Heparin-conjugated injectable hydrogels with sustained releasing capability for promotion of H-type vessels formation and rat femoral bone defects repair

Adequate vascularization is crucial for the repair of bone defects. Platelet-derived growth factor-BB (PDGF-BB) has been shown to promote H-type vessel formation, a specialized blood vessel, strongly positive for CD31 and endomucin, coupling angiogenesis and osteogenesis. However, the lack of a controllable growth factor delivery limits its clinical application, causing certain complications associated with PDGF-BB administration. This study developed an injectable heparin-conjugated hydrogel (GHH) for controlled delivery to facilitate the effective binding of PDGF-BB and rapid vascularized bone regeneration. Herein, in vitro experiments involving the controlled release of PDGF-BB showed that the PDGF-BB-loaded GHH (GHHP) hydrogel demonstrated excellent cytocompatibility and osteogenic properties. The subcutaneous implantation model in rats revealed that the GHHP hydrogel has the potential to induce the formation of H-type blood vessels in vivo. Furthermore, the healing of distal femoral condyle defects in rat models in vivo demonstrated that GHHP could substantially promote H-type angiogenesis and effectively repair bone defects. Our injectable heparin-conjugated sustainedrelease PDGF-BB hydrogel has excellent angiogenic and osteogenic properties, thus providing a novel and promising solution for bone defect repair.