An injectable microsphere-reinforced system for sustained delivery of Adipo-MBV in adipose tissue engineering

• Both C-AT-MBVs and M-AT-MBVs showed the typical characteristics of EVs. • M-AT-MBVs owned multiple miRNAs involved in cell cycle regulation and stem cells pluripotency. • M-AT-MBVs promoted adipogenesis, tube formation and cell migration in vitro . • Adipo-MBVs could be sustainedly released by PDA@HMs, and hybrid hydrogel could be injected smoothly. • Both C-AT-MBVs and M-AT-MBVs enhanced adipose tissue formation in vivo . • Construction of engineering adipose tissue in hybrid hydrogel grafts assisted by M-AT-MBVs was superior to those assisted by C-AT-MBVs. Tissue engineering has become prominence in soft-tissue reconstruction. Adipogenesis and angiogenesis are important in the formation of engineering adipose tissue. Although acellular adipose matrix (AAM) possesses potential in adipogenic induction, obvious limitations remain in the realization of the authentic physiological regeneration. Matrix-bound nanovesicles (MBVs), located on the extracellular matrix (ECM) scaffold, provide cues for the adipogenesis property of AAM. The bioactive components within ECM are influenced by the isolation procedures. This study aimed to extract and identify adipose-derived MBVs (Adipo-MBVs) from adipose ECM scaffolds and clarify their effective role in engineering adipose tissue formation. Adipo-MBVs were extracted from two types of adipose ECM, including chemically decellularized matrix (i.e. AAM) and mechanically concentrated ECM (i.e. adipose collagen fragment, ACF). The influence of Adipo-MBVs on cell functions were estimated in vitro . In addition, AAM-hyaluronic acid methacrylate (HAMA) hybrid hydrogel (A/H) with polydopamine (PDA)-coated HAMA microspheres (PDA@HMs) was designed to sustainedly release Adipo-MBVs in an animal model. The results showed that Adipo-MBVs effectively recapitulated AAM effects on the construction of engineering adipose tissue. Crucially, mechanical Adipo-MBVs (M-AT-MBVs) derived from mechanically concentrated ECM exhibited a significantly stronger capacity to induce both adipogenesis and angiogenesis in vitro and in vivo , compared to chemical Adipo-MBVs (C-AT-MBVs) from chemically decellularized matrix. Furthermore, we developed a novel composite delivery system that ensured the sustained release of M-AT-MBVs and robustly promoted the regeneration of vascularized adipose tissue in a mouse model. This enhanced efficacy of M-AT-MBVs was associated with their distinct miRNA profile, particularly an enrichment of pro-adipogenic miR-143, and involved the downregulation of MAPK signaling pathway. This study demonstrated Adipo-MBVs as key regenerative components of adipose ECM. It is shown that mechanical isolation yields superior M-AT-MBVs, and our engineered delivery system presents a novel strategy for soft tissue regeneration.