flow-cytometry-based-quantification-and-analysis-of-myocardial-b-cells

Flow Cytometry-Based Quantification and Analysis of Myocardial B-Cells

A growing body of evidence shows that B-lymphocytes play an important role in the context of myocardial physiology and myocardial adaptation to injury. ...

The Johns Hopkins University School of Medicine

In patients with non-ischaemic cardiomyopathy and reduced left ventricular ejection fraction (LVEF), normalisation of LVEF is associated with improved outcomes. However, data on patients with ischaemic cardiomyopathy and recovered LVEF are lacking. The goal of this study was to assess the prognostic significance of normalisation of the LVEF in patients with ischaemic cardiomyopathy.

Association of early versus delayed normalisation of left ventricular ejection fraction with mortality in ischemic cardiomyopathy.

The uninjured murine heart contains a heterogeneous population of macrophages with disparate ontogenies and functions. These macrophages are often associated with blood vessels and can be subclassified based on the expression of CC chemokine receptor 2 (CCR2) and major histocompatibility complex class II (MHC-II). The biological cues that modulate these macrophage pool subpopulations have not been completely identified. It has been recently shown that a sub-population of circulating naïve B cells adheres to the myocardial microvasculature. We hypothesized that B cells might modulate the phenotype of myocardial macrophages. To test this hypothesis, we analyzed both the relative location of B cells and macrophages in myocardial histological section and the prevalence of myocardial macrophage subsets in hearts from B cell-deficient mice (μMT) and mice depleted of B cells through administration of an anti-CD20 antibody. We found that B cells pause in the microvasculature in proximity of macrophages and modulate the number of myocardial CCR2MHC-II cells. Through in vitro studies we found that this is likely the result of a paracrine effect of B cells on the expression of MHC-II in CCR2 cells. These results reveal an unexpected relationship between B cells and resident macrophages and, highlighting a direct intramyocardial effect of circulating B cells, challenge the currently held belief that naïve recirculating B lymphocytes merely shuttle between lymphoid stations.

B cells modulate the expression of MHC-II on cardiac CCR2 macrophages.

Patients with non-ischaemic dilated cardiomyopathy (NICM) may experience a normalisation in left ventricular ejection fraction (LVEF). Although this correlates with improved prognosis, it does not correspond to a normalisation in the risk of death during follow-up. Currently, there are no tools to risk stratify this population. We tested the hypothesis that absolute global longitudinal strain (aGLS) is associated with mortality in patients with NICM and recovered ejection fraction (LVEF).

Prognostic significance of longitudinal strain in dilated cardiomyopathy with recovered ejection fraction.

Practice guidelines suggest the use of implantable cardioverter-defibrillators in patients with left ventricular ejection fractions (LVEF) ≤ 35% despite 3 to 6 months of guideline-directed medical therapy (GDMT). It remains unclear whether this strategy is appropriate for patients with dilated cardiomyopathy (DCM), who can experience reverse ventricular remodeling for up to 24 months after the initiation of GDMT. The aim of this study was to assess the longitudinal dynamic relationship between LVEF ≤ 35% and arrhythmic risk in patients with recent-onset nonischemic DCM on GDMT.

Longitudinal Arrhythmic Risk Assessment Based on Ejection Fraction in Patients with Recent-Onset Nonischemic Dilated Cardiomyopathy.

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

Article	Year
Association of early versus delayed normalisation of left ventricular ejection fraction with mortality in ischemic cardiomyopathy. Open heart\| PubMed ID: 33723015	2021
B cells modulate the expression of MHC-II on cardiac CCR2 macrophages. Journal of molecular and cellular cardiology\| PubMed ID: 33971183	2021
Prognostic significance of longitudinal strain in dilated cardiomyopathy with recovered ejection fraction. Heart (British Cardiac Society)\| PubMed ID: 34493546	2022
Longitudinal Arrhythmic Risk Assessment Based on Ejection Fraction in Patients with Recent-Onset Nonischemic Dilated Cardiomyopathy. Journal of the American Society of Echocardiography : official publication of the American Society of Echocardiography\| PubMed ID: 35367610	2022
The Role of B Cells in Cardiomyopathy and Heart Failure. Current cardiology reports\| PubMed ID: 35689723	2022

Luigi Adamo

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