RESUMEN
Cell vital function has correlation with mechanical loadings that cell experiences. Here, effects of in-vitro combined cyclic-static stretch on proliferation of human mesenchymal stem cell [HMSC] were evaluated. HMSCs were cultured on gelatin coated elastic membranes, and exposed to stretch loading. Four different regimes of cyclic, static, combined cyclic-static, and cyclic with a period of unloading were exerted on the elastic membrane. Duration of cyclic loading and static loading was 5 and 12 hours respectively. The results illustrate that 10% cyclic stretch causes cell alignment but there were no significant proliferation differences between control and test group. Combined cyclic-static stretch reduced proliferation significantly while cyclic stretch with an unloading period increased cell proliferation significantly. At last, static stretch did not affect cell proliferation significantly. Cell stretching regimes and post-loading duration are effective factors on cell proliferation
RESUMEN
Endothelium is a selective and permeable membrane for transferring nutrients and vital components to arterial wall. Endothelial damage might lead to altered biological function of endothelium and clinical consequences such as atherosclerosis. Blood pressure pulse always exerts circumferential tension to the arterial wall. Hence, such tension together with other loads, play important role in functional properties of endothelial cells. Previous studies verify effects of cyclic loading on adaptation and remodeling of endothelium. This study investigates structural properties of cultured endothelial cells subjected to uni-axial cyclic loading. Human umbilical vein endothelial cells, prepared from national cell bank of Iran [NCBI-C554], were cultured on silicon membrane, and then subjected to cyclic tension with 10% amplitude and 1 Hz frequency, and 2, 4, 6, 8 hour durations utilizing a custom made tensile device. Viscoelastic properties of endothelial cells were examined by micropipette aspiration technique. Results show increase in elastic modulus [E] of cells due to tensile cyclic loading which results in stiffening of cell body. Also results show primary increase then subsequent decrease in viscose modulus. Previous studies verify generation of stress fibers due to accumulation and increase in actin fibers in endothelial cells after tensile cyclic loading. Since mechanical and structural properties of endothelial cells depend on actin fibers, results of this study show tensile cyclic loading causes increase in stiffness of endothelial cells through generation of stress fibers