TNF and osteoarthritis: Moreover, the treatment with osteotropic factors, such as vitamin D3, IL‐1β, TNF‐α, PGE2, IL‐6, but not PTH, and IL‐17, has been correlated with an increased membranous localization of RANKL on low osteoarthritis osteoblasts compared with high osteoarthritis osteoblasts (Tat et al., 2008).