Effects of continuous and released compressive force on osteoclastogenesis invitro

Abstract

ObjectiveCompressive force has been found to be catabolic to alveolar bone during orthodontic tooth movement. This study quantified the fusion of mononuclear RAW 264.7 cells (a murine osteoclastic-like cell line) into multinucleated osteoclasts under a hydrostatic pressure-generated mechanical compression-the new model of various magnitudes and durations. MethodsRAW 264.7 cells were subjected to 0.3, 0.6 or 0.9 g/cm2 of compressive force by an acrylic cylinder custom-made by laser cutting or no compressive force for 4 days during osteoclastogenic induction. TRAP-positive multinucleated cells were quantified. For the release from force experiment, osteoclastogenesis was induced by 0.6 g/cm2 mechanical stimuli for 0, 1, 2, 3 or 4 days. Cell viability, TRAP-positive multinucleated cells, DCSTAMP and Cathepsin K (CTSK) gene expression were evaluated 4 days after release from force. ResultsCompressive force at 0.6 and 0.9 g/cm2 significantly increase the number of TRAP-positive multinucleated cells (P < 0.05). Release from continuous mechanical compression after 4 days significantly elevated the number of TRAP-positive multinucleated cells and DCSTAMP and CTSK mRNA expression, with no adverse effects on cell viability (P < 0.05). ConclusionsContinuous stimulation with compressive force induced osteoclastogenesis in RAW 264.7 cells by enhancing DCSTAMP and CTSK expression, which provides new understanding of bone remodeling during orthodontic treatment.