Complement C3 is Essential for Development of Kidney Cysts in ADPKD Mice

描述（由申请人提供）：本提案旨在确定补体C3是否需要用于小鼠Pkd1失活诱导的肾囊肿的发展和进行性扩张。作为最常见的遗传性疾病，常染色体显性多囊肾病（ADPKD）影响约1 / 400至1000活产婴儿。约85%的ADPKD是由PKD1基因突变引起的，其余15%是由PKD2基因突变引起的。它是大量囊肿的逐渐扩张和增大，破坏正常肾脏结构，损害肾脏功能并引起临床症状。还有其他因素控制着ADPKD的发病和严重程度，尤其是肾囊肿的侵袭性进展。肾囊肿的扩大是一个缓慢的炎症过程。细胞因子、生长因子和其他炎症介质参与其中，但确切的机制和关键介质尚不清楚。我们发现补体C3在小鼠和人AKPKD肾脏和囊液中升高和活化。补体C3的局部浓度和活化可能参与肾囊肿的发展和扩大。根据文献，补体C3是PKD小鼠模型肾组织中最易诱导的基因之一。它也存在于人类ADPKD的囊液和肾组织中并高度表达。因此，为了进一步确定补体C3在体内肾囊肿发育和侵袭性扩大中的重要作用，我们将产生C3基因缺失的双敲除小鼠（Mx1Cre+Pkd1flox/flox C3-/-），通过将条件ADPKD小鼠（Mx1Cre+Pkd1flox/flox）与C3敲除小鼠（C3-/-）杂交，也可以有条件地敲除Pkd1。我们将开展多项实验来研究补体C3如何促进侵袭性囊性发育，包括产生局部增加C3的细胞类型，活化和裂解C3片段导致局灶性炎症和囊性扩张的作用，以及C3在囊性肾中的激活机制（Aim 1）。在小鼠模型中，我们预计补体C3基因的缺失可以阻断或延缓Pkd1失活诱导的肾囊肿的发生和进展（Aim 2）。大约一半的ADPKD患者在60岁时进展为慢性肾衰竭。目前对这种疾病的治疗是透析或肾脏替代疗法。我们提出的研究将为这种最常见的危及生命的遗传疾病揭示一种新的治疗策略。

DESCRIPTION (provided by applicant): This proposal is to determine whether complement C3 is required for development and progressive expansion of kidney cysts induced by Pkd1 inactivation in mice. As the most common inherited disease, autosomal dominant polycystic kidney disease (ADPKD) affects approximately 1 in 400 to 1000 live births. Approximately 85% of ADPKD results from mutation of PKD1, and the remaining 15% are from mutation of PKD2 gene. It is the progressive expansion and enlargement of numerous cysts that destroys normal kidney structure, impairs kidney function and causes clinical symptoms. There are also other factors that control onset and severity of ADPKD, especially aggressive progression of kidney cysts. Enlargement of kidney cysts is a slowly inflammatory process. Cytokines, growth factors and other inflammatory mediators are involved, but the exact mechanism and key mediators remain unclear. We found that complement C3 was elevated and activated in mouse and human AKPKD kidneys and cystic fluid. The local concentration and activation of complement C3 may be involved in development and expansion of kidney cysts. Based on the literature, complement C3 is one of the most highly induced genes in kidney tissue from a PKD mouse model. It is also present and highly expressed in cystic fluid and kidney tissue in human ADPKD. Thus, in order to further determine the essential role of complement C3 in development and aggressive expansion of kidney cysts in vivo, we will generate a double knockout mice (Mx1Cre+Pkd1flox/flox C3-/-) in which the C3 gene is deleted, and Pkd1 can also be conditionally knocked-out by crossing conditional ADPKD mice (Mx1Cre+Pkd1flox/flox) with C3 knockout mice (C3-/-). We will carry out several experiments to investigate how complement C3 promotes the aggressive cystic development, which includes the cell type producing local increased C3, the role of activated and cleaved fragments of C3 leading to focal inflammation and cystic expansion, the mechanism of C3 activation in cystic kidney (Aim 1). In mouse models, we expect that deletion of the complement C3 gene blocks or delays development and progression of kidney cysts induced by Pkd1 inactivation (Aim 2). Approximately one-half of ADPKD patients progress to chronic renal failure by age 60. Current treatment for this disease is dialysis or renal replacement therapy. Our proposed study would reveal a novel therapeutic strategy for this most common life-threatening genetic disease.