Background: In this study, we attempted to determine whether heparin-binding epidermal growth factor-like growth factor (HB-EGF) was up-regulated in two chronic models of proteinuria.
Methods: Chronic passive Heymann nephritis (PHN) and puromycin aminonucleoside (PAN) models were induced in Sprague-Dawley rats. HB-EGF expression was studied by Northern blotting, in situ hybridization, and immunohistochemistry.
Results: The chronic PAN model was associated with the development of glomerular lesions of focal glomerular sclerosis (FGS), severe interstitial fibrosis, and renal failure. Lesions of FGS were seen in approximately 80% of glomeruli at all time points, with a slight increase in the number of glomeruli showing extensive adhesion between 40 and 90 days. Northern blots of whole kidney tissue showed a 3- to 5.8-fold increased expression of HB-EGF mRNA in the chronic PAN group. Increased mRNA and protein were localized by in situ hybridization and immunohistochemistry to tubules, glomerular epithelial cells (GECs), and cells of Bowman's capsule. HB-EGF mRNA and protein were strongly expressed by epithelial cells involved in the formation of the lesions of FGS. By contrast, in chronic PHN, there was a small increase in HB-EGF, and the extensive lesions of FGS did not develop despite continued, heavy proteinuria.
Conclusions: These data suggest that HB-EGF may contribute to formation of the lesions of FGS, perhaps through stimulation of abortive mitogenesis in GECs or an adhesive interaction between transmembrane HB-EGF and the exposed glomerular basement membrane.