Combined effect of parathyroid hormone and strontium ranelate on bone healing in ovariectomized rats

Objective: Parathyroid hormone (PTH) enhances bone healing. Strontium ranelate (SR) is an antiresorptive agent that increases bone formation. Reports about combined effects of PTH and SR on local bone regeneration in osteoporotic subjects are limited. We aimed at investigating the efficacy of PTH and SR for promoting new bone formation in critical-sized defects of ovariectomized rats. Materials and Methods: Parathyroid hormone- and/or SR-containing poloxamer implant tablets with/without chitosan microparticles were delivered locally to calvarial defects of 90 Wistar rats. Biopsies were analyzed histologically and histomorphometrically at 4 and 8 weeks of healing. Results: Histomorphometry revealed that PTH alone promoted new bone formation at 4 weeks but the efficiency declined in 8 weeks. There was no positive effect of SR alone on bone formation at 4 or 8 weeks. Calvarial defects treated with PTH+SR combinations showed statistically significant greater new bone formation than either treatment alone at both time intervals. Tissue responses were modest and supported the good biocompatibility of the biomaterials used. Conclusion: Parathyroid hormone and SR combinations can be effective for calvarial bone regeneration of ovariectomized rats. PTH plus SR may have potential use as bone graft material in orthopedic and dental surgery to enhance bone healing and osseointegration.