GROWTH FACTOR-INDUCED ACCELERATION OF TISSUE-REPAIR THROUGH DIRECT AND INDUCTIVE ACTIVITIES IN A RABBIT DERMAL ULCER MODEL

The roles of polypeptide growth factors in promoting wound healing and in directing the specificity and sequence of responses of different tissues in wounds are little understood. We investigated the influence of four growth factors on the rates of healing of a novel full thickness dermal ulcer placed on an avascular base in the rabbit ear. The wound model precludes significant wound contraction and requires new granulation tissue and epithelial cells for healing to originate centripetally. 5-mu-g (7-31 pmol/mm2) of platelet-derived growth factor-B chain (PDGF-BB), basic fibroblast growth factor (bFGF), and epidermal growth factor (EGF) applied locally at the time of wounding resulted in a twofold increase in complete reepithelialization of treated wounds (PDGF-BB, P = 0.02 chi square analysis; bFGF, P = 0.04; EGF, P = 0.05); transforming growth factor (TGF)-beta-1 significantly inhibited reepithelialization (P = 0.05). Both PDGF-BB and TGF-beta-1 uniquely increased the depth and area of new granulation tissue (P < 0.005), the influx of fibroblasts, and the deposition of new matrix into wounds. Explants from 7-d old PDGF-BB-treated wounds remained metabolically far more active than controls, incorporating 473% more [H-3]thymidine into DNA (P = 0.05) and significantly more [H-3]leucine and [H-3]proline into collagenase-sensitive protein (P = 0.04). The results establish that polypeptide growth factors have significant and selective positive influences on healing of full thickness ulcers in the rabbit.