Engineered Extracellular Vesicles Delivering miR-30d-5p Alleviate Osteonecrosis of the Femoral Head

Osteonecrosis of the femoral head (ONFH) remains a significant clinical challenge characterized by impaired bone regeneration and compromised blood supply. This study aimed to investigate the therapeutic efficacy and mechanism of engineered extracellular vesicles (EVs) derived from bone marrow mesenchymal stromal cells (BMSCs) preconditioned with pulsed electromagnetic fields (PEMFs). We demonstrated that BMSC-EVs harvested under a specific PEMF of 3 millitesla (mT) (BMSC-EVsPEMFs (3 mT)) significantly enhanced the proliferation and osteogenic differentiation of glucocorticoid-insulted osteoblasts in vitro. In an ONFH rat model, BMSC-EVsPEMFs (3 mT) administration effectively facilitated the restoration of the femoral head bone structure and promoted angiogenesis, as evidenced by increased CD31 expression. Mechanistically, miRNA sequencing revealed that miR-30d-5p was significantly upregulated in BMSC-EVsPEMFs (3 mT), which downregulated the expression of CYP24A1 and promoted osteogenic differentiation. These findings suggest that PEMF preconditioning with an amplitude of 3 mT optimizes the cargo of BMSC-EVs to promote osteogenic differentiation and alleviate ONFH via the miR-30d-5p/CYP24A1 axis.