Background: Different mitogens are involved in the pathogenesis of kidney damage after subtotal nephrectomy. One of them, TGF-beta, controls mesangial cell proliferation and interstitial fibrosclerosis. The transduction of the TGF-beta signal is controlled by intracellular signalling molecules such as Ras G monomeric proteins. Renal damage after subtotal nephrectomy (5/6 Nx) can be prevented by heparins, but so far no immunohistochemical correlation between TGF-beta, TGF-beta induced matrix molecules and Rho proteins has been investigated. Since the Ras transduction pathway has recently been associated with progression of renal damage, we evaluated the effect of heparan sulphate (HS) on the expression of TGF-beta, laminin, fibronectin and a Ras protein, RhoA, in the rat remnant kidney model.
Methods: The immunoperoxidase technique was employed to reveal the antigens on 18 remnant kidneys from 5/6 nephrectomized rats, nine untreated and nine treated with oral HS, and on seven normal kidneys from sham-operated rats. Data were semiquantitatively analyzed by an image analyzer (Quantimet, Leica).
Results: The expression of the antigens was significantly higher in the remnant kidneys than in normals. The high TGF-beta, laminin, fibronectin and RhoA expression observed in subtotally nephrectomized rats suggests a role for these molecules in the pathogenesis of progressive renal damage. However, apart from RhoA, HS-treated rats had significantly lower levels of the antigens than the untreated rats.
Conclusions: HS treatment is associated with significantly lower renal expression of TGF-beta, laminin and fibronectin, but not of RhoA. This suggests that the renal-protective effect of HS may be obtained by modulating the TGF-beta pathway, independently of RhoA-mediated transduction.