Changes in collagenases and TGF-beta precede structural alterations in a model of chronic renal fibrosis

Background. To study the role of collagenases and transforming growth facto r-beta (TGF-beta) in the genesis of interstitial fibrosis. we used the mode l of bromoethylamine (BEA)-induced papillary necrosis, which is known to le ad over a period of 1 to 12 months to interstitial fibrosis and renal insuf ficiency. Methods. Rats were injected with BEA, and urine and kidney tissue (cortex a nd medulla) were collected after 1, 2, 3, 7, and 30 days. One kidney was pe rfused and fixed for morphological studies and immunostained for collagen t ype I. III, and IV. The other kidney was used to prepare cortex and medulla extracts for gelatinases (by fluorometric and zymographic techniques). tis sue inhibitors of metalloproteinase-1 (TIMP-1), and TIMP-2 (by enzyme-linke d immunosorbent assay, ELISA) and TGF-beta 1 (by ELISA). Results. Albuminuria and interstitial fibrosis were present in BEA rats by; day 7, which continued until day 30. Immunocytochemical staining for colla gen types showed that collagen III and IV increased in the interstitium by day 30, but collagen I remained unchanged. Gelatinase activity in the medul la decreased bq 57% compared with control by day 2 and remained low until d ay 30. In the cortex, gelatinase activity remained unchanged between 0 and 7 days after BEA but decreased by 72% by day. 30. TIMP-1 and TIMP-2 were de creased by 80% compared with day 0 in both the medulla (by day 1) and corte x (bq. day 2) and remained low up to day 30. TGF-beta 1 immunoreactivity in creased progressively until day 2 in the medulla (16-fold higher than contr ol) and day 3 in the cortex (S-fold higher than control) and returned to co ntrol level by day 3 in the medulla and by day 30 in the cortex. Two days a fter BEA injection. the mRNA for TGF-beta 1 was increased eightfold in the cortex and 12-fold in the medulla, and it remained high for up to 30 days. Conclusions, The fibrosis that follows papillary necrosis is associated wit h both high TGF-beta 1 expression and depressed gelatinolytic activity.