Cellular orientation is guided by strain gradients

Abstract

The strain-induced reorientation response of cyclically stretched cells has been well characterized in uniform strain fields. In the present study, we comprehensively analyse the behaviour of human fibroblasts subjected to a highly non-uniform strain field within a polymethylsiloxane microdevice. Our results indicate that the strain gradient amplitude and direction regulate cell reorientation through a coordinated gradient avoidance response. We provide critical evidence that strain gradient is a key physical cue that can guide cell organization. Specifically, our work suggests that cells are able to pinpoint the location under the cell of multiple physical cues and integrate this information (strain and strain gradient amplitudes and directions), resulting in a coordinated response. To gain insight into the underlying mechanosensing processes, we studied focal adhesion reorganization and the effect of modulating myosin-II contractility. The extracted focal adhesion orientation distributions are similar to those obtained for the cell bodies, and their density is increased by the presence of stretching forces. Moreover, it was found that the myosin-II activity promoter calyculin-A has little effect on the cellular response, while the inhibitor blebbistatin suppresses cell and focal adhesion alignment and reduces focal adhesion density. These results confirm that similar internal structures involved in sensing and responding to strain direction and amplitude are also key players in strain gradient mechanosensing and avoidance.

Time dependence of cellular responses to dynamic and complex strain fields

“…In general, the complex microenvironment in which cells evolve in vivo gives rise to non-uniform, time-varying, anisotropic strain fields [21][22][23][24] . Importantly, in our previous work 16 , we have clearly demonstrated that cells have an ability to sense and respond to both strain and strain gradients. Yet, the large majority of previous cyclic stretching studies have focused on stretch patterns with nearly-uniform strain amplitude and direction [8][9][10][11]13,15 .…”

“…Another example extensively studied to further our understanding of mechanotransduction processes is the cellular reorientation induced by cyclic stretching. More specifically, cyclically stretched cells were shown to exhibit elongation 7,8 , alignment perpendicular to the stretching direction [9][10][11][12][13][14][15] , and more recently fibroblasts were also demonstrated to exhibit strain gradient avoidance 16 .…”

Time dependence of cellular responses to dynamic and complex strain fields

“…In general, the complex microenvironment in which cells evolve in vivo gives rise to non-uniform, time-varying, anisotropic strain fields [21][22][23][24] . Importantly, in our previous work 16 , we have clearly demonstrated that cells have an ability to sense and respond to both strain and strain gradients. Yet, the large majority of previous cyclic stretching studies have focused on stretch patterns with nearly-uniform strain amplitude and direction [8][9][10][11]13,15 .…”

“…Another example extensively studied to further our understanding of mechanotransduction processes is the cellular reorientation induced by cyclic stretching. More specifically, cyclically stretched cells were shown to exhibit elongation 7,8 , alignment perpendicular to the stretching direction [9][10][11][12][13][14][15] , and more recently fibroblasts were also demonstrated to exhibit strain gradient avoidance 16 .…”

A vacuum-actuated microtissue stretcher for long-term exposure to oscillatory strain within a 3D matrix

“…[14][15][16] In this paper we describe the fabrication steps of the MVAS, and to validate our approach, we characterize the bulk microtissue strain, the microtissue strain field and single cell strain, and assess changes in F-actin expression in response to chronic cyclic strain.…”