Contribution of intermediate filaments to cell stiffness, stiffening, and growth

Abstract

It has been shown previously that intermediate filament (IF) gels in vitro exhibit stiffening at high-applied stress, and it was suggested that this stiffening property of IFs might be important for maintaining cell integrity at large deformations (Janmey PA, Evtenever V, Traub P, and Schliwa M, J Cell Biol 113: 155-160, 1991). In this study, the contribution of IFs to cell mechanical behavior was investigated by measuring cell stiffness in response to applied stress in adherent wild-type and vimentin-deficient fibroblasts using magnetic twisting cytometry. It was found that vimentin-deficient cells were less stiff and exhibited less stiffening than wild-type cells, except at the lowest applied stress (10 dyn/cm(2)) where the difference in the stiffness was not significant. Similar results were obtained from measurements on wild-type fibroblasts and endothelial cells after vimentin IFs were disrupted by acrylamide. If, however, cells were plated over an extended period of time (16 h), they exhibited a significantly greater stiffness before than after acrylamide, even at the lowest applied stress. A possible reason could be that the initially slack IFs became fully extended due to a high degree of cell spreading and thus contributed to the transmission of mechanical stress across the cell. Taken together, these findings were consistent with the notion that IFs play important roles in the mechanical properties of the cell during large deformation. The experimental data also showed that depleting or disrupting IFs reduced, but did not entirely abolish, cell stiffening. This residual stiffening might be attributed to the effect of geometrical realignment of cytoskeletal filaments in the direction of applied load. It was also found that vimentin-deficient cells exhibited a slower rate of proliferation and DNA synthesis than wild-type cells. This could be a direct consequence of the absence of the intracellular IFs that may be necessary for efficient mediation of mechanical signals within the cell. Taken together, results of this study suggest that IFs play important roles in the mechanical properties of cells and in cell growth.

Deformability of Human Mesenchymal Stem Cells Is Dependent on Vimentin Intermediate Filaments

“…Changes in MSC mechanical 10 properties have been found to be related to both their physical environment and 11 differentiation potential 10,19,20,37 . Mechanical properties and mechanotransduction are in 12 part regulated by the cytoskeleton, consisting primarily of actin microfilaments, 13 microtubules, and vimentin intermediate filaments (IFs) for cells of mesenchymal 14 lineage 5,7,19,23,24,29,30,34,36 . While their role in the pathogenesis of OA is still unknown, 15 vimentin IFs have recently been found to be disrupted or dispersed in osteoarthritic 16 chondrocytes 4,16 .…”

“…19 20 The role of vimentin is still being examined using a variety of techniques to decrease, 21 disrupt, or collapse vimentin IFs, but it is clear that they are involved in modulating the 22 mechanical properties of cells. In fibroblasts, mutations resulting in vimentin deficiency 23 have been linked to not only impaired migration, but also reduction of mechanical 1 stability and stiffness of the cytoplasm 13,34 . Further, in these cells, decreases in 2 vimentin led to compromised ability for fibroblasts to contract collagen gels, which is 3 critical for wound healing 7 .…”

Keratins as the main component for the mechanical integrity of keratinocytes

“…These observations are in line with reports on other IF systems. For example, vimentin-deficient fibroblasts presented a reduced stiffness on mechanical stress application by extracellular magnetic twisting cytometry (35). In another study, Brown et al (36) noted that the rigidity of T lymphocytes depends primarily on intact vimentin filaments as determined by flow cytometry.…”

Comparative study on the differential mechanical properties of human liver cancer and normal cells

“…Because cytoskeletal proteins influence cellular mechanical properties as the primary force-bearing structure (Stamenović & Coughlin 1999;Wang & Stamenović 2000; Wu et al , and actin-disruptive (CD) conditions. For all conditions, THLE-2 cells had higher elastic moduli than did cancerous cells.…”