Pericardial fluid as a new material for clinical heart research

Thiol/Disulfide Homeostasis in Pericardial Fluid and Plasma of Patients Undergoing Coronary Artery Bypass Surgery

INTRODUCTION

On-pump coronary artery bypass grafting (CABG) method affect almost allbiochemicalreactions by disrupting the patient's redox homeostasis. Detection of systemic redox hemostasis in the patient is critical for the CABG method's success and the prognosis of the disease. In this study, thiol/disulfide parameters, which are indicators of redox homeostasis, and ischemia-modified albumin levels in the plasma and pericardial fluid of patients who underwent CABG were investigated.

METHODS

Sixty patients who underwent an on-pump CABG operation with the cardiopulmonary bypass method were included in this study. Blood samples were taken from the patients before and after cardiopulmonary bypass. Pericardia fluid samples were taken before cardiopulmonary bypass. Then, thiol/disulfide homeostasis, albumin, and ischemia-modified albumin levels in the pericardial fluid and the patients' plasma levels were compared.

RESULTS

Albumin and ischemia-modified albumin levels were significantly higher in the postoperative period compared to the preoperative one (P<0.001). Thiol/disulfide parameters were higher and statistically significant in preoperative than in postoperative examinations (P<0.001). A negative correlation was found between pericardial fluid ischemia-modified albumin and thiol-disulfide parameters (P<0.001).

CONCLUSION

Changes in thiol/disulfide homeostasis, albumin, and ischemia-modified albumin levels at different times during the on-pump CABG may be caused by foreign non-endothelial surfaces, filters, the reperfusion process, and pharmacological effects in the extracorporeal circulation. Thiol/disulfide homeostasis, albumin, and ischemia-modified albumin levels should be monitored during the on-pump CABG and should be intervened with appropriate therapeutic strategies. In this way, secondary pathologies can be avoided by preventing cellular damage and excessive inflammatory responses.

Exploring the role of pericardial miRNAs and exosomes in modulating cardiac fibrosis

The potential of the pericardial space as a therapeutic delivery tool for cardiac fibrosis and heart failure (HF) treatment has yet to be elucidated. Recently, miRNAs and exosomes have been discovered to be present in human pericardial fluid (PF). Novel studies have shown characteristic human PF miRNA compositions associated with cardiac diseases and higher miRNA expressions in PF compared to peripheral blood. Five key studies found differentially expressed miRNAs in HF, angina pectoris, aortic stenosis, ventricular tachycardia, and congenital heart diseases with either atrial fibrillation or sinus rhythm. As miRNA-based therapeutics for cardiac fibrosis and HF showed promising results in several in vivo studies for multiple miRNAs, we hypothesize a potential role of miRNA-based therapeutics delivered through the pericardial cavity. This is underlined by the favorable results of the first phase 1b clinical trial in this emerging field. Presenting the first human miRNA antisense drug trial, inhibition of miR-132 by intravenous administration of a novel antisense oligonucleotide, CDR132L, established efficacy in reducing miR-132 in plasma samples in a dose-dependent manner. We screened the literature, provided an overview of the miRNAs and exosomes present in PF, and drew a connection to those miRNAs previously elucidated in cardiac fibrosis and HF. Further, we speculate about clinical implications and potential delivery methods.

The protective role of GATA6+ pericardial macrophages in pericardial inflammation

Prior research has suggested that GATA6+ pericardial macrophages may traffic to the myocardium to prevent interstitial fibrosis after myocardial infarction (MI), while subsequent literature claims that they do not. We demonstrate that GATA6+ pericardial macrophages are critical for preventing IL-33 induced pericarditis and attenuate trafficking of inflammatory monocytes and granulocytes to the pericardial cavity after MI. However, absence of GATA6+ macrophages did not affect myocardial inflammation due to MI or coxsackievirus-B3 induced myocarditis, or late-stage cardiac fibrosis and cardiac function post MI. GATA6+ macrophages are significantly less transcriptionally active following stimulation in vitro compared to bone marrow-derived macrophages and do not induce upregulation of inflammatory markers in fibroblasts. This suggests that GATA6+ pericardial macrophages attenuate inflammation through their interactions with surrounding cells. We therefore conclude that GATA6+ pericardial macrophages are critical in modulating pericardial inflammation, but do not play a significant role in controlling myocardial inflammation or fibrosis.

Pericardial fluid troponin in cardiac surgery

BACKGROUND AND OBJECTIVE

Pericardial Fluid (PF) is a rich reservoir of biologically active factors. Due to its proximity to the heart, the biochemical structure of PF may reflect the pathological changes in the cardiac interstitial environment. This manuscript aimed to determine whether the PF level of cardiac troponins changes in patients undergoing cardiac surgery.

METHODS

This scoping review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Medline, EMBASE, Cochrane, ClinicalTrials.gov, and Google Scholar databases were electronically searched for primary studies using the keywords "pericardial fluid," "troponin," and "cardiac surgery." The primary outcome of interest was changes in troponin levels within the PF preoperatively and postoperatively. Secondary outcomes of interest included comparisons between troponin level changes in the PF compared to plasma.

RESULTS

A total of 2901 manuscripts were screened through a title and abstract stage by two independent blinded reviewers. Of those, 2894 studies were excluded, and the remaining seven studies underwent a full-text review. Studies were excluded if they did not provide data or failed to meet inclusion criteria. Ultimately, six articles were included that discussed cardiac troponin levels within the PF in patients who had undergone cardiac surgery. Pericardial troponin concentration increased over time after surgery, and levels were significantly higher in PF compared to serum. All studies found that the type of operation did not affect these overall observations.

CONCLUSION

Our review of the literature suggest that the PF level of cardiac troponins increases in patients undergoing cardiac surgery, irrespective of the procedure type. However, these changes' exact pattern and clinical significance remain undefined.

Heart transplantation and biomarkers: a review about their usefulness in clinical practice

Advanced heart failure (AdvHF) can only be treated definitively by heart transplantation (HTx), yet problems such right ventricle dysfunction (RVD), rejection, cardiac allograft vasculopathy (CAV), and primary graft dysfunction (PGD) are linked to a poor prognosis. As a result, numerous biomarkers have been investigated in an effort to identify and prevent certain diseases sooner. We looked at both established biomarkers, such as NT-proBNP, hs-troponins, and pro-inflammatory cytokines, and newer ones, such as extracellular vesicles (EVs), donor specific antibodies (DSA), gene expression profile (GEP), donor-derived cell free DNA (dd-cfDNA), microRNA (miRNA), and soluble suppression of tumorigenicity 2 (sST2). These biomarkers are typically linked to complications from HTX. We also highlight the relationships between each biomarker and one or more problems, as well as their applicability in routine clinical practice.

Accumulation of Inflammatory Mediators in the Normal Pericardial Fluid

There is paucity of studies that focus on the composition of pericardial fluid under resting conditions. The purpose of this study is to determine the levels of inflammatory mediators in pericardial fluid and their correlation with plasma levels in patients undergoing elective cardiac surgery. We conducted a prospective cohort study on candidates for elective aortic valve replacement surgery. Pericardial fluid and peripheral venous blood samples were collected after opening the pericardium. Levels of interleukin 1α (IL-1α); interleukin 1β (IL-1β); interleukin 2 (IL-2) interleukin 4 (IL-4); interleukin 6 (IL-6); interleukin 8 (IL8); interleukin 10 (IL10); tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), vascular endothelial growth factor (VEGF), monocyte chemotactic protein-1 (MCP-1) epidermal growth factor (EGF), soluble E-selectin, L-selectin, P-selectin, intercellular adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecule-1 (VCAM-1) were determined in both pericardial fluid and serum samples. A total of 45 patients with a mean age of 74 years were included of which 66% were males. Serum levels of all study mediators were within normal limits. Serum and pericardial levels of IL-1 α, IL-1 β, IL-2, IL-4, and IL-10 were similar. Levels of VEGF, EGF, VCAM-2, ICAM 1, E-selectin, P-selectin, and L-selectin were significantly lower in pericardial fluid than in serum. However, levels of IL-6, IL-8, TNF-α, IFN-γ, MCP-1, and MCP-1 were significantly higher in the pericardial fluid than in serum. Under normal conditions, the pattern of distribution of different inflammatory mediators in the pericardial fluid does not reflect serum levels. This may either reflect the condition of the underlying myocardium and epicardial fat or the activity of the mesothelial and mononuclear cells present in pericardial fluid.

Feasibility study of intraoperative pericardial fluid biomarkers and length of stay after cardiac surgery

Objective

Pericardial fluid biomarkers reflect the physiologic state of the myocardium. Previously, we showed a sustained increase in pericardial fluid biomarkers compared with blood in the 48 hours after cardiac surgery. We assess the feasibility of analyzing 9 common cardiac biomarkers from pericardial fluid collected during cardiac surgery and test a preliminary hypothesis of association between the most common biomarkers, troponin and brain natriuretic peptide, and length of stay after surgery.

Methods

We prospectively enrolled 30 patients aged 18 years or more undergoing coronary artery or valvular surgery. Patients with ventricular assist devices, atrial fibrillation surgery, thoracic aorta surgery, redo surgery, concomitant noncardiac surgery, and preoperative inotropic support were excluded. Before pericardial excision during surgery, a 1-cm pericardial incision was made to insert an 18-gauge catheter and collect 10 mL of pericardial fluid. Concentrations of 9 established biomarkers of cardiac injury or inflammation including brain natriuretic peptide and troponin were measured. Zero truncated Poisson regression adjusted for Society of Thoracic Surgery Preoperative Risk of Mortality tested for a preliminary association between pericardial fluid biomarkers and length of stay.

Results

Pericardial fluid was collected and pericardial fluid biomarkers resulted for all patients. Adjusted for Society of Thoracic Surgery risk, brain natriuretic peptide, and troponin were associated with increased intensive care unit and overall hospital length of stay.

Conclusions

In 30 patients, pericardial fluid was obtained and analyzed for cardiac biomarkers. Adjusting for Society of Thoracic Surgery risk, pericardial fluid troponin and brain natriuretic peptide were preliminarily associated with increased length of stay. Further investigation is needed to validate this finding and to investigate the potential clinical utility of pericardial fluid biomarkers.

Myeloperoxidase Levels in Pericardial Fluid Is Independently Associated with Postoperative Atrial Fibrillation after Isolated Coronary Artery Bypass Surgery

BACKGROUND

Postoperative atrial fibrillation (POAF) is the most common complication after surgery for atherosclerotic cardiovascular disease (ASCVD) and leads to extended hospital stays and increased mortality. Myeloperoxidase (MPO) in postoperative pericardial drainage fluid is associated with an increased risk of POAF; however, the correlations between MPO in intraoperative pericardial fluid and POAF remain largely unknown. The aim of the study was to evaluate whether MPO is associated with POAF.

METHODS

A total of 97 patients with no history of atrial arrhythmia who had undergone coronary artery bypass surgery (CABG) were identified. We prospectively measured the levels of MPO in intraoperative pericardial fluid and blood using the human magnetic Luminex assay. Then, the occurrence of atrial fibrillation was continuously observed by postoperative ECG and telemetry strips until discharge.

RESULTS

Our data showed that POAF occurred in 24 of 97 patients (24.74%). MPO levels in blood were higher in the POAF group than the SR group (p = 0.064). Patients with POAF had significantly higher intraoperative pericardial fluid MPO levels than patients who remained in SR (p = 0.021). There was no significant correlation between pericardial fluid MPO levels and blood MPO levels (r = -0.47, p = 0.770). In a multivariable logistic regression model, pericardial fluid MPO levels were significantly associated with a higher risk of POAF (odds ratio = 1.016, 95% confidence interval, 1.001-1.031; p = 0.031).

CONCLUSIONS

Higher intraoperative pericardial fluid MPO levels are linked with POAF in patients undergoing CABG. This finding provides insight into a possible mechanism of MPO in pericardial fluid increase susceptibility to developing POAF in patients undergoing CABG.

Pericardial fluid and vascular tissue engineering: A preliminary study

BACKGROUND

The heart is surrounded by a membrane called pericardium or pericardial cavity.

OBJECTIVE

In this study, we investigated the pericardial fluid (PF) for coating polycaprolactone (PCL) scaffolds. PFS, which is a PF component, was used for the coating material. In addition to using PFS for surface coating, MED and fetal bovine serum (FBS) were also used for comparison.

METHODS

Pericardial fluid cells (PFSc) isolated from PF were cultured on coated PCL scaffolds for 1, 3, and 5 days. Cell viability was determined using 3-(4, 5-di-methylthiazol- 2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay.

RESULTS

The MTT assay results showed that the viability of cells on PCL scaffold coated with PFS increased over time (P < 0.005), and cell viability was significantly different between PCL scaffolds coated with PFS and non-coated PCL scaffolds. However, cell viability was significantly higher in the PCL scaffolds coated with PFS than non-coated and coated with FBS, MED, and PCL scaffolds. Scanning electron microscopy (SEM) microscopy images and MTT assay indicated that PFSc are attached, proliferated, and spread on PCL scaffolds, especially on PCL scaffolds coated with PFS.

CONCLUSIONS

These results suggest that PFS is a biocompatible material for surface modification of PCL scaffolds, which can be used as a suitable material for tissue engineering applications.

An overview of human pericardial space and pericardial fluid

The pericardium is a double-layered fibro-serous sac that envelops the majority of the surface of the heart as well as the great vessels. Pericardial fluid is also contained within the pericardial space. Together, the pericardium and pericardial fluid contribute to a homeostatic environment that facilitates normal cardiac function. Different diseases and procedural interventions may disrupt this homeostatic space causing an imbalance in the composition of immune mediators or by mechanical stress. Inflammatory cells, cytokines, and chemokines are present in the pericardial space. How these specific mediators contribute to different diseases is the subject of debate and research. With the advent of highly specialized assays that can identify and quantify various mediators we can potentially establish specific and sensitive biomarkers that can be used to differentiate pathologies, and aid clinicians in improving clinical outcomes for patients.

Isolation and Multiple Differentiation of Rat Pericardial Fluid Cells

Objective

The aim of the present study is to isolate and analyze the characterization of pericardial fluid cells (PFCs) from rat and provides a morphological basis for the basic research and clinical application of PFCs.

Methods

After aseptic thoracotomy was performed, normal saline was injected into the pericardial cavity of 50 adult Sprague–Dawley rats. The mixture of diluted pericardial fluid was extracted, centrifuged, and cultured. The cell morphology of different generations in the pericardial fluid was observed on an inverted microscope. The expression levels of CD44, CD29, CD90, and pan-hematopoietic marker CD45 were analyzed via flow cytometry. The third-generation cells were used for osteogenic, adipogenic, and cardiac differentiation.

Results

PFCs were successfully isolated and subcultured. PFCs were predominantly circular in shape after 24 h of culture. Following subculture for 3 days, the cells demonstrated a spindle shape. The rat pericardial fluid contains cell populations with uniform morphology, good growth state, and strong proliferation ability. Flow cytometry results showed that CD29 (100%) and CD90 (99.3%) were positively expressed, whereas CD45 (0.30%) and CD44 (0.48%) were negatively expressed. The PFCs could differentiate into osteoblasts and adipocytes after being induced. Cardiac differentiation was also confirmed by cardiac troponin T (cTnT) and α-sarcomeric actin (α-SA) staining.

Conclusion

This study revealed that a subpopulation of cells was isolated from pericardial fluid, which exhibited progenitor cell features and multiple differentiation potency. PFCs could serve as an alternative cell source for myocardial tissue repair, engineering, and reconstruction.

Therapeutic angiogenesis with exosomal microRNAs: an effectual approach for the treatment of myocardial ischemia

Therapeutic angiogenesis presents a potential approach for treating ischemic heart diseases especially in patients who are not appropriate candidates for traditional approaches of revascularization. This approach acts through inducing the neovascularization or maturation of pre-existing collateral vessels into functional arteries to bypass the blocked arteries and restore perfusion to ischemic myocardium. Successful stimulation of local angiogenesis can be established by the cross talk between stem cells, endothelial cells, and cardiomyocytes, which is mainly mediated by paracrine communication accompanied by secreted exosomes. Exosomes are extracellular vesicles carrying a complex of signaling molecules, such as microRNAs (miRs) that can modulate the function of recipient cells. Such particles have been indicated to exert cardioprotective role through providing signaling cues for angiogenesis, an effect ascribed mainly to their miRs content. Exosomal miRs-mediated therapeutic angiogenesis has been under drastic preclinical and clinical studies. In the current review, it was aimed to summarize pro-angiogenic exosomal miRs released by various cell types mediating angiogenesis, including stem cells, endothelial cells, and cardiomyocytes, which appear to exert a therapeutic effect on the myocardial ischemia. In brief, secreted exosomal miRs including miR-210, miR-23a-3p, miR-424, let-7f, miR-30b, miR-30c, miR-126, miR-21, miR-132, miR-130a-3p, miR-214, miR-378, miR-126, miR-133, and let-7b-5p could protect against myocardial ischemia through inducing cardiac angiogenesis and vascular regeneration resulting in the increase blood flow to ischemic myocardium.

Technologies for intrapericardial delivery of therapeutics and cells

The pericardium, which surrounds the heart, provides a unique enclosed volume and a site for the delivery of agents to the heart and coronary arteries. While strategies for targeting the delivery of therapeutics to the heart are lacking, various technologies and nanodelivery approaches are emerging as promising methods for site specific delivery to increase therapeutic myocardial retention, efficacy, and bioactivity, while decreasing undesired systemic effects. Here, we provide a literature review of various approaches for intrapericardial delivery of agents. Emphasis is given to sustained delivery approaches (pumps and catheters) and localized release (patches, drug eluting stents, and support devices and meshes). Further, minimally invasive access techniques, pericardial access devices, pericardial washout and fluid analysis, as well as therapeutic and cell delivery vehicles are presented. Finally, several promising new therapeutic targets to treat heart diseases are highlighted.

Pericardial Parietal Mesothelial Cells: Source of the Angiotensin-Converting-Enzyme of the Bovine Pericardial Fluid

Background

Angiotensin II (Ang II), the primary effector hormone of the renin-angiotensin system (RAS), acts systemically or locally, being produced by the action of angiotensin-converting-enzyme (ACE) on angiotensin I. Although several tissue RASs, such as cardiac RAS, have been described, little is known about the presence of an RAS in the pericardial fluid and its possible sources. Locally produced Ang II has paracrine and autocrine effects, inducing left ventricular hypertrophy, fibrosis, heart failure and cardiac dysfunction. Because of the difficulties inherent in human pericardial fluid collection, appropriate experimental models are useful to obtain data regarding the characteristics of the pericardial fluid and surrounding tissues.

Objectives

To evidence the presence of constituents of the Ang II production paths in bovine pericardial fluid and parietal pericardium.

Methods

Albumin-free crude extracts of bovine pericardial fluid, immunoprecipitated with anti-ACE antibody, were submitted to electrophoresis (SDS-PAGE) and gels stained with coomassie blue. Duplicates of gels were probed with anti-ACE antibody. In the pericardial membranes, ACE was detected by use of immunofluorescence.

Results

Immunodetection on nitrocellulose membranes showed a 146-KDa ACE isoform in the bovine pericardial fluid. On the pericardial membrane sections, ACE was immunolocalized in the mesothelial layer.

Conclusions

The ACE isoform in the bovine pericardial fluid and parietal pericardium should account at least partially for the production of Ang II in the pericardial space, and should be considered when assessing the cardiac RAS.

A fractionation approach applying chelating magnetic nanoparticles to characterize pericardial fluid's proteome

Owing to their close proximity, pericardial fluid (PF)'s proteome may mirror the pathophysiological status of the heart. Despite this diagnosis potential, the knowledge of PF's proteome is scarce. Large amounts of albumin hamper the characterization of the least abundant proteins in PF. Aiming to expand PF's proteome and to validate the technique for future applications, we have fractionated and characterized the PF, using N-(trimethoxysilylpropyl)ethylenediamine triacetic acid (EDTA)-functionalized magnetic nanoparticles (NPs@EDTA) followed by a GeLC-MS/MS approach. Similarly to an albumin-depletion kit, NPs@EDTA-based fractionation was efficient in removing albumin. Both methods displayed comparable inter-individual variability, but NPs@EDTA outperformed the former with regard to the protein dynamic range as well as to the monitoring of biological processes. Overall, 565 proteins were identified, of which 297 (>50%) have never been assigned to PF. Moreover, owing to this method's good proteome reproducibility, affordability, rapid automation and high binding ability of NP@EDTA, it bears a great potential towards future clinical application.

Adipokine Imbalance in the Pericardial Cavity of Cardiac and Vascular Disease Patients

Aim

Obesity and especially hypertrophy of epicardial adipose tissue accelerate coronary atherogenesis. We aimed at comparing levels of inflammatory and atherogenic hormones from adipose tissue in the pericardial fluid and circulation of cardiovascular disease patients.

Methods and Results

Venous plasma (P) and pericardial fluid (PF) were obtained from elective cardiothoracic surgery patients (n = 37). Concentrations of leptin, adipocyte fatty acid-binding protein (A-FABP) and adiponectin (APN) were determined by enzyme-linked immunosorbent assays (ELISA). The median concentration of leptin in PF (4.3 (interquartile range: 2.8–9.1) μg/L) was comparable to that in P (5.9 (2.2–11) μg/L) and these were significantly correlated to most of the same patient characteristics. The concentration of A-FABP was markedly higher (73 (28–124) versus 8.4 (5.2–14) μg/L) and that of APN was markedly lower (2.8 (1.7–4.2) versus 13 (7.2–19) mg/L) in PF compared to P. APN in PF was unlike in P not significantly related to age, body mass index, plasma triglycerides or coronary artery disease. PF levels of APN, but not A-FABP, were related to the size of paracardial adipocytes. PF levels of APN and A-FABP were not related to the immunoreactivity of paracardial adipocytes for these proteins.

Conclusion

In cardiac and vascular disease patients, PF is enriched in A-FABP and poor in APN. This adipokine microenvironment is more likely determined by the heart than by the circulation or paracardial adipose tissue.

MicroRNA profiling of pericardial fluid samples from patients with heart failure

AIMS

Multicellular organisms maintain vital functions through intercellular communication. Release of extracellular vesicles that carry signals to even distant target organs is one way of accomplishing this communication. MicroRNAs can also be secreted from the cells in exosomes and act as paracrine signalling molecules. In addition, microRNAs have been implicated in the pathogenesis of a large number of diseases, including cardiovascular diseases, and are considered as promising candidate biomarkers due to their relative stability and easy quantification from clinical samples. Pericardial fluid contains hormones secreted by the heart and is known to reflect the cardiac function. In this study, we sought to investigate whether pericardial fluid contains microRNAs and if so, whether they could be used to distinguish between different cardiovascular pathologies and disease stages.

METHODS AND RESULTS

Pericardial fluid was collected from heart failure patients during open-heart surgery. MicroRNA profiles of altogether 51 patients were measured by quantitative real-time PCR (qPCR) using Exiqon human panels I and II. On the average, 256 microRNAs were detected per sample, and 70 microRNAs out of 742 profiled microRNAs were detected in every sample. The five most abundant microRNAs in pericardial fluid were miR-21-5p, miR-451a, miR-125b-5p, let-7b-5p and miR-16-5p. No specific signatures for cardiovascular pathologies or clinically assessed heart failure stages could be detected from the profiles and, overall, microRNA profiles of the samples were found to be very similar despite the heterogeneity in the study population.

CONCLUSION

Measured microRNA profiles did not separate the samples according to the clinical features of the patients. However, several previously identified heart failure marker microRNAs were detected. The pericardial fluid microRNA profile appeared to be a result of an active and selective secretory process indicating that microRNAs may act as paracrine signalling factors by mediating the local crosstalk between cardiac cells.

Regular heartbeat rhythm at the heartbeat initiation stage is essential for normal cardiogenesis at low temperature

BACKGROUND

The development of blood flow in the heart is crucial for heart function and embryonic survival. Recent studies have revealed the importance of the extracellular matrix and the mechanical stress applied to the valve cushion that controls blood flow to the formation of the cardiac valve during embryogenesis. However, the events that trigger such valve formation and mechanical stress, and their temperature dependence have not been explained completely. Medaka (Oryzias latipes) inhabits a wide range of East Asia and adapts to a wide range of climates. We used medaka embryos from different genomic backgrounds and analyzed heartbeat characteristics including back-and-forth blood flow and bradyarrhythmia in embryos incubated at low temperature. We also used high-speed imaging analysis to examine the heartbeat of these animals after transient exposure to low temperature.

RESULTS

Embryos of the Hd-rR medaka strain exhibited back-and-forth blood flow in the heart (blood regurgitation) after incubation at 15 °C. This regurgitation was induced by exposure to low temperature around the heartbeat initiation period and was related to abnormalities in the maintenance or pattern of contraction of the atrium or the atrioventricular canal. The Odate strain from the northern Japanese group exhibited normal blood flow after incubation at 15 °C. High-speed time-lapse analysis of the heartbeat revealed that bradyarrhythmia occurred only in Hd-rR embryos incubated at 15 °C. The coefficient of contraction, defined as the quotient of the length of the atrium at systole divided by its length at diastole, was not affected in either strain. The average heart rate after removing the effect of arrhythmia did not differ significantly between the two strains, suggesting that the mechanical stress of individual myocardial contractions and the total mechanical stress could be equivalent, regardless of the presence of arrhythmia or the heart rate. Test-cross experiments suggested that this circulation phenotype was caused by a single major genomic locus.

CONCLUSIONS

These results suggest that cardiogenesis at low temperature requires a constant heartbeat. Abnormal contraction rhythms at the stage of heartbeat initiation may cause regurgitation at later stages. From the evolutionary viewpoint, strains that exhibit normal cardiogenesis during development at low temperature inhabit northern environments.

Patient-to-patient variability in autologous pericardial matrix scaffolds for cardiac repair

The pursuit of alternate therapies for end-stage heart failure post-myocardial infarction has led to the development of a variety of in situ gelling materials to be used as cellular or acellular scaffolds for cardiac repair. Previously, a protocol was established to decellularize human and porcine pericardia and process the extracellular matrix (ECM) into an injectable form. The resulting gels were found to retain components of the native extracellular matrix; cell infiltration was facilitated in vivo, and neovascularization was observed by 2 weeks. However, the assertion that an injectable form of human pericardial tissue could be a potentially autologous scaffold for myocardial tissue engineering requires assessment of the patient-to-patient variability. With this work, seven human pericardia from a relevant patient demographic are processed into injectable matrix materials that gel when brought to physiologic conditions. The resulting materials are compared with respect to their protein composition, glycosaminoglycan content, in vitro degradation, in vivo gelation, and microstructure. It is observed that a diminished collagen content in a subset of samples prevents in vitro gelation but not in vivo gelation at lower ECM concentrations. The structure is similarly fibrous and porous across all samples, implying the cell infiltration may be similarly facilitated. The biochemical composition as characterized by tandem mass spectrometry is comparable; basic ECM components are conserved across all samples, and the presence of a wide variety of ECM proteins and glycoproteins demonstrate the retention of biochemical complexity post-processing. It is concluded that the variability within human pericardial tissue specimens does not prevent them from being processed into injectable scaffolds; therefore, pericardial tissue offers a promising source as an autologous, injectable biomaterial scaffold.

The roles of natriuretic peptides in pericardial fluid in patients with heart failure

BACKGROUND

It is well known that the plasma concentrations of atrial and brain natriuretic peptides, as cardiac hormones, are elevated in heart failure.

HYPOTHESIS

Pericardial fluid in patients with various heart diseases contains both natriuretic peptides that are released into the pericardial fluid. However, it is unknown whether these peptides reflect cardiac function in patients with various heart diseases, more than both the peptides in blood.

METHODS

Plasma and pericardial fluid samples were obtained from 22 patients undergoing cardiac surgery for the measurement of atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) levels in plasma and pericardial fluid.

RESULTS

The ANP levels in pericardial fluid were higher in patients with impaired left ventricular systolic function (ejection fraction<50% versus>or=50%; 77.0+/-4.9 versus 14.0+/-50.9, p=0.017), but not BNP.However, BNP levels in pericardial fluid were significantly higher in patients with left ventricle dilatation (left ventricular diastolic dimension<or=54 mm versus>54 mm; 130.3+/-68.9: 709.7+/-324.7, p=0.0168). Moreover, BNP levels in pericardial fluid were significantly higher in Grade III than Grade II and I (Grade I: echo-free space<5 mm, Grade II: 5-10 mm, Grade III: >10 mm).

CONCLUSION

These results suggest that BNP levels in pericardial fluid served as more sensitive and accurate indicators of left ventricular diastolic dysfunction, and that increased BNP levels in pericardial fluid may have an important pathophysiologic role in heart failure as a cardiocyte-derived antifibrotic factor.

Brain natriuretic peptide concentration in pericardial fluid is independently associated with atrial fibrillation after off-pump coronary artery bypass surgery

OBJECTIVES

Postoperative atrial fibrillation is associated with the increased incidence of morbidities and mortality. Predisposing determinants of atrial fibrillation development after off-pump coronary artery bypass grafting remain unclear. We hypothesized that pericardial fluid natriuretic peptide concentrations have a predictive value for developing postoperative atrial fibrillation in patients who have undergone off-pump coronary artery bypass grafting.

METHODS

We prospectively measured atrial natriuretic peptide and brain natriuretic peptide concentrations in plasma and pericardial fluid in 42 consecutive patients undergoing off-pump coronary artery bypass grafting, then continuously observed the occurrence of atrial fibrillation following off-pump coronary artery bypass grafting until the time of discharge.

RESULTS

Postoperative atrial fibrillation was documented in nine patients (21%, atrial fibrillation group), and not in 33 patients (no atrial fibrillation group). Between the groups, there was neither significant difference in plasma atrial natriuretic peptide concentrations nor in pericardial atrial natriuretic peptide concentrations. Plasma brain natriuretic peptide concentrations were comparable in both groups [56.2 (interquartile range 42.7-102.8) vs. 35.2 pg/ml (13.8-75.0), P=0.07]. Pericardial fluid brain natriuretic peptide concentrations were significantly higher in the atrial fibrillation group than in the no atrial fibrillation group [188.0 (124.8-411.0) vs. 39.3 pg/ml (10.0-88.4), P=0.0001]. In a multivariable logistic regression model, pericardial brain natriuretic peptide concentration was significantly associated with a higher risk of postoperative atrial fibrillation (odds ratio=3.0 every 50 pg/ml increase; 95% confidence interval, 1.1-8.6; P=0.04).

CONCLUSION

Our results suggested that pericardial fluid brain natriuretic peptide concentration is independently associated with the development of atrial fibrillation after off-pump coronary artery bypass grafting.

Increased pericardial fluid level of matrix metalloproteinase-9 activity in patients with acute myocardial infarction: possible role in the development of cardiac rupture

BACKGROUND

In an animal model of acute myocardial infarction (AMI), deletion of matrix metalloproteinase (MMP)-9 results in suppression of the development of cardiac rupture. The present study sought to clarify how myocardial MMP-9 activity is related to the pathophysiologies of AMI and cardiac rupture in humans.

METHODS AND RESULTS

Levels of interleukin-8 (IL-8), polymorphonuclear leukocyte (PMN) elastase, monocyte chemotactic protein-1 (MCP-1) and MMP activity were measured in the pericardial fluid obtained from 28 patients with angina pectoris (AP group) and 16 patients with AMI (AMI group) undergoing cardiac surgery. In the AMI group, 5 were complicated with ventricular septal perforation (VSP) and the remaining 11 were not (non-VSP). Levels of IL-8, PMN elastase, MMP-2 and MMP-9 activity were all higher in the AMI group than in the AP group. In the AMI group, all levels other than MMP-2 activity were further elevated in cases with VSP compared with those in the non-VSP group. There was no significant difference in MCP-1 among the groups

CONCLUSIONS

Markers of neutrophil activation in the infarcted cardiac tissue seem to be elevated in AMI. Highly elevated levels of MMP-9 activity, which may be derived from neutrophils, and PMN elastase may be related to the pathophysiology of VSP or cardiac rupture in AMI.

Pericardial fluid and serum levels of vascular endothelial growth factor and endostatin in patients with or without coronary artery disease

BACKGROUND/PURPOSE

Vascular endothelial growth factor (VEGF) and endostatin are related to ischemic heart disease. This study investigated pericardial fluid and serum levels of VEGF and endostatin in patients with or without ischemic heart disease.

METHODS

A total of 39 patients (24 patients in the CAD group with significant coronary artery disease; 15 patients in the non-CAD group without coronary artery disease) undergoing open heart surgery were enrolled. In the CAD group, patients were classified according to good coronary collateralization (Group A; n = 11) or poor coronary collateralization (Group B; n = 13). Pericardial fluid and serum samples were obtained at the time of surgery. VEGF and endostatin were measured by enzyme-linked immunosorbent assay.

RESULTS

The levels of endostatin in both serum and pericardial fluid were significantly lower in the CAD group than in the non-CAD group (130.5 +/- 37.3 ng/mL vs. 172.4 +/- 37.8 ng/mL and 119.0 +/- 25.0 ng/mL vs. 143.0 +/- 23.5 ng/mL). The concentration of serum VEGF in the CAD group (92.6 +/- 18.2 pg/mL) was significantly higher than that in the non-CAD group (75.2 +/- 22.3 pg/mL). The concentration of serum VEGF in Group A (100.1 +/- 20.7 pg/mL) was significantly higher than that in Group B (84.3 +/- 12.4 pg/mL). The levels of pericardial fluid VEGF, serum and pericardial fluid endostatin were not significantly different between Groups A and B.

CONCLUSION

Patients with coronary artery disease have lower serum and pericardial fluid levels of endostatin and higher serum levels of VEGF. Serum level VEGF, but not endostatin, is associated with good or poor collateralization in patients with coronary artery disease.

Oxidative stress in pericardial fluid and plasma and its association with ventricular function

There are no studies evaluating oxidative stress markers both in pericardial fluid and plasma and whether they correlate with cardiac function indexes. The purpose of the study was to investigate whether oxidative stress markers in pericardial fluid and plasma are associated with left ventricular function.

METHODS AND RESULTS

Twenty-eight consecutive patients (class I or II NYHA) scheduled for myocardial revascularization, valve replacement, valve repair or closure of atrial septal defect. Plasma and pericardial fluid were collected and malondialdehyde, catalase, superoxide dismutase and glutathione peroxidase were determined. Left ventricular ejection fraction, left ventricular end diastolic diameter and left ventricular end systolic diameter were determined as echocardiographic indexes of ventricular function. We found that oxidative stress determined by a simple malondialdehyde (MDA) assay, correlated in plasma and pericardial fluid, and this parameter was associated with left ventricular end systolic diameter.

CONCLUSION

Plasma and pericardial fluid malondialdehyde levels can be used as an early marker of ventricular dysfunction.

Antioxidant capacity of the human pericardial fluid: does gender have a role?

The aim of the present study was to assess the antioxidant capacity in the serum and pericardial fluid of patients undergoing heart surgery for coronary heart disease (CHD) or valvular heart disease (VHD) and to find out whether there are gender-related differences in the antioxidant defense. This study involved 85 patients (35 VHD and 50 CHD) undergoing elective heart surgery. Blood samples from the peripheral vein and from the pericardial fluid were taken intraoperatively. Variables determined in the serum and pericardial fluid were: total protein, albumin, uric acid and antioxidant capacity. In the total patient population the antioxidant capacity in the pericardial fluid was lower than in the serum but still relatively high as determined by two independent techniques. No major differences were seen in serum or pericardial fluid antioxidant capacity between the two patient groups. In the overall patient population uric acid (p<0.05), albumin (p<0.01) and total protein concentrations (p<0.01) were, however, significantly greater in the pericardial fluid of male than of female patients. The pericardial fluid may contribute to the local antioxidant defense of the myocardium. It appears that male gender confers advantage in this respect. It remains to be elucidated whether this finding has any implication for the higher risk for women of perioperative complications and of cardiovascular mortality after coronary bypass grafting or coronary angioplasty.

Reduced pericardial levels of endostatin correlate with collateral development in patients with ischemic heart disease

OBJECTIVES

We investigated whether pericardial levels of a pro-angiogenic factor (vascular endothelial growth factor, VEGF) or an anti-angiogenic factor (endostatin) related to the presence of coronary collateral circulation in patients with significant coronary artery disease (CAD).

BACKGROUND

Coronary collateralization favorably alters the prognosis of patients with occlusive CAD. The specific factors that mediate and maintain collateral formation in coronary vessel occlusion are yet to be identified.

METHODS

Coronary angiograms from 39 patients undergoing coronary artery bypass surgery were evaluated for the absence of collaterals (n = 20) or the presence of Rentrop classification grade 3 collaterals (n = 19). Pericardial fluid samples were obtained at the time of surgery and were assayed for the VEGF and endostatin by enzyme-linked immunosorbent assay comparing the two groups of patients.

RESULTS

Vascular endothelial growth factor levels were not significantly different between the groups (28.86 +/- 4.67 pg/ml vs. 24.39 +/- 3.08 pg/ml, p = 0.43). However, pericardial fluid endostatin levels were nearly 40% lower in patients with grade 3 collateralization compared with those lacking angiographic evidence of collaterals (15.17 +/- 1.87 ng/ml vs. 24.25 +/- 2.08 ng/ml, p < 0.0025).

CONCLUSIONS

Pericardial fluid levels of endostatin, but not VEGF, are associated with the presence or absence of collaterals in patients with CAD. These data suggest that the angiogenesis inhibitor endostatin levels may locally modulate coronary collateral formation.