OA-FLSs accumulated less HIF-1α than RA-FLSs, and RA-FLSs expressed higher levels of BNIP3 than OA-FLSs, which supported the hypothesis that RA-FLSs showed better metabolic and mitophagy adaptive response to hypoxia (Fig. 4D, E). Here, BNIP3 is linked to rheumatoid arthritis.