Formation of multinucleated cells with osteoclast precursor features in human cord monocytes cultures

A common lineage between monocytes and osteoclasts has been suggested but not yet proved, and an osteoclast precursor might be an immature cell of the monocyte-macrophage family. We therefore compared the ability of cord blood and adult monocytes in long-term culture to differentiate toward osteoclasts. Both adult and cord monocytes were cultured for 3 weeks in the presence of 20% horse serum. The proportion of multinucleated cells formed was influenced by 1,25(OH)2D3 in cord, but not in adult monocyte cultures: 10(-9)M 1,25(OH)2D3 increased multinucleated cells from 13 +/- 2 to 26 +/- 1% of total cells in cord monocyte cultures. The formation of multinucleated cells in cord monocyte cultures, in the presence of 10(-9) M 1,25(OH)2D, was decreased by salmon calcitonin (dose dependently from 10(-8) to 10(-6) M) and increased by 1-34 parathormone (100 ng/ml). None of these hormones induced any modification of the proportion of multinucleated cells formed in adult monocytes culture. Specific antigens on the membrane of the cells obtained after 3 weeks culture in the presence of 10(-9) M 1,25(OH)2D3 were assessed by immunocytochemistry. The respective proportion of adult and cord labeled cells was 64 +/- 11 vs. 63 +/- 6% with Leu M5 (specific for monocyte) and 68 +/- 7 vs. 30 +/- 10% (P less than 0.05) with the anti-HLA DR antibody. The monoclonal antibody 23C6 is specific to the vitronectin receptor, which is highly expressed by osteoclasts--41 +/- 2% of the cells in cord monocyte cultures--but none in the adult monocytes culture were labeled with 23C6 at the end of the culture period.(ABSTRACT TRUNCATED AT 250 WORDS)