Nephrol Dial Transplant (2000) 15: 1956-1964
© 2000 European Renal Association-European Dialysis and Transplant Association
Abnormal expression of glomerular basement membrane laminins in membranous glomerulonephritis
1 INSERM U489, and Departments of 2 Nephrology and 4 Pathology, Paris VI University, Assistance Publique-Hôpitaux de Paris, Paris, France, 3 Present address: Department of Nephrology, University hospital of Strasbourg, Strasbourg, France
Background. Proteinuria associated with glomerular diseases is secondary to alterations of the charge-selective and/or size-selective properties of the glomerular basement membrane (GBM), but molecular alterations that are responsible for these functional changes are still poorly understood. Analysis of mice harbouring a null mutation in the gene encoding the ß2 chain of laminin has suggested that the presence of abnormal laminin chains within the GBM can be responsible for proteinuria.
Methods. We have investigated whether abnormal laminin ß chains could be detected by immunohistochemistry within the GBM of patients with proteinuria and minimal change disease (five patients), focal and segmental glomerulosclerosis (five patients), or primary membranous glomerulonephritis (10 patients). Three patients with mesangiocapillary glomerulonephritis and three patients with IgA nephropathy were also studied as controls.
Results. We showed that the GBM of all 10 patients with membranous glomerulonephritis, but not of patients with other glomerulopathies, contained laminin ß1, which is normally expressed only during metanephros development. The re-expression of the ß1 chain of laminin was not associated with that of the embryonic
1 chain of type IV collagen, or with the loss of expression of vimentin and synaptopodin, two markers of differentiated podocytes.
Conclusions. The presence of new laminin isoforms within the GBM of patients with membranous glomerulonephritis could play a role in the occurrence of proteinuria, by modifying either the sieving properties of the GBM or the interactions between podocytes and the GBM.
Keywords: glomerular basement membrane; laminin; membranous glomerulonephritis
Correspondence and offprint requests to: Jérôme Rossert, INSERM U489 and Department of Nephrology, Tenon hospital, 4 rue de la Chine, F-75020 Paris, France.