Electrophysiological maturation of rat mesenchymal stem cells after induction of vascular smooth muscle cell differentiation in vitro.

Previous studies have suggested that mesenchymal stem cells (MSCs) can differentiate into smooth muscle-like cells. However their functionalities remain questionable. The aim of this study was to investigate the functionality of MSCs differentiated into smooth muscle (SM) in vitro by SM-inducing medium. MSCs have been isolated from rat bone marrow and cultured in SM-inducing medium. After 21 days in culture, messenger RNA and specific SM proteins such as myosin heavy chain and myosin light chain 2 were expressed in the in vitro differentiated MSCs to a similar level of that in freshly isolated SM cells (SMCs). At the electrophysiological level, MSCs presented an outward K+ current with an IK(DR) component and IK(Ca) component. In vitro differentiation induced an enhancement of the IK(Ca) current to a level similar to that observed in aortic SMCs. Calcium homeostasis measurements revealed that both differentiated and undifferentiated MSCs responded to extracellular adenosine triphosphate (ATP) in a similar fashion to SMCs. However MSCs failed to contract in response to ATP. This data shows that despite specific SM protein expression and modification of electrophysiological properties similar to that of aortic SMCs, MSCs cultured in differentiation medium failed to display contractile properties. These results underline the necessity to find the ideal cultured conditions to induce complete SMC function.