Tunable co-delivery of VEGF and BMP2 mimetic peptides to enhance bone regeneration

University Of Alabama At Birmingham, Birmingham AL

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Abstract

Project Summary/Abstract Current bone grafting materials such as allograft and alloplast have limited osteoinductivity. The proposed research aims to reintroduce bone-healing factors to these materials to improve bone regeneration. Our group has identified a polyglutamate domain that can be added to growth factor mimetic peptides to control the binding and release of the peptides from calcium-containing bone grafting materials. In the proposed research, we will use variable-length polyglutamate domains (E2, E4, & E7) to create a gradient release of the proangiogenic QK peptide (angiogenic signaling domain of VEGF) known as PGM-QK from bone grafts. We hypothesize that the controlled release of PGM-QK will increase vascularization within the implant site, thereby improving bone regeneration. In addition to PGM-QK peptide delivery, we will investigate the co-delivery of PGM-QK with the osteogenic peptide, E7-BMP2pep. In previous studies, E7-BMP2pep delivered on grafting material was able to localize within the injury site and induce an osteogenic response comparable to rBMP-2, without any deleterious side effects. We propose that co-delivery of these two therapeutics on bone grafts will greatly enhance new bone synthesis. In this proposal, there are two major objectives: (1) develop a gradient release of PGM-QK from bone grafts to induce angiogenesis, and (2) co-deliver PGM-QK and E7-BMP2pep on bone grafting materials to accelerate bone regeneration. AIM 1: Use of PGM-QK peptides to stimulate angiogenic endothelial cell behavior. Aim 1 will develop a gradient release of PGM-QK from bone grafting materials to elicit proangiogenic endothelial cell responses including migration and tubule formation. As well, graft materials with PGM-QK will be evaluated for angiogenic potential using the chorioallantoic membrane assay. We postulate that controlled release of PGM- QK peptide from grafting materials will elicit greater neovascularization compared with rVEGF and QK peptide. AIM 2: Co-delivery of PGM-QK and E7-BMP2pep peptides to stimulate bone regeneration. Bone grafts treated with PGM-QK will be implanted into subcutaneous pouches to evaluate vascularization from gradient release of PGM-QK. In addition, bone grafts coated with both PGM-QK and E7-BMP2pep will be implanted into cranial defects to determine whether increased vascularization mediated by PGM-QK improves osteogenesis. Excised tissue will be evaluated for angiogenesis, new bone formation, immune and foreign body response, and fibrosis. We hypothesize that the osteogenic potency of E7-BMP2pep in conjunction with the increased vessel network formed in response to PGM-QK peptide will greatly accelerate bone regeneration mediated by bone grafting materials.