tbuckley/cabot-search huggingface dataset:
Abstract Tu102: The Role of the β <sub>IV</sub> -spectrin/STAT3 Complex in Regulating Ischemic Cardiac Remodeling
Authors: Rebecca Shaheen, Drew Nassal, Riece Rivera, Simon Lococo, Xianyao xu, Thomas Hund
Journal: Circulation Research (2024)

Adverse fibrotic remodeling contributes to high morbidity and mortality in patients following myocardial infarction (MI). The healing process after MI requires necrotic tissue to be cleared and replaced with fibrosis, which is driven by the coordinated effort of several distinct cardiac cell populations, including macrophages and cardiac fibroblasts (CFs). While previous studies have focused on identifying the stimuli that drives fibrotic remodeling in the infarcted myocardium, the contribution of specific cell populations to the signaling cascade and the manner of how these communication networks are tuned in response to chronic stress remains unclear. Prior work has identified a role for the cytoskeletal protein, β IV -spectrin, in coordinating the activity of the transcription factor, STAT3, with implications for CF activation and profibrotic signaling. Specifically, it was found that mice expressing truncated β IV -spectrin ( qv 3J ) are resistant to cardiac fibrosis in the setting of chronic pressure overload, with maintained β IV -spectrin expression and STAT3 localization/activity in CFs. Further, β IV -spectrin deficiency causes increased secretion of profibrotic and proinflammatory factors, including matrix metallopeptidases (MMPs). Therefore, we hypothesized that stress-induced loss of β IV -spectrin and subsequent dysregulation of STAT3 signaling in CFs proximal to the infarct promotes fibroblast activation, an important first step in repairing the infarct region. In this study, we subjected WT and qv 3J mice to permanent ligation of the left anterior descending artery and assessed cardiac function and survival through 28 days. A subset of mice were sacrificed at 7 days for histology, qPCR, and flow cytometry. Compared to WT, qv 3J mice showed a significant decrease in 28-day survival with increased mortality in the first week post-MI. Autopsy identified increased incidence of cardiac rupture in qv 3J animals. Immunohistochemistry revealed impaired scar formation at 7 days post-MI in qv 3J compared to WT. Quantitative PCR showed altered expression of matrix metallopeptidases (MMPs 3, 8, 9, and 14) in the qv 3J hearts at day 7. MMP activity was assessed in whole heart lysates using gelatin-zymography. Collagen uptake was assessed in CFs and bone marrow-derived macrophages isolated from WT and qv 3J mice. Our work identifies a novel role of the spectrin-based pathway in facilitating fibrotic remodeling in response to ischemic stress.
Abstract We059: Age-associated Alterations in T cell Output and Functions
Authors: Daria Konovalova, Danielle Shane, Megan Mabito, Sarah Yuan, Yonggang Ma
Journal: Circulation Research (2024)

The elderly have a higher risk for a wide range of diseases, including infection, tumor, and cardiovascular disease. This could be, at least partially, attributed to T lymphocyte changes during aging. The goal of this project was to characterize age-related changes in T cell output and functions. In this study, young (3-6 months old) and aged (18-24 months old) male and female C57BL/6J mice were utilized. Our data showed that compared to young mice, aged mice demonstrated significantly smaller thymus and fewer developing thymocytes, including double negative CD4 - CD8 - , double positive CD4 + CD8 + , as well as single positive CD4 + and CD8 + thymocytes, which implies that aged mice generate less T cells. Accordingly, circulating T cell count was significantly lower in aged mice than young controls. To investigate how aging affects T cell functions, we isolated splenic T cells and stimulated them with PMA (100 nM) + ionomycin (1 µM) (P+I) or vehicle for 4 hours. At the steady state, aged T cells expressed higher levels of Ifng , Tnfα , granzyme b , and perforin than young T cells, suggesting that aged T cells show a senescence-associated secretory phenotype (SASP). After stimulation with P+I, both young and aged T cells expressed dramatically higher levels of Ifng , Tnfα , Il2 , Il4 , Il17 , and granzyme b , indicative of T cell activation. Interestingly, aged T cells had higher expression of Ifng, Il17, and granzyme b, but lower Tnfα and Il2 levels. Moreover, aged T cells expressed higher levels of exhaustion markers, such as Pd1 , Ctla4 , Lag3 , and Tigit , indicating that aged T cells exhibit an exhaustion phenotype. In conclusion, our study demonstrates that aged mice show smaller thymus and fewer thymocytes and blood T cells than young mice. In addition, aged T cells exhibit a SASP and exhaustion phenotype. Upon activation, aged T cells might be more cytotoxic by secreting higher levels of IFN-γ, IL-17, and granzyme B.
Abstract Mo043: Advanced waveform analysis of the electrocardiogram signals using complementary signal processing techniques to investigate the response to a QTc prolonging drug vs control including food effect.
Authors: Miquel Serna Pascual, Manasi Nandi, Jorg Taubel, Ulrike Lorch, Dilshat Djumanov, Tyrone-Joshua Sadsad, Elisa Mejia, James Rickard
Journal: Circulation Research (2024)

Background: Thorough QT studies using Electrocardiogram data, are a well-established method for testing the pro-arrhythmic propensity of drugs performed during drug development. ECG analysis is currently reduced to simplified biomarkers, such as rate, intervals and amplitudes. However, ECG waveforms are complex and generally sampled with high fidelity 125-1000 Hz. Our novel mathematical method, Symmetric Projection Attractor Reconstruction analyses the morphology and variability of such waveforms, using every data point to generate a new, faithful 2D waveform representation termed an attractor. Moxifloxacin know QT prolonging medicine and has been shown to cause a mean increase of the QTc interval of 10–14 mS after a single dose of 400 mg. Separately, studies have shown that meals can alter QT interval as well as altering the pharmacokinetic profile of moxifloxacin itself with gender and ethnicity impacting individual responses. In-depth knowledge of these physiological factors could support safer medicines development and clinical use. Purpose: This project investigated the feasibility of SPAR analysis of ECG signals to detect drug induced changes which a higher degree of sensitivity, to support safety evaluation during medicines development Methods: High resolution triplicate 12 lead ECG time-series data from a Phase one study of healthy human volunteers cross over of placebo, moxifloxacin or moxifloxacin + food was retrospectively analysed using SPAR at 0,1 and 6 hours. MATLAB bespoke software tool was used to perform SPAR analyses to transform ECG time-series into corresponding attractors. Corresponding single point measurements were previously obtained as part of the original Phase one study. Results: Initial evaluation of attractors revealed high inter-individual variation, consistent with previous SPAR ECG analysis. Nevertheless, we identified changes in subjects receiving Moxifloxacin +/- food vs placebo control. These changes were not as evident in previously obtained QT intervals. Conclusion: This pilot study illustrates that SPAR is highlighting changes on the ECG in fasted and fed states that are less obvious from QT data alone. Further evaluation of the whole dataset to identify generalisable SPAR features, and their comparison with existing markers is now necessary. The individualised nature of ECGs and corresponding attractors indicates the method may have highest utility in personalised medicine.
Abstract Mo053: Acacetin's Antiarrhythmic Potential in Human-Induced Pluripotent Stem Cell-Derived Cardiomyocytes Harboring Hypertrophic and Dilated Cardiomyopathy-Related Mutations
Authors: mena abdelsayed, Mark Mercola, Charles Antzelevitch
Journal: Circulation Research (2024)

Background: Hypertrophic cardiomyopathy (HCM) is often caused by mutations such as p.R943X in the Myosin Binding Protein C3 (MYBPC3), leading to early and delayed afterdepolarizations, myofibrillar disarray, and calcium dysfunction, which may induce lethal arrhythmias. Dilated cardiomyopathy (DCM) can also result from mutations, such as the p.R14del mutation in the phospholamban (PLN) protein, which is crucial for calcium signaling regulation, leading to arrhythmogenesis when provoked. This study explores the arrhythmogenic potential in human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) carrying the HCM MYBPC3 p.R943X mutation and the DCM PLN p.R14del mutation. Methods: We utilized a 384-well optical physiological system to record action potentials (APs) in hiPSC-CMs carrying the MYBPC3 p.R943X mutation and the DCM PLN p.R14del mutation, including their isogenic controls. Action potential metrics were measured under spontaneous and electrically paced conditions. The effects of Acacetin, NS-5806, nifedipine, and GS-967 on the recorded AP types were analyzed to understand the underlying channelopathies and arrhythmogenic potential. Special attention was given to the variability between the HCM MYBPC3 p.R943X and DCM PLN p.R14del cell lines' susceptibility to arrhythmogenesis and their isogenic controls. Results: The HCM MYBPC3 p.R943X hiPSC-CMs exhibited a significant increase in early afterdepolarizations, non-sustained and sustained ventricular tachycardia, and AP notches compared to their isogenic control. AP notches and arrhythmogenic events were notably provoked by NS-5806 in both the HCM MYBPC3 p.R943X and DCM PLN p.R14del hiPSC-CMs. However, these were significantly ameliorated (p&lt;0.05) by Acacetin administration (5 µM), highlighting its potential as an effective antiarrhythmic in managing both HCM- and DCM-induced arrhythmias. GS-967 also showed efficacy in reducing early afterdepolarizations (EADs) in the HCM model. Conclusions: This study provides novel insights into the arrhythmogenic potential of hiPSC-CMs carrying MYBPC3 p.R943X and PLN p.R14del mutations, underscoring the significant role of Acacetin in attenuating these effects. It paves the way for developing targeted therapies that address the complex molecular mechanisms underlying arrhythmogenesis in cardiomyopathies. The findings suggest that Acacetin could be a promising candidate for the pharmacologic treatment of cardiomyopathies characterized by arrhythmogenic risks.
Abstract We069: Post-infarction Cardiac Function is Improved in Mice with TSC2 <sup>-/-</sup> Macrophages
Authors: Mohammad Keykhaei, Navid Koleini, Mariam Meddeb, Masih Tajdini, Kejun Liu, David Kass
Journal: Circulation Research (2024)

Introduction: Macrophages (MF) play major roles in myocardial ischemia/reperfusion (I/R) injury, both beneficial and detrimental. The mechanistic target of rapamycin (mTOR) plays an important role in MF polarization and functionality. It is prominently regulated by tuberous sclerosis complex 2 (TSC2) which constitutively inhibits and regulates mTORC1. Little is known about how such mTORC1 regulation influences the effect of MFs in I/R injured hearts. Hypothesis: We tested if gene knockdown of TSC2 to constitutively enhance MF mTORC1 activity by TSC2 knockdown impairs or benefits the I/R heart. Methods/Results: MF-specific TSC2 knock-out mice (MF TSC2-/- ) were generated by crossing flox’d TSC2 mice with those expressing LysM-Cre. MTORC1 was constitutively active in bone marrow-derived MF TSC2-/- , reflected by increased S6K1 and 4E-BP1 phosphorylation. MF TSC2-/- exposed to liposaccharide had greater proinflammatory responses, e.g. increased TNF-a secretion, supporting an M1-like phenotype. MF TSC2-/- also exhibited less M2-like features (reduced Arg1, Mrc1, and Rentla expression). To test the impact of MF TSC2-/- on infiltrating myocardial MF subtypes post I/R, MF were isolated from the myocardium and sorted by flow-cytometry based on CD45 + , CD11b + , and CD64 + and then parsed as ±CCR2 and ±MHC-II. We found MF TSC2-/- resulted in an increase in infiltrating CCR2 - MHC-II - phenotypes, which are thought to be anti-inflammatory and to support healing. Consistent with this, we found MF TSC2-/- hearts exposed to I/R had higher ejection fractions (74.2±10.3%) vs controls (47.2±14.3%, P=0.002). MF TSC2-/- hearts also had smaller LV internal end-systolic diameter (P=0.009). As LysM is also expressed in neutrophils, we also performed this study in mice where neutrophils were first depleted using an anti-Ly6G antibody. Similar cardioprotective effects were observed with MF TSC2-/- after I/R: (EF: 56.9±12.3 vs 36.1±9.8, P=0.01). This supports the impact being conferred by MF. Conclusion: TSC2-deleted MF with constitutive mTORC1 activation confer cardio-protection to I/R injury. These findings help identify a novel signaling mechanism coupling mTORC1/TSC2 in MF to myocyte recovery, highlight novel avenues to improve post ischemic cardiac repair.
Abstract We046: Building Mass or Strength: Stage-specific Effects of Insulin and Wnt on Cell Fate Decisions in Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes
Authors: Qianliang Yuan, Eric Schoger, Rosa Kim, Diederik Kuster, Reinier Boon, Laura Zelarayan, Jolanda van der Velden, Jan Buikema
Journal: Circulation Research (2024)

Background: Reactivation of the so-called fetal gene programs and pathways have been reported in failing hearts, however, it remains unclear whether this phenomenon is beneficial or detrimental to the remaining functional myocardium. During cardiac development, the orchestration of these embryonic growth pathways, facilitate temporal and stage-specific cell fate decisions such as required for specification and growth of the various myocardial compartments. Previously, we demonstrated that molecular activation of the Wnt pathway resulted in massive expansion of immature human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). Yet, it is unknown what exact cues guide the cell fate decisions of immature hiPSC-CMs to either proliferate or terminally differentiate into more mature cardiomyocytes. Purpose: This work uncovers the embryonic growth pathways that control the cues for proliferation versus terminal differentiation in functional immature hiPSC-CMs. Methods: We utilised spontaneously beating hiPSC-CMs at day 11 of differentiation and performed a combinatory screen for various dosages of CHIR99021/Wnt and Insulin/Akt pathway. Proliferation was determined by quantification of cell number and the proportion of Ki67 positive hiPSC-CMs. Terminal differentiation was evaluated by presence of more mature sarcomere markers and cell cycle exit. Results: Our combinatory screen for Insulin/Akt and CHIR99021/Wnt demonstrates synergistic effects on proliferation of immature hiPSC-CMs, whereas the absence of these pathway activators leads to rapid cell cycle exit and terminal differentiation of hiPSC-CMs. Detailed characterization reveals that CHIR99021/Wnt also importantly regulates sarcomere homeostasis and architecture in hiPSC-CMs. Moreover, we identify a novel temporal interplay between CHIR99021/Wnt via TCF and Insulin/Akt via FOXO as regulators of cell-fate decision in immature hiPSC-CMs. Conclusions: Molecular targeting of the embryonic growth pathways in acute and chronic forms of heart failure requires a detailed understanding of the specific effects on cardiomyocyte function and sarcomere architecture. This work provides a starting point to develop future strategies to target acute and chronic forms of heart failure via modulation of embryonic growth pathways.
Abstract Mo068: The role of FGF13 in modulating gap junction protein Connexin-43
Authors: LALA TANMOY DAS, Mattia Malvezzi, Aravind Gade, Maiko Matsui, Steven Marx, Geoffrey Pitt
Journal: Circulation Research (2024)

Background: Fibroblast growth factor homologous factors (FHFs) are associated with arrhythmias like Brugada syndrome and atrial fibrillation, but their pathological mechanisms remain poorly understood. FHFs are best characterized as regulators of voltage gated sodium channels (VGSCs), however recent studies suggest broader, non-VGSC-related functions, including regulation of microtubules. Whether and how non-VGSC regulatory functions modulate cardiac rhythm is not known. Hypothesis: FGF13 regulates Cx43 trafficking and expression in ventricular cardiomyocytes via destabilizing microtubules. Aims: Building on an unbiased proteomic screen, we investigated if FGF13, the predominant FHF in rodent heart, affects the expression and trafficking of Connexin-43 (Cx43), the predominant gap junction protein in ventricular myocytes. Methods: To identify additional FGF13-dependent functional roles, we employed proximity labeling proteomics in mouse heart with the TurboID biotin ligase fused to FGF13. We used immunoblots, immunohistochemistry, and immunocytochemistry to further characterize the effects of FGF13 ablation on Cx43 pattern distribution and expression. We also leveraged electrophysiology techniques using gap junction inhibitors to detect any Cx43-dependent functional changes in FGF13-ablated cardiomyocytes. Results: The proteomic data revealed that cell junction proteins associated with the intercalated disc (ID) were among the top FGF13 near neighbors, of which Cx43 was heavily enriched, together with microtubule associated proteins (MAPs) known to be critical for cardiomyocyte function and ion channel trafficking. In ventricular cardiomyocytes from constitutive cardiomyocyte-restricted Fgf13 knockout mice, we found markedly perturbed trafficking of Cx43 and reduced colocalization with the ID marker N-Cadherin. Separately, MAP4 abundance was markedly reduced. The addition of colchicine, a microtubule destabilizing drug, to WT cells altered Cx43 distribution pattern similar to that observed in FGF13-ablated cardiomyocytes. Re-expression of FGF13 restored Cx43 trafficking and ID targeting. Electrophysiology experiments using a Cx43 hemichannel inhibitor, Gap19, showed a perturbation of the action potential duration in knockout cardiomyocytes. Isoproterenol-induced action potential prolongation in knockout myocytes was decreased by the addition of Gap19. Conclusions: FGF13 regulates microtubule-based trafficking and targeting of Cx43.
Abstract Mo055: CHD4 Interacts With TBX5 to Maintain the Gene Regulatory Network of Postnatal Atrial Cardiomyocytes
Authors: Mason Sweat, Wei Shi, Erin Keating, Anna Ponek, Frank Conlon, William Pu
Journal: Circulation Research (2024)

Atrial fibrillation (AF) is the most common sustained arrhythmia in humans, leading to increased mortality due to increased incidence of stroke and heart failure. Over 200 genes are associated with AF by GWAS studies, suggesting a nuanced gene regulatory network (GRN) is required to maintain atrial cardiomyocyte (aCM) function and rhythm. Among these genes is the transcription factor TBX5, which we and others have shown is a master regulator of aCM identity that is essential for atrial rhythm homeostasis. We showed that TBX5 is required to maintain the chromatin looping, accessibility, and activity of atrial enhancers. Chromodomain helicase DNA binding protein 4 (CHD4), a chromatin remodeling protein that interacts with TBX5, is canonically thought to repress transcription as a component of the NuRD complex. Here, we investigated the contribution of CHD4 to TBX5 regulation of aCM gene expression. Methods: We inactivated CHD4 specifically within atrial cardiomyocytes using Cre recombinase driven by the aCM-specific Nppa promoter delivered postnatally with AAV9. Atrial remodeling, transcriptomic changes and AF susceptibility were examined. Results: We show that inactivating CHD4 in postnatal aCMs resulted in fibrotic atrial remodeling, spontaneous AF in a subset of mice, and increased AF susceptibility and burden after electrical pacing. Transcriptomic profiling of CHD4 aCM KO atria revealed gene expression changes that were highly correlated to altered gene expression downstream of TBX5 inactivation. Mechanistically, we show TBX5 recruits CHD4 to 33,170 genomic regions that are important for aCM gene regulation, whose expression is concordantly regulated downstream of TBX5 and CHD4. Together, these data reveal that CHD4 is required by TBX5 to promote accessibility of enhancers and activate many TBX5 target genes to maintain atrial rhythm.
Abstract We074: Macrophages Endocytose the Extracellular Matrix Component Hyaluronan
Authors: Caitlin Howard, Emma Pendergraft, Sarah Belcher, Steven Jones
Journal: Circulation Research (2024)

Background: Following myocardial infarction, macrophages clear cellular debris during remodeling of the extracellular matrix (ECM). The presence of macrophages coincides with a significant increase in the ECM component hyaluronan (HA). HA is produced in copious amounts following injury, such as myocardial infarction, and HA may interfere with myocardial wound healing. Because macrophages express hyaluronan receptors and are known to facilitate ECM remodeling, it is possible that macrophages remove HA early after MI. The extent to which macrophages clear HA is not known. Goal: To determine the extent to which macrophages endocytose hyaluronan (HA). Methods and Results: Bone marrow derived macrophages (BMDMs) were polarized into a pro-inflammatory (M1) phenotype using LPS and INF-g, or pro-reparative phenotype (M2) using IL-4 and IL-13. In addition to the polarization factors, cells were treated with 5,000 ng/ml of a fluorescein-labeled HA or a vehicle for 24 hours. At the time of collection, cells were stained with trypan blue to quench surface fluorescence and flow cytometry was used to measure the uptake of labeled HA. An increase in cellular fluorescence intensity after HA treatment indicates the extent of endocytosis of HA. Mean fluorescence intensity (MFI) values were recorded and used to calculate the change in fluorescence between the treated and control groups (DMFI). A significant increase in DMFI was observed when both M1 and M2 macrophages were compared to naïve (M0) controls. Conclusion: Macrophages endocytose HA, and polarized macrophages endocytose HA at a greater level than naïve macrophages. Hence, polarized macrophages may play a role in clearing HA in the heart following injury. We speculate that enhancement of macrophage-mediated clearance of HA may improve acute scar formation following myocardial infarction.