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Matrix-associated latent TGF-beta with latent TGF-beta binding protein in the progressive process in
K Tamaki1, S Okuda, K Miyazono
1Second Department of Internal Medicine, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
Background:
A progressive increase in latent transforming growth factor-beta (TGF-beta) secretion from diseased tissue was revealed in our previous work using adriamycin (ADR)-nephropathy (Kidney Int 45:525-36, 1994). Latent TGF-beta is composed of mature TGF-beta and latency-associated peptide (LAP) with or without latent TGF-beta-binding protein (LTBP). LTBP has been reported to contribute to either matrix-association or activation of latent TGF-beta. LTBP also seems to play a key role in the renal lesions of this model. The present study was designed to show the secretion of latent TGF-beta with LTBP and the location of LTBP in renal tissue in ADR-nephropathy.
Experimental Design:
The renal cortical tissue specimens were sampled at Weeks 4, 8, and 16 after the injection of ADR or saline (control) for cortical tissue culture and immunohistology. TGF-beta in the conditioned medium was assayed by immunoprecipitation and bioassay using mink lung epithelial cells. An immunohistochemical study was performed to examine the localization of LTBP, ED-1-positive macrophages, and extracellular matrix proteins including laminin, fibronectin, and collagen type I and type III.
Results:
A TGF-beta bioassay revealed a progressive increase in latent TGF-beta secretion from the cortex of diseased kidney. Free LTBP and LTBP-LAP complex with mature TGF-beta were immunoprecipitated by anti-LTBP Ab from the cortical culture medium. An immunohistochemical study using anti-LTBP Ab demonstrated that LTBP localization was restricted to the glomeruli and the arterioles in the control cortex. In the ADR rats at Week 4, a faint deposition of LTBP was observed in the interstitium around the glomeruli. At Week 8 or 16, LTBP was accumulated in the sclerosing glomeruli or fibrous interstitium, where ECM proteins and infiltrating ED-1-positive macrophages were intensely located.
Conclusions:
Our results indicated that latent TGF-beta with LTBP was localized in association with the extracellular matrix in the sclerotic and fibrotic tissue in this model. Matrix-associated latent TGF-beta with LTBP may thus play an important role in the progressive process of glomerulosclerosis and interstitial fibrosis in ADR-nephropathy.