Effect of survivin knockdown on apoptosis and spatial learning and memory of mice with traumatic brain injury

Abstract

Objective To examine the effect of survivin downregulation by adenovirus-mediated RNA interference on apoptosis in hippocampal dentate gyrus and spatial learning and memory of mice with traumatic brain injury (TBI). Methods A total of 112 adult male mice were allocated into 4 groups (28 animals each) according to the random number table. Fluid percussion model of TBI was used in the study. In negative control group, animals were stereotactically injected with control recombinant adenovirus immediately after injury. In survivin knockdown group, the animals were stereotactically injected with shRNA adenovirus immediately after injury. In sham group, animals were subjected to identical surgery without fluid percussion injury. In TBI group, animals were subjected to isolated fluid percussion injury. Real-time fluorescent quantitative polymerase chain reaction (RT-PCR), Western blot analysis and immunofluorescence staining were used to detect expression level of survivin in mouse brain tissue. TUNEL assay was used for measuring apoptotic cells in hippocampal denate gyrus. Morris water maze test was adopted to evaluate mouse learning and memory after surviving downregulation. Results Expression levels of survivin mRNA and protein in survivin knockdown group reduced at days 3 postinjury compared to negative control group (1.21±0.11 vs.4.05±0.30; 0.34±0.08 vs.1.11±0.17, respectively) (P<0.01). Immunofluorescence staining showed survivin-positive cells calculated 267.45±38.41 in survivin knockdown group, lower than 896.56±102.23 in negative control group (P<0.01). TUNEL-positive cells in dentate gyrus of the hippocampus in survivin knockdown group increased at days 3 postinjury compared to negative control group (416.1±29.0 vs. 250.2±20.8) (P<0.01). Morris water maze test confirmed that survivin downexpression did lead to a statistically significant changes in escape latency (P<0.05) and target quadrant (P<0.01). Conclusion Decreased expression of survivin may promote apoptotic cell death and result in a negative role in the recovery of learning and memory function of mice after TBI. Key words: Mice, knockout; Brain injuries; Apoptosis; Memory function