Inhibitory effect of minocycline on osteoclastogenesis in mouse bone marrow cells

Objective: To study the effects of minocycline hydrochloride (MINO) on the formation of tartrate-resistant acid phosphatase (TRAP) staining-positive multinucleated osteoclast-like cells in mouse bone marrow cells (BMCs) treated with 1 alpha,25(OH)(2)D-3 or soluble receptor activator of nuclear factor-kappa B ligand (s-RANKL). Materials and methods: Mouse BMCs were cultured in alpha-modified minimum essential medium containing foetal calf serum (10%) and tetracyclines (2.5, 5 and 10 mu M), such as MINO, tetracycline hydrochloride (TC), oxytetracycline hydrochloride (OXT) or doxycycline (DOXY) in the presence of 1 alpha,25(OH)(2)D-3 (10 nM) or s-RANKL (20 ng/ml) for 7 days, and the number of TRAP staining-positive osteoclast-like cells was counted. In RNA isolated from BMCs treated with 1 alpha,25(OH)(2)D-3 or s-RANKL in the presence or absence of MINO, the expressions of osteoclast differentiation relating to mRNA were analysed by reverse transcription-polymerase chain reaction. Cell viability was examined in mouse BMCs and rabbit osteoclasts treated with MINO (0.25-20 mu M and 2-50 mu M, respectively) for 24 h. Results: MINO, TC, OXT or DOXY inhibited 1 alpha,25(OH)(2)D-3-induced osteoclast-like cell formation in mouse BMCs dose dependently. MINO suppressed 1 alpha,25(OH)(2)D-3-induced up-regulation of mRNA expressions of TRAP, cathepsin K, carbonic anhydrase II, and calcitonin receptor, but not RANKL. MINO inhibited s-RANKL-induced osteoclast-like cell formation and up-regulation of mRNA expressions for nuclear factor of activated T-cells c1 (NFATc1), a key regulator of osteoclast differentiation; however, MINO had no effects on the viability of mouse BMCs and rabbit osteoclasts. Conclusion: MINO inhibits RANKL-induced osteoclastogenesis via down-regulation of NFATc1 mRNA expression in osteoclast precursor cells. (C) 2011 Elsevier Ltd. All rights reserved.