Identification of a novel TGF-β-miR-122-fibronectin 1/serum response factor signaling cascade and its implication in hepatic fibrogenesis

// Chunxian Zeng 1,* , Yun-Long Wang 1,* , Chen Xie 2 , Ye Sang 1 , Tuan-Jie Li 2 , Min Zhang 2 , Ruizhi Wang 1 , Qi Zhang 2 , Limin Zheng 1 , Shi-Mei Zhuang 1,2 1 Key Laboratory of Gene Engineering of The Ministry of Education, State Key Laboratory of Biocontrol, Collaborative Innovation Center for Cancer Medicine, School of Life Sciences, Sun Yat-sen University, Guangzhou, P.R. China 2 Key Laboratory of Liver Disease of Guangdong Province, The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, P.R. China * These authors have contributed equally to this work Correspondence to: Shi-Mei Zhuang, email: // Keywords : hepatic fibrosis, noncoding RNA, microRNA, miR-122, fibronectin 1 Received : November 10, 2014 Accepted : February 27, 2015 Published : March 26, 2015 Abstract Transforming growth factor-β (TGF-β) is a potent cytokine that promotes the development of fibrogenic cells, stimulates the expression of fibrosis-related genes, and consequently results in hepatic fibrogenesis. The involvement of miRNAs in this process remains largely unknown. We showed that miR-122 was substantially expressed in hepatic stellate cells (HSCs) and fibroblasts, the major sources of fibrogenic cells in liver tissues. Notably, exposure to TGF-β led to significant downregulation of miR-122. Furthermore, reintroduction of miR-122 suppressed TGF-β-induced expression of fibrosis-related genes, including alpha smooth muscle actin (α-SMA), fibronectin 1 (FN1) and α1 type I collagen (COL1A1), in HSCs and fibroblasts. Subsequent mechanism investigations revealed that miR-122 directly inhibited FN1 expression by binding to its 3’-untranslated region and indirectly reduced the transcription of α-SMA and COL1A1 by inhibiting the expression of serum response factor (SRF), a key transcription factor that mediated the activation of fibrogenic cells. Further in vivo studies disclosed that intravenous injection of miR-122-expressing lentivirus successfully increased miR-122 level and reduced the amount of collagen fibrils, FN1 and SRF in the livers of CCl 4 -treated mice. These findings disclose a novel TGF-β-miR-122-FN1/SRF signaling cascade and its implication in hepatic fibrogenesis, and suggest miR-122 as a promising molecular target for anti-fibrosis therapy.