Experimental Tracheal Replacement Using a Revascularized Ileal Segment for Transplantation in Rats

Abstract

The clinical field of tracheal reconstruction is still the subject of intensive investigation. Numerous attempts to replace extensive circumferential tracheal defects have failed to demonstrate long-lasting reliable results. Commonly used alloplastic prostheses are missing a mucosal barrier which clears mucus secretions and protects against contamination by infectious organisms. Tissue granulation and formation of scar strictures at the suture lines are common sequels and mainly contribute to graft failure. We hypothesized that the small bowel could adapt and comply with the functional and physiological requirements of the respiratory tract. To further clarify this study objective, a "two-step" surgical procedure was carried out on LEW inbred rats. First, an ileal segment 6 cm in length was dissected from the intestinal continuity. The divided segment was then sidepassed in a Roux-en-y fashion. The exposed segment was stabilized by a ring-enforced PTFE (polytetrafluoroethylene) prosthesis which was cut open and wrapped around the antimesenteric outside surface of the bowel segment. After 21 days the alloplastic prosthesis was completely incorporated into the adjacent small bowel tissue. Afterward, a tracheal resection of 10 cartilage rings was performed in a second syngeneic animal and the composite graft prepared in animal one was interposed for reconstruction in animal two. In a series of 10 successful experiments, air tightness and a normal respiratory tract without signs of mucus congestion could be confirmed. A gap-free epithelial lining at the suture lines reliably prevented bacterial contamination, subsequent tissue granulation, and formation of scar stricture within the graft. Incorporation of the PTFE prosthesis into the muscle layer of the adjacent small bowel provided efficient stability to avoid graft collapse. In addition, histological examination demonstrated induction of neocartilage, originating from giant cells lining the boundary between the small bowel muscle layer and the PTFE meshgraft. However, transient stenting was necessary to omit stenosis due to postoperative mucosal edema. Based on these results, we conclude that the adaptive potency of the investigated composite graft meets the functional and physiological needs of the respiratory tract and offers efficient suitability for the replacement of long segmental defects of the trachea. Above all, our findings encourage further long-term investigations, also in higher vertebrates.