Appiication Of MRI In Evaluation Of MCAO/R Model Of Rats

Background Ischemia reperfusion-injury is the basic pathology of cerebral infarction, which is also the main restriction factor of thrombolysis. After middle cerebral artery (MCA) occlusion, the ipsilateral MCA territory may be divided into infarction area and penumbra area. We want to know whether different regions have suffered different ischemia reperfusion damage and their underlying neural mechanisms. In this study, we combined MRI and pathologic methods to explore the infarction area and penumbra area to depict MR features and the damage mechanisms in two different kinds of areas.Parti. Application of MRA and T2in evaluating the success of a stable tMCAO model.Objective:MRA was used to evaluate the success of the rat model of vascular occlusion and recanalization to choose stable tMCAO (transient middle cerebral artery occlusion) model. Intracereral hemorrhage was assessed by T2scan. Qualified ischemia-perfusion rats were used to investigate the processes of the restoration of the blood flow after recanalizationMethods:Modified Zea-Longa operation was performed to establish the tMCAO models. After the MCA was occluded60min, it was recanalized. MRA was used to observe the artery and T2scan was used to exclude hemorrhage. The neurological function of each rat was also assessed.Results:There were four rats whose middle cerebral artery was not fully occluded, other rats were recanalization, the cerebral blood flow was gradually increased and close to the level of the contralateral hemisphere after5h of reperfusion. T2scans revealed no cerebral hemorrhage after perfusion. Only one rat showed bleeding in cavernous region near the internal carotid artery, which is considered as surgery-related.Conclusion:We can select qualified middle cerebral artery occlusion/perfusion model using MRA and T2.Part2MRI Manifestations of ischemia-reperfusion damage in different regions of the ischemia brain tissue and MMP-9/MMP-2expression. Objective:To observe MRI manifestations of cerebral ischemia reperfusion in infarct and penumbra area and to explore the expression of MMP-9/MMP-2in these different areas.Methods:Thread embolism was used to establish tMCAO (transient middle cerebral artery occlussion) rat models. These rats were divided into groups after60min or90min cerebral ischemia. Dynamic MR Scans were performed at baseline,2h,3h, and6h after cerebral ischemia. The ADC and FA of each time point were calculated. MMP-9/MMP-2expression was evaluated using WesternBlot and immunofluorescenc at different time points in ischemic brain tissue. BBB damage was assessed using EB permeate volume evaluate, cerebral edema was evaluated by wet and dry weight, and pathologic features were shown by HE staining.Results:(1)EB infiltration volume of90min group is32.75%, BBB open area of60min group shrinkage, EB infiltration volume of60min group smaller48.86%compared with90min group (t=5.673,P<0.01). Wet and dry weigh of90min group compared with Sham group, the brain water of content increased significantly (1.47±0.18. vs.1.05±0.07, t=2.57, P<0.05);60min group compared with90min group, significantly reduce the brain water content(1.25±0.11, P<0.05).(2) Combinting the ADC figure and EB premeating figure. We can observe the opening of the BBB in infarction and penumbra area, and the punumbra mainly in cortex.(3) MRI imaging features are:ADC signal of cortical area has been drops in90min group, and the ADC signal of subcortical area did not change significantly. The ADC signal of cortex recovery firstly in60min group,then falling.The ADC signal of subcortical area did not change significantly, Cortex rADC value of90min and60min group is more different in different measuring time.Cortex rADC value of60min is higher then rADC value of90min in21、3h、6h. Whether in90min or60min group, FA signal of cortex reduce with time extend. Subcortical area FA signal did not change significantly. Cortex rFA value of90min and60min is more different in different measuring time.Cortex rFA value of60min is higher then rFA value of90min in2h、3h、6h.(4) Immune fluorescent and Wb of MMP-9reveal the positive cells number and the quantity of protein expression increased with extend the time expansion, however MMP-2positive cells number and the quantity of protein expression increase at2h, with extend the time expansion MMP-2positive cells number and the quantity of protein expression increase lightly.Conclusion:The degree of cerebral ischemia-perfusion injury and brain edema may be associated with ischemia time. The longer of ischemia time, the severer of the reperfusion injury is. BBB opening may appear in both the infarction area and the penumbra area. The MRI manifestation of penumbra reperfusion injury is that rADC is firstly increased and then droped, companied by the decrease in FA. ADC and FA values in the infarction area do not change significantly in the acute stage. Perfusion injury machnism of penumbra associated with MMP-2, perfusion injury machnism of the infarction associated with MMP-9.