Experimental tracheal and tracheoesophageal allotransplantation. Paris-Sud University Lung Transplantation Group

We investigated the effects of allograft perfusion with a preservative technique and of combined thyrotracheoesophageal implantation on airway epithelium of long segments of thyrotracheal grafts allotransplanted on their own vascular pedicles into immunosuppressed pigs. Four groups of five animals each underwent heterotopic (into the neck) thyrotracheal (group 1) and thyrotracheoesophageal (group 2) and orthotopic thyrotracheal (group 3) and thyrotracheoesophageal (group 4) allotransplantation. Allograft revascularization included (1) interposition of donor right subclavian artery--incorporating the inferior thyroid artery--to recipient right carotid artery (end-to-end fashion) and (2) end-to-side anastomosis of donor anterior vena cava to recipient right external jugular vein. All thyrotracheoesophageal blocks were harvested after inferior thyroid artery perfusion with 4 degrees C Euro-Collins solution. The overall lengths of tracheal and esophageal grafts were 10.7 +/- 2.7 cm and 13.4 +/- 3.6 cm, respectively. In the heterotopic groups, all allografts were viable and histologically normal at postmortem examination and the incidence and severity of airway ischemia and rejections (at equal residual levels of cyclosporine) were not different between groups 1 and 2. In the orthotopic groups, the first two pigs died of airway collapse with histologically normal grafts. In the remaining pigs, temporary airway stenting was inserted and allografts remained viable and histologically intact for their entire length 30 days after transplantation. Transplanted tracheal smooth muscles had concentration-dependent contractions and relaxations similar to those of nontransplanted (native) tracheas. This study documents the feasibility of allotransplanting long tracheal and esophageal segments on their own vascular pedicles and demonstrates that allograft preservation and thyrotracheoesophageal transplantation are equally effective in minimizing airway ischemia. Thyrotracheoesophageal transplantation does not enhance recipient alloimmune response compared with thyrotracheal transplantation alone.