Biochemistry, Genetics and Molecular Biology › Cell Biology

Cellular Mechanics and Interactions

Works Count: 55703

Wikipedia

Description

This cluster of papers focuses on the interaction between cells and the extracellular matrix, with an emphasis on cell mechanics, mechanotransduction, and the role of matrix stiffness in regulating stem cell behavior, tissue engineering, and cancer progression.

Keywords

Extracellular Matrix; Cell Mechanics; Mechanotransduction; Stem Cells; Cytoskeleton; Tissue Engineering; Cell Migration; Matrix Stiffness; Biomechanics; Cancer Progression

Transmembrane crosstalk between the extracellular matrix and the cytoskeleton

2001-11-01

Benjamin Geiger , Alexander D. Bershadsky , Roumen Pankov +1 more

Local force and geometry sensing regulate cell functions

2006-02-22

Viola Vogel , Michael P. Sheetz

Cell Migration: A Physically Integrated Molecular Process

1996-02-01

Douglas A. Lauffenburger , Alan F. Horwitz

View PDF Chat

Intermediate filaments as mechanical integrators of cellular space

1980-01-17

Elias Lazarides

Cell locomotion and focal adhesions are regulated by substrate flexibility

1997-12-09

Robert J. Pelham , Yu‐li Wang

Responses of cells to mechanical properties of the adhesion substrate were examined by culturing normal rat kidney epithelial and 3T3 fibroblastic cells on a collagen-coated polyacrylamide substrate that allows the … Responses of cells to mechanical properties of the adhesion substrate were examined by culturing normal rat kidney epithelial and 3T3 fibroblastic cells on a collagen-coated polyacrylamide substrate that allows the flexibility to be varied while maintaining a constant chemical environment. Compared with cells on rigid substrates, those on flexible substrates showed reduced spreading and increased rates of motility or lamellipodial activity. Microinjection of fluorescent vinculin indicated that focal adhesions on flexible substrates were irregularly shaped and highly dynamic whereas those on firm substrates had a normal morphology and were much more stable. Cells on flexible substrates also contained a reduced amount of phosphotyrosine at adhesion sites. Treatment of these cells with phenylarsine oxide, a tyrosine phosphatase inhibitor, induced the formation of normal, stable focal adhesions similar to those on firm substrates. Conversely, treatment of cells on firm substrates with myosin inhibitors 2,3-butanedione monoxime or KT5926 caused the reduction of both vinculin and phosphotyrosine at adhesion sites. These results demonstrate the ability of cells to survey the mechanical properties of their surrounding environment and suggest the possible involvement of both protein tyrosine phosphorylation and myosin-generated cortical forces in this process. Such response to physical parameters likely represents an important mechanism of cellular interaction with the surrounding environment within a complex organism.

View PDF Chat

Environmental sensing through focal adhesions

2008-12-19

Benjamin Geiger , Joachim P. Spatz , Alexander D. Bershadsky

Signaling from Rho to the Actin Cytoskeleton Through Protein Kinases ROCK and LIM-kinase

1999-08-06

Midori Maekawa , Toshimasa Ishizaki , Shuken Boku +7 more

The actin cytoskeleton undergoes extensive remodeling during cell morphogenesis and motility. The small guanosine triphosphatase Rho regulates such remodeling, but the underlying mechanisms of this regulation remain unclear. Cofilin exhibits … The actin cytoskeleton undergoes extensive remodeling during cell morphogenesis and motility. The small guanosine triphosphatase Rho regulates such remodeling, but the underlying mechanisms of this regulation remain unclear. Cofilin exhibits actin-depolymerizing activity that is inhibited as a result of its phosphorylation by LIM-kinase. Cofilin was phosphorylated in N1E-115 neuroblastoma cells during lysophosphatidic acid–induced, Rho-mediated neurite retraction. This phosphorylation was sensitive to Y-27632, a specific inhibitor of the Rho-associated kinase ROCK. ROCK, which is a downstream effector of Rho, did not phosphorylate cofilin directly but phosphorylated LIM-kinase, which in turn was activated to phosphorylate cofilin. Overexpression of LIM-kinase in HeLa cells induced the formation of actin stress fibers in a Y-27632–sensitive manner. These results indicate that phosphorylation of LIM-kinase by ROCK and consequently increased phosphorylation of cofilin by LIM-kinase contribute to Rho-induced reorganization of the actin cytoskeleton.

Visualizing Spatiotemporal Dynamics of Multicellular Cell-Cycle Progression

2008-02-01

Asako Sakaue-Sawano , Hiroshi Kurokawa , Toshifumi Morimura +7 more

View PDF Chat

Phosphorylation and Activation of Myosin by Rho-associated Kinase (Rho-kinase)

1996-08-01

Mutsuki Amano , Masaaki Ito , Kazushi Kimura +5 more

The small GTPase Rho is implicated in physiological functions associated with actin-myosin filaments such as cytokinesis, cell motility, and smooth muscle contraction. We have recently identified and molecularly cloned Rho-associated … The small GTPase Rho is implicated in physiological functions associated with actin-myosin filaments such as cytokinesis, cell motility, and smooth muscle contraction. We have recently identified and molecularly cloned Rho-associated serine/threonine kinase (Rho-kinase), which is activated by GTP·Rho (Matsui, T., Amano, M., Yamamoto, T., Chihara, K., Nakafuku, M., Ito, M., Nakano, T., Okawa, K., Iwamatsu, A., and Kaibuchi, K. (1996) EMBO J. 15, 2208-2216). Here we found that Rho-kinase stoichiometrically phosphorylated myosin light chain (MLC). Peptide mapping and phosphoamino acid analyses revealed that the primary phosphorylation site of MLC by Rho-kinase was Ser-19, which is the site phosphorylated by MLC kinase. Rho-kinase phosphorylated recombinant MLC, whereas it failed to phosphorylate recombinant MLC, which contained Ala substituted for both Thr-18 and Ser-19. We also found that the phosphorylation of MLC by Rho-kinase resulted in the facilitation of the actin activation of myosin ATPase. Thus, it is likely that once Rho is activated, then it can interact with Rho-kinase and activate it. The activated Rho-kinase subsequently phosphorylates MLC. This may partly account for the mechanism by which Rho regulates cytokinesis, cell motility, or smooth muscle contraction. The small GTPase Rho is implicated in physiological functions associated with actin-myosin filaments such as cytokinesis, cell motility, and smooth muscle contraction. We have recently identified and molecularly cloned Rho-associated serine/threonine kinase (Rho-kinase), which is activated by GTP·Rho (Matsui, T., Amano, M., Yamamoto, T., Chihara, K., Nakafuku, M., Ito, M., Nakano, T., Okawa, K., Iwamatsu, A., and Kaibuchi, K. (1996) EMBO J. 15, 2208-2216). Here we found that Rho-kinase stoichiometrically phosphorylated myosin light chain (MLC). Peptide mapping and phosphoamino acid analyses revealed that the primary phosphorylation site of MLC by Rho-kinase was Ser-19, which is the site phosphorylated by MLC kinase. Rho-kinase phosphorylated recombinant MLC, whereas it failed to phosphorylate recombinant MLC, which contained Ala substituted for both Thr-18 and Ser-19. We also found that the phosphorylation of MLC by Rho-kinase resulted in the facilitation of the actin activation of myosin ATPase. Thus, it is likely that once Rho is activated, then it can interact with Rho-kinase and activate it. The activated Rho-kinase subsequently phosphorylates MLC. This may partly account for the mechanism by which Rho regulates cytokinesis, cell motility, or smooth muscle contraction.

View PDF Chat

Extracellular Matrix Degradation and Remodeling in Development and Disease

2011-09-14

Pengfei Lu , Ken Takai , Valerie M. Weaver +1 more

Pengfei Lu1,2, Ken Takai2, Valerie M. Weaver3 and Zena Werb2 Breakthrough Breast Cancer Research Unit, Paterson Institute for Cancer Research and Wellcome Trust Centre for Cell Matrix Research, Faculty of … Pengfei Lu1,2, Ken Takai2, Valerie M. Weaver3 and Zena Werb2 Breakthrough Breast Cancer Research Unit, Paterson Institute for Cancer Research and Wellcome Trust Centre for Cell Matrix Research, Faculty of Life Sciences, University of Manchester, Manchester M20 4BX, United Kingdom Department of Anatomy and Program in Developmental Biology, University of California, San Francisco, California 94143-0452 Department of Surgery and Center for Bioengineering and Tissue Regeneration, University of California, San Francisco, California 94143 Correspondence: zena.werb{at}ucsf.edu

View PDF Chat

The small GTP-binding protein rho regulates the assembly of focal adhesions and actin stress fibers in response to growth factors

1992-08-01

Anne J. Ridley , Alan Hall

Cell Movement Is Guided by the Rigidity of the Substrate

2000-07-01

Chun‐Min Lo , Hong-Bei Wang , Micah Dembo +1 more

View PDF Chat

Rho, Rac, and Cdc42 GTPases regulate the assembly of multimolecular focal complexes associated with actin stress fibers, lamellipodia, and filopodia

1995-04-01

Catherine D. Nobes , Alan Hall

Non-muscle myosin II takes centre stage in cell adhesion and migration

2009-10-23

Miguel Vicente‐Manzanares , Xuefei Ma , Robert Adelstein +1 more

View PDF Chat

Filopodia: molecular architecture and cellular functions

2008-05-09

Pieta K. Mattila , Pekka Lappalainen

View PDF Chat

Mechanotransduction Across the Cell Surface and Through the Cytoskeleton

1993-05-21

Ning Wang , James P. Butler , Donald E. Ingber

Mechanical stresses were applied directly to cell surface receptors with a magnetic twisting device. The extracellular matrix receptor, integrin β 1 , induced focal adhesion formation and supported a force-dependent … Mechanical stresses were applied directly to cell surface receptors with a magnetic twisting device. The extracellular matrix receptor, integrin β 1 , induced focal adhesion formation and supported a force-dependent stiffening response, whereas nonadhesion receptors did not. The cytoskeletal stiffness (ratio of stress to strain) increased in direct proportion to the applied stress and required intact microtubules and intermediate filaments as well as microfilaments. Tensegrity models that incorporate mechanically interdependent struts and strings that reorient globally in response to a localized stress mimicked this response. These results suggest that integrins act as mechanoreceptors and transmit mechanical signals to the cytoskeleton. Mechanotransduction, in turn, may be mediated simultaneously at multiple locations inside the cell through force-induced rearrangements within a tensionally integrated cytoskeleton.

Tissue Cells Feel and Respond to the Stiffness of Their Substrate

2005-11-18

Dennis E. Discher , Paul A. Janmey , Yu-Li Wang

Normal tissue cells are generally not viable when suspended in a fluid and are therefore said to be anchorage dependent. Such cells must adhere to a solid, but a solid … Normal tissue cells are generally not viable when suspended in a fluid and are therefore said to be anchorage dependent. Such cells must adhere to a solid, but a solid can be as rigid as glass or softer than a baby's skin. The behavior of some cells on soft materials is characteristic of important phenotypes; for example, cell growth on soft agar gels is used to identify cancer cells. However, an understanding of how tissue cells-including fibroblasts, myocytes, neurons, and other cell types-sense matrix stiffness is just emerging with quantitative studies of cells adhering to gels (or to other cells) with which elasticity can be tuned to approximate that of tissues. Key roles in molecular pathways are played by adhesion complexes and the actinmyosin cytoskeleton, whose contractile forces are transmitted through transcellular structures. The feedback of local matrix stiffness on cell state likely has important implications for development, differentiation, disease, and regeneration.

View PDF Chat

Geometric Control of Cell Life and Death

1997-05-30

Christopher S. Chen , Milan Mrksich , Sui Huang +2 more

Human and bovine capillary endothelial cells were switched from growth to apoptosis by using micropatterned substrates that contained extracellular matrix-coated adhesive islands of decreasing size to progressively restrict cell extension. … Human and bovine capillary endothelial cells were switched from growth to apoptosis by using micropatterned substrates that contained extracellular matrix-coated adhesive islands of decreasing size to progressively restrict cell extension. Cell spreading also was varied while maintaining the total cell-matrix contact area constant by changing the spacing between multiple focal adhesion-sized islands. Cell shape was found to govern whether individual cells grow or die, regardless of the type of matrix protein or antibody to integrin used to mediate adhesion. Local geometric control of cell growth and viability may therefore represent a fundamental mechanism for developmental regulation within the tissue microenvironment.

Cellular mechanotransduction: putting all the pieces together again

2006-05-01

Donald E. Ingber

Analysis of cellular mechanotransduction, the mechanism by which cells convert mechanical signals into biochemical responses, has focused on identification of critical mechanosensitive molecules and cellular components. Stretch-activated ion channels, caveolae, … Analysis of cellular mechanotransduction, the mechanism by which cells convert mechanical signals into biochemical responses, has focused on identification of critical mechanosensitive molecules and cellular components. Stretch-activated ion channels, caveolae, integrins, cadherins, growth factor receptors, myosin motors, cytoskeletal filaments, nuclei, extracellular matrix, and numerous other structures and signaling molecules have all been shown to contribute to the mechanotransduction response. However, little is known about how these different molecules function within the structural context of living cells, tissues, and organs to produce the orchestrated cellular behaviors required for mechanosensation, embryogenesis, and physiological control. Recent work from a wide range of fields reveals that organ, tissue, and cell anatomy are as important for mechanotransduction as individual mechanosensitive proteins and that our bodies use structural hierarchies (systems within systems) composed of interconnected networks that span from the macroscale to the nanoscale in order to focus stresses on specific mechanotransducer molecules. The presence of isometric tension (prestress) at all levels of these multiscale networks ensures that various molecular scale mechanochemical transduction mechanisms proceed simultaneously and produce a concerted response. Future research in this area will therefore require analysis, understanding, and modeling of tensionally integrated (tensegrity) systems of mechanochemical control.

Mechanotransduction at a distance: mechanically coupling the extracellular matrix with the nucleus

2008-12-19

Ning Wang , Jessica Tytell , Donald E. Ingber

Actin-Based Cell Motility and Cell Locomotion

1996-02-01

Timothy J. Mitchison , Louise P. Cramer

View PDF Chat

Cell adhesion: integrating cytoskeletal dynamics and cellular tension

2010-08-23

J. Thomas Parsons , Alan Rick Horwitz , Martin A. Schwartz

Demonstration of mechanical connections between integrins, cytoskeletal filaments, and nucleoplasm that stabilize nuclear structure

1997-02-04

Andrew J. Maniotis , Christopher S. Chen , Donald E. Ingber

We report here that living cells and nuclei are hard-wired such that a mechanical tug on cell surface receptors can immediately change the organization of molecular assemblies in the cytoplasm … We report here that living cells and nuclei are hard-wired such that a mechanical tug on cell surface receptors can immediately change the organization of molecular assemblies in the cytoplasm and nucleus. When integrins were pulled by micromanipulating bound microbeads or micropipettes, cytoskeletal filaments reoriented, nuclei distorted, and nucleoli redistributed along the axis of the applied tension field. These effects were specific for integrins, independent of cortical membrane distortion, and were mediated by direct linkages between the cytoskeleton and nucleus. Actin microfilaments mediated force transfer to the nucleus at low strain; however, tearing of the actin gel resulted with greater distortion. In contrast, intermediate filaments effectively mediated force transfer to the nucleus under both conditions. These filament systems also acted as molecular guy wires to mechanically stiffen the nucleus and anchor it in place, whereas microtubules acted to hold open the intermediate filament lattice and to stabilize the nucleus against lateral compression. Molecular connections between integrins, cytoskeletal filaments, and nuclear scaffolds may therefore provide a discrete path for mechanical signal transfer through cells as well as a mechanism for producing integrated changes in cell and nuclear structure in response to changes in extracellular matrix adhesivity or mechanics.

View PDF Chat

A tense situation: forcing tumour progression

2009-01-23

Darci T. Butcher , Tamara Alliston , Valerie M. Weaver

Nanomechanical analysis of cells from cancer patients

2007-12-01

S. E. Cross , Yusheng Jin , Jianyu Rao +1 more

The small GTP-binding protein rac regulates growth factor-induced membrane ruffling

1992-08-01

Anne J. Ridley , Hugh F. Paterson , Caroline L. Johnston +2 more

Rho GTPases and the Actin Cytoskeleton

1998-01-23

Alan Hall

The actin cytoskeleton mediates a variety of essential biological functions in all eukaryotic cells. In addition to providing a structural framework around which cell shape and polarity are defined, its … The actin cytoskeleton mediates a variety of essential biological functions in all eukaryotic cells. In addition to providing a structural framework around which cell shape and polarity are defined, its dynamic properties provide the driving force for cells to move and to divide. Understanding the biochemical mechanisms that control the organization of actin is thus a major goal of contemporary cell biology, with implications for health and disease. Members of the Rho family of small guanosine triphosphatases have emerged as key regulators of the actin cytoskeleton, and furthermore, through their interaction with multiple target proteins, they ensure coordinated control of other cellular activities such as gene transcription and adhesion.

Tensional homeostasis and the malignant phenotype

2005-09-01

Matthew J. Paszek , Nastaran Zahir , Kandice R. Johnson +7 more

Geometric cues for directing the differentiation of mesenchymal stem cells

2010-03-01

K. Kilian , Branimir Bugarija , Bruce T. Lahn +1 more

Significant efforts have been directed to understanding the factors that influence the lineage commitment of stem cells. This paper demonstrates that cell shape, independent of soluble factors, has a strong … Significant efforts have been directed to understanding the factors that influence the lineage commitment of stem cells. This paper demonstrates that cell shape, independent of soluble factors, has a strong influence on the differentiation of human mesenchymal stem cells (MSCs) from bone marrow. When exposed to competing soluble differentiation signals, cells cultured in rectangles with increasing aspect ratio and in shapes with pentagonal symmetry but with different subcellular curvature—and with each occupying the same area—display different adipogenesis and osteogenesis profiles. The results reveal that geometric features that increase actomyosin contractility promote osteogenesis and are consistent with in vivo characteristics of the microenvironment of the differentiated cells. Cytoskeletal-disrupting pharmacological agents modulate shape-based trends in lineage commitment verifying the critical role of focal adhesion and myosin-generated contractility during differentiation. Microarray analysis and pathway inhibition studies suggest that contractile cells promote osteogenesis by enhancing c-Jun N-terminal kinase (JNK) and extracellular related kinase (ERK1/2) activation in conjunction with elevated wingless-type (Wnt) signaling. Taken together, this work points to the role that geometric shape cues can play in orchestrating the mechanochemical signals and paracrine/autocrine factors that can direct MSCs to appropriate fates.

View PDF Chat

In vitro scratch assay: a convenient and inexpensive method for analysis of cell migration in vitro

2007-02-01

Chun-Chi Liang , Ann Y. Park , Jun‐Lin Guan

View PDF Chat

Mechanotransduction and extracellular matrix homeostasis

2014-10-22

Jay D. Humphrey , Eric R. Dufresne , Martin A. Schwartz

View PDF Chat

Cells lying on a bed of microneedles: An approach to isolate mechanical force

2003-01-27

John L. Tan , Joe Tien , Dana M. Pirone +3 more

We describe an approach to manipulate and measure mechanical interactions between cells and their underlying substrates by using microfabricated arrays of elastomeric, microneedle-like posts. By controlling the geometry of the … We describe an approach to manipulate and measure mechanical interactions between cells and their underlying substrates by using microfabricated arrays of elastomeric, microneedle-like posts. By controlling the geometry of the posts, we varied the compliance of the substrate while holding other surface properties constant. Cells attached to, spread across, and deflected multiple posts. The deflections of the posts occurred independently of neighboring posts and, therefore, directly reported the subcellular distribution of traction forces. We report two classes of force-supporting adhesions that exhibit distinct force–size relationships. Force increased with size of adhesions for adhesions larger than 1 μm 2 , whereas no such correlation existed for smaller adhesions. By controlling cell adhesion on these micromechanical sensors, we showed that cell morphology regulates the magnitude of traction force generated by cells. Cells that were prevented from spreading and flattening against the substrate did not contract in response to stimulation by serum or lysophosphatidic acid, whereas spread cells did. Contractility in the unspread cells was rescued by expression of constitutively active RhoA. Together, these findings demonstrate a coordination of biochemical and mechanical signals to regulate cell adhesion and mechanics, and they introduce the use of arrays of mechanically isolated sensors to manipulate and measure the mechanical interactions of cells.

View PDF Chat

Force and focal adhesion assembly: a close relationship studied using elastic micropatterned substrates

2001-04-06

Nathalie Q. Balaban , Ulrich S. Schwarz , Daniel Riveline +7 more

TENSEGRITY: THE ARCHITECTURAL BASIS OF CELLULAR MECHANOTRANSDUCTION

1997-10-01

Donald E. Ingber

▪ Abstract Physical forces of gravity, hemodynamic stresses, and movement play a critical role in tissue development. Yet, little is known about how cells convert these mechanical signals into a … ▪ Abstract Physical forces of gravity, hemodynamic stresses, and movement play a critical role in tissue development. Yet, little is known about how cells convert these mechanical signals into a chemical response. This review attempts to place the potential molecular mediators of mechanotransduction (e.g. stretch-sensitive ion channels, signaling mollecules, cytoskeleton, integrins) within the context of the structural complexity of living cells. The model presented relies on recent experimental findings, which suggests that cells use tensegrity architecture for their organization. Tensegrity predicts that cells are hard-wired to respond immediately to mechanical stresses transmitted over cell surface receptors that physically couple the cytoskeleton to extracellular matrix (e.g. integrins) or to other cells (cadherins, selectins, CAMs). Many signal transducing molecules that are activated by cell binding to growth factors and extracellular matrix associate with cytoskeletal scaffolds within focal adhesion complexes. Mechanical signals, therefore, may be integrated with other environmental signals and transduced into a biochemical response through force-dependent changes in scaffold geometry or molecular mechanics. Tensegrity also provides a mechanism to focus mechanical energy on molecular transducers and to orchestrate and tune the cellular response.

Cellular Motility Driven by Assembly and Disassembly of Actin Filaments

2003-02-01

Thomas D. Pollard , Gary G. Borisy

Nonlinear elasticity in biological gels

2005-05-01

Cornelis Storm , Jennifer J. Pastore , F. C. MacKintosh +2 more

View PDF Chat

Bone “mass” and the “mechanostat”: A proposal

1987-09-01

Harold M. Frost

Abstract The observed fit of bone mass to a healthy animal's typical mechanical usage indicates some mechanism or mechanisms monitor that usage and control the three longitudinal growth, bone modeling, … Abstract The observed fit of bone mass to a healthy animal's typical mechanical usage indicates some mechanism or mechanisms monitor that usage and control the three longitudinal growth, bone modeling, and BMU‐based remodeling activities that directly determine bone mass. That mechanism could be named a mechanostat. Accumulated evidence suggests it includes the bone itself, plus mechanisms that transform its mechanical usage into appropriate signals, plus other mechanisms that detect those signals and then direct the above three biologic activities. In vivo studies have shown that bone strains in or above the 1500–3000 microstrain range cause bone modelling to increase cortical bone mass, while strains below the 100–300 microstrain range release BMU‐based remodeling which then removes existing cortical‐endosteal and trabecular bone. That arrangement provides a dual system in which bone modeling would adapt bone mass to gross overloading, while BMU‐based remodeling would adapt bone mass to gross underloading, and the above strain ranges would be the approximate “setpoints” of those responses. The anatomical distribution of those mechanical usage effects are well known. If circulating agents or disease changed the effective setpoints of those responses their bone mass effects should copy the anatomical distribution of the mechanical usage effects. That seems to be the case for many agents and diseases, and several examples are discussed, including postmenopausal osteoporosis, fluoride effects, bone loss in orbit, and osteogenesis imperfecta. The mechanostat proposal is a seminal idea which fits diverse evidence but it requires critique and experimental study.

Matrix Elasticity Directs Stem Cell Lineage Specification

2006-08-01

Adam J. Engler , Shamik Sen , H. Lee Sweeney +1 more

View PDF Chat

Control of Stem Cell Fate by Physical Interactions with the Extracellular Matrix

2009-07-01

Farshid Guilak , Daniel M. Cohen , Bradley T. Estes +3 more

View PDF Chat

Cancer Invasion and the Microenvironment: Plasticity and Reciprocity

2011-11-01

Peter Friedl , Stephanie Alexander

Cell Shape, Cytoskeletal Tension, and RhoA Regulate Stem Cell Lineage Commitment

2004-04-01

Rowena McBeath , Dana M. Pirone , Celeste M. Nelson +2 more

View PDF Chat

Collective cell migration in morphogenesis, regeneration and cancer

2009-06-23

Peter Friedl , Darren Gilmour

Effects of substrate stiffness on cell morphology, cytoskeletal structure, and adhesion

2004-01-01

Tony Yeung , Penelope C. Georges , Lisa A. Flanagan +7 more

The morphology and cytoskeletal structure of fibroblasts, endothelial cells, and neutrophils are documented for cells cultured on surfaces with stiffness ranging from 2 to 55,000 Pa that have been laminated … The morphology and cytoskeletal structure of fibroblasts, endothelial cells, and neutrophils are documented for cells cultured on surfaces with stiffness ranging from 2 to 55,000 Pa that have been laminated with fibronectin or collagen as adhesive ligand. When grown in sparse culture with no cell-cell contacts, fibroblasts and endothelial cells show an abrupt change in spread area that occurs at a stiffness range around 3,000 Pa. No actin stress fibers are seen in fibroblasts on soft surfaces, and the appearance of stress fibers is abrupt and complete at a stiffness range coincident with that at which they spread. Upregulation of α5 integrin also occurs in the same stiffness range, but exogenous expression of α5 integrin is not sufficient to cause cell spreading on soft surfaces. Neutrophils, in contrast, show no dependence of either resting shape or ability to spread after activation when cultured on surfaces as soft as 2 Pa compared to glass. The shape and cytoskeletal differences evident in single cells on soft compared to hard substrates are eliminated when fibroblasts or endothelial cells make cell-cell contact. These results support the hypothesis that mechanical factors impact different cell types in fundamentally different ways, and can trigger specific changes similar to those stimulated by soluble ligands. Cell Motil. Cytoskeleton 60:24–34, 2005. © 2004 Wiley-Liss, Inc.

Rho-stimulated contractility drives the formation of stress fibers and focal adhesions.

1996-06-15

Magdalena Chrzanowska‐Wodnicka , Keith Burridge

Activated rhoA, a ras-related GTP-binding protein, stimulates the appearance of stress fibers, focal adhesions, and tyrosine phosphorylation in quiescent cells (Ridley, A.J., and A. Hall, 1992. Cell. 70:389-399). The pathway … Activated rhoA, a ras-related GTP-binding protein, stimulates the appearance of stress fibers, focal adhesions, and tyrosine phosphorylation in quiescent cells (Ridley, A.J., and A. Hall, 1992. Cell. 70:389-399). The pathway by which rho triggers these events has not been elucidated. Many of the agents that activate rho (e.g., vasopressin, endothelin, lysophosphatidic acid) stimulate the contractility of smooth muscle and other cells. We have investigated whether rho's induction of stress fibers, focal adhesions, and tyrosine phosphorylation is the result of its stimulation of contractility. We demonstrate that stimulation of fibroblasts with lysophosphatidic acid, which activates rho, induces myosin light chain phosphorylation. This precedes the formation of stress fibers and focal adhesions and is accompanied by increased contractility. Inhibition of contractility by several different mechanisms leads to inhibition of rho-induced stress fibers, focal adhesions, and tyrosine phosphorylation. In addition, when contractility is inhibited, integrins disperse from focal adhesions as stress fibers and focal adhesions disassemble. Conversely, upon stimulation of contractility, diffusely distributed integrins are aggregated into focal adhesions. These results suggest that activated rho stimulates contractility, driving the formation of stress fibers and focal adhesions and elevating tyrosine phosphorylation. A model is proposed to account for how contractility could promote these events.

View PDF Chat

Actin, a Central Player in Cell Shape and Movement

2009-11-27

Thomas D. Pollard , John A. Cooper

The protein actin forms filaments that provide cells with mechanical support and driving forces for movement. Actin contributes to biological processes such as sensing environmental forces, internalizing membrane vesicles, moving … The protein actin forms filaments that provide cells with mechanical support and driving forces for movement. Actin contributes to biological processes such as sensing environmental forces, internalizing membrane vesicles, moving over surfaces, and dividing the cell in two. These cellular activities are complex; they depend on interactions of actin monomers and filaments with numerous other proteins. Here, we present a summary of the key questions in the field and suggest how those questions might be answered. Understanding actin-based biological phenomena will depend on identifying the participating molecules and defining their molecular mechanisms. Comparisons of quantitative measurements of reactions in live cells with computer simulations of mathematical models will also help generate meaningful insights.

View PDF Chat

Cell mechanics and the cytoskeleton

2010-01-01

Daniel A. Fletcher , R. Dyche Mullins

View PDF Chat

Myotubes differentiate optimally on substrates with tissue-like stiffness

2004-09-13

Adam J. Engler , Maureen A. Griffin , Shamik Sen +3 more

Contractile myocytes provide a test of the hypothesis that cells sense their mechanical as well as molecular microenvironment, altering expression, organization, and/or morphology accordingly. Here, myoblasts were cultured on collagen … Contractile myocytes provide a test of the hypothesis that cells sense their mechanical as well as molecular microenvironment, altering expression, organization, and/or morphology accordingly. Here, myoblasts were cultured on collagen strips attached to glass or polymer gels of varied elasticity. Subsequent fusion into myotubes occurs independent of substrate flexibility. However, myosin/actin striations emerge later only on gels with stiffness typical of normal muscle (passive Young's modulus, E ∼12 kPa). On glass and much softer or stiffer gels, including gels emulating stiff dystrophic muscle, cells do not striate. In addition, myotubes grown on top of a compliant bottom layer of glass-attached myotubes (but not softer fibroblasts) will striate, whereas the bottom cells will only assemble stress fibers and vinculin-rich adhesions. Unlike sarcomere formation, adhesion strength increases monotonically versus substrate stiffness with strongest adhesion on glass. These findings have major implications for in vivo introduction of stem cells into diseased or damaged striated muscle of altered mechanical composition.

View PDF Chat

Cell Adhesion: The Molecular Basis of Tissue Architecture and Morphogenesis

1996-02-01

Barry M. Gumbiner

View PDF Chat

Hydrogels with tunable stress relaxation regulate stem cell fate and activity

2015-11-30

Ovijit Chaudhuri , Luo Gu , Darinka D. Klumpers +7 more

View PDF Chat

Effects of extracellular matrix viscoelasticity on cellular behaviour

2020-08-26

Ovijit Chaudhuri , Justin J. Cooper‐White , Paul A. Janmey +2 more

Confinement Suppresses Mechanical Force‐Mediated Cancer Cell Apoptosis

2025-06-25

Kumari Alka , Akshay Kumar , Xu Gao +4 more | Small

Abstract During the invasion, cancer cells migrate through ‘3D channel‐like tracks’ present in the tissues' interstitial extracellular matrix (ECM). Cancer cell migration through these 3D confined channels leads to confinement‐induced … Abstract During the invasion, cancer cells migrate through ‘3D channel‐like tracks’ present in the tissues' interstitial extracellular matrix (ECM). Cancer cell migration through these 3D confined channels leads to confinement‐induced cell deformation. Emerging reports show that cancer cells are susceptible to mechanical stretch/ultrasound (US)‐mediated mechanical forces and undergo calcium‐dependent apoptosis (mechanoptosis) under conditions that promote normal cell growth. Surprisingly, we find that confinement‐induced cell deformation suppresses mechanoptosis. Studies done using microchannel platforms and tumor spheroid models show that a low level of apoptosis is observed in confined cells. Further, apoptosis level is found to increase with a decrease in the degree of confinement. The absence of mature focal adhesions (FAs), low myosin IIA contractility, and diffuse mechanosensitive Piezo1 channels are responsible for a low level of apoptosis in confined cells. Thus, these findings suggest that confined cells, due to the absence of mature FAs, could not sense and transduce the mechanical forces and generate enough myosin IIA contractility required to initiate apoptosis. The combined action of US and activators of myosin contractility can be used to target invading cancer cells.

Healing regimes for microscopic wounds in the vertex model of cell tissues

2025-06-24

NULL AUTHOR_ID | Physical review. E

Chirality Hydroxyapatite Gradient Scaffold Drives Osteochondral Regeneration via YAP/TAZ‐Mediated Mechanotransduction

2025-06-23

Y. Liu , Chao Zhou , Xiaoyin Zhang +1 more | Advanced Healthcare Materials

Abstract Cartilage lesions are commonly age‐related disorders capable of affecting regular joint movement until they extend to underlying subchondral bones, resulting in osteochondral defects. Gradient scaffold as an effective solution … Abstract Cartilage lesions are commonly age‐related disorders capable of affecting regular joint movement until they extend to underlying subchondral bones, resulting in osteochondral defects. Gradient scaffold as an effective solution for healing has drawn more attention, however, current studies only consider the biomimetic design of gradient structures, but ignore the chiral microenvironment remodeling in native tissues. Here, highly biomimetic chiral gradient scaffolds are designed and prepared by using lyophilization bonding among layers for liquid chitosan (CS) substrate incorporating stratified‐distributed chiral hydroxyapatite (HAP). These biomimetic scaffolds facilitate both bone marrow stromal cells (BMSCs) adhesion and differentiation and chondrocytes dedifferentiation inhibition in vitro tests. Furthermore, in vivo assays unveil the presence of the levorotatory (L) in them markedly strengthened the performance of osteochondral regeneration, in stark contrast to the dextrorotatory (D). The subsequent investigation into the repair‐promoting mechanism prove L enhanced nuclear transport of yes‐associated protein (YAP) by modulating stress fiber distribution in BMSCs, which is instrumental in up‐regulation of osteogenesis‐related biomarkers. Meanwhile, detected up‐regulation of chondrogenesis biomarkers suggest enhanced bone repair provided structural support for neochondrogenesis and averted collapse. These results indicate novel bioactive scaffolds are beneficial for achieving effective repair in the context of osteochondral injury situation.

E-cadherin negatively regulates hESCs endodermal differentiation under varied substrate stiffnesses

2025-06-23

Fan Zhang , Lu Zheng , Yi Wu +4 more | Cellular and Molecular Life Sciences

Intercellular adhesion is crucial in regulating stemness maintenance and differentiation initiation of embryonic stem cells (ESCs), which is also cooperated with extracellular mechanical microenvironment. Here an in vitro model was … Intercellular adhesion is crucial in regulating stemness maintenance and differentiation initiation of embryonic stem cells (ESCs), which is also cooperated with extracellular mechanical microenvironment. Here an in vitro model was used to elucidate the effects of E-cadherin complexes on definitive endoderm (DE)-directed differentiation of hESCs (H1 cells), when the cells were seeded on polyacrylamide hydrogels with varied stiffnesses. Results indicated that stiff substrate increased the proportion of H1 cells differentiating into DE cells and intercellular E-cadherin expression was reduced with progressive stages at same stiffness, presenting a negative correlation of E-cadherin expression with differentiating progress or substrate stiffness. Blocking E-cadherin enhanced the productivity of differentiated cells and promoted the disassembly of intercellular adhesions by translocating YAP into nuclei, which was positively correlated with GATA6 and CXCR4 expressions in a stiffness-dependent manner. This work provided an insight into understanding the roles of E-cadherin-related intercellular adhesion and substrate stiffness in DE-directed differentiation of hESCs.

Consolidation of cell-ECM adhesion through direct talin-mediated actin linkage is essential for mouse embryonic morphogenesis

2025-06-21

Wenjun Deng , Rosalyn Leigh Carr , Rajeev Kaul +4 more | Communications Biology

During animal development, cell-ECM adhesion mediated by integrins is required for the assembly and maintenance of tissues and organs. It can either be transient or stable and requires linking integrins … During animal development, cell-ECM adhesion mediated by integrins is required for the assembly and maintenance of tissues and organs. It can either be transient or stable and requires linking integrins to the cytoskeleton. Talin can link integrins to actin either directly through its actin-binding sites (ABSs) or indirectly by recruiting downstream actin-binding molecules. In Drosophila, talin's ABS3 domain is essential for biological functions, but its role remains unknown in mammalian systems. Here, we investigate the role of direct talin-mediated actin linkage in mammals by generating a mouse model containing point mutations in talin's ABS3 domain. We find that mutant mice exhibit early developmental defects and die midway through embryogenesis. Primary mouse embryonic fibroblasts generated from mutants form prominent focal adhesions but show defective consolidation and maturation. Adhesion dynamics, cell spreading, actin dynamics and organization, and traction force generation are also impacted in mutants, which affect processes such as cell migration that impinge on multiple events during early mouse embryogenesis. Overall, our work provides key mechanistic insights into how direct coupling of ECM to actin through talin has specific and critical roles in controlling adhesion dynamics required for early mammalian development.

A balance between nucleating and elongating actin filaments controls deformation of protein condensates

2025-06-21

Caleb Walker , Daniel Mansour , Unyime M. Effiong +7 more | bioRxiv (Cold Spring Harbor Laboratory)

Protein condensates use multivalent binding and surface tension to assemble actin filaments into diverse architectures, reminiscent of filopodia and stress fibers. During this process, nucleation of new filaments and elongation … Protein condensates use multivalent binding and surface tension to assemble actin filaments into diverse architectures, reminiscent of filopodia and stress fibers. During this process, nucleation of new filaments and elongation of existing filaments inherently compete for a shared pool of actin monomers. Here we show that a balance between these competing processes is required to deform condensates of VASP, an actin binding protein, into structures with high aspect ratios. Addition of magnesium, which promotes filament nucleation, helped actin to deform condensates into high aspect ratio structures. In contrast, addition of profilin, which inhibits filament nucleation, allowing existing filaments to elongate, caused actin to assemble into ring-like bundles that failed to substantially increase condensate aspect ratio. Computational modeling helped to explain these results by predicting that a group of short linear filaments, which can apply asymmetric pressure to the condensate boundary, is needed to increase condensate aspect ratio. In contrast, a small number of long filaments with the same total actin content should fail to overcome the droplet surface tension, forming a ring-like bundle. To test these predictions, we introduced gelsolin, which severed log filaments within rings, creating new barbed ends. The resulting set of shorter filaments regained the ability to deform condensates into high aspect ratio structures. Collectively, these results suggest that a balance of actin filament nucleation and elongation is required to deform protein condensates. More broadly, these findings illustrate how protein condensates can balance multiple kinetic processes to direct the assembly of diverse cytoskeletal architectures.

Tuning collagen nonlinear mechanics with interpenetrating networks drives adaptive cellular phenotypes in three dimensions

2025-06-20

Marco A. Enríquez Martínez , Zhao Wang , Yanina D. Álvarez +7 more | Science Advances

In living tissues, collagen networks rarely exist alone because they are embedded within other biological matrices. When combined, collagen networks rigidify via synergistic mechanical interactions and stiffen only with higher … In living tissues, collagen networks rarely exist alone because they are embedded within other biological matrices. When combined, collagen networks rigidify via synergistic mechanical interactions and stiffen only with higher mechanical loads. However, how cells respond to the nonlinear elasticity of collagen in hybrid networks remains largely unknown. Here, we demonstrate that when collagen rigidifies by the interpenetration of a second polymer, the amount of force that initially stiffens the network (onset of stiffening, σ c ) increases and is sufficient to stimulate an increase in intracellular tension. We investigated this effect by precisely controlling the nonlinear elasticity of collagen with the synthetic semiflexible polymer, polyisocyanopeptides. We find that small increases in σ c induce a biphasic response in cell-matrix interactions, influencing how cells migrate, proliferate, and generate contractile force. Our results suggest that cells adaptively respond to changes in the nonlinear mechanics of collagen, which may be a mechanistic behavior used during tissue homeostasis or when collagen rigidifies during pathological conditions.

Fabrication of microcompartments with controlled size and shape for encapsulating active matter

2025-06-20

Benoît Vianay , Christophe Guérin , Laurène Gressin +4 more | Frontiers in Cell and Developmental Biology

In all living systems, the cytoplasm is separated from the external environment by membranes. This confinement imposes spatial constraints on the self-organization of internal components, filaments and organelles. While reconstituted … In all living systems, the cytoplasm is separated from the external environment by membranes. This confinement imposes spatial constraints on the self-organization of internal components, filaments and organelles. While reconstituted systems are instrumental for understanding fundamental biological principles, traditional experiments often utilize volumes vastly larger than actual cells. In recent studies, water-in-oil droplets or giant unilamellar vesicles have been widely used to impose confinement. However, these compartments present imaging challenges and make precise protein content control difficult. To address these limitations, we have developed versatile microwells that are straightforward to implement, compatible with different types of imaging and suitable for long-term experiments. These microwells are compatible with several surface treatments and a wide range of experimental techniques making them a powerful tool for answering key questions in cell biology. We present here a detailed protocol of the fabrication of the microwells as well as characterization of the method to ensure quality throughout the manufacturing process. These microwells support various cytoskeleton-based processes including actin polymerization, dynamic steady-state actin networks, and composite actin-microtubule networks. More broadly, they can be used to encapsulate and study over time any kind of active matter.

Intercellular flow dominates the poroelasticity of multicellular tissues

2025-06-20

Fan Liu , Bo Gao , L. Lei +3 more | Nature Physics

An Insight into Cancer Cells and Disease Progression Through the Lens of Mathematical Modeling

2025-06-20

Polychronis Michalakis , Dimitra Vasilaki , Ali Abdallah +6 more | Current Issues in Molecular Biology

During cancer initiation, normal cells acquire mutations disrupting standard cellular processes, activating oncogenes and inactivating tumor suppressor genes, acquiring the well-described hallmarks of cancer on the path to malignancy. This … During cancer initiation, normal cells acquire mutations disrupting standard cellular processes, activating oncogenes and inactivating tumor suppressor genes, acquiring the well-described hallmarks of cancer on the path to malignancy. This process is influenced by a combination of physiological and metabolic pathways, as well as environmental cues, and leads to abnormal cell cycle, increased cell motility, and invasive characteristics. Cancer cell organelles also present some distinct differences from those of normal cells. Cancer progression requires certain tumorigenic biochemical pathways to be activated. However, mechanical cues are also important, as they have an effect on cell differentiation and fate. A continuous biochemical–biomechanical interaction exists, which affects the mechanical properties of the cells, as well as their behavior. This review aims to focus on the mathematical relationships governing cancer mechanobiology and examine how the altered mechanical properties of a cancer cell may affect malignant progression.

ECM Mechanics Control Jamming-to-Unjamming Transition of Cancer Cells

2025-06-20

Claudia Tanja Mierke | Cells

Cancer metastasis constitutes a multifactorial phenomenon that continues to confound therapeutic strategies. The biochemical signals governing motile phenotypes have been extensively characterized, but mechanobiological interactions have only recently been integrated … Cancer metastasis constitutes a multifactorial phenomenon that continues to confound therapeutic strategies. The biochemical signals governing motile phenotypes have been extensively characterized, but mechanobiological interactions have only recently been integrated into cancer cell motility models and remain less well elucidated. The identification of the biochemically and mechanically controlled epithelial–mesenchymal transition (EMT) of cancer cells, which occurs either completely or partially, has led to a major breakthrough and a universal phenomenon in cancers. In addition, a relatively new theory based on mechanobiological aspects called “jamming-to-unjamming transition” is being proposed to explain the transition of cancer cells to an invasive phenotype. The latter transition may help to better understand the different types of 3D migration and invasion of cancer cells. Similarly to EMT, the transition from jamming to unjamming seems to be controlled by molecular and physical factors, including cell mechanics and mechanical cues from the extracellular matrix (ECM) of the tumor microenvironment (TME). It is challenging to grasp the distinctions between the transition from jamming to unjamming and EMT, as they appear to be the same at first glance. However, upon closer examination, the two transitions are quite separate. Moreover, it is still unclear whether both transitions may act synergistically. This review highlights the most important breakthroughs in the transition from jamming to unjamming, with a focus on mechanobiology and extracellular environmental aspects, and it compares them with those of EMT. In addition, the impact of the TME, such as ECM scaffold and cancer-associated fibroblasts (CAFs) on the jamming-to-unjamming transition is discussed. Finally, the research frontiers and future directions in the field of mechanobiological research in cancer metastasis are outlined.

Eco‐Fabricated Nanowave‐Textured Implants Drive Microtubule‐Assisted Nuclear Mechanotransduction and Chromatin Modification: Biophysical Priming for Osteogenesis and Bone Regeneration

2025-06-19

Bosu Jeong , Ji‐Young Yoon , Junyong Ahn +7 more | Advanced Functional Materials

Abstract The biophysical cues from implantable materials, specifically nanotopography, play a pivotal role in directing cellular lineage specification, thereby accelerating tissue healing and regeneration. Despite the recognized impact of these … Abstract The biophysical cues from implantable materials, specifically nanotopography, play a pivotal role in directing cellular lineage specification, thereby accelerating tissue healing and regeneration. Despite the recognized impact of these cues, the mechanisms governing mechano‐activated signaling pathways between the cytoskeletal and nuclear domains remain largely unexplored. Here, the processes underlying the enhanced osteogenesis of mesenchymal stem cells (MSCs) driven by nanotextured implants are elucidated, focusing on alterations in cytoskeletal mechanosensitive molecules and nuclear chromatin structures. Using green‐processed femtosecond laser fabrication, an implant platform featuring nanowave textures is engineered, inducing cellular alignment with oriented cytoskeletons and consequential changes in nuclear shape. Notably, activated and aligned microtubules alongside the nucleus play a key role in shaping nuclear morphology. The nanowave textures induce significant modifications in chromatin structure, characterized by increased histone acetylation, implying a mechano‐priming of MSCs for osteogenesis. Mechanically‐primed MSCs exhibit enhanced osteogenic transcriptional responsiveness to biochemical cues, with mechanosensitive YAP co‐signaling with the RUNX2, facilitated by an opened chromatin structure. In vivo experiments in a rabbit tibia reveal that nanowave‐textured implants promote osteogenesis and bone formation. This study underscores the ability of nanowave‐textured cues to transmit mechano‐signals across the cytoskeletal‐to‐nuclear space in MSCs, leading to stimulated osteogenesis.

Cytokinesis in Suspension: A Distinctive Trait of Mesenchymal Stem Cells

2025-06-19

Bhavna Rani , Hong Qian , Staffan Johansson | Cells

Mesenchymal stem cells (MSCs) have a broad clinical potential, but their selection and expansion on plastic cause unknown purity and phenotypic alterations, reducing therapy efficiency. Furthermore, their behavior in non-adherent … Mesenchymal stem cells (MSCs) have a broad clinical potential, but their selection and expansion on plastic cause unknown purity and phenotypic alterations, reducing therapy efficiency. Furthermore, their behavior in non-adherent conditions during systemic transplantation remains poorly understood. The sphere formation from single cells is commonly used to assess stemness, but MSCs lack this ability, raising questions about their anchorage dependence for proliferation. We investigated whether bone marrow-derived MSCs can complete cytokinesis in non-adherent environments. Primary human and mouse bone marrow-derived MSCs were synchronized in early mitosis using nocodazole and were cultured on soft, rigid, or non-adherent surfaces. Both human and mouse MSCs displayed an ALIX (abscission licensor) recruitment to the midbody 40-90 min post-nocodazole release, regardless of the substrate adherence. Cells maintained for 4hr in the suspension remained viable, and daughter cells rapidly migrated apart upon the re-adhesion to fibronectin-coated surfaces, demonstrating cytokinesis completion in suspension. These findings distinguish MSCs from fibroblasts (which require adhesion for division), provide a more general stemness feature, and suggest that adhesion-independent cytokinesis is a trait relevant to the post-transplantation survival and tissue homing. This property may offer strategies to expand MSCs with an improved purity and functionality and to enhance engraftment by leveraging cell cycle manipulation to promote an early extracellular matrix deposition at target sites.

Motor-driven modulation of actin network mechanics across linear and nonlinear regimes

2025-06-18

Bernard Nkusi , Morgan L. Thomas , Bekele Gurmessa | bioRxiv (Cold Spring Harbor Laboratory)

Cytoskeletal networks enable cells to dynamically regulate their mechanical properties in response to internal forces and external cues. Here, we investigate how motor activity influences the structure and mechanics of … Cytoskeletal networks enable cells to dynamically regulate their mechanical properties in response to internal forces and external cues. Here, we investigate how motor activity influences the structure and mechanics of actomyosin networks reconstituted in vitro from filamentous actin, myosin II minifilaments, and transient α -actinin cross-linkers. By varying the myosin-to-actin molar ratio ( R MA ), we observe a transition from isotropic actin meshes to contractile, coarsened architectures marked by bundled filaments and increasing spatial correlation lengths ( ξ z , ξ t ). Optical tweezers microrheology reveals a nonmonotonic mechanical response: at low R MA , networks fluidize, with reductions in the plateau modulus ( G 0 ), zero-shear viscosity ( η 0 ), and fast relaxation timescales ( , τ 1 ). At higher motor levels, the networks stiffen and retain internal stress, reflecting contractile reinforcement. Notably, τ 1 exhibits a minimum when plotted against ξ z , suggesting that intermediate levels of coarsening facilitate efficient local stress dissipation. These results identify distinct mechanical regimes governed by motor-induced remodeling and highlight a structural basis for the dual roles of myosin in fluidization and reinforcement.

Toward a role for the acoustic field in cells interaction

2025-06-18

M. Girasole , P. F. Moretti , Angela Di Giannatale +5 more | Frontiers in Systems Neuroscience

Nanoscale motility of cells is a fundamental phenomenon, closely associated with biological status and response to environmental solicitations, whose investigation has disclosed new perspectives for the comprehension of cell behavior … Nanoscale motility of cells is a fundamental phenomenon, closely associated with biological status and response to environmental solicitations, whose investigation has disclosed new perspectives for the comprehension of cell behavior and fate. To investigate intracellular interactions, we designed an experiment to monitor movements of clusters of neuroblastoma cells (SH-SY5Y) growing on a nanomechanical oscillator (nanomotion sensor) suspended few hundreds of microns over the surface of a Petri dish where other neuroblastoma cells are freely moving. We observed that the free-to-move cells feel the presence of cells on the nearby nanosensor (at a distance of up to 300 microns) and migrate toward them, even in presence of environmental hampering factors, such as medium microflows. The interaction is bidirectional since, as evidenced by nanomotion sensing, the cells on the sensor enhance their motion when clusters of freely moving cells approach. Considering the geometry and environmental context, our observations extend beyond what can be explained by sensing of chemical trackers, suggesting the presence of other physical mechanisms. We hypothesize that the acoustic field generated by cell vibrations can have a role in the initial recognition between distant clusters. Integrating our findings with a suitable wave propagation model, we show that mechanical waves produced by cellular activity have sufficient energy to trigger mechanotransduction in target cells hundreds of microns away. This interaction can explain the observed distance-dependent patterns of cellular migration and motion alteration. Our results suggest that acoustic fields generated by cells can mediate cell-cell interaction and contribute to signaling and communication.

Regulation of Nuclear Deformation via Spatiotemporal Modulation of Cytoskeleton Forces on Photo-switchable Surfaces

2025-06-18

Francesca Mauro , Carlo F. Natale , Valeria Panzetta +2 more | Biomaterials

Feedback between F-actin organization and active stress governs criticality and energy localization in the cell cytoskeleton

2025-06-18

Zachary Gao Sun , Nathan Zimmerberg , Patrick Kelly +3 more | Nature Physics

SON-Related Syndrome: A Nuclear Speckleopathy

2025-06-18

Singanamalla Bhanudeep , Bramhini Bhargavi Koneti | Neurology India

Comprehensive Analysis of Shear Deformation Cytometry Based on Numerical Simulation Method

2025-06-17

Jun Wang , Jiahe Chen , Wenlai Tang +1 more | Biosensors

The deformability of cells reflects their capacity for shape changes under external forces; however, the systematic investigation of deformation-influencing factors remains conspicuously underdeveloped. In this work, by using an incompressible … The deformability of cells reflects their capacity for shape changes under external forces; however, the systematic investigation of deformation-influencing factors remains conspicuously underdeveloped. In this work, by using an incompressible neo-Hookean viscoelastic solid model, coupled with the Kelvin-Voigt model, the effects of flow rate, fluid viscosity, cell diameter, and shear modulus on cell deformability were systematically calculated and simulated. Additionally, the relationship between cell deformability and relaxation time within a dissipative process was also simulated. The results indicate that cell deformation is positively correlated with flow rate, with an approximate linear relationship between the deformation index and flow velocity. Fluid viscosity also significantly affects cell deformation, as an approximate linear relationship with the deformation index is observed. Cell diameter has a more prominent impact on cell deformability than do flow rate or fluid viscosity, with the deformation index increasing more rapidly than the cell diameter. As the Young's modulus increases, cell deformation decreases non-linearly. Cell deformation in the channel also gradually decreases with the increase in relaxation time. These findings enhance the understanding of cell biophysical characteristics and provide a basis for the precise control of cell deformation in deformability cytometry. This research holds significant implications for cell analysis-based animal health monitoring in the field of agriculture, as well as for other related areas.

Injectable Thymosin β4-Modified Hyaluronic Acid Hydrogel with Exosomes for Stem Cell Homing and Neuronic–Angiogenic–Osteogenic Coupled Cranial Repair

2025-06-17

Yanhai Xi , Zhen Zhang , Zixuan Zhao +7 more | ACS Nano

Accelerating angiogenesis, neurogenesis, and in situ stem cell recruitment at the site of bone defects is critical for bone regenerative repair. Bone marrow mesenchymal stem cell (BMSC) exosomes are cell-free … Accelerating angiogenesis, neurogenesis, and in situ stem cell recruitment at the site of bone defects is critical for bone regenerative repair. Bone marrow mesenchymal stem cell (BMSC) exosomes are cell-free therapeutic agents with bone-enhancing effects. Thymosin β4 (Tβ4) is a short peptide known for its key role in tissue repair and angiogenesis. In this study, we successfully developed a multifunctional injectable Exo@Tβ4/HAMA hydrogel platform by grafting Tβ4 onto methylmalonic anhydride-modified hyaluronic acid (HAMA) via photo-cross-linking and then encapsulating BMSC-derived exosomes. In vitro results demonstrated that the Exo@Tβ4/HAMA hydrogel exhibited improved mechanical properties, favorable biocompatibility, and the ability to significantly recruit BMSCs. Additionally, it showed superior vasculogenic effects on HUVECs and osteogenic differentiation potentials on BMSCs. In vivo studies revealed that the hydrogel successfully promoted both neurogenesis, angiogenesis, and new bone formation. It also facilitated osteogenesis through the ERK1/2-dependent RUNX2 signaling pathway. Our results suggest that this hydrogel platform exerts a robust multisystemic regulatory effect, fostering rat bone repair through the synergistic promotion of in situ stem cell recruitment, angiogenesis, neurogenesis, and osteogenesis. As a simple-to-prepare and multifunctional integrated bone graft, this hydrogel platform holds a significant promise in establishing a conducive microenvironment for optimal bone healing.

Influence of Aging and Diabetes on the Mechanical Properties of Mouse Skin

2025-06-17

Sarah Miny , Gaël Runel , Julien Chlasta +1 more | Dermatopathology

Diabetics accumulate Advanced Glycation End products (AGEs) such as Nε-(carboxymethyl)lysine (CML) in their skin, which can provoke changes in the skin's biomechanical properties. The same changes are also observed during … Diabetics accumulate Advanced Glycation End products (AGEs) such as Nε-(carboxymethyl)lysine (CML) in their skin, which can provoke changes in the skin's biomechanical properties. The same changes are also observed during aging. Collagen is one of the first targets of glycation, and this leads to the disruption of the dermis, potentially contributing to the skin complications seen in diabetes, like impaired wound healing and the formation of chronic ulcers. We therefore investigated whether it was possible to detect differences in the biomechanical properties of the reticular dermis by comparing C57/BL6 control mice, type 1 and type 2 diabetic mice, and aged mice. To investigate this, we used an Atomic Force Microscope (a type of local probe microscope used to visualize the surface topography of a sample) to measure the elastic modulus of each skin sample. The elastic modulus is a parameter that describes a tissue's resistance to elastic deformation when stress is applied. We also determined whether diabetes is associated with the accumulation of AGEs via Western blots. We found that type 2 diabetic mice and aged mice had a stiffer reticular dermis than young control mice. No differences were found in type 1 diabetic mice. The results of the Western blot did not reveal any significant differences in the CML content in different types of mice, although a non-significant increase was found in type 2 diabetic and aged mice. We show that there is a significant positive correlation between the amount of CML in a mouse and the rigidity of its reticular dermis. We have demonstrated that increased glycation in mouse skin is correlated with the biomechanical properties of that skin, which explains the wound healing defects diabetic patient's experience. AFM is therefore a powerful technique that could be used to characterize the mechanical effects of treatments aimed at reducing the level of AGEs in the skin.

Extracellular Matrix Viscoelasticity: A Dynamic Regulator of Cellular Behavior

2025-06-17

Hossein Eslami , Ahmad Darvishi | Annals of Biomedical Engineering

Monocytes use protrusive forces to generate migration paths in viscoelastic collagen-based extracellular matrices

2025-06-16

Kolade Adebowale , Cole Allan , Byung Hang Ha +7 more | Proceedings of the National Academy of Sciences

Circulating monocytes are recruited to the tumor microenvironment, where they can differentiate into macrophages that mediate tumor progression. To reach the tumor microenvironment, monocytes must first extravasate and migrate through … Circulating monocytes are recruited to the tumor microenvironment, where they can differentiate into macrophages that mediate tumor progression. To reach the tumor microenvironment, monocytes must first extravasate and migrate through the type-1 collagen rich stromal matrix. The viscoelastic stromal matrix around tumors not only stiffens relative to normal stromal matrix, but often exhibits enhanced viscous characteristics, as indicated by a higher loss tangent or faster stress relaxation rate. Here, we studied how changes in matrix stiffness and viscoelasticity impact the three-dimensional (3D) migration of monocytes through stromal-like matrices. Interpenetrating networks of type-1 collagen and alginate, which enable independent tunability of stiffness and stress relaxation over physiologically relevant ranges, were used as confining matrices for 3D culture of monocytes. Increased stiffness and faster stress relaxation independently enhanced the 3D migration of monocytes. Migrating monocytes have an ellipsoidal or rounded wedge-like morphology, reminiscent of amoeboid migration, with accumulation of actin at the trailing edge. Matrix adhesions were dispensable for monocyte migration in 3D, but migration did require actin polymerization and myosin contractility. Mechanistic studies indicate that actin polymerization at the leading edge generates protrusive forces that open a path for the monocytes to migrate through in the confining viscoelastic matrices. Taken together, our findings implicate matrix stiffness and stress relaxation as key mediators of monocyte migration and reveal how monocytes use pushing forces at the leading edge mediated by actin polymerization to generate migration paths in confining viscoelastic matrices.

Phosphoproteomic Analysis of <scp>CARMIL1</scp> Reveals Novel Regulatory Mechanisms and Upstream Kinases Involved in Actin Dynamics and Cell Migration

2025-06-16

Akhila Sheela , Althaf Mahin , Samseera Ummar +4 more | Cytoskeleton

ABSTRACT Capping protein regulator and myosin 1 Linker 1 (CARMIL1) is a multifunctional regulator of actin polymerization, ruffle formation, and lamellipodia development, making it essential for cell spreading and migration. … ABSTRACT Capping protein regulator and myosin 1 Linker 1 (CARMIL1) is a multifunctional regulator of actin polymerization, ruffle formation, and lamellipodia development, making it essential for cell spreading and migration. While its protein‐level functions are perceived, phospho‐signaling of highly phosphorylated CARMIL1 remains unexplored. This study investigates CARMIL1 phosphorylation and its regulatory mechanisms. Global phosphoproteome datasets captured the most frequently detected and differentially regulated CARMIL1 phosphosites under different conditions to be in the CARMIL_C domain (T916, S968, and S1067). A coregulation‐based method was employed to identify interactors and upstream kinases that are coregulated with the phosphorylation sites. These sites exhibited a consistent co‐occurrence pattern including both positive and negative coregulation. The phosphosites of complex interactors showed positive and negative coregulation and were involved in cell cycle regulation and cell growth. AKT1, PAK2, and MYLK were identified as potential upstream kinases for CARMIL at S968, while WNK1 was predicted as a potential upstream kinase for S1067, suggesting distinct regulatory mechanisms for these phosphorylation sites. Phosphorylation at CDK1 S146, MAP4K2 S238, MINK1 S641, and TNIK S678 was found coregulated high with CARMIL T916 in human brain cancer. Notably, most coregulated proteins were associated with regulation of the actin cytoskeleton pathway. Our results show that phosphorylation of CARMIL1 in the C‐terminal domain highly influences actin cytoskeletal organization. It offers new insights on CARMIL1‐mediated cellular functions, deepening our comprehension of its involvement in cytoskeletal dynamics.

Spindle Orientation Regulation Is Governed by Redundant Cortical Mechanosensing and Shape-Sensing Mechanisms

2025-06-15

Rania Hadjisavva , Paris A. Skourides | International Journal of Molecular Sciences

Spindle orientation (SO) plays a critical role in tissue morphogenesis, homeostasis, and tumorigenesis by ensuring accurate division plane positioning in response to intrinsic and extrinsic cues. While SO has been … Spindle orientation (SO) plays a critical role in tissue morphogenesis, homeostasis, and tumorigenesis by ensuring accurate division plane positioning in response to intrinsic and extrinsic cues. While SO has been extensively linked to cell shape sensing and cortical forces, the interplay between shape- and force-sensing mechanisms remains poorly understood. Here, we reveal that SO is governed by two parallel mechanisms that ensure redundancy and adaptability in diverse cellular environments. Using live-cell imaging of cultured cells, we demonstrate that the long prometaphase axis (LPA) is a superior predictor of SO compared to the long interphase axis, reflecting adhesive geometry and force distribution efficiently at prometaphase. Importantly, we uncover a pivotal role for focal adhesion kinase (FAK) in mediating cortical mechanosensing to regulate SO in cells undergoing complete metaphase rounding. We show that in cells with complete metaphase rounding, FAK-dependent force sensing aligns the spindle with the major force vector, ensuring accurate division. Conversely, in cells retaining shape anisotropy during mitosis, a FAK-independent shape-sensing mechanism drives SO. These findings highlight a dual regulatory system for SO, where shape sensing and force sensing operate in parallel to maintain division plane fidelity, shedding light on the mechanisms that enable cells to adapt to diverse physical and mechanical environments.

A role for class I p21-activated kinases in the regulation of the excitability of the actin cytoskeleton

2025-06-15

Joe Tyler , Anthony C. Davidson , Megan E. Poxon +4 more | Journal of Cell Science

ABSTRACT The p21-activated kinases (PAKs) are involved in a range of functions, including the regulation of the actin cytoskeleton. However, although many PAK substrates identified have been implicated in the … ABSTRACT The p21-activated kinases (PAKs) are involved in a range of functions, including the regulation of the actin cytoskeleton. However, although many PAK substrates identified have been implicated in the regulation of the actin cytoskeleton, a coherent picture of the total effect of PAK activation on the state of the actin cytoskeleton is unclear. Here, we show that, in mouse embryonic fibroblasts, inhibition of class I PAK kinase activity by small-molecule inhibitors leads to the constitutive production of the phosphoinositide phosphatidylinositol (3,4,5)-trisphosphate [PI(3,4,5)P3] on the ventral surface of the cell. The formation of patches of PI(3,4,5)P3 remodels the actin cytoskeleton and polarises the cell. From the overexpression of truncated and mutated PAK1 and PAK2 constructs, as well as an in vitro model of PAK activation, we propose that this is driven by a hyper recruitment of class I PAK and PAK-binding partners. This aberrant production of PI(3,4,5)P3 suggests that, by limiting its own recruitment, the kinase activity of class I PAKs acts to downregulate phosphoinositide 3-kinase (PI3K) activity, further highlighting class I PAKs as regulators of PI3K activity and therefore the excitability of the actin cytoskeleton.

Mechanochemical feedback between confinement and actin crosslinking drives the shape dynamics of liquid-like droplets

2025-06-15

Daniel Mansour , Dominique Jordan , Caleb Walker +5 more | bioRxiv (Cold Spring Harbor Laboratory)

Several actin-binding proteins can form liquid-liquid phase-separated condensates that promote actin filament assembly and bundling, which is crucial for local actin network organization. Previous studies have established that phase-separated condensates … Several actin-binding proteins can form liquid-liquid phase-separated condensates that promote actin filament assembly and bundling, which is crucial for local actin network organization. Previous studies have established that phase-separated condensates composed of actin-binding proteins, such as vasodilator-stimulated phosphoprotein (VASP) and Lamellipodin (Lpd), restrict the organization of actin filaments to structures such as rings, shells, discs, and rods through kinetic trapping. However, the mechanism by which crosslinker multivalency, actin growth, and condensate properties tune actin organization and droplet shape is not well understood. Using a combination of agent-based simulations and experiments, we find that the deformability of the droplet interface allows for the emergence of not just tightly-bundled actin rings but also weakly-bundled actin discs. We find two major quantitative relationships between actin bundling and droplet deformation. The first relationship shows that the crosslinked bundle thickness and droplet diameter followed a power law, consistent with experiments. The second one is that the kinetics of droplet deformation follows a dynamic snapping behavior that depends on the droplet surface tension and the multivalent VASP-actin binding kinetics. We predicted that these two relationships were generalizable to dynamic multimers and to weak actin crosslinkers. Our predictions were experimentally tested using two additional condensate-forming proteins, lamellipodin and RGG. Taken together, we show that mechanochemical feedback between the droplet interface properties and crosslinker multivalency tune actin organization and control the dynamics of droplet deformation by actin networks.

In vivo assessment of kinematic relationships for epithelial morphogenesis

2025-06-15

T. Namba , Kaoru Sugimura , Shuji Ishihara | The European Physical Journal E

Abstract Tissue growth and deformation result from the combined effects of various cellular events, including cell shape change, cell rearrangement, cell division, and cell death. Resolving and integrating these cellular … Abstract Tissue growth and deformation result from the combined effects of various cellular events, including cell shape change, cell rearrangement, cell division, and cell death. Resolving and integrating these cellular events is essential for understanding the coordination of tissue-scale growth and deformation by individual cellular behaviors that are critical for morphogenesis, wound healing, and other collective cellular phenomena. For epithelial tissues composed of tightly connected cells, the texture tensor method provides a unified framework for quantifying tissue and cell strains by tracking individual cells in live imaging data. The corresponding kinematic relationships have been introduced in a hydrodynamic model that we previously reported. In this study, we quantitatively evaluated the kinematic equations proposed in the hydrodynamic model using experimental data from a growing Drosophila wing. To accomplish this, we introduced modified definitions of the texture tensor and confirmed that one of these modifications more accurately represents approximated cellular shapes without relying on ad hoc scaling factors. By utilizing the modified tensor, we demonstrated the compatibility of the strain rate tensors and the accuracy of both the kinematic and cell number density equations. These results cross-validate the modified texture analysis and the hydrodynamic model. Furthermore, the precision of the kinematic relationships achieved in this study provides a robust foundation for more advanced integration of modeling and experiment. Graphic abstract

Resonance assignment of the intrinsically disordered actin-binding region of Drebrin

2025-06-14

Soma Varga , Julie Maibøll Kaasen , Zoltán Gáspári +2 more | Biomolecular NMR Assignments

Abstract Drebrin (developmentally regulated brain protein) is a vital component of the Postsynaptic Density (PSD). It performs important biological roles as it interacts with the postsynaptic protein Homer and anchors … Abstract Drebrin (developmentally regulated brain protein) is a vital component of the Postsynaptic Density (PSD). It performs important biological roles as it interacts with the postsynaptic protein Homer and anchors the complete protein network to the cellular skeleton through actin filaments. Drebrin contains unique structural elements including an evolutionarily unconventional actin-depolymerizing factor homology (ADFH) domain that has lost its strong actin-binding ability, and a Single Alpha-Helix (SAH) motif harbored by long flexible regions. In vivo studies have suggested that a disordered segment in Drebrin plays a key role in binding filamentous actin, yet the atomic-level characterization of the binding interface between these proteins has not been reported. To bridge this gap, we designed the intrinsically disordered construct D233 and employed 3D (HN)CO(CO)NH NMR spectroscopy to accomplish a near-complete backbone resonance assignment. This work serves as an essential step toward a detailed structural and functional investigation of the interaction between Drebrin and F-Actin.

Photonic Crystal Array Enhanced Cellular Force Microscopy for High-Throughput Detection of Regulated Cell Death and Cytopathic Effects

2025-06-14

Yifu Fu , Xiling Guo , Qiwei Li +4 more | ACS Nano

Regulated cell death (RCD) is pivotal in developmental biology, disease pathology, target identification, and drug discovery. Existing RCD detection methods, reliant on biomarkers and fluorescent staining, are often cumbersome and … Regulated cell death (RCD) is pivotal in developmental biology, disease pathology, target identification, and drug discovery. Existing RCD detection methods, reliant on biomarkers and fluorescent staining, are often cumbersome and limited to end point assessments. To enable real-time monitoring of RCD progression, we introduce an array-based photonic crystal cellular force microscopy (PCCFM) platform. This innovative system utilizes a series of photonic crystal patterns, varying in area and shape, to translate micro- to nanoscale cellular deformations during RCD into discernible color shifts in the photonic crystals. The implementation of this array architecture enhances the photonic crystal substrate's utilization efficiency, facilitating the seamless transition between multiple fields of view during detection. This advancement overcomes the constraints of single-field observation. Here, we report the continuous changes in single-cell mechanics during RCD and the changes in the cell layer mechanics during cytopathic effects (CPE), revealing that these changes are associated with cytoskeletal movement. Moreover, our PCCFM approach provides real-time, in situ detection of RCD, overcoming limitations of conventional LIVE/DEAD staining and biomarker assessments by detecting changes at an earlier stage. Furthermore, our findings demonstrate that PCCFM can detect CPE approximately 24 h earlier than bright-field microscopy-based observations. As a nonspecific, in situ, and real-time cellular force detection tool, PCCFM enables early detection of RCD and can be applied to high-throughput drug screening and early identification of CPE.

Cell state-specific cytoplasmic density controls spindle architecture and scaling

2025-06-13

Tobias Kletter , Omar Muñoz , Sebastian Reusch +6 more | Nature Cell Biology

Apical constriction in morphogenesis: From actomyosin architecture to regulatory networks

2025-06-12

Samara N. Ranie , Melanie D. White | Current Opinion in Cell Biology

Apical constriction is a key morphogenetic process driving tissue remodelling throughout life, including early developmental events. Once thought to occur through uniform actomyosin ring contraction, it is now recognized as … Apical constriction is a key morphogenetic process driving tissue remodelling throughout life, including early developmental events. Once thought to occur through uniform actomyosin ring contraction, it is now recognized as a dynamic process with diverse actomyosin architectures across species, tissues, and cell types. Regulation of apical constriction involves multiple scales, from tissue mechanics to junctional remodelling and protein trafficking. New studies are revealing how this process is controlled through actomyosin cortex organization, cytoskeletal-junctional interactions, and junctional protein levels. Considering how variable actomyosin structures are integrated with emerging regulatory pathways across different models will be crucial. Advances in in vivo live imaging promise deeper insights into the regulatory networks coordinating actomyosin dynamics and apical constriction, shedding light on its role in shaping tissues during development.

Unraveling a novel missense mutation (c.A248C) in Wiskott-Aldrich syndrome gene by whole exome sequencing: Insights from dynamic simulation, molecular docking and in-silico studies

2025-06-12

Fatemeh Mohammad-Rezaei , Javad Saffari‐Chaleshtori , Kolsoum InanlooRahatloo +2 more | International Immunopharmacology

Intracellular pressure: Regulation, characterization and implication

2025-06-12

Ruotian Du , Yizhuo Wu , Min Zou +6 more | Science China Physics Mechanics and Astronomy

Actin-Like Protein 6A as an Oncogene and Therapeutic Target in Cancer

2025-06-12

Guobin Song , Lin Xiang , Peng Tian +3 more | International Journal of Medical Sciences