Cytokines and cell cycle regulation in the fibrous progression of crescentformation in antiglomerular basement membrane nephritis of WKY rats

Cytokines may regulate cell proliferation by cell-cycle-regulatory proteins , in which cyclin-dependent kinase inhibitors (CDKI) inhibit cell prolifera tion. We investigated whether CDKI p21 or p27. both of which are potentiall y regulated by transforming growth factor (TGF)-beta, a key cytokine in fib rogenesis, are involved together with TGF-beta and/or platelet-derived grow th factor (PDGF) in the fibrous progression of glomerular crescent formatio n and examined the sequential change in the cell type and the cellular back ground of myofibroblasts in crescent formation. Crescentic glomerulonephrit is (GN) was induced by i.v. injection of rabbit anti-rat glomerular basemen t membrane antiserum in WKY rats. Animals were killed 1, 2, 3 and 4 weeks a fter the induction of GN, and their kidneys were processed for immunohistoc hemical examination. After 1 week more than 85% of glomeruli showed cellula r crescents, which became fibrocellular with decreased cellularity by 4 wee ks. ED 1-positive macrophages were components of crescent cells in about 44 % at 1-2 weeks, and this proportion declined markedly afterwards. Alpha smo oth muscle actin (alpha SMA, a marker for myofibroblasts)positive cells wer e found in Bowman's epithelial cells (BEP) and in some crescent cells at I week, becoming major components of crescent cells by 4 weeks (about 40%). I t was 2 weeks before invasion of alpha SMA-positive interstitial cells into glomeruli was evident. PDGF-B and PDGF receptor beta -positive cells, indi cating possible targets for PDGF, were found in BEP adjoining crescent form ation almost exclusively from I to 2 weeks. By contrast, both TGF-beta rece ptor types I- and II-positive cells, indicating possible effectors for TGF- beta, were found in BEP and crescent formation, and the percentage of these in the crescent formation did not change until 4 weeks (about 32%). Cells with positive immunostaining for proliferating cell nuclear antigen and cyc lin A, markers for cell proliferation, in the crescent formation peaked in number and proportion at 1-2 weeks, then decreased. In contrast, cells with positive immunostaining for p21 and p27, CDKI, were sparse at 1 week, and then increased markedly in number and in proportion, peaking at 3 (39.6%) o r 2-3 weeks (about 25-30%), respectively. The present study demonstrates th at restrained expression or a transient increase in p21 and p27 may be asso ciated with proliferation or with inhibited proliferation of crescent cells , most of which are macrophages and myofibroblasts. The action of PDGF and TGF-beta may contribute to the recruitment of myofibroblasts into the cresc ent. The action of TGF-beta on crescent cells might be linked to the expres sion of p21 and/or p27.