The Preliminary Study Of Calcium Signal In The Diffuse Axonal Injury

【Backgroung and aims】Diffuse axonal injury (diffuse axonal injury， DAI)， alsoknown as "diffuse axonal injury", is extensive cerebral white matter axon damage causedby outside force. DAI accounted for29%~43%in death of patients with traumatic braininjury. DAI with consciousness loss after head trauma is typical without a common focaldamage such as cerebral contusion. The common imaging examination such as CT，MRIcann’t show axonal injury directly There is no uniform diagnostic criteria for DAI atpresent. Although over the past20years, the great progress was made in research ontraumatic brain injury，diagnostic technique and treatment measures are also constantlyimproving，but the craniocerebral injury and fatality rate haven’t obviously decline yet.A large number of studies have shown that DAI were related with Ca2+overload,axoplasmic transport barriers, mitochondrial injury, axon cytoskeleton damage, free radicaland inflammatory factor and so on. It has been recognized that Ca2+overload is a keyaxon injury cascade reaction in the process of DAI. In treatment, so far，there is no specificmethod to block DAI，so the prognosis is poor. The slow progress of clinical and basicresearch in DAI also limits its application in forensic medicine， now it is still the difficultyin forensic identification and the focus of controversy.Therefore，this study observed the development of DAI by using Ca2+antagonistblocking in animal model to investigate the influence of Ca2+in the pathogenesis and mechanism of DAI. Also, this research was order to find a certain time window to preventaxon injury. Thus, the study might provide the research basis for clinical and forensicprogress of DAI.【Materials and Methods】DAI model was made by linear acceleration load referring toMarmarou’s method.28male SD rats completely randomly were divided into control group,experimental group and intervention group. The rats were sacrificed at12h,24h and72hrespectively. Each group at each timepoint included four rats. The intervention group wasadministrated with nimo(Nimodipine, ND) intervention after hit. The rats were sacrificedwith10%chloral hydrate anesthesia. And cerebellum and brain stem, along the left andright sagittal, were cut into two hemispheres. And a half was used for the determination onwet and dry ratio, the other half was used for brain tissue morphological andimmunohistochemistry detection.(1)The brain tissue was roasted in the oven (85) for24hours, and was weighed before and after roasting, the weight ratio of wet to dry wascalculated.2) The brain tissue was fixed with4%paraformaldehyde for24h, and then wasundertaken by dehydration, transparent, embedding and paraffin section was made,haematin-eosin (HE) staining and immunohistochemical staining were used to observe theaxonal and vascular injury.【Results】Theratio of wet to dry of brain tissue in the experimental group andintervention group was increased firstly, and then decreased. The water content of braintissue peaked at24h after trauma. The axon became twisted, swelling and breaking andshowed a gradually increased trend with the time extension in the experiment group, NDcould decrease the severity of axonal injury. Beta APP expression was increased inexperiment group with the time extension in the experiment group. Compared to theexperiment group, ND decreased beta APP expression. vWF expression was showed in theendothelial cell in subarachnoid blood vessel, brain parenchymal vessel and the axon inbrain stem. VWF expression in experiment group was increased firstly, and then decreasedwith the time extension. VWF expression was peaked at24h after trauma. The region in vWF expression in brain parenchyma was consistent with cerebral edema. ND decreasedvWF expression, especially in the vessel of brain parenchyma.【Conclusion】This studycouldsimulate Marmarou’s axonal injury animal models, inwhich brain edema, axonal injury and focal point of subarachnoid hemorrhage were showed.Using of calcium antagonists nimodepine could relieve cerebral edema, axonal injury andmake vascular injury localized after being hit, which revealed calcium signals played animportant role in the diffuse axonal injury. The cerebral edema was peaked at24h afterbeing hit, it was supposed that24h after trauma may be a better time window for thetreatment of diffuse axonal injury.