Effect of gene transfecting at different times on mandibular distraction osteogenesis

Recently, numerous research of gene therapy for mandibular distraction has been published. Based on previous study, the authors used New Zealand rabbits bilateral mandibular distraction model and used electroporation mediate gene therapy at different time, to explore the optimal time for gene therapy and obtain a better effect.

Forty-eight New-Zealand rabbits were used; after accomplished osteotomy and implant distraction devices on mandible bilaterly, the rabbits were randomly divided into 4 groups: groups A, B, and C were transfected recombinant plasmids pIRES-hBMP2-hVEGF165 via electroporation-mediated approach at latency period, distraction period, and consolidation period, respectively. Group D is a control group, only distracted without gene transfection. After 3 days of latency period, the device was activated at the rate of 1 mm per day for 10 days. Three rabbits of each group were sacrificed at 1, 2, 4, and 8 weeks of consolidation, respectively. The mandibles were harvested; the left was subject to radiograph examination for bone healing, and quantitative computed tomography detect for the bone mineral density (BMD) of newly formed bone in the distraction gap. The biomechanical properties of the new generation bone at the fourth and eighth weeks of consolidation of each group were detected using 3-point bending test.

The BMD and the stiffness of newly formed bone increased with the pass of the consolidation time in each group. After 1 week of consolidation, there is no significant difference of BMD among groups A, B, and C. However, the BMD of groups A, B, and C is higher than that of group D. After 2, 4, and 8 weeks of consolidation, the BMD of group B is significantly higher than those of groups A, C, and D. The biomechanical parameters are also higher in group B than those of groups A, C, and D after 4 and 8 weeks of consolidation.

It is better to transfect gene at distraction period than at other stages of DO; in this way, we can obtain more remarkable effect on new bone formation. It suggests that the distraction stage is the optimal time for gene therapy.