Influence of Calcium Hydroxide–loaded Microcapsules on Osteoprotegerin and Receptor Activator of Nuclear Factor Kappa B Ligand Activity

Abstract Introduction Calcium hydroxide (Ca[OH] 2 ) microcapsules were synthesized to allow controlled release of Ca(OH) 2 . The aim of this study was to evaluate the influence of Ca(OH) 2 microcapsules on osteoprotegerin (OPG) activity, receptor activator of nuclear factor kappa B ligand (RANKL) activity, and the OPG/RANKL ratio compared with pure Ca(OH) 2 powder and Vitapex (Neo Dental Chemical Products Co Ltd, Tokyo, Japan). Methods One formula of Ca(OH) 2 microcapsules was evaluated, and pure Ca(OH) 2 powder was used as a control. A commonly used Ca(OH) 2 medication containing an oily vehicle (Vitapex) was also evaluated, and the in vitro release profile of Vitapex was studied. The human osteosarcoma cell line MG63 was used to evaluate the influence of Ca(OH) 2 microcapsules, pure Ca(OH) 2 powder, and Vitapex on OPG and RANKL activity. The relative messenger RNA (mRNA) expression of OPG and RANKL was determined by real-time polymerase chain reaction. The protein expression of OPG and RANKL in supernatants was measured using enzyme-linked immunosorbent assay. Results Vitapex prolonged the release of Ca(OH) 2 compared with pure Ca(OH) 2 powder, and the release rate of Vitapex was faster than that of the microcapsules. The OPG/RANKL ratio in the microcapsules group was up-regulated at both the mRNA and protein levels compared with the negative control group and the pure Ca(OH) 2 powder group. The ratio in the Vitapex group was lower than the microcapsule group both at the mRNA and protein levels. Conclusions Ca(OH) 2 microcapsules increased the expression of OPG although they did not increase the expression of RANKL compared with pure Ca(OH) 2 powder and Vitapex. This increase in expression led to an increase in the OPG/RANKL ratio and eventual inhibition of osteoclast activity.