A Pilot Study Evaluating Combinatorial and Simultaneous Delivery of Polyethylenimine-Plasmid DNA Complexes Encoding for VEGF and PDGF for Bone Regeneration in Calvarial Bone Defects.

Gene therapy is a promising strategy to deliver growth factors of interest locally in a sustained fashion and has the potential to overcome barriers to using recombinant protein therapy such as sustainability and cost. Recent studies demonstrate the safety and efficacy of non-viral delivery of plasmid DNA (pDNA) encoding a single growth factor to enhance bone healing. This pilot study is aimed at testing a non-viral gene delivery system that can deliver two different plasmids encoding two different growth factors. Polyethylenimine (PEI), a cationic polymer, was utilized as a gene delivery vector and collagen scaffold was used as a carrier to deliver the PEI-pDNA complexes encoding platelet derived growth factor B (PDGF-B) and/or vascular endothelial growth factor (VEGF). Calvarial defects in rats were implanted with scaffolds containing PEI-pPDGF-B complexes, PEI-pVEGF complexes or containing both PEIpPDGF- B and PEI-pVEGF complexes in a 1:1 ratio of plasmids. The results indicated that bone regeneration as measured using micro-CT and histological assessments was inferior in groups treated with PEI-(pPDGF-B + pVEGF) complexes, compared to defects treated with PEI-pPDGF-B complexes. This pilot study that explores the feasibility and efficacy of combinatorial non-viral gene delivery system for bone regeneration appears to provide a rationale for investigation of sequential delivery of growth factors at specific time points during the healing phases and this will be explored further in future studies.