Cyclic Stretch Effects on Adipose-Derived Stem Cell Stiffness, Morphology and Smooth Muscle Cell Gene Expression

Recent investigations consider adipose-derived stemcells (ASCs) as a promising source of stemcells for clinical therapies. To obtain functional cells with enhanced cytoskeleton and aligned structure, mechanical stimuli are utilized during differentiation of stem cells to the target cells. Since function of muscle cells is associated with cytoskeleton, enhanced structure is especially essential for these cells when employed in tissue engineering. In this study by utilizing a custom-made device, effects of uniaxial tension (1Hz, 10% stretch) on cytoskeleton, cell alignment, cell elastic properties, and expression of smooth muscle cell (SMC) genes in ASCs are investigated.Due to proper availability ofASCs, results can be employed in cardiovascular engineeringwhen production of functional SMCs in arterial reconstruction is required. Results demonstrated that cells were oriented after 24 hours of cyclic stretch with aligned pseudo-podia. Staining of actin filaments confirmed enhanced polymerization and alignment of stress fibers. Such phenomenon resulted in stiffening of cell body which was quantified by atomic force microscopy (AFM). Expression of SM α-actin and SM22 α-actin as SMC associated genes were increased after cyclic stretch while GAPDH was considered as internal control gene. Finally, it was concluded that application of cyclic stretch on ASCs assists differentiation to SMC and enhances functionality of cells.

Effects of Uniaxial Cyclic Stretch Loading on Morphology of Adipose Derived Stem Cells

Adipose derived stem cells (ADSC) are good candidates for the replacement of bone marrow derived mesenchymal stem cells due to their abundance, multipotency property, and easier accessibility. In order to explore the behavior of these cells in response to mechanical stimulation, in this study we have investigated the effects of uniaxial dynamic mechanical loading on ADSC's morphology. Stem cells derived from the fat tissue of human and after an overnight culture were seeded on a silicone rubber strips. Afterwards, cells were subjected to a uniaxial dynamic loading in three different groups. Cell images were evaluated considering different morphological parameters. Fractal dimension decreased significantly after loading while in control groups there were a significant increase (p<0.05), approving that cyclic strain would lead to more aligned and organized cells. Cell orientation also increased significantly (p<0.05). Moreover cells' orientation angle, 24 hour after loading does not change compared to the observations immediately after loading, which attests to the practicality of the cyclic strain in functional tissue engineering. Cell width decreased and cell length increased which led to a significant increase in cell shape index (p<0.05). Results confirmed that uniaxial dynamic loading affects cell morphological parameters comparing their values before and after loading. In addition, the number of cycles are also an important factor since different number of cycles lead to different amounts of certain morphological parameters. Conclusively, cyclic strain can be a practical method in the field of functional tissue engineering.

[Effects of combined cyclic-static stretch on orientation and proliferation of human mesenchymal stem cells]

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