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Background: Steroid-induced Osteonecrosis of the Femoral Head (SIONFH) is a skeletal disease with a high incidence and a poor prognosis. Whole body vibration therapy (WBVT), a new type of physical training, is known to promote bone formation. However, it remains unclear whether WBVT has a therapeutic effect on SIONFH.Materials and methods: Thirty adult male and female Sprague-Dawley (SD) rats were selected and randomly assigned to three experimental groups: the control group, the model group, and the mechanical vibration group, respectively. SIONFH induction was achieved through the combined administration of lipopolysaccharides (LPS) and methylprednisolone sodium succinate for injection (MPS). The femoral head samples underwent hematoxylin and eosin (H&E) staining to visualize tissue structures. Structural parameters of the region of interest (ROI) were compared using Micro-CT analysis. Immunohistochemistry was employed to assess the expression levels of Piezo1, BMP2, RUNX2, HIF-1, VEGF, CD31, while immunofluorescence was used to examine CD31 and Emcn expression levels.Results: The H&E staining results revealed a notable improvement in the ratio of empty lacuna in various groups following WBVT intervention. Immunohistochemical analysis showed that the expression levels of Piezo1, BMP2, RUNX2, HIF-1, VEGF, and CD31 in the WBVT group exhibited significant differences when compared to the Model group (p < 0.05). Additionally, immunofluorescence analysis demonstrated statistically significant differences in CD31 and Emcn expression levels between the WBVT group and the Model group (p < 0.05).Conclusion: WBVT upregulates Piezo1 to promote osteogenic differentiation, potentially by enhancing the HIF-1α/VEGF axis and regulating H-vessel angiogenesis through the activation of the Piezo1 ion channel. This mechanism may lead to improved blood flow supply and enhanced osteogenic differentiation within the femoral head.

Background: Osteonecrosis of the femoral head is a complex hip ailment. The precise changes in bone tissue during the disease’s onset remain unclear. It is vital to assess both the quantity and quality of the trabecular state in a necrotic femoral head.Aim: This study aims to identify and compare the ultrastructural changes in osteocyte morphology and nanomechanical characteristics within various regions of necrotic femoral heads.Methods: Between December 2016 and May 2023, we gathered ten necrotic femoral heads from patients and five femoral heads from cadavers. The samples from the necrotic femoral heads were categorized into three areas: necrotic, sclerotic, and normal. Our assessment methods encompassed hematoxylin and eosin staining, sclerostin (SOST) immunohistochemistry, micro-computed tomography, nanoindentation, and acid-etched scanning electron microscopy. These techniques enabled us to examine the SOST expression, trabecular microstructure, micromechanical properties of trabeculae, and modifications in osteocyte morphology at the ultrastructural level.Results: The protein level of SOST was found to be lower in the sclerotic area. In the necrotic area, decreased values of bone volume fraction, trabecular thickness, and trabecular number and an increased value of trabecular separation were found. Conversely, in the sclerotic area, higher mean values of bone volume fraction, trabecular number, and trabecular thickness and lower trabecular separation indicated significant changes in the structural characteristics of trabeculae. Compared with the healthy area, the elastic modulus and hardness in the sclerotic area were significantly higher than those in the necrotic, normal, and control areas, while those in necrotic areas were significantly lower than those in the healthy area. The number of osteocytes tended to increase in the sclerotic area with more canalicular cells compared to the healthy area and control group.Conclusion: These results imply that the stress distribution within the sclerotic area could potentially lead to enhanced trabecular quality and quantity. This effect is also reflected in the increased count of osteocytes and their canaliculars. It is plausible that the sclerotic trabecular bone plays a pivotal role in the repair of necrotic femoral heads.