Podocyte injury and its association with proteinuria in IgA nephropathy / 中华肾脏病杂志

ABSTRACT

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.