Growth and development of homograft tracheal transplants in the piglet model.

OBJECTIVE

To determine the growth characteristics of homograft tracheal transplants 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 treated 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 tracheofissure, no transplant, and surgical placement of the stent. Three other control 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 viability indicated by cartilage retention.

RESULTS

The mean diameter of the tracheae in the stented tracheal transplant group was 11.7 mm before transplantation and 6.6 mm 2 months after transplantation. The transplanted segments were significantly malacic 2 months after transplantation. The mean diameter of the tracheae in the tracheofissure group was 9.0 mm before surgery and 11.0 mm 2 months after surgery. The 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 homografts showed evidence of extensive resorption of the graft cartilage. The graft cartilage was replaced by collagen, with minimal evidence of neochondrification. There was no evidence of host-vs-graft rejection. All grafted trachea had severe tracheomalacia with granulation tissue.

CONCLUSIONS

Homograft tracheal transplantation results in a tracheal segment that is replaced with collagen. The transplanted cartilage is resorbed, leaving a significantly malacic segment. Homograft tracheal transplantation might result in a small malacic airway with little potential for growth when performed in children.