Previous studies have shown that TGF-b induces the expression of various smooth muscle markers in MSCs, and the combination of mechanical strain and TGF-b further promoted MSC differentiation into SMCs [19,22,23,24,25,29]. In addition, TGF-b induced differentiation of smooth muscle lineage from a mouse NCSC line [26]. Here we showed that both mechanical strain and TGF-b, but no PDGF (data not shown), induced an increase of contractile markers such as CNN1, and the combination of the two factors had additive effects. Even though NB medium suppressed the basal level of SMC marker expression, mechanical strain still induced CNN expression. These results suggest that mechanical strain works in parallel with biochemical factors to regulate NCSC differentiation. How mechanical strain regulates stem cell differentiation at different stages has not been addressed previously. 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(2006) Cyclic strain induces expression of specific smooth muscle cell markers in human endothelial cells. Differentiation 74: 552–561. PLoS ONE | www.plosone.org 8 October 2011 | Volume 6 | Issue 10 | e26029