Engineering 3D-BMSC exosome-based hydrogels that collaboratively regulate bone microenvironment and promote...

Large bone defects are a significant clinical challenge due to their frequent failure to heal spontaneously. Recently, BMSC-derived exosomes (Exo) based cell-free bone regeneration offer several distinct advantages over BMSCs themselves in the repair of damaged tissue, including enhanced repair ability and superior biocompatibility, which can be further augmented under 3D-cultured conditions. However, their therapeutic efficacy for bone regeneration is significantly constrained by hypoxic bone microenvironment and short retention time in bone defect region. Thus, judiciously regulating bone microenvironment and extending retention time are crucial for bone regeneration. Herein, we developed Superparamagnetic Iron Oxide Nanoparticles (SPION) -modified 3D-cultured Exo, termed as 3D-SExo, to enhance Reactive Oxygen Species (ROS) scavenging and promote bone regeneration in response to the needs of bone defect. After entrapment in bone-targeting peptide-modified GelMA (Gel-DSS6), the composite hydrogel (3D-SExo/DGel) was obtained, which can prolong the retention of exosomes, and thereby enhancing bone repair ability. In addition, miR-122-5p, detected via microRNA (miRNA) array from 3D-cultured Exo, were observed to promote osteogenesis by activating Wnt/β-catenin pathway, which was further verified by miRNA transfection. Through the in vitro and in vivo studies, 3D-SExo/DGel could decompose ROS to relive hypoxia and alleviate the inhibitory effect of ROS on β-catenin production, demonstrating significant clinical therapeutic potential to improve cell-free bone regeneration.