A novel micropeptide, Slitharin, exerts cardioprotective effects in myocardial infarction

PURPOSE

Micropeptides are an emerging class of proteins that play critical roles in cell signaling. Here, we describe the discovery of a novel micropeptide, dubbed slitharin (Slt), in conditioned media from Cardiosphere-derived cells (CDCs), a therapeutic cardiac stromal cell type.

EXPERIMENTAL DESIGN

We performed mass spectrometry of peptide-enriched fractions from the conditioned media of CDCs and a therapeutically inert cell type (human dermal fibrobasts). We then evaluated the therapeutic capacity of the candidate peptide using an in vitro model of cardiomyocyte injury and a rat model of myocardial infarction.

RESULTS

We identified a novel 24-amino acid micropeptide (dubbed Slitharin [Slt]) with a non-canonical leucine start codon, arising from long intergenic non-coding (LINC) RNA 2099. Neonatal rat ventricular myocytes (NRVMs) exposed to Slt were protected from hypoxic injury in vitro compared to a vehicle or scrambled control. Transcriptomic analysis of cardiomyocytes exposed to Slt reveals cytoprotective capacity, putatively through regulation of stress-induced MAPK-ERK. Slt also exerted cardioprotective effects in rats with myocardial infarction as shown by reduced infarct size 48 h post-injury. Conclusions and clinical relavance: Thus, Slt is a non-coding RNA-derived micropeptide, identified in the extracellular space, with a potential cardioprotective function.

A Noninvasive Circulating Signature of Combined Right Ventricular Pressure and Volume Overload in Tetralogy of Fallot/Pulmonary Atresia/Major Aortopulmonary Collateral Arteries

Background: Despite surgical advances, children with tetralogy of Fallot/pulmonary atresia/major aortopulmonary collaterals (TOF/PA/MAPCAs) are subject to chronic right ventricular (RV) pressure and volume overload. Current diagnostic tools do not identify adverse myocardial remodeling and cannot predict progression to RV failure. We sought to identify a noninvasive, circulating signature of the systemic response to right heart stress to follow disease progression. Methods: Longitudinal data were collected from patients with TOF/PA/MAPCAs (N = 5) at the time of (1) early RV pressure overload and (2) late RV pressure and volume overload. Plasma protein and microRNA expression were evaluated using high-throughput data-independent mass spectroscopy and Agilent miR Microarray, respectively. Results: At the time of early RV pressure overload, median patient age was 0.34 years (0.02-9.37), with systemic RV pressures, moderate-severe hypertrophy, and preserved systolic function. Late RV pressure and volume overload occurred at a median age of 4.08 years (1.51-10.83), with moderate RV hypertrophy and dilation, and low normal RV function; 277 proteins were significantly dysregulated (log2FC ≥0.6/≤-0.6, FDR≤0.05), predicting downregulation in lipid transport (apolipoproteins), fibrinolytic system, and extracellular matrix structural proteins (talin 1, profilin 1); and upregulation in the respiratory burst. Increasing RV size and decreasing RV function correlated with decreasing structural protein expression. Similarly, miR expression predicted downregulation of extracellular matrix-receptor interactions and upregulation in collagen synthesis. Conclusion: To our knowledge, we show for the first time a noninvasive protein and miR signature reflecting the systemic response to adverse RV myocardial remodeling in TOF/PA/MAPCAs which could be used to follow disease progression.

High-Throughput Single-Cell Proteomic Analysis of Organ-Derived Heterogeneous Cell Populations by Nanoflow Dual-Trap Single-Column Liquid Chromatography

Identification and proteomic characterization of rare cell types within complex organ-derived cell mixtures is best accomplished by label-free quantitative mass spectrometry. High throughput is required to rapidly survey hundreds to thousands of individual cells to adequately represent rare populations. Here we present parallelized nanoflow dual-trap single-column liquid chromatography (nanoDTSC) operating at 15 min of total run time per cell with peptides quantified over 11.5 min using standard commercial components, thus offering an accessible and efficient LC solution to analyze 96 single cells per day. At this throughput, nanoDTSC quantified over 1000 proteins in individual cardiomyocytes and heterogeneous populations of single cells from the aorta.

Plasma Metabolomics Predicts Chemotherapy Response in Advanced Pancreatic Cancer

Pancreatic cancer (PC) is one of the deadliest cancers. Developing biomarkers for chemotherapeutic response prediction is crucial for improving the dismal prognosis of advanced-PC patients (pts). To evaluate the potential of plasma metabolites as predictors of the response to chemotherapy for PC patients, we analyzed plasma metabolites using high-performance liquid chromatography-mass spectrometry from 31 cachectic, advanced-PC subjects enrolled into the PANCAX-1 (NCT02400398) prospective trial to receive a jejunal tube peptide-based diet for 12 weeks and who were planned for palliative chemotherapy. Overall, there were statistically significant differences in the levels of intermediates of multiple metabolic pathways in pts with a partial response (PR)/stable disease (SD) vs. progressive disease (PD) to chemotherapy. When stratified by the chemotherapy regimen, PD after 5-fluorouracil-based chemotherapy (e.g., FOLFIRINOX) was associated with decreased levels of amino acids (AAs). For gemcitabine-based chemotherapy (e.g., gemcitabine/nab-paclitaxel), PD was associated with increased levels of intermediates of glycolysis, the TCA cycle, nucleoside synthesis, and bile acid metabolism. These results demonstrate the feasibility of plasma metabolomics in a prospective cohort of advanced-PC patients for assessing the effect of enteral feeding as their primary source of nutrition. Metabolic signatures unique to FOLFIRINOX or gemcitabine/nab-paclitaxel may be predictive of a patient's response and warrant further study.

Initial recommendations for performing, benchmarking and reporting single-cell proteomics experiments

Analyzing proteins from single cells by tandem mass spectrometry (MS) has recently become technically feasible. While such analysis has the potential to accurately quantify thousands of proteins across thousands of single cells, the accuracy and reproducibility of the results may be undermined by numerous factors affecting experimental design, sample preparation, data acquisition and data analysis. We expect that broadly accepted community guidelines and standardized metrics will enhance rigor, data quality and alignment between laboratories. Here we propose best practices, quality controls and data-reporting recommendations to assist in the broad adoption of reliable quantitative workflows for single-cell proteomics. Resources and discussion forums are available at https://single-cell.net/guidelines .

High Throughput Single Cell Proteomic Analysis of Organ Derived Heterogeneous Cell Populations by Nanoflow Dual Trap Single Column Liquid Chromatography

Identification and proteomic characterization of rare cell types within complex organ derived cell mixtures is best accomplished by label-free quantitative mass spectrometry. High throughput is required to rapidly survey hundreds to thousands of individual cells to adequately represent rare populations. Here we present parallelized nanoflow dual-trap single-column liquid chromatography (nanoDTSC) operating at 15 minutes of total run time per cell with peptides quantified over 11.5 minutes using standard commercial components, thus offering an accessible and efficient LC solution to analyze 96 single-cells per day. At this throughput, nanoDTSC quantified over 1,000 proteins in individual cardiomyocytes and heterogenous populations of single cells from aorta.

530. Characterization of the Proteomic Changes via SARS-CoV-2 Infection or Vaccination in the COVID-19 Community Research Partnership (CCRP)

Background

There remain important gaps in knowledge concerning the effects of SARS-CoV-2 infection or vaccination on the human blood proteome.

Methods

The CCRP is a longitudinal surveillance study with information on SARS-CoV-2 infections, vaccinations and associated humoral immune responses in over 37,000 individuals. We selected a sample of blood spots cards (n=510) from serum antibody studies obtained between October 2020 and April 2021 for mass spectrometry proteomics analysis covering 540 unique plasma proteins. We analyzed the quantified protein differences based on dried blood samples obtained before and after infection or vaccination among previously non-infected individuals (immune naïve) after adjustment for batch effects, age, sex, or prior diagnosis of cancer, cardiovascular or autoimmune disease, or diabetes. The majority of infected individuals were minimally symptomatic. Differentially expressed proteins were considered significant with an FDR adjusted p-value of < 0.05 and log2 fold change (L2FC) >0.2.

Results

We found 11 and 12 proteins differentially expressed proteins in the naïve/infected and naïve/vaccinated people respectively, of which 10 were shared. Hepatocyte growth factor receptor (HGF) was upregulated (L2FC 0.24; p < 0.001) only in those who were infected while fibrillarin (L2FC -0.24; p< 0.001) and lambda-crystallin homolog (L2FC -0.29, p < 0.001) were downregulated only in the vaccinated samples (Fig 1). The remaining DE protein were associated with a wide array of functions including metabolic, cytostructural, extracellular matrix and DNA regulatory processes.

Conclusion

We found changes in the proteome both from infection and vaccination. HGF, elevated in the infected, has been associated with endothelial inflammation, upregulation of pro-inflammatory cytokines to reduce lung fibrosis and is known to promote tissue repair. Fibrillarin, downregulated in the vaccinated, has been associated with higher rates of bacterial and viral clearance, inflammation reduction, and increased cell survival. These findings suggest detectable complex inflammation from mild to moderate infections. Further investigation is required to understand the mechanism of action and clinical implication of these findings.

Disclosures

All Authors: No reported disclosures.

Prospective changes in diastolic function in patients with rheumatoid arthritis

Background

Diastolic dysfunction (DD) is more prevalent in patients with rheumatoid arthritis (RA) compared to the general population. However, its evolution over time and its significant clinical predictors remain uncharacterized. We report on baseline and prospective changes in diastolic function and its associated RA and cardiovascular (CV) predictors.

Methods

In this study, 158 RA patients without clinical CV disease (CVD) were enrolled and followed up at 4 to 6 years, undergoing baseline and follow-up echocardiography to assess for DD, as well as extensive characterization of RA disease activity and CV risk factors. Novel measures of myocardial inflammation and perfusion were obtained at baseline only. Using baseline and follow-up composite DD (E/e′, Left Atrial Volume Index (LAVI) or peak tricuspid regurgitation (TR) velocity; ≥ 1 in top 25%) as the outcome, multivariable regression models were constructed to identify predictors of DD.

Results

DD was prevalent in RA patients without clinical heart failure (HF) (40.7% at baseline) and significantly progressed on follow-up (to 57.9%). Baseline composite DD was associated with baseline RA disease activity (Clinical Disease Activity Index; CDAI) (OR 1.39; 95% CI 1.02–1.90; p=0.034). Several individual diastolic parameters (baseline E/e′ and LAVI) were associated with troponin-I and brain natriuretic peptide (BNP). Baseline and follow-up composite DD, however, were not associated with myocardial inflammation, myocardial microvascular dysfunction, or subclinical atherosclerosis.

Conclusions

DD is prevalent in RA patients without clinical HF and increases to >50% over time. Higher RA disease activity at baseline predicted baseline composite DD. Future longitudinal studies should explore whether adverse changes in diastolic function lead to clinical HF and are attenuated by disease-modifying antirheumatic drugs (DMARDs).

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-022-02864-0.

The Molecular Twin platform: a novel machine learning tool for democratization of precision cancer medicine

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Background: Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive cancers. Contemporary analyses focused on a handful of molecular and clinical variables combined with machine learning algorithms (MLA) are unable to accurately predict therapy outcomes. Here, we use the Molecular Twin multi-omic analytical platform that evaluates tumor and host features extracted from 10 multi-omic analytes and provides an array of MLA, including a Parsimonious Biomarker Model that can predict survival and recurrence with limited analytic burden, while maintaining a high degree of fidelity. Methods: Retrospectively collected serum and tissue samples from 74 patients with Stage I/II resectable PDAC were subjected to targeted NGS DNA sequencing, whole transcriptome RNA sequencing, paired tissue proteomics, unpaired serum proteomics, lipidomics and computational pathology. Analytes including plasma proteins, RNA fusions, tissue proteins, plasma lipids, RNA gene expressions, CNVs, INDELS, SNVs and tumor nuclei characteristics, were processed to obtain a panel of 6363 features. 1024 single-omic and multi-omics feature combinations generated from this panel served as input for 7 different types of MLA to predict binary survival (SR) and disease recurrence (DR) outcomes. The resultant 70 single and 7098 multi-omic biomarker models were evaluated for positive predictive value (PPV) and accuracy (ACC) in predicting DR and SR, and feature proportions learned by each ML model using leave-one-patient-out cross-validation strategy. By recursively eliminating features with low importance, we developed progressively parsimonious biomarker models for predicting SR and DR. Results: Our top model was multi-omic and predicted the SR with ACC = 0.85, PPV = 0.87 and the DR with ACC = 0.90, and PPV = 0.91. It outperformed all models based only on one single analyte type including plasma protein, RNA fusion, tissue protein, plasma lipid, clinical, RNA gene expression, tumor nuclei characteristics, CNV, INDEL and SNV, in predicting the SR. This model contained predominantly plasma protein features. Interestingly, less accurate models contained a greater proportion of other features in addition to plasma proteins. Parsimonious feature reduction of the top model stabilized at 589 features yielding an ACC = 0.85, and PPV = 0.85, comparable to the intact model. Conclusions: This proof-of-concept of the Molecular Twin precision medicine platform applied in PDAC reveals the potential of our unique MLA to provide a novel parsimonious biomarker panel with similar fidelity as much larger biomarker panels. If these results are reproduced on larger datasets, across tumor types, the Molecular Twin platform would have significant potential to democratize precision cancer medicine by discovering smaller biomarker panels with the predictive performance of much larger ones thus reducing cost and simplifying assays.

Metabolomics in advanced pancreatic cancer (PC) patients (pts) achieving weight stability on enteral feeding for cachexia

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Background: We previously showed that enteral feeding was associated with weight stability and compositional changes in the gut microbiome with increased abundance of the gram-negative genera Veillonella over time. Here, we evaluated the potential of plasma metabolites as predictors of weight stability and high Veillonella abundance in enteral fed pts. Methods: The PANCAX-1 (NCT02400398) prospective trial enrolled 31 cachectic advanced PC pts to receive jejunal tube peptide-based diet for 12 weeks (wks) who were planned for standard chemotherapy. In preplanned exploratory analyses, serial blood samples were collected over 12 wks of enteral feeding. Up to 219 plasma metabolites were analyzed by mass spectrometry and high-performance liquid chromatography. Analytes were compared by relative area under the curve (AUC) and differences evaluated by two-sample t-tests. Pts were stratified by weight stable (WS, defined as weight change < 0.1 kg/baseline BMI-unit over 12 wks of enteral feeding) vs. weight unstable (WU) and high (HV) vs. low Veillonella (LV) abundance (defined by dichotomizing at the mean relative abundance in WS pts). Results: Of 31 cachectic pts enrolled into PANCAX-1, a total of 55 blood samples were collected from 28 pts for plasma metabolomics. Out of 16 evaluable pts, 62.5% receiving enteral feeding met the primary endpoint of weight stability at 12 wks. Plasma metabolomics in 10 pts showed that WU pts (n = 4) had significantly decreased levels of essential amino acids (AAs, L-histidine, L-phenylalanine) and non-essential AAs (L-citrulline, L-tyrosine, all p < 0.05) than WS pts (n = 6) at the end of 12 wks of enteral feeding. In 7 WS pts with complete serial sets of blood samples available, enteral feeding over 12 wks was associated with increases in markers of muscle mass (creatinine) but decreases in nucleotide precursors (all p < 0.05) compared to baseline. Comparison of baseline metabolites between 6 WS pts with HV and 4 WU pts with LV showed that HV was associated with increases in the nucleotide dCDP and essential AA L-isoleucine but decreased TCA cycle metabolite alpha-ketoglutarate (all p < 0.05). Decreases in lactic acid was observed at 12 wks of enteral feeding in HV pts when compared to baseline (p < 0.05). Conclusions: Our findings are hypothesis-generating in that metabolites unique to weight stability and Veillonella abundance may inform future studies of anti-cachexia therapies involving enteral feeding or microbial modulation.

Plasma metabolomics to predict chemotherapy (CTX) response in advanced pancreatic cancer (PC) patients (pts) on enteral feeding for cachexia

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Background: We evaluated the potential of plasma metabolites as predictors of response to CTX in a prospective cohort of pts who received enteral feeding for cachexia and advanced PC. Methods: The PANCAX-1 (NCT02400398) prospective trial enrolled 31 cachectic advanced PC pts to receive jejunal tube peptide-based diet for 12 weeks (wks) who were planned for palliative CTX. Out of 16 evaluable pts, 62.5% receiving enteral feeding met the primary endpoint of weight stability at 12 wks. As part of an exploratory analysis of the PANCAX-1 trial, serial blood samples were collected at 3 predefined timepoints over 12 wks of enteral feeding. Up to 219 plasma metabolites were analyzed by mass spectrometry and high-performance liquid chromatography. Analytes were compared by relative area under the curve (AUC) and differences evaluated by two-sample t-tests. The mean AUC was used in pts with metabolites measured from > 1 timepoint of collection. Pts were stratified by stable disease (SD), partial response (PR), or progressive disease (PD) as best overall response to standard CTX. Results: Of 31 pts with advanced PC prospectively enrolled for enteral feeding, there were 55 blood samples collected from 28 pts available for plasma metabolomics. 20/28 (71%) pts received first-line CTX, the majority of whom (90%) received gemcitabine-based CTX. There were 2 PRs (7%) and 10 with SD (36%) as best response to CTX. Overall, there were statistically significant differences in levels of intermediates involved in multiple metabolic pathways including glycolysis, the tricarboxylic acid (TCA) cycle, fatty acid synthesis, and nucleoside synthesis in pts with PR/SD vs. PD to CTX (all p < 0.05). When stratified by CTX regimen, PD to 5-fluorouracil-based CTX (e.g., FOLFIRINOX) was associated with decreased levels of essential amino acids (AAs, L-leucine, L-methionine, L-tryptophan) and non-essential AAs (L-arginine, L-serine, L-tyrosine, all p < 0.05). For gemcitabine-based CTX (e.g., gemcitabine/nab-paclitaxel), PD was associated with increased levels of intermediates of glycolysis (pyruvate), TCA cycle (L-glutamate), nucleoside synthesis (xanthine), and bile acid metabolism (taurocholic acid, all p < 0.05). Conclusions: We are the first to demonstrate the feasibility of plasma metabolomics in a prospective cohort of advanced PC pts on enteral feeding as their primary source of nutrition. Metabolic signatures unique to FOLFIRINOX or gemcitabine/nab-paclitaxel may be predictive of response and warrant further study.

pH/Acetonitrile-Gradient Reversed-Phase Fractionation of Enriched Hyper-Citrullinated Library in Combination with LC-MS/MS Analysis for Confident Identification of Citrullinated Peptides

Citrullination, the Ca²⁺-driven enzymatic conversion of arginine residues to citrulline, is a posttranslational modification, implicated in several physiological and pathological processes. Several methods to detect citrullinated proteins have been developed, including color development reagent, fluorescence, phenylglyoxal, and antibody-based methods. These methods yet suffer from limitations in sensitivity, specificity, or citrullinated site determination. Mass spectrometry (MS)-based proteomic analysis has emerged as a promising method to resolve these problems. However, due to low abundance of citrullinated proteins and similar MS features to deamidation of asparagine and glutamine, confident identification of citrullinated proteome is challenging. Here, we present a systematic approach to identify a compendium of steps to enhance the number of detected citrullinated residue and implement diagnostic MS feature that allow the confidence of MS-based identifications. Our method is based on the concept of generation of hyper-citrullinated library with high-pH reversed-phase peptide fractionation that allows to enrich in low abundance citrullinated peptides and amplify the effect of charge loss upon citrullination. Application of our approach to complex global citrullino-proteome datasets demonstrates the confident assessment of citrullinated peptides, thereby enhancing the size and functional interpretation of citrullinated proteomes.

Longitudinal SARS-CoV-2 mRNA Vaccine-Induced Humoral Immune Responses in Patients with Cancer

Longitudinal studies of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine-induced immune responses in patients with cancer are needed to optimize clinical care. In a prospective cohort study of 366 (291 vaccinated) patients, we measured antibody levels [anti-spike (IgG-(S-RBD) and anti-nucleocapsid immunoglobulin] at three time points. Antibody level trajectories and frequency of breakthrough infections were evaluated by tumor type and timing of treatment relative to vaccination. IgG-(S-RBD) at peak response (median = 42 days after dose 2) was higher (P = 0.002) and remained higher after 4 to 6 months (P = 0.003) in patients receiving mRNA-1273 compared with BNT162b2. Patients with solid tumors attained higher peak levels (P = 0.001) and sustained levels after 4 to 6 months (P < 0.001) compared with those with hematologic malignancies. B-cell targeted treatment reduced peak (P = 0.001) and sustained antibody responses (P = 0.003). Solid tumor patients receiving immune checkpoint inhibitors before vaccination had lower sustained antibody levels than those who received treatment after vaccination (P = 0.043). Two (0.69%) vaccinated and one (1.9%) unvaccinated patient had severe COVID-19 illness during follow-up. Our study shows variation in sustained antibody responses across cancer populations receiving various therapeutic modalities, with important implications for vaccine booster timing and patient selection. SIGNIFICANCE: Long-term studies of immunogenicity of SARS-CoV-2 vaccines in patients with cancer are needed to inform evidence-based guidelines for booster vaccinations and to tailor sequence and timing of vaccinations to elicit improved humoral responses.

Autophagy-mitophagy induction attenuates cardiovascular inflammation in a murine model of Kawasaki disease vasculitis

Kawasaki disease (KD) is the leading cause of acquired heart disease among children. Murine and human data suggest that the NLRP3-IL-1β pathway is the main driver of KD pathophysiology. NLRP3 can be activated during defective autophagy/mitophagy. We used the Lactobacillus casei cell wall extract (LCWE) murine model of KD vasculitis, to examine the role of autophagy/mitophagy on cardiovascular lesion development. LCWE-injected mice had impaired autophagy/mitophagy and increased levels of ROS in cardiovascular lesions, together with increased systemic 8-OHdG release. Enhanced autophagic flux significantly reduced cardiovascular lesions in LCWE-injected mice, whereas autophagy blockade increased inflammation. Vascular smooth muscle cell specific deletion of Atg16l1 and global Parkin-/- significantly increased disease formation, supporting the importance of autophagy/mitophagy in this model. Ogg1-/- mice had significantly increased lesions with increased NLRP3 activity, whereas treatment with MitoQ, reduced vascular tissue inflammation, ROS production and systemic 8-OHdG release. Treatment with MN58b or Metformin (increasing AMPK and reducing ROS), resulted in decreased disease formation. Our results demonstrate that impaired autophagy/mitophagy and ROS-dependent damage exacerbate the development of murine KD vasculitis. This pathway can be efficiently targeted to reduce disease severity. These findings enhance our understanding of KD pathogenesis and identify novel therapeutic avenues for KD treatment.

HLA class I-associated expansion of TRBV11-2 T cells in multisystem inflammatory syndrome in children

Multisystem inflammatory syndrome in children (MIS-C), a hyperinflammatory syndrome associated with SARS-CoV-2 infection, shares clinical features with toxic shock syndrome, which is triggered by bacterial superantigens. Superantigen specificity for different Vβ chains results in Vβ skewing, whereby T cells with specific Vβ chains and diverse antigen specificity are overrepresented in the T cell receptor (TCR) repertoire. Here, we characterized the TCR repertoire of MIS-C patients and found a profound expansion of TCRβ variable gene 11-2 (TRBV11-2), with up to 24% of clonal T cell space occupied by TRBV11-2 T cells, which correlated with MIS-C severity and serum cytokine levels. Analysis of TRBJ gene usage and complementarity-determining region 3 (CDR3) length distribution of MIS-C expanded TRBV11-2 clones revealed extensive junctional diversity. Patients with TRBV11-2 expansion shared HLA class I alleles A02, B35, and C04, indicating what we believe is a novel mechanism for CDR3-independent T cell expansion. In silico modeling indicated that polyacidic residues in the Vβ chain encoded by TRBV11-2 (Vβ21.3) strongly interact with the superantigen-like motif of SARS-CoV-2 spike glycoprotein, suggesting that unprocessed SARS-CoV-2 spike may directly mediate TRBV11-2 expansion. Overall, our data indicate that a CDR3-independent interaction between SARS-CoV-2 spike and TCR leads to T cell expansion and possibly activation, which may account for the clinical presentation of MIS-C.

Identification of a unique TCR repertoire, consistent with a superantigen selection process in Children with Multi-system Inflammatory Syndrome

Multisystem Inflammatory Syndrome in Children (MIS-C), a hyperinflammatory syndrome associated with SARS-CoV-2 infection, shares many clinical features with toxic shock syndrome, which is triggered by bacterial superantigens. The superantigen specificity for binding different Vβ-chains results in Vβ-skewing, whereby T cells with specific Vβ-chains and diverse antigen specificity are overrepresented in the TCR repertoire. Here, we characterized the TCR repertoire of MIS-C patients and found a profound expansion of TCR Βeta Variable gene (TRBV)11-2. Furthermore, TRBV11-2 skewing was remarkably correlated with MIS-C severity and serum cytokine levels. Further analysis of TRBJ gene usage and CDR3 length distribution of MIS-C expanding TRBV11-2 clones revealed extensive junctional diversity, indicating a superantigen-mediated selection process for TRBV expansion. In silico modelling indicates that polyacidic residues in TCR Vβ11-2 engage in strong interactions with the superantigen-like motif of SARS-CoV-2 spike glycoprotein. Overall, our data indicate that the immune response in MIS-C is consistent with superantigenic activation.

Coronary Vascular Function and Cardiomyocyte Injury: A Report From the WISE-CVD

OBJECTIVE

Women with symptoms or signs of myocardial ischemia but no obstructive coronary artery disease (INOCA) often have coronary vascular dysfunction and elevated risk for adverse cardiovascular events. We hypothesized that u-hscTnI (ultra-high-sensitivity cardiac troponin I), a sensitive indicator of ischemic cardiomyocyte injury, is associated with coronary vascular dysfunction in women with INOCA. Approach and Results: Women (N=263) with INOCA enrolled in the WISE-CVD study (Women's Ischemic Syndrome Evaluation-Coronary Vascular Dysfunction) underwent invasive coronary vascular function testing and u-hscTnI measurements (Simoa HD-1 Analyzer; Quanterix Corporation, Lexington, MA). Logistic regression models, adjusted for traditional cardiovascular risk factors were used to evaluate associations between u-hscTnI and coronary vascular function. Women with coronary vascular dysfunction (microvascular constriction and limited coronary epicardial dilation) had higher plasma u-hscTnI levels (both P=0.001). u-hscTnI levels were associated with microvascular constriction (odds ratio, 1.38 per doubling of u-hscTnI [95% CI, 1.03-1.84]; P=0.033) and limited coronary epicardial dilation (odds ratio, 1.37 per doubling of u-hscTnI [95% CI, 1.04-1.81]; P=0.026). u-hscTnI levels were not associated with microvascular dilation or coronary epicardial constriction.

CONCLUSIONS

Our findings indicate that higher u-hscTnI is associated with coronary vascular dysfunction in women with INOCA. This suggests that ischemic cardiomyocyte injury in the setting of coronary vascular dysfunction has the potential to contribute to adverse cardiovascular outcomes observed in these women. Additional studies are needed to confirm and investigate mechanisms underlying these findings in INOCA. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT00832702.

Human iPSC-Derived Blood-Brain Barrier Chips Enable Disease Modeling and Personalized Medicine Applications

The blood-brain barrier (BBB) tightly regulates the entry of solutes from blood into the brain and is disrupted in several neurological diseases. Using Organ-Chip technology, we created an entirely human BBB-Chip with induced pluripotent stem cell (iPSC)-derived brain microvascular endothelial-like cells (iBMECs), astrocytes, and neurons. The iBMECs formed a tight monolayer that expressed markers specific to brain vasculature. The BBB-Chip exhibited physiologically relevant transendothelial electrical resistance and accurately predicted blood-to-brain permeability of pharmacologics. Upon perfusing the vascular lumen with whole blood, the microengineered capillary wall protected neural cells from plasma-induced toxicity. Patient-derived iPSCs from individuals with neurological diseases predicted disease-specific lack of transporters and disruption of barrier integrity. By combining Organ-Chip technology and human iPSC-derived tissue, we have created a neurovascular unit that recapitulates complex BBB functions, provides a platform for modeling inheritable neurological disorders, and advances drug screening, as well as personalized medicine.

The continuing evolution of cardiac troponin I biomarker analysis: from protein to proteoform

INTRODUCTION

The troponin complex consists of three proteins that fundamentally couple excitation with contraction. Circulating cardiac-specific Troponin I (cTnI) serves as diagnostic biomarker tools for risk stratification of acute coronary syndromes and acute myocardial infarction (MI). Within the heart, cTnI oscillates between inactive and active conformations to either block or disinhibit actinomyosin formation. This molecular mechanism is fine-tuned through extensive protein modifications whose profiles are maladaptively altered with co-morbidities including hypertrophic cardiomyopathy, diabetes, and heart failure. Technological advances in analytical platforms over the last decade enable routine baseline cTnI analysis in patients without cardiovascular complications, and hold potential to expand cTnI readouts that include modified cTnI proteoforms. Areas covered: This review covers the current state, advances, and prospects of analytical platforms that now enable routine baseline cTnI analysis in patients. In parallel, improved mass spectrometry instrumentation and workflows already reveal an array of modified cTnI proteoforms with promising diagnostic implications. Expert commentary: New analytical capabilities provide clinicians and researchers with an opportunity to address important questions surrounding circulating cTnI in the improved diagnosis of specific patient cohorts. These techniques also hold considerable promise for new predictive and prescriptive applications for individualized profiling and improve patient care.

Abstract 198: Multipotent Placenta-derived Cdx2 Cells Possess in vitro and in vivo Cardiomyogenic Potential

Stem cell-based therapies for cardiac regeneration are of crucial importance and an ideal cell-type is yet to be established. We previously reported that fetal cells from placenta “home” to injured maternal heart and approximately 40% (40/100) of the migrating cells expressed homeodomain protein Cdx2. This interesting observation led us to hypothesize that placental Cdx2 could be a novel cell target for cardiac differentiation. To understand this phenomenon, we employed a cre-lox strategy that labeled Cdx2 cells in placenta with e-GFP and induced myocardial infarction (MI) in pregnant mice at mid-gestation. The maternal heart was analyzed 4 weeks post-MI for the presence of Cdx2-eGFP-derived cardiomyocytes. Additionally, Cdx2 cells were isolated from late-gestation placenta and assayed for cardiac differentiation in vitro followed by live cell imaging. Phenotypic and whole-cell proteomic analysis, clonal and vascular lineage differentiation and immune profiling were carried out subsequently. We observed that Cdx2 cells migrated to injured maternal hearts and differentiated into cardiomyocytes highlighting the functional significance of fetal-maternal stem cell transfer. Additionally, isolated Cdx2 cells from the late placenta differentiated into spontaneously beating cardiomyocytes and expressed structural proteins cardiac troponin T(cTnT), α-sarcomeric actinin and gap junction protein Cx43. These cells underwent clonal expansion and differentiated into endothelial and smooth muscle lineages in culture indicative of their multipotent nature. Low expression of MHC molecules and other components of the immune-response, infer that these cells possess the ability to evade host immune surveillance. Proteomic analysis demonstrated that 145 proteins were uniquely identified in the Cdx2 cells compared to embryonic stem cells. These protein networks reflected an increased activation of functions involving migration, fertility, homing, and chemotaxis. Our study is the first to demonstrate that Cdx2 may play a role in cardiac differentiation and delineate multipotent cells in placenta with an inherent “homing” ability. These findings point to a potential role for Cdx2 cells in cardiac regenerative therapies using allogeneic cells.

Abstract 2216: A novel MRM-based mass spectrometry assay to quantify HMGB1

Background: High mobility group box 1 (HMGB1) is a versatile protein with dual roles. Within the cell, this highly conserved chromosomal protein functions as a DNA chaperone. Outside of the cell, it functions as the prototypical damage-associated molecular pattern. There is significant evidence that HMGB1 dysfunction contributes to cancer development, particularly in mesothelioma, where its role in carcinogenesis is better defined.

Goal: To develop a mass spectrometry based immune-multiple reaction monitoring (iMRM) assay to quantify HMGB1 and its disease-associated post-translationally modified forms.

Methods: Mesothelioma cell lines (Ren, Phi and PP-Mill) known to secrete HMGB1 were used. Concentrated cell line supernatants, anti-HMGB1 antibody-loaded magnetic beads were incubated overnight. Beads were extensively washed and the HMGB1 released from the beads was enzymatically digested prior to targeted MRM mass spectrometry. Known quantity of N15 labeled synthetic peptides were spiked in to be used as internal standards to assess the total protein concentrations as well as the acetylated modified peptides that encompass the Lys residue. To ensure tight reproducibility during sample processing, we developed an automated workflow from enrichment to digestion with % coefficient of variance of less than 20%.

Results: Two multiplex MRM assays were developed for HMGB1: 1) total HMGB1 protein assay based on trypsin digested peptides and 2) Acetylated HMGB1 assay based on Endoproteinase GluC (Staphylococcus aureus Protease V8) digestion to obtain the peptides containing hyper-acetylated Lysine residues, which are not located within a suitable tryptic peptide. Four significant milestones were accomplished. i) We optimized the HMGB1 liquid chromatography and mass spectrometry performance through the utilization of signature synthesized peptides representing the common amino acid sequence and potential acetylated regions. The calibration curves for both peptides based on the ratio of light and heavy isotopic labeled internal standards were achieved. LLOD and LLOQ and the inter and intra-day variability of the iMRM assay have been achieved. ii) A robust immuno-capture protocol was established. The final protocol included isolation of HMGB1 using a capture antibody followed by protein release, denaturation, reduction, alkylation and digestion. To date, we have optimized the conditions for HMGB1 attachment to antibody, antibody coupling to magnetic beads, the wash and elution steps. iii) The protocol was applied to quantify HMGB1 in mesothelioma cell lines. HMGB1 was measured in cytoplasm, nucleus and supernatant from the cell lines. iv) Finally, the assay was adapted to work on human plasma samples.

Conclusion: We successfully developed the iMRM workflow for quantification of total HMGB1 and acetylated HMGB1 based on the measurement of the target signature peptides in HMGB1.

Citation Format: Dawn Zhaohui Chen, Weston R. Spivia, Yang Gao, Jennifer Van Eyk, Shreya Kanodia. A novel MRM-based mass spectrometry assay to quantify HMGB1 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2216. doi:10.1158/1538-7445.AM2017-2216

Whole Exome Sequencing to Identify Genetic Variants Associated with Raised Atherosclerotic Lesions in Young Persons

We investigated the influence of genetic variants on atherosclerosis using whole exome sequencing in cases and controls from the autopsy study “Pathobiological Determinants of Atherosclerosis in Youth (PDAY)”. We identified a PDAY case group with the highest total amounts of raised lesions (n = 359) for comparisons with a control group with no detectable raised lesions (n = 626). In addition to the standard exome capture, we included genome-wide proximal promoter regions that contain sequences that regulate gene expression. Our statistical analyses included single variant analysis for common variants (MAF > 0.01) and rare variant analysis for low frequency and rare variants (MAF < 0.05). In addition, we investigated known CAD genes previously identified by meta-analysis of GWAS studies. We did not identify individual common variants that reached exome-wide significance using single variant analysis. In analysis limited to 60 CAD genes, we detected strong associations with COL4A2/COL4A1 that also previously showed associations with myocardial infarction and arterial stiffness, as well as coronary artery calcification. Likewise, rare variant analysis did not identify genes that reached exome-wide significance. Among the 60 CAD genes, the strongest association was with NBEAL1 that was also identified in gene-based analysis of whole exome sequencing for early onset myocardial infarction.

Modeling Psychomotor Retardation using iPSCs from MCT8-Deficient Patients Indicates a Prominent Role for the Blood-Brain Barrier

Inactivating mutations in the thyroid hormone (TH) transporter Monocarboxylate transporter 8 (MCT8) cause severe psychomotor retardation in children. Animal models do not reflect the biology of the human disease. Using patient-specific induced pluripotent stem cells (iPSCs), we generated MCT8-deficient neural cells that showed normal TH-dependent neuronal properties and maturation. However, the blood-brain barrier (BBB) controls TH entry into the brain, and reduced TH availability to neural cells could instead underlie the diseased phenotype. To test potential BBB involvement, we generated an iPSC-based BBB model of MCT8 deficiency, and we found that MCT8 was necessary for polarized influx of the active form of TH across the BBB. We also found that a candidate drug did not appreciably cross the mutant BBB. Our results therefore clarify the underlying physiological basis of this disorder, and they suggest that circumventing the diseased BBB to deliver active TH to the brain could be a viable therapeutic strategy.

Metabolomic Identification of Subtypes of Nonalcoholic Steatohepatitis

BACKGROUND & AIMS

Nonalcoholic fatty liver disease (NAFLD) is a consequence of defects in diverse metabolic pathways that involve hepatic accumulation of triglycerides. Features of these aberrations might determine whether NAFLD progresses to nonalcoholic steatohepatitis (NASH). We investigated whether the diverse defects observed in patients with NAFLD are caused by different NAFLD subtypes with specific serum metabolomic profiles, and whether these can distinguish patients with NASH from patients with simple steatosis.

METHODS

We collected liver and serum from methionine adenosyltransferase 1a knockout (MAT1A-KO) mice, which have chronically low levels of hepatic S-adenosylmethionine (SAMe) and spontaneously develop steatohepatitis, as well as C57Bl/6 mice (controls); the metabolomes of all samples were determined. We also analyzed serum metabolomes of 535 patients with biopsy-proven NAFLD (353 with simple steatosis and 182 with NASH) and compared them with serum metabolomes of mice. MAT1A-KO mice were also given SAMe (30 mg/kg/day for 8 weeks); liver samples were collected and analyzed histologically for steatohepatitis.

RESULTS

Livers of MAT1A-KO mice were characterized by high levels of triglycerides, diglycerides, fatty acids, ceramides, and oxidized fatty acids, as well as low levels of SAMe and downstream metabolites. There was a correlation between liver and serum metabolomes. We identified a serum metabolomic signature associated with MAT1A-KO mice that also was present in 49% of the patients; based on this signature, we identified 2 NAFLD subtypes. We identified specific panels of markers that could distinguish patients with NASH from patients with simple steatosis for each subtype of NAFLD. Administration of SAMe reduced features of steatohepatitis in MAT1A-KO mice.

CONCLUSIONS

In an analysis of serum metabolomes of patients with NAFLD and MAT1A-KO mice with steatohepatitis, we identified 2 major subtypes of NAFLD and markers that differentiate steatosis from NASH in each subtype. These might be used to monitor disease progression and identify therapeutic targets for patients.

Bioinformatic Analysis of Coronary Disease Associated SNPs and Genes to Identify Proteins Potentially Involved in the Pathogenesis of Atherosclerosis

Factors that contribute to the onset of atherosclerosis may be elucidated by bioinformatic techniques applied to multiple sources of genomic and proteomic data. The results of genome wide association studies, such as the CardioGramPlusC4D study, expression data, such as that available from expression quantitative trait loci (eQTL) databases, along with protein interaction and pathway data available in Ingenuity Pathway Analysis (IPA), constitute a substantial set of data amenable to bioinformatics analysis. This study used bioinformatic analyses of recent genome wide association data to identify a seed set of genes likely associated with atherosclerosis. The set was expanded to include protein interaction candidates to create a network of proteins possibly influencing the onset and progression of atherosclerosis. Local average connectivity (LAC), eigenvector centrality, and betweenness metrics were calculated for the interaction network to identify top gene and protein candidates for a better understanding of the atherosclerotic disease process. The top ranking genes included some known to be involved with cardiovascular disease (APOA1, APOA5, APOB, APOC1, APOC2, APOE, CDKN1A, CXCL12, SCARB1, SMARCA4 and TERT), and others that are less obvious and require further investigation (TP53, MYC, PPARG, YWHAQ, RB1, AR, ESR1, EGFR, UBC and YWHAZ). Collectively these data help define a more focused set of genes that likely play a pivotal role in the pathogenesis of atherosclerosis and are therefore natural targets for novel therapeutic interventions.

Head injury serum markers for assessing response to trauma: Design of the HeadSMART study

BACKGROUND

Accurate diagnosis and risk stratification of traumatic brain injury (TBI) at time of presentation remains a clinical challenge. The Head Injury Serum Markers for Assessing Response to Trauma study (HeadSMART) aims to examine blood-based biomarkers for diagnosing and determining prognosis in TBI.

METHODS

HeadSMART is a 6-month prospective cohort study comparing emergency department patients evaluated for TBI (exposure group) to (1) emergency department patients evaluated for traumatic injury without head trauma and (2) healthy persons. Study methods and characteristics of the first 300 exposure participants are discussed.

RESULTS

Of the first 300 participants in the exposure arm, 70% met the American Congress of Rehabilitation Medicine criteria for TBI, with the majority (80.1%) classified as mild TBI. The majority of subjects in the exposure arm had Glasgow Coma Scale scores of 13-15 (98.0%), normal head computed tomography (81.3%) and no prior history of concussion (71.7%).

CONCLUSION

With systematic phenotyping, HeadSMART will facilitate diagnosis and risk-stratification of the heterogeneous group of individuals currently diagnosed with TBI.

Heterogeneous Stromal Signaling within the Tumor Microenvironment Controls the Metastasis of Pancreatic Cancer

Understanding how stromal signals regulate the development of pancreatic ductal adenocarcinoma (PDAC) may suggest novel therapeutic interventions in this disease. In this study, we assessed the metastatic role of stromal signals suggested to be important in the PDAC microenvironment. Src and IGF-1R phosphorylated the prometastatic molecule Annexin A2 (AnxA2) at Y23 and Y333 in response to stromal signals HGF and IGF-1, respectively, and IGF-1 expression was regulated by the Sonic Hedgehog (Shh) pathway. Both Shh and HGF were heterogeneously expressed in PDAC stroma, and only dual inhibition of these pathways could significantly suppress AnxA2 phosphorylation, PDAC growth, and metastasis. Taken together, our results illuminate tumor-stromal interactions, which drive metastasis, and provide a mechanism-based rationale for a stroma-directed therapy for PDAC. Cancer Res; 77(1); 41-52. ©2016 AACR.

Protein kinase A-dependent phosphorylation stimulates the transcriptional activity of hypoxia-inducible factor 1

Hypoxia-inducible factor 1 (HIF-1) activates the transcription of genes encoding proteins that enable cells to adapt to reduced O2 availability. Proteins encoded by HIF-1 target genes play a central role in mediating physiological processes that are dysregulated in cancer and heart disease. These diseases are also characterized by increased production of cyclic adenosine monophosphate (cAMP), the allosteric activator of cAMP-dependent protein kinase A (PKA). Using glutathione S-transferase pull-down, coimmunoprecipitation, and mass spectrometry analyses, we demonstrated that PKA interacts with HIF-1α in HeLa cervical carcinoma cells and rat cardiomyocytes. PKA phosphorylated Thr(63) and Ser(692) on HIF-1α in vitro and enhanced HIF transcriptional activity and target gene expression in HeLa cells and rat cardiomyocytes. PKA inhibited the proteasomal degradation of HIF-1α in an O2-independent manner that required the phosphorylation of Thr(63) and Ser(692) and was not affected by prolyl hydroxylation. PKA also stimulated the binding of the coactivator p300 to HIF-1α to enhance its transcriptional activity and counteracted the inhibitory effect of asparaginyl hydroxylation on the association of p300 with HIF-1α. Furthermore, increased cAMP concentrations enhanced the expression of HIF target genes encoding CD39 and CD73, which are enzymes that convert extracellular adenosine 5'-triphosphate to adenosine, a molecule that enhances tumor immunosuppression and reduces heart rate and contractility. These data link stimuli that promote cAMP signaling, HIF-1α-dependent changes in gene expression, and increased adenosine, all of which contribute to the pathophysiology of cancer and heart disease.

Local Joint inflammation and histone citrullination in a murine model of the transition from preclinical autoimmunity to inflammatory arthritis

OBJECTIVE

Anti-citrullinated protein antibodies (ACPAs) are characteristic of rheumatoid arthritis (RA). However, their presence years before the onset of clinical RA is perplexing. Although multiple putative citrullinated antigens have been identified, no studies have demonstrated the specific capacity of these antigens to initiate inflammatory arthritis. This study was undertaken to recapitulate the transition from preclinical to clinical RA and to demonstrate the capacity of local citrullination to facilitate this transition.

METHODS

We performed proteomic analysis of activated human neutrophils to identify citrullinated proteins, including those targeted as part of the RA immune response. Using enzyme-linked immunosorbent assay, we compared RA and osteoarthritis synovial fluid for levels of citrullinated histone H2B and its immune complex. Using macrophage activation assays, we assessed the effect of histone citrullination on immunostimulatory capacity and evaluated the stimulatory capacity of native and citrullinated H2B immune complexes. Finally, we assessed the potential for anti-citrullinated H2B antibodies to mediate arthritis in vivo.

RESULTS

We identified robust targeting of neutrophil-derived citrullinated histones by the ACPA immune response. More than 90% of the RA patients had anti-citrullinated H2B antibodies. Histone citrullination increased innate immunostimulatory capacity, and immune complexes containing citrullinated histones activated macrophage cytokine production and propagated neutrophil activation. Finally, we demonstrated that immunization with H2B was arthritogenic, but only in the setting of underlying articular inflammation.

CONCLUSION

Our findings indicate that citrullinated histones, specifically citrullinated H2B, are an antigenic target of the ACPA immune response. Furthermore, local generation of citrullinated antigen during low-grade articular inflammation provides a mechanistic model for the conversion from preclinical autoimmunity to inflammatory arthritis.

Harnessing the Power of Integrated Mitochondrial Biology and Physiology: A Special Report on the NHLBI Mitochondria in Heart Diseases Initiative

Mitochondrial biology is the sum of diverse phenomena from molecular profiles to physiological functions. A mechanistic understanding of mitochondria in disease development, and hence the future prospect of clinical translations, relies on a systems-level integration of expertise from multiple fields of investigation. Upon the successful conclusion of a recent National Institutes of Health, National Heart, Lung, and Blood Institute initiative on integrative mitochondrial biology in cardiovascular diseases, we reflect on the accomplishments made possible by this unique interdisciplinary collaboration effort and exciting new fronts on the study of these remarkable organelles.

Circulating Brain-Derived Neurotrophic Factor Has Diagnostic and Prognostic Value in Traumatic Brain Injury

Brain-derived neurotrophic factor (BDNF) is important for neuronal survival and regeneration. We investigated the diagnostic and prognostic values of serum BDNF in traumatic brain injury (TBI). We examined serum BDNF in two independent cohorts of TBI cases presenting to the emergency departments (EDs) of the Johns Hopkins Hospital (JHH; n = 76) and San Francisco General Hospital (SFGH, n = 80), and a control group of JHH ED patients without TBI (n = 150). Findings were subsequently validated in the prospective, multi-center Transforming Research and Clinical Knowledge in TBI (TRACK-TBI) Pilot study (n = 159). We investigated the association between BDNF, glial fibrillary acidic protein (GFAP), and ubiquitin C-terminal hydrolase-L1 (UCH-L1) and recovery from TBI at 6 months in the TRACK-TBI Pilot cohort. Incomplete recovery was defined as having either post-concussive syndrome or a Glasgow Outcome Scale Extended score <8 at 6 months. Median day-of-injury BDNF concentrations (ng/mL) were lower among TBI cases (JHH TBI, 17.5 and SFGH TBI, 13.8) than in JHH controls (60.3; p = 0.0001). Among TRACK-TBI Pilot subjects, median BDNF concentrations (ng/mL) were higher in mild (8.3) than in moderate (4.3) or severe TBI (4.0; p = 0.004. In the TRACK-TBI cohort, the 75 (71.4%) subjects with very low BDNF values (i.e., <the 1st percentile for non-TBI controls, <14.2 ng/mL) had higher odds of incomplete recovery than those who did not have very low values (odds ratio, 4.0; 95% confidence interval [CI]: 1.5-11.0). The area under the receiver operator curve for discriminating complete and incomplete recovery was 0.65 (95% CI: 0.52-0.78) for BDNF, 0.61 (95% CI: 0.49-0.73) for GFAP, and 0.55 (95% CI: 0.43-0.66) for UCH-L1. The addition of GFAP/UCH-L1 to BDNF did not improve outcome prediction significantly. Day-of-injury serum BDNF is associated with TBI diagnosis and also provides 6-month prognostic information regarding recovery from TBI. Thus, day-of-injury BDNF values may aid in TBI risk stratification.

Transformative Impact of Proteomics on Cardiovascular Health and Disease: A Scientific Statement From the American Heart Association

The year 2014 marked the 20th anniversary of the coining of the term proteomics. The purpose of this scientific statement is to summarize advances over this period that have catalyzed our capacity to address the experimental, translational, and clinical implications of proteomics as applied to cardiovascular health and disease and to evaluate the current status of the field. Key successes that have energized the field are delineated; opportunities for proteomics to drive basic science research, facilitate clinical translation, and establish diagnostic and therapeutic healthcare algorithms are discussed; and challenges that remain to be solved before proteomic technologies can be readily translated from scientific discoveries to meaningful advances in cardiovascular care are addressed. Proteomics is the result of disruptive technologies, namely, mass spectrometry and database searching, which drove protein analysis from 1 protein at a time to protein mixture analyses that enable large-scale analysis of proteins and facilitate paradigm shifts in biological concepts that address important clinical questions. Over the past 20 years, the field of proteomics has matured, yet it is still developing rapidly. The scope of this statement will extend beyond the reaches of a typical review article and offer guidance on the use of next-generation proteomics for future scientific discovery in the basic research laboratory and clinical settings.