Crucial role of Nrf3 in smooth muscle cell differentiation from stem cells

Rationale: Nuclear factor erythroid 2-related factor (Nrf)3, a member of the cap 'N' collar family of transcription factors that bind to the DNA-antioxidant responsive elements, is involved in reactive oxygen species balancing and in muscle precursor migration during early embryo development. Objective: To investigate the functional role of Nrf3 in smooth muscle cell (SMC) differentiation in vitro and in vivo. Methods and Results: Nrf3 was upregulated significantly following 1 to 8 days of SMC differentiation. Knockdown of Nrf3 resulted in downregulation of smooth muscle specific markers expression, whereas enforced expression of Nrf3 enhanced SMC differentiation in a dose-dependent manner. SMC-specific transcription factor myocardin, but not serum response factor, was significantly upregulated by Nrf3 overexpression. Strikingly, the binding of SRF and myocardin to the promoter of smooth muscle differentiation genes was dramatically increased by Nrf3 overexpression, and Nrf3 can directly bind to the promoters of SMC differentiation genes as demonstrated by chromatin immunoprecipitation assay. Moreover, NADPH-derived reactive oxygen species production during SMC differentiation was further enhanced by Nrf3 overexpression through upregulation of NADPH oxidase and inhibition of antioxidant signaling pathway. In addition, Nrf3 was involved in the endoplasmic reticulum stressor induced SMC differentiation. Conclusion: Our findings demonstrate for the first time that Nrf3 has a crucial role in SMC differentiation from stem cells indicating that Nrf3 could be a potential target for manipulation of stem cell differentiation toward vascular lineage. (Circ Res. 2010; 106: 870-879.)