Endothelial differentiation of mesenchymal stem cells induced by the combined mechanical stimulation of wall shear stress and cyclic strain

Abstract

Differentiation of mesenchymal stem cells (MSCs) into vascular endothelial cells has been demonstrated for application in cardiovascular regenerative medicine. In this study, we evaluated the effect of the combined mechanical stimuli of wall shear stress (SS) and cyclic strain (CS), mimicking hemodynamic conditions of arteries, on endothelial differentiation of MSCs. Immortalized human adipose-derived MSCs were subjected to a combined stimulations of SS (1 Pa) and CS (4%, 1 Hz) by using a developed cell culture chamber. Endothelial differentiation of MSCs was evaluated by immunofluorescent staining of an endothelial protein maker, fetal liver kinase-1 (Flk-1). Morphological changes in MSCs by the stimulation were also examined from the fluorescent images. As a result, the application of the combined stimulation of SS and CS for 24 h induced an increased expression of Flk-1 in MSCs and cell alignment to the direction of flow, whereas the stimulation of only SS or CS did not change Flk-1 expression and morphology of MSCs compared to statically cultured cells. We also found that inhibition of the activation of extracellular signal-regulated kinase 1/2 (ERK1/2) blocked the increased expression of Flk-1 under the combined mechanical condition. These results indicate that the combination of SS and CS effectively induces MSCs differentiation into endothelial cells via activation of ERK1/2 signaling pathway.