Meis1在CKD肾小管间质纤维化中的作用及机制研究

Renal tubular epithelial cell injury and the activation of tubulointerstitial fibroblasts are key pathogenic events in promoting the development and progression of renal fibrosis. Thus, exploration of the endogenous protective factors against renal fibrosis are of importance in finding the novel strategies for CKD therapy. Myeloid ecotropic viral integration site-1 (Meis1) is a cofactor of Hemobox (HOX) gene. It has been shown that Meis1 contributes a series of events of physiology and pathology including the development of embryonic kidney. However, the role of Meis1 in renal fibrosis is still unclear. Our preliminary studies showed that Meis1 was upregulated in the kidney tissues of CKD patients and UUO mice, as well as in the renal tubular cells treated with TGF-β1. Furthermore, we found that overexpression of Meis1 in renal tubular cells significantly attenuated the fibrotic response induced by TGF-β1. These data suggested that Meis1 might play an important role in antagonizing the renal fibrosis during CKD. Due to the property of Meis1 as a transcription factor, we analyzed the potential target genes of Meis1 via bioinformatics and found multiple binding sites in the promoter region of profibrotic gene β-catenin. By overexpression of Meis1, we further observed that β-catenin was downregulated by Meis1 at both mRNA and protein levels, suggesting that transcription factor Meis1 might negatively regulate β-catenin to protect against renal fibrosis in CKD. In this proposal, we will employ the human kidney samples and the models of animals, cells, and molecules to fully investigate the role and mechanism of Meis1 in antagonizing the renal tubulointerstitial fibrosis, which will provide new insights into the prevention and treatment of CKD.

肾脏纤维化是CKD发生发展的关键环节，对其发生机制进行深入研究有助于寻找新的干预靶点。Meis1是同源盒基因的辅因子，参与肿瘤、胚胎发育等病理及生理过程，但Meis1在肾脏纤维化中的作用尚无报道。我们预实验发现，在CKD患者及UUO小鼠肾组织，Meis1的表达均显著上调，在肾小管细胞过表达Meis1可抑制TGF-β诱导的促纤维化效应，提示Meis1可能对肾脏纤维化具有拮抗作用。进一步生物信息学分析发现，促纤维化因子β-catenin的启动子区存在转录因子Meis1的结合位点，在小管上皮细胞过表达Meis1下调了β-catenin的mRNA及蛋白表达，提示Meis1可能负性调控β-catenin的表达。因而推测：Meis1可以通过负性调控β-catenin来拮抗肾脏纤维化。本项目将在整体、细胞及分子层面探讨Meis1拮抗肾间质纤维化的作用和机制，为防治CKD提供新视角。

肾间质纤维化(renal interstitial fibrosis，RIF)是多种慢性肾脏病（CKD）发展到终末期肾病（ESRD）的共同病理途径。近年研究显示，肾脏小管间质成纤维细胞活化及小管上皮细胞损伤均是导致肾脏纤维化的关键因素。但具体机制仍不十分清楚。髓细胞异位病毒整合位点-1（myeloid ecotropic viral integration site-1，Meis1）属于三氨基酸环延伸（TALE）同源域转录因子家族，本质上是一种转录因子，通过直接调控下游基因的转录水平，参与多种细胞生理及病理生理功能。但其在慢性肾脏病及纤维化中的作用暂无研究。我们在临床CKD患者的肾组织以及单侧输尿管梗阻（UUO）诱导的肾小管间质纤维化的小鼠肾组织中发现Meis1表达显著上调。TGF-β1刺激体外培养的小鼠近端小管上皮细胞，同样观察到Meis1表达水平明显上调。而在成纤维细胞及近端小管上皮细胞中过表达Meis1则明显减轻了TGF-β1诱导的细胞外基质成分FN、Collagen-III的表达水平，成纤维细胞活化指标α-SMA的表达及炎症因子表达水平。在体内使用Meis1基因肾小管上皮及成纤维细胞特异性过表达小鼠，制备UUO, 单侧IR及叶酸模型，结果发现，与野生型小鼠相比过表达Meis1显著改善了各类损伤诱导的间质纤维化，包括细胞外基质成分沉积减轻，成纤维细胞活化水平改善及炎症因子表达水平下降。在机制上，本课题组利用成纤维细胞Meis1 cKI 小鼠构建UUO 7d 模型后取肾皮质送RNA测序。通过荧光素酶报告基因实验及ChIP实验最终筛出Ptprj（蛋白质酪氨酸磷酸酶，受体J型）可能是Meis1的下游调控靶点。因此我们在成纤维细胞中过表达Ptprj发现，其显著减弱了TGF-β1诱导的细胞外基质分泌，而在野生型小鼠中用尾静脉高压注射Ptprj过表达质粒也发现，过表达Ptprj后显著改善了UUO诱导的小鼠肾脏纤维化损伤。上述结果提示，Meis1很有可能通过转录激活Ptprj，促使其表达升高，从而减轻UUO诱导的损伤小鼠肾脏纤维化损伤。