Single-Cell Sequencing of Mouse Heart Immune Infiltrate in Pressure Overload–Driven Heart Failure Reveals Extent of Immune Activation

Abstract

Background: Inflammation is a key component of cardiac disease, with macrophages and T lymphocytes mediating essential roles in the progression to heart failure. Nonetheless, little insight exists on other immune subsets involved in the cardiotoxic response. Methods: Here, we used single-cell RNA sequencing to map the cardiac immune composition in the standard murine nonischemic, pressure-overload heart failure model. By focusing our analysis on CD45 + cells, we obtained a higher resolution identification of the immune cell subsets in the heart, at early and late stages of disease and in controls. We then integrated our findings using multiparameter flow cytometry, immunohistochemistry, and tissue clarification immunofluorescence in mouse and human. Results: We found that most major immune cell subpopulations, including macrophages, B cells, T cells and regulatory T cells, dendritic cells, Natural Killer cells, neutrophils, and mast cells are present in both healthy and diseased hearts. Most cell subsets are found within the myocardium, whereas mast cells are found also in the epicardium. Upon induction of pressure overload, immune activation occurs across the entire range of immune cell types. Activation led to upregulation of key subset-specific molecules, such as oncostatin M in proinflammatory macrophages and PD-1 in regulatory T cells, that may help explain clinical findings such as the refractivity of patients with heart failure to anti–tumor necrosis factor therapy and cardiac toxicity during anti–PD-1 cancer immunotherapy, respectively. Conclusions: Despite the absence of infectious agents or an autoimmune trigger, induction of disease leads to immune activation that involves far more cell types than previously thought, including neutrophils, B cells, Natural Killer cells, and mast cells. This opens up the field of cardioimmunology to further investigation by using toolkits that have already been developed to study the aforementioned immune subsets. The subset-specific molecules that mediate their activation may thus become useful targets for the diagnostics or therapy of heart failure.

Adipokines and Inflammation: Focus on Cardiovascular Diseases

“…Several studies have demonstrated the implication of OSM in cardiovascular diseases; in fact, its receptor is expressed in cardiomyocytes, which supports these findings. This adipokine is expressed in cardiac tissue from patients undergoing valve surgery, tissues from patients with end-stage heart failure and in aortic samples showing inflammation, but not in healthy hearts [ 186 , 187 , 188 ].…”

Epigenetics of aging and disease: a brief overview

“…Finally, single-cell transcriptome analysis will be crucial to uncovering epigenomic changes within various cellular and sub-cellular populations to further shed light on the correlation of (epi)transcriptomic changes in aged and diseased tissue. Single-cell RNA sequencing of a murine cardiac pressure-overload HF model revealed that induction of HF leads to an intricate immune activation, whereby a myriad of cells, including neutrophils, B cells, NK cells and mast cells are activated [76]. Using this approach, and correlation of aberrant or acute immune responses with disease onset during aging can further shed light onto the underlying mechanisms of the failing heart.…”

Single-cell genomics to understand disease pathogenesis

“…We also performed molecular pathology analysis using cardiac biopsy samples from patients with heart failure before treatment to demonstrate that the level of DNA damage in cardiomyocytes determines clinical prognosis and treatment response [9]. Recent single-cell RNA-seq analysis in heart failure biology has also revealed the involvement of inflammatory cells [10] and the anatomical expression profiles of disease-causing genes [11,12].…”