Molecular Mechanism Of Deep Hypothermic Circulatory Arrest Induced Brain Injury:The Research On Differential Expression Profiles Of Circular RNA

ObjectivesDeep hypothermic circulatory arrest(DHCA)is one of the indispensable interventions during aortic arch surgery and complex congenital cardiac surgery.DHCA is a common cause of temporary or persistent neurological dysfunction after cardiac surgery,and seriously affects the prognosis of patients undergoing cardiac surgery.The mechanisms underlying DHCA-induced brain injury remain poorly understood and the effective treatment or prevention strategies for DHCA-related brain injury are still lacking clinically.This study aimed to determine the changes in expression profiles of circular RNAs(circRNAs)in the hippocampus in rats underwent DHCA,with an attempt to explore the potential role of circRNAs in the brain injury associated with DHCA.MethodsAdult male Sprague-Dawley rats were subjected to cardiopulmonary bypass with DHCA.The DHCA group(n=16)underwent cardiopulmonary bypass(CPB),was cooled to 18?,cut off the circulation for 45 minutes,rewarmed and resuscitated to complete the DHCA experimental intervention;the Sham group(n=16)was only established peripheral intubation and accepted systemic heparinization without CPB.The hemodynamic performance and blood gas analysis were monitored during and after the operation.Brain injury was evaluated by the modified Neurological Severity Scores(mNSS)and histological as well as transmission electron microscope examinations.The expression profiles of circRNAs in the hippocampal tissues were screened by microarray.Quantitative real-time PCR(RT-qPCR)was used to validate the reliability of the microarray results.Bioinformatic algorithms were applied to predict target microRNA(miRNA)and target genes of differential circRNAs,construct a competing endogenous RNA(ceRNA)network,and Gene Ontology(GO)and Kyoto Encyclopedia of Genes and Genomes(KEGG)analyses were performed to explore the potential biological roles of the circRNAs.ResultsHemodynamics and blood gas analysis indexes were stable during and after the DHCA period.The mNSS of the DHCA group was significantly higher than the Sham group(P<.0001);the pathological damage score of H&E staining in DHCA group was significantly higher than the Sham group in the hippocampus CA1 area(P<.0001);Nissl staining showed the number of survival neurons in the DHCA group was significantly lower than the Sham group(P<.0001);transmission electron microscopy showed the mitochondria and endoplasmic reticulum of DHCA neurons were significantly damaged.Out of 14,145 circRNAs screened,56 were differentially expressed in the hippocampus between the DHCA and Sham operated rats,including 30 up-regulated and 26 down-regulated circRNAs.The expression changes of six selected circRNAs(up-regulated:rno_circRNA₀11190,no_circRNA₀12988,rno_circRNA₀00544;down-regulated:rno circRNA₀10393,rno_circRNA₀12043,mo_circRNA₀15149)were further confirmed by RT-qPCR.Bioinformatics analysis showed the enrichment of these confirmed circRNAs and their potential target mRNA in several KEGG pathways including histidine metabolism,arachidonic acid metabolism,adipocytokine signaling and cAMP signaling.ConclusionsIn this study,an animal experimental model of DHCA brain injury in rats was successfully established.The study identified changes in the circRNAs expression profiles in rat brain after DHCA and indicated possible involvements of these dysregulated circRNAs in DHCA brain injury.With the predicted circRNA-miRNA-mRNA network,this work provided new insight into the molecular mechanisms of brain injuries resulting from DHCA,and suggested a potential of targeting circRNAs for prevention and treatment of neurological dysfunction associated with DHCA.