RT-qPCR results showed a significant upregulation of leptin mRNA and protein expression of RA-FLSs under hypoxic conditions, while osteoblast markers (RUNX2, OCN, and ALP) were significantly downregulated (Figures 4(c)–4(e)), which indicated that hypoxia increased leptin expression and reduced RA-FLS osteogenesis. Here, LEP is linked to rheumatoid arthritis.