Maximal period of cryopreservation with the bicell biofreezing vessel for rat tracheal isografts

Objective: The maximal period of cryopreservation for the trachea is still unsolved, We assessed the maximal period of cryopreservation using the Bice ll biofreezing vessel as an easy and cheap slow-freezing instrument for via ble tracheal grafts in 95 rats. Methods: Each isograft was harvested from 1 7 donor rats, immersed in the preservative solution, and stored in a Bicell device in a deep freezer at -80 degrees C. The tracheal isografts were the n randomly assigned to 9 groups according to cryopreservation periods rangi ng from 0 to 12 months. Included in the 9 groups were 2 subgroups (n = 6 pe r subgroup) that were observed immediately after being thawed and 1 month a fter heterotopic transplantation into the omentum after being thawed. Four subgroups (n = 6 per subgroup) were added according to the cryopreservation period for 1, 3, 6, and 12 months to evaluate the graft morphology 3 month s after being thawed and transplanted heterotopically, Results: A prolonged period of cryopreservation had a degenerative effect on both the epitheliu m and cartilage. One month after transplantation, degeneration was more pro nounced in the cartilage than in the epithelium, as characterized by the vi able chondrocyte ratio and the epithelial score of isografts undergoing cry opreservation for more than 9 months. Three months after transplantation, t he morphology of the epithelium and cartilage in isografts undergoing cryop reservation for less than 3 months was better preserved, whereas the morpho logy of both deteriorated in isografts undergoing cryopreservation for more than 6 months. Conclusions: We conclude that the permissible period of cry opreservation to maintain tracheal isograft viability in this simple system using a Bicell biofreezing vessel is 3 months.