Generation of patient-specific induced pluripotent stem cell lines from one patient with Jervell and Lange-Nielsen syndrome, one with type 1 long QT syndrome and two healthy relatives

The effects of inflammation on connexin 43 in chronic Chagas disease cardiomyopathy

Background

Cardiac arrhythmias are the main cause of sudden death due to Chronic Chagasic Cardiomyopathy (CCC). Here we investigated alterations in connexin 43 (Cx43) expression and phosphorylation in cardiomyocytes as well as associations with cardiac arrhythmias in CCC.

Methods

C57Bl/6 mice infected with Trypanosoma cruzi underwent cardiac evaluations at 6 and 12 months after infection via treadmill testing and EKG. Histopathology, cytokine gene expression, and distribution of total Cx43 and its phosphorylated forms Cx43S368 and Cx43S325/328/330 were investigated. Human heart samples obtained from subjects with CCC were submitted to immunofluorescence analysis. In vitro simulation of a pro-inflammatory microenvironment (IL-1β, TNF, and IFN-γ) was performed in H9c2 cells and iPSC-derived cardiomyocytes to evaluate Cx43 distribution, action potential duration, and Lucifer Yellow dye transfer.

Results

Mice chronically infected with T. cruzi exhibited impaired cardiac function associated with increased inflammation, fibrosis and upregulated IL-1β, TNF, and IFN-γ gene expression. Confocal microscopy revealed altered total Cx43, Cx43S368 and Cx43S325/328/330 localization and phosphorylation patterns in CCC, with dispersed staining outside the intercalated disc areas, i.e., in lateral membranes and the cytoplasm. Reduced co-localization of total Cx43 and N-cadherin was observed in the intercalated discs of CCC mouse hearts compared to controls. Similar results were obtained in human CCC heart samples, which showed Cx43 distribution outside the intercalated discs. Stimulation of human iPSC-derived cardiomyocytes or H9c2 cells with IL-1β, TNF, and IFN-γ induced alterations in Cx43 localization, reduced action potential duration and dye transfer between adjacent cells.

Conclusion

Heart inflammation in CCC affects the distribution and phosphorylation pattern of Cx43, which may contribute to the generation of conduction disturbances in Chagas disease.

Action potential variability in human pluripotent stem cell-derived cardiomyocytes obtained from healthy donors

Human pluripotent stem cells (PSC) have been used for disease modelling, after differentiation into the desired cell type. Electrophysiologic properties of cardiomyocytes derived from pluripotent stem cells are extensively used to model cardiac arrhythmias, in cardiomyopathies and channelopathies. This requires strict control of the multiple variables that can influence the electrical properties of these cells. In this article, we report the action potential variability of 780 cardiomyocytes derived from pluripotent stem cells obtained from six healthy donors. We analyze the overall distribution of action potential (AP) data, the distribution of action potential data per cell line, per differentiation protocol and batch. This analysis indicates that even using the same cell line and differentiation protocol, the differentiation batch still affects the results. This variability has important implications in modeling arrhythmias and imputing pathogenicity to variants encountered in patients with arrhythmic diseases. We conclude that even when using isogenic cell lines to ascertain pathogenicity to variants associated to arrythmias one should use cardiomyocytes derived from pluripotent stem cells using the same differentiation protocol and batch and pace the cells or use only cells that have very similar spontaneous beat rates. Otherwise, one may find phenotypic variability that is not attributable to pathogenic variants.

Chromosomal aberrations after induced pluripotent stem cells reprogramming

Induced pluripotent stem cells (iPSCs) are generated from adult cells that have been reprogrammed to pluripotency. However, in vitro cultivation and genetic reprogramming increase genetic instability, which could result in chromosomal abnormalities. Maintenance of genetic stability after reprogramming is required for possible experimental and clinical applications. The aim of this study was to analyze chromosomal alterations by using the G-banding karyotyping method applied to 97 samples from 38 iPSC cell lines generated from peripheral blood or Wharton’s jelly. Samples from patients with long QT syndrome, Jervell and Lange-Nielsen syndrome and amyotrophic lateral sclerosis and from normal individuals revealed the following chromosomal alterations: acentric fragments, chromosomal fusions, premature centromere divisions, double minutes, radial figures, ring chromosomes, polyploidies, inversions and trisomies. An analysis of two samples generated from Wharton’s jelly before and after reprogramming showed that abnormal clones can emerge or be selected and generate an altered lineage. IPSC lines may show clonal and nonclonal chromosomal aberrations in several passages (from P6 to P34), but these aberrations are more common in later passages. Many important chromosomal aberrations were detected, showing that G-banding is very useful for evaluating genetic instability with important repercussions for the application of iPSC lines.

Establishment of a heart-on-a-chip microdevice based on human iPS cells for the evaluation of human heart tissue function

Human iPS cell (iPSC)-derived cardiomyocytes (CMs) hold promise for drug discovery for heart diseases and cardiac toxicity tests. To utilize human iPSC-derived CMs, the establishment of three-dimensional (3D) heart tissues from iPSC-derived CMs and other heart cells, and a sensitive bioassay system to depict physiological heart function are anticipated. We have developed a heart-on-a-chip microdevice (HMD) as a novel system consisting of dynamic culture-based 3D cardiac microtissues derived from human iPSCs and microelectromechanical system (MEMS)-based microfluidic chips. The HMDs could visualize the kinetics of cardiac microtissue pulsations by monitoring particle displacement, which enabled us to quantify the physiological parameters, including fluidic output, pressure, and force. The HMDs demonstrated a strong correlation between particle displacement and the frequency of external electrical stimulation. The transition patterns were validated by a previously reported versatile video-based system to evaluate contractile function. The patterns are also consistent with oscillations of intracellular calcium ion concentration of CMs, which is a fundamental biological component of CM contraction. The HMDs showed a pharmacological response to isoproterenol, a β-adrenoceptor agonist, that resulted in a strong correlation between beating rate and particle displacement. Thus, we have validated the basic performance of HMDs as a resource for human iPSC-based pharmacological investigations.

Establishment of a heart-on-a-chip microdevice based on human iPS cells for the evaluation of human heart tissue function

Human iPS cell (iPSC)-derived cardiomyocytes (CMs) hold promise for drug discovery for heart diseases and cardiac toxicity tests. To utilize human iPSC-derived CMs, the establishment of three-dimensional (3D) heart tissues from iPSC-derived CMs and other heart cells, and a sensitive bioassay system to depict physiological heart function are anticipated. We have developed a heart-on-a-chip microdevice (HMD) as a novel system consisting of dynamic culture-based 3D cardiac microtissues derived from human iPSCs and microelectromechanical system (MEMS)-based microfluidic chips. The HMDs could visualize the kinetics of cardiac microtissue pulsations by monitoring particle displacement, which enabled us to quantify the physiological parameters, including fluidic output, pressure, and force. The HMDs demonstrated a strong correlation between particle displacement and the frequency of external electrical stimulation. The transition patterns were validated by a previously reported versatile video-based system to evaluate contractile function. The patterns are also consistent with oscillations of intracellular calcium ion concentration of CMs, which is a fundamental biological component of CM contraction. The HMDs showed a pharmacological response to isoproterenol, a β-adrenoceptor agonist, that resulted in a strong correlation between beating rate and particle displacement. Thus, we have validated the basic performance of HMDs as a resource for human iPSC-based pharmacological investigations.

Extracellular Vesicles Derived from Induced Pluripotent Stem Cells Promote Renoprotection in Acute Kidney Injury Model

Induced pluripotent stem cells (iPSC) have been the focus of several studies due to their wide range of application, including in cellular therapy. The use of iPSC in regenerative medicine is limited by their tumorigenic potential. Extracellular vesicles (EV) derived from stem cells have been shown to support renal recovery after injury. However, no investigation has explored the potential of iPSC-EV in the treatment of kidney diseases. To evaluate this potential, we submitted renal tubule cells to hypoxia-reoxygenation injury, and we analyzed cell death rate and changes in functional mitochondria mass. An in vivo model of ischemia-reperfusion injury was used to evaluate morphological and functional alterations. Gene array profile was applied to investigate the mechanism involved in iPSC-EV effects. In addition, EV derived from adipose mesenchymal cells (ASC-EV) were also used to compare the potential of iPSC-EV in support of tissue recovery. The results showed that iPSC-EV were capable of reducing cell death and inflammatory response with similar efficacy than ASC-EV. Moreover, iPSC-EV protected functional mitochondria and regulated several genes associated with oxidative stress. Taken together, these results show that iPSC can be an alternative source of EV in the treatment of different aspects of kidney disease.

Pathogenic mechanism and gene correction for LQTS-causing double mutations in KCNQ1 using a pluripotent stem cell model

AIMS

To establish a KCNQ1 mutant-specific induced pluripotent stem cell (iPSC) model of a Chinese inherited long QT syndrome (LQTS) patient and to explore the pathogenesis of KCNQ1 mutations.

METHODS AND RESULTS

(1) Two patient-specific iPSC lines from the proband were obtained. (2) The experiments produced spontaneously beating cardiomyocytes (CMs) from patient iPSCs. Splicing mutation c. 605-2A > G in iPSC-derived cardiomyocytes (iPSC-CMs) resulted in the skipping of exon 4, exons 3-4, or exons 3-6 in KCNQ1 transcription what was observed in the patient's peripheral leukocytes. (3) Action potential duration (APD) at 50% and 90% repolarization (APD50 and APD90) of the patient's iPSC-derived ventricular-like-CMs was significantly longer than that of the control. Moreover, early after depolarization (EAD) and coupled beats were observed only in L1-iPSC-CMs. (4) A c.815G > A corrected iPSC line was obtained by using the clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR associated protein 9 (Cas9) system.

CONCLUSION

(1) Cardiomyocytes with spontaneous pulsation were successfully differentiated from LQTS patient-specific iPSC lines. (2) For KCNQ1 splicing mutations, there is a chance that splicing patterns in peripheral leukocytes are similar to that in patient iPSC-CMs. (3) The truncated KCNQ1 proteins induced by such splicing mutation might cause Iks decrease, which in turn produced APD prolongation and triggered activities. (4) Our data showed that CRISPR-Cas9 system could be used to rescue the LQTS-related mutations.

Long QT Syndrome Modelling with Cardiomyocytes Derived from Human-induced Pluripotent Stem Cells

Long QT syndrome (LQTS) is a potentially severe arrhythmogenic disorder, associated with a prolonged QT interval and sudden death, caused by mutations in key genes regulating cardiac electrophysiology. Current strategies to study LQTS in vitro include heterologous systems or animal models. Despite their value, the overwhelming power of genetic tools has exposed the many limitations of these technologies. In 2010, human-induced pluripotent stem cells (hiPSCs) revolutionised the field and allowed scientists to study in vitro some of the disease traits of LQTS on hiPSC-derived cardiomyocytes (hiPSC-CMs) from LQTS patients. In this concise review we present how the hiPSC technology has been used to model three main forms of LQTS and the severe form of LQTS associated with mutations in calmodulin. We also introduce some of the most recent challenges that must be tackled in the upcoming years to successfully shift hiPSC-CMs from powerful in vitro disease modelling tools into assets to improve risk stratification and clinical decision-making.