Intra-renal and urinary RNA expression of podcyte-associated molecules in patients with IgA nephropathy

Background Podocyte injury probably plays important roles in the pathogenesis of IgA nephropathy (IgAN). We studied intra-renal and urinary messenger RNA (mRNA) expression of podocyte-associated molecules in patients with IgAN. Methods We studied 43 consecutive patients with biopsy-proven IgAN. Intra-renal and urinary expression of mRNAs was determined and compared to that of 20 patients with nephrectomy for kidney cancer and 12 normal subjects. Results Intra-renal mRNA expression levels of nephrin, podocin and synaptopodin were significantly lower in patients with IgAN than that of controls. In contrast, their urinary mRNA expression levels were similar. Intra-renal gene expression of nephrin inversely correlated with proteinuria (r = –0.620, P < 0.001), GFR (r = 0.538, P < 0.001), and the degree of tubulointerstitial scarring (r = –0.423, P = 0.013). After followed for an average of 33.4  12.6 months, intra-renal nephrin expression significantly correlated with the rate of GFR decline (r = 0.324, P = 0.041). Conclusions Intra-renal mRNA expression of podocyte associated molecules was down-regulated in patients with IgAN, and the degree of downregulation of nephrin correlated with disease severity and the rate of progression. Our result supports the hypothesis that podocyte injury is an important component in the pathophysiology of IgAN.