Comparison of osteoclast precursors in peripheral blood mononuclear cells from rheumatoid arthritis and osteoporosis patients

Osteolytic disorders cause serious problems for quality of life with aging. Osteolysis is performed by osteoclasts of the hematopoietic lineage that share some characteristics with monocytes and macrophages. As osteoclast precursors (pOCs) are present in peripheral blood, their characterization in osteolytic diseases may help us to understand risk factors. Although essential factors for osteoclastogenesis have been reported, the effective induction from pOCs in human peripheral blood mononuclear cells (PBMCs) to mature osteoclasts in culture requires further improvement. The aim of this study was development of an efficient culture system for human osteoclastogenesis and providing a simple system for the enrichment of pOCs from PBMCs. We employed coculturing of human PBMCs with a mouse stromal cell line. Significant numbers of tartrate-resistant acid phosphatase-positive (TRAP⁺) multinucleated osteoclasts (MNCs), which could resorb dentine slices, were efficiently induced in this culture condition. pOCs were enriched in an anti-CD16 antibody column-passed anti-CD14 antibody-bound cell population isolated by magnetic cell sorting. We compared the percentage of the CD14high CD16dull cell population, which mainly contained pOCs in PBMCs, from age-matched patients with rheumatoid arthritis (RA) and osteoporosis (OP), but it was comparable. However, the mean number of TRAP⁺ MNCs generated in cultures from PBMCs of RA was higher. In contrast, the frequency of pOCs in PBMCs from OP was relatively higher. These results suggest the characteristics of pOCs from RA and OP may be different, because single pOCs from OP gave rise to lower numbers of osteoclasts than those from RA.