npg Function of miR-27b in cardiac hypertrophy 516 ORIGINAL ARTICLE Cell Research (2012) 22:516-527. © 2012 IBCB, SIBS, CAS All rights reserved 1002-0602/12 www.nature.com/cr npg Cardiomyocyte overexpression of miR-27b induces cardiac hypertrophy and dysfunction in mice Jian Wang1, Yao Song2, Yan Zhang1, Han Xiao2, Qiang Sun1, Ning Hou1, Shuilong Guo1, Youliang Wang1, Kaiji Fan1, Dawei Zhan3, Lagabaiyila Zha1, Yang Cao1, Zhenhua Li1, Xuan Cheng1, Youyi Zhang2, Xiao Yang1, 4 1State Key Laboratory of Proteomics, Genetic Laboratory of Development and Diseases, Institute of Biotechnology, 20 Dongda- jie, Beijing 100071, China; 2Institute of Vascular Medicine, Peking University Third Hospital and Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education, Key Laboratory of Cardiovascular Molecular Biology and Regulatory Peptides, Ministry of Health, Beijing 100191, China; 3The First Hospital Affiliated to the Chinese PLA General Hospital, Beijing 100048, China; 4Model Organism Division, E-institutes of Shanghai Universities, Shanghai Jiao Tong University, Shanghai 200240, China Recent studies have begun to reveal critical roles of microRNAs (miRNAs) in the pathogenesis of cardiac hyper- trophy and dysfunction. In this study, we tested whether a transforming growth factor-β (TGF-β)-regulated miRNA played a pivotal role in the development of cardiac hypertrophy and heart failure (HF). We observed that miR-27b was upregulated in hearts of cardiomyocyte-specific Smad4 knockout mice, which developed cardiac hypertrophy. In vitro experiments showed that the miR-27b expression could be inhibited by TGF-β1 and that its overexpression promoted hypertrophic cell growth, while the miR-27b suppression led to inhibition of the hypertrophic cell growth caused by phenylephrine (PE) treatment. Furthermore, the analysis of transgenic mice with cardiomyocyte-specific overexpression of miR-27b revealed that miR-27b overexpression was sufficient to induce cardiac hypertrophy and dysfunction. We validated the peroxisome proliferator-activated receptor-γ (PPAR-γ) as a direct target of miR-27b in cardiomyocyte. Consistently, the miR-27b transgenic mice displayed significantly lower levels of PPAR-γ than the control mice. Furthermore, in vivo silencing of miR-27b using a specific antagomir in a pressure-overload-induced mouse model of HF increased cardiac PPAR-γ expression, attenuated cardiac hypertrophy and dysfunction. The re- sults of our study demonstrate that TGF-β1-regulated miR-27b is involved in the regulation of cardiac hypertrophy, and validate miR-27b as an efficient therapeutic target for cardiac diseases. Keywords: microRNA; cardiac hypertrophy; PPAR-γ; transgenic mouse; therapeutic target Cell Research (2012) 22:516-527. doi:10.1038/cr.2011.132; published online 16 August 2011 Introduction Heart failure (HF) is one of the most frequent causes of death worldwide. The underlying causes of HF are diverse, but HF is often associated with cardiac hyper- trophy. Numerous regulatory pathways are implicated in the transduction of hypertrophic signaling [1]. The members of the transforming growth factor-β (TGF-β) superfamily signal through receptor serine/threonine kinases and intracellular Smad proteins [2], and play a Correspondence: Xiao Yang Tel/Fax: +86-10-63895937 E-mail: yangx@nic.bmi.ac.cn Received 13 March 2011; revised 26 May 2011; accepted 13 July 2011; published online 16 August 2011 complex and often contradictory role in the development of cardiac hypertrophy [3]. Although many in vitro and in vivo studies have shown that TGF-β1 overexpression leads to cardiac hypertrophy and HF [4, 5], recent studies have shown that TGF-β signaling may play a role in the protective mechanism in cardiac hypertrophy [6-9]. Our previous study reveals that Smad4 deletion in cardio- myocytes results in cardiac hypertrophy characterized by enlargement of cardiomyocytes, age-associated fibrosis and re-expression of certain fetal genes [6]. Growth dif- ferentiation factor 15 (GDF15), a member of the TGF-β superfamily, antagonizes the hypertrophic response pos- sibly through a mechanism involving the Smad proteins [7, 8]. In addition, cardiac-specific overexpression of bone morphogenetic protein-10 (BMP-10) impairs the postnatal cardiac hypertrophic growth by activation of Cell Research | Vol 22 No 3 | March 2012