The Expression Of PERK,PCNA And GFAP After Acute Spinal Cord Injury And The Influence Of U0126 On Their Expression

Objective To observe the expression of pERK,PCNA and GFAP after acute spinal cord injury in rats model and analyze their correlations,and further observe the influence of U0126 on their expression.To explore the function of MEK/ERK pathway on the formation of glial scar and its significance. It may provides new ideas for clinical treatment of spinal cord injury.Methods Selecting 6 rats randomly from 78 female SD rats as the false damage group, the more than 72 only randomly divided into three groups:simple damage group, DMSO group(inject DMSO after injury) and U0126 treatment group (inject U0126 after injury). Simple damage group,DMSO group and U0126 treatment group were further divided randomly into four subgroups, according to different time points after SCI (subgroup of 1d, 4d, 7d,14d,6 rats in each subgroup), each subgroup are only 6. The 78 female rats were surgically removed the vertebral lamina of T12 segment to expose the spinal cord, and then in sham group, the spinal cord was untouched; in Simple damage group,DMSO group and U0126 treatment group, the spinal cord was hit by power of 10g×6cm according to modified Allen's method to establish rat acute spinal cord injury(SCI) model. The behavior of each group were respectively observed at 1d,4d,7d,14d after injury and Motor Function Assessment was taken(BBB), then the lesions were obtained from the injury locations and studied by HE staining, immunohistochemical staining(IHC) of pERK, PCNA and GFAP.using light microscope.The experimental data was analyzed by SPSS16.0 statistical software.Results 1. The rats had significant deficits in hind limb movement after spinal cord injury, according to the modified BBB hind limb locomotor rating scale score. The score of simple damage group and DMSO group could improved to a centain degree from 1^st to 14^th day, the highest score was 10;and the score of U0126 treatment group was higher than simple damage group and DMSO group (P<0.05), the highest score was 13. 2. In sham injury group a few pERK and PCNA expressed in normal spinal cord .Compared with sham injury group the expression of pERK and PCNA in injured spinal cord existed significant difference(P<0.05).1 day after SCI their expression increased prominently,and peaked at 7th day,and at the end of 14th day began drop. 3. In sham injury group GFAP exited in cytoplasm of astrocytes.Compared with sham injury group the expression of GFAP in injured spinal cord existed significant difference(P<0.05).its expression was increased progressively form 1st to 14th day after SCI. 4. The expression of pERK and PCNA ; PCNA and GFAP ; pERK and GFAP form 1^st to 14^th day after SCI all had positive correlation(r1=0.907,P<0.05;r2=0.823,P<0.05;r3=0.807,P<0.05). 5. The expression of pERK,PCNA and GFAP between simple damage group and DMSO group didn't existed significant difference(P>0.05).Compared with simple damage group and DMSO group the expression of pERK,PCNA and GFAP in U0126 treatment group at 7^th day and 14^th day was down-regulated, and existed significant difference(P<0.05).Conclusion 1. The expression of pERK,PCNA and GFAPincreased prominently after SCI,and had positive correlation with each other. those experimental results suggested that MEK/ERK signal pathway may be activated after SCI which can increase the phosphorylation of ERK ,and further promote astrocyte into cell cycle ,higher the proliferation of astrocyte, which lead to the formation of the glial scar. 2. MEK inhibitors U0126 can promote rats acute spinal cord injury rats after double hind ethology recovery. 3. The inhibitors of MEK U0126 can suppress the proliferation of astrocyte and reduce the formation of the glial scar . Its mechanism might reduce the phosphorylation of ERK in the spinal cord injury site by MEK/ERK signal pathway ,and further suppress astrocyte into cell cycle,lower the proliferation of astrocyte in order to provide favorable conditions for recovery of neurological function.