MCP-1-induced human osteoclast-like cells are tartrate-resistant acid phosphatase, NFATc1, and calcitonin receptor-positive but require receptor activator of NFkappaB ligand for bone resorption.

MCP-1 (monocyte chemotactic protein-1) is a CC chemokine that is induced by receptor activator of NFkappaB ligand (RANKL) in human osteoclasts. In the absence of RANKL, treatment of human peripheral blood mononuclear cells with macrophage colony-stimulating factor and MCP-1 resulted in tartrate-resistant acid phosphatase (TRAP)-positive multinuclear cells that are positive for calcitonin receptor (CTR) and a number of other osteoclast markers, including nuclear factor of activated t cells, cytoplasmic, calcineurin-dependent 1 (NFATc1). Although NFATc1 was strongly induced by MCP-1 and was observed in the nucleus, MCP-1 did not permit the formation of bone-resorbing osteoclasts, although these cells had the typical TRAP(+)/CTR(+) multinuclear phenotype of osteoclasts.

Gene array identification of osteoclast genes: differential inhibition of osteoclastogenesis by cyclosporin A and granulocyte macrophage colony stimulating factor.

Treatment of adherent peripheral blood mononuclear cells (PBMCs) with macrophage colony stimulating factor (M-CSF) and receptor activator of NF-kappaB ligand (RANKL) stimulates the formation of multinucleate osteoclast-like cells. Treatment with M-CSF alone results in the formation of macrophage-like cells. Through the use of Atlas human cDNA expression arrays, genes regulated by RANKL were identified.