circHIPK3竞争性结合miR-338-3p调控HIF-1α在博来霉素诱导肺纤维化中的机制研究

Progression of pulmonary fibrosis is associated with the accumulation of fibroblasts and the process of fibroblast to myofibroblast differentiation (FMD). HIF-1α has been proved to play a key role in connecting the lung injury to its repair. We previously demonstrated that HIF-1α could regulate the epithelial-to-mesenchymal transition in pulmonary fibrosis. In recent studies, functional circRNAs have been shown to participate in the regulatory networks governing cell proliferation at transcriptional and post-transcriptional level. The newest research revealed that fibroblast contains abundant circular RNA (circRNA), circHIPK3, whose role remains unclear. Our previous study demonstrated the elevation of circHIPK3 expression in bleomycin-induced pulmonary fibrosis. We also found the increased circHIPK3 expression in TGF-β1 induced myofibroblast in vitro. Knockout of circHIPK3 gene significantly decreases TGF-β1 induced FMD in vitro. Also, knockout of circHIPK3 gene significantly down-regulates the expression of HIF-1α. Given the importance of circRNA in biological process, we speculate circHIPK3 might be involved in the pathogenesis of pulmonary fibrosis. Bioinformatics analysis found that circHIPK3 might function as competing endogenous RNA to regulate HIF-1α level by sponging miR-338-3p in the process of FMD in pulmonary fibrosis. This project is designed to use both biomolecular techniques and animal models of pulmonary fibrosis(bleomycin-exposed mice) to further explore the mechanism of circHIPK3/miR-338-3p/HIF-1α pathway in regulating FMD process. The results would be verified in clinical samples. The aim of this study is to provide theoretical evidence for targeted therapy in treating pulmonary fibrosis.

成纤维细胞的肌成纤维转化（FMD）是肺纤维化持续进展的重要机制。研究报道HIF-1α是联系肺损伤与修复的关键因子。课题组也证实HIF-1α可通过调控上皮-间质转化参与肺纤维化的发生。最新研究显示，成纤维细胞中富含circRNA，circRNA可参与调控细胞增殖。课题组进一步发现：肌成纤维细胞中circHIPK3异常增高，circHIPK3通过调控HIF-1α介导FMD进程；生物信息学分析发现成纤维细胞中存在circHIPK3/miR-338-3p/HIF-1α调控轴。因此，推测circHIPK3可能通过抑制miR-338-3p，解除miR-338-3p对HIF-1α mRNA的抑制，上调HIF-1α表达，介导肺纤维化FMD过程。本课题拟在细胞及博来霉素诱导的小鼠肺纤维化模型中探讨circHIPK3/miR-338-3p/HIF-1α通路调控FMD进程的机制，为肺纤维化靶向治疗提供理论依据。

肺纤维化进程中，成纤维细胞持续激活并通过肌成纤维细胞转化（fibroblast to myofibroblast transition，FMT）合成分泌大量胶原，造成肺纤维化持续进展。目前探究如何逆转成纤维细胞的FMT成为研究肺纤维化机制的热点问题。环状RNA（circRNA）是许多生物过程重要的参与者。circHIPK3是人类肺中最丰富的环RNA之一。本研究探讨了circHIPK3在肺纤维化中的作用。我们发现，在博莱霉素诱导的肺纤维化小鼠模型及体外诱导的肌成纤维细胞中，circHIPK3表达上调。circHIPK3沉默可在体内外改善FMT并抑制成纤维细胞增殖。机制上，circHIPK3通过充当内源性miR-338-3p海绵来调节FMT，并抑制miR-338-3p活性，从而导致SOX4和COL1A1表达增加。此外，在特发性肺纤维化患者的临床样本中检测到circHIPK3表达失调。circHIPK3的干预可能是肺纤维化的一种有前途的治疗方法。