Objectives: To observe the effect of FTY720 on the changes of tissue microenvironment after acute spinal cord injury (ASCI) in rats. Methods: A total of 168 female SD rats were randomly divided into A, B and C groups, with 56 rats in each group. In group A (Sham-operation group), only T9 laminectomy was performed without spinal cord injury, and 0.3 ml normal saline was given by gavage immediately after suture. Group B (control group) was given 0.3 ml normal saline by gavage, group C (treatment group) was given 0.3 ml FTY720 diluted in 3mg/kg normal saline by gavage. The rats were sacrificed at 6h, 12h, 24h, 72h, 7d and 21d after operation. The injured spinal cord (the corresponding part of group A) was taken for ultrathin section, and HE staining was used to observe the necrosis of the spinal cord, inflammatory cell infiltration, glial scar formation, and the size of the syringomyelia in each group. The ratio of syringomyelia area to spinal cord area was calculated 21 days after injury. SPSS 13.0 software was used for statistical analysis. Results: HE staining showed that the morphology of the spinal cord in group A was normal at each time point: At 12h to 48h after operation, progressive edema of the spinal cord and liquefaction necrosis of the injured central area were observed, accompanied by inflammatory cell infiltration, mainly neutrophils, lymphocytes and monocytes. At 12h and 72h after operation, the degree of inflammatory cell infiltration in group B was significantly higher than that in group C (P<0.05). The degree of lymphocyte infiltration in group C was significantly lower than that in group B 12 hours after operation (P< 0.05). At 72 hours after operation, the central area of the injury had formed an unorganized structure cavity, and a large number of inflammatory cells infiltrated around the cavity, mainly microglia/monocytes. The number of glial scar cells in group B was significantly higher than that in group C (P < 0.05). The syringomyelia formed 21 days after operation. The syringomyelia ratio in group B was significantly higher than that in group C (P<0.05). Conclusions: FTY720 can significantly improve neurological function in rats after ASCI possibly by inhibiting the inflammatory response after spinal cord injury, thereby reducing the secondary injury of the spinal cord
