[An experimental study of cell apoptosis and correlative gene expression after tractive spinal cord injury in rats].

OBJECTIVE: To observe the cell apoptosis after tractive spinal cord injury in rats, determine expression of apoptosis correlative genes, and study the molecular mechanism of cell apoptosis. METHODS: The T(13)-L(2) spinal cord of rats was injured by traction after the amplitude of P1-N1 wave decreased to 70% in postoperation than in preoperation through cortical somatosensory evoked potential (CSEP) monitor. Then rats were killed in 30 min, 6 h, 1, 4, 7, 14 and 21 d respectively after operation (n = 4). Cell apoptosis was examined by the flow cytometer and terminal deoxynucleotidyl transferase-mediated DUTP-biotin nick end labeling (TUNEL) reaction, the expression of p53, bax and bc1-2 genes was tested with immunohistochemistry. RESULTS: The flow cytometer test and TUNEL method showed that the apoptosis cell ratio raised in 6 h and reached at peak in 7 d after injury, and then declined till 21 d, they showed significant difference (P < 0.05, 0.01). TUNEL method showed that injured group had a large number of apoptosis glial cells in white matter. Immunohistochemical staining showed that the positive expression of p53, bax and bc1-2 protein raised at 6 h, expression of p53 protein reached at peak in 4 d, bax and bc1-2 protein reached at peak in 7 d after injury. Compared with control group and laminectomy group, the injured group showed significant difference (P < 0.05, 0.01). CONCLUSION: There is cell apoptosis phenomenon after tractive spinal cord injury in rats. Morphology indicates that apoptosis includes neurons and glialcytes, which is an important form of cell death and pathological changes in secondary lesion period after tractive spinal cord. There exist high expression of apoptosis correlative gene p53 and bax after spinal cord injury, they may play an important role in reduction of cells to apoptosis.