Enhancement of toluidine blue staining by transforming growth factor-beta,insulin-like growth factor and growth hormone in the temporomandibular joint of aged mice

Osteoarthritic lesions appear in the articular cartilage of the temporomand ibular joint of mice aged 7 months and older. Reduced rate of proteoglycan (PG) synthesis leading to destruction of the articular cartilage was observ ed in this joint. The purpose of the present study was to test the ability of transforming growth factor-beta 1 (TGF-beta 1), insulin-like growth fact or-1 (IGF-1) and growth hormone (GH) to induce PG synthesis in joint cartil age of aged animals and to compare it with the effect of interleukin-l alph a (IL-l alpha). Mandibular condyle explants from 18-month-old mice were cul tured up to 72 h in serum-free medium, supplemented with I L-l alpha (TGF-b eta 1 (0.1-5.0 ng/ml), TGF-beta 1 (1.0 ng/ml) + IGF-1 (2 ng/ml) or GH (10 n g/ml). The incorporation of S-35-SO4 into sulfated PG was tested. Cartilage samples were processed for histomorphometry using sections stained with 0. 1% toluidine blue (TB), pH 1.8. Results indicated that in cultures suppleme nted (48 h) with either TGF-beta, TGF-beta + IGF-1 or with GH, an increased height and area of TB-positive staining as well as increased incorporation of S-35-SO4 into sulfated PG were observed. In contrast, the cytokine IL-l alpha exerted an inhibitory effect on TB staining and on S-35-SO4 incorpor ation. The present study demonstrated that in vitro supplementation of IL-l alpha to mandibular condyle cartilage reduced the height and area of TB st aining and incorporation of S-35-SO4, whereas TGF-beta 1,TGF-beta 1 + IGF-1 or GH increased the height and a rea of TB staining and increased incorpor ation of S-35-SO4. The two parameters used to identify increased PG synthes is were shown to reveal similar results and were useful for studying the dy namic events taking place in cartilage destruction and repair in osteoarthr itis. Copyright (C) 2000 S. Karger AG. Basel.