Yeon Jeong Kim^1,2, Soo Jin Hwang^1,2,3, Yong Chan Bae⁴ and Jin Sup Jung^1,2,3,5,*

¹ Department of Physiology, School of Medicine, Pusan National University, Yangsan, Gyeongnam 626-870, Korea

² Medical Research Center for Ischemic Tissue Engineering, Pusan National University, Yangsan, Gyeongnam 626-870, Korea

³ BK21 Medical Science Education Center, School of Medicine, Pusan National University, Yangsan, Gyeongnam 626-870, Korea

⁴ Department of Plastic Surgery, School of Medicine, Pusan National University, Pusan 602-739, Korea

⁵ Medical Research Institute, Pusan National University, Pusan 602-739, Korea

^* Corresponding author

Abstract

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

Keywords: microRNA; Human adipose tissue-derived mesenchymal stem cells; Adipogenic differentiation; microRNA-21; TGF-β