IRoot BP Plus Inhibits Osteoclastogenesis via Up-Regulating the Expression of ROR-α

Objectives: iRoot BP Plus is a novel bioceramic material with excellent bioactivity and biocompatibility which has been considered as an alternative to mineral trioxide aggregate(MTA) in regenerative endodontic therapy. MTA has been applied popularly in endodontic therapy result from its prominent property of inhibiting osteoclastogenesis. Besides, the circadian clock regulates various physiological processes, including bone metabolism and regeneration. This study aimed to compare the effects of iRoot BP Plus on the osteoclastogenesis with MTA and explore the role of clock genes during the process.
Methods: Mouse macrophage cell line RAW 264.7 were treated with soluble receptor activator of nuclear factor kappa B ligand to osteoclastogenesis. Then the iRoot BP Plus-conditioned medium(BP-CM) of different concentrations was used to explore the effect of BP-CM on osteoclast differentiation, fusion, and bone resorption. The proliferation ability was evaluated by cell counting kit 8. Furthermore, the expressing of several core clock genes were also examined by Quantitative real-time polymerase chain-reaction and western blotting.
Results: Both MTA and iRoot BP Plus of low concentration stimulated cell proliferation. However, iRoot BP Plus of high concentration showed slight toxicity to the viability of RAW264.7 in long-term treatment. Besides, iRoot BP Plus dose-dependently reduced the total area of pits formed by osteoclasts and disrupted actin ring formation, a marker of osteoclastic bone resorption, the coincident with reduced numbers of TRAP-positive osteoclasts. In addition, the expressing of ROR-α was up-regulated significantly in RAW 264.7 treated with BP-CM while nuclear factor kappa B ligand decreased the expressing of it in RAW 264.7.
Conclusions: Our study provides further insight into the role of ROR-α in the process which iRoot BP Plus inhibit osteoclastogenesis and bone resorption and also suggests that iRoot BP Plus is an excellent bioceramic for several endodontic situations because of its capacity in inhibiting osteoclast formation.