Shin Kashimura

Impaired respiratory function in MELAS‐induced pluripotent stem cells with high heteroplasmy levels

Mitochondrial diseases are heterogeneous disorders, caused by mitochondrial dysfunction. Mitochondria are not regulated solely by nuclear genomic DNA but by mitochondrial DNA. It is difficult to develop effective therapies for mitochondrial disease because of the lack of mitochondrial disease models. Mitochondrial myopathy, encephalomyopathy, lactic acidosis, and stroke‐like episodes (MELAS) is one of the major mitochondrial diseases. The aim of this study was to generate MELAS‐specific induced pluripotent stem cells (iPSCs) and to demonstrate that MELAS‐iPSCs can be models for mitochondrial disease. We successfully established iPSCs from the primary MELAS‐fibroblasts carrying 77.7% of m.3243A>G heteroplasmy. MELAS‐iPSC lines ranged from 3.6% to 99.4% of m.3243A>G heteroplasmy levels. The enzymatic activities of mitochondrial respiratory complexes indicated that MELAS‐iPSC‐derived fibroblasts with high heteroplasmy levels showed a deficiency of complex I activity but MELAS‐iPSC‐derived fibroblasts with low heteroplasmy levels showed normal complex I activity. Our data indicate that MELAS‐iPSCs can be models for MELAS but we should carefully select MELAS‐iPSCs with appropriate heteroplasmy levels and respiratory functions for mitochondrial disease modeling.

G-CSF supports long-term muscle regeneration in mouse models of muscular dystrophy

Duchenne muscular dystrophy (DMD) is a chronic and life-threatening disease that is initially supported by muscle regeneration but eventually shows satellite cell exhaustion and muscular dysfunction. The life-long maintenance of skeletal muscle homoeostasis requires the satellite stem cell pool to be preserved. Asymmetric cell division plays a pivotal role in the maintenance of the satellite cell pool. Here we show that granulocyte colony-stimulating factor receptor (G-CSFR) is asymmetrically expressed in activated satellite cells. G-CSF positively affects the satellite cell population during multiple stages of differentiation in ex vivo cultured fibres. G-CSF could be important in developing an effective therapy for DMD based on its potential to modulate the supply of multiple stages of regenerated myocytes. This study shows that the G-CSF-G-CSFR axis is fundamentally important for long-term muscle regeneration, functional maintenance and lifespan extension in mouse models of DMD with varying severities.

H1foo Has a Pivotal Role in Qualifying Induced Pluripotent Stem Cells

Summary Embryonic stem cells (ESCs) are a hallmark of ideal pluripotent stem cells. Epigenetic reprogramming of induced pluripotent stem cells (iPSCs) has not been fully accomplished. iPSC generation is similar to somatic cell nuclear transfer (SCNT) in oocytes, and this procedure can be used to generate ESCs (SCNT-ESCs), which suggests the contribution of oocyte-specific constituents. Here, we show that the mammalian oocyte-specific linker histone H1foo has beneficial effects on iPSC generation. Induction of H1foo with Oct4, Sox2, and Klf4 significantly enhanced the efficiency of iPSC generation. H1foo promoted in vitro differentiation characteristics with low heterogeneity in iPSCs. H1foo enhanced the generation of germline-competent chimeric mice from iPSCs in a manner similar to that for ESCs. These findings indicate that H1foo contributes to the generation of higher-quality iPSCs.

Predictive factors of lead failure in patients implanted with cardiac devices

INTRODUCTION Lead failures (LFs) are one of the most common complications in patients implanted with cardiovascular implantable electronic devices. LFs often cause serious secondary complications such as inappropriate ICD shocks or asystole. This study aimed to identify the clinical factors associated with the occurrence of LFs. METHODS A total of 735 consecutive device implantations (mean age 67±15years, males 64%) performed at a single university hospital setting from 1997 to 2014 were included. The implanted devices consisted of 421 pacemakers, 250 implantable cardioverter defibrillators (ICD), 9 cardiac resynchronization therapy pacemakers (CRT-P), and 55 CRT defibrillators (CRT-D). The primary endpoint was the development of an LF. RESULTS During a mean duration of 5.8±4.3years, 38 LFs developed in 31 patients (mean age 56±14years). LFs included 32 ICD (7 Sprint Fidelis, 2 Riata), and 6 pacing leads. Nine patients received inappropriate ICD shocks and 1 had syncope due to an LF. All patients underwent lead reinsertions with device replacements. Eight patients required opposite site implantations due to venous occlusions. The predictive factors of LFs were the age, male sex, taller body length, ICD vs. pacemaker, lesser lead number, extra-thoracic puncture of the axillary vein vs. a cut-down of the cephalic vein, use of recalled leads and patients with idiopathic ventricular fibrillation (IVF) and Brugada syndrome (BrS). CONCLUSION LFs occurred mainly with ICD leads. A lesser age, the puncture method, lead model, and diagnosis of IVF/BrS were associated with the development of LFs.

Electrical superior vena cava isolation using photodynamic therapy in a canine model

AIMS With the new era of multi-tip radiofrequency or balloon ablation catheters replacing the point-to-point ablation strategy, we aimed to determine the feasibility of a ring-laser catheter ablation technology to electrically isolate the superior vena cava (SVC) by exploring the advantages of the limitless catheter tip size possibly with the photodynamic therapy (PDT)-mediated ablation. METHODS AND RESULTS We developed a first-generation prototype of a circular-laser-mapping catheter by fitting a 7 cm plastic optical fibre onto a circular variable-loop Lasso™ mapping catheter. Following SVC venography, both the laser catheter and another ring catheter for monitoring the SVC potentials were placed at the SVC. After the systemic infusion of a photosensitizer (talaporfin sodium), we initiated the irradiation with an output of 1 W in three canines and 0.3 W in four. The creation of electrical isolation as well as occurrence of phrenic nerve injury, sinus node injury, and SVC stenosis were evaluated before, immediately after, and 1 month after the procedure. A PDT-mediated SVC isolation was successfully performed in all seven canines. The isolation was completed with a laser irradiation of 70.4 ± 71.4 J/cm under 30.9 ± 5.0 µg/mL of a photosensitizer without any sinus node injury, phrenic nerve palsy, or SVC stenosis in both the acute and chronic evaluations. The minimum isolation time of 270 s was not correlated with the laser input power or the photosensitizer concentration. CONCLUSION The electrical SVC isolation was successfully and instantly achieved using the PDT laser-ring catheter without any complications.

Emerin plays a crucial role in nuclear invagination and in the nuclear calcium transient

Alteration of the nuclear Ca2+ transient is an early event in cardiac remodeling. Regulation of the nuclear Ca2+ transient is partly independent of the cytosolic Ca2+ transient in cardiomyocytes. One nuclear membrane protein, emerin, is encoded by EMD, and an EMD mutation causes Emery-Dreifuss muscular dystrophy (EDMD). It remains unclear whether emerin is involved in nuclear Ca2+ homeostasis. The aim of this study is to elucidate the role of emerin in rat cardiomyocytes by means of hypertrophic stimuli and in EDMD induced pluripotent stem (iPS) cell-derived cardiomyocytes in terms of nuclear structure and the Ca2+ transient. The cardiac hypertrophic stimuli increased the nuclear area, decreased nuclear invagination, and increased the half-decay time of the nuclear Ca2+ transient in cardiomyocytes. Emd knockdown cardiomyocytes showed similar properties after hypertrophic stimuli. The EDMD-iPS cell-derived cardiomyocytes showed increased nuclear area, decreased nuclear invagination, and increased half-decay time of the nuclear Ca2+ transient. An autopsied heart from a patient with EDMD also showed increased nuclear area and decreased nuclear invagination. These data suggest that Emerin plays a crucial role in nuclear structure and in the nuclear Ca2+ transient. Thus, emerin and the nuclear Ca2+ transient are possible therapeutic targets in heart failure and EDMD.

Prevalence and clinical characteristics of obstructive- and central-dominant sleep apnea in candidates of catheter ablation for atrial fibrillation in Japan

INTRODUCTION We aimed to study the prevalence and types of sleep apnea (SA) as well as their clinical characteristics in atrial fibrillation (AF) ablation candidates in Japan. METHODS Before catheter ablation, 197 consecutive AF patients (age: 60 ± 9 years, body mass index; 25.0 ± 3.0) were evaluated with portable polygraphy. We compared the clinical characteristics, according to the severity of SA as well as its types, as defined by the presence of obstruction and the mixed vs. central apnea indices. RESULTS The mean apnea-hypopnea index (AHI) was 17.7 ± 11.9, with 135 AF patients having an AHI ≥10 (68.5%). Patients with an AHI ≥10 had a significantly higher body mass index, plasma brain natriuretic peptide (BNP) level, prevalence of hypertension, and larger left atrial size. Among patients with an AHI ≥10, the incidence of obstructive-dominant SA was 60.9% and that of central-dominant SA was 7.6%. The prevalence of hypertension was significantly higher in obstructive-dominant SA patients (obstructive vs. central: 48.3% vs. 20.0%, P = 0.038). The obstructive apnea index correlated with plasma BNP level and age, but the central and mixed apnea indices did not. CONCLUSIONS The prevalence of SA was common in AF ablation candidates, even without an obesity epidemic, and the SA type was predominantly obstructive. Portable polygraphy was useful for detecting undiagnosed SA patients in AF ablation candidates.

A cost-utility analysis for catheter ablation of atrial fibrillation in combination with warfarin and dabigatran based on the CHADS2 score in Japan

BACKGROUND We aimed to clarify the cost-effectiveness of an expensive combination therapy for atrial fibrillation (AF) using both catheter ablation and dabigatran compared with warfarin at each CHADS2 score for patients in Japan. METHODS A Markov model was constructed to analyze costs and quality-adjusted life years associated with AF therapeutic options with a time horizon of 10 years. The target population was 60-year-old patients with paroxysmal AF. The indication for anticoagulation was determined according to the Japanese guideline. Anticoagulation-related data were derived from the RE-LY study and the AF recurrence rate was set at 2.7% per month during the first 12 months and at 0.40% per month afterwards. Stroke risk was determined according to AF recurrence, anticoagulation, and CHADS2 score. The risks for stroke recurrence and stroke death were also considered. Costs were calculated from the healthcare payers perspective, and only direct medical costs were included. RESULTS Warfarin was the most preferred option for patients with a CHADS2 score of 0 from a health economics aspect. Ablation under warfarin was preferred for a CHADS2 score of 1-3, while ablation under dabigatran was preferred for a CHADS2 score ≥4. The quality of life score for AF had the largest impact on the incremental cost-effectiveness ratios in the analysis between the anticoagulation arm and the anticoagulation+ablation arm for a CHADS2 score of 2. Within the range of the Japanese willingness-to-pay threshold (¥5,000,000), the ablation+warfarin arm became the best option with its probability of 81.7% for a CHADS2 score of 2; the dabigatran+ablation arm was the most preferred option with its probability of 56.1% for a CHADS2 score of 4. CONCLUSIONS Ablation under dabigatran therapy is an expensive therapeutic option, but it might benefit patients with a low quality of life and a high CHADS2 score.

Pulmonary Artery Denervation by Determining Targeted Ablation Sites for Treatment of Pulmonary Arterial Hypertension

At 19 years of age, a woman experiencing dyspnea on exertion was diagnosed with idiopathic pulmonary arterial hypertension. Pulmonary arterial hypertension–targeted drugs (oral beraprost, sildenafil, tadalafil, macitentan, and subcutaneous treprostinil) were administered sequentially. However, the patient’s symptoms, World Health Organization functional class II or III, persisted. The patient refused to start intravenous epoprostenol because of cosmetic concerns and was referred to our hospital at 38 years of age. Right-sided heart catheterization revealed mean pulmonary arterial pressure of 72 mm Hg and pulmonary vascular resistance of 13.0 Wood units. The patient developed right-sided heart failure twice within 1 year, which was poorly controlled by conventional therapy. Previous studies have reported that pulmonary artery denervation with radiofrequency catheter ablation of the pulmonary artery trunk significantly improves pulmonary hypertension.1,2 We undertook a clinical study to investigate a novel method of pulmonary artery denervation using a commercially available radiofrequency ablation catheter, in part because the circular ablation …

Diagnostic Accuracy of Commercially Available Automated External Defibrillators

Background Although automated external defibrillators (AEDs) have contributed to a better survival of out‐of‐hospital cardiac arrests, there have been reports of their malfunctioning. We investigated the diagnostic accuracy of commercially available AEDs using surface ECGs of ventricular fibrillation (VF), ventricular tachycardia (VT), and supraventricular tachycardia (SVT). Methods and Results ECGs(VF 31, VT 48, SVT 97) were stored during electrophysiological studies and transmitted to 4 AEDs, the LifePak CR Plus (CR Plus), HeartStart FR3 (FR3), and CardioLife AED‐2150 (CL2150) and ‐9231 (CL9231), through the pad electrode cables. For VF, the CL2150 and CL9231 advised shocks in all cases, and the CR Plus and FR3 advised shocks in all but one VF case. For VTs faster than 180 bpm, the ratios for advising shocks were 79%, 36%, 89%, and 96% for the CR Plus, FR3, CL2150, and CL9231, respectively. The FR3 and CR Plus did not advise shocks for narrow QRS SVTs, whereas the CL9231 tended to treat high‐rate tachycardias faster than 180 bpm even with narrow QRS complexes. The characteristics of the shock advice for the FR3 differed from that for the CL9231 (kappa coefficient [κ]=0.479, P<0.001), and the CR Plus and CL2150 had characteristics somewhere between the 2 former AEDs (κ=0.818, P<0.001). Conclusions Commercially available AEDs diagnosed VF almost always correctly. For VT and SVT diagnoses, a discrepancy was evident among the 4 investigated AEDs. The differences in the arrhythmia diagnosis algorithms for differentiating SVT from VT were thought to account for these differences.