microRNA Expression Levels Change in Neonatal Patients During and After Exposure to Cardiopulmonary Bypass

ObjectivesThe systemic inflammation that occurs after exposure to cardiopulmonary bypass (CPB), which is especially severe in neonatal patients, is associated with poorer outcomes and is not well understood. In order to gain deeper insight into how exposure to bypass activates inflammatory responses in circulating leukocytes, we studied changes in microRNA (miRNA) expression during and after exposure to bypass. miRNAs are small non-coding RNAs that have important roles in modulating protein levels and function of cells. MethodsWe performed miRNA-Sequencing on leukocytes isolated from neonatal cardiopulmonary bypass patients (N=5) at 7 timepoints during the process of CPB, including prior to the initiation of bypass, during bypass, and at three time points during the first 24 hours after weaning from bypass. We identified significant differentially expressed miRNAs using generalized linear regression models, and miRNAs were defined as statistically significant using an FDR adjusted p <0.05. We identified gene targets of these miRNAs using the Targetscan database, and identified significantly enriched biological pathways for these gene targets. ResultsWe identified 54 miRNAs with differential expression during and after CPB. These miRNAs clustered into 3 groups, including miRNAs that were increased during and after CPB (3 miRNAs), miRNAs that decreased during and after CPB (10 miRNAs), and miRNAs that decreased during CPB but then increased 8-24 hours after CPB. 38.9% of the target genes of these miRNAs were significantly differentially expressed in our previous study. miRNAs with altered expression levels are predicted to significantly modulate pathways related to inflammation and signal transduction. ConclusionsThe unbiased profiling of the miRNA changes that occur in the circulating leukocytes of bypass patients provides deeper insight into the mechanisms that underpin the systemic inflammatory response that occurs in patients after exposure to cardiopulmonary bypass. These data will help the development of novel treatments and biomarkers for bypass associated inflammation.