Propranolol

All the experiments were approved by the Ethics Committee of Biomedical Science of Peking University (approval no. LA20210509). Twelve-week-old female C57BL/6 mice were used in this study. The mice were anesthetized and subjected to bilateral ovariectomy (OVX) as described previously.^{46 (link)} Two months later, the mice were further subjected to tibia fracture or sham operation as previous description with modification.^{47 (link)} Briefly, the mice were anesthetized with 2%-4% isoflurane gas and a syringe needle was inserted into the tibia canal for fixation. Fractures were created at the mid-diaphysis using scissors. X-ray confirmed the position of the intramedullary pin and fracture. OVX mice with fractures were further randomly assigned to four treatment groups: iPTH (rhPTH1-34; Shenzhen Salubris Pharmaceuticals Co, China), propranolol (MedChemExpress, New Jersey, USA), iPTH + propranolol, or vehicle. PTH was intermittently administrated by subcutaneous injection at 80 μg/kg once a day at approximately 10 am. propranolol hydrochloride was dissolved in drinking water (0.5 g/L) and was delivered daily (changed once per 3 days). Mice were euthanized after 4 weeks of treatment. Tissues, including tibias, femurs, lumbar vertebrae and serum, were collected for further analyses.