A new cytometric method for the immunophenotypic characterization of bone-derived human osteoclasts

Background: Osteoclast cell function relates to bone resorption. Isolation and characterization of these cells from in vivo sources remain difficult. The aim of this study was to show the feasibility of using flow cytometry to identify and characterize human mature osteoclasts obtained from bone tissues. Methods: Bone femoral heads obtained as discarded surgical material were used. To check the nature of 121F⁺ (a monoclonal antibody specific for human osteoclasts) cells by flow cytometry, we used laser scanning cytometry to analyze simultaneously the immunophenotype and DNA cell content of osteoclast-like cell-enriched bone samples. Results: Results were compared with conventional morphologic and cytochemical studies. The percentage of cells that showed both cytochemical (tartrate-resistant acid phosphatase [TRAP] ⁺) and immunophenotypic (121F⁺) osteoclast-associated characteristics was very similar (12.5 ± 6.2 versus 14.7 ± 11.7; P = 0.46). Laser scanning cytometry showed that 121F⁺ cells were bigger (P = 0.04) and they had a higher DNA cell content (P = 0.04) and more nuclei per cell (P = 0.04) than the 121F^- cells present in the same sample. Discussion: This study relied on the combined use of the 121F ⁺ antibody and different cytometry-based techniques to characterize the osteoclast populations from human bone.