Mechanical Stimulation Differentially Controls Proliferation, Morphology, and Vascular Gene and Protein Expression in Mesenchymal Progenitor Cells

Introduction: Cyclic strain can regulate smooth muscle cell (SMC) gene and protein expression in mesenchymal progenitor cells (MPCs). We tested the hypothesis that the differentiation of BMPCs to endothelial cells (ECs) and SMCs may be controlled by the appropriate type, magnitude, and frequency of mechanical stimulation. Methods: Bone marrow MPCs were seeded onto collagen I substrates and exposed to three stimuli – cyclic strain (CS), cyclic pressure (CP), steady shear stress (SS) – at 3 magnitudes and 2 frequencies for 5 days. Morphology and proliferation were analyzed by Scion Image. Protein expression was examined via immunohistochemistry. RT‐PCR was used to quantify genes relevant to various cell phenotypes and matrix proteins. Results: MPCs responded differentially via changes in morphology, proliferation, gene, and protein expression. Cell size correlated negatively with SS and positively with CP. Proliferation was enhanced by CP, but decreased in for SS. CS caused a sequential increase in the number of SMC proteins. Although gene expression for EC and SMC genes was elevated in CP and SS, respectively, no protein expression was found. Most ECM genes were up‐regulated under CP, while only collagen I was increased in SS. Increases in TGFβ gene expression correlated with SMC and collagen I gene expression. Conclusions: We conclude that the differentiation of MPCs towards SMCs and ECs may be regulated, in part, by the specific mechanical stimulus applied. This work was funded by the NIH BRP grant # R01 HL069368, NIH training grant # T32 EB001026, Ruth L. Kirschstein predoctoral fellowship #F31 EB004791, and American Heart Association predoctoral fellowship #0415437U.