Controlled Decompression Alleviates Acute Brain Injury In Rats Via Inhibiting Necroptosis And Improves Early Postoperative Cerebral Perfusion In Brain Trauma Patients

ObjectivePart 1: To establish a rat epidural extreme intracranial hypertension（EEIH）model,and on the basis of this model to elucidate the possible molecular mechanism of controlled decompression in reducing acute brain injury induced by EEIH in rats.Part 2: To determine the effect of controlled decompression on early postoperative cerebral perfusion in patients with severe traumatic brain injury（s TBI）via analyzing results of cerebral computerized tomography perfusion image（CTP）and transcranial doppler sonography（TCD）.MethodsPart 1: After anesthetization,the top hair of Sprague-Dawley rats was removed and the skin was incised for 3cm long.The skin and subcutaneous tissue were separated to fully expose the skull.After drilling on both sides of the center line,the intracranial pressure（ICP）probe was inserted into the brain through the right bone foramen and the balloon was placed into the epidural through the left bone foramen.The volume of balloon was regulated via water with a pressure pump.The level of EEIH was determined by recording and analyzing the ICP and cerebral perfusion pressure（CPP）of rats at different balloon volumes,as well as the mean arterial pressure（MABP）,mortality rate and mean velocity（Vm）of left middle cerebral artery（LMCA）of rats at different ICP levels.The rats were divided into Sham Group,Controlled decompression Group（Con Group）,Rapid decompression Group（Rap Group）and Rapid decompression + Necrostatin-1（Nec1）Group（Rap + Nec1 Group）according to different treatment.Prehensile traction and beam-balance tests were performed at 24 hours and 1 week after operation,and cerebral water content was determined at 24 hours after operation.24 h postoperatively,cortical brain tissue was collected from the compression side,and the levels of interleukin-1 β（IL-1β）and tumor necrosis factor-α（TNF-α）were measured by western blotting（WB）and real-time polymerase chain reaction（Rt-PCR）to assess the level of neuroinflammatory response,and the levels of reactive oxygen species（ROS）were measured to determine cerebral ischemia-reperfusion injury（IRI）.At the same time,Nissl bodies were stained to evaluate the extent of neuron injury between groups,and the content of Evans blue（EB）in brain was measured to determine the permeability of blood brain barrier（BBB）in each group.WB and RT-PCR were used to detect the expression levels of necroptosis related proteins: RIPK1,RIPK3 and MLKL（WB only）in the cortex on the compression side at 24 h after surgery,and the expression of RIPK3 in neurons was further evaluated by immunofluorescence staining（RIPK3-NEUN）.Part 2: 20 patients with s TBI who were admitted into 904 th Hospital of Joint Logistic Support Force from June 1st,2020 to October 31 st,2020,were divided into control group（10 cases,standard large bone flap decompression）and observation group（10 cases,controlled decompression）.All patients received CTP examination at 12 h and 72 h after surgery and TCD monitoring for 7 days to compare the effects of these two operations on early postoperative cerebral perfusion.ResultsPart 1: After recording ICP and MABP of rats at different balloon volumes,CPP values were calculated and cerebral pressure-volume curve of rats（P-V curve）was plotted.Meanwhile,the survival rate,MABP and Vm of LMCA were recorded at different ICP levels.With analysis of the data,the EEIH level of rats was finally determined at40 mm Hg.After being injured by epidural balloon pressured up to 40 mm Hg,decompression was performed on rats in different ways.The results suggested that controlled decompression lowered cerebral water content,improved neurological function,and attenuated EEIH-induced inflammation response and ROS generation to a greater extent than rapid decompression.Meanwhile,controlled decompression functioned to preserve more Nissl bodies,indicating alleviated neuron injury after EEIH.Additionally,the permeability of BBB was also safeguarded in the Con group.WB and Rt-PCR assays consistently determined lower protein and m RNA levels of necroptosisrelated molecules RIPK1,RIPK3 and MLKL（WB only）in the Con and Rap+Nec-1 group.Double immunofluorescent staining found weaker fluorescence intensity of RIPK3 in the compressed neurons of the Con and Rap+Nec-1 group.Part 2: In observation group,cerebral blood flow（CBF）and cerebral blood volume（CBV）of basal ganglia region in lateral ventricle plane on the decompression side was higher than the control group,on the contrary,mean transit time（MTT）was lower.Additionally,mean velocity（Vm）of internal carotid（ICA）and middle cerebral artery（MCA）was higher in observation group compared with the control group,and pulsatility index（PI）was lower.This trend was more obvious in the 1-3 days after surgery.ConclusionPart 1: The level of rats EEIH was determined and based on this result,an EEIH model of rats was built to corroborated the effectiveness of controlled decompression in reducing brain injury induced by EEIH.It was suggested that controlled decompression could effectively reduce brain edema content,improve neurological scoring,thwart neuroapoptosis,inflammation response and ROS generation,ameliorate neuro-death and attenuate BBB damage in rats inflicted with EEIH.The neuro-protective effect of controlled decompression may be attributable to the inhibition of necroptosis trigged by TNFR-1 activation.Part 2: In the aspect of improving early cerebral perfusion in s TBI patients after surgery,controlled decompression had more advantages over standard large bone flap decompression.