Human articular chondrocytes suppress in vitro proliferation of anti-CD3 activated peripheral blood mononuclear cells

Objective: To investigate whether mature human articular chondrocytes (AC) exhibit an anti proliferative effect on activated peripheral blood mononuclear cells (PBMC) and to compare this effect with other cells of mesenchymal origin. Methods: AC from healthy cadaveric cartilage were grown for different passages, in the absence (control) or presence of factors enhancing cell dedifferentiation (transforming growth factor (TGF)beta 1, fibroblast growth factor (FGF)-2, and platelet derived growth factor (PDGF)bb-TFP medium). Cell ability to suppress PBMC proliferation driven by anti-CD3 antibody was measured by tritiated thymidine uptake following incubation for 48 h at different PBMC:AC ratios and expressed as percent of residual proliferation (RP) AC anti proliferative effect was compared to that of control dermal fibroblasts (DF) and bone marrow stromal cells (BMSC). Results: AC exhibited a cell number-dependent anti proliferative effect. The strongest effect (up to 2% RP) was measured using the least expanded AC cultures. The use of TFP medium for AC expansion resulted in a significantly lower anti proliferative effect, in the range of that induced by BMSC (up to 18% RP). Also DF induced a marked anti proliferative effect (up to 11% RP) Conclusion: We report for the first time that human AC have a marked anti proliferative effect on anti-CD3 stimulated PBMC, which is reduced upon culture in medium-inducing extensive cell de-differentiation. These results reflect the immunosuppressive properties observed for other different mesenchymal cell types and raise the question of a potential common physiological role in local tissue protection.