Structural Plasticity Changes In The Brain After Experimental Spinal Cord Injury

First In vivo MR vessel size imaging of brain vascular plasticity after experimental spinal cord injuryObjectives:Spinal cord injury（SCI）can damage efferent and afferent neural pathways,which can cause structural and functional changes in the brain.Recently MR vessel size imaging has shown promising application in visualizing angiogenesis in the brain.The study aims to explore the sensitivity of MR vessel size imaging at 7T high-field to the brain vascular plasticity changes after SCI.Methods:In this experiment,six male Sprague-Dawley rats were selected to perform Thoracic T₉hemisection.The MR scans were carried out 4 weeks after injury using a7T small animal MRI scanner.MRI datasets were analyzed using Image J software to quantify the changes in the corticospinal tract（CST）in this study.The expression of platelet endothelial cell adhesion molecule 1（CD31）and glial fibrillary acidic protein（GFAP）proteins was investigated by immunofluorescence assay.Results:Region of interest（ROI）analysis showed that 4 weeks after injury,mean vessel diameter（m VD）,microvascular density（Density）and vessel size index（VSI）values were significantly increased in the contralateral side compared with the ipsilateral pyramid of the injury site,suggesting angiogenesis or vascular activation in the white matter region of the contralateral CST.Immunofluorescence results showed that the intensity of staining for GFAP and CD31 also increased significantly in the contralateral pyramid 4 weeks after injury.Conclusions:MR vessel size imaging could provide valuable information on neovascularization in brain after spinal cord injury and may be a novel tool to diagnose brain vascular pathologies in patients with spinal cord injury.Second Olfactory bulb plasticity after experimental spinal cord injuryObjectives:SCI is a devastating neurological disorder that can lead to pathological changes in the olfactory bulb.The olfactory bulb is a relay structure that transmits olfactory information to the central nervous system and is highly plastic.Therefore,the aim of this study was to investigate whether SCI leads to plasticity changes in the olfactory bulb.Methods:In this experiment,48 male ICR mice were selected and randomly divided into SCI group（8 hours,3 days,7 days）and sham group,with 12 mice in each group.Thoracic T₉hemisection was performed in the SCI group of mice.The mice in the sham group were subjected to laminectomy and no hemisection injury.The expression of olfactory receptors（Olfr1494,Olfr1324,Olfr1241 and Olfr979）,brain-derived neurotrophic factor（BDNF）,glial cell-derived neurotrophic factor（GDNF）,and nerve growth factor（NGF）was detected by real-time fluorescent quantitative PCR assay.Expression of GFAP protein was investigated by immunofluorescence assay.Glutamine synthetase（GS）activity was evaluated by GS activity assay kit.Results:Real-time fluorescent quantitative PCR results showed that the m RNA expression levels of Olfr1494,Olfr1324,Olfr1241 and Olfr979 were significantly downregulated in the olfactory bulb tissues of mice 8 hours after SCI compared with the sham group.The m RNA expression levels of Olfr1494,Olfr1324,Olfr1241 and Olfr979 in the olfactory bulb tissues of mice recovered initially 3 days after injury compared with 8 hours after SCI and basically returned to the normal levels 7 days after injury.In addition,the m RNA expression levels of BDNF,GDNF and NGF were significantly downregulated in the olfactory bulb tissue of mice 8 hours after SCI compared with the sham group.The m RNA expression levels of BDNF and GDNF were significantly upregulated in the olfactory bulb of mice 3 days after injury compared to 8 hours after SCI,and the m RNA expression levels of NGF were also upregulated.The m RNA expression levels of BDNF,GDNF and NGF were significantly upregulated in the olfactory bulb tissue of mice 7 days after injury compared to 8 hours after SCI.Immunofluorescence results showed that the intensity of staining for GFAP increased significantly in the mouse olfactory bulb tissue at 8hours,3 days and 7 days after SCI compared to the sham group.The results of the GS activity assay kit showed that the GS activity was significantly reduced in the olfactory bulb tissue of mice 8 hours after SCI compared with the sham group.Compared with 8hours after SCI,the GS activity in the olfactory bulb tissues of mice recovered 3 days after injury and returned to normal levels 7 days after injury.Conclusions:SCI can cause plasticity changes in olfactory bulb.