CXCL12 and Urethral stricture: Recently study also proved that miR‐21 overexpressed MSCs can effectively induce angiogenesis potential via promoting HIF‐1a activity.24 In the present study, in order to understand the mechanism of miR‐21 modified ADSCs in counteract urethral stricture formation, we examined the expression levels of some angiogenic genes, such as VEGF, HIF‐1a and SDF‐1a.