Extract of ginkgo biloba leaves influences the harvesting and cryopreservation of rat islet cells

Background: A successful islet cell transplantation attributes to the harvesting of enough bio-active islet cells, and cryopreservation is a feasible way to collect islet cells, but cell apoptosis may occur in the procedure of cryopreservation and resuscitation. Objective: To explore the influence of the extract of ginkgo biloba leaves (EGB) on rat islet cells harvesting and function after cryopreservation. Design, time and setting: A randomized control animal study was performed in the Key Laboratory of Environment and Genes Related to Diseases (Xi'an Jiaotong University Medical College), Ministry of Education from October to December in 2007. Materials: Forty male SD rats were used in this study to isolate islet cells. Methods: Forty rats were divided into 2 groups at random (n=20). In EGB group, rats were injected with 25 mg/kg EGB via tail vein, and the islet harvesting was performed. Next, the islet cells were cultured in EGB-containing medium for 3, 7, 14 and 21 days (n=5) after cryopreservation and resuscitation. In control group, an intravenous injection of equal volume of saline was given, followed by the same time of cryopreservation and resuscitation in EGB group. Main outcome measures: Cell morphology under electron microscopy; Detection of apoptosis by terminal dUTP nick end labeling (TUNEL); Immunohistochemical detection of Bcl-2 expression. Results: 1 The loss rate of cells after resuscitation in the EGB group was obviously lower than that in the control group (P < 0.05). 2 Compared with the control group, the endocrine particles and zymogen granules increased more significantly in the EGB group after islet cells were cultured for 3 days. 3 After 21 days of resuscitation culture, 45% of islet cells in EGB group survived, while the survival rate of cells in the control group was less than 35%, there were significant differences between the two groups (P < 0.05). 4 After 7 and 14 days of resuscitation culture, the rate of apoptosis in the EGB group was less than that in the control group (P < 0.05), whereas Bcl-2 expression were increased (P < 0.05). Conclusion: EGB can reduce the cell loss after cryopreservation and resuscitation, prevent the cells from apoptosis, so as to protect the activity of islet cells.