COL2A1 and rheumatoid arthritis: However, supplementing culture media with IL-1β, IL-1α, or TNF-α all induced a relevant phenotype in the cartilage pellets similar to an RA-like joint with increased expression of inflammatory genes Il6 and Ccl2, reduced expression of matrix genes Acan and Col2a1, and reduced histological Safranin-O staining, supporting their use as an in vitro model suitable for characterizing the effects of therapeutic macrophages.