Effect of cyclic uniaxial strain on morphology of mesenchymal stem cells during differentiation to smooth muscle cells

Introduction: Cells and tissues are mainly exposed to different mechanical stimuli, which are essential for their function. Blood vessels are subjected to circumferential straining induced by pulse pressure. The phenotype regulation and function of vascular smooth muscle cells depend on both chemical factors and their mechanical environment. Chemical and mechanical stem cell stimulations can contribute to their differentiation to functional target cells, including smooth muscle cells. This makes a great potential subject for cell therapy and tissue engineering. Here, we evaluated effects of short term uniaxial cyclic strain on morphology of rabbit adipose derived mesenchymal stem cells. Materials and Methods: Using a custom made bioreactor, a 5% cyclic uniaxial strain with 1Hz frequency were applied on mesenchymal stem cells for 4, 8 and 24 hours. Smooth muscle specific gene expression was analyzed by Real Time PCR. Before and after experiments, cell images were taken and processed for morphological parameters evaluation. Results: Cyclic strain caused cells to re-orient to the direction that cell body were experiencing minimal force. Two fold increases in smooth muscle gene expression was observed after 24 hour mechanical stimulation. Cyclic strain caused morphological alterations including reduction of cell shape index up to 41%, and elevation of aspect ratio up to 45% after 24 hours loading compared to control samples. Conclusion: Cyclic strain caused significant elongation of mesenchymal stem cells close to contractile smooth muscle phenotype. This method can be applied in cardiovascular tissue engineering to provide functional smooth muscle cells.