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Abstract Background Carbohydrate antigen 125 (CA125) is a proteolytic fragment of MUC-16 that is increased in heart failure (HF) and associated with inflammation, fluid overload, and worse adverse events. Our main objective was to study the expression of CA125 on epicardium and its association with inflammation, adipogenesis, and fibrosis. Methods Epicardial fat biopsies and blood were obtained from 151 non-selected patients undergoing open heart surgery. Immunohistochemistry, ELISA, or real-time PCR were used for analyzing protein or mRNA expression levels of CA125 and markers of inflammatory cells, fibroblasts, and adipocytes. Epithelial or stromal cells from epicardium were isolated and cultured to identify CA125 and its association with the adipogenesis and fibrosis pathways, respectively. Results The median age was 71 (63–74) years, 106 patients (70%) were male, and 62 (41%) had an established diagnosis of HF before surgery. The slice of epicardial fat biopsy determined a positive and colorimetric staining on the epithelial layer after incubating with the CA125 M11 antibody, providing the first description of CA125 expression in the human epicardium. Epicardial CA125 showed a strong and positive correlation with markers of inflammation and fibrosis in the epicardial fat tissue while exhibiting a negative correlation with markers of the adipogenesis pathway. This relationship remained significant after adjusting for potential confounders such as a prior HF diagnosis and plasma CA125 levels. Conclusion Epicardial cells express CA125, which is positively associated with inflammatory and fibroblast markers in epicardial adipose tissue. These results suggest that CA125 may be biologically involved in HF progression (transition from adipogenesis to fibrosis). Graphical Abstract

During heart development, the embryonic ventricle becomes enveloped by the epicardium, which adheres to the outer apical surface of the heart. This is concomitant with onset of ventricular trabeculation, where a subset of cardiomyocytes lose apicobasal polarity and delaminate basally from the ventricular wall. Llgl1 regulates the formation of apical cell junctions and apicobasal polarity, and we investigated its role in ventricular wall maturation. We found that llgl1 mutant zebrafish embryos exhibit aberrant apical extrusion of ventricular cardiomyocytes. While investigating apical cardiomyocyte extrusion, we identified a basal-to-apical shift in laminin deposition from the internal to the external ventricular wall. We find that epicardial cells express several laminin subunits as they adhere to the ventricle, and that the epicardium is required for laminin deposition on the ventricular surface. In llgl1 mutants, timely establishment of the epicardial layer is disrupted due to delayed emergence of epicardial cells, resulting in delayed apical deposition of laminin on the ventricular surface. Together, our analyses reveal an unexpected role for Llgl1 in correct timing of epicardial development, supporting integrity of the ventricular myocardial wall. [ABSTRACT FROM AUTHOR]

Background: Carbohydrate antigen 125 (CA125) is a proteolytic fragment of MUC-16 that is increased in heart failure (HF) and associated with inflammation, fluid overload, and worse adverse events. Our main objective was to study the expression of CA125 on epicardium and its association with inflammation, adipogenesis, and fibrosis. Methods: Epicardial fat biopsies and blood were obtained from 151 non-selected patients undergoing open heart surgery. Immunohistochemistry, ELISA, or real-time PCR were used for analyzing protein or mRNA expression levels of CA125 and markers of inflammatory cells, fibroblasts, and adipocytes. Epithelial or stromal cells from epicardium were isolated and cultured to identify CA125 and its association with the adipogenesis and fibrosis pathways, respectively. Results: The median age was 71 (63–74) years, 106 patients (70%) were male, and 62 (41%) had an established diagnosis of HF before surgery. The slice of epicardial fat biopsy determined a positive and colorimetric staining on the epithelial layer after incubating with the CA125 M11 antibody, providing the first description of CA125 expression in the human epicardium. Epicardial CA125 showed a strong and positive correlation with markers of inflammation and fibrosis in the epicardial fat tissue while exhibiting a negative correlation with markers of the adipogenesis pathway. This relationship remained significant after adjusting for potential confounders such as a prior HF diagnosis and plasma CA125 levels. Conclusion: Epicardial cells express CA125, which is positively associated with inflammatory and fibroblast markers in epicardial adipose tissue. These results suggest that CA125 may be biologically involved in HF progression (transition from adipogenesis to fibrosis). Highlights: This is the first time that CA125 was identified on human epicardium biopsies and primary culture of epithelial cells was performed. This is a promising tool for understanding the pathophysiological mechanisms association between CA-125 and HF progression. [ABSTRACT FROM AUTHOR]

The reactivated adult epicardium produces epicardium-derived cells (EPDCs) via epithelial-mesenchymal transition (EMT) to benefit the recovery of the heart after myocardial infarction (MI). SMARCA4 is the core catalytic subunit of the chromatin re-modeling complex, which has the potential to target some reactivated epicardial genes in MI. However, the effects of epicardial SMARCA4 on MI remain uncertain. This study found that SMARCA4 was activated over time in epicardial cells following MI, and some of activated cells belonged to downstream differentiation types of EPDCs. This study used tamoxifen to induce lineage tracing and SMARCA4 deletion from epicardial cells in Wt1-CreER;Smarca4 fl/fl ;Rosa26-RFP adult mice. Epicardial SMARCA4 deletion reduces the number of epicardial cells in adult mice, which was related to changes in the activation, proliferation, and apoptosis of epicardial cells. Epicardial SMARCA4 deletion reduced collagen deposition and angiogenesis in the infarcted area, exacerbated cardiac injury in MI. The exacerbation of cardiac injury was related to the inhibition of generation and differentiation of EPDCs. The alterations in EPDCs were associated with inhibited transition between E -CAD and N-CAD during the epicardial EMT, coupled with the down-regulation of WT1, SNAIL1, and PDGF signaling. In conclusion, this study suggests that Epicardial SMARCA4 plays a critical role in cardiac injury caused by MI, and its regulatory mechanism is related to epicardial EMT. Epicardial SMARCA4 holds potential as a novel molecular target for treating MI. [Display omitted] • Lineage tracing and SMARCA4 deletion in epicardial cells were achieved using Wt1-CreER;Smarca4fl/fl;Rosa26-RFP mice. • Epicardial SMARCA4 deletion exacerbated cardiac injury in myocardial infarction. • Epicardial SMARCA4 deletion inhibited the generation and differentiation of EPDCs in myocardial infarction. • The effects of Epicardial SMARCA4 deletion on EPDCs were related to the obstruction of epicardial EMT. [ABSTRACT FROM AUTHOR]

Key Clinical Message Epicardial metastasis from mixed germ cell tumors is exceedingly rare and poses a significant risk for cardiac morbidity. This case highlights the crucial need for comprehensive systemic evaluation in patients with known malignancies presenting with cardiac symptoms.

Despite extensive studies on endogenous heart regeneration within the past 20 years, the players involved in initiating early regeneration events are far from clear. Here, we assessed the function of neutrophils, the first-responder cells to tissue damage, during zebrafish heart regeneration. We detected rapid neutrophil mobilization to the injury site after ventricular amputation, peaking at 1-day post-amputation (dpa) and resolving by 3 dpa. Further analyses indicated neutrophil mobilization coincides with peak epicardial cell proliferation, and recruited neutrophils associated with activated, expanding epicardial cells at 1 dpa. Neutrophil depletion inhibited myocardial regeneration and significantly reduced epicardial cell expansion, proliferation, and activation. To explore the molecular mechanism of neutrophils on the epicardial regenerative response, we performed scRNA-seq analysis of 1 dpa neutrophils and identified enrichment of the FGF and MAPK/ERK signaling pathways. Pharmacological inhibition of FGF signaling indicated its' requirement for epicardial expansion, while neutrophil depletion blocked MAPK/ERK signaling activation in epicardial cells. Ligand-receptor analysis indicated the EGF ligand, hbegfa , is released from neutrophils and synergizes with other FGF and MAPK/ERK factors for induction of epicardial regeneration. Altogether, our studies revealed that neutrophils quickly motivate epicardial cells, which later accumulate at the injury site and contribute to heart regeneration. [Display omitted] • Neutrophil mobilization coincides with peak epicardial cell proliferation. • Neutrophils associated with activated, expanding epicardial cells. • Neutrophil significantly reduced epicardial cell expansion and activation. • FGF signaling is required for epicardial expansion. [ABSTRACT FROM AUTHOR]

Pericarditis is a group of polyetiological diseases often associated with emergence of life–threatening conditions. Poor knowledge of underlying cellular mechanisms and lack of relevant approaches to investigation of pericarditis result in major challenges in diagnosis and treatment.The aim of this work was to identify changes in the activity of autophagy in epicardial cells in acute pericarditis.Materials and methods. Acute pericarditis in mice was induced by intrapericardial injection of Freund's adjuvant in the study group (n=15). The control group included animals receiving either intrapericardial injection of phosphate-buffered saline (PBS) (n=15), or sham surgery without injections (n=7). On Days 3 or 5 after surgery the animals were euthanized under isoflurane anesthesia. Immunofluorescence staining of cardiac tissue cryo-sections and immunoblotting were used to assess the intensity of inflammation and autophagy in the epicardium.Results. Inflammation and other signs of acute pericarditis resulting in thickening of some epicardial areas were found: 68+9% in the control (after PBS injection) and 124+22% after Freund's adjuvant injection (p=0.009); other signs included cellular infiltration of epicardium and multiple adhesions. The epicardial layer exhibited signs of mesothelial cells reorganization with 11-fold increase of autophagy markers LC3 II/LC3 I ratio: 0.07+0.02 in the control group (after PBS injection) and 0.84+0.07 - in acute pericarditis (p=0.04), and accumulation of collagen fibers.Conclusion. Development of acute pericarditis is accompanied by activation of epicardial mesothelial cells, intensified autophagy and development of fibrous changes in epicacardial/ subepicardial areas.

Epicardial-derived cells (EPDCs) are involved in the regulation of myocardial growth and coronary vascularization and are critically important for proper development of the atrioventricular (AV) valves. SOX9 is a transcription factor expressed in a variety of epithelial and mesenchymal cells in the developing heart, including EPDCs. To determine the role of SOX9 in epicardial development, an epicardial-specific Sox9 knockout mouse model was generated. Deleting Sox9 from the epicardial cell lineage impairs the ability of EPDCs to invade both the ventricular myocardium and the developing AV valves. After birth, the mitral valves of these mice become myxomatous with associated abnormalities in extracellular matrix organization. This phenotype is reminiscent of that seen in humans with myxomatous mitral valve disease (MVD). An RNA-seq analysis was conducted in an effort to identify genes associated with this myxomatous degeneration. From this experiment, Cd109 was identified as a gene associated with myxomatous valve pathogenesis in this model. Cd109 has never been described in the context of heart development or valve disease. This study highlights the importance of SOX9 in the regulation of epicardial cell invasion—emphasizing the importance of EPDCs in regulating AV valve development and homeostasis—and reports a novel expression profile of Cd109 , a gene with previously unknown relevance in heart development. [Display omitted] • SOX9 controls epicardial-derived cell invasion into the developing heart. • Epicardial-derived cells are needed to maintain atrioventricular valve homeostasis. • Cd109 is identified as novel gene associated with valve development and disease. [ABSTRACT FROM AUTHOR]

The epicardium is a very dynamic cardiac layer with pivotal contributions during cardiogenesis, acting in the postnatal period as an apparently dormant single-cell layer. In mammalian embryos, the epicardium, which originates form the proepicardium, translocates into the pericardial cavity and subsequently rests on the surface of the myocardium. Later, it gives rise to the epicardium-derived cells, which migrate into subepicardial space, invade the developing myocardium, promoting its growth, and contribute to different cell types. Anomalies in the process of epicardial development, the generation of epicardium-derived cells and their signaling mechanisms in different experimental models lead to defective cardiac development, reminiscent of human congenital heart diseases. Furthermore, recent studies have reported that epicardial derivates in adults, i.e., epicardial adipose tissue, are associated with electrophysiological cardiovascular anomalies. Herein, we provide a state-of-the-art review focusing on both congenital and adult heart diseases associated with epicardial development. [ABSTRACT FROM AUTHOR]

Background/Aims: Obesity increases the risk of having COVID-19. To evaluate the relationship between body fat, muscle composition and visceral adipose tissue on computed tomography (CT) with COVID-19 outcome. Materials and Methods: One hundred forty-nine patients who had chest CT and a positive reverse transcriptase-polymerase chain reaction test were included. We measured the epicardial adipose tissue thickness (EAT) and liver density (LD), thoracic subcutaneous adipose tissue/pectoralis major (TSAT/PMJ), abdominal subcutaneous adipose tissue/psoas major muscle (ASAT/PSM), abdominal subcutaneous adipose tissue/erector spina muscle (ASAT/ESM) thickness ratios from thorax CT. Lymphocyte, platelet, neutrophil count, lymphocyte/neutrophil ratio and CRP were recorded. Results: The mean EAT was high in patients with a poor clinical course (in severe patients: 7.06±2.39 mm, in critical patients: 7.89±2.08 mm). The mean EAT of the ICU group was 7.70±2.14 mm, and it was 8.50±2.10 mm in the deceased patients. TSAT/PMJ was lower in deceased patients (0.90±0.36, p=0.038). ASAT/PSM and ASAT/ESM were also higher in the moderate group (2,27±1,60 and 0,51±0,25) (p=0.003. and p=0.019) than mild one (1.59±1.80, and 0.40±0.26). There was no difference in terms of DM, malignancy or gender. Conclusion: EAT was high in ICU admitted and deceased patients and should be used as a predictor of poor prognosis. [ABSTRACT FROM AUTHOR]

IntroductionSignal-averaged electrocardiography (SAECG) provides diagnostic and prognostic information regarding cardiac diseases. However, its value in other nonischemic cardiomyopathies (NICMs) remains unclear. This study aimed to investigate the role of SAECG in patients with NICM.Methods and resultsThis retrospective study included consecutive patients with NICM who underwent SAECG, biventricular substrate mapping, and ablation for ventricular arrhythmia (VA). Patients with baseline ventricular conduction disturbances were excluded. Patients who fulfilled at least one SAECG criterion were categorized into Group 1, and the other patients were categorized into Group 2. Baseline and ventricular substrate characteristics were compared between the two groups. The study included 58 patients (39 men, mean age 50.4 ± 15.5 years), with 34 and 24 patients in Groups 1 and 2, respectively. Epicardial mapping was performed in eight (23.5%) and six patients (25.0%) in Groups 1 and 2 (p = 0.897), respectively. Patients in Group 1 had a more extensive right ventricular (RV) low-voltage zone (LVZ) and scar area than those in Group 2. Group 1 had a larger epicardial LVZ than Group 2. Epicardial late potentials were more frequent in Group 1 than in Group 2. There were more arrhythmogenic foci within the RV outflow tract in Group 1 than in Group 2. There was no significant difference in long-term VA recurrence.ConclusionIn our NICM population, a positive SAECG was associated with a larger RV endocardial scar, epicardial scar/late potentials, and a higher incidence of arrhythmogenic foci in the RV outflow tract.

The epicardium is a very dynamic cardiac layer with pivotal contributions during cardiogenesis, acting in the postnatal period as an apparently dormant single-cell layer. In mammalian embryos, the epicardium, which originates form the proepicardium, translocates into the pericardial cavity and subsequently rests on the surface of the myocardium. Later, it gives rise to the epicardium-derived cells, which migrate into subepicardial space, invade the developing myocardium, promoting its growth, and contribute to different cell types. Anomalies in the process of epicardial development, the generation of epicardium-derived cells and their signaling mechanisms in different experimental models lead to defective cardiac development, reminiscent of human congenital heart diseases. Furthermore, recent studies have reported that epicardial derivates in adults, i.e., epicardial adipose tissue, are associated with electrophysiological cardiovascular anomalies. Herein, we provide a state-of-the-art review focusing on both congenital and adult heart diseases associated with epicardial development.

Abstract The epicardium is the important outermost mesothelial/epithelial layer of the heart that serves as a signaling center for cardiac development and repair. During heart development, epicardial cells undergo a process known as epithelial-to-mesenchymal transition to form diverse mesenchymal cell lineages, such as fibroblasts, coronary vascular smooth muscle cells, and pericytes. However, it is not clear whether the reverse process, mesenchymal-to-epithelial transition (MET), takes place in the mammalian heart. In this study, we performed apical resection on neonatal hearts and used Fap-CreER;Ai9 labeling to track activated fibroblasts in the injured cardiac regions. We found that these fibroblasts underwent MET to generate epicardial cells during heart regeneration. To our knowledge, this is the first report of MET occurring in vivo during heart development and regeneration. Our findings suggest that it is feasible to directly convert fibroblasts into epicardial cells, providing a novel approach to generate epicardial cells.

Featured Application: This study proposes an epicardial adipose tissue (EAT) analysis using an advanced computer-assisted approach in a population of patients undergoing Cardiac CT (CCT) during statin administration, in relation to the body mass index (BMI). The epicardial adipose tissue (EAT) is the visceral fat located between the myocardium and the pericardium. We aimed to perform a longitudinal evaluation of the epicardial adipose tissue using an advanced computer-assisted approach in a population of patients undergoing Cardiac CT (CCT) during statin administration, in relation to their body mass index (BMI). We retrospectively enrolled 95 patients [mean age 62 ± 10 years; 68 males (72%) and 27 females (28%)] undergoing CCT for suspected coronary artery disease during statin administration. CCT was performed at two subsequent time points. At the second CCT, EAT showed a mean density increase (−75.59 ± 7.0 HU vs. −78.18 ± 5.3 HU, p < 0.001) and a volume decrease (130 ± 54.3 cm3 vs.142.79 ± 56.9 cm3, p < 0.001). Concerning coronary artery EAT thickness, a reduction was found at the origin of the right coronary artery (13.26 ± 5.2 mm vs. 14.94 ± 5.8, p = 0.001) and interventricular artery (8.22 ± 3.7 mm vs. 9.13 ± 3.9 mm, p = 0.001). The quartile (Q) attenuation percentage (%) distribution of EAT changed at the second CCT. The EAT % distribution changed by the BMI in Q1 (p = 0.015), Q3 (p = 0.001) and Q4 (p = 0.043) at the second CCT, but the normal-BMI and overweight/obese patients showed a similar response to statin therapy in terms of quartile distribution changes. In conclusion, statins may determine significant changes in EAT quantitative and qualitative characteristics detected by CCT; the BMI influences the EAT composition, but statins determine a similar response in quartile distribution's variation, irrespective of the BMI. [ABSTRACT FROM AUTHOR]

Key Clinical Message: Epicardial metastasis from mixed germ cell tumors is exceedingly rare and poses a significant risk for cardiac morbidity. This case highlights the crucial need for comprehensive systemic evaluation in patients with known malignancies presenting with cardiac symptoms. [ABSTRACT FROM AUTHOR]

The article discusses the role of the epicardium, a layer of cells that covers the outer surface of the heart, in cardiac development and regeneration. The authors highlight recent research on epicardioids, which are cardiac organoids that mimic the self-organization and functionality of the ventricular myocardium with an external epicardial layer. These epicardioids have provided insights into the functions of the epicardium, including its role as a source of progenitor cells and a facilitator of myocardial compaction and maturation. The article also emphasizes the potential of epicardioids for studying developmental processes and investigating therapeutic strategies for cardiac regeneration. [Extracted from the article]

Background The area of abnormal bipolar potentials in the right ventricular epicardium is recognized as an arrhythmogenic substrate in patients with Brugada syndrome (BrS); however, the correlation between local potentials and Brugada-type surface electrocardiograms (ECGs) remains unclear. Case summary A 49-year-old man with BrS who was hospitalized for refractory ventricular fibrillation underwent an electrocardiographic study with unipolar electrodes with the same bandwidth as surface ECGs. The right ventricular outflow tract epicardium showed abnormal bipolar potentials composed of split sharp and delayed dull components with coved-type J-ST elevation in the unipolar electrodes. The additional stimuli from the atrium gradually decreased the number of unipolar electrodes showing coved-type J-ST elevation along with a shortening of the local bipolar activation time. The pilsicainide provocation test induced a change in unipolar morphology from coved type to convex type and an intermittent local block of the divided and sharp components in bipolar electrodes. Of note, the unipolar J-ST elevation was not changed along with the localized conduction block in bipolar leads. Discussion The unipolar electrode waveforms during sinus rhythm change together with bipolar electrodes, consisting of sharp and blunt components in BrS. However, the convex-type J-ST elevation in unipolar leads persisted irrespective of the local conduction block in bipolar leads after pilsicainide provocation. These findings suggest the complexity of BrS mechanisms. [ABSTRACT FROM AUTHOR]

The epicardium is the important outermost mesothelial/epithelial layer of the heart that serves as a signaling center for cardiac development and repair. During heart development, epicardial cells undergo a process known as epithelial-to-mesenchymal transition to form diverse mesenchymal cell lineages, such as fibroblasts, coronary vascular smooth muscle cells, and pericytes. However, it is not clear whether the reverse process, mesenchymal-to-epithelial transition (MET), takes place in the mammalian heart. In this study, we performed apical resection on neonatal hearts and used Fap-CreER;Ai9 labeling to track activated fibroblasts in the injured cardiac regions. We found that these fibroblasts underwent MET to generate epicardial cells during heart regeneration. To our knowledge, this is the first report of MET occurring in vivo during heart development and regeneration. Our findings suggest that it is feasible to directly convert fibroblasts into epicardial cells, providing a novel approach to generate epicardial cells. [ABSTRACT FROM AUTHOR]

Background: Endocardial ablation is effective for most focal atrial tachycardias (FATs). In rare circumstances, the FAT can originate from the epicardial side of atrium.Objective: In the present study, we retrospectively assessed the percutaneous approach for epicardial ablation of FAT when standard endocardial ablation had failed.Methods: Among a consecutive 186 patients undergoing ablation for 198 FATs, epicardial mapping and ablation via a percutaneous subxiphoid approach were attempted in ten patients due to failed endocardial ablation.Results: In three cases, the origin of FAT was at the epicardial side of the junction of the right atrial appendage (RAA) and superior vena cava (SVC). In three cases, the origin of FAT was located in the epicardial region of the LA insertion of Bachmann's bundle (BB). In two cases, the FAT originated from the epicardial side of right atrial free wall. In one case, the FAT was successfully ablated from the epicardial side of the RAA, and in the remaining case, the origin of FAT was located in the epicardial region of the vein of Marshall (VOM). All FATs were successfully eliminated by ablation at the epicardial earliest activation site (EAS).Conclusions: Epicardial mapping and ablation can be considered as an effective and safe option for FAT resistant to endocardial ablation. [ABSTRACT FROM AUTHOR]

Aims The long-QT syndrome (LQTS) represents a leading cause of sudden cardiac death (SCD). The aim of this study was to assess the presence of an underlying electroanatomical arrhythmogenic substrate in high-risk LQTS patients. Methods and results The present study enrolled 11 consecutive LQTS patients who had experienced frequent implantable cardioverter-defibrillator (ICD discharges triggered by ventricular fibrillation (VF). We acquired electroanatomical biventricular maps of both endo and epicardial regions for all patients and analyzed electrograms sampled from several myocardial regions. Abnormal electrical activities were targeted and eliminated by the means of radiofrequency catheter ablation. VF episodes caused a median of four ICD discharges in eleven patients (6 male, 54.5%; mean age 44.0 ± 7.8 years, range 22–53) prior to our mapping and ablation procedures. The average QTc interval was 500.0 ± 30.2 ms. Endo-epicardial biventricular maps displayed abnormally fragmented, low-voltage (0.9 ± 0.2 mV) and prolonged electrograms (89.9 ± 24.1 ms) exclusively localized in the right ventricular epicardium. We found electrical abnormalities extending over a mean epicardial area of 15.7 ± 3.1 cm2. Catheter ablation of the abnormal epicardial area completely suppressed malignant arrhythmias over a mean 12 months of follow-up (median VF episodes before vs. after ablation, 4 vs. 0; P = 0.003). After the procedure, the QTc interval measured in a 12-lead ECG analysis shortened to a mean of 461.8 ± 23.6 ms (P = 0.004). Conclusion This study reveals that, among high-risk LQTS patients, regions localized in the epicardium of the right ventricle harbour structural electrophysiological abnormalities. Elimination of these abnormal electrical activities successfully prevented malignant ventricular arrhythmia recurrences. [ABSTRACT FROM AUTHOR]

Background: A regimen of rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) is the standard treatment for non-Hodgkin's lymphoma. Brown adipose tissue possesses anti-cancer potential. This study aimed to explore practical biomarkers for non-Hodgkin's lymphoma by analyzing the metabolic activity of adipose tissue. Methods: Twenty patients who received R-CHOP for non-Hodgkin's lymphoma were reviewed. Positron emission tomography/computed tomography (PET/CT) images, lactate dehydrogenase (LDH) levels, and body mass index (BMI) before and after treatment were collected. Regions with a high standardized uptake value (SUV) in epicardial and orbital adipose tissue were selected and analyzed by a PET/CT viewer. The initial measurements and changes in the high SUV of epicardial and orbital adipose tissues, LDH levels, and BMI of treatment responders and non-responders, and complete and partial responders, were compared. Results: The volumes of high-SUV epicardial and orbital adipose tissues significantly increased in responders after R-CHOP (p = 0.03 and 0.002, respectively). There were significant differences between changes in the high-SUV volumes of epicardial and orbital adipose tissues (p = 0.03 and 0.001, respectively) and LDH levels (p = 0.03) between responders and non-responders. The changes in high-SUV epicardial adipose tissue volumes were greater among complete responders than partial responders (p = 0.04). Poorer treatment responses were observed in patients with lower high-SUV epicardial adipose tissue volumes and higher LDH levels after R-CHOP (p = 0.03 and 0.03, respectively). Conclusions: The preliminary results of greater changes in high-SUV epicardial and orbital adipose tissue volumes among responders indicate that brown adipose tissue could be considered a favorable prognostic biomarker. [ABSTRACT FROM AUTHOR]

Purpose: Idiopathic epicardial ventricular arrhythmias (VAs) are clustered in the areas of the summit and crux. This study was to report a group of idiopathic epicardial VAs remote from the summit and crux areas. Methods: In total, 9 patients (6 males, mean age 32 ± 13 years) were enrolled. The locations were identified by epicardial mapping and ablation. The electrocardiographic and electrophysiological characteristics were compared to those of 9 patients who had VAs ablated at the opposite endocardial site. Results: VAs were identified at the epicardium, with 4 patients had VAs located at the inferior wall, one at the anterior wall, one at the apex and 3 patients had VAs at the lateral wall. A "QS" type at the location-related leads was the only identified surface electrocardiogram indication suggesting epicardial origin (compared to that of the controls, 100% vs 0%, p<0.001). Endocardial and epicardial mapping revealed pre-maturities of −11 ± 4 ms and −25 ± 8 ms, respectively (VS. −28 ± 8 ms revealed by endocardial mapping in control patients, p<0.001 and p=0.389, respectively). All of the study cases demonstrated an "rS" pattern in the endocardial unipolar electrogram. Acute and long-term successful ablation (a median of 11 months of follow-up) was achieved in all patients without complications. Conclusions: A distinct group of idiopathic VAs remote from the summit and crux areas warranting ablation by a subxiphoid approach were identified. Morphological ECG features of a "QS" type among the location-related grouped leads combined with the mapping findings helped in the identification of the epicardial site of origin. [ABSTRACT FROM AUTHOR]

Coronary artery disease (CAD) is widely considered a chronic inflammatory disorder, and dysfunction of epicardial adipose tissue could be an important source of the inflammation. Amino-terminal fragment of pro-B-type natriuretic peptide (NT-proBNP) is a known marker of cardiovascular disorders of cardiac origin. Recent studies show that inflammatory stimuli may influence its secretion. Our purpose was to evaluate NT-proBNP serum concentration in relation to immune cell ratios in epicardial adipose tissue (EAT), and cytokine levels in the patients with stable CAD. Patients with stable CAD and heart failure classified into classes II–III, according to the New York Heart Association (NYHA) scale, scheduled for the coronary artery bypass graft (CABG) surgery, were recruited into the study (n = 10; 59.5 (53.0-65.0) y. o.; 50% males). The EAT and subcutaneous adipose tissue (SAT) specimens were harvested in the course of CABG surgery. Immunostaining with anti-CD68, anti-CD45, antiIL-1β and anti-TNFα monoclonal antibodies was performed to evaluate cell composition by differential counts per ten fields (400 magnification). Fasting venous blood was obtained from patients before CABG. Blood was centrifuged at 1500g, aliquots were collected and stored frozen at -40 °С until final analysis. Concentrations of NT-proBNP, IL-1β, IL-6, IL-10, TNFα were determined in serum samples by enzyme-linked immunosorbent assay (ELISA). We have found increased production of IL-1β and TNFα cytokines in EAT compared to SAT. Concentrations of NT-proBNP exceeded 125 pg/ml in 4 patients, and correlations between the CD68+ macrophage counts in both EAT and SAT samples (rs = 0.762; p = 0.010 and rs = 0.835; p = 0.003, respectively). NT-proBNP levels showed positive relations with CD45+ leukocyte counts (rs = 0.799; p = 0.006), and with IL-1β+ cell numbers (rs = 0.705; p = 0.023) in EAT samples only. As for the serum biomarkers, NT-proBNP levels showed negative correlation with fasting glucose levels (rs = -0.684; p = 0.029), and positive correlation with serum IL-6 concentrations (rs = 0.891; p = 0.001). Increased serum concentrations of NT-proBNP in CAD patients correlate with accumulation of macrophages in EAT, which is associated with increased production of IL-1β in EAT and correlates with some metabolic parameters.

The embryonic epicardium originates from the proepicardium, an extracardiac primordium constituted by a cluster of mesothelial cells. In early embryos, the embryonic epicardium is characterized by a squamous cell epithelium resting on the myocardium surface. Subsequently, it invades the subepicardial space and thereafter the embryonic myocardium by means of an epithelial–mesenchymal transition. Within the myocardium, epicardial-derived cells present multilineage potential, later differentiating into smooth muscle cells and contributing both to coronary vasculature and cardiac fibroblasts in the mature heart. Over the last decades, we have progressively increased our understanding of those cellular and molecular mechanisms driving proepicardial/embryonic epicardium formation. This study provides a state-of-the-art review of the transcriptional and emerging post-transcriptional mechanisms involved in the formation and differentiation of the embryonic epicardium.

The epicardial adipose tissue (EAT) is the visceral fat located between the myocardium and the pericardium. We aimed to perform a longitudinal evaluation of the epicardial adipose tissue using an advanced computer-assisted approach in a population of patients undergoing Cardiac CT (CCT) during statin administration, in relation to their body mass index (BMI). We retrospectively enrolled 95 patients [mean age 62 ± 10 years; 68 males (72%) and 27 females (28%)] undergoing CCT for suspected coronary artery disease during statin administration. CCT was performed at two subsequent time points. At the second CCT, EAT showed a mean density increase (−75.59 ± 7.0 HU vs. −78.18 ± 5.3 HU, p < 0.001) and a volume decrease (130 ± 54.3 cm3 vs.142.79 ± 56.9 cm3, p < 0.001). Concerning coronary artery EAT thickness, a reduction was found at the origin of the right coronary artery (13.26 ± 5.2 mm vs. 14.94 ± 5.8, p = 0.001) and interventricular artery (8.22 ± 3.7 mm vs. 9.13 ± 3.9 mm, p = 0.001). The quartile (Q) attenuation percentage (%) distribution of EAT changed at the second CCT. The EAT % distribution changed by the BMI in Q1 (p = 0.015), Q3 (p = 0.001) and Q4 (p = 0.043) at the second CCT, but the normal-BMI and overweight/obese patients showed a similar response to statin therapy in terms of quartile distribution changes. In conclusion, statins may determine significant changes in EAT quantitative and qualitative characteristics detected by CCT; the BMI influences the EAT composition, but statins determine a similar response in quartile distribution’s variation, irrespective of the BMI.

The outermost layer of the heart, the epicardium, is an essential cell population that contributes, through epithelial-to-mesenchymal transition (EMT), to the formation of different cell types and provides paracrine signals to the developing heart. Despite its quiescent state during adulthood, the adult epicardium reactivates and recapitulates many aspects of embryonic cardiogenesis in response to cardiac injury, thereby supporting cardiac tissue remodeling. Thus, the epicardium has been considered a crucial source of cell progenitors that offers an important contribution to cardiac development and injured hearts. Although several studies have provided evidence regarding cell fate determination in the epicardium, to date, it is unclear whether epicardium-derived cells (EPDCs) come from specific, and predetermined, epicardial cell subpopulations or if they are derived from a common progenitor. In recent years, different approaches have been used to study cell heterogeneity within the epicardial layer using different experimental models. However, the data generated are still insufficient with respect to revealing the complexity of this epithelial layer. In this review, we summarize the previous works documenting the cellular composition, molecular signatures, and diversity within the developing and adult epicardium.

The epicardium is a single cell layer of mesothelial cells that plays a critical role during heart development contributing to different cardiac cell types of the developing heart through epithelial-to-mesenchymal transition (EMT). Moreover, the epicardium is a source of secreted growth factors that promote myocardial growth. CCBE1 is a secreted extracellular matrix protein expressed by epicardial cells that is required for the formation of the primitive coronary plexus. However, the role of CCBE1 during epicardial development was still unknown. Here, using a Ccbe1 knockout (KO) mouse model, we observed that loss of CCBE1 leads to congenital heart defects including thinner and hyper-trabeculated ventricular myocardium. In addition, Ccbe1 mutant hearts displayed reduced proliferation of cardiomyocyte and epicardial cells. Epicardial outgrowth culture assay to assess epicardial-derived cells (EPDC) migration showed reduced invasion of the collagen gel by EPDCs in Ccbe1 KO epicardial explants. Ccbe1 KO hearts also displayed fewer nonmyocyte/nonendothelial cells intramyocardially with a reduced proliferation rate. Additionally, RNA-seq data and experimental validation by qRT-PCR showed a marked deregulation of EMT-related genes in developing Ccbe1 mutant hearts. Together, these findings indicate that the myocardium defects in Ccbe1 KO mice arise from disruption of epicardial development and function. [ABSTRACT FROM AUTHOR]

Understanding the molecular mechanisms of epicardial epithelial-to-mesenchymal transition (EMT), particularly in directing cell fate toward epicardial derivatives, is crucial for regenerative medicine using human induced pluripotent stem cell (iPSC)-derived epicardium. Although transforming growth factor β (TGF-β) plays a pivotal role in epicardial biology, orchestrating EMT during embryonic development via downstream signaling through SMAD proteins, the function of SMAD proteins in the epicardium in maintaining vascular homeostasis or mediating the differentiation of various epicardial-derived cells (EPDCs) is not yet well understood. Our study reveals that TGF-β-independent SMAD3 expression autonomously predicts epicardial cell specification and lineage maintenance, acting as a key mediator in promoting the angiogenic-oriented specification of the epicardium into cardiac pericyte progenitors. This finding uncovers a novel role for SMAD3 in the human epicardium, particularly in generating cardiac pericyte progenitors that enhance cardiac microvasculature angiogenesis. This insight opens new avenues for leveraging epicardial biology in developing more effective cardiac regeneration strategies., Competing Interests: Declaration of interests Y.Y. is a scientific advisor of Orizuru Therapeutics and receives grants from Takeda Pharmaceutical Company and Altos Labs, Inc. outside the submitted work., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

Cardiovascular disease (CVD) is one of the leading causes of mortality worldwide, and frequently leads to massive heart injury and the loss of billions of cardiac muscle cells and associated vasculature. Critical work in the last 2 decades demonstrated that these lost cells can be partially regenerated by the epicardium, the outermost mesothelial layer of the heart, in a process that highly recapitulates its role in heart development. Upon cardiac injury, mature epicardial cells activate and undergo an epithelial-mesenchymal transition (EMT) to form epicardium-derived progenitor cells (EpiPCs), multipotent progenitors that can differentiate into several important cardiac lineages, including cardiomyocytes and vascular cells. In mammals, this process alone is insufficient for significant regeneration, but it might be possible to prime it by administering specific reprogramming factors, leading to enhanced EpiPC function. Here, we show that oxytocin (OXT), a hypothalamic neuroendocrine peptide, induces epicardial cell proliferation, EMT, and transcriptional activity in a model of human induced pluripotent stem cell (hiPSC)-derived epicardial cells. In addition, we demonstrate that OXT is produced after cardiac cryoinjury in zebrafish, and that it elicits significant epicardial activation promoting heart regeneration. Oxytocin signaling is also critical for proper epicardium development in zebrafish embryos. The above processes are significantly impaired when OXT signaling is inhibited chemically or genetically through RNA interference. RNA sequencing data suggests that the transforming growth factor beta (TGF-β) pathway is the primary mediator of OXT-induced epicardial activation. Our research reveals for the first time an evolutionary conserved brain-controlled mechanism inducing cellular reprogramming and regeneration of the injured mammalian and zebrafish heart, a finding that could contribute to translational advances for the treatment of cardiac injuries.

Background: Certain nonmammalian species such as zebrafish have an elevated capacity for innate heart regeneration. Understanding how heart regeneration occurs in these contexts can help illuminate cellular and molecular events that can be targets for heart failure prevention or treatment. The epicardium, a mesothelial tissue layer that encompasses the heart, is a dynamic structure that is essential for cardiac regeneration in zebrafish. The extent to which different cell subpopulations or states facilitate heart regeneration requires research attention.Methods: To dissect epicardial cell states and associated proregenerative functions, we performed single-cell RNA sequencing and identified 7 epicardial cell clusters in adult zebrafish, 3 of which displayed enhanced cell numbers during regeneration. We identified paralogs of hapln1 as factors associated with the extracellular matrix and largely expressed in cluster 1. We assessed HAPLN1 expression in published single-cell RNA sequencing data sets from different stages and injury states of murine and human hearts, and we performed molecular genetics to determine the requirements for hapln1-expressing cells and functions of each hapln1 paralog.Results: A particular cluster of epicardial cells had the strongest association with regeneration and was marked by expression of hapln1a and hapln1b. The hapln1 paralogs are expressed in epicardial cells that enclose dedifferentiated and proliferating cardiomyocytes during regeneration. Induced genetic depletion of hapln1-expressing cells or genetic inactivation of hapln1b altered deposition of the key extracellular matrix component hyaluronic acid, disrupted cardiomyocyte proliferation, and inhibited heart regeneration. We also found that hapln1-expressing epicardial cells first emerge at the juvenile stage, when they associate with and are required for focused cardiomyocyte expansion events that direct maturation of the ventricular wall.Conclusions: Our findings identify a subset of epicardial cells that emerge in postembryonic zebrafish and sponsor regions of active cardiomyogenesis during cardiac growth and regeneration. We provide evidence that, as the heart achieves its mature structure, these cells facilitate hyaluronic acid deposition to support formation of the compact muscle layer of the ventricle. They are also required, along with the function of hapln1b paralog, in the production and organization of hyaluronic acid-containing matrix in cardiac injury sites, enabling normal cardiomyocyte proliferation and muscle regeneration. [ABSTRACT FROM AUTHOR]