Formation of osteoclasts and osteoblast-like cells in long-term human bone marrow cultures

A culture system for human osteoclasts is described. It is based on incubation of mononuclear marrow cells for three weeks in the presence of 1,25 dihydroxyvitamin D3. The resulting cells exhibited all the classic characteristics of osteoclasts. They formed a true syncytium with up to 25 nuclei per cell. The cells revealed a strong positive reaction for tartrate-resistant acid phosphatase and a ruffled border. When these cells were cultured on 100 microns thick human dentine slices for three weeks, typical resorption pits were formed. In the culture, alkaline phosphatase-positive osteoblast-like cells were formed in the vicinity of osteoclasts. This culture system permits studies of human osteoclasts and their interaction with osteoblast cell precursors in the human bone marrow.