OP3-4 peptide sustained-release hydrogel inhibits osteoclast formation and promotes vascularization to promote bone regeneration in a rat femoral defect model.

Bone injury caused changes to surrounding tissues, leading to a large number of osteoclasts appeared to clear the damaged bone tissue before bone regeneration. However, overactive osteoclasts will inhibit bone formation. In this study, we prepared methacrylylated gelatin (GelMA)-based hydrogel to co-crosslink with OP3-4 peptide, a receptor activator of NF-κB ligand (RANKL) binding agent, to achieve the slow release of OP3-4 peptide to inhibit the activation of osteoclasts, thus preventing the long-term existence of osteoclasts from affecting bone regeneration, and promoting osteogenic differentiation. Moreover, CXCL9 secreted by osteoblasts will bind to endogenous VEGF and inhibit vascularization, finally hinder bone formation. Thus, anti-CXCL9 antibodies (A-CXCL9) were also loaded in the hydrogel to neutralize excess CXCL9. The hydrogel slow released of OP3-4 cyclic peptide and A-CXCL9 to simultaneously inhibiting osteoclast activation and promoting vascularization, thereby accelerating the healing of femur defect. Further analysis of osteogenic protein expression and signal pathways showed that the hydrogel may be through activating the AKT-RUNX2-ALP pathway and ultimately promote osteogenic differentiation. This dual-acting hydrogel can effectively prevent nonunion caused by low vascularization and provide long-term support for the treatment of bone injury.