Holistic bone developing microenvironment engineered apoptotic extracellular vesicles recapitulate multidimensional developmental signatures in adult and senile bone repair

Abstract Owing to the rich repertoire of bioactive cargos inherited from parent cells, apoptotic extracellular vesicles (ApoEVs) have emerged as powerful biological agents in regenerative medicine. To augment ApoEVs regenerative potency, microenvironment‐engineered ApoEVs (ME‐ApoEVs) have been proposed, which mainly focused on embedding a single microenvironment factor within the vesicle cargo. Since the microenvironment operates as a system composed of multiple factors that collectively govern regeneration, we introduce a novel holistic microenvironment‐engineered ApoEVs (hME‐ApoEVs) for superior ME‐ApoEVs. To validate the hME‐ApoEV concept, we endowed ApoEV with a bone developing microenvironment, aiming to recapitulate developing features in adult bone repair. In the study, the developing bone microenvironment was first identified as an M2a‐like macrophage driven immune microenvironment accounting for multidimensional developmental signatures. Based on these findings, we successfully fabricated hME‐ApoEVs via stimulating the M2a‐like developing microenvironment in vitro and confirmed its recapitulation of developmental signatures. Thirdly, we found that hME‐ApoEVs recapitulated multidimensional developmental signatures in bone marrow‐derived mesenchymal stem cell (BMSC) likely through activating Wnt/β‐catenin signaling pathway. Finally, hME‐ApoEVs were verified to retain development signatures in adult and senile cranial bone repair, improving bone regeneration. Instead of engineering a single microenvironment factor, the hME‐ApoEV strategy effectively recapitulated the key features of the desired microenvironment in themselves, target cells and animal models via imprinting key features onto a simulated microenvironment generated by key cells in vitro. This strategy equips ApoEVs with complex microenvironment cues, amplifying their potency in regeneration medicine and providing a promising foundation for future microenvironment‐inspired ApoEV engineering strategies.