Hiroshi Kasanuki

Transplantation of cardiac progenitor cells ameliorates cardiac dysfunction after myocardial infarction in mice

Cardiac progenitor cells are a potential source of cell therapy for heart failure. Although recent studies have shown that transplantation of cardiac stem/progenitor cells improves function of infarcted hearts, the precise mechanisms of the improvement in function remain poorly understood. The present study demonstrates that transplantation of sheets of clonally expanded stem cell antigen 1-positive (Sca-1-positive) cells (CPCs) ameliorates cardiac dysfunction after myocardial infarction in mice. CPC efficiently differentiated into cardiomyocytes and secreted various cytokines, including soluble VCAM-1 (sVCAM-1). Secreted sVCAM-1 induced migration of endothelial cells and CPCs and prevented cardiomyocyte death from oxidative stress through activation of Akt, ERK, and p38 MAPK. Treatment with antibodies specific for very late antigen-4 (VLA-4), a receptor of sVCAM-1, abolished the effects of CPC-derived conditioned medium on cardiomyocytes and CPCs in vitro and inhibited angiogenesis, CPC migration, and survival in vivo, which led to attenuation of improved cardiac function following transplantation of CPC sheets. These results suggest that CPC transplantation improves cardiac function after myocardial infarction through cardiomyocyte differentiation and paracrine mechanisms mediated via the sVCAM-1/VLA-4 signaling pathway.

Acute decompensated heart failure syndromes (ATTEND) registry. A prospective observational multicenter cohort study: Rationale, design, and preliminary data

Acute heart failure syndromes (AHFS) are likely to increase in the future, and the high readmission rate of patients with AHFS is an important issue in Western countries. However, there are very few published epidemiological studies on AHFS in the Asia Pacific region. Because AHFS are heterogeneous, the characteristics, clinical profile, and management of AHFS should be clarified in an epidemiological study. The acute decompensated heart failure syndromes (ATTEND) registry is a prospective, observational, multicenter cohort study being performed in Japan and is the first epidemiological study of AHFS in the Asia Pacific region. This study is designed to investigate several aspects of AHFS as follows: (1) the registry allows patient-based data collection for precise evaluation of patient characteristics and short-term outcomes, including the readmission rate; (2) confirmation of clinical assessments can be performed, and new clinical assessments can be created; and (3) feedback allows the modification of guidelines for clinical management. The present report describes the clinical characteristics of patients with AHFS in Japan based on the preliminary data collected in this study, and the similarities and differences in characteristics of these patients compared with those in Western countries. Although most of the patient characteristics did not differ from those reported in Western studies, there are some unique findings in this study, including a high rate of treatment with carperitide (69.4%) and angiotensin II receptor blockers (53.9%) at discharge and a longer hospital stay (median 21 days). The ATTEND registry is designed to provide valuable information to clarify the characteristics of patients with AHFS to improve their management.

Enhancement of the L-Type Ca2+ Current by Mechanical Stimulation in Single Rabbit Cardiac Myocytes

Anion conductance is known to be activated by mechanical stimulation, such as osmotic cell swelling or cell inflation via the patch pipette, of canine or rabbit cardiac myocytes. The effects of mechanical stimulation on time-dependent currents, however, remain unsettled. Using the whole-cell voltage-clamp method, we have found that mechanical stimuli enhance the L-type Ca2+ current (ICa,L) in rabbit cardiac myocytes. At every membrane potential, ICa,L was reversibly increased by osmotic cell swelling and by cell inflation caused by applying a positive pressure of 10 to 15 cm H2O via the patch pipette. ICa,L was increased during cell inflation by 37 +/- 21% (mean +/- SD, n = 17) in atrial cells and by 37 +/ -8% (n = 7) in sinoatrial node cells in solution containing 2 mmol/L Ca2+. The current-voltage relationship, the inactivation time constant, the steady state inactivation curve, and the conductance properties of ICa,L were all virtually unaffected by mechanical stimulation except for the open probability, which appears to increase. The increase in ICa,L was not dependent on protein kinase A, since an inhibitor peptide of cAMP-dependent protein kinase failed to prevent the increase in ICa,L during mechanical stimuli (n=5). The increase in ICa,L caused by cell inflation was unaffected by the chelation of intracellular Ca2+ by the addition of 10 mmol/L EGTA or 10 mmol/L BAPTA to the pipette solution, suggesting that the effect was not mediated by changes in intracellular Ca2+. Thus, mechanical stimulation due to cell swelling or inflation may itself directly increase ICa,L in rabbit cardiac myocytes.

Oxidized LDL receptor gene (OLR1) is associated with the risk of myocardial infarction

Lectin-like oxidized low-density lipoprotein receptor (LOX-1/OLR1) has been suggested to play a role in the progression of atherogenesis. We analyzed the OLR1 gene and found a single nucleotide polymorphism (SNP), G501C, in patients with ischemic heart disease from a single family, which resulted in the missense mutation of K167N in LOX-1 protein. We compared the group of patients with myocardial infarction (MI) (n=102) with a group of clinically healthy subjects (n=102), and found that the MI group had a significantly high frequency of 501G/C+501C/C (38.2%) compared with the healthy group (17.6%; p<0.002). The odds ratio for the risk of MI associated with the 501G/C+501C/C genotype was 2.89 (95% CI, 1.51-5.53). These findings suggest that OLR1 or a neighboring gene linked with G501C SNP is important for the incidence of MI. Manipulating LOX-1 activity might be a useful therapeutic and preventative approach for coronary artery disease, especially for individuals with the G501C genotype of OLR1.

Angiotensin II receptor blocker-based vs. non-angiotensin II receptor blocker-based therapy in patients with angiographically documented coronary artery disease and hypertension: the Heart Institute of Japan Candesartan Randomized Trial for Evaluation in Coronary Artery Disease (HIJ-CREATE)

AIMS To test whether angiotensin II receptor blockers (ARBs) therapy can reduce the incidence of cardiovascular events compared with non-ARB-based standard pharmacotherapy in coronary artery disease (CAD) patients with hypertension. METHODS AND RESULTS Angiographically documented CAD patients with hypertension were randomly assigned to receive either candesartan-based (n= 1024) or non-ARB-based pharmacotherapy including angiotensin-converting enzyme-inhibitors (n = 1025). The primary endpoint was the occurrence of a first major adverse cardiovascular event (MACE). There were 552 primary events during a median follow-up of 4.2 years: 264 (25.8%) in the candesartan group and 288 (28.1%) in the non-ARB group (hazard ratio, 0.89; 95% confidence interval, 0.76-1.06). No significant differences existed between groups in terms of cardiovascular death (2.7 vs. 2.4%, 1.14; 0.66-1.95), non-fatal myocardial infarction (2.8 vs. 2.5%, 1.12; 0.66-1.88), or heart failure (3.9 vs. 4.3%, 0.91; 0.59-1.40). New-onset diabetes was diagnosed significantly less frequently with candesartan than with non-ARBs (0.37; 0.16-0.89). Incidence of study drug discontinuation due to adverse events was lower with candesartan than with non-ARBs (5.7 vs. 12.2%, P < 0.001). CONCLUSION Although candesartan showed no significant differences in MACE compared with the non-ARB treatment group, the drug significantly reduced the incidence of new-onset diabetes and was better tolerated. This study is registered as International Standard Randomised Controlled Trial No. UMIN000000790.

Assessment of Markers for Identifying Patients at Risk for Life‐Threatening Arrhythmic Events in Brugada Syndrome

Introduction: Risk stratification for life‐threatening arrhythmic events in Brugada syndrome is not yet established. The aim of the present study was to examine the usefulness of various markers in predicting life‐threatening arrhythmic events in the Brugada syndrome.

Telmisartan induces proliferation of human endothelial progenitor cells via PPARγ-dependent PI3K/Akt pathway

OBJECTIVE Although recent clinical trials have suggested that angiotensin II type 1 receptor blockers (ARBs) reduced cardiovascular events, the precise mechanisms involved are still unknown. Telmisartan, an ARB, has recently been identified as a ligand of peroxisome proliferator-activated receptor-gamma (PPARgamma). On the other hand, since endothelial progenitor cells (EPCs) are thought to play a critical role in ischemic diseases, we investigated effects of telmisartan on proliferation of EPCs. METHODS AND RESULTS Human peripheral blood mononuclear cells were isolated from healthy volunteers, and cultured on fibronectin-coated dishes in the presence or absence of telmisartan. Four days after starting culture, adherent cells were collected, and equal numbers of cells were reseeded into methylcellulose medium with or without telmisartan. In the presence of telmisartan, numbers of colonies increased in a dose-dependent manner. DiI-AcLDL uptake and lectin and CD31, CD34 staining revealed that these colonies were EPCs. Increase in colony number by treatment with telmisartan was absolutely inhibited when cultured with a specific inhibitor of PPARgamma. In addition, we observed that specific inhibitors of phosphoinositide-3 kinase (PI3K) abolished telmisartan-stimulated increase of monocytic EPC-like cells and telmisartan induced phosphorylation of Akt. Furthermore, mRNA expression of p21 was downregulated in a dose dependent manner, suggesting that growth inductive effects of telmisartan might be regulated by the PI3K/Akt and p21 signaling pathway. CONCLUSIONS These findings suggest that telmisartan might contribute to endothelial integrity and vasculogenesis in ischemic regions by increasing numbers of EPCs.

Impact of Sleep-Disordered Breathing on Life-Threatening Ventricular Arrhythmia in Heart Failure Patients With Implantable Cardioverter-Defibrillator

It was recognized that sleep-disordered breathing (SDB) is associated with cardiac arrhythmia and sudden cardiac death. However, it was unclear whether the presence of SDB increased the risk of life-threatening ventricular arrhythmia in patients with heart failure (HF) with an implantable cardioverter-defibrillator (ICD). Seventy-one patients with HF and an ICD who were followed up for 180 days after a sleep study were prospectively studied. All patients had an ejection fraction <or=35%. SDB was defined as an apnea-hypopnea index >or=10 events/hour on the sleep study. The frequency of appropriate ICD therapy and the day-night pattern of ICD therapies were compared between patients with and without SDB. SDB was diagnosed in 47 of 71 patients (66%). There were no statistical differences between patients with and without SDB in baseline cardiac function. However, appropriate ICD therapies occurred more frequently in patients with (43%) than without SDB (17%; p = 0.029). On multivariate analysis, the presence of SDB was an independent predictor for appropriate ICD therapy (hazard ratio 4.05, 95% confidence interval 1.20 to 13.65, p = 0.015). Moreover, the rate of total ICD therapy from midnight to 6 A.M. was significantly higher in patients with (34%) than without SDB (13%; p = 0.046). In conclusion, in patients with HF with an ICD, the presence of SDB was common and an independent predictor of life-threatening ventricular arrhythmias that were more likely to occur during sleep.

Sudden Cardiac Death and Left Ventricular Ejection Fraction During Long-Term Follow-up After Acute Myocardial Infarction in the Primary Percutaneous Coronary Intervention Era. Results from the HIJAMI-II Registry

Objective: To determine the incidence of sudden cardiac death (SCD) according to left ventricular ejection fraction (LVEF) in survivors of myocardial infarction (MI) in the primary percutaneous coronary intervention (PCI) era. Design: A multicentre observational prospective registered cohort study. Setting: 18 medical centres in Japan. Patients: 4122 consecutive patients (mean age 66 (SD 12) years, 73.7% male) with acute MI, who were discharged alive. Main outcome measures: The primary end-point was SCD, and a secondary end-point was death from any cause. Results: Patients were categorised into three groups: LVEF >40% (n = 3416), LVEF ⩽40% and >30% (n = 507) and LVEF ⩽30% (n = 199). Among all patients, 77.8% received PCI and 3.7% received coronary artery bypass graft surgery. During an average follow-up of 4.1 years, SCD was 1.2% and mortality was 13.1%. Patients with LVEF ⩽30% and LVEF ⩽40% and >30% were at increased risk for SCD (HR 5.99, 95% CI 2.73 to 13.14, p<0.001, HR 3.37, 95% CI 1.74 to 6.50, p<0.001, respectively), and mortality (HR 3.85, 95% CI 2.96 to 5.00, p<0.001, HR 2.06, 95% CI 1.66 to 2.57, p<0.001, respectively), compared to patients with LVEF >40%. Kaplan-Meier estimates of SCD in patients with LVEF ⩽30% were 2.9%, 5.1% and 5.1% at 1, 3 and 5 years, respectively. Conclusion: There is a low incidence of SCD in survivors of MI in the primary PCI era, although LVEF is a predictor of increased risk for SCD.

Mutation of junctophilin type 2 associated with hypertrophic cardiomyopathy

AbstractJunctophilin subtypes, designated as JPH1∼4, are protein components of junctional complexes and play essential roles in cellular Ca2+ signaling in excitable cells. Knockout mice lacking the cardiac-type Jph2 die of embryonic cardiac arrest, and the mutant cardiac myocytes exhibit impaired formation of peripheral couplings and arrhythmic Ca2+ signaling caused by functional uncoupling between dihydropyridine and ryanodine receptor channels. Based on these observations, we hypothesized that mutations of JPH2 could cause human genetic cardiac diseases. Among 195 Japanese patients (148 index cases and 47 affected family members) with hypertrophic cardiomyopathy (HCM), two heterozygous nonsynonymous nucleotide transitions, G505S and R436C, were newly found in JPH2. When Fishers exact test was used to compare index cases with HCM to unrelated Japanese healthy controls in the frequencies of mutant alleles, only the G505S mutation showed statistical significance (4/296 HCM patients and 0/472 control individuals, P=0.022). This result was still significant after Bonferronis correction for multiple comparisons (P=0.044). To the best of our knowledge, this is the first report on JPH2 mutation associated with HCM.