After 12 h of hypoxia, HIF-1α and BNIP3 accumulated in OA-FLSs and RA-FLSs, but at 24 h, HIF-1α and BNIP3 did not accumulate in OA-FLSs compared with normoxia, but in RA-FLSs, HIF-1α and BNIP3 continued to accumulate (Fig. 4D, F). Here, BNIP3 is linked to rheumatoid arthritis.