Abstract: Objective To evaluate therapeutic effects of BMSCs on BRONJ in rats. Methods SD rats were injected intravenously with zoledronate (80 μg/kg/week) via the tail vein. After two weeks of administration, under general anesthesia, the first molars from bilateral maxillae were extracted. Drugs were continuously injected for 12 weeks to establish a rat BRONJ model. The 3rd generation of isolated BMSCs from peripheral bones were cultivated in the Bio-Oss scaffold for later use. BRONJ rats were randomly divided into four groups, and treated with surgical debridement under general anesthesia. Then, BMSCs/scaffold and scaffold were transplanted into operation sites of BRONJ rats under aseptic conditions, respectively. Rats with or without surgical debridement were used as negative control and blank control. Thereafter, rats were sacrificed at 4 and 8 weeks in batches, and bone samples were collected. New bone formation was observed by Micro-CT scanning and histological analysis. Expressions of signaling pathway related factors including RANKL and OPG were detected using ELISA testing. Results Micro-CT and histological analysis showed that bone repair effect of the BMSCs/scaffold group was optimal, presenting rapid scaffold degradation, active new bone formation and high bone mineral density (P<0.05). Bone repair effect of the scaffold group was the second, presenting slower degradation, less new bone formation and lower bone mineral density compared with the BMSCs/scaffold group. Bone repair effect of the debridement group was the worst, showing pit-like bone defect and exposed dead bone. Even worse, the bone defect was enlarged after surgical debridement. The control group presented major histopathological manifestations of human BRONJ, including non-healed or delay-healed mucosa, exposed necrotic bone, osseous sclerosis and inflammatory infiltration. Cytokines results showed that RANKL/OPG ratio was the lowest in BMSCs/scaffold group and the highest in debridement group at 4 and 8 weeks. The RANKL/OPG ratio of BMSCs/scaffold group and scaffold group significantly decreased than that of control group (P<0.05), but the ratio of debridement group significantly increased compared with the control group (P<0.05). Conclusion BMSCs from peripheral bones have a therapeutic effect on BRONJ, which can promote the repair of bone defect after debridement in BRONJ rats. RANKL/RANK/OPG signaling pathway may play an essential role in the development of BRONJ.

Key words: bone mesenchymal stem cell, bisphosphonate-related jaw osteonecrosis, therapy