Our laboratory has shown the efficacy of bone morphogenetic proteins (BMPs) in healing critical-sized rat cranial defects. Gene therapy, however, offers a more efficient, sustained, and cost effective method of bone regeneration. This study investigated the bone regenerative ability of plasmid DNA encoding recombinant human bone morphogenetic protein-4 (rhBMP-4) administered with a biodegradable, biocompatible fabric, porous poly(D,L-lactide) and type 1 collagen (PLC). Uniform 8-mm calvaria defects were prepared in 150 rats divided into 5 treatment groups: 1. untreated critical-sized defect (negative control); 2. PLC only; 3. plasmid DNA rhBMP-4 only; 4. plasmid DNA rhBMP-4/PLC; 5. autogenous bone graft (positive control). Rats were sacrificed at 2, 4, and 8 weeks post surgery. Sacrifice time periods were based on data from previous studies. Quantitative analysis of bone formation included radiomorphometry and histomorphometry. Statistical significance was established at p<0.05. Treatment outcomes revealed statistically greater bone healing in the plasmid DNA rhBMP-4 with the bioresorbable carrier compared to the untreated group, the plasmid alone group, or the carrier alone group at 4 and 8 weeks. These results were consistent in both histomorphometry and radiomorphometry analyses. We also found significantly greater bone healing in the autogenous bone graft control group compared to the plasmid DNA rhBMP-4 with the bioresorbable carrier group. This study demonstrated plasmid DNA rhBMP-4 and a bioresorbable carrier can stimulate clinically relevant quantities of new bone growth to fill a critical-sized rat cranial defect. This treatment group was superior to the untreated defect, the carrier alone or the plasmid alone. This study provides important preliminary data for the development of juvenile canine and primate models of alveolar cleft bone healing.

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