| Bone fracture, particularly that occurring in osteoporotic conditions, has become a major health issue. Fracture healing is a well-orchestrated regenerative process, the enhancement of which has been one of the major goals in fracture management. Low-magnitude high-frequency vibration (LMHFV) is osteogenic for intact bone and beneficial for limb blood circulation, which implies a potential of enhancement for fracture healing. Three parts of the experiments were conducted in this study to test the hypothesis that LMHFV would accelerate fracture healing by promoting chondrogenesis, endochondral ossification, and remodeling in both normal and osteoporotic bones.;Part I study. Three-month-old female SD rats underwent closed femoral fracture and were randomized into either vibration group (VG-I, 35Hz, 0.3g, 20min/day, 5days/week) or sham-treated control group (CG-I). Femora were harvested at 1, 2 and 4 weeks for micro-CT analysis, histomorphometry, and mechanical testing. Part II study. Osteoporotic model was established in nine-month-old SD rats after three months of inducement following ovariectomy. Similar grouping (VG-II and CG-II) and treatment regimes were performed after fracture, with the femora harvested at 2, 4 and 8 weeks for assessments like those in the Part I study. Part III study. After fracture, 3-month-old female SD rats were grouped (VG-III and CG-III) and treated as in the Part I study. At 1, 2 and 4 weeks, femora were collected for gene quantification (Col-1, Col-2, BMP-2, VEGF, and TGF-beta1) using real-time PCR. Type I and II collagens were located immunochemically in histological sections.;Results of the Part I and II studies demonstrated that LMHFV promoted callus formation (together with chondrogenesis), mineralization (endochondral ossification), and remodeling, which led to faster healing and better mechanical outcomes in both normal and osteoporotic fractures. In molecular level, the effect of LMHFV was reflected by the stimulation of chondrogenesis and osteogenesis related matrix collagen formation and growth factor expression. The molecular data echo Part I and II findings well. This study proved that LMHFV accelerated fracture healing by promoting chondrogenesis, endochondral ossification, and remodeling in both normal and osteoporotic bones, and indicated great potential of its future clinical application on fracture healing. |
