scholarly journals Dynamics of force generation by spreading platelets

Soft Matter ◽  
2018 ◽  
Vol 14 (31) ◽  
pp. 6571-6581 ◽  
Author(s):  
Jana Hanke ◽  
Dimitri Probst ◽  
Assaf Zemel ◽  
Ulrich S. Schwarz ◽  
Sarah Köster
Keyword(s):  
Internal Stress ◽  
Traction Force ◽  
Variable Stiffness ◽  
Human Platelets ◽  
Force Generation ◽  
Dynamic Force ◽  
Time Resolved ◽  
Force Microscopy ◽  
Elastic Substrates ◽  
High Level

Using time-resolved traction force microscopy on soft elastic substrates of variable stiffness, here we show that human platelets generate highly dynamic force patterns and an exceptionally high level of internal stress.

scholarly journals Inverting dynamic force microscopy: From signals to time-resolved interaction forces

2002 ◽  
Vol 99 (13) ◽  
pp. 8473-8478 ◽  
Author(s):  
M. Stark ◽  
R. W. Stark ◽  
W. M. Heckl ◽  
R. Guckenberger
Keyword(s):  
Dynamic Force ◽  
Interaction Forces ◽  
Time Resolved ◽  
Force Microscopy

scholarly journals Black Dots: Microcontact-Printed, Reference-Free Traction Force Microscopy

2021 ◽  
Author(s):  
Kevin M Beussman ◽  
Molly Y Mollica ◽  
Andrea Leonard ◽  
Jeffrey Miles ◽  
John Hocter ◽  
...  
Keyword(s):  
Flexible Substrate ◽  
Traction Force ◽  
Human Platelets ◽  
High Yield ◽  
Traction Forces ◽  
Cooperative Effects ◽  
Force Microscopy ◽  
Interaction Terms ◽  
Spread Area ◽  
Insight Into

Measuring the traction forces produced by cells provides insight into their behavior and physiological function. Here, we developed a technique (dubbed 'black dots') that microcontact prints a fluorescent micropattern onto a flexible substrate to measure cellular traction forces without constraining cell shape or needing to detach the cells. To demonstrate our technique, we assessed human platelets, which can generate a large range of forces within a population. We find platelets that exert more force have more spread area, are more circular, and have more uniformly distributed F-actin filaments. As a result of the high yield of data obtainable by this technique, we were able to evaluate multivariate mixed effects models with interaction terms and conduct a clustering analysis to identify clusters within our data. These statistical techniques demonstrated a complex relationship between spread area, circularity, F-actin dispersion, and platelet force, including cooperative effects that significantly associate with platelet traction forces.

scholarly journals Phagocytic 'teeth' and myosin-II 'jaw' power target constriction during phagocytosis

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Daan Vorselen ◽  
Sarah R Barger ◽  
Yifan Wang ◽  
Wei Cai ◽  
Julie A Theriot ◽  
...  
Keyword(s):  
Myosin Ii ◽  
Traction Force ◽  
Light Sheet ◽  
Force Generation ◽  
Actin Dynamics ◽  
Force Microscopy ◽  
Light Sheet Microscopy ◽  
Macrophage Phagocytosis ◽  
Actin Protrusions

Phagocytosis requires rapid actin reorganization and spatially controlled force generation to ingest targets ranging from pathogens to apoptotic cells. How actomyosin activity directs membrane extensions to engulf such diverse targets remains unclear. Here, we combine lattice light-sheet microscopy (LLSM) with microparticle traction force microscopy (MP-TFM) to quantify actin dynamics and subcellular forces during macrophage phagocytosis. We show that spatially localized forces leading to target constriction are prominent during phagocytosis of antibody-opsonized targets. This constriction is largely driven by Arp2/3-mediated assembly of discrete actin protrusions containing myosin 1e and 1f ('teeth') that appear to be interconnected in a ring-like organization. Contractile myosin-II activity contributes to late-stage phagocytic force generation and progression, supporting a specific role in phagocytic cup closure. Observations of partial target eating attempts and sudden target release via a popping mechanism suggest that constriction may be critical for resolving complex in vivo target encounters. Overall, our findings present a phagocytic cup-shaping mechanism that is distinct from cytoskeletal remodeling in 2D cell motility and may contribute to mechanosensing and phagocytic plasticity.

scholarly journals Regulation of SMC traction forces in human aortic thoracic aneurysms

2021 ◽  
Author(s):  
Claudie Petit ◽  
Ali-Akbar Karkhaneh Yousefi ◽  
Olfa Ben Moussa ◽  
Jean-Baptiste Michel ◽  
Alain Guignandon ◽  
...  
Keyword(s):  
Traction Force ◽  
Aortic Aneurysms ◽  
Force Generation ◽  
Dynamic Force ◽  
Generation Process ◽  
Traction Forces ◽  
Thoracic Aortic Aneurysms ◽  
And Gender ◽  
Thoracic Aneurysms ◽  
Future Work

AbstractSmooth muscle cells (SMCs) usually express a contractile phenotype in the healthy aorta. However, aortic SMCs have the ability to undergo profound changes in phenotype in response to changes in their extracellular environment, as occurs in ascending thoracic aortic aneurysms (ATAA). Accordingly, there is a pressing need to quantify the mechanobiological effects of these changes at single cell level. To address this need, we applied Traction Force Microscopy (TFM) on 759 cells coming from three primary healthy (AoPrim) human SMC lineages and three primary aneurysmal (AnevPrim) human SMC lineages, from age and gender matched donors. We measured the basal traction forces applied by each of these cells onto compliant hydrogels of different stiffness (4, 8, 12, 25 kPa). Although the range of force generation by SMCs suggested some heterogeneity, we observed that: 1. the traction forces were significantly larger on substrates of larger stiffness; 2. traction forces in AnevPrim were significantly higher than in AoPrim cells. We modelled computationally the dynamic force generation process in SMCs using the motor-clutch model and found that it accounts well for the stiffness-dependent traction forces. The existence of larger traction forces in the AnevPrim SMCs were related to the larger size of cells in these lineages. We conclude that phenotype changes occurring in ATAA, which were previously known to reduce the expression of elongated and contractile SMCs (rendering SMCs less responsive to vasoactive agents), tend also to induce stronger SMCs. Future work aims at understanding the causes of this alteration process in aortic aneurysms.

scholarly journals Crosstalk between myosin II and formin functions in the regulation of force generation and actomyosin dynamics in stress fibers

2021 ◽  
Author(s):  
Yukako Nishimura ◽  
Shidong Shi ◽  
Qingsen Li ◽  
Alexander D. Bershadsky ◽  
Virgile Viasnoff
Keyword(s):  
Contractile Activity ◽  
Myosin Ii ◽  
Focal Adhesions ◽  
Traction Force ◽  
Stress Fiber ◽  
Force Generation ◽  
Stress Fibers ◽  
Force Microscopy ◽  
Fiber Dynamics ◽  
The Relationship

REF52 fibroblasts have a well-developed contractile machinery, the most prominent elements of which are actomyosin stress fibers with highly ordered organization of actin and myosin IIA filaments. The relationship between contractile activity and turnover dynamics of stress fibers is not sufficiently understood. Here, we simultaneously measured the forces exerted by stress fibers (using traction force microscopy or micropillar array sensors) and the dynamics of actin and myosin (using photoconversion-based monitoring of actin incorporation and high-resolution fluorescence microscopy of myosin II light chain). Our data revealed new features of the crosstalk between myosin II-driven contractility and stress fiber dynamics. During normal stress fiber turnover, actin incorporated all along the stress fibers and not only at focal adhesions. Incorporation of actin into stress fibers/focal adhesions, as well as actin and myosin II filaments flow along stress fibers, strongly depends on myosin II activity. Myosin II-dependent generation of traction forces does not depend on incorporation of actin into stress fibers per se, but still requires formin activity. This previously overlooked function of formins in maintenance of the actin cytoskeleton connectivity could be the main mechanism of formin involvement in traction force generation.

scholarly journals Phagocytic 'teeth' and myosin-II 'jaw' power target constriction during phagocytosis

2021 ◽  
Author(s):  
Daan Vorselen ◽  
Sarah R. Barger ◽  
Yifan Wang ◽  
Wei Cai ◽  
Julie A. Theriot ◽  
...  
Keyword(s):  
Myosin Ii ◽  
Traction Force ◽  
Light Sheet ◽  
Force Generation ◽  
Actin Dynamics ◽  
Force Microscopy ◽  
Light Sheet Microscopy ◽  
Macrophage Phagocytosis ◽  
Actin Protrusions

Phagocytosis requires rapid actin reorganization and spatially controlled force generation to ingest targets ranging from pathogens to apoptotic cells. How actomyosin activity directs membrane extensions to engulf such diverse targets remains unclear. Here, we combine lattice light-sheet microscopy (LLSM) with microparticle traction force microscopy (MP-TFM) to quantify actin dynamics and subcellular forces during macrophage phagocytosis. We show that spatially localized forces leading to target constriction are prominent during phagocytosis of antibody-opsonized targets. This constriction is largely mediated by Arp2/3-mediated assembly of discrete actin protrusions containing myosin 1e and 1f ('teeth') that are interconnected in a ring-like organization. Contractile myosin-II activity contributes to late-stage phagocytic force generation and progression, suggesting a specific role in phagocytic cup closure. Observations of partial target eating attempts and sudden target release via a popping mechanism suggest that constriction may be critical for resolving complex in vivo target encounters. Overall, our findings suggest a phagocytic cup-shaping mechanism that is distinct from cytoskeletal remodeling in 2D cell motility and may contribute to mechanosensing and phagocytic plasticity.

scholarly journals How do biofilms feel their environment?

2021 ◽  
Author(s):  
Merrill Asp ◽  
Minh Tri Ho Thanh ◽  
Arvind Gopinath ◽  
Alison Elise Patteson
Keyword(s):  
Traction Force ◽  
Time Lapse ◽  
Colony Growth ◽  
Biofilm Growth ◽  
Force Microscopy ◽  
Elastic Substrates ◽  
Sense And Respond ◽  
Biofilm Development ◽  
Physical Features ◽  
Underlying Substrate

The ability of bacteria to colonize and grow on different surfaces is an essential process for biofilm development and depends on complex biomechanical interactions between the biofilm and the underlying substrate. Changes in the physical properties of the underlying substrate are known to alter biofilm expansion, but the mechanisms by which biofilms sense and respond to physical features of their environment are still poorly understood. Here, we report the use of synthetic polyacrylamide hydrogels with tunable stiffness and controllable pore size to assess physical effects of the substrate on biofilm development. Using time lapse microscopy to track the growth of expanding Serratia marcescens colonies, we find that biofilm colony growth can increase with increasing substrate stiffness on purely elastic substrates, unlike what is found on traditional agar substrates. Using traction force microscopy, we find that biofilms exert transient stresses correlated over length scales much larger than a single bacterium. Our results are consistent with a model of biofilm development in which the interplay between osmotic pressure arising from the biofilm and the poroelastic response of the underlying substrate controls biofilm growth and morphology.

scholarly journals How Localized Z-Disc Damage Affects Force Generation and Gene Expression in Cardiomyocytes

2021 ◽  
Vol 8 (12) ◽  
pp. 213
Author(s):  
Dominik Müller ◽  
Sören Donath ◽  
Emanuel Georg Brückner ◽  
Santoshi Biswanath Devadas ◽  
Fiene Daniel ◽  
...  
Keyword(s):  
Gene Expression ◽  
Troponin I ◽  
Troponin T ◽  
Laser System ◽  
Traction Force ◽  
Force Generation ◽  
Proper Function ◽  
Force Microscopy ◽  
Vitro Model

The proper function of cardiomyocytes (CMs) is highly related to the Z-disc, which has a pivotal role in orchestrating the sarcomeric cytoskeletal function. To better understand Z-disc related cardiomyopathies, novel models of Z-disc damage have to be developed. Human pluripotent stem cell (hPSC)-derived CMs can serve as an in vitro model to better understand the sarcomeric cytoskeleton. A femtosecond laser system can be applied for localized and defined damage application within cells as single Z-discs can be removed. We have investigated the changes in force generation via traction force microscopy, and in gene expression after Z-disc manipulation in hPSC-derived CMs. We observed a significant weakening of force generation after removal of a Z-disc. However, no significant changes of the number of contractions after manipulation were detected. The stress related gene NF-kB was significantly upregulated. Additionally, α-actinin (ACTN2) and filamin-C (FLNc) were upregulated, pointing to remodeling of the Z-disc and the sarcomeric cytoskeleton. Ultimately, cardiac troponin I (TNNI3) and cardiac muscle troponin T (TNNT2) were significantly downregulated. Our results allow a better understanding of transcriptional coupling of Z-disc damage and the relation of damage to force generation and can therefore finally pave the way to novel therapies of sarcomeric disorders.

scholarly journals ATP allosterically stabilizes Integrin-linked kinase for efficient force generation

2021 ◽  
Author(s):  
Isabel M. Martin ◽  
Michele M. Nava ◽  
Sara A. Wickstroem ◽  
Frauke Graeter
Keyword(s):  
Focal Adhesion ◽  
Protein Unfolding ◽  
Focal Adhesions ◽  
Traction Force ◽  
Force Generation ◽  
Force Microscopy ◽  
Integrin Linked Kinase ◽  
And Migration ◽  
Dynamics Simulations ◽  
Propagation Network

Focal adhesions link the actomyosin cytoskeleton to the extracellular matrix regulating cell adhesion, shape, and migration. Adhesions are dynamically assembled and disassembled in response to extrinsic and intrinsic forces, but how the essential adhesion component intergrin-linked kinase (ILK) dynamically responds to mechanical force and what role ATP bound to this pseudokinase plays remains elusive. Here, we apply force-probe molecular dynamics simulations of ILK:alpha-parvin coupled to traction force microscopy to explore ILK mechanotransducing functions. We identify two key saltbridge-forming arginines within the allosteric, ATP-dependent force-propagation network of ILK. Disrupting this network by mutation impedes parvin binding, focal adhesion stabilization, force generation, and thus migration. Under tension, ATP shifts the balance from rupture of the complex to protein unfolding, indicating that ATP increases the force threshold required for focal adhesion disassembly. Our study proposes a new role of ATP as an obligatory binding partner for structural and mechanical integrity of the pseudokinase ILK, ensuring efficient cellular force generation and migration.

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