Effect of fluid shear stress on cardiomyogenic differentiation of rat bone marrow mesenchymal stem cells

Background and Aims: Bone marrow mesenchymal stem cells (BMSCs) are a potential source of material for the construction of tissue-engineered cardiac grafts because of their potential to transdifferentiate into cardiomyocytes after chemical treatment or co-culture with cardiomyocytes. Recent evidence has shown that mechanical loads could regulate the BMSC differentiation into osteoblasts and endothelial cells through various signaling pathways. We investigated whether fluid shear stress (FSS), which is a mechanical load generated by fluid flow, can regulate rat BMSC (rBMSC) differentiation into cardiomyocytes. Methods: rBMSCs were isolated from marrow of rat femur and tibia using density gradient centrifugation combined with adhesion method and identified with surface marker, proliferation character and differentiation potential in vitro. Cultured rBMSCs with or without 5-azacytidine (5-aza) treatment were exposed to laminar shear stress with a parallel plate-type device and analyzed by RT-PCR, immunocytochemistry, FACS and Western-blotting for the cardiomyogenic differentiation. Results: Appropriate FSS treatment alone induced cardiomyogenic differentiation of rBMSCs, as confirmed by the expression of cardiomyocyte-related markers at both mRNA and protein levels. Furthermore, when rBMSC cultures were exposed to both FSS and 5-aza, expression levels of cardiomyocyte-related markers significantly increased to a degree suggestive of a synergistic interaction. Conclusions: The results demonstrate that FSS is an important factor affecting cardiomyogenic differentiation of rBMSCs. This provides a new avenue for mechanistic studies of stem cell differentiation and a new approach to obtain more committed differentiated cells.