tbuckley/cabot-search huggingface dataset:
Abstract We024: Spatial Transcriptomics Identifies a Regeneration-Permissive Microenvironment in the Neonatal Mammalian Heart
Authors: Saradha Miriyala, Miao Cui
Journal: Circulation Research (2024)

Ischemic heart disease is the leading cause of death globally, largely driven by inability of the adult heart to restore tissue structure and function after injury. However, the neonatal mouse heart is able to regenerate up to one week after birth, circumventing scarring and functional impairment. Neonatal heart regeneration is a spatially and temporally regulated process, involving coordinated communication of different cardiac cell types. Our previous work identified a regenerative cardiomyocyte population (CM4) that proliferates after myocardial infarction (MI), but the intercellular communication that induces their regenerative response is not fully understood. To study the cellular environment of CM4 cells during neonatal heart regeneration, we profiled spatial transcriptomes of regenerative P1 hearts at 3 days and 7 days after MI and compared them to nonregenerative P8 hearts. We identified unique spatial regions with distinct gene expression signatures, that we refer to as “molecular niches”, in the ischemic and border zones (IZ, BZ) of the P1 heart post-MI compared to P8 hearts. Cell type deconvolution of molecular niches showed a distinct temporal change of fibroblast and macrophage abundance in the IZ of P1 hearts compared to P8 hearts and also showed the localization of CM4 cells to the BZ of P1 hearts at 7 days post-MI. To identify intercellular communication that contributes to the differential injury response in P1 and P8 hearts, we analyzed ligand-receptor pairs that were expressed at higher levels in the IZ and BZ of P1 compared to P8 hearts. Among the nearly 50 signaling pairs identified, OSM and SLIT signaling have been previously implicated in heart regeneration. Notably, many of these signaling factors, including cytokines, chemokines and growth factors, have receptors expressed in multiple cardiac cell types. Thus, ongoing studies are systematically distilling the effect of each secreted factor on individual cell types in the heart using a cardiac cell co-culture and multiplexed single-cell RNA sequencing approach. In summary, our study provides insight into the spatial organization and tissue microenvironment of neonatal heart regeneration and identifies a number of candidate signaling pathways that potentially mediate critical intercellular communication during neonatal heart regeneration.
Abstract We020: <i>Myh9</i> plays a vital role in cardiac myofibroblast differentiation and is indispensable for cardiac repair after myocardial infarction
Authors: Leshan Wang, Yuxia Li, Qianglin Liu, Xujia Zhang, Robert Adelstein, Xing Fu
Journal: Circulation Research (2024)

After myocardial infarction (MI), quiescent cardiac fibroblasts (CFs) are activated and differentiate into myofibroblasts featured by elevated expression of smooth muscle alpha-actin (SMαA, encoded by Acta2 ), which form contractile stress fibers. However, compared to the matrix formation function of cardiac myofibroblasts, much less is known about the role of their contraction in post-MI cardiac repair. In our previous study using mice lacking Acta2 in CFs, all other 5 actin isoforms were activated to compensate for the loss of Acta2 , suggesting the low feasibility of abolishing cardiac myofibroblast contraction through deleting actin genes. An alternative strategy through targeting myosin was explored. Our transcriptomic study identified Myh9 and Myh10 [encoding non-muscle myosin IIA (NM IIA) and NM IIB, respectively] as the dominant myosin isoforms in cardiac myofibroblasts. In vitro studies found that Myh9 knockout (KO) but not Myh10 KO significantly affected cardiac myofibroblast morphology, completely abolished the stress fiber formation and contractility of these cells, and reduced their proliferation and ability to stabilize the surrounding matrix. Mice lacking Myh9 in CFs have an increased post-MI cardiac rupture rate compared to WT mice regardless of sexes ( p =0.004 and 0.02 for male and female mice, respectively). In vitro and in vivo transcriptomic and proteomics analysis revealed disrupted expression of stress fiber and mesenchymal identity genes/proteins caused by Myh9 KO. Mechanistically, Myh9 KO led to an increased globular to filamentous (G/F) actin ratio. The altered actin dynamics likely trigger multiple epigenetic events, which together lead to significantly altered cardiac myofibroblast gene expression and activities beyond contraction.
Abstract We147: The Utility of Cardiopulmonary Exercise Testing (CPET) Amongst Male and Female athletes to Differentiate Between Physiological Left Ventricular Enlargement and Mildly Depressed Resting Systolic Function and Athletic Individuals with Dilated Cardiomyopathy.
Authors: Sarandeep Marwaha, Zephryn Fanton, Paulo Bulleros, Rachel Simmons, Raghav T Bhatia, Hamish MacLachlan, Maite Tome, Gherardo Finocchiaro, Aneil Malhotra, Sabiha Gati, Sanjay Prasad, Michael Papadakis, Sanjay Sharma
Journal: Circulation Research (2024)

Background: Athletes frequently reveal a dilated left ventricle (LV),some also demonstrate a co-existent mildly depressed LV ejection fraction, raising the possibility of mild dilated cardiomyopathy (DCM). The maximal oxygen consumption(VO2max) is a valuable tool for assessing fitness, largely determined by cardiac output. References ranges derived from the general population, may have limitations when assessing athletes with primary myocardial disease. This study investigated the role of VO2max and VO2max predicted (V02pred) to differentiate between physiological LV dilatation and athletic individuals with DCM in male and female athletes. Methods: 147 male and 35 female athletes with dilated LV(mean age 35.4years, 34.5 years respectively) underwent a 25watt cycle ergometer continuous ramp protocol. 75% males and 67% females participated in endurance sports, remaining participating in mixed sports. 52 had mild DCM, 62 defined as healthy control athletes(dilated LV) and 68 were Grey zone (dilated LV and mildly depressed LVEF) Results: DCM males (N=39) revealed a lower mean VO2max than male control (N=46), 34.9ml/kg/min and 48ml/kg/min respectively (p value &lt;0.001). DCM females(N=13) showed lower VO2max of 29.9ml/min/kg than female control (N=16) who revealed similar values to male controls (48 ml/kg/min)(p value &lt;0.001). 62 male Grey zones and 6 female Grey zone revealed lower VO2max than controls 43.1ml/min/kg and 34.1ml/min/kg respectively. DCM females had lower VO2pred than control females 119% and 161% respectively but significantly higher than their male counterparts, means of 106% and 123% respectively (p value &lt;0.001). Male and female grey zones had lower mean VO2pred than controls, 121% and 106% respectively. Higher VO2max of ≥38ml/kg/min and VO2pred of ≥120% gave a sensitivity, specificity of 84.7% and 77%respectively to differentiate healthy athletes and athletic DCMs in males and females. Only41.1% Grey zone athletes were able to achieve above these thresholds. Conclusion: Female athletes with dilated LV may reveal supranormal VO2max which can equal their male counterparts. Furthermore, athletic females with physiological or pathological LV dilatation can reveal higher VO2pred than male athletes. Most athletic DCM individuals show lower CPET parameters than controls athletes but can still achieve greater than normal measurements seen in healthy general population. VO2 may have a role in assisting in differentiating healthy athletes from athletic DCM.
Recaticimab Monotherapy for Nonfamilial Hypercholesterolemia and Mixed Hyperlipemia
Authors: Mingtong Xu, Zhen Wang, Yumin Zhang, Yong Liu, Rongjie Huang, Xuebin Han, Zhuhua Yao, Jiao Sun, Fengsheng Tian, Xitian Hu, Liping Ma, Chunlin Lai, Xiwen Zhang, Jianlong Sheng, Qinghua Han, Chunrong Jin, Li Luo, Ruiping Zhao, Liwen Li, Biao Xu, Delu Yin, Suxin Luo, Xiaofeng Ge, Zhiyuan Liu, Ping Yang, Zheng Huang, Tianfa Li, Wei Feng, Yanqing Wu, Zhiyu Ling, Likun Ma, Chao Lv, Chanjuan Deng, Wenhua Wei, Ying Wang, Li Yan, JunBo Ge
Journal: Journal of the American College of Cardiology (2024)
Abstract We028: Decoding m6a RNA methylomes identifies Igf2bp1 as a common barrier to direct reprogramming
Authors: Yifang Xie, Qiaozi Wang, Brian Spurlock, Jiandong Liu, Li Qian
Journal: Circulation Research (2024)

Direct reprogramming has revolutionized the fields of stem cell biology and regenerative medicine. Targeted transdifferentiation of cells in situ holds significant promise in treating a large swathe of illness and injury including cardiovascular disease. However, much remains unknown about the molecular mechanisms of direct reprogramming, particularly its post-transcriptional regulation, including the role of m6a RNA modification. Here, by characterizing early changes in the m6a RNA methylome during reprogramming of fibroblasts toward three distinct lineages—cardiac, hepatic and neuronal—we identify lineage-specific features as well as common regulatory patterns. Our data reveal extensive changes in m6a methylome of direct reprogramming with clear impacts on cell fate decisions. Through loss-of-function screening of m6a readers, we uncovered Igf2bp1(insulin-like growth factor 2 mRNA binding protein 1) as a shared barrier to direct reprogramming. Further mechanistic studies will show how Igf2bp1 influences the reprogramming process mediated via m6a modifications. Collectively, our results present a fascinating portrait of m6a RNA methylome during direct reprogramming and reveal a key role of Igf2bp1 in maintaining cell fate, enhancing our mechanistic understanding of the reprogramming process.
Abstract We026: Foxk1 and Foxk2 Promote Cardiomyocyte Proliferation and Heart Regeneration
Authors: Dongcheng Cai, Chungeng Liu, Haotong Li, Yu Nie
Journal: Circulation Research (2024)

Background: The adult mammalian heart exhibits limited regenerative capacity due to restricted cardiomyocyte (CM) proliferation following injuries like ischemia. Foxk1 and Foxk2, members of the Foxk family, are pivotal in cell proliferation and metabolic regulation. However, the roles of Foxk1 and Foxk2 in CM proliferation and heart regeneration remain elusive. Hypothesis: We propose that Foxk1 and Foxk2 are master regulators of CM proliferation and heart regeneration. Methods: Three genetic mouse lines, Myh6-CreER , Foxk1 fl/fl , and Foxk2 fl/fl were used to generate CM-specific Foxk1 or Foxk2 deficient mice. Myocardial infarction was performed in neonatal and adult mice. Cleavage Under Targets and Tagmentation sequencing (CUT&amp;Tag-seq), RNA sequencing (RNA-seq), qRT-PCR, Western blotting, immunostaining, and Seahorse metabolic assays were conducted to investigate the intrinsic mechanisms by which Foxk1 and Foxk2 regulate CM proliferation and heart regeneration. Masson’s staining and echocardiography were conducted to evaluate cardiac fibrosis and function, respectively. Results: Our results showed that the expression of Foxk1 and Foxk2 gradually decreased in CMs during postnatal heart development. CM-specific knockout of Foxk1 or Foxk2 inhibited neonatal heart regeneration after MI. AAV9-mediated CM-specific overexpression of Foxk1 or Foxk2 prolonged the postnatal proliferative window of CMs in mice. AAV9-mediated overexpression of Foxk1 or Foxk2 in adult mice improved heart regeneration by promoting endogenous CM proliferation after MI. Through joint analysis of RNA-Seq and CUT&amp;Tag-seq, we found that Foxk1 and Foxk2 regulated Ccnb1 and Cdk1 transcription respectively. Knockdown of Ccnb1 hindered CM proliferation induced by Foxk1 overexpression, and the same effect was observed when Cdk1 was knocked down in Foxk2-overexpressing CMs. Additionally, Foxk1 and Foxk2 induced CM metabolic reprogramming, suppressing mitochondrial oxidative phosphorylation (OXPHOS) via Hif1α upregulation and reducing oxidative DNA damage, thereby modulating the cell cycle. Conclusions: Foxk1 and Foxk2 promote CM proliferation and heart regeneration. Mechanistically, Foxk1 and Foxk2 promote CM proliferation via dual effects that directly promote cell cycle gene transcription and induce metabolic reprogramming. Our findings suggest these transcription factors as potential novel targets in cardiac regeneration post-injury.
Abstract We039: Adducin Promotes Cardiomyocyte Sarcomere Disassembly
Authors: Feng Xiao, Ngoc Uyen Nhi Nguyen, Ping Wang, Ching-Cheng Hsu, Shujuan Li, Suwannee Thet, Wataru Kimura, Xiang Luo, Nicholas Lam, Ivan Menendez-Montes, Waleed Elhelaly, Rohit Singh, Sakthivel Sadayappan, Mohammed Kanchwala, Chao Xing, Feria Ladha, Travis Hinson, Roger Hajjar, Joseph Hill, Hesham Sadek
Journal: Circulation Research (2024)

Introduction: Recent interest in understanding the cardiomyocyte cell cycle has been driven by potential therapeutic applications in cardiomyopathy. Despite advancements, the intricacies of cardiomyocyte mitosis, especially the breakdown of sarcomeres to enable daughter cardiomyocytes' division, remain largely unexplored. Hypothesis: This study investigates the role of Adducin in the disassembly of sarcomeres during cardiomyocyte mitosis, hypothesizing that Adducin serves as a crucial regulator in this process. Goals: Our objective is to elucidate the function of Adducin in sarcomere disassembly during the mitosis of mammalian cardiomyocytes and understand how this process is regulated. Methods: We examined the expression patterns of α/γ-Adducins, particularly in neonatal cardiomyocytes undergoing mitosis. Subsequently, we experimented with the overexpression of various α-Adducin splices and phosphorus in vitro and in vivo, with a keen interest in the phosphorylation effects of α-Adducin on sarcomere disassembly. Results: Here, we identify Adducin as a regulator of sarcomere disassembly during mammalian cardiomyocyte mitosis. α/γ-Adducins are selectively expressed in neonatal mitotic cardiomyocytes, and their levels decline precipitously thereafter. Cardiomyocyte-specific overexpression of various splice isoforms and phosphoforms of α-Adducin in vitro and in vivo identified Thr445/Thr480 phosphorylation of a short isoform of α-Adducin as a potent inducer of neonatal cardiomyocyte sarcomere disassembly. Additionally, co-overexpressing this α-Adducin variant with γ-Adducin in adult mice stabilizes the Adducin complex and maintains sarcomere disassembly, facilitated through interactions with α-Actinin. Conclusion: The study highlights Adducin, particularly α-Adducin phosphorylated at Thr445/Thr480, as a pivotal regulator of sarcomere disassembly during neonatal cardiomyocyte mitosis. This mechanism is essential for coordinating the cytoskeletal changes necessary for the mitotic process in cardiomyocytes, offering insights into potential therapeutic targets for cardiomyopathy.
Abstract We032: FOXK1-Gli2 network regulates cardiomyocyte proliferation and heart regeneration
Authors: Thijs Larson, Satyabrata Das, Javier Sierra-Pagan, Young Geun Choi, Xiao Ma, Alice Bieda, Tamas Alexy, qinglu li, Hesham Sadek, Jianyi Zhang, Mary Garry, Daniel Garry
Journal: Circulation Research (2024)

Unlike adult mammals, the neonatal mouse has an exceptional regenerative capacity following myocardial injury. Our goal was to decipher and define novel factors and mechanisms that have a role in regeneration of the injured adult mouse heart. FOXK1 is a transcription factor that regulates cell cycle kinetics, myogenic stem cell proliferation, and skeletal muscle regeneration. During development, its expression is restricted to progenitors, somites and the heart. In these studies, we identified a novel role for FOXK1 as a regulator of cardiomyocyte (CM) proliferation and regeneration through the regulation of Gli2 . Analysis of single nucleus RNAseq datasets of neonatal hearts revealed that FOXK1 was expressed in neonatal CMs. qPCR analysis from P1 hearts of control and Foxk1 null mice confirmed this finding and demonstrated dysregulation of the cell cycle regulators, Ccne1 and p21 , in the absence of Foxk1 . Control and Foxk1 null mice were pulsed with EdU from P3 to P7 which demonstrated that the absence of Foxk1 led to a decrease in CM proliferation in-vivo. Then, using a transgenic mouse model that we engineered to overexpress FOXK1 in muscle ( MCK-Foxk1 ), we observed CM proliferation in adult MCK-Foxk1 mice, which showed increased incorporation of EdU and increased pH3 expression compared to control. Bulk RNA-seq analysis of P1, P7, and P14 hearts indicated increased CM proliferation in the MCK-Foxk1 mouse and revealed Gli2 as a potential downstream target of FOXK1. A gel shift assay was performed, which demonstrated that FOXK1 was able to bind to a FOXK1 motif upstream of the Gli2 gene. ChIP-PCR further verified that Gli2 was a direct downstream target of FOXK1 in the embryonic stem cell-embryoid body (ES-EB) system. We then performed ligation of the left anterior descending coronary artery (LAD) in adult control and MCK-Foxk1 mice. Echocardiography following the LAD-ligation injuries showed improved cardiac function in MCK-Foxk1 transgenic mice compared with controls. These results identify FOXK1 as a regulator of CM proliferation and heart regeneration and suggest that this function is mediated through the regulation of Gli2 gene expression.
Abstract We030: Microtubule Organizing Centers in Cardiomyocyte Proliferation and Maturation
Authors: Siqi Li, Enrique Avila, Anna Berthiaume, Katelyn Albrecht, Chun Liu, Lu Han
Journal: Circulation Research (2024)

Mammalian cardiomyocytes undergo a loss of proliferative capacity due to cell division failure, leading to polyploidy (genome duplication) during postnatal maturation. Centrosomes, primary microtubule organizing centers (MTOCs) in animal cells comprised of centrioles and pericentriolar matrix (PCM), play a crucial role in cell division. In differentiated cells, non-centrosomal (nc) MTOCs can reorganize microtubules, with cellular localization varying between cell types to mediate specialized functions. The specific role of ncMTOCs in cardiomyocyte division and maturation remains unknown. This study investigates the formation and function of ncMTOCs in cardiomyocytes, aiming to elucidate the regulating mechanism. Our results demonstrate that during the maturation of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs), centrosomes disassemble, and their PCM translocates to the nuclear envelope, establishing perinuclear ncMTOCs. Furthermore, maturing CMs with ncMTOCs often exhibit polyploidy, indicating incomplete cell division. Microtubule dynamic experiments reveal that ncMTOCs serve as organizing centers for microtubules, promoting their assembly around the nucleus in maturing cardiomyocytes. To understand the mechanism regulating the transition from centrosomes to ncMTOCs in cardiomyocytes, we identified a significant downregulation of the nuclear lamina protein Lamin B2 (LMNB2) during CM maturation. Our results indicate that LMNB2 is essential for mitotic spindle formation in CMs but not in stem cells, suggesting a distinct role for LMNB2 in CMs. Our results also suggest an increased centrosome to ncMTOC transition in LMNB2-depleted CMs at an early differentiation stage. Ongoing research aims to investigate the impact of perinuclear ncMTOCs on cardiomyocyte proliferation through pericentriolar matrix knockdown in hiPSC-CMs. Additionally, the study seeks to further elucidate the role of Lamin B2 in the transition of centrosome proteins and its underlying mechanism.
Abstract We144: Fto Deficiency Causes Cardiac Dysfunction by Altering Expression of Serca2a mRNA
Authors: Anh Phan, shihong zhang, Alex Gallinat, Alan Shao, Xisheng Li, Susmita Sahoo
Journal: Circulation Research (2024)

Introduction and Research Question: The impact of post-transcriptional regulation of gene expression, including N6-methyladenosine (m6A) messenger RNA methylation, on cardiac function has not yet been fully understood. Our study found that the absence of the m6A eraser, Fat mass and obesity-associated protein (Fto), in cardiomyocytes of adult mice led to cardiac dysfunction and cardiac hypertrophy. Methods and Results: To evaluate Fto physiological functions, we generated a tamoxifen-inducible cardiac-specific Fto knockout mouse model (Fto cKO). This resulted in a substantial reduction of Fto at both mRNA and protein levels in the whole heart, leading to an almost complete absence of Fto within cardiomyocytes. Echocardiography analyses showed that Fto cKO mice exhibit impaired cardiac functions, indicated by a 30% reduction in ejection fraction and 40% decrease in fractional shortening after one month of deletion of cardiac Fto ( p&lt;0.01 ). We found a significant increase in heart weight to body weight ratios in Fto cKO animals ( p&lt;0.05 ). This result corresponded with an increased expression of hypertrophic markers including Nppb and Myh7 mRNA in the absence of Fto ( p&lt;0.01 ). We noted an increase in the length of Fto cKO cardiomyocytes ( p&lt;0.05 ) in isolated cardiomyocytes, a characteristic feature of eccentric pathologic hypertrophy. Electron microscopy analysis of intact hearts showed ultrastructure abnormalities in cardiomyocytes from Fto cKO mice including Z-line density loss and disarray in cristae alignment of mitochondria. Moreover, cardiomyocytes from Fto cKO mice demonstrated defects in sarcomeric shortening including a prolongation of time to 90% peak, time to 90% rest, and decay time constant of relaxation for sarcomere shortening ( p&lt;0.001 ), compared to control mice. Mechanistically, we found down-regulation of Serca2a and Ryr2 mRNA in cardiomyocytes lacking Fto. We further demonstrated that Fto binds Serca2a mRNA and controls its cytoplasmic-nuclear shuttling. Fto deficiency led to accumulation of Serca2a mRNA in the nucleus. Conclusion: These findings suggest that Fto plays a pivotal role as a crucial regulator for cardiac function. Consequently, our results unveil a significant and novel mechanism through which Fto-dependent regulation contributes to the preservation of cardiac homeostasis.