The effect of platelet-derived growth factor on tracheal wound healing

In order to evaluate a new method for the direct application of a polypeptide growth factor to injured tracheal epithelium and to determine the effect of topical platelet-derived growth factor (PDGF) on tracheal wound healing, a controlled animal study was designed using six adult beagle dogs. Four 2×1 cm mucosal defects were created in the tracheal lumen of each dog for a total of 24 experimental sites. Twelve wounds were treated with PDGF in a collagen–fibrin composite tissue adhesive (CTA) carrier. Eight sites received CTA alone and four were left untreated. Healing was assessed by endoscopic exam on post-operative days 4, 7, 10, 14, 17 and 21. The animals were sacrificed on day 21 and the tracheas were harvested for histological examination of the experimental sites and adjacent unwounded trachea. By 21 days, complete healing of all sites was observed endoscopically. Wounds treated with CTA or PDGF-CTA healed at a faster rate than control sites. The PDGF-CTA treated wounds demonstrated excessive granulation tissue formation. Histological examination demonstrated a higher percentage of wound coverage with ciliated epithelium most similar to normal trachea in the PDGF treated wounds. CTA is effective as a carrier for the direct delivery of a growth factor to injured tracheal epithelium. The application of CTA or PDGF-CTA results in a more rapid rate of tracheal wound healing as compared with control wounds. PDGF-CTA led to increased acute local inflammatory changes but was associated with a structurally more normal respiratory epithelium after healing. Physiological studies are necessary to determine the functional significance of these findings.