Tracheal cryopreservation: caspase-3 immunoreactivity in tracheal epithelium and in mixed glands

Cryopreservation has an immunomodulating effect on tracheal tissue as a result of class II antigen depletion due to epithelium exfoliation. However, not all epithelium is detached. We evaluated the role of apoptosis in the remaining epithelium of 30 cryopreserved tracheal grafts. Caspase-3 immunoreactivity of tracheal epithelium was studied in canine tracheal segments cryopreserved with F12K medium, with or without subsequent storage in liquid nitrogen at -196°C for 15 days. Loss of structural integrity of tracheal mixed glands was observed in all cryopreserved tracheal segments. Caspase-3 immunoreactivity in tracheal mucosa and in mixed glands was significantly decreased, in contrast to the control group and to cryopreserved tracheal segments in which it remained high, due to the effect of storage in liquid nitrogen (P < 0.05, ANOVA and Tukey test). We conclude that apoptosis can be triggered in epithelial cells during tracheal graft harvesting even prior to cryopreservation, and although the epithelial caspase-3 immunoreactivity is reduced in tracheal cryopreservation, this could be explained by increased cell death. Apoptosis cannot be stopped during tracheal cryopreservation.

Protective mechanism of trehalose in tracheal cryopreservation / 中国海洋药物

Objective To detect the protective mechanism of trehalose in tracheal cryopreservation.Methods Inbred male Sprague-Dawley (SD) rats were sacrificed with intraperitoneal injection of ketamine(150mg?kg -1).The tracheas were removed and immersed immediately in the freezing medium of low potassium dextran (LPD) solution only(Group Ⅰ) ,containing with 10% dimethylsulfoxide(DMSO)(Group Ⅱ), containing with 0.15mol?L -1 trehalose (Group Ⅲ),and containing with 10% DMSO and 0.15mol?L -1 trehalose (Group Ⅳ) respectively. A sterile plastic tube containing a 1-cm-long trachea was filled with the freezing medium,sealed,and frozen to -80℃ at rate of -1℃ per minute in a programmable freezer.Then the tube was stored in liquid nitrogen(-196℃) for 20 days. Then the specimen was thawed in a 37℃ water bath and rinsed with physiologic saline solution 10 times.Histologic changes before cryopreservation and after thawing were examined in each group. After the specimens were embedded in paraffin,5-(m-thick sections were stained with hematoxylin and eosin.The epithelium and cartilage was assessed. We also observed Bcl-2 and Bax gene expression by immunohistochemistry. At last, some tracheas(SD) after cryopreservation were thawed and transplanted into the abdominal cavity of Wistar rats. The transplanted tracheas were retrieved and assessed histologically.Results Microscopic findings of the tracheas in Group Ⅲ and Group Ⅳ showed their structure were intact and Bax gene expression was lower in cartilage after cryopreservation(20d) compared with other groups,especially in Group Ⅳ.The tracheas in Group Ⅲ and Group Ⅳ grew well after they were transplanted into cavity of Wistar rats heterotopically,too.There were no significant differences among 4 groups in Bcl-2 gene expression.Conclusion In tracheal cryopreservation the trehalose can protect the trachea by protecting the tracheal cartilage.It is one of the protective mechanism that the trehalose inhibit the Bax gene expression of cartilage cells.The concomitant use of trehalose and DMSO has a synergistic effect.