MMP9 and osteoarthritis: The genes enriched in the osteoarthritis pathway revealed by IPA of the DEGs in the palovarotene-treated chondrocytes included various matrix catabolic genes (Adamts4, Adamts5, Mmp9, Mmp10, Mmp12, and Mmp13) and cell death-related genes (Casp1, Casp3, and Casp6).