Glomerular Expression of α2(IV) and α5(IV) Chains of Type IV Collagen in Patients with IgA Nephropathy

Abstract

IgA nephropathy (IgAN) frequently accompanies glomerular basement membrane (GBM) alterations. To clarify the compositional changes of the GBM in IgAN, we examined the glomerular expression of α2(IV) and α5(IV) chains of type IV collagen in 36 patients with IgAN. Increased expression of the α2(IV) chain was observed in the expanded mesangium, and there were segmental sclerotic lesions of glomeruli in which the expression of the α5(IV) chain in the GBM was reduced. These lesions were found in 11 out of the 36 patients (30.6%). The patients with these lesions had more proteinuria, lower creatinine clearance and severer histological changes than the patients without them. On the other hand, a partial reduction of α5(IV) chain in normal-appearing GBM was observed in 15 out of the 36 patients (41.7%). The patients with this lesion had a longer disease period before biopsy than the patients without it. No other clinical and histological parameters were related to the partial reduction of α5(IV) in the GBM. In conclusion, an imbalance of glomerular α2(IV) and α5(IV) chain expression occurred in IgAN. This may be associated with the morphological changes of glomerular sclerosis and GBM alterations in IgAN. Further studies are required to understand the pathogenesis of the abnormal expression of type IV collagen chains.