GJB4 encodes a transmembrane connexin protein (Cx30.3) that is a component of gap junctions. This study investigated whether GJB4 plays an important role in human heart disease and function.
We ...examined a patient and her older brother who both presented with complicated severe hypertrophic cardiomyopathy (HCM) and whose parents are healthy married cousins. The gene exome analysis showed 340 single nucleotide polymorphisms (SNPs) that caused amino acid changes for which the patient was homozygous and both parents were heterozygous. After excluding all known common (>10%) SNP gene mutations, the gene for GJB4 was the only identified gene that is possibly associated with cardiac muscle. The resultant E204A substitution exists in the 4th transmembrane domain. GJB4-E204A impaired the binding with gap junction protein A1 (GJA1) compared with GJB4-WT. The expression of GJB4 was induced in rat disease models of left and right ventricle hypertrophy and mouse disease models of adriamycin-induced cardiomyopathy and myocardial infarction, while it was not detected at all in control. An immunohistochemical study was performed for autopsied human hearts and the explanted heart of the patient. GJB4 was expressed and colocalized with GJA1 in intercalated discs in human diseased hearts, which was extensively enhanced in the explanted heart of the patient. The abnormal expression and localization of GJB4 were observed in beating spheres of patient's induced pluripotent stem cell (iPSC)-derived cardiomyocytes (CMs). We generated knockout zebrafish of GJB4 by CRISPR/Cas9 and the endodiastolic volume and the ventricular ejection fraction were significantly lower in GJB4-deficient than in wild-type zebrafish at five days post-fertilization.
These results indicate both that GJB4 is defined as a new connexin in diseased hearts, of which mutation can cause a familial form of HCM, and that GJB4 may be a new target for the treatment of cardiac hypertrophy and dysfunction.
Human induced pluripotent stem cells (hiPSCs) offer a unique opportunity for disease modeling. However, it is not invariably successful to recapitulate the disease phenotype because of the immaturity ...of hiPSC-derived cardiomyocytes (hiPSC-CMs). The purpose of this study was to establish and analyze iPSC-based model of catecholaminergic polymorphic ventricular tachycardia (CPVT), which is characterized by adrenergically mediated lethal arrhythmias, more precisely using electrical pacing that could promote the development of new pharmacotherapies.
We generated hiPSCs from a 37-year-old CPVT patient and differentiated them into cardiomyocytes. Under spontaneous beating conditions, no significant difference was found in the timing irregularity of spontaneous Ca2+ transients between control- and CPVT-hiPSC-CMs. Using Ca2+ imaging at 1 Hz electrical field stimulation, isoproterenol induced an abnormal diastolic Ca2+ increase more frequently in CPVT- than in control-hiPSC-CMs (control 12% vs. CPVT 43%, p<0.05). Action potential recordings of spontaneous beating hiPSC-CMs revealed no significant difference in the frequency of delayed afterdepolarizations (DADs) between control and CPVT cells. After isoproterenol application with pacing at 1 Hz, 87.5% of CPVT-hiPSC-CMs developed DADs, compared to 30% of control-hiPSC-CMs (p<0.05). Pre-incubation with 10 μM S107, which stabilizes the closed state of the ryanodine receptor 2, significantly decreased the percentage of CPVT-hiPSC-CMs presenting DADs to 25% (p<0.05).
We recapitulated the electrophysiological features of CPVT-derived hiPSC-CMs using electrical pacing. The development of DADs in the presence of isoproterenol was significantly suppressed by S107. Our model provides a promising platform to study disease mechanisms and screen drugs.
Induced pluripotent stem cells (iPSCs) can serve as a source of cardiomyocytes (CMs) to treat end-stage heart failure; however, transplantation of genetically dissimilar iPSCs even within species ...(allogeneic) can induce immune rejection. We hypothesized that this might be limited by matching the major histocompatibility complex (MHC) antigens between the donor and the recipient. We therefore transplanted fluorescence-labeled (GFP) iPSC-CMs donated from a macaque with homozygous MHC haplotypes into the subcutaneous tissue and hearts of macaques having heterozygous MHC haplotypes (MHC-matched; group I) or without identical MHC alleles (group II) in conjunction with immune suppression. Group I displayed a higher GFP intensity and less immune-cell infiltration in the graft than group II. However, MHC-matched transplantation with single or no immune-suppressive drugs still induced a substantial host immune response to the graft. Thus, the immunogenicity of allogeneic iPSC-CMs was reduced by MHC-matched transplantation although a requirement for appropriate immune suppression was retained for successful engraftment.
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•Cardiomyocytes from iPSCs can treat heart disease•iPSC-CMs were transplanted into MHC-matched or unmatched cynomolgus macacques•Matched iPSC-CM grafts had better survival and less host rejection immune response•Immunosuppression was still required for successful allogeneic iPSC-CM engraftment
In this article, Sawa and colleagues examined whether transplantation of cardiomyocytes generated from induced pluripotent stem cells could alleviate immune-mediated rejection in major histocompatibility antigen-matched non-human primates. Transplantation of matched tissue prevented allogeneic immune rejection and enhanced engraftment with appropriate immunosuppressants. Thus, banked iPSCs with simple MHC profiles might be useful for regenerative therapy for a variety of pathologies.
Hand1 and Hand2 are transcriptional factors, and knockout mice of these genes show left and right ventricular hypoplasia, respectively. However, their function and expression in human cardiogenesis ...are not well studied. To delineate their expressions and assess their functions in human cardiomyocytes (CMs) in vitro, we established two triple-reporter human induced pluripotent stem cell lines that express HAND1mCherry, HAND2EGFP and either MYH6-driven iRFP670 or tagBFP constitutively and investigated their expression dynamics during cardiac differentiation. On day 5 of the differentiation, HAND1 expression marked cardiac progenitor cells. We profiled the CM subpopulations on day 20 with RNA sequencing and found that mCherry+ CMs showed higher proliferative ability than mCherry− CMs and identified a gene network of LEF1, HAND1, and HAND2 to regulate proliferation in CMs. Finally, we identified CD105 as a surface marker of highly proliferative CMs.
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•Expression of HAND1 marks cardiovascular progenitor cells•LEF1 is a key regulator of proliferating cardiomyocytes•CD105 expression marks highly proliferative cardiomyocytes
HAND1 and HAND2 are important cardiac transcriptional factors, but their functions in human cardiogenesis are difficult to analyze. Okubo et al. established HAND1mCherry and HAND2EGFP reporter induced pluripotent stem cells and showed that HAND1 marks cardiovascular progenitors and regulates the gene network of cardiomyocyte proliferation. They further showed that CD105 can be used as a surface marker for proliferative cardiomyocytes.
Compared with glycated hemoglobin (HbA1c), glycated albumin (GA) is superior in estimating glycemic control in diabetic patients on hemodialysis (HD). However, the better index for assessment of ...glycemic control in diabetic patients on peritoneal dialysis (PD) and the impact of protein loss on GA are unknown. Twenty diabetic patients on HD were matched by age, sex, and baseline postprandial plasma glucose (PG) levels to 20 PD patients. PG, HbA1c, GA, and serum albumin levels were measured for six months. Protein loss in PD patients was estimated by measuring the protein concentration in the peritoneal dialysate and by 24 h urine collection. Although PG and HbA1c did not differ significantly between the groups, the PD group had significantly lower GA (17.8% versus 20.8%, p < 0.001) and GA/HbA1c ratio (2.95% versus 3.45%, p < 0.0001) than the HD group. Although the PG level correlated significantly with the GA levels in both groups, it was not correlated with the HbA1c levels in both groups. HbA1c level was negatively associated with erythropoiesis-stimulating agent (ESA) dose in both groups, whereas GA was not significantly associated with serum albumin, hemoglobin concentration, ESA dose, and protein loss. Multiple regression analysis identified GA as the only independent factor associated with PG in PD patients. Our results suggested that GA was not significantly associated with protein loss, hemoglobin, serum albumin, and ESA dose. Although GA might underestimate glycemic status, it provided a significantly better measure for estimating glycemic control than HbA1c, even in PD patients.
Due to the COVID-19 pandemic, the 84thAnnual Meeting of the Japanese Circulation Society (JCS) was held in a web-based format for the first time in its history as “The Week for JCS 2020” from Monday, ...July 27 to Sunday, August 2, 2020. All sessions, including general abstracts, were streamed live or on-demand. The main theme of the meeting was “Change Practice!” and the aim was to organize the latest findings in the field of cardiovascular medicine and discuss how to change practice. The total number of registered attendees was over 16,800, far exceeding our expectations, and many of the sessions were viewed by far more people than at conventional face-to-face scientific meetings. At this conference, the power of online information dissemination was fully demonstrated, and the evolution of online academic meetings will be a direction that cannot be reversed in the future. The meeting was completed with great success, and we express our heartfelt gratitude to all affiliates for their enormous amount of work, cooperation, and support.
Myotonic dystrophy type 1 (DM1) is an autosomal-dominant multi-system disease caused by expanded CTG repeats in dystrophia myotonica protein kinase (DMPK). The expanded CTG repeats are unstable and ...can increase the length of the gene with age, which worsens the symptoms. In order to establish a human stem cell system suitable for the investigation of repeat instability, DM1 patient-derived iPSCs were generated and differentiated into three cell types commonly affected in DM1, namely cardiomyocytes, neurons and myocytes. Then we precisely analysed the CTG repeat lengths in these cells. Our DM1-iPSCs showed a gradual lengthening of CTG repeats with unchanged repeat distribution in all cell lines depending on the passage numbers of undifferentiated cells. However, the average CTG repeat length did not change significantly after differentiation into different somatic cell types. We also evaluated the chromatin accessibility in DM1-iPSCs using ATAC-seq. The chromatin status in DM1 cardiomyocytes was closed at the DMPK locus as well as at SIX5 and its promoter region, whereas it was open in control, suggesting that the epigenetic modifications may be related to the CTG repeat expansion in DM1. These findings may help clarify the role of repeat instability in the CTG repeat expansion in DM1.
In order to resume operations after a large earthquake, it is necessary to investigate the degree of damage to railway structures. The inspection of bearings is labor-intensive, particularly when the ...bearings are located on the high piers or in narrow places. This study proposes a method for detecting seismic damage to bearings using a displacement sensor. The relationship between the degree of damage and running safety of train is investigated for a rubber bearing and a line bearing. In addition, we developed a displacement sensor that detects the seismic damage of bearings and enables remote monitoring by wireless communication.
Papillary fibroelastoma (PFE) is a benign tumor that arises mostly from left-sided valves. PFE can cause stroke, and surgical resection may be needed. Lambl's excrescence (LE) is a filiform valvular ...lesion and is considered a possible cause of stroke. A 79-year-old man with light-headedness and left-sided hemiparesis was diagnosed with stroke. Transesophageal echocardiography (TEE) revealed a round-shaped mobile mass in the left ventricular outflow tract (LVOT), which was considered the cause of the stroke. Surgical resection was performed transaortically, and during surgery, a mass was incidentally detected on the noncoronary cusp (NCC), which was also resected followed by aortic valve replacement. Pathology confirmed that the mass in the LVOT was a PFE and that the filiform mass on the NCC was LE. We herein report a rare case of PFE in the LVOT and coexisting LE on the NCC. A careful examination via TEE helps to identify other possible causes of stroke hidden behind the obvious cause.
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