长链非编码RNA H19调控组蛋白表观遗传在骨关节炎发生中的功能及分子机制研究

Osteoarthritis (OA) is a common disease with cartilage degradation. At present, there is no effective therapeutic to prevent development and progression of OA. Long noncoding RNAs (lncRNAs) have been considered as novel regulators for gene expression and emerging evidences suggest that they play important roles in regulating cell differentiation and tissue regeneration. H19, a member of lncRNA, is abundantly expressed in normal chondrocytes, and dysregulated in OA cartilage tissues. So H19 may involve in cartilage formation and degradation, but the mechanisms remain unknown. Our preliminary results showed that H19 was downregulated in most cartilage tissues derived from OA patients. In Sprague Dawley (SD) rats OA model, H19 expression was increased at early stage whereas it was decreased at late stage. We also found that H19 overexpression promoted chondrogenesis of mesenchymal stem cells (MSCs) in vitro and in vivo. Furthermore, H3K27me3 and H3K9me3 were also found to be involved in OA progression. In the present proposal, we will further verify the functions of H19 in cartilage degradation and the underlying mechanisms. The aims of the study are: (1) To clarify the correlation between H19 expression and OA in clinical specimens; (2) To investigate the effects of H19 on cartilage degradation in a rat OA model and chondrocyte; (3) To elucidate the epigenetic regulation of H19 during chondrogenesis and OA progression. The current study will address the novel roles of lncRNA H19 in cartilage health and disease, and H19 may be developed as a potential therapeutic target for maintaining cartilage health and OA treatment.

骨性关节炎(Osteoarthritis, OA)是一种常见的软骨退行性疾病，因其发病原因及分子机制仍未完全明确，目前临床上尚无有效的治疗措施。近年来研究火热的长链非编码RNA(lncRNAs)为OA的发病机制提供了新思路。H19是发现较早的一个lncRNA，虽然在肿瘤领域已有大量的报道。但在其他疾病方面研究还不是很多，尤其是在OA的研究中更不多见。只有零星报道称H19在正常的软骨中高表达，在OA软骨中表达失调；并且其表达受炎症因子调控。据此推测H19可能参与调控软骨退行性病变。前期研究表明H19促进骨髓间充质干细胞的体外成软骨分化及体内软骨形成，并且组蛋白甲基化参与此调控过程。本课题拟从细胞、分子、动物、组织上进一步确定H19在OA发病中的生物学功能，并深入探讨其中的分子机制，从而为OA的防治提供一个新的分子靶标。

骨性关节炎(Osteoarthritis，OA)又称退行性骨关节病，其典型的病理改变为关节软骨的进行性退变、降解，同时伴有代偿性的骨质增生、关节边缘出现骨赞、软骨下骨和关节滑膜出现反应性改变[1]。作为一种常见的关节疾病，OA在60岁以上人群中发病率已经超过50%，且出现发病低龄化的趋势，是排在首位的致残性疾病。目前临床上有效的治疗手段并不多，因其发病原因及分子机制仍未完全明确，所以临床上对其治疗只能采取对症处理的治疗方法。因此，对OA发病机制的研究是寻找理想治疗靶标的基础。近年来对lncRNA转录调控作用的研究发现，与OA相关的多种重要蛋白分子的表达均受lncRNA的调控，这就为OA的发病机制提供了新思路，有希望成为OA治疗的新靶标。.EZH2属于polycomb家族，是构成PRC2蛋白复合物中的一个催化亚基，可通过催化组蛋白H3氨基末端的赖氨酸发生三甲基化而抑制基因转录。作为H3K9和H3K27特异性的甲基转移酶，EZH2参与多种生命活动和疾病的发生，例如胚胎发育、细胞分化、肿瘤发生等。近年来，已有大量文献报道H19在多种肿瘤细胞内调控EZH2的表达。例如，H19 通过抑制miR-630的表达来调控鼻咽癌(NPC)细胞中EZH2的表达；H19可招募EZH2从而调控甲状腺肿瘤的迁移及乳腺癌的耐药性。另外，有研究表明H19在心肌细胞内可直接与EZH2结合。.通过前面的论述中我们知道H19参与OA的发病过程，并且可能是通过与EZH2直接结合从而调控组蛋白甲基化。因此本项目中，我们以H19为核心，通过体内体外验证其调控软骨分化及体内软骨形成中的功能，并结合RIP、CHIP等实验证实H19可直接结合EZH2，从而调控组蛋白H3K9和H3K27的三甲基化，而这两个组蛋白可与成软骨的关键转录因子Sox9及OA标志基因col10a1的promoter具有结合能力。因此，本项目的研究结果阐明了H19调控OA发生的一个新机制，从而为OA的治疗提供一个新的思路。

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