Urine transforming growth factor-beta activity is related to the degree of scarring in crescentic nephritis in the rabbit.

Crescentic nephritis was induced in rabbits by injection of antirabbit glomerular basement membrane (GBM) antibodies. Urine samples were obtained by catheterization and assayed for transforming growth factor-beta (TGF-beta) activity. On day 31, all animals were sacrificed for evaluation of renal cortical histopathology and collagen content. The results show that control rabbit urine contains measurable amounts of TGF-beta. Urine TGF-beta activity was expressed in relation to urine creatinine concentration to correct for variation in urine concentration. When expressed in this manner, urine TGF-beta activity increased from day 2 onwards, peaked on day 7 and returned to normal levels after day 14. This time course is identical to that previously seen for the cortical and glomerular production of TGF-beta in the same model. Furthermore, when the normalized TGF-beta values for each animal were compared to their respective fibrosis parameters on day 31, significant correlations were observed for the values of urine TGF-beta activities on day 7 and all indices of fibrosis. These results suggest that measurements of urine TGF-beta activity at certain critical stages of disease could be useful in predicting the progression to end-stage renal disease with fibrosis and might serve as a helpful noninvasive adjunct in monitoring response to therapy.