Effects of rhBMP-2/7 Heterodimer and RADA16 Hydrogel Scaffold on Bone Formation During Rabbit Mandibular Distraction.

PURPOSE: The effects of a recombinant human bone morphogenetic protein-2/7 (rhBMP-2/7) heterodimer and a RADA16 (Ac-RADARADARADARADA-CONH2) hydrogel scaffold on bone formation during distraction osteogenesis were evaluated.

MATERIALS AND METHODS: Forty New Zealand white rabbits, which underwent mandibular lengthening, were randomly divided into 5 groups. One group served as the control group. The others received 2 μg of rhBMP-2 homodimer, 2 μg of rhBMP-2/7 heterodimer, 100 μL of RADA16, or 100 μL of RADA16 plus 2 μg of rhBMP-2/7 heterodimer in the mandibular distraction gap at the beginning of distraction. Fluorine-18-labeled fluoride positron emission tomography was used to assess osteogenesis both after distraction and at the end of consolidation. Dual-energy x-ray absorptiometry (DEXA) examination and bone histologic findings were also evaluated.

RESULTS: At the end of distraction, the radioactivity concentration in the distracted area was significantly greater in the RADA16 plus rhBMP-2/7 heterodimer group than in the other groups (P < .01). The differences among the other 4 groups were also statistically significant in the following order: rhBMP-2/7 heterodimer group greater than the rhBMP-2 homodimer group, which was greater than the RADA16 group (or control group; P < .05). However, the radioactivity concentration of the RADA16 group was slightly greater than that of the control group with a nonsignificant difference (P > .05). By the end of consolidation, the activity in the control group, RADA16 group, rhBMP-2 homodimer group, and rhBMP-2/7 heterodimer group had significantly diminished (P < .05). However, the activity in the RADA16 plus rhBMP-2/7 heterodimer group remained at the same level (P > .05). The DEXA results and bone histologic findings indicated that more callus regeneration was noted in the RADA16 plus rhBMP-2/7 heterodimer group than in any other group.

CONCLUSIONS: The use of rhBMP-2/7 heterodimer and RADA16 hydrogel scaffold significantly promoted mandibular distraction osteogenesis.