Expression of alpha5beta1 and alpha6beta1 integrins in IgA nephropathy (IgAN) with mild and severe proteinuria. An immunohistochemical study.

Immunoperoxidase staining was carried out using monoclonal antibodies against integrin alpha5beta1 and integrin alpha6beta1 on renal biopsy specimens from patients with IgA nephropathy with mild proteinuria (n = 15) and with severe proteinuria (n = 10). Our study revealed increase in glomerular immunoexpression of alpha5beta1 in renal biopsies in IgA nephropathy with severe proteinuria. There were no statistical differences between interstitial alpha5beta1 immunostaining, as well as tubular alpha6beta1 immunoexpression in renal tissue between patients with mild and severe proteinuria. The intensity of interstitial alpha5beta1 integrin immunoexpression was positively correlated with the degree of interstitial fibrosis in both studied groups, meanwhile the intensity of tubular alpha6beta1 integrin immunoexpression was not related to the degree of renal interstitial fibrosis in patients with mild and severe proteinuria. Our results suggest that elevated immunoexpression of alpha5beta1 integrin on endothelial glomerular cells in the renal tissue in patients with severe proteinuria may point to the role of this integrin in the mechanism of glomerular injury in these cases of IgA nephropathy. The positive association between the interstitial expression of alpha5beta1 integrin and the relative interstitial cortical volume in renal biopsies in patients with mild and severe proteinuria suggests that alpha5beta1 integrin may play a role in the pathogenesis of chronic progressive renal disease in both studied group. Lack of positive correlation between tubular alpha6beta1 integrin immunoexpression and the relative interstitial cortical volumen may indicate that this molecule play no role in the pathomechanism of interstitial fibrosis in IgA nephropathy with mild and severe proteinuria.