Role of the interaction of slit membrane, podocyte and glomerular basement membrane in pathogenesis of glomerular kidney diseases such as Alport's syndrome

肾小球滤过屏障如IV型胶原蛋白（COL 4A 3/4/5，肾小球基底膜）或podocin（Nphs 2，裂隙隔膜）中的突变导致蛋白尿、肾纤维化和终末期肾病的早期开始。杂合子COL 4A 3/4突变携带者在以后的生活中发展为薄基底膜肾病，仅伴有血尿。最近，青少年已被描述发展早期蛋白尿和肾功能衰竭，只有杂合子胶原IV型突变。在这些患者中发现了额外的podocin-polymorphism. In该项目中，计划在双杂合子COL 4A 3 +/-//Nphs 2 +/R140 Q-小鼠的帮助下研究可能的发病相关性。我们假设肾小球基底膜（GBM）和裂膈（SD）之间存在通过足细胞受体的相互作用。这种联系对于过滤屏障的稳态和稳定性至关重要。我们希望关注修饰基因（如podocin）对发展TBMN的COL 4A 3小鼠的影响。我们的第一个结果显示，早期蛋白尿以及病理足细胞足突消失，在这些小鼠。具体而言，我们希望重点关注超滤对COL 4A 3 +/-//Nphs 2 +/R140 Q-小鼠单肾切除术所致肾纤维化发展的影响。此外，还将研究单肾切除术后蛋白尿前和蛋白尿期间ACE抑制剂治疗的效果。这些问题应根据临床参数进行研究，如生存时间至肾衰竭作为主要终点，蛋白尿/白蛋白尿的发展，以及肾脏的组织学和超微结构分析。此外，将通过免疫组织化学、实时PCR和Western印迹在体内和体外研究GBM、SD组合物及其受体的描述。这也将研究与我们完善的超微结构免疫金组织化学在不同的疾病阶段。我们的GBM和SD研究结果的第一个结果表明，双杂合子小鼠引起足细胞，其GBM和SD之间的联系，以及它们的稳态的基本机制的重要见解。本课题对Alport综合征、局灶节段性肾小球硬化等人类疾病的治疗具有重要的临床参考价值。预期的结果也可以为更常见的肾脏疾病如糖尿病肾病或肾小球肾炎的治疗选择提供新的基本理解。

Mutations in the glomerular filtration barrier like collagen type IV (COL4A3/4/5, glomerular basement membrane) or podocin (Nphs2, slit diaphragm) lead to an early begin of proteinuria, kidney fibrosis and end-stage-renal disease. Heterozygous COL4A3/4-mutation-carriers develop a thin basement membrane nephropathy with only hematuria later in life. Recently, adolescents have been described developing early proteinuria and kidney failure with only heterozygous collagen type IV-mutations. In these patients additional podocin-polymorphism were found. In this project, a possible pathogenetic correlation is planned to be investigated with help of double-heterozygous COL4A3+/-//Nphs2+/R140Q-mice. We hypothesize that between the glomerular basement membrane (GBM) and slit diaphragm (SD) an interaction exists via the podocytes' receptors. This link is essential for homeostasis and stability of the filtration barrier. We want to focus on the influence of a modifier-gene, like podocin, on the COL4A3-mice who develop TBMN. Our first results show an early proteinuria as well as pathological podocyte foot process effacement in these mice. Specifically, we want to focus on the influence of hyperfiltration on kidney fibrosis development due to uninephrectomy in COL4A3+/-//Nphs2+/R140Q-mice. Furthermore, the effect of ACE-inhibitor therapy after uninephrectomy before and during proteinuria will be investigated. These questions shall be studied on clinical parameters like survival time till kidney failure as primary end point, development of proteinuria/albuminuria, as well as histological and ultrastructural analysis of the kidneys. Furthermore, description of the GBM-, SD-composition and their receptors will be studied, in vivo and in vitro by immunohistochemistry, real-time PCR and Western Blot. This will also be studied with our well-established ultrastructural immunogoldhistochemistry during different disease stages. Our first results of the GBM- and SD-findings demonstrate that the double-heterozygous mice give rise to important insights in basic mechanisms of the link between podocyte, its GBM and SD, as well as their homeostasis. Our project has a significant clinical reference for human diseases like Alport Syndrome and focal segmental glomerulosclerosis. The expected results could also offer a new basic understanding for treatment options of more frequent kidney diseases like diabetic nephropathy or glomerulonephritis.