Study on the Angiogenic Effect of Low-Intensity Pulsed Ultrasound

Objectives: We examined the angiogenic effects of low-intensity pulsed ultrasound (LIPUS) on immunohistological outcomes in a rat femoral fracture model, vascular endothelial cell migration, and allogeneic bone tissue transplant in a rat model. Subjects and Methods: Experiment 1: We exposed the fracture site in the femur of the Wister rat model to LIPUS every day. We collected the femur on the 14th day after bone fracture and prepared decalcified tissue sections. We performed immunostaining with anti-VEGF antibody in serial sections for comparison with the non-treated group. Experiment 2: We performed a scratch test 12 hours after plating 1 × 10 6 human vascular endothelial cells in a 6-well culture plate. To examine the effect of LIPUS on cell migration, we exposed cells to LIPUS via the bottom face of the culture plate for comparison with the non-treated group. Experiment 3: We transplanted a delipidized frozen dry bone to the anterior surface of a Wister rat femur, and exposed the site to LIPUS every day. We collected the femur 3 weeks after transplantation for histological examination. Results: Experiment 1: The LIPUS radiation group exhibited an anti-VEGF positive region surrounding the callus, and robust new vascularization was confirmed in the region. Experiment 2: Vascular endothelial cell migration was promoted in the LIPUS treated group. Experiment 3: The LIPUS treatment group exhibited significant formation of new vascularization around the grafted bone, compared with the non-treated group, in addition to significant formation of TRAP-positive cells. Discussions: It was suggested that LIPUS would promote the formation of new vascularization and accelerate cell migration.