Dual-targeted bioengineered bacterial extracellular vesicles ameliorate senile osteoporosis via SAE1-mediated NAT10 SUMOylation and ac4C-dependent glycolysis

Senile osteoporosis (SOP) is an age-related skeletal disease characterized by progressive bone loss and the deterioration of bone microarchitecture. Promoting the osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) is a potential strategy for SOP intervention; however, achieving targeted regulation of BMSCs with translational feasibility remains challenging. Given the modifiability, biocompatibility, and production potential of bacterial extracellular vesicles (BEVs), this study constructed dual-targeted bioengineered BEVs (BT-BEVs-CS) via synthetic biology. These BT-BEVs-CS display the bone-targeting peptide Ser-Asp-Ser-Ser-Asp (SDSSD, BT), the chemokine receptor CXCR4, and SUMOylation activating enzyme subunit 1 (SAE1) to promote the osteogenic differentiation of BMSCs. In vitro and in vivo experiments showed that, via the synergistic action of CXCR4 and BT, BT-BEVs-CS targeted the bone microenvironment and were internalized by BMSCs. Mechanistic studies suggested that targeted delivery of SAE1 promoted the SUMOylation of N-acetyltransferase 10 (NAT10), thereby attenuating its ubiquitin-mediated degradation. Stabilized NAT10 subsequently supported the N4-acetylcytidine (ac4C) modification of the mRNA encoding phosphoglucose isomerase (PGI), enhancing PGI mRNA stability. This modification contributed to increased PGI expression, enhanced glycolytic activity, and improved energy support for the osteogenic differentiation of BMSCs. In vivo studies further showed that BT-BEVs-CS facilitated the osteogenic differentiation of BMSCs and ameliorated pathological bone loss in SOP mouse models. In summary, this study constructed bioengineered BT-BEVs-CS with bone-targeting and osteoinductive properties. This work provides insights into the mechanisms of the SAE1-NAT10/ac4C-PGI regulatory axis in post-translational modifications (PTMs), RNA epigenetic regulation, and glycolysis, offering a preclinical proof-of-concept for targeted nano-intervention strategies for SOP.