Biology of the cardiac myocyte in heart disease

Transcriptomic Approaches to Cardiomyocyte-Biomaterial Interactions: A Review

Biomaterials, essential for supporting, enhancing, and repairing damaged tissues, play a critical role in various medical applications. This Review focuses on the interaction of biomaterials and cardiomyocytes, emphasizing the unique significance of transcriptomic approaches in understanding their interactions, which are pivotal in cardiac bioengineering and regenerative medicine. Transcriptomic approaches serve as powerful tools to investigate how cardiomyocytes respond to biomaterials, shedding light on the gene expression patterns, regulatory pathways, and cellular processes involved in these interactions. Emerging technologies such as bulk RNA-seq, single-cell RNA-seq, single-nucleus RNA-seq, and spatial transcriptomics offer promising avenues for more precise and in-depth investigations. Longitudinal studies, pathway analyses, and machine learning techniques further improve the ability to explore the complex regulatory mechanisms involved. This review also discusses the challenges and opportunities of utilizing transcriptomic techniques in cardiomyocyte-biomaterial research. Although there are ongoing challenges such as costs, cell size limitation, sample differences, and complex analytical process, there exist exciting prospects in comprehensive gene expression analyses, biomaterial design, cardiac disease treatment, and drug testing. These multimodal methodologies have the capacity to deepen our understanding of the intricate interaction network between cardiomyocytes and biomaterials, potentially revolutionizing cardiac research with the aim of promoting heart health, and they are also promising for studying interactions between biomaterials and other cell types.

Empagliflozin attenuates doxorubicin-induced cardiotoxicity by inhibiting the JNK signaling pathway

BACKGROUND

Sodium-glucose cotransporter-2 inhibitors, such as empagliflozin, are pivotal therapies for heart failure. However, the effect of empagliflozin on doxorubicin-related cardiac dysfunction remains unclear.

METHODS

Human induced pluripotent stem cell- and embryonic stem cell-derived cardiomyocytes were used to investigate the direct effect of empagliflozin on human cardiomyocytes. Then, the c-Jun amino-terminal kinases (JNK) inhibitor SP600125 was administered to the doxorubicin cardiotoxicity model in vitro and in vivo to investigate the role of JNK in empagliflozin.

RESULTS

In human stem cell-derived cardiomyocytes, pretreatment with empagliflozin attenuated doxorubicin-induced cleavage of caspase 3 and other apoptosis markers. Empagliflozin significantly attenuated doxorubicin-induced phosphorylation of JNK and p38. Inhibiting the phosphorylation of JNK (SP600125) or STAT3 attenuated doxorubicin-induced apoptosis, but inhibiting the phosphorylation of p38 did not. SP600125 inhibits the phosphorylation of STAT3 (S727), and a STAT3 (Y705) inhibitor also inhibits the phosphorylation of JNK. Empagliflozin and SP600125 attenuated doxorubicin-induced increases in reactive oxygen species (ROS) and decreases in oxidized nicotinamide adenine dinucleotide (NAD+). In animal studies, empagliflozin and SP600125 attenuated doxorubicin-induced cardiac dysfunction and fibrosis.

CONCLUSIONS

Empagliflozin attenuated doxorubicin-induced apoptosis by inhibiting the phosphorylation of JNK and its downstream signaling pathways, including ROS and NAD+.

Signaling Pathways Governing Cardiomyocyte Differentiation

Cardiomyocytes are the largest cell type that make up the heart and confer beating activity to the heart. The proper differentiation of cardiomyocytes relies on the efficient transmission and perception of differentiation cues from several signaling pathways that influence cardiomyocyte-specific gene expression programs. Signaling pathways also mediate intercellular communications to promote proper cardiomyocyte differentiation. We have reviewed the major signaling pathways involved in cardiomyocyte differentiation, including the BMP, Notch, sonic hedgehog, Hippo, and Wnt signaling pathways. Additionally, we highlight the differences between different cardiomyocyte cell lines and the use of these signaling pathways in the differentiation of cardiomyocytes from stem cells. Finally, we conclude by discussing open questions and current gaps in knowledge about the in vitro differentiation of cardiomyocytes and propose new avenues of research to fill those gaps.

Nanomedicine And Nanotheranostics: Special Focus on Imaging of Anticancer Drugs Induced Cardiac Toxicity

Cardiotoxicity, the often-overlooked second leading cause of death in cancer patients, has been associated with certain anticancer drugs. These drugs can induce cardiac damage through various pathways, and their adverse effects on the heart are not fully understood. Cardiotoxicity is a major issue in cancer treatment, particularly with chemotherapeutics, because it can cause cardiac dysfunction such as hypotension, heart failure, and even death. Doxorubicin, 5-fluorouracil, and trastuzumab, all of which are very potent anticancer drugs, are known to cause cardiotoxicity. When it comes to lowering cardiotoxicity and alleviating the harmful effects of chemotherapy medications, nanomedicine has the potential to transport therapeutic molecules. Nanotheranostics offers novel options for identifying and treating cardiotoxicity resulting from a wide range of substances, including anticancer medications. Additionally, theranostics platforms such as micellar systems, carbon-based nanomedicine, solid lipid nanoparticles, polymeric nanoparticles, and liposomes can transport chemotherapeutic medications while minimising their cardiotoxicity. The present level of understanding of the molecular and cellular processes that lead to cardiotoxicity in reaction to both traditional chemotherapy and targeted drug delivery systems is summarised in this article. This review delves into nanomedicine and nanotheranostics, with an emphasis on reducing anticancer medication-induced cardiac toxicity. Nanotheranostics provide potential solutions for early diagnosis and tailored therapy of heart injury by combining diagnostic and therapeutic capabilities into nanomedicine.

Tailoring transfection for cardiomyocyte cell lines: balancing efficiency and toxicity in lipid versus polymer-based transfection methods in H9c2 and HL-1 cells

Cardiovascular research relies heavily on the veracity of in vitro cardiomyocyte models, with H9c2 and HL-1 cell lines at the forefront due to their cardiomyocyte-like properties. However, the variability stemming from nonstandardized culturing and transfection methods poses a significant challenge to data uniformity and reliability. In this study, we introduce meticulously crafted protocols to enhance the culture and transfection of H9c2 and HL-1 cells, emphasizing the reduction of cytotoxic effects while improving transfection efficiency. Through the examination of polymer-based and lipid-based transfection methods, we offer a comparative analysis that underscores the heightened efficiency and reduced toxicity of these approaches. Our research provides an extensive array of step-by-step procedures designed to foster robust cell cultures and outlines troubleshooting practices to rectify issues of low transfection rates. We discuss the merits and drawbacks of both transfection techniques, equipping researchers with the knowledge to choose the most fitting method for their experimental goals. By offering a definitive guide to these cell lines' culturing and transfection, our work seeks to set a new standard in procedural consistency, ensuring that the cardiovascular research community can achieve more dependable and reproducible results, thereby pushing the boundaries of current methodologies toward impactful clinical applications.NEW & NOTEWORTHY We have developed standardized protocols that significantly reduce cytotoxicity and enhance transfection efficiency in H9c2 and HL-1 cardiomyocyte cell lines. Our detailed comparative analysis of polymer-based and lipid-based transfection methods has identified optimized approaches with superior performance. Accompanying these protocols are comprehensive troubleshooting strategies to address common issues related to low transfection rates. Implementing these protocols is expected to yield more consistent and reproducible results, driving the field of cardiovascular research toward impactful clinical breakthroughs.

Single-Cell Analysis of Contractile Forces in iPSC-Derived Cardiomyocytes: Paving the Way for Precision Medicine in Cardiovascular Disease

Induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) hold enormous potential in cardiac disease modeling, drug screening, and regenerative medicine. Furthermore, patient-specific iPSC-CMS can be tested for personalized medicine. To provide a deeper understanding of the contractile force dynamics of iPSC-CMs, we employed Atomic Force Microscopy (AFM) as an advanced detection tool to distinguish the characteristics of force dynamics at a single cell level. We measured normal (vertical) and lateral (axial) force at different pacing frequencies. We found a significant correlation between normal and lateral force. We also observed a significant force-frequency relationship for both types of forces. This work represents the first demonstration of the correlation of normal and lateral force from individual iPSC-CMs. The identification of this correlation is relevant because it validates the comparison across systems and models that can only account for either normal or lateral force. These findings enhance our understanding of iPSC-CM properties, thereby paving the way for the development of therapeutic strategies in cardiovascular medicine.

Comparative Analysis of Heart Regeneration: Searching for the Key to Heal the Heart-Part I: Experimental Injury Models to Study Cardiac Regeneration

Cardiovascular diseases are the leading cause of death worldwide, among which, ischemic heart disease is the most prevalent. Myocardial infarction results from occlusion of a coronary artery, which leads to an insufficient blood supply to the myocardium. As is well known, the massive loss of cardiomyocytes cannot be solved due the limited regenerative ability of the adult mammalian heart. In contrast, some lower vertebrate species can regenerate the heart after injury; their study has disclosed some of the involved cell types, molecular mechanisms and signaling pathways during the regenerative process. In this two-part review, we discuss the current state of the principal response in heart regeneration, where several involved processes are essential for full cardiac function in recovery.

The Microenvironment of the Pathogenesis of Cardiac Hypertrophy

Pathological cardiac hypertrophy is a key risk factor for the development of heart failure and predisposes individuals to cardiac arrhythmia and sudden death. While physiological cardiac hypertrophy is adaptive, hypertrophy resulting from conditions comprising hypertension, aortic stenosis, or genetic mutations, such as hypertrophic cardiomyopathy, is maladaptive. Here, we highlight the essential role and reciprocal interactions involving both cardiomyocytes and non-myocardial cells in response to pathological conditions. Prolonged cardiovascular stress causes cardiomyocytes and non-myocardial cells to enter an activated state releasing numerous pro-hypertrophic, pro-fibrotic, and pro-inflammatory mediators such as vasoactive hormones, growth factors, and cytokines, i.e., commencing signaling events that collectively cause cardiac hypertrophy. Fibrotic remodeling is mediated by cardiac fibroblasts as the central players, but also endothelial cells and resident and infiltrating immune cells enhance these processes. Many of these hypertrophic mediators are now being integrated into computational models that provide system-level insights and will help to translate our knowledge into new pharmacological targets. This perspective article summarizes the last decades' advances in cardiac hypertrophy research and discusses the herein-involved complex myocardial microenvironment and signaling components.

Three-dimensional analysis of hydrogel-imbedded aortic valve interstitial cell shape and its relation to contractile behavior

Cell-shape is a conglomerate of mechanical, chemical, and biological mechanisms that reflects the cell biophysical state. In a specific application, we consider aortic valve interstitial cells (AVICs), which maintain the structure and function of aortic heart valve leaflets. Actomyosin stress fibers help determine AVIC shape and facilitate processes such as adhesion, contraction, and mechanosensing. However, detailed 3D assessment of stress fiber architecture and function is currently impractical. Herein, we assessed AVIC shape and contractile behaviors using hydrogel-based 3D traction force microscopy to intuit the orientation and behavior of AVIC stress fibers. We utilized spherical harmonics (SPHARM) to quantify AVIC geometries through three days of incubation, which demonstrated a shift from a spherical shape to forming substantial protrusions. Furthermore, we assessed changes in post-three day AVIC shape and contractile function within two testing regimes: (1) normal contractile level to relaxation (cytochalasin D), and (2) normal contractile level to hyper-contraction (endothelin-1). In both scenarios, AVICs underwent isovolumic shape changes and produced complex displacement fields within the hydrogel. AVICs were more elongated when relaxed and more spherical in hyper-contraction. Locally, AVIC protrusions contracted along their long axis and expanded in their circumferential direction, indicating predominately axially aligned stress fibers. Furthermore, the magnitude of protrusion displacements was correlated with protrusion length and approached a consistent displacement plateau at a similar critical length across all AVICs. This implied that stress fiber behavior is conserved, despite great variations in AVIC shapes. We anticipate our findings will bolster future investigations into AVIC stress fiber architecture and function. STATEMENT OF SIGNIFICANCE: Within the aortic valve there exists a population of aortic valve interstitial cells, which orchestrate the turnover, secretion, and remodeling of its extracellular matrix, maintaining tissue integrity and ultimately sustaining the proper mechanical function. Alterations in these processes are thought to underlie diseases of the aortic valve, which affect hundreds of thousands domestically and world-wide. Yet, to date, there are no non-surgical treatments for aortic heart valve disease, in part due to our limited understanding of the underlying disease processes. In the present study, we built upon our previous study to include a full 3D analysis of aortic valve interstitial cell shapes at differing contractile levels. The resulting detailed shape and deformation analysis provided insight into the underlying stress-fiber structures and mechanical behaviors.

Three tyrosine kinase inhibitors cause cardiotoxicity by inducing endoplasmic reticulum stress and inflammation in cardiomyocytes

BACKGROUND

Tyrosine kinase inhibitors (TKIs) are anti-cancer therapeutics often prescribed for long-term treatment. Many of these treatments cause cardiotoxicity with limited cure. We aim to clarify molecular mechanisms of TKI-induced cardiotoxicity so as to find potential targets for treating the adverse cardiac complications.

METHODS

Eight TKIs with different levels of cardiotoxicity reported are selected. Phenotypic and transcriptomic responses of human cardiomyocytes to TKIs at varying doses and times are profiled and analyzed. Stress responses and signaling pathways that modulate cardiotoxicity induced by three TKIs are validated in cardiomyocytes and rat hearts.

RESULTS

Toxicity rank of the eight TKIs determined by measuring their effects on cell viability, contractility, and respiration is largely consistent with that derived from database or literature, indicating that human cardiomyocytes are a good cellular model for studying cardiotoxicity. When transcriptomes are measured for selected TKI treatments with different levels of toxicity in human cardiomyocytes, the data are classified into 7 clusters with mainly single-drug clusters. Drug-specific effects on the transcriptome dominate over dose-, time- or toxicity-dependent effects. Two clusters with three TKIs (afatinib, ponatinib, and sorafenib) have the top enriched pathway as the endoplasmic reticulum stress (ERS). All three TKIs induce ERS in rat primary cardiomyocytes and ponatinib activates the IRE1α-XBP1s axis downstream of ERS in the hearts of rats underwent a 7-day course of drug treatment. To look for potential triggers of ERS, we find that the three TKIs induce transient reactive oxygen species followed by lipid peroxidation. Inhibiting either PERK or IRE1α downstream of ERS blocks TKI-induced cardiac damages, represented by the induction of cardiac fetal and pro-inflammatory genes without causing more cell death.

CONCLUSIONS

Our data contain rich information about phenotypic and transcriptional responses of human cardiomyocytes to eight TKIs, uncovering potential molecular mechanisms in modulating cardiotoxicity. ER stress is activated by multiple TKIs and leads to cardiotoxicity through promoting expression of pro-inflammatory factors and cardiac fetal genes. ER stress-induced inflammation is a promising therapeutic target to mitigate ponatinib- and sorafenib-induced cardiotoxicity.

FK506-Binding Protein like (FKBPL) Has an Important Role in Heart Failure with Preserved Ejection Fraction Pathogenesis with Potential Diagnostic Utility

Heart failure (HF) is the leading cause of hospitalisations worldwide, with only 35% of patients surviving the first 5 years after diagnosis. The pathogenesis of HF with preserved ejection fraction (HFpEF) is still unclear, impeding the implementation of effective treatments. FK506-binding protein like (FKBPL) and its therapeutic peptide mimetic, AD-01, are critical mediators of angiogenesis and inflammation. Thus, in this study, we investigated-for the first time-FKBPL's role in the pathogenesis and as a biomarker of HFpEF. In vitro models of cardiac hypertrophy following exposure to a hypertensive stimulus, angiotensin-II (Ang-II, 100 nM), and/or AD-01 (100 nM), for 24 and 48 h were employed as well as human plasma samples from people with different forms of HFpEF and controls. Whilst the FKBPL peptide mimetic, AD-01, induced cardiomyocyte hypertrophy in a similar manner to Ang-II (p < 0.0001), when AD-01 and Ang-II were combined together, this process was abrogated (p < 0.01-0.0001). This mechanism appears to involve a negative feedback loop related to FKBPL (p < 0.05). In human plasma samples, FKBPL concentration was increased in HFpEF compared to controls (p < 0.01); however, similar to NT-proBNP and Gal-3, it was unable to stratify between different forms of HFpEF: acute HFpEF, chronic HFpEF and hypertrophic cardiomyopathy (HCM). FKBPL may be explored for its biomarker and therapeutic target potential in HFpEF.

An efficient human stem cells derived cardiotoxicity testing platform for testing oncotherapeutic analogues of quercetin and cinnamic acid

Oncotherapeutics research is progressing at a rapid pace, however, not many drugs complete the successful clinical trial because of severe off-target toxicity to cardiomyocytes which ultimately leads to cardiac dysfunction. It is thus important to emphasize the need for early testing for possible cardiotoxicity of emerging oncotherapeutics. In this study, we assessed a novel stem cell-derived cardiac model for testing for cardiotoxicity of novel oncotherapeutics. We evaluated the cardiotoxic effect of synthesized derivatives of oncotherapeutics, quercetin (QMJ-2, -5, and -6) and cinnamic acid (NMJ-1, -2, and -3) using human Wharton's jelly mesenchymal stem cells-derived cardiomyocytes (WJCM) against known cardiotoxic oncologic drugs, doxorubicin, 5-fluorouracil, cisplatin. QMJ-6, NMJ-2, and NMJ-3 were not cardiotoxic and had minimum cardiac side effects. They did not show any effect on cardiomyocyte viability, caused low LDH release, and intracellular ROS production kept the calcium flux minimal and protected the active mitochondrial status in cardiomyocytes. They persevered cardiac-specific gene expression as well. However, compounds QMJ-2, QMJ-5, and NMJ-1 were cardiotoxic and the concentration needs to be reduced to prevent toxic effects on cardiomyocytes. Significantly, we were able to demonstrate that WJCM is an efficient cardiac testing model to analyze the cardiotoxicity of drugs in a human context.

Cellular enlargement - A new hallmark of aging?

Years of important research has revealed that cells heavily invest in regulating their size. Nevertheless, it has remained unclear why accurate size control is so important. Our recent study using hematopoietic stem cells (HSCs) in vivo indicates that cellular enlargement is causally associated with aging. Here, we present an overview of these findings and their implications. Furthermore, we performed a broad literature analysis to evaluate the potential of cellular enlargement as a new aging hallmark and to examine its connection to previously described aging hallmarks. Finally, we highlight interesting work presenting a correlation between cell size and age-related diseases. Taken together, we found mounting evidence linking cellular enlargement to aging and age-related diseases. Therefore, we encourage researchers from seemingly unrelated areas to take a fresh look at their data from the perspective of cell size.

Merits of hiPSC-Derived Cardiomyocytes for In Vitro Research and Testing Drug Toxicity

The progress of medical technology and scientific advances in the field of anticancer treatment have increased the survival probabilities and duration of life of patients. However, cancer-therapy-induced cardiac dysfunction remains a clinically salient problem. Effective anticancer therapies may eventually induce cardiomyopathy. To date, several studies have focused on the mechanisms underlying cancer-treatment-related cardiotoxicity. Cardiomyocyte cell lines with no contractile physiological characteristics cannot adequately model “true” human cardiomyocytes. However, applying “true” human cardiomyocytes for research is fraught with many obstacles (e.g., invasiveness of the procedure), and there is a proliferative limitation for rodent primary cultures. Human-induced pluripotent stem-cell-differentiated cardiomyocytes (hiPSC-CMs), which can be produced efficiently, are viable candidates for mimicking human cardiomyocytes in vitro. We successfully performed cardiac differentiation of human iPSCs to obtain hiPSC-CMs. These hiPSC-CMs can be used to investigate the pathophysiological basis and molecular mechanism of cancer-treatment-related cardiotoxicity and to develop novel strategies to prevent and rescue such cardiotoxicity. We propose that hiPSC-CMs can be used as an in vitro drug screening platform to study targeted cancer-therapy-related cardiotoxicity.

Cardiac tissue engineering: Multiple approaches and potential applications

The overall increase in cardiovascular diseases and, specifically, the ever-rising exposure to cardiotoxic compounds has greatly increased in vivo animal testing; however, mainly due to ethical concerns related to experimental animal models, there is a strong interest in new in vitro models focused on the human heart. In recent years, human pluripotent stem cells-derived cardiomyocytes (hiPSC-CMs) emerged as reference cell systems for cardiac studies due to their biological similarity to primary CMs, the flexibility in cell culture protocols, and the capability to be amplified several times. Furthermore, the ability to be genetically reprogrammed makes patient-derived hiPSCs, a source for studies on personalized medicine. In this mini-review, the different models used for in vitro cardiac studies will be described, and their pros and cons analyzed to help researchers choose the best fitting model for their studies. Particular attention will be paid to hiPSC-CMs and three-dimensional (3D) systems since they can mimic the cytoarchitecture of the human heart, reproducing its morphological, biochemical, and mechanical features. The advantages of 3D in vitro heart models compared to traditional 2D cell cultures will be discussed, and the differences between scaffold-free and scaffold-based systems will also be spotlighted.

Myocardial infarction from a tissue engineering and regenerative medicine point of view: A comprehensive review on models and treatments

In the modern world, myocardial infarction is one of the most common cardiovascular diseases, which are responsible for around 18 million deaths every year or almost 32% of all deaths. Due to the detrimental effects of COVID-19 on the cardiovascular system, this rate is expected to increase in the coming years. Although there has been some progress in myocardial infarction treatment, translating pre-clinical findings to the clinic remains a major challenge. One reason for this is the lack of reliable and human representative healthy and fibrotic cardiac tissue models that can be used to understand the fundamentals of ischemic/reperfusion injury caused by myocardial infarction and to test new drugs and therapeutic strategies. In this review, we first present an overview of the anatomy of the heart and the pathophysiology of myocardial infarction, and then discuss the recent developments on pre-clinical infarct models, focusing mainly on the engineered three-dimensional cardiac ischemic/reperfusion injury and fibrosis models developed using different engineering methods such as organoids, microfluidic devices, and bioprinted constructs. We also present the benefits and limitations of emerging and promising regenerative therapy treatments for myocardial infarction such as cell therapies, extracellular vesicles, and cardiac patches. This review aims to overview recent advances in three-dimensional engineered infarct models and current regenerative therapeutic options, which can be used as a guide for developing new models and treatment strategies.

Upregulation of Phospholipase C Gene Expression Due to Norepinephrine-Induced Hypertrophic Response

The activation of phospholipase C (PLC) is thought to have a key role in the cardiomyocyte response to several different hypertrophic agents such as norepinephrine, angiotensin II and endothelin-1. PLC activity results in the generation of diacylglycerol and inositol trisphosphate, which are downstream signal transducers for the expression of fetal genes, increased protein synthesis, and subsequent cardiomyocyte growth. In this article, we describe the signal transduction elements that regulate PLC gene expression. The discussion is focused on the norepinephrine- α₁-adrenoceptor signaling pathway and downstream signaling processes that mediate an upregulation of PLC isozyme gene expression. Evidence is also indicated to demonstrate that PLC activities self-regulate the expression of PLC isozymes with the suggestion that PLC activities may be part of a coordinated signaling process for the perpetuation of cardiac hypertrophy. Accordingly, from the information provided, it is plausible that specific PLC isozymes could be targeted for the mitigation of cardiac hypertrophy.

Bioinformatics and System Biological Approaches for the Identification of Genetic Risk Factors in the Progression of Cardiovascular Disease

Background

Cardiovascular disease (CVD) is the combination of coronary heart disease, myocardial infarction, rheumatic heart disease, and peripheral vascular disease of the heart and blood vessels. It is one of the leading deadly diseases that causes one-third of the deaths yearly in the globe. Additionally, the risk factors associated with it make the situation more complex for cardiovascular patients, which lead them towards mortality, but the genetic association between CVD and its risk factors is not clearly explored in the global literature. We addressed this issue and explored the linkage between CVD and its risk factors.

Methods

We developed an analytical approach to reveal the risk factors and their linkages with CVD. We used GEO microarray datasets for the CVD and other risk factors in this study. We performed several analyses including gene expression analysis, diseasome analysis, protein-protein interaction (PPI) analysis, and pathway analysis for discovering the relationship between CVD and its risk factors. We also examined the validation of our study using gold benchmark databases OMIM, dbGAP, and DisGeNET.

Results

We observed that the number of 32, 17, 53, 70, and 89 differentially expressed genes (DEGs) is overlapped between CVD and its risk factors of hypertension (HTN), type 2 diabetes (T2D), hypercholesterolemia (HCL), obesity, and aging, respectively. We identified 10 major hub proteins (FPR2, TNF, CXCL8, CXCL1, IL1B, VEGFA, CYBB, PTGS2, ITGAX, and CCR5), 12 significant functional pathways, and 11 gene ontological pathways that are associated with CVD. We also found the connection of CVD with its risk factors in the gold benchmark databases. Our experimental outcomes indicate a strong association of CVD with its risk factors of HTN, T2D, HCL, obesity, and aging.

Conclusions

Our computational approach explored the genetic association of CVD with its risk factors by identifying the significant DEGs, hub proteins, and signaling and ontological pathways. The outcomes of this study may be further used in the lab-based analysis for developing the effective treatment strategies of CVD.

Compatibility and function of human induced pluripotent stem cell derived cardiomyocytes on an electrospun nanofibrous scaffold, generated from an ionomeric polyurethane composite

Synthetic scaffolds are needed for generating organized neo-myocardium constructs to promote functional tissue repair. This study investigated the biocompatibility of an elastomeric electrospun degradable polar/hydrophobic/ionic polyurethane (D-PHI) composite scaffold with human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). The composite material was electrospun to generate scaffolds, with nanofibres oriented in aligned or random directions. These features enabled the authors to evaluate the effect of characteristic elements which mimic that of the native extracellular matrix (alignment, chemical heterogeneity, and fiber topography) on hiPSC-CMs activity. The functional nature of the hiPSC-CM cultured on gelatin and Matrigel-coated scaffolds were assessed, investigating the influence of protein interactions with the synthetic substrate on subsequent cell phenotype. After 7 days of culture, high hiPSC-CM viability was observed on the scaffolds. The cells on the aligned scaffold were elongated and demonstrated aligned sarcomeres that oriented parallel to the direction of the fibers, while the cells on random scaffolds and a tissue culture polystyrene (TCPS) control did not exhibit such an organized morphology. The hiPSC-CMs cultured on the scaffolds and TCPS expressed similar levels of cardiac troponin-T, but there was a higher expression of ventricular myosin light chain-2 on the D-PHI composite scaffolds versus TCPS, indicating a higher proportion of hiPSC-CM exhibiting a ventricular cardiomyocyte like phenotype. Within 7 days, the hiPSC-CMs on aligned scaffolds and TCPS beat synchronously and had similar conductive velocities. These preliminary results show that aligned D-PHI elastomeric scaffolds allow hiPSC-CMs to demonstrate important cardiomyocytes characteristics, critical to enabling their future potential use for cardiac tissue regeneration.

Role of Phospholipase C in Catecholamine-induced Increase in Myocardial Protein Synthesis

The activation of the α1-adrenoceptor-(α1-AR) by norepinephrine results in the G-protein (Gqα) mediated increase in the phosphoinositide-specific phospholipase C (PLC) activity. The byproducts of PLC hydrolytic activity, namely, 1,2-diacylglycerol and inositol-1,4,5-trisphosphate, are important downstream signal transducers for increased protein synthesis in the cardiomyocyte and the subsequent hypertrophic response. In this article, evidence is outlined to demonstrate the role of cardiomyocyte PLC isozymes in the catecholamine-induced increase in protein synthesis by using a blocker of α1-AR and an inhibitor of PLC. The discussion will be focused on the α1-AR-Gqα-PLC-mediated hypertrophic signaling pathway from the viewpoint that it may compliment the other β1-AR-Gs protein-adenylyl cyclase signal transduction mechanisms in the early stages of cardiac hypertrophy development, but may become more relevant at the late stage of cardiac hypertrophy. From the information provided here, it is suggested that some specific PLC isozymes may potentially serve as important targets for the attenuation of cardiac hypertrophy in the vulnerable patient population at-risk for heart failure.

Genetically Encoded ATP Biosensors for Direct Monitoring of Cellular ATP Dynamics

Adenosine 5'-triphosphate, or ATP, is the primary molecule for storing and transferring energy in cells. ATP is mainly produced via oxidative phosphorylation in mitochondria, and to a lesser extent, via glycolysis in the cytosol. In general, cytosolic glycolysis is the primary ATP producer in proliferative cells or cells subjected to hypoxia. On the other hand, mitochondria produce over 90% of cellular ATP in differentiated cells under normoxic conditions. Under pathological conditions, ATP demand rises to meet the needs of biosynthesis for cellular repair, signaling transduction for stress responses, and biochemical processes. These changes affect how mitochondria and cytosolic glycolysis function and communicate. Mitochondria undergo remodeling to adapt to the imbalanced demand and supply of ATP. Otherwise, a severe ATP deficit will impair cellular function and eventually cause cell death. It is suggested that ATP from different cellular compartments can dynamically communicate and coordinate to adapt to the needs in each cellular compartment. Thus, a better understanding of ATP dynamics is crucial to revealing the differences in cellular metabolic processes across various cell types and conditions. This requires innovative methodologies to record real-time spatiotemporal ATP changes in subcellular regions of living cells. Over the recent decades, numerous methods have been developed and utilized to accomplish this task. However, this is not an easy feat. This review evaluates innovative genetically encoded biosensors available for visualizing ATP in living cells, their potential use in the setting of human disease, and identifies where we could improve and expand our abilities.

Measuring hypertrophy in neonatal rat primary cardiomyocytes and human iPSC-derived cardiomyocytes

In the heart, left ventricular hypertrophy is initially an adaptive mechanism that increases wall thickness to preserve normal cardiac output and function in the face of coronary artery disease or hypertension. Cardiac hypertrophy develops in response to pressure and volume overload but can also be seen in inherited cardiomyopathies. As the wall thickens, it becomes stiffer impairing the distribution of oxygenated blood to the rest of the body. With complex cellular signalling and transcriptional networks involved in the establishment of the hypertrophic state, several model systems have been developed to better understand the molecular drivers of disease. Immortalized cardiomyocyte cell lines, primary rodent and larger animal models have all helped understand the pathological mechanisms underlying cardiac hypertrophy. Induced pluripotent stem cell-derived cardiomyocytes are also used and have the additional benefit of providing access to human samples with direct disease relevance as when generated from patients suffering from hypertrophic cardiomyopathies. Here, we briefly review in vitro and in vivo model systems that have been used to model hypertrophy and provide detailed methods to isolate primary neonatal rat cardiomyocytes as well as to generate cardiomyocytes from human iPSCs. We also describe how to model hypertrophy in a "dish" using gene expression analysis and immunofluorescence combined with automated high-content imaging.

Alpha Mangostin Derived from Garcinia magostana Linn Ameliorates Cardiomyocyte Hypertrophy and Fibroblast Phenotypes in Vitro

Cardiac hypertrophy and fibrosis are significant risk factors for chronic heart failure (HF). Since pharmacotherapy agents targeting these processes have not been established, we investigated the effect of alpha-magostin (α-man) on cardiomyocyte hypertrophy and fibrosis in vitro. Primary cultured cardiomyocytes and cardiac fibroblasts were prepared from neonatal rats. After α-man treatment, phenylephrine (PE) and transforming growth factor-beta (TGF-β) were added to the cardiomyocytes and cardiac fibroblasts to induce hypertrophic and fibrotic responses, respectively. Hypertrophic responses were assessed by measuring the cardiomyocyte surface area and hypertrophic gene expression levels. PE-induced phosphorylation of Akt, extracellular signal-regulated kinase (ERK)1/2, and p38 was examined by Western blotting. Fibrotic responses were assessed by measuring collagen synthesis, fibrotic gene expression levels, and myofibroblast differentiation. In addition, TGF-β-induced reactive oxygen species (ROS) production was investigated. In cultured cardiomyocytes, α-man significantly suppressed PE-induced increases in the cardiomyocyte surface area, and the mRNA levels (atrial natriuretic factor (ANF) and brain natriuretic peptide (BNP)). Treatment with α-man significantly suppressed PE-induced Akt phosphorylation, but not ERK and p38 phosphorylation. In cultured cardiac fibroblasts, α-man significantly suppressed TGF-β-induced increases in L-proline incorporation, mRNA levels (POSTN and alpha-smooth muscle actin (α-SMA)), and myofibroblast differentiation. Additionally, it significantly inhibited TGF-β-induced reduced nicotinamide adenine dinucleotide phosphate oxidase4 (NOX4) expression and ROS production in cardiac fibroblasts. Treatment with α-man significantly ameliorates hypertrophy by inhibiting Akt phosphorylation in cardiomyocytes and fibrosis by inhibiting NOX4-generating ROS in fibroblasts. These findings suggest that α-man is a possible natural product for the prevention of cardiac hypertrophy and fibrosis.

Serum response factor deletion 5 regulates phospholamban phosphorylation and calcium uptake

AIMS

Pediatric dilated cardiomyopathy (pDCM) is characterized by unique age-dependent molecular mechanisms that include myocellular responses to therapy. We previously showed that pDCM, but not adult DCM patients respond to phosphodiesterase 3 inhibitors (PDE3i) by increasing levels of the second messenger cAMP and consequent phosphorylation of phospholamban (PLN). However, the molecular mechanisms involved in the differential pediatric and adult response to PDE3i are not clear.

METHODS AND RESULTS

Quantification of serum response factor (SRF) isoforms from the left ventricle of explanted hearts showed that PDE3i treatment affects expression of SRF isoforms in pDCM hearts. An SRF isoform lacking exon 5 (SRFdel5) was highly expressed in the hearts of pediatric, but not adult DCM patients treated with PDE3i. To determine the functional consequence of expression of SRFdel5, we overexpressed full length SRF or SRFdel5 in cultured cardiomyocytes with and without adrenergic stimulation. Compared to a control adenovirus, expression of SRFdel5 increased phosphorylation of PLN, negatively affected expression of the phosphatase that promotes dephosphorylation of PLN (PP2Cε), and promoted faster calcium reuptake, whereas expression of full length SRF attenuated calcium reuptake through blunted phosphorylation of PLN.

CONCLUSIONS

Taken together, these data indicate that expression of SRFdel5 in pDCM hearts in response to PDE3i contributes to improved function through regulating PLN phosphorylation and thereby calcium reuptake.

Evaluation of lung tumor motion in a large sample: Target-related and clinical factors influencing tumor motion based on four-dimensional CT

Background and purpose

We aimed to analyze the influence of target‐related and clinical factors on lung tumor motion based on four‐dimensional CT (4DCT), and clarify the motion based on subgroups in lung stereotactic body radiation therapy.

Materials and methods

4DCT image data of 267 tumors from 246 patients were analyzed. The coordinates in the left–right (LR), anterior–posterior (AP), and cranial–caudal (CC) directions of the center of mass (COM) of the gross tumor volumes in 10 phases of 4DCT were measured. The peak‐to‐peak COM displacement in the LR, AP, CC, and 3D directions was calculated. The influence of target‐related and clinical factors on tumor motion was evaluated using multivariate analysis.

Results

The tumor segment location correlated with the tumor motion in each direction. Tumor size was predictive of tumor motion in the 3D (p = 0.023) and AP directions (p = 0.049). The tumor motion for metastatic tumors was smaller than that for primary tumors in the LR (p = 0.019) and AP directions (p = 0.008). The CC motion for pulmonary surgery recipients (3.8 ± 4.5 mm) was less than that for patients who had not undergone surgery (5.6 ± 5.4 mm), and no significant clinical factor was observed. BSA and BMI were positively correlated with the motion in the CC (p = 0.02) and LR directions (p = 0.002).

Conclusion

The tumor segment location was a good predictor of tumor motion. A larger tumor tends to have a smaller motion. Patients with metastatic tumors or those who have undergone pulmonary surgery exhibited smaller and more unpredictable tumor motions, which required individual assessments. Thus, clinical factors can potentially predict tumor motion.

The Hippo pathway regulates density-dependent proliferation of iPSC-derived cardiac myocytes

Inducing cardiac myocytes to proliferate is considered a potential therapy to target heart disease, however, modulating cardiac myocyte proliferation has proven to be a technical challenge. The Hippo pathway is a kinase signaling cascade that regulates cell proliferation during the growth of the heart. Inhibition of the Hippo pathway increases the activation of the transcription factors YAP/TAZ, which translocate to the nucleus and upregulate transcription of pro-proliferative genes. The Hippo pathway regulates the proliferation of cancer cells, pluripotent stem cells, and epithelial cells through a cell-cell contact-dependent manner, however, it is unclear if cell density-dependent cell proliferation is a consistent feature in cardiac myocytes. Here, we used cultured human iPSC-derived cardiac myocytes (hiCMs) as a model system to investigate this concept. hiCMs have a comparable transcriptome to the immature cardiac myocytes that proliferate during heart development in vivo. Our data indicate that a dense syncytium of hiCMs can regain cell cycle activity and YAP expression and activity when plated sparsely or when density is reduced through wounding. We found that combining two small molecules, XMU-MP-1 and S1P, increased YAP activity and further enhanced proliferation of low-density hiCMs. Importantly, these compounds had no effect on hiCMs within a dense syncytium. These data add to a growing body of literature that link Hippo pathway regulation with cardiac myocyte proliferation and demonstrate that regulation is restricted to cells with reduced contact inhibition.

Combined genetic and chemical screens indicate protective potential for EGFR inhibition to cardiomyocytes under hypoxia

The return of blood flow to ischemic heart after myocardial infarction causes ischemia-reperfusion injury. There is a clinical need for novel therapeutic targets to treat myocardial ischemia-reperfusion injury. Here we screened for targets for the treatment of ischemia-reperfusion injury using a combination of shRNA and drug library analyses in HL-1 mouse cardiomyocytes subjected to hypoxia and reoxygenation. The shRNA library included lentiviral constructs targeting 4625 genes and the drug library 689 chemical compounds approved by the Food and Drug Administration (FDA). Data were analyzed using protein-protein interaction and pathway analyses. EGFR inhibition was identified as a cardioprotective mechanism in both approaches. Inhibition of EGFR kinase activity with gefitinib improved cardiomyocyte viability in vitro. In addition, gefitinib preserved cardiac contractility in zebrafish embryos exposed to hypoxia-reoxygenation in vivo. These findings indicate that the EGFR inhibitor gefitinib is a potential candidate for further studies of repurposing the drug for the treatment of myocardial infarction.

Integrated Quantitative Phosphoproteomics and Cell-based Functional Screening Reveals Specific Pathological Cardiac Hypertrophy-related Phosphorylation Sites

Cardiac hypertrophic signaling cascades resulting in heart failure diseases are mediated by protein phosphorylation. Recent developments in mass spectrometry-based phosphoproteomics have led to the identification of thousands of differentially phosphorylated proteins and their phosphorylation sites. However, functional studies of these differentially phosphorylated proteins have not been conducted in a large-scale or high-throughput manner due to a lack of methods capable of revealing the functional relevance of each phosphorylation site. In this study, an integrated approach combining quantitative phosphoproteomics and cell-based functional screening using phosphorylation competition peptides was developed. A pathological cardiac hypertrophy model, junctate-1 transgenic mice and control mice, were analyzed using label-free quantitative phosphoproteomics to identify differentially phosphorylated proteins and sites. A cell-based functional assay system measuring hypertrophic cell growth of neonatal rat ventricle cardiomyocytes (NRVMs) following phenylephrine treatment was applied, and changes in phosphorylation of individual differentially phosphorylated sites were induced by incorporation of phosphorylation competition peptides conjugated with cell-penetrating peptides. Cell-based functional screening against 18 selected phosphorylation sites identified three phosphorylation sites (Ser-98, Ser-179 of Ldb3, and Ser-1146 of palladin) displaying near-complete inhibition of cardiac hypertrophic growth of NRVMs. Changes in phosphorylation levels of Ser-98 and Ser-179 in Ldb3 were further confirmed in NRVMs and other pathological/physiological hypertrophy models, including transverse aortic constriction and swimming models, using site-specific phospho-antibodies. Our integrated approach can be used to identify functionally important phosphorylation sites among differentially phosphorylated sites, and unlike conventional approaches, it is easily applicable for large-scale and/or high-throughput analyses.

Application of Patient-Specific iPSCs for Modelling and Treatment of X-Linked Cardiomyopathies

Inherited cardiomyopathies are among the major causes of heart failure and associated with significant mortality and morbidity. Currently, over 70 genes have been linked to the etiology of various forms of cardiomyopathy, some of which are X-linked. Due to the lack of appropriate cell and animal models, it has been difficult to model these X-linked cardiomyopathies. With the advancement of induced pluripotent stem cell (iPSC) technology, the ability to generate iPSC lines from patients with X-linked cardiomyopathy has facilitated in vitro modelling and drug testing for the condition. Nonetheless, due to the mosaicism of the X-chromosome inactivation, disease phenotypes of X-linked cardiomyopathy in heterozygous females are also usually more heterogeneous, with a broad spectrum of presentation. Recent advancements in iPSC procedures have enabled the isolation of cells with different lyonisation to generate isogenic disease and control cell lines. In this review, we will summarise the current strategies and examples of using an iPSC-based model to study different types of X-linked cardiomyopathy. The potential application of isogenic iPSC lines derived from a female patient with heterozygous Danon disease and drug screening will be demonstrated by our preliminary data. The limitations of an iPSC-derived cardiomyocyte-based platform will also be addressed.

Isolation and Culture of Neonatal Murine Primary Cardiomyocytes

The cardiomyocyte is the main cell type in the heart responsible for its contractile function. Culturing primary cardiomyocytes from mammalian sources to study their function remains challenging as they are terminally differentiated and cease to multiply soon after birth. The major technical hurdles associated with primary cardiomyocyte culture include attaining high yields, obtaining healthy/viable cells that show spontaneous contractions upon culture, and avoiding contamination by non-myocyte cardiac cell types such as fibroblasts and endothelial cells. The yield and the quality of the cardiomyocytes obtained are impacted by a variety of factors, such as the purity of the reagents, composition of the digestion mixture, the digestion conditions, and the temperature of the tissue during different steps of isolation. Here, we provide a simplified workflow to isolate, culture, and maintain neonatal primary cardiomyocytes from rats/mice in culture dishes, which can then be used to study, for instance, cardiac hypertrophy and drug-induced cardiotoxicity. © 2021 Wiley Periodicals LLC. Basic Protocol: Isolation and culture of primary cardiomyocytes from rat/mouse pups Support Protocol: Coating of tissue culture plates with extracellular matrix substrates for efficient cardiomyocyte attachment.

The emerging technology of biohybrid micro-robots: a review

Abstract

In the past few decades, robotics research has witnessed an increasingly high interest in miniaturized, intelligent, and integrated robots. The imperative component of a robot is the actuator that determines its performance. Although traditional rigid drives such as motors and gas engines have shown great prevalence in most macroscale circumstances, the reduction of these drives to the millimeter or even lower scale results in a significant increase in manufacturing difficulty accompanied by a remarkable performance decline. Biohybrid robots driven by living cells can be a potential solution to overcome these drawbacks by benefiting from the intrinsic microscale self-assembly of living tissues and high energy efficiency, which, among other unprecedented properties, also feature flexibility, self-repair, and even multiple degrees of freedom. This paper systematically reviews the development of biohybrid robots. First, the development of biological flexible drivers is introduced while emphasizing on their advantages over traditional drivers. Second, up-to-date works regarding biohybrid robots are reviewed in detail from three aspects: biological driving sources, actuator materials, and structures with associated control methodologies. Finally, the potential future applications and major challenges of biohybrid robots are explored.

Graphic abstract

Rutin Modulates MAPK Pathway Differently from Quercetin in Angiotensin II-Induced H9c2 Cardiomyocyte Hypertrophy

Rutin is a flavonoid with antioxidant property. It has been shown to exert cardioprotection against cardiomyocyte hypertrophy. However, studies regarding its antihypertrophic property are still lacking, whether it demonstrates similar antihypertrophic effect to its metabolite, quercetin. Hence, this study aimed to investigate the effects of both flavonoids on oxidative stress and mitogen-activated protein kinase (MAPK) pathway in H9c2 cardiomyocytes that were exposed to angiotensin II (Ang II) to induce hypertrophy. Cardiomyocytes were exposed to Ang II (600 nM) with or without quercetin (331 μM) or rutin (50 μM) for 24 h. A group given vehicle served as the control. The concentration of the flavonoids was chosen based on the reported effective concentration to reduce cell hypertrophy or cardiac injury in H9c2 cells. Exposure to Ang II increased cell surface area, intracellular superoxide anion level, NADPH oxidase and inducible nitric oxide synthase activities, and reduced cellular superoxide dismutase activity and nitrite level, which were similarly reversed by both rutin and quercetin. Rutin had no significant effects on phosphorylated proteins of extracellular signal-related kinases (ERK1/2) and p38 but downregulated phosphorylated c-Jun N-terminal kinases (JNK1/2), which were induced by Ang II. Quercetin, on the other hand, had significantly downregulated the phosphorylated proteins of ERK1/2, p38, and JNK1/2. The quercetin inhibitory effect on JNK1/2 was stronger than the rutin. In conclusion, both flavonoids afford similar protective effects against Ang II-induced cardiomyocyte hypertrophy, but they differently modulate MAPK pathway.

Selective HDAC8 Inhibition Attenuates Isoproterenol-Induced Cardiac Hypertrophy and Fibrosis via p38 MAPK Pathway

Histone deacetylase (HDAC) expression and enzymatic activity are dysregulated in cardiovascular diseases. Among Class I HDACs, HDAC2 has been reported to play a key role in cardiac hypertrophy; however, the exact function of HDAC8 remains unknown. Here we investigated the role of HDAC8 in cardiac hypertrophy and fibrosis using the isoproterenol-induced cardiac hypertrophy model system.Isoproterenol-infused mice were injected with the HDAC8 selective inhibitor PCI34051 (30 mg kg⁻¹ body weight). Enlarged hearts were assessed by HW/BW ratio, cross-sectional area, and echocardiography. RT-PCR, western blotting, histological analysis, and cell size measurements were performed. To elucidate the role of HDAC8 in cardiac hypertrophy, HDAC8 knockdown and HDAC8 overexpression were also used. Isoproterenol induced HDAC8 mRNA and protein expression in mice and H9c2 cells, while PCI34051 treatment decreased cardiac hypertrophy in isoproterenol-treated mice and H9c2 cells. PCI34051 treatment also reduced the expression of cardiac hypertrophic markers (Nppa, Nppb, and Myh7), transcription factors (Sp1, Gata4, and Gata6), and fibrosis markers (collagen type I, fibronectin, and Ctgf) in isoproterenol-treated mice. HDAC8 overexpression stimulated cardiac hypertrophy in cells, whereas HDAC8 knockdown reversed those effects. HDAC8 selective inhibitor and HDAC8 knockdown reduced the isoproterenol-induced activation of p38 MAPK, whereas HDAC8 overexpression promoted p38 MAPK phosphorylation. Furthermore, p38 MAPK inhibitor SB203580 significantly decreased the levels of p38 MAPK phosphorylation, as well as ANP and BNP protein expression, induced by HDAC8 overexpression.Here we show that inhibition of HDAC8 activity or expression suppresses cardiac hypertrophy and fibrosis. These findings suggest that HDAC8 could be a promising target to treat cardiac hypertrophy and fibrosis by regulating p38 MAPK.

Epitope-directed monoclonal antibody production using a mixed antigen cocktail facilitates antibody characterization and validation

High quality, well-validated antibodies are needed to mitigate irreproducibility and clarify conflicting data in science. We describe an epitope-directed monoclonal antibody (mAb) production method that addresses issues of antibody quality, validation and utility. The workflow is illustrated by generating mAbs against multiple in silico-predicted epitopes on human ankyrin repeat domain 1 (hANKRD1) in a single hybridoma production cycle. Antigenic peptides (13-24 residues long) presented as three-copy inserts on the surface exposed loop of a thioredoxin carrier produced high affinity mAbs that are reactive to native and denatured hANKRD1. ELISA assay miniaturization afforded by novel DEXT microplates allowed rapid hybridoma screening with concomitant epitope identification. Antibodies against spatially distant sites on hANKRD1 facilitated validation schemes applicable to two-site ELISA, western blotting and immunocytochemistry. The use of short antigenic peptides of known sequence facilitated direct epitope mapping crucial for antibody characterization. This robust method motivates its ready adoption for other protein targets.

Recapitulating Cardiac Structure and Function In Vitro from Simple to Complex Engineering

Cardiac tissue engineering aims to generate in vivo-like functional tissue for the study of cardiac development, homeostasis, and regeneration. Since the heart is composed of various types of cells and extracellular matrix with a specific microenvironment, the fabrication of cardiac tissue in vitro requires integrating technologies of cardiac cells, biomaterials, fabrication, and computational modeling to model the complexity of heart tissue. Here, we review the recent progress of engineering techniques from simple to complex for fabricating matured cardiac tissue in vitro. Advancements in cardiomyocytes, extracellular matrix, geometry, and computational modeling will be discussed based on a technology perspective and their use for preparation of functional cardiac tissue. Since the heart is a very complex system at multiscale levels, an understanding of each technique and their interactions would be highly beneficial to the development of a fully functional heart in cardiac tissue engineering.

Multiplexing physical stimulation on single human induced pluripotent stem cell-derived cardiomyocytes for phenotype modulation

Traditional in vitro bioengineering approaches whereby only individual biophysical cues are manipulated at any one time are highly inefficient, falling short when recapitulating the complexity of the cardiac environment. Multiple biophysical cues are present in the native myocardial niche and are essential during development, as well as in maintenance of adult cardiomyocyte (CM) phenotype in both health and disease. This study establishes a novel biofabrication workflow to study and manipulate hiPSC-CMs and to understand how these cells respond to a multiplexed biophysical environment, namely 3D shape and substrate stiffness, at a single cell level. Silicon masters were fabricated and developed to generate inverse patterns of the desired 3D shapes in bas relief, which then were used to mold the designed microwell arrays into a hydrogel. Polyacrylamide (PAAm) was modified with the incorporation of acrylic acid to provide a carboxylic group conjugation site for adhesion motifs, without compromising capacity to modulate stiffness. In this manner, two individual parameters can be finely tuned independently within the hydrogel: the shape of the 3D microwell and its stiffness. The design allows the platform to isolate single hiPSC-CMs to study solely biophysical cues in the absence of cell-cell physical interaction. Under physiologic-like physical conditions (3D shape resembling that of adult CM and 9.83 kPa substrate stiffness that mimics muscle stiffness), isolated single hiPSC-CMs exhibit increased Cx-43 density, cell membrane stiffness and calcium transient amplitude; co-expression of the subpopulation-related MYL2-MYL7 proteins; and higher anisotropism than cells in pathologic-like conditions (flat surface and 112 kPa substrate stiffness). This demonstrates that supplying a physiologic or pathologic microenvironment to an isolated single hiPSC-CM in the absence of any physical cell-to-cell communication in this biofabricated platform leads to a significantly different set of cellular features, thus presenting a differential phenotype. Importantly, this demonstrates the high plasticity of hiPSC-CMs even in isolation. The ability of multiple biophysical cues to significantly influence isolated single hiPSC-CM phenotype and functionality highlights the importance of fine-tuning such cues for specific applications. This has the potential to produce more fit-for-purpose hiPSC-CMs. Further understanding of human cardiac development is enabled by the robust, versatile and reproducible biofabrication techniques applied here. We envision that this system could be easily applied to other tissues and cell types where the influence of cellular shape and stiffness of the surrounding environment is hypothesized to play an important role in physiology.

Amylin deposition activates HIF1α and 6-phosphofructo-2-kinase/fructose-2, 6-biphosphatase 3 (PFKFB3) signaling in failing hearts of non-human primates

Hyperamylinemia induces amylin aggregation and toxicity in the pancreas and contributes to the development of type-2 diabetes (T2D). Cardiac amylin deposition in patients with obesity and T2D was found to accelerate heart dysfunction. Non-human primates (NHPs) have similar genetic, metabolic, and cardiovascular processes as humans. However, the underlying mechanisms of cardiac amylin in NHPs, particularly related to the hypoxia inducible factor (HIF)1α and 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3) signaling pathways, are unknown. Here, we demonstrate that in NHPs, amylin deposition in heart failure (HF) contributes to cardiac dysfunction via activation of HIF1α and PFKFB3 signaling. This was confirmed in two in vitro cardiomyocyte models. Furthermore, alterations of intracellular Ca2+, reactive oxygen species, mitochondrial function, and lactate levels were observed in amylin-treated cells. Our study demonstrates a pathological role for amylin in the activation of HIF1α and PFKFB3 signaling in NHPs with HF, establishing amylin as a promising target for heart disease patients.

Tissue Chips and Microphysiological Systems for Disease Modeling and Drug Testing

Tissue chips (TCs) and microphysiological systems (MPSs) that incorporate human cells are novel platforms to model disease and screen drugs and provide an alternative to traditional animal studies. This review highlights the basic definitions of TCs and MPSs, examines four major organs/tissues, identifies critical parameters for organization and function (tissue organization, blood flow, and physical stresses), reviews current microfluidic approaches to recreate tissues, and discusses current shortcomings and future directions for the development and application of these technologies. The organs emphasized are those involved in the metabolism or excretion of drugs (hepatic and renal systems) and organs sensitive to drug toxicity (cardiovascular system). This article examines the microfluidic/microfabrication approaches for each organ individually and identifies specific examples of TCs. This review will provide an excellent starting point for understanding, designing, and constructing novel TCs for possible integration within MPS.

Interaction of the Joining Region in Junctophilin-2 With the L-Type Ca2+ Channel Is Pivotal for Cardiac Dyad Assembly and Intracellular Ca2+ Dynamics

RATIONALE

Ca2+-induced Ca2+ release (CICR) in normal hearts requires close approximation of L-type calcium channels (LTCCs) within the transverse tubules (T-tubules) and RyR (ryanodine receptors) within the junctional sarcoplasmic reticulum. CICR is disrupted in cardiac hypertrophy and heart failure, which is associated with loss of T-tubules and disruption of cardiac dyads. In these conditions, LTCCs are redistributed from the T-tubules to disrupt CICR. The molecular mechanism responsible for LTCCs recruitment to and from the T-tubules is not well known. JPH (junctophilin) 2 enables close association between T-tubules and the junctional sarcoplasmic reticulum to ensure efficient CICR. JPH2 has a so-called joining region that is located near domains that interact with T-tubular plasma membrane, where LTCCs are housed. The idea that this joining region directly interacts with LTCCs and contributes to LTCC recruitment to T-tubules is unknown.

OBJECTIVE

To determine if the joining region in JPH2 recruits LTCCs to T-tubules through direct molecular interaction in cardiomyocytes to enable efficient CICR.

METHODS AND RESULTS

Modified abundance of JPH2 and redistribution of LTCC were studied in left ventricular hypertrophy in vivo and in cultured adult feline and rat ventricular myocytes. Protein-protein interaction studies showed that the joining region in JPH2 interacts with LTCC-α1C subunit and causes LTCCs distribution to the dyads, where they colocalize with RyRs. A JPH2 with induced mutations in the joining region (mutPG1JPH2) caused T-tubule remodeling and dyad loss, showing that an interaction between LTCC and JPH2 is crucial for T-tubule stabilization. mutPG1JPH2 caused asynchronous Ca2+-release with impaired excitation-contraction coupling after β-adrenergic stimulation. The disturbed Ca2+ regulation in mutPG1JPH2 overexpressing myocytes caused calcium/calmodulin-dependent kinase II activation and altered myocyte bioenergetics.

CONCLUSIONS

The interaction between LTCC and the joining region in JPH2 facilitates dyad assembly and maintains normal CICR in cardiomyocytes.

Three-Week-Old Rabbit Ventricular Cardiomyocytes as a Novel System to Study Cardiac Excitation and EC Coupling

Cardiac arrhythmias significantly contribute to cardiovascular morbidity and mortality. The rabbit heart serves as an accepted model system for studying cardiac cell excitation and arrhythmogenicity. Accordingly, primary cultures of adult rabbit ventricular cardiomyocytes serve as a preferable model to study molecular mechanisms of human cardiac excitation. However, the use of adult rabbit cardiomyocytes is often regarded as excessively costly. Therefore, we developed and characterized a novel low-cost rabbit cardiomyocyte model, namely, 3-week-old ventricular cardiomyocytes (3wRbCMs). Ventricular myocytes were isolated from whole ventricles of 3-week-old New Zealand White rabbits of both sexes by standard enzymatic techniques. Using wheat germ agglutinin, we found a clear T-tubule structure in acutely isolated 3wRbCMs. Cells were adenovirally infected (multiplicity of infection of 10) to express Green Fluorescent Protein (GFP) and cultured for 48 h. The cells showed action potential duration (APD90 = 253 ± 24 ms) and calcium transients similar to adult rabbit cardiomyocytes. Freshly isolated and 48-h-old-cultured cells expressed critical ion channel proteins: calcium voltage-gated channel subunit alpha1 C (Ca_vα1c), sodium voltage-gated channel alpha subunit 5 (Nav1.5), potassium voltage-gated channel subfamily D member 3 (Kv4.3), and subfamily A member 4 (Kv1.4), and also subfamily H member 2 (RERG. Kv11.1), KvLQT1 (K7.1) protein and inward-rectifier potassium channel (Kir2.1). The cells displayed an appropriate electrophysiological phenotype, including fast sodium current (I _Na), transient outward potassium current (I _to), L-type calcium channel peak current (I _Ca,L), rapid and slow components of the delayed rectifier potassium current (I _Kr and I _Ks), and inward rectifier (I _K1). Although expression of the channel proteins and some currents decreased during the 48 h of culturing, we conclude that 3wRbCMs are a new, low-cost alternative to the adult-rabbit-cardiomyocytes system, which allows the investigation of molecular mechanisms of cardiac excitation on morphological, biochemical, genetic, physiological, and biophysical levels.

Sinapic Acid Inhibits Cardiac Hypertrophy via Activation of Mitochondrial Sirt3/SOD2 Signaling in Neonatal Rat Cardiomyocytes

Sinapic acid (SA) is a naturally occurring phenolic compound with antioxidant properties. It also has a wide range of pharmacological properties, such as anti-inflammatory, anticancer, and hepatoprotective properties. The present study aimed to evaluate the potential pharmacological effects of SA against hypertrophic responses in neonatal rat cardiomyocytes. In order to evaluate the preventive effect of SA on cardiac hypertrophy, phenylephrine (PE)-induced hypertrophic cardiomyocytes were treated with subcytotoxic concentrations of SA. SA effectively suppressed hypertrophic responses, such as cell size enlargement, sarcomeric rearrangement, and fetal gene re-expression. In addition, SA significantly inhibited the expression of mitogen-activated protein kinase (MAPK) proteins as pro-hypertrophic factors and protected the mitochondrial functions from hypertrophic stimuli. Notably, SA activated Sirt3, a mitochondrial deacetylase, and SOD2, a mitochondrial antioxidant, in hypertrophic cardiomyocytes. SA also inhibited oxidative stress in hypertrophic cardiomyocytes. However, the protective effect of SA was significantly reduced in Sirt3-silenced hypertrophic cardiomyocytes, indicating that SA exerts its beneficial effect through Sirt3/SOD signaling. In summary, this is the first study to reveal the potential pharmacological action and inhibitory mechanism of SA as an antioxidant against cardiac hypertrophy, suggesting that SA could be utilized for the treatment of cardiac hypertrophy.

Lab-on-a-Chip for Cardiovascular Physiology and Pathology

Lab-on-a-chip technologies have allowed researchers to acquire a flexible, yet relatively inexpensive testbed to study one of the leading causes of death worldwide, cardiovascular disease. Cardiovascular diseases, such as peripheral artery disease, arteriosclerosis, and aortic stenosis, for example, have all been studied by lab-on-a-chip technologies. These technologies allow for the integration of mammalian cells into functional structures that mimic vital organs with geometries comparable to those found in vivo. For this review, we focus on microdevices that have been developed to study cardiovascular physiology and pathology. With these technologies, researchers can better understand the electrical-biomechanical properties unique to cardiomyocytes and better stimulate and understand the influence of blood flow on the human vasculature. Such studies have helped increase our understanding of many cardiovascular diseases in general; as such, we present here a review of the current state of the field and potential for the future.

The effect of tropomyosin variants on cardiomyocyte function and structure that underlie different clinical cardiomyopathy phenotypes

Background - Variants within the alpha-tropomyosin gene (TPM1) cause dominantly inherited cardiomyopathies, including dilated (DCM), hypertrophic (HCM) and restrictive (RCM) cardiomyopathy. Here we investigated whether TPM1 variants observed in DCM and HCM patients affect cardiomyocyte physiology differently. Methods - We identified a large family with DCM carrying a recently identified TPM1 gene variant (T201M) and a child with RCM with compound heterozygote TPM1 variants (E62Q and M281T) whose family members carrying single variants show diastolic dysfunction and HCM. The effects of TPM1 variants (T201M, E62Q or M281T) and of a plasmid containing both the E62Q and M281T variants on single-cell Ca²⁺ transients (CaT) in HL-1 cardiomyocytes were studied. To define toxic threshold levels, we performed dose-dependent transfection of TPM1 variants. In addition, cardiomyocyte structure was studied in human cardiac biopsies with TPM1 variants. Results - Overexpression of TPM1 variants led to time-dependent progressive deterioration of CaT, with the smallest effect seen for E62Q and larger and similar effects seen for the T201M and M281T variants. Overexpression of E62Q/M281T did not exacerbate the effects seen with overexpression of a single TPM1 variant. T201M (DCM) replaced endogenous tropomyosin dose-dependently, while M281T (HCM) did not. Human cardiac biopsies with TPM1 variants revealed loss of sarcomeric structures. Conclusion - All TPM1 variants result in reduced cardiomyocyte CaT amplitudes and loss of sarcomeric structures. These effects may underlie pathophysiology of different cardiomyopathy phenotypes.

Sulfated N-acetylglucosamino-glucuronopyranosyl-arabinopyranan from seafood Amphioctopus neglectus attenuates angiotensin-II prompted cardiac hypertrophy

Angiotensin converting enzyme (ACE) is a multifunctional enzyme involved in translation of angiotensin-I (Ang^I) to vasoconstrictor angiotensin-II (Ang^II). A sulfated N-acetylglucosamino-glucuronopyranosyl-arabinopyranan characterized as poly-[(2-methoxy-β-arabinopyranosyl)-(1 → 3)-(β-glucurono)-(1 → 4)-(2-acetamido-2-deoxy-3,6-di-O-sulfonato-β-glucopyranose)] was purified and reported first time from the edible portion of Amphioctopus neglectus and evaluated for various pharmacological properties. The polysaccharide exhibited potential ACE attenuation property (IC₅₀ 0.11 mg mL^-1), whereas molecular docking simulations displayed its efficient binding at the ACE active site with lesser inhibitory constant (K_i) of 17.36 nM and binding energy (-10.59 kcal mol^-1). The in-vitro analysis showed that the studied polysacharide attenuated Ang^II prompted cardiac hypertrophy at 50 μg mL^-1 in the cardiomyoblast cells, whereas 48% reduction in cellular surface area with extended viability could be correlated with anti-hypertrophic properties of the studied polysaccharide. The sulfated N-acetylglucosamino-glucuronopyranosyl-arabinopyranan purified from A. neglectus could function as a prospective functional lead against the pathophysiological conditions leading to hypertension.

Quantifying drug-induced structural toxicity in hepatocytes and cardiomyocytes derived from hiPSCs using a deep learning method

Cardiac and hepatic toxicity result from induced disruption of the functioning of cardiomyocytes and hepatocytes, respectively, which is tightly related to the organization of their subcellular structures. Cellular structure can be analyzed from microscopy imaging data. However, subtle or complex structural changes that are not easily perceived may be missed by conventional image-analysis techniques. Here we report the evaluation of PhenoTox, an image-based deep-learning method of quantifying drug-induced structural changes using human hepatocytes and cardiomyocytes derived from human induced pluripotent stem cells. We assessed the ability of the deep learning method to detect variations in the organization of cellular structures from images of fixed or live cells. We also evaluated the power and sensitivity of the method for detecting toxic effects of drugs by conducting a set of experiments using known toxicants and other methods of screening for cytotoxic effects. Moreover, we used PhenoTox to characterize the effects of tamoxifen and doxorubicin-which cause liver toxicity-on hepatocytes. PhenoTox revealed differences related to loss of cytochrome P450 3A4 activity, for which it showed greater sensitivity than a caspase 3/7 assay. Finally, PhenoTox detected structural toxicity in cardiomyocytes, which was correlated with contractility defects induced by doxorubicin, erlotinib, and sorafenib. Taken together, the results demonstrated that PhenoTox can capture the subtle morphological changes that are early signs of toxicity in both hepatocytes and cardiomyocytes.

Simultaneous Isolation and Culture of Atrial Myocytes, Ventricular Myocytes, and Non-Myocytes from an Adult Mouse Heart

The isolation and culturing of cardiac myocytes from mice has been essential for furthering the understanding of cardiac physiology and pathophysiology. While isolating myocytes from neonatal mouse hearts is relatively straightforward, myocytes from the adult murine heart are preferred. This is because compared to neonatal cells, adult myocytes more accurately recapitulate cell function as it occurs in the adult heart in vivo. However, it is technically difficult to isolate adult mouse cardiac myocytes in the necessary quantities and viability, which contributes to an experimental impasse. Furthermore, published procedures are specific for the isolation of either atrial or ventricular myocytes at the expense of atrial and ventricular non-myocyte cells. Described here is a detailed method for isolating both atrial and ventricular cardiac myocytes, along with atrial and ventricular non-myocytes, simultaneously from a single mouse heart. Also provided are the details for optimal cell-specific culturing methods, which enhance cell viability and function. This protocol aims not only to expedite the process of adult murine cardiac cell isolation, but also to increase the yield and viability of cells for investigations of atrial and ventricular cardiac cells.

An improved two-step method for extraction and purification of primary cardiomyocytes from neonatal mice

INTRODUCTION

Primary mouse cardiomyocytes are essential tools for cardiovascular pharmacology research at the cellular and molecular levels, but their low viability and low purity have often caused challenges in previous studies. Hence, we developed an improved two-step method for extraction and purification of primary cardiomyocytes from neonatal mice.

METHOD

This method consisted of two steps: 1) isolation and pre-digestion of heart tissues from 1- to 3-day-old C57 neonatal mice and 2) extraction and purification of cardiomyocytes. The traditional method of primary mouse cardiomyocyte isolation was used as the control group to assess the extraction efficiency of cardiomyocytes by the two-step method, and the purity and viability of cardiomyocytes were evaluated by immunofluorescence staining and autonomous beating analysis, respectively.

RESULTS

Compared with the control method, the two-step method enabled acquisition of more cells from mouse hearts (1.28 ± 0.11 × 10⁶vs 0.59 ± 0.15 × 10⁶ cells/heart), and the resulting cells exhibited higher adherence rates and cell purity (93.25 ± 1.69% vs 73.62 ± 9.76%) after 48 h of culture. Moreover, the viability of cardiomyocytes was also evidently higher in the two-step group than in the control group (124.67 ± 10.50 vs 88.50 ± 6.61 beats/min).

DISCUSSION

Compared with the traditional method, the two-step method exhibited significantly better efficiency in extraction of primary cardiomyocytes and yielded cells with greater purity and viability. The two-step method will likely become a standard method for studies based on primary mouse cardiomyocytes in the future.

Loss of function of transcription factor EB remodels lipid metabolism and cell death pathways in the cardiomyocyte

Glucolipotoxicity following nutrient overload causes cardiomyocyte injury by inhibiting TFEB and suppressing lysosomal function. We ascertained whether in addition to the amount, the type of fatty acids (FAs) and duration of FA exposure regulate TFEB action and dictate cardiomyocyte viability. Saturated FA, palmitate, but not polyunsaturated FAs decreased TFEB content in a concentration- and time-dependent manner in cardiomyocytes. Hearts from high-fat high-sucrose diet-fed mice exhibited a temporal decline in nuclear TFEB content with marked elevation of diacylglycerol and triacylglycerol, suggesting that lipid deposition and TFEB loss are concomitant molecular events. Next, we examined the identity of signaling and metabolic pathways engaged by the loss of TFEB action in the cardiomyocyte. Transcriptome analysis in murine cardiomyocytes with targeted deletion of myocyte TFEB (TFEB^-/-) revealed enrichment of differentially expressed genes (DEG) representing pathways of nutrient metabolism, DNA damage and repair, cell death and cardiac function. Strikingly, genes involved in macroautophagy, mitophagy and lysosome function constituted a small portion of DEGs in TFEB^-/- cardiomyocytes. In myoblasts and/or myocytes, nutrient overload-induced lipid droplet accumulation and caspase-3 activation were exacerbated by silencing TFEB or attenuated by overexpressing constitutively active TFEB. The effect of TFEB overexpression were persistent in the presence of Atg7 loss-of-function, signifying that the effect of TFEB in the myocyte is independent of changes in the macroautophagy pathway. In the cardiomyocyte, the non-canonical effect of TFEB to reprogram energy metabolism is more evident than the canonical action of TFEB on lysosomal autophagy. Loss of TFEB function perturbs metabolic pathways in the cardiomyocyte and renders the heart prematurely susceptible to nutrient overload-induced injury.