A systematic literature review of economic evaluations and cost-of-illness studies of inherited cardiomyopathies.

Hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM) are commonly inherited heart conditions associated with a high risk of heart failure and sudden cardiac death. To understand the economic and societal disease burden, this study systematically identified and reviewed cost-of-illness (COI) studies and economic evaluations (EEs) of various interventions for HCM and DCM. A literature search was performed in MEDLINE, EMBASE, NHS EED, EconLit and Web of Science to identify COI studies and EEs published between 1 January 2010 and 28 April 2021. The selection of studies and their critical appraisal were performed jointly by two independent researchers. For the quality assessment, the 'Consensus on Health Economic Criteria' list was used. Two COI studies and 11 EEs were eligible for inclusion. Cost-effectiveness varied among interventions and depended on the targeted patient population. Both COI studies identified only hospitalisation costs in HCM. The mean study quality was high in EEs but low in COI studies. Most studies excluded costs for patients, caregivers and productivity losses. Overall, knowledge of the societal and economic burden of inherited cardiomyopathies is limited. Future research needs to include quality-adjusted life years and a broader range of costs to provide an information base for optimising care for affected patients.

PITX2 induction leads to impaired cardiomyocyte function in arrhythmogenic cardiomyopathy.

Arrhythmogenic cardiomyopathy (ACM) is an inherited progressive disease characterized by electrophysiological and structural remodeling of the ventricles. However, the disease-causing molecular pathways, as a consequence of desmosomal mutations, are poorly understood. Here, we identified a novel missense mutation within desmoplakin in a patient clinically diagnosed with ACM. Using CRISPR-Cas9, we corrected this mutation in patient-derived human induced pluripotent stem cells (hiPSCs) and generated an independent knockin hiPSC line carrying the same mutation. Mutant cardiomyocytes displayed a decline in connexin 43, NaV1.5, and desmosomal proteins, which was accompanied by a prolonged action potential duration. Interestingly, paired-like homeodomain 2 (PITX2), a transcription factor that acts a repressor of connexin 43, NaV1.5, and desmoplakin, was induced in mutant cardiomyocytes. We validated these results in control cardiomyocytes in which PITX2 was either depleted or overexpressed. Importantly, knockdown of PITX2 in patient-derived cardiomyocytes is sufficient to restore the levels of desmoplakin, connexin 43, and NaV1.5.

Characterization of cardiac metabolism in iPSC-derived cardiomyocytes: lessons from maturation and disease modeling.

BACKGROUND: Induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) have emerged as a powerful tool for disease modeling, though their immature nature currently limits translation into clinical practice. Maturation strategies increasingly pay attention to cardiac metabolism because of its pivotal role in cardiomyocyte development and function. Moreover, aberrances in cardiac metabolism are central to the pathogenesis of cardiac disease. Thus, proper modeling of human cardiac disease warrants careful characterization of the metabolic properties of iPSC-CMs. METHODS: Here, we examined the effect of maturation protocols on healthy iPSC-CMs applied in 23 studies and compared fold changes in functional metabolic characteristics to assess the level of maturation. In addition, pathological metabolic remodeling was assessed in 13 iPSC-CM studies that focus on hypertrophic cardiomyopathy (HCM), which is characterized by abnormalities in metabolism. RESULTS: Matured iPSC-CMs were characterized by mitochondrial maturation, increased oxidative capacity and enhanced fatty acid use for energy production. HCM iPSC-CMs presented varying degrees of metabolic remodeling ranging from compensatory to energy depletion stages, likely due to the different types of mutations and clinical phenotypes modeled. HCM further displayed early onset hypertrophy, independent of the type of mutation or disease stage. CONCLUSIONS: Maturation strategies improve the metabolic characteristics of iPSC-CMs, but not to the level of the adult heart. Therefore, a combination of maturation strategies might prove to be more effective. Due to early onset hypertrophy, HCM iPSC-CMs may be less suitable to detect early disease modifiers in HCM and might prove more useful to examine the effects of gene editing and new drugs in advanced disease stages. With this review, we provide an overview of the assays used for characterization of cardiac metabolism in iPSC-CMs and advise on which metabolic assays to include in future maturation and disease modeling studies.

Required GK1 to Suppress Automaticity of iPSC-CMs Depends Strongly on IK1 Model Structure.

Human-induced pluripotent stem cells derived cardiomyocytes (hiPSC-CMs) are a virtually endless source of human cardiomyocytes that may become a great tool for safety pharmacology; however, their electrical phenotype is immature: they show spontaneous action potentials (APs) and an unstable and depolarized resting membrane potential (RMP) because of lack of IK1. Such immaturity hampers their application in assessing drug safety. The electronic overexpression of IK1 (e.g., through the dynamic clamp (DC) technique) is an option to overcome this deficit. In this computational study, we aim to estimate how much IK1 is needed to bring hiPSC-CMs to a stable and hyperpolarized RMP and which mathematical description of IK1 is most suitable for DC experiments. We compared five mature IK1 formulations (Bett, Dhamoon, Ishihara, O'Hara-Rudy, and ten Tusscher) with the native one (Paci), evaluating the main properties (outward peak, degree of rectification), and we quantified their effects on AP features (RMP, V˙max, APD50, APD90 (AP duration at 50 and 90% of repolarization), and APD50/APD90) after including them in the hiPSC-CM mathematical model by Paci. Then, we automatically identified the critical conductance for IK1 ( GK1, critical), the minimally required amount of IK1 suppressing spontaneous activity. Preconditioning the cell model with depolarizing/hyperpolarizing prepulses allowed us to highlight time dependency of the IK1 formulations. Simulations showed that inclusion of mature IK1 formulations resulted in hyperpolarized RMP and higher V˙max, and observed GK1, critical and the effect on AP duration strongly depended on IK1 formulation. Finally, the Ishihara IK1 led to shorter (-16.3%) and prolonged (+6.5%) APD90 in response to hyperpolarizing and depolarizing prepulses, respectively, whereas other models showed negligible effects. Fine-tuning of GK1 is an important step in DC experiments. Our computational work proposes a procedure to automatically identify how much IK1 current is required to inject to stop the spontaneous activity and suggests the use of the Ishihara IK1 model to perform DC experiments in hiPSC-CMs.

The influence of hERG1a and hERG1b isoforms on drug safety screening in iPSC-CMs.

The human Ether-à-go-go Related Gene (hERG) encodes the pore forming subunit of the channel that conducts the rapid delayed rectifier potassium current IKr. IKr drives repolarization in the heart and when IKr is dysfunctional, cardiac repolarization delays, the QT interval on the electrocardiogram (ECG) prolongs and the risk of developing lethal arrhythmias such as Torsade de Pointes (TdP) increases. TdP risk is incorporated in drug safety screening for cardiotoxicity where hERG is the main target since the IKr channels appear highly sensitive to blockage. hERG block is also included as an important read-out in the Comprehensive in Vitro Proarrhythmia Assay (CiPA) initiative which aims to combine in vitro and in silico experiments on induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) to screen for cardiotoxicity. However, the hERG channel has some unique features to consider for drug safety screening, which we will discuss in this study. The hERG channel consists of different isoforms, hERG1a and hERG1b, which individually influence the kinetics of the channel and the drug response in the human heart and in iPSC-CMs. hERG1b is often underappreciated in iPSC-CM studies, drug screening assays and in silico models, and the fact that its contribution might substantially differ between iPSC-CM and healthy but also diseased human heart, adds to this problem. In this study we show that the activation kinetics in iPSC-CMs resemble hERG1b kinetics using Cs+ as a charge carrier. Not including hERG1b in drug safety testing might underestimate the actual role of hERG1b in repolarization and drug response, and might lead to inappropriate conclusions. We stress to focus more on including hERG1b in drug safety testing concerning IKr.

The immature electrophysiological phenotype of iPSC-CMs still hampers in vitro drug screening: Special focus on IK1.

Preclinical drug screens are not based on human physiology, possibly complicating predictions on cardiotoxicity. Drug screening can be humanised with in vitro assays using human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs). However, in contrast to adult ventricular cardiomyocytes, iPSC-CMs beat spontaneously due to presence of the pacemaking current If and reduced densities of the hyperpolarising current IK1. In adult cardiomyocytes, IK1 finalises repolarisation by stabilising the resting membrane potential while also maintaining excitability. The reduced IK1 density contributes to proarrhythmic traits in iPSC-CMs, which leads to an electrophysiological phenotype that might bias drug responses. The proarrhythmic traits can be suppressed by increasing IK1 in a balanced manner. We systematically evaluated all studies that report strategies to mature iPSC-CMs and found that only few studies report IK1 current densities. Furthermore, these studies did not succeed in establishing sufficient IK1 levels as they either added too little or too much IK1. We conclude that reduced densities of IK1 remain a major flaw in iPSC-CMs, which hampers their use for in vitro drug screening.

3D bioprinting of methacrylated hyaluronic acid (MeHA) hydrogel with intrinsic osteogenicity.

In bone regenerative medicine there is a need for suitable bone substitutes. Hydrogels have excellent biocompatible and biodegradable characteristics, but their visco-elastic properties limit their applicability, especially with respect to 3D bioprinting. In this study, we modified the naturally occurring extracellular matrix glycosaminoglycan hyaluronic acid (HA), in order to yield photo-crosslinkable hydrogels with increased mechanical stiffness and long-term stability, and with minimal decrease in cytocompatibility. Application of these tailor-made methacrylated hyaluronic acid (MeHA) gels for bone tissue engineering and 3D bioprinting was the subject of investigation. Visco-elastic properties of MeHA gels, measured by rheology and dynamic mechanical analysis, showed that irradiation of the hydrogels with UV light led to increased storage moduli and elastic moduli, indicating increasing gel rigidity. Subsequently, human bone marrow derived mesenchymal stromal cells (MSCs) were incorporated into MeHA hydrogels, and cell viability remained 64.4% after 21 days of culture. Osteogenic differentiation of MSCs occurred spontaneously in hydrogels with high concentrations of MeHA polymer, in absence of additional osteogenic stimuli. Addition of bone morphogenetic protein-2 (BMP-2) to the culture medium further increased osteogenic differentiation, as evidenced by increased matrix mineralisation. MeHA hydrogels demonstrated to be suitable for 3D bioprinting, and were printed into porous and anatomically shaped scaffolds. Taken together, photosensitive MeHA-based hydrogels fulfilled our criteria for cellular bioprinted bone constructs within a narrow window of concentration.

A Hybrid Model for Safety Pharmacology on an Automated Patch Clamp Platform: Using Dynamic Clamp to Join iPSC-Derived Cardiomyocytes and Simulations of Ik1 Ion Channels in Real-Time.

An important aspect of the Comprehensive In Vitro Proarrhythmia Assay (CiPA) proposal is the use of human stem cell-derived cardiomyocytes and the confirmation of their predictive power in drug safety assays. The benefits of this cell source are clear; drugs can be tested in vitro on human cardiomyocytes, with patient-specific genotypes if needed, and differentiation efficiencies are generally excellent, resulting in a virtually limitless supply of cardiomyocytes. There are, however, several challenges that will have to be surmounted before successful establishment of hSC-CMs as an all-round predictive model for drug safety assays. An important factor is the relative electrophysiological immaturity of hSC-CMs, which limits arrhythmic responses to unsafe drugs that are pro-arrhythmic in humans. Potentially, immaturity may be improved functionally by creation of hybrid models, in which the dynamic clamp technique joins simulations of lacking cardiac ion channels (e.g., IK1) with hSC-CMs in real-time during patch clamp experiments. This approach has been used successfully in manual patch clamp experiments, but throughput is low. In this study, we combined dynamic clamp with automated patch clamp of iPSC-CMs in current clamp mode, and demonstrate that IK1 conductance can be added to iPSC-CMs on an automated patch clamp platform, resulting in an improved electrophysiological maturity.