A composite hydrogel enables the spatiotemporal delivery of distinct cytokines to drive the native vascularized bone regeneration.

Bone defect represents one of the most prevalent clinical conditions in orthopedics diseases, and the key to successful therapeutic outcomes lies in achieving early vascularization coupled with late-phase osteogenic differentiation. Growth factor delivery is among the most widely adopted strategies for bone tissue regeneration. However, achieving the spatiotemporal coupled regulation of vascularized bone regeneration remains a major challenge. Proprotein convertase subtilisin/kexin type 9 (PCSK9) exerts a pivotal role in bone metabolism. Our preliminary findings demonstrated that PCSK9 expression is upregulated during bone regeneration, while the supplementation of exogenous PCSK9 can enhance the osteogenic differentiation of bone marrow mesenchymal stem cells (BMMSC). Based on these findings, we fabricated a composite hydrogel by adsorbing PCSK9 onto vascular-derived extracellular matrix (ECM) and incorporating vascular endothelial growth factor (VEGF) into gelatin methacryloyl (GelMA). Taking advantage of the distinct sustained-release profiles of these biomaterials, this hydrogel system was engineered to recapitulate the natural bone defect healing process, thereby enabling the coupled regulation of accelerated early vascularization and enhanced late-phase osteogenic differentiation. Both in vitro and in vivo experimental results confirmed that the constructed composite hydrogel can further potentiate the therapeutic efficacy of PCSK9 and achieve efficient vascularized bone regeneration. Mechanistically, our findings revealed that PCSK9 promotes the osteogenic differentiation of BMMSC via activation of the ERK signaling pathway. Collectively, the PCSK9- and VEGF-loaded composite hydrogel exhibits promising pro-angiogenic and pro-osteogenic coupling capabilities for bone regeneration, which provides novel therapeutic targets and innovative strategies for the clinical management of bone defects.