MiR‐21 Regulates Adipogenic Differentiation through the Modulation of TGF‐β Signaling in Mesenchymal Stem Cells Derived from Human Adipose Tissue

A better understanding of the molecular mechanisms that govern human adipose tissue‐derived mesenchymal stem cells (hASCs) differentiation could improve hASCs‐based cell therapy and provide new insights into a number of diseases, including obesity. In this study, we examined the roles of microRNA‐21 (miR‐21) in adipogenic differentiation of hASCs. We found that miR‐21 expression was transiently increased after induction of adipogenic differentiation, peaked at 3 days, and returned to the baseline level 8 days. Lentiviral overexpression of miR‐21 enhanced adipogenic differentiation. Overexpression of miR‐21 decreased both protein and mRNA levels of TGFBR2. The expression of TGFBR2 was decreased during adipogenic differentiation of hASCs in concordance with an increase in the level of miR‐21. In contrast, inhibiting miR‐21 with 2′‐O‐methyl‐antisense microRNA increased TGFBR2 protein levels in hASCs, accompanied by decreased adipogenic differentiation. The activity of a luciferase construct containing the miR‐21 target site from the TGFBR2 3′UTR was lower in LV‐miR21‐infected hASCs than in LV‐miLacZ infected cells. TGF‐β‐induced inhibition of adipogenic differentiation was significantly decreased in miR‐21 overexpressing cells compared with control lentivirus‐transduced cells. RNA interference‐mediated downregulation of SMAD3, but not of SMAD2, increased adipogenic differentiation. Overexpression and inhibition of miR‐21 altered SMAD3 phosphorylation without affecting total levels of SMAD3 protein. Our data are the first to demonstrate that the role of miR‐21 in the adipogenic differentiation of hASCs is mediated through the modulation of TGF‐β signaling. This study improves our knowledge of the molecular mechanisms governing hASCs differentiation, which may underlie the development of obesity or other metabolic diseases. STEM CELLS 2009;27:3093–3102