Ketoconazole and phorbol myristate acetate regulate osteoclast precursor fusion in primary murine marrow culture

Publisher Website
Google Scholar
Abstract
Osteoclast formation requires both precursor proliferation and then fusion into a multinuclear cell. These processes can be separated in primary murine marrow culture where osteoclastogenesis is stimulated by 1,25‐dihydroxyvitamin D3 (1,25(OH)2D3). Here we investigate the regulation of precursor fusion. Ketoconazole, an agent known to inhibit cell fusion, added during the fusion period (days 5–6), dose‐dependently inhibited formation of tartrate‐resistant acid phosphatase+ (TRAP+) multinucleated cells (TRAP+MNCs), maximally at 62 ± 4% (n = 10). TRAP+MNCs in cultures exposed to 48 h of ketoconazole (1 μM) during fusion had fewer nuclei compared with control (11.7 ± 0.6 vs. 15.1 ± 0.9). This inhibitory effect was completely reversed 24 h after removal of ketoconazole from culture. Phorbol myristate acetate (PMA) stimulated TRAP+MNC formation when given during the last 12 h of culture (2.3 ± 0.2 fold compared with control). This increased formation was unaffected by the addition of hydroxyurea and accompanied by an increase in nuclei per TRAP+MNC (15.5 ± 0.9 vs. 13.1 ± 0.6). Finally, staurosporine decreased TRAP+MNC formation in the presence or absence of PMA, implying that protein kinase C is involved in fusogenic processes. Regulation of fusion appears to be another mechanism by which bone remodeling can be modulated in vivo.
Funding Information
  • NIH Career Development Award (NIH AR 42360, (AR01945-01 to DMB))
  • Veterans Affairs Rehabilitation and Development Department