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Objective To investigate the dynamic images of traumatic penumbra(TP)in a rat model of traumatic brain injury (TBI)treated with AQP4-RNAi using multimodal MRI(MM-MRI)at 7.0 Tesla.Methods A rat model of TBI was established by the improved Feeney's method.MRI scans were performed including T2WI,DWI,ADC and SWI.The pathological changes in penumbra area were observed.All statistical analyses were performed using SPSS 21.0 software package.Results Over time rs-T2WI,rs-DWI and rs-SWI in TBI group were gradually increased.The r-ADC began to increase at one hour after trauma and reached the peak at 6 h. Then it began to fall and reached the bottom at 12 h.At each time point,the difference was statistically significant(P<0.05).Compared with RNA interference group,the rs-T2WI and rs-DWI in TBI group were decreased significantly at 6 h and 12 h(P<0.05),the r-ADC was not decreased significantly at 1 h(P>0.05)and decreased significantly at 6 h and 12 h(P<0.05).At each time point,there was no significant difference in rs-SWI(P>0.05).The area of mismatch between rs-SWI and rs-DWI was the most obvious at 6 h and 12 h,and the area of mismatch was decreased in size after treatment with AQP4-RNAi.There was no significant difference between TBI group and placebo group(P>0.05).In two groups,similar pathological changes were observed,which was depicted as vasogenic edema predominantly at 1 h and mixed edema at 6 h and 12 h. In RNA interference group,intracellular edema was markedly reduced at 6 h and 12 h,and the vasogenic edema was relieved to some extent at 12 h.Conclusion The treatment with APQ4-RNAi markedly alleviates cerebral edema.MM-MRI can reflect its pathological changes.The area of mismatch between SWI and DWI can prompt early detection of traumatic penumbra,which may provide useful information for clinical treatment.
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Objective To investigate the value of DWI high b value and ADC value in the diagnosis of hyperacute cerebral is-chemia.Methods Adult SD rats were selected and divided into the control and ischemic group by adopting the random number table method,the ischemic group was re-divided into 0.25,0.50,2.00,4.00、6.00 h groups according to the ischemic time,6 cases in each group with a total of 42 cases.The ischemic group conducted the right middle cerebral artery occlusion(MCAO)for performing the head T2WI and DWI scanning(b values were 0,400,800,2 000,3 000 s/mm2),the CNR and SNR values were recorded,rs-T2WI, rs-DWI and relative apparent diffusion coefficient(rADC)were measured.Then the imaging change of ischemic area was observed. The sensitivity and specificity were detected.Results In b=2 000 s/mm2and 3 000 s/mm2,the diagnostic rates of DWI for hyper-acute cerebral ischemia were obviously higher than those in b=400 s/mm2and 800 s/mm2,and when the b values were 400,800, 2 000,3 000 s/mm2,the sensitivities were 16.7%,50.0%,100.0% and 100.0% respectively and the specificities were 16.7%, 50.0%,100.0% and 100.0% respectively.The difference of ADC values under different b values had statistical significance(P<0.05).Conclusion High b value DWI in the diagnosis of hyperacute ischemia is significantly better than that of low b value,espe-cially in the aspect of displaying the lesion at 0.25,0.50 h cerebral ischemia.
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Objective To observe the abnormality of gray matter volume and density in patients undergoing postoperative delirium (POD).Methods Forty-seven cases of aged patients, 26 males and 21 females, aged 60-75 years, ASA physical status Ⅱ or Ⅲ, were selected.On the third day after operation, cognitive function estimation was performed.The patients were assigned into group POD and group C according to whether POD occurred and brain magnetic resonance imaging (MRI) scanning was implemented.The discrepancy in gray matter volume and density between the two groups were compared using voxel-based morphometry method (VBM).Correlation analysis was performed between the corresponding parameters in the regions where notable differences between the two groups existed and minimum mental state examination (MMSE) score were found.Results Global gray matter volume of group POD was notably lower than that of group C (P<0.01).Cerebrospinal fluid volume of group POD was significantly higher than that of group C (P<0.01).Gray matter volume of bilateral frontal gyrus and right parahippocampus was remarkably reduced in group POD (P<0.001).Gray matter density of bilateral hippocampus and right parahippocampus decreased significantly (P<0.001).Right parahippocampal gray matter volume was positively correlated with MMSE score in POD patients (P<0.05).Conclusion Structural abnormality in frontal regions, hippocampus and parahippocampus may play an important role in pathogenetic and developing process of POD.Gray matter volume in the right parahippocampus may be one of reference index for POD severity.
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Objective To investigate the usefulness of different-b-value diffusion weighted imaging (DWI) in patients with early cerebral infarction and obtain the optimal b value of early cerebral infarction.Methods DWI at b-value of 1,000,2,000,and 3,000 s/mm2 was performed for 40 patients within 72 h after the onset of stroke using a GE Signa HDx 3.0T MRI scanner.Post-processing was done by the DWI specific software Function Tool to gain signal intensity and mean apparent diffusion coefficient in the lesions center and the contralateral normal brain tissue,respectively.The sensitivity of conventional MRI and different-b-value DWI was calculated in the diagnosis of early cerebral infarction.Results In 40 patients with early cerebral infarction,the sensitivity of b-values of 1,000,2,000,and 3,000 s/mm2 (DWIb=1 000,DWIb=2 000,DWIb=3 000) and conventional MRI in the diagnosis of early cerebral infarction were 100％,97.5％,97.5％,72.5％,respectively.With b value increased,signal intensity and ADC value declined.Under the condition of different b values,signal intensity and ADC value were statistically significant in region of interest (P＜0.05).Conclusion DWI is superior to conventional MRI scan in monitoring early cerebral infarction.With the increase of b value,the sensitivity is the higher to hyperacute cerebral infarction,the signal contrast is obvious,while signal to noise ratio of the image reduces.It is suggested that brain tissue contrast and the sensitivity to the new cerebral infarction is more predictable on b value =1,000 DWI than on the other DWIs.
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Objective This study investigated magnetic resonance imaging (MRI)manifestations and pathological changes after aquaporin-4 (AQP4)gene silencing in treatment of early cerebral infarction.Methods Ninety adult Wistar rats were randomly divided into con-trol group,infarction group and treatment group.All the above groups were assigned to five sub-groups according to the time point:0.5,1,2,4 and 6 hours,respectively (n= 6 for each group).For the right middle cerebral artery occlusion (MCAO-infarction group),the rats were separately injected with short hairpin RNA-AQP4 liposome (shRNA-AQP4+MCAO-control group)and in-terference agents (siRNA-AQP4 + MCAO-interference group).The rats in all groups were examined with T2 weighted image (T2 WI)and diffusion-weighted imaging (DWI).The rs-T2 WI,rs-DWI and relative apparent diffusion coefficient (ADC)of the big-gest high-signal-intensity layer on T2 WI and DWI were measured.Corresponding brain tissue was collected for pathological observa-tion.The data were analyzed using SPSS 13.0 software.Results Identical changes were detected between control and infarction groups.The high-signal intensity was found on DWI at 0.5 hour and on T2 WI at 2 hours after MCAO.rs-DWI and rs-T2 WI in-creased with time.The value of relative ADC decreased quickly within 2 hours after MCAO,and cytotoxic edema was significantly aggravated.The value of relative ADC increased slowly at 4 and 6 hours,but angioedema was detected during this period.There was significant change in relative ADC between the treatment and control groups at 0.5 to 4 hours (P 0.05).However,angioedema was visible in this group at 6 hours.Above results confirmed that during early cerebral in-farction,the differential regions of DWI and T2 WI high-signal area were considered as cytotoxic edema,which was the pathologic basis of the decreased ADC values.AQP4 gene silencing could effectively reduce cytotoxic edema.Conclusion DWI and ADC value could reveal timely and exactly therapeutic outcomes of cytotoxic edema.The high-signal intensity on T2 WI represents angioedema, and AQP4 gene silencing has no obvious change.
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Objective To investigate the expression of aquaporins 4 (AQP4) and histopathological changes in early phase of traumatic brain edema and the correlation between AQP4 expression and structural damage to blood-brain barrier (BBB).Methods A total of 120 healthy adult Wistar rats were divided into sham operation group and brain trauma group (which was subgrouped at hours 1,3,6,12 and 24 postinjury) according to random number table,with 20 rats per group.At each time point,brain water content was measured; brain edema and BBB structural changes were observed pathologically;IgG and AQP4 expressions in traumatic brain tissues were detected with immunohistochemical method and Western-blotting.Results In sham operation group,negatively stained IgG was observed and there were no abnormalities in brain tissue structure,brain water content as well as AQP4 expression.In brain trauma group,cerebral water content presented notable increase at 6 hours postinjury and peaked at 24hours; IgG expression showed significant increase at 1 hour postinjury,peaked at 6 hours postinjury and remained a high level at 24 hours.Pathologic observation revealed damage to BBB,blood red cells leaking out of the blood vessels,and tissue gap widening at 1 hour postinjury,which manifested as vasogenic brain edema.Further,those phenomena were gradually aggravated over time and became obvious at 6 hours postinjury.Intracellular edema occurred at 3 hours postinjury,with the presence of increased glial cell body,cytoplasm light staining or vacuolar degeneration,as well as mitochondria swelling and was also aggravated with time,particularly at 6 hours postinjury.Except that the previously mentioned two forms of edema coexisted at 12 hours postinjury,tissue necrosis,inflammatory cell infiltration and microglia proliferation were emerged and aggravated at 24 hours postinjury.AQP4 level decreased at 1 hour,minimized at 6 hours and regained at 12 hours,showing a V-shape curve.Conclusions Vasogenic edema characterized by BBB disruption is the primary histopathological change in early-phase of brain trauma,followed by the coexistence with intracellular edema and aggravation of the two forms of edema over time.AQP4 expression is down-regulated in the vasogenic edema phase but highly expressed at phase of the intracellular edema.
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Objective To investigate the expression of aquaporin-4 (AQP4) in cultured astrocytes after in vitro hypoxia induced by CoCl2. Methods After primary culture and subculture, the astrocytes were placed in a controlled atmosphere culture chamber. Both control group and hypoxia groups were established.These groups were further divided into seven sub-groups according to the different time intervals: 15, 30minutes and 1,2, 4, 6, 12 hours, respectively (6 apertures for each group). The shape of the astrocytes in each group was observed with light microscopy and transmission electron microscopy ( TEM ). All groups were examined using in situ hybridization, real time fluorescence quantitative reverse transcriptase polymerase chain reaction, immunocytochemistry and Western blot. The data was analyzed statistically with SPSS 13.0 software. Results There was significant consistency between the AQP4 mRNA and protein ( r =0. 85, P ＜0. 01 ). There was slight positive expression of AQP4 in a few astrocytes of the control groups. In the hypoxia groups, the expression of AQP4 increased within 15 minutes; the increase was most prominent between 1 and 4 hours( mRNA in hypoxia groups: 0. 26 ± 0. 04, 0. 31 ± 0. 02, 0. 36 ± 0. 04; control groups:0. 06 ±0. 01,0. 09 ±0. 01,0. 08 ±0. 01 )after hypoxia and became less between 6 and 12 hours; There was significant difference in the AQP4 expression between the hypoxia groups and control groups among different time points (t = 16. 51, 18.20, 15.26,all P＜0. 01 ). The corresponding pathological changes were cellular edema, which was most prominent between 1 and 4 hours. Under TEM, increase in size of the nucleolus and swelling of endoplasmic reticulum and mitochondria; these changes became more marked with time.Disruption of a few astrocytes was detected in the hypoxia groups at 12 hours. Conclusions The pathological change of astrocytes is cellular edema following hypoxia. There is a positive relationship between the presence and degree of cellular edema as well as the duration of hypoxia and the up-regulating of AQP4.These results imply that AQP4 expression is an important molecular mechanism of celluar edema of astrocytes.