[Diffusion tensor imaging study of the protective effect of shRNA on matrix metalloproteinase-9 in middle cerebral artery occlusion rats]

Objective: To investigate the cerebral protective effect of shRNA down-regulated matrix metalloproteinase-9(MMP-9) on cerebral infarction rats. Methods: 32 SD rats were randomly divided into four groups (8 for each group): group A (sham operation group): the branches of external carotid artery were only separated and ligated and were not be inserted thread; group B (MCAO group): rat MCAO models were made referring to the conventional Longa method; group C (physiological saline group): rats were injected with 5 μl saline two weeks before MCAO models; group D (lentivirus intervention group): rats were injected with 5 μl lentivirus-mediated shRNA two weeks before MCAO models.The diffusion tensor imaging(DTI) was used to evaluate the tissue of cerebral ischemic of middle cerebral artery occlusion(MCAO) in rats.At 4, 8, 12, 18 and 24 h after MCAO, the ADC value and FA value of the lesion side were calculated.The expression of MMP-9 protein in brain tissue of ischemic side was measured by Western blot, and the expression of MMP-9 protein was observed by paraffin section and immunohistochemistry.SPSS 17.0 software was used for statistical processing, and the difference was statistically significant in P<0.05. Results: At 4, 8, 12, 18, 24 h after ischemia, the values of ADC and FA in the ischemic area of the lentivirus intervention group were higher than those in the MCAO group, and the difference was statistically significant (the t values of ADC values at different time points were 8.78, 3.30, 3.58, 4.55 and 13.12, respectively P<0.05.The t values of FA values at different time points were 2.51, 5.87, 6.91, 4.97 and 4.58, respectively P<0.05). The expression of MMP-9 protein increased gradually after focal cerebral ischemia.The expression of MMP-9 protein in lentivirus intervention group was lower than MCAO group.The differences were statistically significant at each point (t values at different time points were 3.55, 6.11, 4.67, 4.63 and 2.77, respectively P<0.05). Conclusion: Lentivirus mediated shRNA inhibits the expression of MMP-9, reduces the vasogenic edema and plays a protective role in cerebral infarction.Magnetic resonance DTI can monitor dynamically the changes of ischemic area in rats with ischemic cerebral infarction.