A Preliminary Study On Diffuse Axonal Injury Using MALDI-TOF IMS Technology

Background and Objectives:As the Human Genome Project gradually completed,scientists put forward after the Genome Project,proteome research is one of the important projects.Proteomics will become the most effective way to look for molecular markers of disease and drug targets.It has an attractive prospect in the field of clinical diagnosis and treatment of cancer,Alzheimer's disease and so on.In recent years,matrix assisted laser desorption/ionization time of flight imaging mass spectrometry,MALDI-TOF IMS,has been successfully used for directly analysis of biological tissue section,it not only avoids the time-consuming sample extraction,,purification,separation,but also obtains proteins and peptides expression profile of tissue and draws two-dimensional spectrum images.As a new technology,MALDI-TOF IMS can simultaneously draws thousands of two-dimensional spectrum images of proteins or peptides in tissue.MALDI-TOF IMS has been widely used in protein expression and biomarker discovery in physiological and pathological tissue.Diffuse axonal injury(DAI)is a kind of brain injury that cerebral white matter damage as the main characteristics after suffer from the blunt external force.Due to the main characteristic of DAI is cerebral white matter axon injury,so it's lack of the clear location of neurological damage and imageological characteristic leading to the high mortality and morbidity.It's difficult to diagnose DAI if only depend on autopsy and general histological examination.In recent years,the rapid development of proteomics technology has brought a new opportunity to discover biological markers,this technology can analyze the whole protein profile,is expected to discover a set of related protein or peptide instead of a single molecular,in other to achieve the purpose of early diagnosis.Methods:Establish the animal model of DAI and apply MALDI-TOF IMS to detect protein profile in brain tissue sections from DAI rats(n= 10)and healthy controls(n=5)to find the specific proteins.10mg/ml sinapinic acid in 60%acetonitrile and 0.2%trifluoroacetic acid were used as matrix,and MALDI-TOF MS scanning was conducted on the brains in the m/z range of 1kDa to 20kDa with positive and liner mode.ClinProTools 2.2 software was used to statistical analysis,and then picked out 5 significant differentially expressed proteins(p<0.05)to conduct imaging.The 5 proteins are M4963.30Da,M5634.78Da,M6253.65Da,M6714.37Da and M7532.87Da.Observed the distribution of the proteins in the rat brains.5 proteins which were picked out to conduct imaging differentially expressed in the rat brain.Set up the diagnostic models by analyzing proteomic profile with ClinProtools 2.2 using Supervised Neural Network algorithm.Result:61 significant different protein peaks were found between DAI and control group of brainstem,9 peaks were down-regulated and 52 up-regulated.60 discriminative protein peaks were found between DAI and control group of cerebral cortex,10 peaks were down-regulated and 50 up-regulated.56 significant different protein peaks were found between DAI and control group of cerebral medullary substance,10 peaks were down-regulated and 46 up-regulated.65 discriminative protein peaks were found between DAI and control group of cerebellum,32 peaks were down-regulated and 33 up-regulated.Compare with control group,M4963.30Da was down-regulated expression in cerebellum,while it was up-related expression in cerebrum and brainstem.M5634.78Da was down-regulated expression in cerebrum,up-related expression in cerebellum and brainstem.M6253.65Da was down-regulated expression in cerebellum and cerebrum,up-related expression in brainstem.M6714.37Da was down-regulated expression in cerebellum and cerebellum,up-related expression in brainstem.M7532.87 was down-regulated expression in cerebral medullary substance,up-related expression in cerebral cortex,cerebellum and brainstem.A diagnostic model was established to classify the two groups.Additionally,4 distinctively overexpressed peaks were identified:7059.21 and 1518.33 Da for DAI sections,and 5077.03 and 4327.20 Da for normal sections.The overall cross validation is 95.67%,sensitivity is 99.34%,specificity is 92.01%.Conclusion:MALDI-TOF IMS can be used to screen the different expressed proteins in normal group and DAI group.It can also conduct the mass imaging of different protein,in other to observe the distribution in the rat brain section.Besides,the ability of establishing diagnosis model of DAI has a good prospect in forensic pathology.