Comparison between slow and rapid freezing for adrenal gland cryopreservation and xenotransplantation

The aim of our study was to examine whether slow or rapid cryopreservation of adrenal xenografts affected xenotransplant outcome. Adrenal xenografts were got from newborn piglets (<24 h after birth). Receptor rats were randomly divided into four groups: a bilateral adrenalectomy group, fresh xenotransplantation group, rapid cryopreservation xenotransplantation group, and a slow cryopreservation xenotransplantation group. 30 days after xenotransplantation, the survival rates of rats in the fresh xenotransplantation group, rapid cryopreservation xenotransplantation group and slow cryopreservation xenotransplantation group were 80 %, 60 % and 60 %, respectively, which were significantly higher than 40 % of the bilateral adrenalectomy group. In addition, the survival rate of rats in the slow cryopreservation group was consistently significantly higher than that in the rapid cryopreservation group at 29 days after xenotransplantation. Morphological observation showed that there were a few medulla cells existed in the adrenal glands in the slow cryopreservation group after 30 days of xenotransplantation, but no medulla cells were found in the rapid cryopreservation group. The plasma cortisol level of rats in the fresh xenotransplantation group and the slow xenotransplantation group 30 days after xenotransplantation was significantly higher than that of the rapid cryopreservation group and bilateral adrenalectomy group (P < 0.05). The levels of liver glycogen and cholesterol in the xenotransplantation rats were increased relative to those of the bilateral adrenalectomy rats, and close to normal level. In conclusion, compared with rapidly frozen preserved grafts, slowly frozen preserved grafts not only ensure the structural integrity of adrenal tissues, but also have corresponding physiological functions, which provid a basic research opportunities for the preservation of xenografts and the treatment of adrenal corticosteroid deficiency. Moreover, these findings can provide evidence for xenotransplantation in the treatment of Addison's disease (adrenal cortex hormone deficiency).