Synthetic biology-based bacterial extracellular vesicles displaying BMP-2 and CXCR4 to ameliorate osteoporosis.

Osteoporosis (OP) is a systematic bone disease characterized by low bone mass and fragile bone microarchitecture. Conventional treatment for OP has limited efficacy and long-term toxicity. Synthetic biology makes bacterial extracellular vesicle (BEVs)-based therapeutic strategies a promising alternative for the treatment of OP. Here, we constructed a recombinant probiotics Escherichia coli Nissle 1917-pET28a-ClyA-BMP-2-CXCR4 (ECN-pClyA-BMP-2-CXCR4), in which BMP-2 and CXCR4 were overexpressed in fusion with BEVs surface protein ClyA. Subsequently, we isolated engineered BEVs-BMP-2-CXCR4 (BEVs-BC) for OP therapy. The engineered BEVs-BC exhibited great bone targeting in vivo. In addition, BEVs-BC had good biocompatibility and remarkable ability to promote osteogenic differentiation of BMSCs. Finally, the synthetic biology-based BEVs-BC significantly prevented the OP in an ovariectomized (OVX) mouse model. In conclusion, we constructed BEVs-BC with both bone-targeting and bone-forming in one-step using synthetic biology, which provides an effective strategy for OP and has great potential for industrialization.