| Background and PurposeIschemic cerebral infarction is a serious manifestation of cerebrovascular disease.The high rate of incidence,mortality and disability make ischemic cerebral infarction become a major public health problem in the world.The neuro-functional defects caused by it include the death of neurons in the infarct core and the secondary delayed injury of adjacent or distant brain tissue.Diachisis is used to describe the decline of brain function or metabolism in the remote cerebral region far from the primary injury.Clinical studies have shown that there is a relationship between secondary injury remote site and neurosymptomatology,and specific treatment strategies based on this phenomenon may improve the neurological functional prognosis in patients.RGMb?Repulsive guidance molecule B?is involved in the development of the nervous system,and the expression decreases with the growth and development.Once the central nervous system was attacked by disease in adulthood,it would re-expressed or overexpressed.In such situation,it would be involved in the inhibition of nerve regeneration,apoptosis and so on.The study of RGMb may be helpful to improve the neurological symptoms and prognosis after cerebral infarction.Diffusion kurtosis imaging?DKI?is based on the non-Gaussian characteristics of the microscopic diffusion-distribution of water molecules in complex microstructures.,using kurtosis to quantify the extent to which the diffusion of water molecules deviates from Gao Si's model.Compared with diffusion weighted imaging and diffusion tensor imaging,DKI is more sensitive to subtle changes in tissue structure,which has been verified in many studies.The secondary effect of white matter injury caused by ischemic attack in the remote site is the pathological basis of DKI to detect diachisis.In this study,the mechanism of neural network injury after cerebral infarction was taken as the main content.Using DKI technique to observe the signal changes of primary foci and distant sites?contralateral mirror area and bilateral cerebellum?after cerebral infarction in MCAO rats,and analyze the correlation between the signal changes and the expression level of RGMb.To explore the value of DKI technique in monitoring the pathophysiological changes of cerebral infarction lesions and corresponding distant sites,so as to provide further research support for the occurrence of diaschisis after ischemic cerebral infarction..Materials and MethodsSeventy-two healthy male SD?sprague dawley?rats?body weight 260g-320g?are divided into two groups:MCAO group?60 rats,12 rats at 1h,6h,12h,24h,3d respectively?:left MCAO model is established by referring to Longa method.Control group?n=12?:the method is the same as that of MCAO group,but the suture is not inserted into the internal carotid artery.After MCAO model made successfully,neurological score and magnetic resonance image scanning are performed at 1h,6h,12h,24h and 3d.The scanning sequences included T1WI,T2WI,DWI and DKI.DKI images are processed and analyzed.The mean kurtosis?MK?value and the mean diffusivity?MD?values of infarcted basal ganglia,mirror-side basal ganglia and bilateral cerebellum are measured at each time point,and the change rates of MD and MK relative to control group are calculated.At the corresponding time point,6 rats in MCAO group are randomly selected for brain tissue specimens,and the sections of region of interest are selected for HE staining and immunohistochemical method to detect the expression of RGMb protein.6 rats randomly selected for specimens from the control group point for HE staining and immunohistochemistry after scanning are finished at all time;SPSS 21.0?Chicago,IL?is used for statistical analysis.The independent sample t test or Mann-Whitney U rank sum test is used to compare the mean of the two samples.One-way analysis of variance or Kruskal-Wallis test is used to compare multiple groups of samples,and LSD-t test or Dunn-Bonferroni test is used for multiple comparison if the difference is statistically significant.Spearmen correlation analysis or Pearson correlation analysis is used to calculate the correlation between RGMb immunohistochemical semi-quantitative results with MD value,MK value or neurological function score separately.When P<0.05,the difference is statistically significant.Results1.The MD values of infarcted foci,infarcted mirror areas and bilateral cerebellar hemispheres reached the lowest value at 12h,and then increased,while MK values of infarcted foci,infarcted mirror areas and bilateral cerebellar hemispheres all reached the highest value at 12h,and then decreased.2.Compared with control group,MD value was significantly decreased and MK value was significantly increased at 1h,6h,12h,24h,3d in MCAO group.MD value was significantly decreased at 6h,12h,24h,3d in infarct mirror area,and MK value was significantly increased at 1h,6h,12h,24h,3d.The MD values of ipsilateral and contralateral cerebellar hemispheres decreased significantly at 1h,6h,12h,24h,3d and MK increased significantly at each time point.All P<0.05.3.There were significant differences in MD and MK values at different time points in the same region of interest?infarct focus,infarct mirror area and bilateral cerebellar hemisphere?in MCAO group?P<0.05?.4.Compared with the infarcted mirror side,the MD value of the infarcted area decreased significantly at 1h,6h,12h,24h,3d,and the MK value increased significantly at each time point?P<0.05?.Compared with the ipsilateral cerebellar hemisphere of the infarcted side,the MD value of the infarcted area is significantly lower than that of the ipsilateral cerebellar hemisphere.The MD value of contralateral cerebellar hemisphere decreased significantly at 6h and 12h,and MK increased significantly at 1h,6h,12h,24h,3d?P<0.05?.5.The change rate of MK value at different time points in infarction focus,infarction mirror area and bilateral cerebellar hemisphere was higher than that of MD value.6.In MCAO group,the expression of RGMb positive cells increased since 1h after operation in the infarcted core area,infarcted mirror area and bilateral cerebellum,and reached the peak at 24h.7.Compared with control group,the mean optical density of RGMb in infarcted focus,infarcted mirror area,contralateral cerebellar and ipsilateral cerebellar hemisphere increased at 1h,6h,12h,24h,3d significantly,andit increased significantly in ipsilateral cerebellar at 6h,12h,24h and 3d after infarction.?P<0.05?.8.There was significant difference between different time points of mean optical density of RGMb in the same region of interest?infarct focus,infarct mirror area and bilateral cerebellar hemisphere?in MCAO group?P<0.05?.9.Compared with the infarcted mirror side,the mean optical density of RGMb in the infarcted area increased significantly at 1h,6h,12h,24h,3d?P<0.05?.Compared with the ipsilateral cerebellar hemisphere of the infarcted side,the mean optical density of the infarcted area was significantly higher than that of the ipsilateral cerebellar hemisphere.The mean optical density of RGMb in contralateral cerebellar hemisphere increased significantly at 1h,6h,12h,24h?P<0.05?.10.In MCAO group,the mean optical density of RGMb in infarcted area and contralateral cerebellar hemisphere is positively correlated with MK value?r=0.892,0.818,P<0.05?.The average optical density of RGMb in infarcted area is negatively correlated with MD value?r=0.814,P<0.05?.11.The mean optical density of RGMb in infarcted area,infarcted mirror area,ipsilateral cerebellar hemisphere and contralateral cerebellar hemisphere is negatively correlated with neurological function score separatively?r=-0.928,-0.928,-0.928,-0.783,P<0.05?.Conclusion1.The MK value is more sensitive than MD value to detect the changes of cerebral neural network connection after cerebral infarction.2.The changes of DKI parameters in the contralateral brain and distant cerebellum after cerebral infarction indicates the existence of transhemispheric transhemispheric diaschisis and cross cerebellar diaschisis after ischemic cerebral infarction in rats.3.The increased expression of RGMb induced by cerebral infarction is related to the neurological function score and the changes of DKI parameters in remote brain areas,demonstrates RGMb may be involved in the process of neurological damage and the occurrence of diachisis. |
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