Cryopreservation of canine trachea: functional and histological changes

The purpose of this study was to evaluate tracheal viability and to document histological changes in an autograft implanted in the abdominal wall after a 1-week period of cryopreservation. A 5-cm segment of cervical trachea was resected in 6 dogs. One-half of the segment was cryopreserved and stored in liquid nitrogen at -196 degrees C for 1 week. The other half was immediately implanted in an abdominal pouch fashioned from the rectus abdominis muscle (control). One week later, the cryopreserved segment was thawed and then implanted in a similar contralateral muscular pouch. Five weeks later, the control and cryopreserved autografts were removed and compared with the in situ trachea. Ciliary beat frequency was assessed by transmitted light technique. Histology was evaluated by light microscopy. Gross anatomy and mucus production were maintained after cryopreservation. Histologically the cryopreserved segment displayed both normal epithelium and smooth muscle cells, but the cartilage was abnormal as characterized by empty lacunae. Mean ciliary beat frequency of in situ, control, and cryopreserved segments was 13.3 +/- 1.8, 13.5 +/- 1.5, and 13.3 +/- 1.1 beats per second (+/- the standard deviation), respectively. We conclude that smooth muscle, epithelium with mucus production, and ciliary function were retained after cryopreservation and reimplantation. Histological changes, however, were suggestive of early cartilage ischemia. These findings support further evaluation of cryopreserved canine tracheal grafts.