Expression changes of miR-335 in focal cerebral ischemia tissues in rats and their related mechanisms

Objective To investigate the expression changes of miR-335 in rats with focal cerebral ischemia and their mechanisms. Methods Fifty adult healthy male SD rats were randomly divided into sham-operated group, model group, miR-335 transfection group, negative control group and blank plasmid group (n=10). The focal cerebral ischemia rat models in the later 4 groups were constructed by Longa method. After model making, rats in the miR-335 transfection group were injected recombinant plasmid pcDNA3.1-miR-335 and stearamide (SA) liposome mixture into the lateral ventricle, rats in the negative control group were injected pcDNA3.1-negative control and SA liposome mixture into the lateral ventricle, rats in the blank plasmid group were injected pcDNA3.1(+) and SA liposome mixture into the lateral ventricle, and rats in the sham-operated group and model group were injected the same volume of saline. Twenty-four h after ischemia, the neurological deficit of these rats were assessed by Zea-Longa scale. These rats were sacrificed, and the brain infarct volumes were measured by TTC staining; the miR-335 expression in cerebral ischemia tissues of rats was detected by using real-time fluorescence quantification PCR (RTFQ PCR); the protein expressions of cell adhesion molecule 1 (CD31) and vascular endothelial growth factor (VEGF) in cerebral ischemia tissues of rats were detected by Western blotting. Results As compared with those in the sham-operated group, the neurological function scale scores and brain infarct volumes of rats in model group, miR-335 transfection group, negative control group and blank plasmid group were significantly increased (P<0.05); the neurological function scale scores and brain infarct volumes of rats in miR-335 transfection group were significantly decreased as compared with those in the model group (P<0.05). As compared with those in the sham-operated group, the relative miR-335 expression level in the cerebral ischemia tissues of the model group, miR-335 transfection group, negative control group and blank plasmid group were statistically decreased (P<0.05); miR-335 transfection group had significantly increased relative miR-335 expression level as compared with the model group (P<0.05). As compared with those in the sham-operated group, the CD31 and VEGF protein relative expression levels in the cerebral ischemia tissues of the model group, miR-335 transfection group, negative control group and blank plasmid group were significantly decreased (P<0.05); as compared with those in the model group, the CD31 and VEGF protein relative expression levels in the miR-335 transfection group were statistically increased (P<0.05). Conclusion Up-regulation of miR-335 expression might improve cerebral ischemic tissue injury; it might be related to promote the angiogenesis in cerebral ischemia tissues. Key words: Focal cerebral ischemia; MicroR-335; Platelet endothelial cell adhesion molecule-1; Vascular endothelial growth factor