Tenascin is an important component of the glomerular extracellular matrix in normal and pathologic conditions

Tenascin (TN), a large oligomeric glycoprotein, is a recently described component of the extracellular matrix (ECM). Previous reports focusing largely on the role of TN in nephrogenesis have documented the strong expression of TN in embryonic kidney tissue and implied an important role for TN in nephrogenesis. However, the expression of TN in normal and pathologic kidneys in adults has not been systematically evaluated. In this study immunohistochemical staining for TN was applied to 184 renal specimens diagnosed as: normal kidney (23 cases); minimal change disease and its variants (8); mesangial proliferative glomerulonephritis (GN) including IgA nephropathy and mesangial proliferative lupus nephritis (9); endocapillary proliferative GN including membranoproliferative GN, lupus nephritis, and post-infectious GN (25); crescentic GN (11); membranous GN (19); focal segmental sclerosis (15); thrombotic microangiopathy (8); amyloidosis (5); diabetic nephropathy (9); primary tubulointerstitial nephritis (14); transplant rejection (14); and ischemia (24). It was found that: (a) there was unequivocal global diffuse staining limited to the mesangium in normal kidney; (b) regardless of the etiologies and the morphologic types of glomerular disease, whenever there was expansion of the ECM, whether in the mesangial, endocapillary, or extracapillary spaces, there was a concomitant and proportional in situ increase in the TN staining; (c) globally sclerotic glomeruli, regardless of causes, showed diffuse, strong staining, especially in the subcapsular fibrous deposition seen in ischemic sclerosis; (d) non-sclerotic glomeruli showing early ischemic change uniformly displayed a marked decrease or complete loss of staining; (e) in cases of thrombotic microangiopathy, there was segmental or global staining of the capillary wall, probably corresponding to the enlarged lamina rara interna; (f) all nodular lesions in diabetic glomerulosclerosis showed strong staining, but in several of them this staining was much more pronounced in the periphery than in the center of the lesion. Our study proves that TN is probably a component of the normal mesangial matrix, that TN is an ubiquitous component of the expanded glomerular ECM in pathologic conditions regardless of morphologic subtypes, and that further studies on the cell types and mechanisms responsible for TN synthesis may provide a new venue for the understanding of the process of glomerular sclerosis.