a, Pathways significantly enriched in Ad/MF and P3 mSSC populations. Top, (from left-right) Protein secretion, MYC targets, E2F targets. Bottom, (from left-right) G2M checkpoint, oxidative phosphorylation and TGFb signaling. b-c, mSSC expression (b) and bulk tissue expression (c) of key genes involved in cartilage development, cell cycle and inflammation. d, mSSC gene expression levels after in vitro treatment of PBS, BMP2, or sVEGFR1.