Dual-engineered small extracellular vesicles targeted delivery miR-126 for reducing age-related bone loss

MiRNA based nucleic acid therapeutics have been extensively investigated for the treatment of agerelated diseases. However, efficient delivery of miRNA and effective therapy for age-related bone loss remain major challenges. In this study, we devised an engineered small extracellular vesicle (sEV) platform to address the dysregulation of bone homeostasis in the elderly. Initially, miR-126 was encapsulated into sEV to generate miR-126 loaded small extracellular vesicles (m-sEV), whose capacity to enhance vascularized bone regeneration was validated in vitro and in a mandibular defect model of aged rats. To further optimize systemic therapeutic efficacy, we functionalized m-sEV with a bone-targeting peptide:(DSS) 6 , thereby constructing bone-targeting engineered vesicles (Bm-sEV). Systemic administration of Bm-sEV enabled precise miR-126 targeted delivery to bone tissue, resulting in increased abundance of type H vessels in the femur, improved bone microarchitecture, and attenuation of age-related bone loss. Mechanistic analyses demonstrated that the angiogenesisosteogenesis coupling effect was mediated by upregulation of endothelial Integrin β3 (ITGB3), which subsequently activated the ITGB3/ERK2 signaling cascade. Notably, Bm-sEV also restored the profoundly impaired osteoclastic activity in aged femurs, thereby re-establishing skeletal homeostasis. Collectively, Our study provides a promising approach for the treatment of age-related bone loss by combining biological macromolecules such as (DSS) 6 and miR-126 with sEV.