PLATELET-DERIVED GROWTH-FACTOR INHIBITS BONE REGENERATION INDUCED BY OSTEOGENIN, A BONE MORPHOGENETIC PROTEIN, IN RAT CRANIOTOMY DEFECTS

Platelet-derived growth factor (PDGF) is a potent moderator of soft ti ssue repair through induction of the inflammatory phase of repair and subsequent enhanced collagen deposition. We examined the effect of rec ombinant BB homodimer PDGF (rPDGF-BB) applied to rat craniotomy defect s, treated with and without bovine osteogenin (OG), to see if bone reg eneration would be stimulated. Implants containing 0, 20, 60, or 200 m ug rPDGF-BB, reconstituted with insoluble rat collagenous bone matrix containing 0, 30, or 150 mug OG, were placed into 8-mm craniotomies. A fter 11 d, 21 of the 144 rats presented subcutaneous masses superior t o the defect sites. The masses, comprised of serosanguinous fluid enca psulated by fibrous connective tissue, were larger and occurred more f requently in rats treated with 200 mug rPDGF-BB, and were absent in ra ts not treated with rPDGF-BB. The masses underwent resorption within 2 8 d after surgery. OG (2-256 mug) caused a dose-dependent increase in radiopacity and a marked regeneration of calcified tissue in a dose-de pendent fashion within defect sites. However, OG-induced bone regenera tion was inhibited 17-53% in the presence of rPDGF-BB. These results s uggest that rPDGF-BB inhibited OG-induced bone regeneration and stimul ated a soft tissue repair wound phenotype and response.