[Different expressions of alpha 2 (IV) and alpha 3 (IV) collagen mRNAs in renal glomeruli of IgA nephropathy].

The levels of extracellular matrix protein mRNAs were increased prior to the appearance of histological glomerulosclerosis in isolated glomeruli from several animal models. Striker studied renal biopsies (Seminar in Nephrology, 13:508,1993). We made a comparable study in human renal biopsies to assess the levels of glomerular alpha 2 (IV) and alpha 3 (IV) collagen gene expressions in renal biopsies. Renal biopsy specimens were obtained from 11 patients (7 IgA nephropathy and 4 mesangial proliferative glomerulonephritis). Glomerular lesion was divided into 5 grades. The amount of collagen type IV in glomerular matrix was evaluated by immunoperoxidase staining using a monoclonal antibody to type IV collagen. For gene expression analysis, glomeruli were dissected out from about 10% of each biopsy specimen. The expressions of alpha 2 (IV) and alpha 3 (IV) collagen mRNAs were analyzed by using in situ reverse transcription coupled with polymerase chain reaction. Each PCR reaction contained an amount of cDNA template equivalent to that obtained from 1/10 of a glomerulus, alpha 2 (IV) and alpha 3 (IV) collagen mRNAs were detected in all specimens. All 3 cases of IgAN with grade III glomerular lesion had a more marked increment of glomerular alpha 2 (IV) collagen cDNA than that of the other 3 IgAN patients with grade II lesion (the intensity of PCR product, grade III 0.54 +/- 0.12, VS grade II 0.25 +/- 0.08, P < 0.05). No discrepancies were detected in the level of glomerular alpha 3 (IV) collagen cDNA and the intensity of collagen IV staining between these two groups of IgAN. Interestingly, in MsPGN patients there was no difference in the expression of glomerular alpha 2 (IV) collagen mRNA between grade II and grade III glomerular lesions. The results suggested that the detection of glomerular alpha 2 (IV) collagen mRNA level in IgAN patients may help to define the pathological classification.