The effects of short-term uniaxial strain on the mechanical properties of mesenchymal stem cells upon TGF-β1 stimulation

Cellular mechanical characteristics represent cell ability to produce tissue-specific metabolites. Therefore, to achieve effective cell therapy, a better understanding of the effects of chemo-mechanical stimuli on the mechanical properties of in vitro-treated cells is essential. Herein, we investigated the effects of uniaxial strain on the mechanical properties of mesenchymal stem cells (MSCs) upon transforming growth factor beta 1 (TGF-beta(1)) stimulation. The MSCs were categorized into control and test groups. In one test group, the MSCs were treated by TGF-beta(1) for 6 d, and in the other, they were additionally subjected to 1-d uniaxial strain on day 2. The cell mechanical properties and smooth muscle (SM) gene expression were assessed on days 2, 4, and 6. During the entire experiment, the MSCs treated by TGF-beta(1) +/- uniaxial strain were induced to differentiate into SM-like cells by significantly upregulation of alpha-actin, SM22 alpha, and hl-calponin in respect to the control samples. When the MSCs were treated with IGF-beta(1) alone, their stiffness and viscosity decreased significantly on day 2 and then increased by increase in culture time. When the cells were subjected to 1-d uniaxial strain upon TGF-beta(1) stimulation, their stiffness and viscosity significantly increased on days 2 and 4 and then decreased on day 6 to a level comparable to that of TGF-beta(1) group. Different paths were noticeable among the treated samples to reach nearly similar states on day 6. It seems that uniaxial strain activates mechanobiological cascades by which cellular mechanical behavior can be regulated after its removal. However, these effects are transient and would diminish over time. The findings may be helpful in the chemo-mechanical regulation of MSCs.