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

Chitosan preparation from Persian Gulf shrimp shells and investigating the effect of time on the degree of deacetylation

Chitosan is an amino polysaccharide which can be prepared from shrimp shells with several applications in medicine and tissue engineering. The most important parameter, that characterizes chitosan and its applications, is its degree of deacetylation. In this research the influence of deacetylation time on the quality of the produced chitosan was investigated by measuring the amount of glucosamine and acetyl glucosamine. The amount of glucosamine in the sample was measured using HPLC analysis based on derivation method. By deacetylation of the extracted chitin in 90 and 180 minutes, chitosan with deacetylation degree of 69.75% and 77.63% was obtained, respectively. Therefore, by increasing the deacetylation period in a constant temperature condition and NaOH concentration, the deacetylation degree is increased

[Evaluation of effects of cyclic loading on structural properties of cultured endothelial cells]

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