Neurocyte apoptosis and expressions of caspase-3 and Fas after spinal cord injury and their implication in rats.

To study the expression of neurocyte apoptosis and the changes of caspase-3 and Fas after spinal cord injury (SCI) in rats, improved Allen's method was used to make model of acute SCI at the level of T9 and T10. The animals were divided into six groups: a control group and 5 injury groups. The segments of injured spinal cords were taken 6, 24, 48 h and 7, 15 days after injury for morphological studies, including HE staining, Hoechst33258 staining and TUNEL labeling. The expression of caspase-3 was detected by immunohistochemical staining and RT-PCR. TUNEL-positive cells began to appear in the compression region 6 h after the injury, mostly located in the gray matter. TUNEL-positive cells were found in both gray and white matter, reaching a peak at the 3rd day. They began to decrease at the 7th day, distributed mostly in the white matter. Fas increased at the 6th h and peaked at the 3rd day. Caspase-3 mRNA increased at the 6th h, peaking 48 h after the trauma, and decreased after 7 days. The protein expression of caspase-3, as revealed by immunohistochemical staining, was similar to TUNEL in time. It is concluded that apoptosis takes place after spinal cord injury, and caspase-3 mRNA and protein expressions were enhanced in the apoptosis. The expression of caspase-3 has a positive correlation with Fas expression.