AIM: To explore the regulatory mechanism of pinoresinol diglucoside (PDG) on angiogenesis during osteoporotic fracture healing in vivo and in vitro. METHODS: Fifty male C57BL/6J mice were randomly divided into five groups: normal group, model group, PDG 0.005, 0.015 g/kg groups, and parathyroid hormone 1-34 (PTH1-34) 4×10-5 g/kg group. The osteoporotic fracture model of ovariectomized combined with femoral fracture was established, the PDG group was given intragastric administration every other day and the PTH1-34 group was given subcutaneous injection of PTH1-34 every other day for 8 weeks. Micro-CT scanning, immunofluorescence and immunohistochemical staining were used to detect the related parameters and protein expressions. Human umbilical vein endothelial cells (HUVECs) were cultured, normal group, PDG 1, 10, 100 μmol/L groups and PTH1-34 1 ng/mL group were set up. CCK-8 assay, scratch experiment, tubule formation experiment, immunofluorescence and Western blot were used to detect the related parameters and protein expressions. RESULTS: In vivo experiments found, compared with the normal control group, a small amount of bone callus volume of fracture site were increased in the model control group, while BMD of non-callus site of femur, trabecular bone fraction (BV/TV), trabecular thickness (Tb. Th) and trabecular number (Tb. N) were decreased (P<0.01), and trabecular separation (Tb. Sp) was increased (P<0.01). The positive expression of vascular endothelial marker vascular endothelial markers (CD31) was decreased (P<0.01). Compared with mice in the model control group, bone callus volume, index of BMD and BV/TV were increased in the PDG 0.005 g/kg group (P<0.05), index of BMD, BV/TV, Tb. Th, Tb. N were increased, and index of Tb. Sp was decreased in the PDG 0.015 g/kg group (P<0.05), the positive expression of CD31 was increased in the PDG administration groups (P<0.01), the protein expressions of vascular endothelial growth factor (VEGF-A) (P<0.01), Yes-associated protein 1 (YAP1) (P<0.01), PDZ-binding motif (TAZ) (P<0.05) and TEA domain transcription factor 2 (TEAD2) (P<0.01) were increased in callus in the PDG 0.015 g/kg groups. Cell experiments found, compared with the normal control group, PDG groups promoted the proliferation, migration and tubule formation activity of HUVECs to varying degrees (P<0.05), at the same time, the expression of endothelial cadherin (E-cadherin) was decreased (P<0.01), and VEGF-A, TEAD2, TAZ and YAP1 protein expression were increased (P<0.05). CONCLUSION: PDG may accelerate osteoporotic fracture healing by promoting bone angiogenesis through regulating Hippo signal pathway.
