In knee osteoarthritis, the production of cytokines and metalloproteinases in presence of chondrocytes and CD4+ T cells depends on T cell subset: An in vitro analysis

Objective

Osteoarthritis (OA) is driven by biomechanical and biochemical inflammatory processes, including CD4⁺ T cell infiltration and activation. However, the role of CD4⁺ T cell subsets interacting with neighboring cells shaping the local inflammatory milieu have remained largely unexplored. This study aimed to investigate in vitro whether interaction of chondrocyte and CD4⁺ T cells modulate cytokine and metalloproteinase production in OA, and to determine if this modulation differ depending on CD4⁺ T cell subsets.

Method

Nineteen patients with knee OA undergoing knee replacement were enrolled. From peripheral blood CD4⁺ T cells were isolated and differentiated into subsets (Th1, Th2, Th17, Treg) using a novel developed protocol. T cell differentiation was validated by flow cytometry. Chondrocytes were mono- and co-cultured with T cell subsets and in culture supernatant cytokine and metalloproteinase levels were quantified using ELISA and multiplex assays.

Results

Compared to monocultures levels MMP-1/3/9/13 and IL-6 were elevated in all co-cultures of chondrocytes and CD4⁺ T cell subsets, with the highest levels in Th17 co-cultures. GM-CSF, IL-9, IL-17 were specifically elevated in Th17 co-cultures and IFN-γ in Th1 co-cultures. TNF-α production was significantly reduced only in Treg co-culture compared to monoculture approach.

Conclusion

This study indicates that chondrocytes can interact with CD4⁺ T cell subsets in OA, modulating the production of metalloproteinases and cytokines to varying degrees, depending on the CD4⁺ T cell subset. Our findings can open new avenues in OA treatment using T cell-based or T cell subset-targeted therapies to modulate inflammatory patterns in affected OA joints.