An investigation of airway wound healing using a novel in vivo model

Objective: To study the amount of wound contraction and reepithelealization occurring in the healing process of full-thickness mucosal defects treated with and without mitomycin, Study Design: A new wound healing model was de veloped in which the tracheal mucosa was exteriorized without interference with the blood supply or with the cartilage support of the trachea. This wa s done by: 1) orthotopic tracheal revascularization in vascularized fascia; 2) isolation of revascularized segment after 14 days; 3) posterior longitu dinal incision of revascularized segment; 4) exteriorization of tracheal mu cosa with formation of anterior full-thickness mucosal defect; and 5) closu re of posterior tracheal incision and reimplantation in the airway. This mo del was used to study ah-way wound healing in three groups of animals: 1) c ontrols (revascularization, exteriorization, reimplantation) (N = 6); 2) fu ll-thickness mucosal defect: patch defect (N = 5), circumferential defect ( N = 3); and 3) full-thickness mucosal defect after topical mitomycin applic ation: patch defect (N = 7), circumferential defect (N = 3). The animals we re followed for periods varying from 2 to 4 weeks or until signs of dyspnea , The surface areas of the wounds before and after follow-up were measured Wound healing was studied histologically on axial and longitudinal sections . Results: Group 1: Ah the animals survived for 1 month. No significant dif ference existed between surface area of isolated trachea and of reimplanted trachea after follow-up. Group 2: Five animals (patch defects) survived fo re 1 month. Full-thickness mucosal defects healed by reepithelialization an d by a surface area reduction of 58.9% (mean - standard deviation = 10.5), The animals with the circumferential defects showed dyspnea after an averag e follow-up of 14 days as a result of excessive granulation tissue formatio n. Group 3: Mitomycin reproducibly inhibited wound closure, yielding wounds that on average closed 56% less than controls by day 14 (P < .001), Histol ogic comparisons showed that mitomycin blocks angiogenesis during wound hea ling Conclusions: A wound healing model based on tracheal revascularization , isolation, and reimplantation was developed in rabbits. This model allowe d us to study the healing of full-thickness mucosal defects inside the airw ay.