Extracorporeal shock wave therapy alleviates glucocorticoid-induced injury and dysfunction of bone microvascular endothelial cells via the PI3K/AKT/FOXO1 pathway.

BACKGROUND: Glucocorticoid-induced osteonecrosis of the femoral head (ONFH) is a common orthopedic condition with a high disability rate, and its pathogenesis remains incompletely understood. Increasing evidence suggests that glucocorticoid-induced damage and dysfunction of bone microvascular endothelial cells (BMECs) play a crucial role in the development and progression of ONFH. Glucocorticoids can cause damage and apoptosis of vascular endothelial cells, triggering coagulopathy and sustained inflammation. These pathological alterations contribute to thrombosis and microcirculatory disturbances, eventually leading to ischemic ONFH. As a non-invasive treatment modality, extracorporeal shock wave therapy (ESWT) offers several advantages, including its non-invasive nature, adjustable stimulation intensity, low procedural risk, and minimal complications. ESWT has been shown to relieve pain, improve hip joint function, and delay disease progression in ONFH patients. Moreover, several studies have reported that the therapeutic efficacy of ESWT is superior to that of core decompression or core decompression combined with bone grafting. However, the underlying mechanisms of its effectiveness remain unclear. This study aimed to investigate the effects and potential mechanisms of ESWT in an in vitro model of glucocorticoid-induced BMECs injury.

METHODS: An in vitro model of glucocorticoid-induced injury in BMECs was established, and various intensities of ESWT were applied to determine the optimal treatment parameters. To assess the therapeutic effects of ESWT on glucocorticoid-induced injury in BMECs, cell viability, proliferation, angiogenic capacity, migration, and apoptosis were evaluated using the Cell Counting Kit-8 (CCK-8) assay, 5-ethynyl-2'-deoxyuridine (EdU) incorporation assay, tube formation assay, wound healing and Transwell assays, and Annexin V-fluorescein isothiocyanate (FITC)/propidium iodide (PI) assay, respectively. In addition, Western blot analysis was conducted to examine the expression levels of PI3K, phospho- (p-)PI3K, AKT, p-AKT, FOXO1, and p-FOXO1. The involvement of the PI3K/AKT/FOXO1 signaling pathway in the protective effect of ESWT was further validated using a specific PI3K inhibitor LY294002.

RESULTS: Our study demonstrated that the biological effects of ESWT exhibit a dose-dependent pattern, and 0.06 mJ/mm2 with 1,000 pulses may represent the optimal parameter for alleviating glucocorticoid-induced injury in BMECs. ESWT effectively mitigated BMEC injury and dysfunction caused by glucocorticoid exposure, as evidenced by enhanced cell viability, proliferation, angiogenic capacity, and migration ability, as well as reduced apoptosis. Western blot analysis further revealed that ESWT treatment significantly increased the phosphorylation levels of PI3K, AKT, and FOXO1, as indicated by elevated p-PI3K/PI3K, p-AKT/AKT, and p-FOXO1/FOXO1 ratios. Moreover, these protective effects of ESWT were abolished by the PI3K inhibitor LY294002.

CONCLUSIONS: Our findings indicate that ESWT mitigates glucocorticoid-induced BMECs injury and dysfunction by activating the PI3K/AKT/FOXO1 signaling pathway.