The glomerular distribution of laminin and fibronectin in glomerulonephritis

Abstract

Laminin (LAM) and fibronectin (FI) are regarded as major components of the glomerular extracellular matrix The aim of this study was to define the distribution of LAM and F1 in primary glomerulonephritis (GN) and GN of systemic lupus erythematosus (SLE) and to correlate the type of glomerular disorders with possible changes in the expression of these components. Normal portions of kidney tissue from 10 patients with renal tumors and sixty-six renal biopsies obtained from patients with GN were studied by the immunoperoxidase- antiperoxidase (PAP) method for the detection of LAM and FI. Twelve patients had membranous GN (MGN), 8 mesangiocapillary GN (MCGN), 2 1 mesangioproliferative GN (MPGN), including I l cases of IgA nephropathy, 11 focal segmental glomerulosclerosis (FSGS) and 14 had SLE. In MGN, LAM was detected more intensely than F1 along the glomerular basement membranes (GBM), in subepithelial GBM protrusions and in the newly-formed GBM. On the contrary, F1 was intensely expressed in the mesangium. LAM and FI expression was pronounced in stages I1 and 111 of MGN. In MCGN, LAM and F1 were diffusely expressed along the GBM and in the mesangium. The distribution of the two antigens in MPGN and FSGS was similar to that seen in normal glomeruli. However, the F1 staining reaction was more intense in severe mesangioproliferative lesions, mainly observed in the cases of IgA-nephropathy, There were no differences in the distribution of LAM and F1 between primary and SLE GN. The antigen staining pattern was pronounced in the membranous and mesangiocapillary lesions of SLE GN. The crescents observed in 7 cases contained increased amounts of both LAM and FI, while the adhesions with Bowman's capsule seen in 9 cases demonstrated increased amounts of LAM. In contrast, the large adhesions observed in 2 cases and the sclerotic lesions in 4 cases contained only small amounts of LAM. Offprint requests to: Dr. Lydia Nakopoulou. Department of Pathology. Medical School, University of Athens, 138-140 Grigoriou Afxediou, Alhens 15772, Greece In conclusion, the increased LAM and F1 glomerular expression mainly in MGN and MCGN, and the F1 overexpression in severe mesangioproliferative lesions of IgA nephropathy suggest that the disturbance of extracellular glomerular matrix is probably due to the damage of glomerular cells or the involvement of the above components in immune-complex formation.