The Diffusion Weighted Imaging Research On AQP4Gene Silence Treatment Of Early Hypoxic-ischemic Brain Edema

Objective: To obverse the early stage of image features of diffusion weightedimaging (DWI) and apparent diffuse coefficient (ADC) maps, monitor the values ofADC, and discuss the intervention effect of the water channel protein-4(Aquaporin-4,AQP4) gene silence on hypoxic-ischemic brain damage (HIBD) of neonatal pigs,moreover to study the AQP4mRNA expression level in early stage of HIBD and its’significance.Materials and Methods:40healthy neonatal York pigs (3-5days,1.3-1.6kg, nolimit of male or female, from dalian huaqiao pig farm) were divided into experimentaland control groups randomly (20pigs per group).12pigs (5pigs of experimental groupand7pigs of control group) died in the whole experimentation because of lack ofoxygen, operation wound and so on.2pigs of experimental group because of injectionfailure were put into control group, and there were13pigs in experimental group and15in control group finally. Experimental group was given intra-ventricular injection ofsiRNA-AQP4(interference Sequence) and hypoxic-ischemic (bilateral carotid arteriesligation and then with4%oxygen and96%nitrogen for30minutes); Control group wasgiven siRNA-Negative (AQP4sequence of non-interference) and hypoxia-ischemia.Give an intramuscular injection of penicillin after operation for infection prevention;Feed discretionary and supply enough calories and fluid.The1.5T MR scanner and standard head coil were used after model wasestablished successfully and coronary scan. All cases in two groups were scanned at0h,1h,3h,6h,9h and12h after hypoxia-ischemia respectively; MR protocols included theT1-weighted imaging (T1WI), T2-weighted imaging (T2WI), fluid attented inversionrecovery (FLAIR) and diffusion weighted imaging (DWI). The DWI scanningparameters: TR=6000ms, TE=91.1ms, slice thickness=4mm, NEX=2, matrix=128x128, B value=0/1000s/mm2. All original images would be sent to and post-processed on GE advantage workstation AW4.4; Regions of interest (ROI) onfrontal cortex, hippocampus and periventricular white matter areas of bilateralhemispheres were chose respectively and ADC values were measured.All pigs’ brains were taken out under anesthesia with3%sodium pentobarbitalintra-peritoneal injection after12h scan. SP immunohistochemical stain was applied toobserve the change under light-microscopy on one side of the brain; on the other side ofthe brain, by real-time fluorescence quantitative PCR detection was used to get theexpression of target gene and Ct value.The ADC values of different parts and different time points between the twogroups were tested by repeated measures data of ANOVA in SPSS16.0software. AQP4mRNA relative expression and Ct value at the same area between the two groups weretested by independent-samples T test. AQP4mRNA relative expression and Ct valueamong the different areas were analyzed by paired-samples T test.Result:1. The high signal at cerebral cortex, hippocampus and periventricular whitematter areas of the experimental group were no obvious, and ADC values of all timepoints were no significant difference (p>0.05); all areas of control group showeddifferent levels of high signal, all ADC values corresponding were reduced, thevariation was that significantly decreased at1hour, lowest at3hours, began to rise at6hours and12hours near to normal, and significant difference among all time points waspresent respectively (p<0.05). ADC value of control group at each time point and samearea was significantly lower than the experimental group (p<0.05).2. Independent-samples T test showed that: the AQP4mRNA relative expressionat hippocampus of experimental group was significantly lower than control group(relative expression were0.80and1.48, p=0.04); the AQP4mRNA relative expressionat periventricular white matter area of experimental group was slightly lower thancontrol group (relative expression were0.69and1.10), but no significant difference waspresent (p=0.31). The Ct values at hippocampus and periventricular areas ofexperimental group were higher than control group (Ct values of hippocampus were20.62and18.47; periventricular areas were20.53and18.93), but no significantdifference was present respectively (p=0.05,0.92).3. Paired-samples T test showed that: the AQP4mRNA relative expression ofhippocampus was significantly higher than periventricular white matter area (meandeviation was0.25, p=0.00); the Ct value of hippocampus was lower than periventricular white matter area (mean deviation was-0.21), but no significantdifference was present (p=0.09).Conclusion:1. Neonatal piglets HIE model had good operability. Bilateral carotid arteriesligation and with4%oxygen30minutes can result in a consistent level of HIE, for thestudy HIE of neonatal asphyxia provide a more reliable animal model.2. DWI has obvious advantages in the early diagnosis of HIE and can reveal itsevolution of microscopic pathophysiology. ADC values can reflect change regulation ofearly hypoxic-ischemic brain edema from the pathophysiological level.3. AQP4expression is connected with occur and develop of HIBD brain edemapathological changes; AQP4gene silence can control HIBD early brain tissue of thebrain edema happen. In the early of hypoxic-ischemia, AQP4gene intervention canprevent the occurrence of cerebral edema.