EFFECT OF PLATELET-DERIVED GROWTH FACTOR-BB ON BONE-FORMATION IN CALVARIAL DEFECTS - AN EXPERIMENTAL-STUDY IN RABBITS

The effect of recombinant human platelet-derived growth factor-BB (rhP DGF-BB) on bone healing was examined in calvarial defects in rabbits. Bicortical circular (critical size) defects were prepared in the calva rial bone of 16 rabbits. The defects were closed on the dural side and covered externally with expanded polytetrafluoroethylene membranes to prevent interference with osteogenesis within the defect by the surro unding tissue and to keep the growth factor in place. A single dose of methylcellulose gel (4.4%) with (n = 8) or without rhPDGF-BB (50 mu g /ml) (n = 8) was applied to the defects, and the bone formation was ev aluated after 8 weeks. Healing of defects in both groups was character ized by the presence of newly formed bone along the edges of the origi nal defect and by a central area of fibrous connective tissue. The new ly formed bone in the rhPDGF-BB treated defects had a trabecular struc ture; in contrast, a more compact structure was found in the control d efects. In the rhPDGF-BB-treated defects, the bone ingrowth was 51.8 /- 7.1% compared to 30.5 +/- 3.3% in the control defects. Furthermore, the amount of mineralized tissue was increased 112% in the rhPDGF-BB group. The amount of bone marrow was increased 75% in the rhPDGF-BB-tr eated defect. The porosity of cortical lamella in the newly formed bon e was 84% higher in the rhPDGF-BB-treated defects compared to the cont rol. These results show that administration of a single dose of rhPDGF -BB stimulates bone formation in critical size calvarial defects.