A migrasome-based osteoinductive strategy: reprogramming the bone microenvironment for accelerated coupling of angiogenesis and osteogenesis

The spatiotemporal coupling of osteogenesis and angiogenesis mediated by type H vessels represents a fundamental mechanism in bone formation. Although macrophages, the key immunomodulatory cells in the bone microenvironment, are known to participate in the regulation of type H vessels, the underlying mechanisms still remain insufficiently understood. The role of migrasomes, a newly discovered class of substrate-anchored extracellular vesicles, in macrophage-type H vessel crosstalk during bone regeneration were investigated in this study. M2 macrophage-derived migrasomes (RAW-MS) were produced by stimulating RAW 264.7 cells with fibronectin (FN). In vitro experiments indicated that RAW-MS were internalized by recipient cells, thereby promoting anti-inflammatory macrophage polarization, enhancing angiogenic activity, and facilitating osteogenic differentiation. Proteomic analysis revealed that RAW-MS were enriched with numerous angiogenesis-associated proteins. Transcriptome sequencing and subsequently in vitro experiments demonstrated that RAW-MS activated the endothelial tip cells phenotype and sprouting angiogenesis via TGFβ1/Smad2 signaling pathway. When incorporated into GelMA hydrogels, RAW-MS significantly improved vascularized bone regeneration in a critical-sized rat cranial defect model. Both in vitro and in vivo investigations consistently showed that RAW-MS enhanced the coupling of angiogenesis and osteogenesis accompanied by an increased density of type H vessel formation through upregulation of the TGFβ1/Smad2 signaling. In conclusion, this study highlighted the potential of migrasomes as innovative signaling vehicles for manipulating the regenerative microenvironment in tissue engineering.