bluuebunny/crossref_metadata_2025_split huggingface dataset:
Milk-derived extracellular vehicles alleviate heart failure with preserved ejection fraction by modulating gut microbiota
Authors: Zhang S , Tong L , Hao H , Huang C , Tan D , Sikka V , Lou C , Yu X , Yang L , Lin Y , Storm G , Wang J 
Published: October 2024

Abstract

Background
Accounting for around 50% of human heart failure, heart failure with preserved ejection fraction (HFpEF) is driven by complex and heterogeneous pathological factors, including gut microbiome dysbiosis. We have previously reported that milk-derived extracellular vesicles (mEVs) modulate the gut microbiota in inflammatory bowel disease. However, whether mEVs can affect gut microbiota and thereby alleviate HFpEF remains unexplored.

Aims
We aim to uncover potential therapeutic effects of mEVs on HFpEF and if so, the underlying mechanisms.

Methods
The HFpEF mouse model was generated by feeding C57/B6 mice on a high-fat diet and L-NAME for 15 weeks. Mouse feces samples were analyzed to detect the presence of gut dysbiosis in HFpEF. Mice received bovine mEVs through oral gavage. Heart function was assessed with echocardiography. Mouse feces and plasma were collected to analyze gut microbiota and metabolomics, respectively.

Results
Gut microbiota was disturbed in HFpEF mice. Oral administration of mEVs effectively attenuated heart failure which was evidenced by less bodyweight gain, reduction in cardiac hypertrophy and lung weight, and improvement in cardiac function parameters such as ratios of E/A (1.8 vs. 1.5, p&lt;0.05) and E/E’ (40 vs. 27, p&lt;0.05). Moreover, the increase in mouse blood pressure in HFpEF was also inhibited upon treatment (SBP 130mmHg vs. 100mmHg, DBP 90mmHg vs. 75mmHg, p&lt;0.05). Mechanistically, we ruled out the possibility of direct action of mEVs on the heart as orally administered mEVs were only distributed in the intestine. On the other hand, mEVs restored gut microbiota by increasing the abundance of beneficial bacteria such as Lachnospiraceae. As a result, oral administration of mEVs elevated blood levels of Lachnospiraceae metabolite, butyric acid, a type of short-chain fatty acid. To confirm the butyric acid-mediated heart-protective effects of mEVs, we administered butyric acid to HFpEF mice. Strikingly, butyric acid largely reproduced the therapeutic effects of mEVs on HFpEF.

Conclusions
Oral administration of mEVs restores gut microbiota dysbiosis, thereby attenuating heart failure in HFpEF. mEVs may represent a new biological therapeutic for the treatment of HFpEF.
The intracardiac echocardiographic findings during rewarming using catheter-based cryoablation
Authors: Sugitani M , Takanao M , Takahashi S , Terao S , Kogame T , Ishihara M 
Published: October 2024

Abstract

Introduction
Cryoablation unlike radiofrequency ablation (RFA) does not damage the endothelium and lining and causes less physical damage, and the mechanisms remain unclear. The increased myocardial echogenicity (iME) observed by intracardiac echocardiography (ICE) during RFA has been reported as the ablation indicator.

Purpose
To evaluate the ICE findings during ablation using catheter-based cryoablation.

Methods
In an extra vivo experiment, we set the bovine myocardium to 36°C in a constant temperature bath and experimented on a water tank that generated a non-pulsatile flow. Catheter-based cryoablation was applied to the bovine myocardium at -80 degrees for 240 seconds. The ICE images were evaluated using ViewFlex Xtra during catheter-based cryoablation.

Results
Macroscopic change (Figure 1): Four seconds after the start of cooling, a thin film of ice began to form between the myocardium and the catheter, and after 7 seconds, the tip of the catheter was covered with ice and the surface of the myocardium was covered with ice. After that, it grew rapidly and an ice ball was formed. There was no change after 18 seconds of cooling. ICE findings (Figure 2): 4 seconds after cooling started, the ME around the catheter tip began to increase, and the ME gradually increased with flickering. The iME stopped after cooling down for 18 seconds and did not change after that. Immediately after stopping cooling, severe flickering occurred and the area of iME began to shrink. The ME gradually returned to its original state with slight bubbles from the central ablation site. Macroscopic change and ICE findings were reproducibly confirmed. Myocardial findings after ablation: The area of cooling was discernible, but the color difference from the surrounding area was not obvious.

Conclusions
The catheter-based cryoablation ablation shows the severest change detected by ICE immediately after stopping cooling. In addition to tissue damage during the freezing stage, the rewarming may be more associated with tissue damage.
Chromatin remodeling by the histone methyltransferase SETD2 drives cardiometabolic heart failure with preserved ejection fraction
Authors: Costantino S , Ambrosini S , Mohammed S A , Gorica E , Ruschitzka F , Paneni F 
Published: October 2024

Abstract

Background
Cardiometabolic heart failure with preserved ejection fraction (cHFpEF) is highly prevalent and associates with a poor outcome. Pathological gene expression in heart failure is accompanied by changes in active histone marks without major alterations in DNA methylation. Histone 3 trimethylation at lysine 36 (H3k36me3) - a chromatin signature induced by the histone methyltransferase SETD2 – has shown a strong correlation with changes in gene expression in the human failing heart; however its role in cardiac disease is poorly understood. The present study investigates the role of SETD2/ H3k36me3 in cHFpEF.

Purpose
To investigate the role of chromatin remodelling in obese HFpEF (obHFpEF).

Methods
Mice with cardiomyocyte-specific deletion of SETD2 (c-SETD2-/-) were generated and subjected to high fat diet feeding and L-NAME treatment for 15 weeks to induce cHFpEF. Cardiac function and exercise tolerance were assessed by echocardiography and Treadmill exhaustion test, respectively. ChIP-Seq datasets were employed to determine the biological pathways regulated by H3k36me3, whereas chromatin immunoprecipitation assays (ChIP) were performed to investigate SETD2/H3k36me3 enrichment on gene promoters. SETD2 gain- and loss-of-function experiments were performed in cultured cardiomyocytes (CMs) exposed to metabolic stress (palmitic acid). SETD2/H3k36me3 axis was also investigated in left ventricular (LV) myocardial specimens from patients with cHFpEF and control donors. Moreover, pharmacological inhibition of SETD2 was performed in skinned CMs from cHFpEF patients.

Results
Bioinformatic analysis of ChIP-Seq data in mouse CMs showed a strong involvement of SETD2/H3k36me3 in lipid-related pathways. Specifically, SETD2 and H3k36me3 were upregulated in cHFpEF vs. control mouse hearts and were highly enriched on the promoter of sterol regulatory element-binding transcription factor 1 (SREBP1) gene. SETD2 activation in cHFpEF led to SREBP1 upregulation, myocardial triglyceride accumulation and lipotoxic damage. In cHFpEF mice, cardiomyocyte-specific deletion of SETD2 prevented hypertrophic remodeling, diastolic dysfunction and lung congestion while improving exercise tolerance. Mechanistically, SETD2 deletion blunted H3K36me3 enrichment on SREBP1 promoter thus preventing SREBP1-driven lipid accumulation and leading to a significant rewiring of the cardiac lipidome. These findings were associated with restoration of autophagic flux in the cHFpEF myocardium. In CMs exposed to palmitic acid, SETD2 depletion prevented SREBP1 upregulation, whereas SETD2 overexpression recapitulated lipotoxic damage. Finally, SETD2 was upregulated in LV myocardial samples from cHFpEF patients and its pharmacological inhibition attenuated CM stiffness.

Conclusions
SETD2 is a new molecular target implicated in the pathophysiology of cHFpEF.
Macrophage-mediated interleukin-6 signaling drives ryanodine receptor-2 calcium leak in postoperative atrial fibrillation
Authors: Wehrens X , Keefe J A , Aguilar-Sanchez Y , Ong I , Navarro-Garcia J A , Paasche A , Abu-Taha I , Tekook M , Bruns F , Barazi D , Kamler M , Shen H Y , Dobrev D 
Published: October 2024

Abstract

Background
Postoperative atrial fibrillation (poAF) is self-limited AF that occurs within days after cardiac surgery in one-third of patients. Clinical and preclinical studies have demonstrated that the magnitude of the perioperative increase in systemic inflammation, in particular mediated by interleukin (IL)-6, correlates with poAF risk. However, no studies to-date have mechanistically linked IL-6 signaling to fundamental arrhythmia mechanisms or identified the specific cell types driving postoperative atrial IL-6 signaling.

Methods
We performed single-cell RNA sequencing (scRNAseq), followed by pseudotime trajectory and cell-cell communication analyses on atrial non-myocytes comparing mice with and without poAF. We followed up our scRNAseq findings with pharmacologic and genetic approaches in mice to validate pathways related to macrophage-mediated IL-6 signaling. We used confocal imaging to assess calcium-signaling mechanisms at the single atrial cardiomyocyte (ACM) level and performed parallel patch-clamp studies in isolated human ACMs as well as biochemical analyses of human atrial tissue to assess the translational relevance of our findings.

Results
Our scRNAseq results demonstrated macrophages to be the most prominently altered cell type in the atria of mice with poAF. Pseudotime trajectory analyses revealed IL-6 to be one of the top inflammatory pathways implicated in macrophage transcriptional state. Indeed, both macrophage depletion and conditional knockout of IL-6 receptors in macrophages were sufficient to prevent poAF. We found that inhibition of STAT3, which is downstream of the IL-6Ra, with FDA-approved phospho-STAT3 inhibitor TTI-101 prevented poAF in mice. Lastly, we demonstrate that enhanced STAT3 activity in poAF promotes arrhythmogenic Ca2+ sparks and waves through ryanodine receptor-2 dysfunction, and that CaMKII inhibition is sufficient to ameliorate Ca2+ mishandling at the single atrial myocyte level.

Conclusions
Taken together, we use an integrated approach incorporating mouse and human biochemical, functional, and single-cell sequencing data to demonstrate that infiltrating atrial macrophages are fundamentally required for poAF. IL-6 was found to be a critical pathway upregulated in poAF leading to downstream ryanodine receptor-2 dysfunction and atrial arrhythmogenesis. Our findings portend significant therapeutic utility by providing robust mechanistic evidence that targeting the IL-6 axis may be used for poAF prevention and treatment in a clinically amenable timeframe.
Calcitonin signalling system regulates function and arhythmogenicity of atrial cardiomyocytes
Authors: Moreira L , Robinson P , Sparrow A J , Mehta N , Agon K A , Steeples V , Akoumianakis I , Sayeed R , Krasopoulos G , Watkins H , Topfer C , Antoniades C , Nattel S , Redwood C , Reilly S 
Published: October 2024

Abstract

Background
Atrial fibrillation (AF) poses a significant therapeutic challenge due to myocardial remodelling, involving both structural and electrical alterations. Recent investigations have shed light on the role of atrial cardiomyocytes (CMs) in secreting Calcitonin (CT), a factor crucial for maintaining atrial tissue integrity. Dysregulated CT secretion in AF showed to contribute to fibrotic tissue production by atrial fibroblasts, exacerbating arrhythmogenesis [1]. However, the direct impact of CT on CM function and arrhythmogenicity remains unclear, driving the objectives of our study.

Methods/Results
Serum samples from 20 cardiac surgery patients revealed a noteworthy association between higher pre-operative CT levels and a significant ~2.8-fold reduction in the incidence of post-operative AF (poAF).
Using freshly isolated atrial guinea pig CMs, confirmed (by qPCR and immunofluorescence) that CMs express CT-receptor (CTR) to enable CT actions in the cell. Functional studies found that CT administration inhibits spontaneous calcium (Ca2+)-release events induced by pacing and decreases the Ca2+ transients amplitude (at 2 Hz; IonOptix μstep system) in fura2-loaded CMs (n=22 cells) in a concentration-dependent manner. Atrial iPSC-CMs transduced with global RGECO sensor (Genetically encoded Ca2+ indicator) and treated with 15 pM CT showed a reduction in the beat rate when paced at 2Hz, and a significantly increased the time to 50% baseline.
Evaluation of the expression and phosphorylation of selected Ca2+ handling proteins, which may potentially account for the observed changes in Ca2+ transients, showed no differences in total or phospho-(ser2808) ryanodine receptor, and SERCA2α in response to CT but an increase in phospho-(Ser16) Phospholamban.

Conclusion
Our findings highlight the effects of CT on atrial CM function. Maintaining physiological CT levels offer a promising approach for managing AF clinically, potentially through the use of already in clinical use CT-analogues.
Reduced Na current in dystrophin-deficient ventricular cardiomyocytes is rescued by tenascin-C inhibition
Authors: Marksteiner J , Sauer J , Koenig X , Todt H , Dostal C , Szabo P L , Podesser B K , Kiss A , Hilber K 
Published: October 2024

Abstract

Background
Duchenne muscular dystrophy (DMD) is an X-linked hereditary disease triggered by the deficiency of the structural protein dystrophin, which leads to muscular degeneration mainly affecting young males. Major contributors to early death in DMD patients are cardiac arrhythmias and dystrophic cardiomyopathy. One cause for arrhythmias is impaired ventricular impulse conduction, which leads to ventricular asynchrony and reentrant mechanisms. We recently showed that the disruption of dystrophin results in a significant reduction of Na current in ventricular cardiomyocytes (vCMs) of the dystrophin-deficient mdx mouse model for human DMD. Na current reduction provides a mechanistic explanation for the impaired ventricular conduction and accompanying arrhythmias in the dystrophic heart.
The extracellular matrix protein tenascin-C (TN-C) is a significant remodeling factor in the injured and diseased heart and is strongly upregulated in dystrophic cardiomyopathy. To this date, it is unknown how the upregulation of TN-C in DMD patients affects dystrophic cardiomyopathy.

Purpose
In this study, we examined the effect of TN-C inhibition on diminished Na currents in dystrophin-deficient vCMs.

Methods
We compared four different mouse genotypes with each other, namely wild-type, dystrophin-deficient mdx, TN-C-deficient and dystrophin- plus TN-C-deficient mice. Furthermore, a cohort of mdx mice was injected with TN-C siRNA twice a week for 9 weeks to investigate the effect of TN-C knockdown. Hearts from adult male mice were enzymatically digested using a Langendorff system to isolate single vCMs. Na currents were then measured with the whole cell patch clamp technique.

Results
Na current densities were increased in TN-C deficient vCMs compared to wild-type vCMs. Accordingly, 24-hour incubation of wild-type vCMs with human recombinant TN-C resulted in a significant decrease in Na current. Na currents of vCMs from mdx mice were reduced, but restored to the wild-type level in vCMs from TN-C-deficient mdx mice. Moreover, vCMs of TN-C siRNA-treated mdx mice had significantly increased Na currents compared to control mdx vCMs.

Conclusion
Upregulation of TN-C in dystrophin-deficient vCMs reduces Na currents, whereas inhibition of TN-C prevents this reduction. Therefore, inhibition of TN-C in DMD patients may be considered as a potential new therapeutic strategy to improve ventricular conduction and reduce arrhythmia vulnerability.
Local ventricular activation at the distal great cardiac vein determines right- and left-sided approach for catheter ablation of outflow tract arrhythmias: a simple and rapid discriminator
Authors: Miyoshi M , Hasegawa K , Tsuji T , Nomura R , Mukai M , Tada H 
Published: October 2024

Abstract

Background
When the precordial transition zone (TZ) of idiopathic outflow tract arrhythmias (OTAs) is present around lead V3, it may be difficult to precisely determine which outflow tract is responsible for the origin of the OTAs from the ECG characteristics.

Purpose
We hypothesized that mapping around the distal portion of the great cardiac vein (dGCV) would be useful for identifying which outflow tract is the origin of OTAs during radiofrequency catheter ablation (RFA).

Methods
Among 28 OTA patients who underwent dGCV mapping and successful RFA at our institution from June 2021 to February 2024, 16 whose TZ during the OTAs was ＞lead V2 and ＜lead V4 were included in this study. In all patients, activation mapping around the dGCV with the novel 2.7 Fr over-the-wire (OTW)-type decapolar catheter was performed during the OTAs.

Results
In all patients, the mapping catheter could be easily placed in the dGCV. In patients whose OTAs were successfully ablated from the left-sided OT (n=7), the local ventricular activation time in the dGCV during OTAs preceded the QRS onset (LAT-dGCV) by -26.1±7.0 msec, which was significantly earlier than that of OTAs successfully ablated from the right-sided OT (n=9; -4.0±5.7 msec; p&lt;0.001). An LAT-dGCV &gt;-18 msec indicated a left-sided OTA, and right-sided and left-sided OTAs were completely distinct. Patients with an LAT-dGCV &gt;-18 msec and mapping initiated first in the left-sided OT had shorter procedure times than those with mapping initiated first in the right-sided OT (p&lt;0.001).

Conclusions
Mapping the dGCV with this OTW-type catheter is easy and safe. The earliness of the local ventricular activation in the dGCV during OTAs could easily and precisely differentiate between right-sided and left-sided OTAs, resulting in a successful ablation with a shorter procedure time.
Anatomical characteristics of the phrenic nerve and the spontaneous conduction block between the right atrium and the superior vena cava
Authors: Hojo R , Miura M , Suzuki M , Komine S , Sunagwa M , Tsuno W , Sasaki T , Kujiraoka H , Yamaoka K , Arai T , Yoshida K , Takahashi M , Tuchiyama T , Fukamizu S 
Published: October 2024

Abstract

Introduction
Although the superior vena cava isolation (SVCI) with minimal radiofrequency application using a spontaneous right atrium – superior vena cava (RA-SVC) conduction block has been reported, the anatomical characteristics of the spontaneous RA-SVC conduction block is not clear.

Purpose
The aim of this study to evaluate the anatomical relationship between the spontaneous RA-SVC conduction block and the phrenic nerve (PN).

Methods
This study consisted of 73 patients who attempted to undergo SVCI using a RA-SVC conduction block. The RA-SVC conduction block was visualized using the extended early meets late tool with the CARTO3 system. We set the first lower threshold at 1800/total local activation time to optimize the visualization of spontaneous RA-SVC conduction block. If the SVC was not isolated by ablation to the gap of the visualized conduction block line, the lower threshold was increased by 5%, and the new gap was ablated each time. The course of the right PN was detected by pacing with 20 mA /2 ms. The RA-SVC conduction block and the course of the PN were measured with reference to the height of the left atrial roof. The extend of the RA-SVC conduction block and PN were measured in angles with respect to the ventral side (Figure 1). These anatomical parameters were compared between the RA-SVC block line and the PN.

Results
Sixty-one patients (83.6%) had spontaneous RA-SVC conduction block, and the remaining 12 patients (16.4%) did not. Anatomical characteristics were evaluated in 61 patients with spontaneous RA-SVC conduction block. Compared with the course of the PN, RA-SVC conduction block extended more posteriorly (110 degrees vs 128 degrees, P = 0.013) and more caudally (9.5 mm vs 16.1 mm, P&lt;0.0001) (Figure 2). In the patients who underwent SVCI using a RA-SVC conduction block, any patients did not undergo radiofrequency application on the course of the PN.

Conclusion
Since the caudal end of the RA-SVC conduction block is posterior to the caudal end of the phrenic nerve, SVCI using the RA-SVC conduction block may be able to avoid ablation near the PN.Figure1Figure2
Role of vitamin K2 and vitamin K cycle enzymes in aortic valvular interstitial cell calcification
Authors: Repges E , Al Zaidi M , Yousif A , Czogalla-Nitsche K , Oldenburg J , Tiyerili V , Nickenig G , Zimmer S , Aksoy A 
Published: October 2024

Abstract

Introduction
Calcific aortic valve disease (CAVD) is the most common valve disease. Currently, there is no medical treatment available for CAVD. Vitamin K antagonists promote CAVD while population-based studies suggest that dietary intake of vitamin K reduces the incidence of CAVD in adults. However, randomized trials have so far not proven a clear benefit of vitamin K supplementation on the progression of AVS. Consequently, there is a need for a deeper understanding of the role of vitamin K in valvular calcification.
This study aims to further investigate mechanisms of action of vitamin K during valvular calcification.

Methods and Results
Aortic valve samples were obtained from patients undergoing surgical aortic valve replacement for CAVD and valvular interstitial cells (VIC) were isolated by collagenase II digestion (Fig. 1). VIC expressed typical markers like Vimentin and α-SMA and were cultured in a control medium (CM) or further calcified in a pro-calcifying medium (PCM) containing sodium dihydrogen phosphate and ascorbic acid. PCM led to upregulation of Runt-related transcription factor 2 (RUNX2), alkaline phosphatase (ALP) expression, and ALP-activity after 7 and 21 days of culture. Moreover, alizarin red staining visualized significant calcium mineral deposition after 21 days of culture (Fig. 2).
The addition of the most potent vitamin K2 derivative (Menaquinone-7, MK-7) improved cell viability under both control and calcifying conditions (Fig. 3). Moreover, MK-7 protected VIC from ferroptotic cell death (Fig. 4) and increased expression of the vitamin K-dependent Matrix-Gla-protein (MGP), a major inhibitor of ectopic calcification (Fig. 5).
To fulfill its function as an activator of vitamin K-dependent proteins like MGP, vitamin K needs to be reduced to vitamin K hydroquinone by the vitamin K epoxide reductase enzymes VKORC1 and VKORC1L1. In VIC, using our calcification protocol, treatment with PCM led to the downregulation of VKORC1, but not of VKORC1L1, an enzyme with known anti-oxidative properties (Fig. 6). We next performed siRNA-mediated knockdown of VKORC1 and VKORC1L1 in VIC and observed calcification after 7 and 21 days of culture by measuring expression of ALP, RUNX2, quantifying ALP activity, and staining for calcium minerals (alizarin red). Intriguingly, VKORC1L1-knockdown sharply increased the expression of ALP.
To further elucidate these findings, we will perform overexpression experiments to analyze, if VKORC1L1 can alleviate PCM-induced calcification
Conclusion: Vitamin K2 inhibits in vitro calcification of valvular interstitial cells and upregulates the calcification inhibitor Matrix-Gla-Protein. Our results suggest the involvement of the vitamin K cycle enzyme VKORC1L1, which is known to exhibit anti-oxidative and cytoprotective effects. Further studies are warranted to shed light on the regulation of the enzymes to improve our understanding.