Growth and development of homograft tracheal transplants in the piglet model

Objective: To determine the growth characteristics of homograft tracheal tr ansplants in piglets. Design: Prospective controlled animal study. Setting: Clinical animal laboratory. Subjects: Seventeen Yorkshire swine piglets. Interventions: The tracheae of adult Yorkshire swine were harvested and tre ated with formaldehyde, thimerosal, and acetone to remove immunogenic major histocompatibility complexes. Eleven piglets had these chemically treated homografts transplanted into 6-cm surgically created tracheal defects. The transplants were stented.. Three control piglets had a 6-cm anterior trache ofissure, no transplant, and surgical placement of the stent. Three other c ontrol piglets had no transplant, and the stent was placed endoscopically. Main Outcome Measures: Growth outcome measurements were tracheal length and diameter. Functional outcome measurements were lumen patency and graft via bility indicated by cartilage retention. Results: The mean diameter of the tracheae in the stented tracheal transpla nt group was 11.7 mm before transplantation and 6.6 mm 2 months after trans plantation. The transplanted segments were significantly malacic 2 months a fter transplantation. The mean diameter of the tracheae in the tracheofissu re group was 9.0 mm before surgery and 11.0 mm 2 months after surgery. Thf mean diameter of the tracheae in the endoscopically stented group was 11.0 mm before surgery and 14.0 mm 2 months after stent placement. All homograft s showed evidence of extensive resorption of the graft cartilage. The graft cartilage was replaced by collagen, with minimal evidence of neochondrific ation. There was no evidence of host-vs-graft rejection. All grafted trache a had severe tracheomalacia with granulation tissue. Conclusion: Homograft tracheal transplantation results in a tracheal segmen t that is replaced with collagen. The transplanted cartilage is resorbed, l eaving a significantly malacic segment. Homograft tracheal transplantation might result in a small malacic airway with little potential for growth whe n performed in children.