Abnormal distribution of laminin α2 chain in renal tissues of patients with Alport syndrome

Objective To identify the distribution of the laminin α5,α2 and γ1 chains within renal basement membrane in Alport syndrome (AS). Methods Kidney tissues from 11 patients of AS, 9 IgA nephropathy (IgAN) , 6 focal segmental glomerular sclerosis (FSGS) , 5 thin basement membrane disease (TBMD), 6 minor change glomerulonephritis and 3 normal people were examined by immunofluorescence and confocal microscopy for the expression of laminin α5,α2 and γ1 chains. Among 11 Alport patients, 8 male and 2 female patients inherited as X-linked dominant trait and 1 female inherited as dominant trait. The expression of the α3,5 chains of type IV collagen in GBM were co-absent in all 8 male Alport patients and were partially absent in 2 female patients, whereas their expression were normal in another female patient. Results Laminin α2 chain was deposited in the mesangium and absent from GBM in normal people, but was abnormally deposited in Alport GBM. GBM laminin α2 chain deposition was not observed in IgAN, FSGS, TBMD and minor change glomerulonephritis. As in normal kidney, Alport kidney revealed similar staining for the laminin α5 and γ1 chains. Conclusions Laminin is one of the main components in GBM and mesangium. Abnormal deposidon of laminin α2 chain is of clinical importance in AS diagnosis.