Associate Professor Children's Hospital Colorado/University of Colorado, United States
Abstract: Introduction/
Objective: Infant cardiothoracic surgery with cardiopulmonary bypass (CPB) results in substantial physiologic disturbance but the extent of the underlying biochemical disruption has not been fully defined. Our group has previously identified significant changes in over 80% of measured circulating metabolites 24hrs after infant cardiothoracic surgery with CPB. Evaluation of changes in the circulating proteome, however, have been limited to date in part due to technical challenges with existing proteomic assays. In this study we sought to leverage novel proteomics techniques (SomaLogic Inc, Boulder, CO) to define changes in >1500 circulating proteins over the first 48hrs postoperatively following infant cardiothoracic surgery with CPB.
Methods: Infants < 6 months of age undergoing cardiothoracic surgery with CPB at Children’s Hospital Colorado were enrolled. Serum samples were obtained preoperatively after induction of anesthesia and at 2, 24, and 48hrs postoperatively and then frozen at -80oC for batch analysis. Samples (55µL) were analyzed using the SomaLogic SomaScan assay with a custom 1512 protein panel. Statistical analysis was performed using MetaboAnalyst 5.0. Partial Least Squares Discriminant Analysis (PLS-DA) was used to distinguish between sample time points based on their protein composition. Variable Importance in Projection and one-way ANOVA with post-hoc pairwise analysis were used to evaluate changes in individual proteins. Significance was defined as a false discovery rate (FDR) < 0.05. Proteins were labeled based on their HUGO gene nomenclature committee name.
Results: Thirty-nine patients were enrolled in this study. The global proteome differed substantially from baseline at all postoperative time points by PLS-DA (Figure 1A; Accuracy 0.85, R2=0.93, Q2=0.90, p< 0.0001) with the 2hr postoperative proteome demonstrating the greatest deviation from baseline. On an individual protein level, 1268/1512 proteins (83%) were significantly dysregulated in the postoperative period with an FDR < 0.05. The top 15 proteins contributing to the differentiation among groups by VIP score are shown in Figure 1B. The top 20 most significantly dysregulated proteins (p-values < 3x10-35) included multiple markers of cardiac injury (ANK2, TNNI3, TNNT2, ACTN2, SFRP1), cardiac metabolism (OXCT1, MDH1), inflammation (LBP, IL6, IL1RN, IGF2R, CTSV), fibroblast/extracellular matrix activity (FGFBP1, VIM, MMP17, LMOD1, FAP, CCN5), and neurologic injury (CNDP1, GFRA1).
Conclusions: Infant cardiothoracic surgery with CPB results in widespread disruption of the circulating proteome involving the majority of proteins measured in this study. Peak difference in the global proteome occurs early after surgery with ongoing deviation from baseline at 48hrs postoperatively. Our findings point to the complexity of the biochemical response to CPB and highlight the need to move beyond single biomarker strategies for the study of postoperative injury and remodeling.
