Serum Proteomic Analysis of Peripartum Cardiomyopathy Reveals Distinctive Dysregulation of Inflammatory and Cholesterol Metabolism Pathways

BACKGROUND

The pathophysiology of peripartum cardiomyopathy (PPCM) and its distinctive biological features remain incompletely understood. High-throughput serum proteomic profiling, a powerful tool to gain insights into the pathophysiology of diseases at a systems biology level, has never been used to investigate PPCM relative to nonischemic cardiomyopathy.

OBJECTIVES

The aim of this study was to characterize the pathophysiology of PPCM through serum proteomic analysis.

METHODS

Aptamer-based proteomic analysis (SomaScan 7K) was performed on serum samples from women with PPCM (n = 67), women with nonischemic nonperipartum cardiomyopathy (NPCM) (n = 31), and age-matched healthy peripartum and nonperipartum women (n = 10 each). Serum samples were obtained from the IPAC (Investigation of Pregnancy-Associated Cardiomyopathy) and IMAC2 (Intervention in Myocarditis and Acute Cardiomyopathy) studies.

RESULTS

Principal component analysis revealed unique clustering of each patient group (P for difference <0.001). Biological pathway analyses of differentially measured proteins in PPCM relative to NPCM, before and after normalization to pertinent healthy controls, highlighted specific dysregulation of inflammatory pathways in PPCM, including the upregulation of the cholesterol metabolism-related anti-inflammatory pathway liver-X receptor/retinoid-X receptor (LXR/RXR) (P < 0.01, Z-score 1.9-2.1). Cardiac recovery by 12 months in PPCM was associated with the downregulation of pro-inflammatory pathways and the upregulation of LXR/RXR, and an additional RXR-dependent pathway involved in the regulation of inflammation and metabolism, peroxisome proliferator-activated receptor α/RXRα signaling.

CONCLUSIONS

Serum proteomic profiling of PPCM relative to NPCM and healthy controls indicated that PPCM is a distinct disease entity characterized by the unique dysregulation of inflammation-related pathways and cholesterol metabolism-related anti-inflammatory pathways. These findings provide insight into the pathophysiology of PPCM and point to novel potential therapeutic targets.

Abstract P3085: The Human Myocardium Harbors A Population Of B Cells With A Distinctive Gene Expression Signature Conserved Across Species

Introduction: Investigations in murine models have identified myocardial B cells with a characteristic gene expression signature and have pointed at B cells as a promising target to develop novel therapies for heart failure. However, there is almost no data on B cells in the human heart.

Methods and Results: We performed immunostaining to characterize the amount and distribution of B cells in human hearts. In 12 healthy hearts collected at autopsy, we found 1.4 ± 1.6 CD20+ B cells per high power field. The number of CD3+ T cells was almost 20 times higher (26.8 ± 28.6, P<0.001). Utilizing CD31 (endothelial marker), we found that human myocardial B cells were both in intravascular and interstitial locations, with a slight prevalence for the interstitium (P=0.006). Parallel analysis of tissue collected post-mortem or at the time of VAD placement showed that analysis of post-mortem tissue did not introduce bias. To gain insight into the biology of human myocardial B cells we first analyzed publicly available single cell sequencing datasets of myocardial (Heart Cell Atlas) and peripheral blood cells (10X Genomics). We found that the human myocardium harbored a minor population of B1 cells and a larger population of B2 cells, and that myocardial B cells had a gene expression signature distinct from that of peripheral blood B cells. We validated these findings on primary B cells sorted from the heart and peripheral blood of 2 patients subjected to LVAD implant (binomial for concordance p=4.13e-32). To identify biological pathways upregulated in myocardial B cells across species, we compared differential gene expression in myocardial vs peripheral blood B cells across the studied human datasets and published rodent datasets. We identified 703 genes with consistent differential gene expression (binomial p=2.9e-48). KEGG pathway analysis of these genes highlighted “B cell receptor signaling pathway”, “Antigen processing and presentation” and “Cytokine-cytokine receptor interaction” among the top conserved pathways upregulated in cardiac B cells (FDR <0.001).

Conclusions: The human heart harbors a small population of B cells that is comprised of both B1 and B2 cells. Human myocardial B cells have a distinct gene expression signature that is conserved across species.

The Role of B Cells in Cardiomyopathy and Heart Failure

PURPOSE OF REVIEW

To summarize the current knowledge on the role that B lymphocytes play in heart failure.

RECENT FINDINGS

Several studies from murine models have shown that B cells modulate cardiac adaptation to injury and ultimately affect the degree of cardiac dysfunction after acute ischemic damage. In addition, a B cell-modulating small molecule was recently shown to have beneficial effects in humans with heart failure with preserved ejection fraction. B lymphocytes are specialized immune cells present in all jawed vertebrates. They are characteristically known for their ability to produce antibodies, but they have other functions and are important players in virtually all forms of immune responses. A growing body of evidence indicates that B cells are intimately connected with the heart and that B cell dysregulation might play a role in the pathogenesis and progression of both heart failure with reduced ejection fraction and heart failure with preserved ejection fraction. B cells are therefore gathering attention as potential targets for the development of novel immunomodulatory-based treatments for heart failure.