Histochemical examination of systemic administration of eldecalcitol combined with guided bone regeneration for bone defect restoration in rats.

The aim of this experiment was to elucidate the histological alterations after systemic administration of eldecalcitol (ELD) combined with guided bone regeneration during the restoration of bone defect healing in rats. The femurs of 8-week-old Wister rats were used to generate bone defect models. The defect was covered with a collagen membrane, and ELD group was administrated with eldecalcitol (50 ng/kg body weight) intragastrically once every other day. Femora were harvested at 1, 2, 4 and 8 weeks post-surgery. Decalcify tissue slices were made and used for histological and immunohistochemical examination. Bone biomarkers of RANKL, OPG and osteocalcin (OCN) were detected by western blot. The results revealed that the system administration of ELD could improve new bone formation demonstrated by the increased bone volume/tissue volume ratio and accelerated mineralization. ELD suppressed osteoclastic bone resorption by reducing the number of osteoclasts, decreasing the expression of cathepsin-K and the ratio of RANKL/OPG at the early stage of bone defect restoration (1 and 2 weeks) and upregulating OCN expression at the later stage of bone defect healing (4 and 8 weeks). These data suggested that systemic administration of eldecalcitol accelerated bone formation and promoted bone maturation by decreasing bone resorption and promoting bone mineralization during bone defect restoration.