IgA肾病中足细胞损伤及其与蛋白尿的关系

目的 观察 IgA肾病（IgAN）患者足细胞损伤的各种表现，探讨其与蛋白尿的关系。 方法 收集35例伴有明显蛋白尿尿蛋白量（24 h）>1.0 g]的IgAN患者肾活检组织作研究；以8例肾错构瘤患者术后切除肾和肾癌患者术后远离癌旁肾组织为正常对照。免疫组化方法观察肾组织细胞周期调节蛋白（p21、p27）、足细胞结构蛋白（nestin）、足细胞数目 （WT1）。用显微切割方法取出肾小球，通过实时定量PCR方法检测整合素（integrin）β1、nephrin和α辅肌动蛋白4（α-actinin 4）水平。电镜观察足细胞超微结构的改变。根据足细胞数目密度(Nv, n×106/μm3)将35例IgAN患者分为足细胞数目减少组（ Nv<52.49×106/μm3，n = 15）和足细胞数目正常组（Nv≥52.49×106/μm3，n = 20）。随访蛋白尿的转归情况，共18个月。 结果 （1）与正常对照组比较，IgAN患者肾小球内个别足细胞重新表达p21，而足细胞p27的表达明显降低（0.71±0.12比0.91±0.07，P < 0.05）。（2）IgAN患者足细胞nestin 蛋白表达比正常对照显著降低（13.40%±0.04%比 17.60%±0.04%，P < 0.05）；肾小球内integrin-β1 mRNA表达显著升高（12.54±5.20比1.02±0.30，P < 0.05），而nephrin及α-actinin4 mRNA无明显改变。（3）电镜下观察到明显的足突融合和足细胞从基底膜脱落。（4）IgAN患者足细胞数目密度比正常对照组显著减少(161.27±225.92比323.22±138.12，P < 0.05)，且与Lee氏分级相关。（5）足细胞数目密度、integrin-β1 mRNA与肾穿刺当时的尿蛋白量（24 h）呈负相关(r = -0.4483、-0.840, 均P < 0.05)。足细胞数目减少组较足细胞数目正常组的蛋白尿下降程度明显减少（P < 0.05）。 结论 伴蛋白尿的IgAN中存在足细胞的损伤，表现为足细胞周期调节蛋白、结构蛋白的改变，足突的融合及足细胞数目的减少，而足细胞损伤及足细胞数目减少会影响蛋白尿的发生和发展。

Podocyte injury and its association with proteinuria in IgA nephropathy

Objective To investigate the injury of podocyte and its association with proteinuria in IgA nephropathy (IgAN). Method Thirty-five patients of IgA nephropathy with proteinuria more than 1.0 g/24 h were enrolled in the study, and eight cases of renal harmatomaeetomy or renal cancinomaectomy were as controls. Cell cycle regulatory proteins (p21, p27), podocyte-associated molecules (integrin-β1, nephrin, α-actinin 4, nestin), foot process width (FPW) and the amount of podocyte were examined by immunohistochemistry and real-time PCR, respectively. Patients were divided into two groups according to podocyte number per volume (Nv): podocytopenia group (n=15, Nv<52.49×106/μm3) and normal number group (n=20, Nv≥52.49× 106/μm3). Proteinuria was followed up for eighteen months. Results Compared with the controls, podocyte p21 was re-expressed, while the expression of p27 was decreased (0.71±0.12 vs 0.91±0.07, P<0.05) in IgAN. The nestin protein level was markedly decreased in IgAN (13.4%± 0.04% vs 17.6%±0.04%, P<0.05). The mRNA expression of integrin-β1 was significantly increased (12.54±5.20 vs 1.02±0.30, P<0.05), while the amount of nephrin, α-actinin4 remained unchanged. Effacement of foot processes and podocyte detachment from the glomerulax basement membrane were observed in some cases. Nv was significantly less than that of controls (161.27± 225.92 vs 323.22±138.12, P<0.05), which was associated with the Lee's grade of IgA nephropathy. The integrin-β1 mRNA expression and Nv were negatively correlated with baseline proteinuria by univariate analysis (r=-0.840, P=0.034; r =-0.4483, P=0.014, respectively). Proteinuria in podocytopenia group was decreased more slowly than that in normal number group. Conclusions Podocyte injury exsists in IgAN with proteinuria, which manifests alterations in cell cycle regulatory protein and some podocyte-associated molecules, as well as foot process effacement and loss of pedocyte. Podocyte injury may be involved in proteinuria by affecting the progression of proteinuria in IgAN.