Abstract: Objective To explore the expression and the changes of ski with time in the injured spinal cord in rats. Methods Sixty adult female Sprague-Dawley rats were randomly divided into sham group (n=30) and injury group (n=30), each group were further divided into 1 week, 2 weeks, 4 weeks, 8 weeks and 12 weeks subgroups, with 6 rats in each subgroup. Spinal cord injury at T10 was established with modified Allen's technique (10 g×25 mm) in the injury group. The hindlimbs behavior of rats was rated with Basso-Beattie-Bresnahan (BBB) scores 1 day, 3 days, 1 week, 2 weeks, 4 weeks, 8 weeks and 12 weeks after spinal cord injury. Three rats in each subgroup were stained with HE staining to observe the pathological changes of the spinal cord and the formation of cavity. The other 3 rats were analyzed with immunofluorescence staining of ski and semi quantitative analysis. Results The BBB scores of each time point were less in the injury group than in the sham group (P<0.05). Necrosis was the major pathological change in the injury groups 1 and 2 weeks after injury; cystic cavity completely formed 4 weeks after injury, with dense scar tissue around it; there was no significant change in the cavity and scar 8 and 12 weeks after injury, however, the adjacent spinal cord was obviously thinner. Ski expressed little in the normal spinal cord, and expressed more and more after injury, peaked at 8 weeks and decreased then. Ski was mainly observed in white matter in the sham group and 12 weeks injury subgroup, which was in gray matter 2, 4 and 8 weeks after injury. Ski was highly expressed around the cavity in injury center and formed high expression band. Conclusion Ski expresses after spinal cord injury in rats, that may be associated with the activation and proliferation of astrocytes and the formation of glial scar.

Key words: spinal cord injury, ski, astrocyte, scar, rats