Studies on type II collagen and aggrecan production in human articular chondrocytes in vitro and effects of transforming growth factor-beta and interleukin-1beta.

Type II collagen and aggrecan are major components of the extracellular matrix of articular cartilage. Their biosynthesis and catabolism are regulated by chondrocytes. They may be used as markers of chondrocyte phenotype for cells cultured in vitro. Type II collagen gene expression was detected by amplification of type II collagen-specific sequences, using cDNA produced by reverse transcription of mRNA extracted from freshly isolated and cultured human articular chondrocytes by the polymerase chain reaction (PCR). The synthesis of gene product was confirmed by immunohistochemical localization of type II collagen in cartilage sections and in cultured chondrocytes. Aggrecan core protein was also immunolocalized in cartilage sections and in chondrocytes in culture. Expression of type II collagen or aggrecan was not detected immunohistochemically in skin or bone. These results demonstrate that human articular chondrocytes can be characterized in culture, by the combined application of PCR and immunohistochemistry. Interleukin-1beta (IL-1beta) may play an important role in the destruction of cartilage matrix in arthritis, whereas transforming growth factor-beta (TGFbeta) may have an opposing effect and their combined actions may modulate chondrocyte phenotype. The effect of rhIL-1beta and rhTGFbeta on the production of type II collagen by chondrocytes in culture was investigated. It was shown that TGFbeta enhanced the production of type II collagen, localized immunocytochemically, in cultured chondrocytes. IL-1beta inhibited expression of mRNA for type II collagen. The implications of this study, in terms of a better understanding of degenerative cartilage disease, are discussed.