HOIL-1L deficiency was recently reported to be one of the causes of myopathy and dilated cardiomyopathy (DCM). However, the mechanisms by which myopathy and DCM develop have not been clearly ...elucidated. Here, we sought to elucidate these mechanisms using the murine myoblast cell line C2C12 and disease-specific human induced pluripotent stem cells (hiPSCs). Myotubes differentiated from HOIL-1L-KO C2C12 cells exhibited deteriorated differentiation and mitotic cell accumulation. CMs differentiated from patient-derived hiPSCs had an abnormal morphology with a larger size and were excessively multinucleated compared with CMs differentiated from control hiPSCs. Further analysis of hiPSC-derived CMs showed that HOIL-1L deficiency caused cell cycle alteration and mitotic cell accumulation. These results demonstrate that abnormal cell maturation possibly contribute to the development of myopathy and DCM. In conclusion, HOIL-1L is an important intrinsic regulator of cell cycle-related myotube and CM maturation and cell proliferation.
Duchenne muscular dystrophy (DMD) is the most common and severe form of muscular dystrophy. The major symptoms of this condition are walking difficulties, dyspnea caused by progressive skeletal ...muscle weakness, and cardiomyopathy. Recent advances in ventilator support devices have dramatically decreased mortality caused by respiratory distress. Consequently, cardiomyopathy resulting in heart failure is currently the major cause of death among DMD patients. One mechanism by which skeletal muscle is damaged in DMD patients involves elevation of the intracellular Ca2+ concentration. By contrast, the mechanisms underlying the development of cardiomyopathy are unclear. To investigate this, we examined the intracellular Ca2+ concentration and calcium transients in cardiomyocytes differentiated from human induced pluripotent stem cells (hiPSCs). hiPSCs were derived from a DMD patient (DMD-hiPSCs), in whom exon 44 of the gene encoding dystrophin was deleted, and from his parents (control-hiPSCs), who did not carry this mutation. The intracellular Ca2+ concentration was measured using the fluorescent indicator indo-1. The fluorescence ratio (410/490 nm) of indo-1 at rest (R0), the peak of this ratio (Rmax), and the amplitude (Rmax-R0) were significantly higher in cardiomyocytes differentiated from DMD-hiPSCs than in those differentiated from control-hiPSCs. Moreover, mechanical stretching significantly increased the intracellular Ca2+ concentration in cardiomyocytes differentiated from DMD-hiPSCs, but not in those differentiated from control-hiPSCs. These findings indicate that elevation of the intracellular Ca2+ concentration can cause cardiac damage leading to cardiomyopathy in DMD patients.
Premature cardiac myocytes derived from human induced pluripotent stem cells (hiPSC-CMs) show heterogeneous action potentials (APs), probably due to different expression patterns of membrane ionic ...currents. We developed a method for determining expression patterns of functional channels in terms of whole-cell ionic conductance (G
) using individual spontaneous AP configurations. It has been suggested that apparently identical AP configurations can be obtained using different sets of ionic currents in mathematical models of cardiac membrane excitation. If so, the inverse problem of G
estimation might not be solved. We computationally tested the feasibility of the gradient-based optimization method. For a realistic examination, conventional 'cell-specific models' were prepared by superimposing the model output of AP on each experimental AP recorded by conventional manual adjustment of G
s of the baseline model. G
s of 4-6 major ionic currents of the 'cell-specific models' were randomized within a range of ± 5-15% and used as an initial parameter set for the gradient-based automatic G
s recovery by decreasing the mean square error (MSE) between the target and model output. Plotting all data points of the MSE-G
relationship during optimization revealed progressive convergence of the randomized population of G
s to the original value of the cell-specific model with decreasing MSE. The absence of any other local minimum in the global search space was confirmed by mapping the MSE by randomizing G
s over a range of 0.1-10 times the control. No additional local minimum MSE was obvious in the whole parameter space, in addition to the global minimum of MSE at the default model parameter.
For long QT syndrome (LQTS), recent progress in genome-sequencing technologies enabled the identification of rare genomic variants with diagnostic, prognostic, and therapeutic implications. However, ...pathogenic stratification of the identified variants remains challenging, especially in variants of uncertain significance. This study aimed to propose a phenotypic cell-based diagnostic assay for identifying LQTS to recognize pathogenic variants in a high-throughput manner suitable for screening. We investigated the response of LQT2-induced pluripotent stem cell (iPSC)-derived cardiomyocytes (iPSC-CMs) following IKr blockade using a multi-electrode array, finding that the response to IKr blockade was significantly smaller than in Control-iPSC-CMs. Furthermore, we found that LQT1-iPSC-CMs and LQT3-iPSC-CMs could be distinguished from Control-iPSC-CMs by IKs blockade and INa blockade, respectively. This strategy might be helpful in compensating for the shortcomings of genetic testing of LQTS patients.
•IKs blockade showed a smaller response of delayed repolarization in LQT1-iPSC-CMs•IKr blockade showed a smaller response of delayed repolarization in LQT2-iPSC-CMs•INa blockade markedly ameliorated prolonged repolarization in LQT3-iPSC-CMs•Ion-channel blockade response distinguished LQTS subtypes with high accuracy
The methods presented by the authors allowed recognition of long QT syndrome (LQTS) subtypes 1, 2, and 3 using specific ion-channel current blockade with a combination of patient-derived iPSCs and a multi-electrode array system. This strategy might potentially compensate for the shortcomings of genetic testing for LQTS, especially in patients who have variants of unknown significance or no identified mutations.
Pediatric pulmonary hypertension after surgery for congenital heart disease is a significant complication. We present a case of living-donor lung transplantation for a 12-year-old girl with pulmonary ...hypertension after surgical repair of transposition of great arteries. Despite repairing the transposition of great arteries, her growth was severely restricted because of progressive pulmonary hypertension; thus, lung transplantation was discussed. Standard bilateral lobar transplantation seemed unfeasible due to oversized grafts, so we performed a single lobar transplantation. Unexpectedly, she developed complications and died 3 months postoperatively despite another emergent lobar transplantation. We discussed the challenges and potential solutions regarding lobar size mismatching.
Using curriculum vitae (CVs) or Short Bios in published resources such as the Internet enables us to analyze many issues concerning researchers’ careers. However, analysis of CVs or Short Bios ...concerning researchers’ life history, such as movement between countries, has rarely been conducted. In this paper, we pursue two purposes: to demonstrate which conditions (citation impact, countries or sectors) are favorable for the analysis, and to show structures of production of highly cited papers. To grasp more obvious tendencies, we compare two “extreme” samples: highly cited and uncited papers. First, we assess the identification rates of researchers’ origin broken down by researchers’ affiliation (countries and sectors). Then, we analyze the influence of these researchers’ international movement based on their origin. The results show the full landscape of the movement’s influence on national publication, the characteristics of each country in terms of researchers’ countries of origin and the research experience of both internationally moved and domestic researchers. Moreover, we analyze the contributions of researchers who returned from abroad to their home countries. Finally, we assess the limitations of our research method and the topic to be addressed concerning this method.
Long QT syndrome is a lethal arrhythmic disorder caused by mutations in genes encoding ion channels and related proteins. Recent advances in genome analysis technologies have raised the issue of ...interpreting genetic variants of unknown significance. Since human induced pluripotent stem（iPS）cell models mimic the phenotypes of diseases, they may play an important role in solving problems associated with genotype-phenotype mismatch. We have shown that disease-specific iPS cell-derived cardiomyocytes（iPSC-CMs）differentially respond to specific ion-channel blockers, reflecting ion channel abnormalities. These results indicate that this strategy may enable us to detect abnormal channels based on the phenotype of patient-specific iPSC-CMs. This method may also be useful in diagnosing cases where pathogenic genetic mutations cannot be identified. In addition, iPSC-CMs are being studied as an experimental model for the development of therapies for hereditary arrhythmias. Here, we discuss the latest iPSC technologies related to hereditary arrhythmias.
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