Conclusion
This study suggests that inhibition of IL-17A in Th17-conditioned cartilage tissue only partially reduced the MMP-mediated type II collagen degradation and ADAMTS-mediated aggrecan degradation, while the TNFα inhibitor treatment fully reduced both MMP- and ADAMTS-mediated ECM degradation. This exploratory study where ECM biomarkers are combined with Th17-conditioned ex vivo model may hold great potential as output for describing joint disease mechanisms and predicting structural effects of treatment on joint tissue.
Methods
Naïve CD4+ T cells from healthy human buffy coat were differentiated into Th17 cells, followed by Th17 cell activation to secrete Th17-related cytokines and molecules into media. The activated Th17 cells were isolated from the conditioned media (CM) and analyzed using flow cytometry to verify Th17 cell differentiation. The CM were assessed with ELISA to quantify the concentrations of cytokines secreted into the media by the Th17 cells. Healthy bovine cartilage explants were cultured with the Th17-CM and treated with IL-17A and TNFα inhibitors for 21 days. In harvested supernatant from the cartilage cultures, MMP- and ADAMTS-mediated biomarker fragments of type II collagen, aggrecan, and fibronectin were measured by ELISA to investigate the ECM remodeling within the cartilage tissue.
Results
Th17-CM stimulated a catabolic response in the cartilage. Markers of type II collagen and aggrecan degradation were upregulated, while anabolic marker of type II collagen formation remained on similar levels as the untreated explants. The addition of IL-17A inhibitor to Th17-CM decreased the elevated type II collagen and aggrecan degradation, however, degenerative levels were still elevated compared to untreated group. The addition of TNFα inhibitor completely reduced both type II collagen and aggrecan degradation compared to untreated explants. Moreover, the TNFα inhibitor treatment did not alter the type II collagen formation compared to untreated group.