Abstract 1051: Mechanical Stimulation Differentially Controls Proliferation, Morphology, and Vascular Gene and Protein Expression in Mesenchymal Progenitor Cells
Introduction: Cyclic strain has been shown to regulate smooth muscle cell (SMC) gene and protein expression in bone marrow mesenchymal progenitor cells (BMPCs). We are testing our 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: BMPCs obtained from the Tulane Center for Gene Therapy were seeded onto collagen I coated substrates and exposed to our Mechanical Panel, which tests the effects of each of three stimuli - cyclic strain (CS), cyclic pressure (CP) and steady shear stress (SS). We tested 1, 5, 10% CS at 1Hz or 1% CS at 2.75Hz; 90/70, 120/80, 180/140 mmHg CP at 1Hz or 90/70 mmHg at 2.75Hz; 1, 5, 10, or 20 dynes/cm2 LSS; or static conditions (control) for 5 days. Morphology and proliferation were analyzed by Scion Image. Protein expression was examined via immunohistochemistry for EC and SMC markers. RT-PCR was used to quantify genes relevant to adipocytes, chondrocytes, SMCs, and ECs as well as extracellular matrix (ECM), growth factor, and apoptosis proteins.
Results: BMPCs responded differentially to the individual stimuli (n=4 – 6) 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 a dose-dependent manner for SS. CS caused a sequential increase in the number of SMC markers. The EC marker Flk-1 was found in control, CS, and some LSS and CP samples. Gene expression data (n=1–3) corroborated the Flk-1 expression to the protein data. Although gene expression for EC and SMC markers 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 appeared to correlate with SMC and collagen I gene expression.
Conclusions: We conclude that the differentiation of BMPCs towards SMCs and ECs may be regulated, in part, by the specific mechanical stimulus applied. Our data revealed a complicated differentiation state, possibly controlled by post-transcriptional regulation which, when understood, may have applications to regenerative medicine and tissue engineering applications.