TNFSF11 and rheumatoid arthritis: NFATC1, the main cytokine involved in RANKL-induced osteoclastogenesis, was also upregulated in active RA synovial tissues, compared to inactive RA, OA, or normal synovial tissues [33] and our results confirmed that NFATC1 was expressed in synovial tissues, and that its level was higher in RA patients compared to OA patients.