Tumor necrosis factor-alpha cooperates with receptor activator of nuclear factor kappa B ligand in generation of osteoclasts in stromal cell-depletedrat bone marrow cell culture

A member of the tumor necrosis factor (TNF) family, receptor activator of n uclear factor kappaB ligand (RANKL; also known as ODF, OPGL, and TRANCE), p lays critical roles in osteoclast differentiation and activation in the pre sence of macrophage colony-stimulating factor (M-CSF), Recently, TNF-alpha has also been shown to induce the formation of multinucleated osteoclast-li ke cells (MNCs) in the presence of M-CSF from mouse macrophages, We demonst rated that mononuclear preosteoclast-like cells (POCs) were formed in the p resence of conditioned medium of osteoblastic cells in a rat bone marrow cu lture depleted of stromal cells. Using this culture system, in this study w e examined whether TNF-alpha affects differentiation into POCs from hematop oietic progenitor cells. Human TNF-alpha (hTNF-alpha) markedly stimulated t he formation of POCs, Moreover, a concentration as low as 0.005 ng/mL, of h TNF-alpha increased the level of mRNA for calcitonin receptor (CTR) and cat hepsin-g of POCs, The POCs induced by hTNF-alpha formed MNCs, which showed dentine-resorbing activity after coculture with primary osteoblasts, Stimul ation was observed after 24 h of treatment with hTNF-alpha. only on day 1 o r day 2 of the culture. After 24 h of hTNF-alpha treatment, expression of t he receptor activator of nuclear factor kappaB (RANK) mRNA was markedly inc reased, The addition of soluble RANKL (sRANKL) to the preformed POCs effici ently induced MNCs, Interestingly, treatment of bone marrow cells with hTNF -alpha and sRANKL synergistically augmented the formation of MNCs, This for mation was abolished by the addition of human osteoprotegerin (hOPG). These results suggest that cooperation of TNF-alpha and RANKL is important for o steoclastogenesis, (C) 2001 by Elsevier Science Inc, All rights reserved.