Formation of osteoclast-like cells from peripheral blood of periodontitis patients occurs without supplementation of macrophage colony-stimulating factor

Aim: To determine whether peripheral blood mononuclear cells (PBMCs) from chronic periodontitis patients differ from PBMCs from matched control patients in their capacity to form osteoclast-like cells. Material and Methods: PBMCs from 10 subjects with severe chronic periodontitis and their matched controls were cultured on plastic or on bone slices without or with macrophage colony-stimulating factor (M-CSF) and receptor activator of nuclear factor-kB ligand (RANKL). The number of tartrate-resistant acid phosphatase-positive (TRACP1) multinucleated cells (MNCs) and bone resorption were assessed. Results: TRACP1 MNCs were formed under all culture conditions, in patient and control cultures. In periodontitis patients, the formation of TRACP1 MNC was similar for all three culture conditions; thus supplementation of the cytokines was not needed to induce MNC formation. In control cultures, however, M-CSF or M-CSF/RANKL resulted in higher numbers compared with cultures without cytokines. Upregulations of osteoclast marker mRNA cathepsin K and carbonic anhydrase II confirmed the osteoclastic character. Bone resorption was only observed when PBMCs were cultured in the presence of M-CSF and RANKL. Conclusion: Our data indicate that PBMCs from periodontitis patients do not need priming by M-CSF to become osteoclast-like cells, suggesting that PBMCs from periodontitis patients are present in the circulation in a different state of activity