| Abstract: | Cultured human articular and costal chondrocytes were used as a model system to examine the effects of recombinant gamma-interferon (IFN-gamma) on synthesis of procollagens, the steady state levels of types I and II procollagen mRNAs, and the expression of major histocompatibility complex class II (Ia-like) antigens on the cell surface. Adult articular chondrocytes synthesized mainly type II collagen during weeks 1-3 of primary culture, whereas types I and III collagens were also produced after longer incubation and predominated after the first subculture. Juvenile costal chondrocytes synthesized no detectable alpha 2(I) collagen chains until after week 1 of primary culture; type II collagen was the predominant species even after weeks of culture. The relative amounts of types I and II collagens synthesized were reflected in the levels of alpha 1(I), alpha 2(I), and alpha 1(II) procollagen mRNAs. In articular chondrocytes, the levels of alpha 1(I) procollagen mRNA were disproportionately low (alpha 1(I)/alpha 2(I) less than 1.0) compared with costal chondrocytes (alpha 1 (I)/alpha 2(I) approximately 2). Recombinant IFN-gamma (0.1-100 units/ml) inhibited synthesis of type II as well as types I and III collagens associated with suppression of the levels of alpha 1(I), alpha 2(I), and alpha 1(II) procollagen mRNAs. IFN-gamma suppressed the levels of alpha 1(I) and alpha 1(II) procollagen mRNAs to a greater extent than alpha 2(I) procollagen mRNA in articular but not in costal chondrocytes. Human leukocyte interferon (IFN-alpha) at 1000 units/ml suppressed collagen synthesis and procollagen mRNA levels to a similar extent as IFN-gamma at 1.0 unit/ml. In addition, IFN-gamma but not IFN-alpha induced the expression of HLA-DR antigens on intact cells. The lymphokine IFN-gamma could, therefore, have a role in suppressing cartilage matrix synthesis in vivo under conditions in which the chondrocytes are in proximity to T lymphocytes and their products. |
