Connexin43对肥胖相关性肾病足细胞损伤的保护作用机制

Podocyte injury is the major cause of microalbuminuria in the early stage of childhood obesity-related glomerulopathy (ORG), therefore, it is a new direction in ORG treatment to explore an effective way for podocyte injury. Previous studies indicate that the major gap junction protein expressed on podocyte is connexin43, some recent studies conducted on heart, brain, liver and retina show subthreshold injury can promote the expression of connexin43 that increase cellular resistance to subsequent more severe injury. At present, it is well known that obesity is a low-grade chronic metabolic inflammation pathological state, therefore, we hypothesized that the metabolic inflammation may induce upregulation of the expression of connexin43 on podocyte that increase podocyte resistance to subsequent more severe metabolic disorders.This study intends to establish obesity-related glomerulonopathy model using young Sprague-Dawley rats and then observes the changes of connexin43 expression on the podocytes. Next, in vivo, RNAi-mediated silencing of the connexin43 gene in kidney of the ORG model is established, and the change of the morphology and function of podocytes in the model will be compared with that in wild-type rats. In vitro, connexin43 gene silencing podocyte model is established, and the function of podocytes in the model will be evaluated by scrape-loading dye transfer assay and permeability assay, and then compared with that in wild-type podocytes. The aim of this study is to investigate the protective effect of upregulation of connexin43 expression on podocyte for obesity-related glomerulopathy.

足细胞损伤是儿童肥胖相关性肾病早期微量蛋白尿形成的主要原因，因此，探索有效方法治疗足细胞损伤已成为肥胖相关性肾病治疗研究的新方向。Connexin43是足细胞间主要分布的缝隙连接蛋白。最近在心、脑、肝及视网膜中进行的研究发现，低强度的损伤可诱导Connexin43表达上调并对相应组织起到保护作用。低度代谢性炎症反应常伴随肥胖，推测其可能诱导足细胞表面的Connexin43表达上调，对足细胞起到保护作用。本项目拟以幼年SD大鼠为研究对象，建立肥胖相关性肾病模型，观察Connexin43在足细胞的表达变化，进一步通过比较野生型大鼠与肾脏Connexin43沉默大鼠以及野生型足细胞与Connexin43沉默足细胞在足细胞形态和功能方面不同，从体内、体外两个方面探索内源性Connexin43表达上调对肥胖相关性肾病足细胞损伤的保护作用，为肥胖相关性肾病早期治疗探索新的方法。

缝隙连接蛋白Connexin43(Cx43)参与了多种肾脏疾病的病理变化过程，并发挥了重要的调控作用，然而目前还不清楚Cx43是否参与调控了肥胖相关性肾病（Obesity-Related Glomerulopathy，ORG）的病理变化过程。本研究项目首先利用高脂喂养建立肥胖相关性肾病大鼠模型，研究了Cx43在肥胖相关性肾病模型肾脏中的表达变化特点。研究结果发现，该动物模型肾脏存在明显的肾脏损伤情况，如：肾脏肥大、肾小球扩张及炎症细胞浸润、足细胞足突出现融合现象、Nephrin表达减少，足细胞数量减少。与之相伴随的是肾小球Cx43表达明显的上调。研究结果提示Cx43参与了肥胖相关性肾病的病理变化过程，其与肾脏炎症细胞浸润有关。进一步的研究通过反义寡核苷酸技术下调Cx43表达后，初步发现ORG小鼠的尿微量白蛋白明显减少，ACR也明显降低。肾脏促炎症因子VCAM1表达明显降低，纤维化因子Fibronectin表达也明显的降低。该结果提示下调Cx43表达对于ORG具有一定的保护作用。进一步更深入的研究将对这一发现进行更全面的证实。在临床研究方面，本项目主要研究了肥胖等因素与儿童过敏性紫癜合并肾脏损伤的关系。采用的研究方法是病例-对照研究。主要的研究结果显示肥胖、起病年龄大于7岁以及持续皮疹是过敏性紫癜合并肾脏损伤的独立危险因素，其中肥胖患儿罹患过敏性紫癜后，出现肾脏损伤的风险是正常体重儿童的4倍。该研究结果明确了肥胖可以增加过敏性紫癜患儿出现肾脏损伤的风险，为实际的临床工作具有一定的指导意义。