Engineered SHED-EVs delivering FtMt siRNA rescue mitophagy and bone formation in smoking-related osteoporosis

Tobacco smoking independently contributes to osteoporosis. Cigarette smoke-derived reactive oxygen species (ROS) and transition metals promote iron accumulation and impair mitophagy in bone marrow mesenchymal stem cells (BMSCs), causing mitochondrial dysfunction, reduced osteogenic differentiation, and iron-induced osteoporosis. The molecular pathways linking smoke exposure to impaired bone formation remain incompletely understood.

We established a cigarette smoke extract (CSE)-induced bone-loss model in female C57BL/6J mice (n = 8/group) and performed femoral transcriptomic profiling. Bone-targeting extracellular vesicles from stem cells from human exfoliated deciduous teeth (SHED-EVs) were loaded with siRNA against mitochondrial ferritin (FtMt; siFtMt) to generate BT-siFtMt@SHED-EVs. The nanoplatform was characterized and tested in vitro and in vivo using micro-CT, JC-1, Alkaline Phosphatase/alizarin red S, immunostaining, RT-qPCR, Western blotting, and in silico docking (ZDOCK/RDOCK).

CSE upregulated FtMt while suppressing mitophagy and osteogenic differentiation. BT-siFtMt@SHED-EVs restored mitochondrial membrane potential, reinstated mitophagic flux, and rescued BMSC osteogenesis. Systemically administered BT-siFtMt@SHED-EVs restored trabecular microarchitecture and bone mineral density and elevated osteogenic markers in CSE-exposed mice; these benefits were abolished by the mitophagy inhibitor Mdivi-1.

Targeted FtMt knockdown via bone-homing SHED-EVs reinstates mitochondrial quality control and ameliorates smoke-related bone loss, offering a precision mitochondrial medicine approach to osteoporosis.