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.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-03021-9.

Gender differences in pursuing leadership positions in the Netherlands; a study in cardiovascular PhD candidates

Background

Gender studies demonstrate that more balance in gender within research teams improves performance and output. In the Netherlands, (bio)medical master programs currently enroll more women than men, but scientific leadership positions are still mainly occupied by men. Women tend to refrain from academic careers – referred to as the “leaking pipeline phenomenon” – and reasons are e.g. family planning or glass-ceiling. Women start working part-time even before family planning comes into play. Moreover, more agentic character traits are associated with the male gender and success than communal traits, which are more associated with the female gender.

Purpose

To be able to promote academic careers amongst women, we have to know their intrinsic motivation and adapt the initiatives accordingly. Therefore, we created a questionnaire to evaluate the intrinsic motivation of (bio)medical PhD candidates on pursuing a leadership position.

Methods

In this study, 143 PhD candidates (68% female) of Dutch cardiovascular research programs participated in an online questionnaire, which was not mentioned to be used for gender studies.

Results

Our data shows that less female cardiovascular PhD candidates in the Netherlands aim at or can imagine having a leadership position – defined as full professor, dean, corporate executive officer, (medical) group leader etc. – in the future compared to male candidates (29% female versus 46% male and 40% female versus 63% male, respectively). In men, this decision seemed to be less influenced by their wish to have children, but both men and women would like to be able to work part-time in the future. When asked whether a certain initiative would positively influence their decision to pursue a leadership position, women reported that position certainty and alternative measures of impact would motivate them to pursue leadership positions rather than gender-specific initiatives. Men, in turn, would be motivated by an adequate mentor, which seems to lack in the current system (40%). Free day care for children would persuade 67% of women and 43% of men and possibilities for a part-time position would persuade 73% of women and 59% of men to pursue a leadership position. When asked, which of their own character traits would benefit or hamper someone in a leadership position, agentic traits were seen as more beneficial for a leadership position, but also more hampering in both genders.

Conclusion

Less female cardiovascular PhD candidates in the Netherlands aim at or can imagine having a leadership position compared to male candidates. However, women reported that position certainty and alternatives to the impact factor would motivate them to pursue a leadership position. Possible part-time work would persuade both genders in pursuing a leadership position. Additionally, agentic character traits are seen as beneficial for a leadership position amongst these candidates, but simultaneously thought to be hampering.

Funding Acknowledgement

Type of funding source: Public hospital(s). Main funding source(s): University Medical Center Utrecht

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 I_K1. Such immaturity hampers their application in assessing drug safety. The electronic overexpression of I_K1 (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 I_K1 is needed to bring hiPSC-CMs to a stable and hyperpolarized RMP and which mathematical description of I_K1 is most suitable for DC experiments. We compared five mature I_K1 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 I_K1 ( G_{K1, critical}), the minimally required amount of I_K1 suppressing spontaneous activity. Preconditioning the cell model with depolarizing/hyperpolarizing prepulses allowed us to highlight time dependency of the I_K1 formulations. Simulations showed that inclusion of mature I_K1 formulations resulted in hyperpolarized RMP and higher V˙max, and observed G_{K1, critical} and the effect on AP duration strongly depended on I_K1 formulation. Finally, the Ishihara I_K1 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 G_K1 is an important step in DC experiments. Our computational work proposes a procedure to automatically identify how much I_K1 current is required to inject to stop the spontaneous activity and suggests the use of the Ishihara I_K1 model to perform DC experiments in hiPSC-CMs.

Abstract 786: A Novel Desmoplakin Mutation Contributes to Arrhythmogenic Cardiomyopathy

Genetic alterations in desmosomal genes are associated with arrhythmogenic cardiomyopathy (ACM). This condition is characterized by sudden cardiac death, severe arrhythmias, and the presence of fibro-fatty patches within the myocardium. Despite the fact that the pathophysiology of ACM is well described, the molecular mechanisms underlying disease onset and progression are poorly understood.

In an effort to identify disease-driving mechanisms we obtained induced pluripotent stem cells (hIPS) from a patient harboring a novel heterozygous mutation in desmoplakin ( DSP p.Tyr1188His/WT ), which we corrected to yield an isogenic control. hIPS cells carrying a known pathogenic mutation in desmoplakin ( DSP p.Arg1113X/WT ) served as a positive control. Gene expression analyses of DSP p.Tyr1188His/WT hIPS-derived cardiomyocytes revealed a dysregulation of desmosomal and ion channel-related genes. At the functional level we observed a prolonged action potential duration in DSP p.Tyr1188His/WT cardiomyocytes. Importantly, we validated these findings in an independent knock-in line carrying the same heterozygous ( DSP p.Tyr1188His/WT ) mutation. To study the in vivo relevance we additionally generated two corresponding mouse models harboring the mouse equivalent of the human desmoplakin mutations in the endogenous locus ( Dsp p.Tyr1200His/WT and Dsp p.Arg1125X/WT ). Both lines show altered connexin 43, phospholamban and Na V 1.5 expression levels under baseline conditions, recapitulating the changes observed in the hIPS-derived cardiomyocytes. Moreover, Fos- and RhoA-signaling pathways are enriched in these mice compared with wildtype littermates. Since exercise can be a trigger for the development of ACM, we are currently in the process of examining the effect of intense swimming exercise in the models.

We show that the DSP p.Tyr1188His/WT mutation causes cellular changes linked to ACM pathogenesis, indicating this mutation to be disease-driving. Moreover, our novel mouse models of ACM recapitulate the findings observed in our human models and show key hallmarks of ACM disease progression. Future studies will focus on the underlying pathogenic mechanisms in the presented models.

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 I_Kr. I_Kr drives repolarization in the heart and when I_Kr 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 I_Kr 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 I_Kr.

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., I_K1) 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 I_K1 conductance can be added to iPSC-CMs on an automated patch clamp platform, resulting in an improved electrophysiological maturity.

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 I_f and reduced densities of the hyperpolarising current I_K1. In adult cardiomyocytes, I_K1 finalises repolarisation by stabilising the resting membrane potential while also maintaining excitability. The reduced I_K1 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 I_K1 in a balanced manner. We systematically evaluated all studies that report strategies to mature iPSC-CMs and found that only few studies report I_K1 current densities. Furthermore, these studies did not succeed in establishing sufficient I_K1 levels as they either added too little or too much I_K1. We conclude that reduced densities of I_K1 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.