肾小球壁层上皮细胞参与FSGS足细胞损伤修复的作用机制研究

Focal segmental glomerulosclerosis (FSGS) is the leading cause of nephrotic syndrome in adults. In this disease, the podocyte, a terminally differentiated epithelial cell, is the primary target of injury. The subsequent decrease in podocyte number is a critical determinant underlying the development of glomerulosclerosis. Although FSGS is typically considered a nonimmunological disease, immunosuppressive agents, such as glucocorticoids, are commonly used as first line therapy in clinical disease. In addition to immunomodulatory effects, the therapeutic benefit of glucocorticoids may be in part due to direct cellular actions on podocyte including limiting apoptosis, actin rearrangement, downregulating podocyte cytokines, and enhanced slit diaphragm complex protein synthesis. .Several recent lines of evidence suggest that glomerular parietal epithelial cells (PECs) may serve as progenitor cells for podocytes, and thus may have a potential role in glomerular repair by replacing, in part or completely, any decrease in podocyte number..Others' and our most recent work showed that in mice model of FSGS, prednisone augments glomerular repair by increasing podocyte number through direct effects on PECs. Prednisone limits podocyte loss by increasing its regeneration by augmenting the number of podocyte progenitors along Bowman’s capsule. The data support a direct glomerular cell action for prednisone in improving outcomes in experimental FSGS. Our earlier further experiment confirmed that glucocorticoids receptor exist in PECs. .Taken together, based on our earlier study, to our knowledge, the direct effect of corticosteroids on PECs is not known, nor is it known whether on podocyte regeneration via PECs. The purpose of this study will study the hypothesis that PECs proliferation and development might be affected by GC, and GC might active GR and its following pathway, which taking part in PECs’ pathway of proliferation and differentiation into podocyte. In order to prove this theory, animal study, cell culture and some clinic-pathological analyses will be performed in current project. These researches are expected to provide novel mechanism for PECs on podocyte regeneration in FSGS, and also looking forward to finding new rational for GC therapy in FSGS.

足细胞损伤是局灶节段性肾小球硬化（FSGS）病变形成关键因素。资料表明，糖皮质激素（GC）是治疗FSGS的一线药，有直接的足细胞保护作用；但是，足细胞损伤后的再生修复机制并不清楚。近来，研究表明，肾小球壁层上皮细胞（PEC）可作为足细胞的祖细胞（progenitor cell）参与其损伤修复。我们前期基础研究显示，糖皮质激素（GC）可促进PEC向足细胞转分化，促进其数目增加，达到再生修复目的。预实验提示，PEC存在GC受体（GR）。因此，我们提出假设，FSGS中PEC可以向足细胞转分化，参与其再生修复，多种细胞增殖、分化信号通路参与其中；GC可能通过激活PEC上的GR相关通路而发挥作用。课题将采用临床病理分析、动物和细胞学试验，研究PEC转分化过程中的机制，以及GC对该再生过程的影响。课题的开展对足细胞再生修复机制研究和寻找FSGS新的治疗靶点均有重要科学意义。

足细胞损伤是局灶节段性肾小球硬化症（FSGS）病变形成的关键因素。糖皮质激素（GC）是治疗FSGS的一线用药，除免疫抑制作用外，还有直接的足细胞保护作用；但是，足细胞损伤后的再生修复机制并不清楚。近来，研究表明，肾小球壁层上皮细胞（PEC）可作为足细胞的祖细胞（progenitor cell）参与其损伤修复。课题组初衷围绕GC可促进PEC向足细胞转分化，达到再生修复目的这一关键科学问题，研究探索FSGS中PEC可以向足细胞转分化的过程，以及参与其再生修复的多种细胞增殖、分化信号通路。课题组原计划采用临床病理分析、动物和细胞学试验，研究PEC转分化过程中的机制，以及GC对该再生过程的影响。.课题组遵照研究计划书，第一，完成了FSGS患者组织病理中肾小球PEC数目变化情况分析，并研究了PEC数目在疾病中的差异性和FSGS不同预后转归中的差异性。第二，初步分离了小鼠原代PEC细胞，然而，并未在本实验室成功构建永生化的小鼠PEC细胞系。第三，首先观察了急性肾小管间质损伤模型中肾小球PEC的变化，以及球内和近段肾小管祖细胞的表达，并分析研究了此类细胞参与肾小球纤维化病变的可能机制；其次，观察了人类抗GBM肾炎中PEC上糖皮质激素受体的表达，以及该受体表达与PEC数量、转分化程度以及新月体形成之间的关系。研究尚未对已经构建的FSGS动物模型进行干预试验，观察PEC的转分化和可能信号通路情况。第四，由于未构建永生化的细胞系，因此，细胞学试验尚未完成。此外，由于肾小球PEC细胞可能作为祖细胞，参与肾小球损伤的再生、修复研究，这属于肾脏病基础研究领域的前沿科学问题，很多研究方法、理论尚不成熟，我们在本课题研究过程中，对相关科学问题进行了多次文献复习，并做相关综述发表。.除此以外，我们还基于本课题研究和本领域研究的发展趋势，利用本基金进行了一些新探索，主要包括糖皮质激素对PECs参与的新月体肾炎的疗效机制这一临床上的基本问题。我们发现PECs参与抗GBM新月体肾炎的发展，明确了糖皮质激素能显著抑制PECs的增殖从而减缓新月体形成。我们发现激素能完全抑制新月体肾炎发生中的一个关键信号，即足细胞内激活的EGFR-JAK2-STAT3信号，从而阻止足细胞分泌的某种促PECs增殖的因子。