Expression of ICAM-1 on intact cartilage and isolated chondrocytes

A major factor in cellular cytotoxicity is the interaction between LFA-1 on leukocytes and ICAM-1 on targets. Because several inflammatory cartilage diseases are characterized by the presence of leukocyte infiltrates, the expression of ICAM-1 on human cartilage, cultured chondrocytes, and transplanted cartilage was investigated using monoclonal antibodies. Frozen tissue sections, chondrocytes in suspension, as well as total cellular mRNA were prepared from human cartilage samples. ICAM-1 expression was studied with two different monoclonal antibodies directed against ICAM-1 by immunohistochemical APAAP-staining and additional flow cytometric analyses. The expression of ICAM-1-mRNA in cartilage tissue was analyzed using the northern blot hybridization technique. Furthermore, chondrocytes were treated in culture with interleukin-1 (IL-1) and gamma-interferon (gamma-IFN). ICAM-1 expression after culture was quantified using flow cytometric analysis. We could detect ICAM-1 mRNA in cartilage tissue, however, the immunostaining of tissue sections using monoclonal antibodies did not give clear positive reactions. Isolated chondrocytes showed strongly positive staining patterns in comparison with adequate negative controls as assessed by flow cytometry. A dose-dependent increase of the expression of ICAM-1 on chondrocytes was observed when stimulated with IL-1 and gamma-IFN. Finally, two of the three studied transplanted autologous cartilage samples with advanced resorption showed the presence of ICAM-1 molecules as assessed by immunohistochemistry. This expression of ICAM-1 suggests that the molecule plays a role in severe cartilage inflammatory processes, where tissue damage leads to the exposure of chondrocyte surfaces.