TNFRSF11B and rheumatoid arthritis: sRANKL remained below detection level (<370 pg/ml) in both RA (n = 3) and OA osteoblasts (n = 3), while OPG was detectable but showed no changes (RA OB 1.2-fold change, p > 0.05/OA OB 1.0-fold change, p > 0.05; n = 3 each).