Departments of Gastroenterology and Hepatology, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, 325000, China.
Department of Anesthesiology, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou, 325000, China.
Cell Death Dis. 2018 Oct 3;9(10):1014. doi: 10.1038/s41419-018-1068-x.
Activation of hepatic stellate cells (HSCs), a pivotal event in liver fibrosis, is considered as an epithelial-mesenchymal transition (EMT) process. Deregulation of long noncoding RNAs (lncRNAs) has been reported to be involved in a series of human diseases. LncRNA-maternally expressed gene 3 (MEG3) functions as a tumor suppressor in cancers and has been shown to play a vital role in EMT process. However, the biological role of MEG3 in liver fibrosis is largely unknown. In this study, MEG3 was reduced in vivo and in vitro during liver fibrosis. Restoring of MEG3 expression led to the suppression of liver fibrosis, with a reduction in α-SMA and type I collagen. Notably, MEG3 overexpression inhibited HSC activation through EMT, associated with an increase in epithelial markers and a reduction in mesenchymal markers. Further studies showed that Hedgehog (Hh) pathway-mediated EMT process was involved in the effects of MEG3 on HSC activation. Smoothened (SMO) is a member of Hh pathway. Using bioinformatic analysis, an interaction between MEG3 and SMO protein was predicted. This interaction was confirmed by the results of RNA immunoprecipitation and deletion-mapping analysis. Furthermore, MEG3 was confirmed as a target of microRNA-212 (miR-212). miR-212 was partly responsible for the effects of MEG3 on EMT process. Interestingly, MEG3 was also reduced in chronic hepatitis B (CHB) patients with liver fibrosis when compared with healthy controls. MEG3 negatively correlated with fibrosis stage in CHB patients. In conclusion, we demonstrate that MEG3 inhibits Hh-mediated EMT process in liver fibrosis via SMO protein and miR-212.
肝星状细胞（HSCs）的激活是肝纤维化的关键事件，被认为是上皮-间充质转化（EMT）过程。长链非编码 RNA（lncRNA）的失调已被报道参与一系列人类疾病。lncRNA-母源性表达基因 3（MEG3）在癌症中作为肿瘤抑制因子发挥作用，并被证明在 EMT 过程中发挥重要作用。然而，MEG3 在肝纤维化中的生物学作用在很大程度上是未知的。在本研究中，MEG3 在肝纤维化的体内和体外均减少。恢复 MEG3 的表达导致肝纤维化的抑制，α-SMA 和 I 型胶原减少。值得注意的是，MEG3 的过表达通过 EMT 抑制 HSC 激活，与上皮标志物增加和间充质标志物减少有关。进一步的研究表明，Hedgehog（Hh）途径介导的 EMT 过程参与了 MEG3 对 HSC 激活的影响。Smoothened（SMO）是 Hh 途径的成员。通过生物信息学分析，预测了 MEG3 和 SMO 蛋白之间的相互作用。RNA 免疫沉淀和缺失映射分析的结果证实了这种相互作用。此外，MEG3 被证实是 microRNA-212（miR-212）的靶标。miR-212 在一定程度上负责 MEG3 对 EMT 过程的影响。有趣的是，与健康对照组相比，慢性乙型肝炎（CHB）患者肝纤维化时 MEG3 也减少。MEG3 与 CHB 患者的纤维化分期呈负相关。总之，我们证明 MEG3 通过 SMO 蛋白和 miR-212 抑制 Hh 介导的 EMT 过程在肝纤维化中。
