A Model Of Blast-related Traumatic Brain Injury In Rats And The Study Of Correlative Mechanism

In current military conflicts and presented to the civilian terrorism, the majorcontributor of neurotrauma is blast-related traumatic brain injury (bTBI). Primary blastinjury (PBI) is one of the most important part in bTBI. However, the effects andmechanism of blast-induced neurotrauma are poorly understood. Although previousinvestigators have made significant contribution in establishing various bTBI animalmodels to simulate PBI that commonly occur on the battlefeld, yet the precision andcontrollability are still insufficient. In this study, a novel primary blast injury model isestablished by using a miniature spherical exploder to simulate a realistic blast wave acting upon a rat’s brain. The animal model can facilitate the development of treatmentstrategies for clinical cases of bTBI.The treatment strategies for bTBI is mainly for secondly brain damage, whichinclude intracranial hematoma and brain edema. Diffuse brain edema as the mainpathological phenomena of traumatic brain edema causes a large number of nerve cells toapoptosis and necrosis. Most malignant brain edema are not suitable for surgery, whichhas a death rate as high as87.2%.AQP4is a important molecules which involved in formation, development andoutcome of brain edema, it plays an important role in the transport through membrane ofwater molecules. However, the mechanism of AQP4in TBE is still poorly understood.Research in AQP4and TBE are beneficial to understanding the mechanisms of bTBI.These data can hopefully guide and facilitate the development of strategies for thetreatment of clinical cases of bTBI.Part I A novel model of blast-related traumatic brain injury in ratsObjective: To establish a stable and reliable animal model of blast-relatedTraumatic Brain Injury (bTBI) in rats, which simulating the mechanism of Primary BlastInjury (PBI) of explosive weapons. Methods: By using the standard of2.5-mm diameterspherical exploder with the explosive equivalent15.6mg TNT, and3.0-mm diameterspherical exploder with the explosive equivalent27.0mg TNT.110maleSprague–Dawley rats were divided into a2.5mm group, a3.0mm group and a controlgroup randomly. Based on the time point after injury at6h,12h,24,3d and7d，eachgroup were randomly divided into five subgroups, n=10. After the rats were anesthetized,the two different spherical exploders were placed2.0mm above the right frontal parietallobe of the rats (3mm right to the center point between bregma and lambda). Theexplosion was triggered by an electric detonator and a silver blast-guide cable. Thephysiological and pathological changes were recorded and the brain tissue was examinedby a microscope at6h,12h,24h,3d,7d after injury. The blood samples were collectedfor testing the changes of serum neuron specific enolase (NSE) concentration after explosion. Results: The results of HE staining in control group brain tissues showed thatcortical and hippocampal cells’ structure are clear, tightly packed. Neuronal cell bodiesare complete, normal morphology. The experimental animals of2.5mm group allsurvived within7days after the explosive injury, significant subdural hematomas andsubarachnoid hemorrhages were observed. In the pathological examination, the apoptosisand the necrosis of cerebral neurons were founded, Some nuclei of neuron are lightlystained, swelling, nuclear fragmentation and nuclear condensation. The microvascularbleeding was visible surrounding the damage area. The NSE concentration increasedfrom6h after brain injury, with the peak value at24h which remarkably higher than thecontrol group, and lasted to7d. A large number of TUNEL-positive cells can be seen atthe damage zone surrounding cortex after explsive injury.3.0mm group has a moresignificantly damage than2.5mm group, the death rate of this group is34%. Conclusion:The damage of3.0mm group is overweight, animal mortality rate is too high. Comparedwith the3.0mm group, the2.5mm diameter spherical exploder in the2.0mm distancecan simulate the effect of PBI in explosion. This can be used to build a reliable andreproducible bTBI model in rats.Part II AQP4expression after blast-related brain traumatic injuryObjective: To investigate the brain water content and the expression of AQP4afterblast-related traumatic brain injury. Methods: In blast-related traumatic brain injurymodel, we detected the changes in brain water content and the changes of AQP4proteinusing Western-Blot. Results: Brain water content significantly increased with the peakvalue at12h after explosive injury which remarkably higher than the control group, andlasted to7d. In the control group, the expression of AQP4is very little in brain tissue.AQP4was significantly increased6h after explosive injury and peaked at12h.7d afterinjury, the expression is still higher than control group. Conclusion: The brain watercontent and the protein levels of AQP4was increased after explosive injury. The changesof brain water content was consistent with the change of expression of AQP4. Suggestingthat the AQP4may play an important role of in bTBI and TBE.