Institute of Human Anatomy and Embryology, University of Regensburg, Germany.
Histochem Cell Biol. 2011 Sep;136(3):301-19. doi: 10.1007/s00418-011-0844-9. Epub 2011 Aug 4.
Structural changes of podocytes and retraction of their foot processes are a critical factor in the pathogenesis of minimal change nephritis and glomerulosclerosis. Here we tested, if connective tissue growth factor (CTGF) is involved in podocyte injury during acute and chronic puromycin aminonucleoside nephrosis (PAN) as animal models of minimal change nephritis, and focal segmental glomerulosclerosis, respectively. Rats were treated once (acute PAN) or for 13 weeks (chronic PAN). In both experimental conditions, CTGF and its mRNA were found to be highly upregulated in podocytes. The upregulation correlated with onset and duration of proteinuria in acute PAN, and glomerulosclerosis and high expression of glomerular fibronectin, and collagens I, III, and IV in chronic PAN. In vitro, treatment of podocytes with recombinant CTGF increased amount and density of actin stress fibers, the expression of actin-associated molecules such as podocalyxin, synaptopodin, ezrin, and actinin-4, and activation of focal adhesion kinase (FAK) and extracellular signal-regulated kinase (ERK). Moreover, we observed increased podocyte expression of mRNA for transforming growth factor (TGF)-β2, TGF-β receptor II, fibronectin, and collagens I, III, and IV. Treatment of cultured podocytes with puromycin aminonucleoside resulted in loss of actin stress fibers and cell death, effects that were partially prevented when CTGF was added to the culture medium. Depletion of CTGF mRNA in cultured podocytes by RNA interference reduced both the number of actin stress fibers and the expression of actin-associated molecules. We propose that the expression of CTGF is acutely upregulated in podocytes as part of a cellular attempt to repair structural changes of the actin cytoskeleton. When the damaging effects on podocyte structure and function persist chronically, continuous CTGF expression in podocytes is a critical factor that promotes progressive accumulation of glomerular extracellular matrix and glomerulosclerosis.
足细胞的结构变化和足突回缩是微小病变性肾炎和肾小球硬化发病机制中的一个关键因素。在这里，我们检测了结缔组织生长因子 (CTGF) 是否参与了嘌呤霉素氨基核苷肾病 (PAN) 的急性和慢性阶段，作为微小病变性肾炎和局灶节段性肾小球硬化的动物模型。大鼠接受一次性 (急性 PAN) 或 13 周 (慢性 PAN) 治疗。在这两种实验条件下，CTGF 及其 mRNA 在足细胞中均高度上调。这种上调与急性 PAN 中的蛋白尿发作和持续时间、肾小球硬化以及肾小球纤维连接蛋白、胶原 I、III 和 IV 的高表达相关。在体外，用重组 CTGF 处理足细胞会增加肌动蛋白应力纤维的数量和密度，以及肌动蛋白相关分子如足突蛋白、突触蛋白、埃兹蛋白和肌动蛋白-4 的表达，并激活粘着斑激酶 (FAK) 和细胞外信号调节激酶 (ERK)。此外，我们观察到转化生长因子 (TGF)-β2、TGF-β 受体 II、纤维连接蛋白和胶原 I、III 和 IV 的 mRNA 在足细胞中的表达增加。嘌呤霉素氨基核苷处理培养的足细胞会导致肌动蛋白应力纤维丢失和细胞死亡，当 CTGF 被添加到培养基中时，这些效应会部分得到预防。用 RNA 干扰耗尽培养的足细胞中的 CTGF mRNA 会减少肌动蛋白应力纤维的数量和肌动蛋白相关分子的表达。我们提出，CTGF 的表达在足细胞中被急性上调，这是细胞试图修复肌动蛋白细胞骨架结构变化的一部分。当对足细胞结构和功能的损伤持续存在时，足细胞中持续的 CTGF 表达是促进肾小球细胞外基质进行性积累和肾小球硬化的一个关键因素。
