The Role of Vimentin Intermediate Filaments in Cortical and Cytoplasmic Mechanics

Abstract

The mechanical properties of a cell determine many aspects of its behavior, and these mechanics are largely determined by the cytoskeleton. Although the contribution of actin filaments and microtubules to the mechanics of cells has been investigated in great detail, relatively little is known about the contribution of the third major cytoskeletal component, intermediate filaments (IFs). To determine the role of vimentin IF (VIF) in modulating intracellular and cortical mechanics, we carried out studies using mouse embryonic fibroblasts (mEFs) derived from wild-type or vimentin(-/-) mice. The VIFs contribute little to cortical stiffness but are critical for regulating intracellular mechanics. Active microrheology measurements using optical tweezers in living cells reveal that the presence of VIFs doubles the value of the cytoplasmic shear modulus to ∼10 Pa. The higher levels of cytoplasmic stiffness appear to stabilize organelles in the cell, as measured by tracking endogenous vesicle movement. These studies show that VIFs both increase the mechanical integrity of cells and localize intracellular components.

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

“…The aim is to investigate the effect of a decreased vimentin IF 11 network on MSC deformability independent of effects from cell-substrate adhesion and 12 long culture times. Our results suggest that a decrease in vimentin IFs paradoxically 13 reduces the deformability of MSCs, potentially due to changes in the manner by which 14 actin microfilaments and microtubules organize and function to resist loads. 15 17 18 hMSC cell culture 19 20 For initial lentiviral construct screening experiments, hMSCs from Lonza (Walkersville,…”

“…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 .…”

“…IF collapse caused by 10 mutated desmin revealed a complex distribution of cellular stiffness with increased 11 cellular stiffness in regions of the collapsed vimentin and a decrease in stiffness in the 12 remaining vimentin-deficient cytoplasm 25 . 13 …”

“…Both shVim-hMSCs and shLacZ-hMSCs were 12 cultured in the presence of 1µg ml -1 doxycycline to induce RNAi. Cells were cultured for 13 7, 14, or 21 days on tissue culture plastic before being harvested to be assayed. 14 …”