Bone-Targeting Peptide and RNF146 Modified Apoptotic Extracellular Vesicles Alleviate Osteoporosis

Background: Osteoporosis is a highly prevalent disease that causes fractures and loss of motor function. Current drugs targeted for osteoporosis often have inevitable side effects. Bone marrow mesenchymal stem cell (BMSCs)-derived apoptotic extracellular vesicles (ApoEVs) are nanoscale extracellular vesicles, which has been shown to promote bone regeneration with low immunogenicity and high biological compatibility. However, natural ApoEVs cannot inherently target bones, and are often eliminated by macrophages in the liver and spleen. Thus, our study aimed to reconstruct ApoEVs to enhance their bone-targeting capabilities and bone-promoting function and to provide a new method for osteoporosis treatment. Methods: We conjugated a bone-targeting peptide, (Asp-Ser-Ser) 6 ((DSS) 6 ), onto the surface of ApoEVs using standard carbodiimide chemistry with DSPE-PEG-COOH serving as the linker. The bone-targeting ability of (DSS) 6 -ApoEVs was determined using an in vivo imaging system and confocal laser scanning microscopy (CLSM). We then loaded ubiquitin ligase RING finger protein146 (RNF146) into BMSCs via adenovirus transduction to obtain functional ApoEVs. The bone-promoting abilities of (DSS) 6 -ApoEVs and (DSS) 6 -ApoEVs RNF146 were measured in vitro and in vivo. Results: Our study successfully synthesized bone-targeting and gained functional (DSS) 6 -ApoEVs RNF146 and found that engineered ApoEVs could promote osteogenesis in vitro and exert significant bone-targeting and osteogenesis-promoting effects to alleviate osteoporosis in a mouse model. Conclusion: To promote the bone-targeting ability of natural ApoEVs, we successfully synthesized engineered ApoEVs, (DSS) 6 -ApoEVs RNF146 and found that they could significantly promote osteogenesis and alleviate osteoporosis compared with natural ApoEVs, which holds great promise for the treatment of osteoporosis. Keywords: osteoporosis, mesenchymal stem cells, apoptotic extracellular vesicles, bone-targeting, bone regeneration