Immune Functions and Properties of Resident Cells in the Heart and Cardiovascular System: Pericytes

Revisiting Cardiac Biology in the Era of Single Cell and Spatial Omics

Throughout our lifetime, each beat of the heart requires the coordinated action of multiple cardiac cell types. Understanding cardiac cell biology, its intricate microenvironments, and the mechanisms that govern their function in health and disease are crucial to designing novel therapeutical and behavioral interventions. Recent advances in single-cell and spatial omics technologies have significantly propelled this understanding, offering novel insights into the cellular diversity and function and the complex interactions of cardiac tissue. This review provides a comprehensive overview of the cellular landscape of the heart, bridging the gap between suspension-based and emerging in situ approaches, focusing on the experimental and computational challenges, comparative analyses of mouse and human cardiac systems, and the rising contextualization of cardiac cells within their niches. As we explore the heart at this unprecedented resolution, integrating insights from both mouse and human studies will pave the way for novel diagnostic tools and therapeutic interventions, ultimately improving outcomes for patients with cardiovascular diseases.

Does new onset and pre-existing atrial fibrillation predict mortality in COVID-19 patients?

Background

Coronavirus Disease-2019 (COVID-19), caused by Severe Acute Respiratory Syndrome-Coronavirus-2, still remains prevalent and severe. We aimed to evaluate the effects of pre-existing atrial fibrillation and new-onset atrial fibrillation (NOAF) on the clinical severity and mortality of COVID-19.

Results

Between April and December 2020, 5577 patients with positive PCR and/or COVID-19 compatible findings in computed tomography hospitalized were enrolled retrospectively. Total and in-hospital mortality, need for intensive care unit (ICU), need for mechanical ventilation, and recurrent hospitalization results of 286 patients with pre-existing AF before hospitalization and 82 patients with NOAF during hospitalization were evaluated. Preexisting AF was associated with a 2-fold increase in total and in-hospital mortality [OR (2.16 (1.62–2.89), 2.02 (1.48–2.76), P < 0.001, respectively]. NOAF was associated with a 14-fold increase in total mortality and a 12-fold increase in in-hospital mortality [OR(14.72 (9.22–23.5), 12.56 (8.02–19.68), P < 0.001], respectively]. However, pre-existing AF and NOAF resulted in increased ICU admission, mechanical ventilation, and recurrent hospitalization. In the Cox regression analysis, NOAF was observed as an independent risk factor for mortality.

Conclusions

Pre-existing AF and in-hospital NOAF were associated with increased mortality and severity in hospitalized COVID-19 patients. In addition, NOAF was observed as an independent prognostic indicator in terms of total mortality.

Is Atrial Fibrillation a Risk Factor for Worse Outcomes in Severe COVID-19 Patients: A Single Center Retrospective Cohort

INTRODUCTION

New onset atrial fibrillation leads to worse outcomes in patients with sepsis. The association between new onset atrial fibrillation (AF) in COVID19 patients with COVID19 outcomes are lacking. This study aims to determine whether new onset atrial fibrillation in COVID19 patients admitted in the ICU is a risk factor for death or requirement of mechanical ventilation (MV).

METHODS

This is a retrospective study conducted in a cohort of COVID-19 patients admitted to Bahrain Defence Force COVID19 Field ICU between April 2020 to November 2020. Data were extracted from the electronic medical records. The patients who developed new onset AF during admission were compared to patients who remained in sinus rhythm. Multivariate logistic regression models were used to control for confounders and estimate the effect of AF on the outcomes of these patients.

RESULTS

Our study included a total of 492 patients out of which 30 were diagnosed with new onset AF. In the AF group, the primary outcome occurred in 66.7% of patients (n = 20). In the control group, 17.1% (n = 79) developed the primary outcome. Upon adjusting for the confounders in the multivariate regression model, AF had an odds ratio of 3.96 (95% CI: 1.05-14.98; p = 0.042) for the primary outcome.

CONCLUSION

Our results indicate that new onset AF is a risk factor for worse outcomes in patients admitted with COVID19 in the ICU.

Atrial fibrillation is an independent predictor for in-hospital mortality in patients admitted with SARS-CoV-2 infection

Background

Atrial fibrillation (AF) is the most encountered arrhythmia and has been associated with worse in-hospital outcomes.

Objective

This study was to determine the incidence of AF in patients hospitalized with coronavirus disease 2019 (COVID-19) as well as its impact on in-hospital mortality.

Methods

Patients hospitalized with a positive COVID-19 polymerase chain reaction test between March 1 and April 27, 2020, were identified from the common medical record system of 13 Northwell Health hospitals. Natural language processing search algorithms were used to identify and classify AF. Patients were classified as having AF or not. AF was further classified as new-onset AF vs history of AF.

Results

AF occurred in 1687 of 9564 patients (17.6%). Of those, 1109 patients (65.7%) had new-onset AF. Propensity score matching of 1238 pairs of patients with AF and without AF showed higher in-hospital mortality in the AF group (54.3% vs 37.2%; P < .0001). Within the AF group, propensity score matching of 500 pairs showed higher in-hospital mortality in patients with new-onset AF as compared with those with a history of AF (55.2% vs 46.8%; P = .009). The risk ratio of in-hospital mortality for new-onset AF in patients with sinus rhythm was 1.56 (95% confidence interval 1.42–1.71; P < .0001). The presence of cardiac disease was not associated with a higher risk of in-hospital mortality in patients with AF (P = .1).

Conclusion

In patients hospitalized with COVID-19, 17.6% experienced AF. AF, particularly new-onset, was an independent predictor of in-hospital mortality.

Role of angiotensin-converting enzyme 2 and pericytes in cardiac complications of COVID-19 infection

The prevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) quickly reached pandemic proportions, and knowledge about this virus and coronavirus disease 2019 (COVID-19) has expanded rapidly. This review focuses primarily on mechanisms that contribute to acute cardiac injury and dysfunction, which are common in patients with severe disease. The etiology of cardiac injury is multifactorial, and the extent is likely enhanced by preexisting cardiovascular disease. Disruption of homeostatic mechanisms secondary to pulmonary pathology ranks high on the list, and there is growing evidence that direct infection of cardiac cells can occur. Angiotensin-converting enzyme 2 (ACE2) plays a central role in COVID-19 and is a necessary receptor for viral entry into human cells. ACE2 normally not only eliminates angiotensin II (Ang II) by converting it to Ang-(1-7) but also elicits a beneficial response profile counteracting that of Ang II. Molecular analyses of single nuclei from human hearts have shown that ACE2 is most highly expressed by pericytes. Given the important roles that pericytes have in the microvasculature, infection of these cells could compromise myocardial supply to meet metabolic demand. Furthermore, ACE2 activity is crucial for opposing adverse effects of locally generated Ang II, so virus-mediated internalization of ACE2 could exacerbate pathology by this mechanism. While the role of cardiac pericytes in acute heart injury by SARS-CoV-2 requires investigation, expression of ACE2 by these cells has broader implications for cardiac pathophysiology.

Role of angiotensin-converting enzyme 2 and pericytes in cardiac complications of COVID-19 infection

The prevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) quickly reached pandemic proportions, and knowledge about this virus and coronavirus disease 2019 (COVID-19) has expanded rapidly. This review focuses primarily on mechanisms that contribute to acute cardiac injury and dysfunction, which are common in patients with severe disease. The etiology of cardiac injury is multifactorial, and the extent is likely enhanced by preexisting cardiovascular disease. Disruption of homeostatic mechanisms secondary to pulmonary pathology ranks high on the list, and there is growing evidence that direct infection of cardiac cells can occur. Angiotensin-converting enzyme 2 (ACE2) plays a central role in COVID-19 and is a necessary receptor for viral entry into human cells. ACE2 normally not only eliminates angiotensin II (Ang II) by converting it to Ang-(1–7) but also elicits a beneficial response profile counteracting that of Ang II. Molecular analyses of single nuclei from human hearts have shown that ACE2 is most highly expressed by pericytes. Given the important roles that pericytes have in the microvasculature, infection of these cells could compromise myocardial supply to meet metabolic demand. Furthermore, ACE2 activity is crucial for opposing adverse effects of locally generated Ang II, so virus-mediated internalization of ACE2 could exacerbate pathology by this mechanism. While the role of cardiac pericytes in acute heart injury by SARS-CoV-2 requires investigation, expression of ACE2 by these cells has broader implications for cardiac pathophysiology.

Mesenchymal stem cell mediates cardiac repair through autocrine, paracrine and endocrine axes

In the past decade, despite key advances in therapeutic strategies following myocardial infarction, none can directly address the loss of cardiomyocytes following ischemic injury. Cardiac cell-based therapy is at the cornerstone of regenerative medicine that has shown potential for tissue repair. Mesenchymal stem cells (MSC) represent a strong candidate to heal the infarcted myocardium. While differentiation potential has been described as a possible avenue for MSC-based repair, their secreted mediators are responsible for the majority of the ascribed prohealing effects. MSC can either promote their own survival and proliferation through autocrine effect or secrete trophic factors that will act on adjacent cells through a paracrine effect. Prior studies have also documented beneficial effects even when MSCs were remotely delivered, much akin to an endocrine mechanism. This review aims to distinguish the paracrine activity of MSCs from an endocrine-like effect, where remotely transplanted cells can promote healing of the injured myocardium.

Atrial fibrillation in COVID-19: A review of possible mechanisms

A relationship between COVID-19 infection and an increasing incidence of atrial fibrillation has been observed. However, the underlying pathophysiology as a precipitant to AF has not been reviewed. This paper will consider the possible pathological and immunological AF mechanisms as a result, of COVID-19 infection. We discuss the role myocardial microvascular pericytes expressing the ACE-2 receptor and their potential for an organ-specific cardiac involvement with COVID-19. Dysfunctional microvascular support by pericytes or endothelial cells may increase the propensity for AF via increased myocardial inflammation, fibrosis, increased tissue edema, and interstitial hydrostatic pressure. All of these factors can lead to electrical perturbances at the tissue and cellular level. We also consider the contribution of Angiotensin, pulmonary hypertension, and regulatory T cells as additional contributors to AF during COVID-19 infection. Finally, reference is given to two common drugs, corticosteroids and metformin, in COVID-19 and how they might influence AF incidence.

Human pluripotent stem cell-derived cardiac stromal cells and their applications in regenerative medicine

Coronary heart disease is one of the leading causes of death in the United States. Recent advances in stem cell biology have led to the development and engineering of human pluripotent stem cell (hPSC)-derived cardiac cells and tissues for application in cellular therapy and cardiotoxicity studies. Initial studies in this area have largely focused on improving differentiation efficiency and maturation states of cardiomyocytes. However, other cell types in the heart, including endothelial and stromal cells, play crucial roles in cardiac development, injury response, and cardiomyocyte function. This review discusses recent advances in differentiation of hPSCs to cardiac stromal cells, identification and classification of cardiac stromal cell types, and application of hPSC-derived cardiac stromal cells and tissues containing these cells in regenerative and drug development applications.

Pericytes in Cerebrovascular Diseases: An Emerging Therapeutic Target

Pericytes are functional components of the neurovascular unit (NVU) that are located around the blood vessels, and their roles in the regulation of cerebral health and diseases has been reported. Currently, the potential properties of pericytes as emerging therapeutic targets for cerebrovascular diseases have attracted considerable attention. Nonetheless, few reviews have comprehensively discussed pericytes and their roles in cerebrovascular diseases. Therefore, in this review, we not only summarized and described the basic characteristics of pericytes but also focused on clarifying the new understanding about the roles of pericytes in the pathogenesis of cerebrovascular diseases, including white matter injury (WMI), hypoxic-ischemic brain damage, depression, neovascular insufficiency disease, and Alzheimer's disease (AD). Furthermore, we summarized the current therapeutic strategies targeting pericytes for cerebrovascular diseases. Collectively, this review is aimed at providing a comprehensive understanding of pericytes and new insights about the use of pericytes as novel therapeutic targets for cerebrovascular diseases.

Resident cells of the myocardium: more than spectators in cardiac injury, repair and regeneration

Multiple resident cell types contribute to maintaining the structure and physiological function of the heart over the life course. Cardiomyocyte proliferation supports scar free regeneration in the neonatal heart following injury, but a lower rate of proliferation in the adult necessitates replacement by a collagen scar to maintain ventricular integrity. In this short review we discuss recent studies that have identified novel roles for non-myocyte resident cells and the extracellular matrix in supporting repair, as well as cardiomyocyte and vascular regeneration, following myocardial infarction.