Given previous evidence that RA-FLSs expressed more adrenomedullin and adrenomedullin receptors (CLR/RAMP-2 and CLR/RAMP-3) than did OA-FLS [10], we compared the effect of adrenomedullin on RA-FLSs and OA-FLSs. This evidence concerns the gene ACKR5 and rheumatoid arthritis.