Inhibition of KDM6B prevents osteoarthritis by blocking growth plate-like H3K27me3 loss in bivalent genes.

Osteoarthritis (OA) is the most prevalent joint disorder occurring with articular cartilage degradation. It includes a switch from an articular to a growth plate chondrocyte phenotype. Here, we investigated the histone modification profiles and found significant H3K27me3 loss in OA, which led to disease-associated gene expression. Surprisingly, these genes were occupied by both H3K27me3 and H3K4me3 in normal chondrocytes, showing a poised bivalent state. Furthermore, we observed the derepression of similar bivalent genes in growth plate chondrocytes. Finally, a KDM6B inhibitor GSK-J4 prevented the H3K27me3 loss and cartilage damage in the rat OA model. Our results reveal an inherited bivalent epigenetic signature on developmental genes that makes articular chondrocytes prone to hypertrophy and contributes to a promising epigenetic therapy for OA.