Effect of interleukin-2 on neurogliocyte and neuron apoptosis in rat models of acute spinal cord injury

Chuanli Zhou; Xiaoliang Chen; Ying Wang

摘要：BACKGROUND: Interleukin-2 (IL-2) may influence the growth and survival of nerve cells following spinal cord injury and resuscitate the proliferation and maturation of oligodendrocytes. OBJECTIVE: To observe the effect of IL-2 on neuronal apoptosis of neurogliocytes at different times following acute spinal cord injury in rats. DESIGN, TIME AND SETTING: A randomized grouping trial based on cellular morphology was performed at the Institute of Traumatic Orthopedics of Shandong Province between October 2004 and January 2006. MATERIALS: A total of 72 adult, male, Sprague Dawley rats were included in this study and were divided into a control group and an IL-2 group. The Bcl-2 monoclonal antibody and TUNEL kit were purchased from Wunan Boster Biological Technology Corporation. METHODS: Spinal cord injury was induced in all the rats by dropping a weight from a height of 25 cm onto the exposed spinal cord at vertebral levels T7-11, thus producing a mild lesion. Immediately following the modeling, the rats were injected with daily IL-2 (10 μL) intramuscularly (the IL-2 group). Other rats received an injection of physiological saline 0.5 mL/d (the control group). MAIN OUTCOME MEASURES: Bcl-2 immunohistochemistry was applied to detect the Bcl-protein and positive cell expression. The TUNEL method was used to count the number of apoptotic cells. RESULTS: The expression level of Bcl-2 proteins increased significantly in spinal cord tissues during the first day after acute spinal cord injury, reaching a peak on days 3 and days 8 in the control and IL-2 groups, respectively. They were more prevalent in neurogliocytes than in neurocytes, and then began to decrease on day 14. From then until day 21, less expression was detected (P < 0.05). In the control group, many apoptotic cells existed after 24 hours, and most of them were gliocytes; apoptotic cells reached a peak after 3-8 days. They then decreased gradually until day 21, when a small number of cells were still available. In the IL-2 group, the number of positive cells was significantly lower than in the control group (P < 0.05). CONCLUSION: The expression of Bcl-2 and the number of apoptotic cells in neurogliocytes undergo similar changes with time after acute spinal cord injury. IL-2 may upregulate the expression of Bcl-2 proteins and decrease cell apoptosis in spinal cord tissue.