Cryopreservation of pig trachea

Abstract

A method of graft preservation is essential if tracheal allografts are to become an option in reconstructing long, circumferential defects. This study evaluated the effect of cryopreservation on tracheal grafts. Eight 6-ring tracheal segments obtained from sacrificed pigs were cryopreserved for 2 months at-196°C by a standard low-freezing technique. Once thawed, 5 were examined histologically (group A) and 3 were wrapped with omentum and then implanted in the peritoneum of a donor pig (group B). Grafts were examined 1 month later. In 10 piglets (group C), a 4-ring segment of cervical trachea was removed and the defect closed by primary anastomosis. The graft was cryopreserved for 7 days, thawed, then reimplanted by dividing the thoracic trachea and interposing the cryopreserved trachea wrapped with omentum. Three piglets developed respiratory distress and were killed after 7 to 20 days; the remaining 7 were killed after 1 month. The grafts were rigid in groups A and B. Chondrocytes were present in group A, but in group B ghost cells were noted. Group C grafts were less rigid than the normal trachea although they did not collapse. Microscopically, cartilage had been replaced by fibrous tissue. Cryopreservation failed to maintain the viability of chondrocytes. However, the resulting fibrous trachea may prove to be a satisfactory alternative for replacement of longitudinal defects such as those created by tracheoplasty to treat congenital tracheal stenosis.