Expression of growth factors in the mandibular distraction zone: a sheep study

Interest in craniofacial osteodistraction has increased in recent years parallel with the growing attention given to the role of growth factors in tissue healing and regeneration. This study was embarked upon to investigate the expression of bFGF, TGF-beta and IGF-1 in the distraction zone of the mandible. Fourteen growing sheep were allocated to three experimental groups. Six animals were allocated to Groups A and B (n = 12) and underwent bilateral mandibular corticotomies with fixation of an external lengthening device. The distraction protocol consisted of a rate of 1.0 mm/day (twice daily) for 20 days followed by a consolidation phase of 20 days after which the sheep were sacrificed. Group C comprised of age matched sham operated animals (n = 2). Bone histochemistry for growth factors were performed in the harvested mandibles. A strong staining of bFGF was seen in the osteoblasts, osteocytes and osteoid matrix following 20 days of distraction and 20 days of consolidation compared to the control group. TGF-beta and IGF-1 demonstrated mild but clear staining in osteocyte and osteoblast cells and TGF-beta stained positively in the osteoid seam in the experimental groups. These finding suggest that bFGF IGF-1 and TGF-beta may play different roles in the remodelling phase of distraction osteogenesis.