Improve Heart Function Research Articles

Echinacoside inhibited cardiomyocyte pyroptosis and improved heart function of HF rats induced by isoproterenol via suppressing NADPH/ROS/ER stress.

Prevalence of heart failure (HF) continues to rise over time and is a global difficult problem; new drug targets are urgently needed. In recent years, pyroptosis is confirmed to promote cardiac remodelling and HF. Echinacoside (ECH) is a natural phenylethanoid glycoside and is the major active component of traditional Chinese medicine Cistanches Herba, which is reported to possess powerful anti-oxidation and anti-inflammatory effects. In addition, we previously reported that ECH reversed cardiac remodelling and improved heart function, but the effect of ECH on pyroptosis has not been studied. So, we investigated the effects of ECH on cardiomyocyte pyroptosis and the underlying mechanisms. In vivo, we established HF rat models induced by isoproterenol (ISO) and pre-treated with ECH. Indexes of heart function, pyroptotic marker proteins, ROS levels, and the expressions of NOX2, NOX4 and ER stress were measured. In vitro, primary cardiomyocytes of neonatal rats were treated with ISO and ECH; ASC speckles and caspase-1 mediated pyroptosis in cardiomyocytes were detected. Hoechst/PI staining was also used to evaluate pyroptosis. ROS levels, pyroptotic marker proteins, NOX2, NOX4 and ER stress levels were all tested. In vivo, we found that ECH effectively inhibited pyroptosis, down-regulated NOX2 and NOX4, decreased ROS levels, suppressed ER stress and improved heart function. In vitro, ECH reduced cardiomyocyte pyroptosis and suppressed NADPH/ROS/ER stress. We concluded that ECH inhibited cardiomyocyte pyroptosis and improved heart function via suppressing NADPH/ROS/ER stress.

FYCO1 ameliorates adverse cardiac remodeling in response to myocardial ischemia by enhancing autophagic flux

Abstract Background Imbalances in autophagy are known to have either protective or detrimental effects on cardiac function. Although there are significant insights into the early steps of the autophagy pathway, the mechanisms of autophagosome-lysosome transport and fusion in cardiomyocytes are less understood. Fyco1 is highly expressed in the heart and facilitates transport of autophagosomes in cardiomyocytes, enhancing global autophagic flux. Purpose The aim of our study was to investigate the effects of FYCO1 overexpression post myocardial infarction. Our hypothesis is that FYCO1 overexpression leads to enhanced autophagic flux and hence blunted cardiac remodeling and improved heart function. Methods FYCO1-Tg mice were crossbred with RFP-EGFP-LC3-Tg reporter mice (FYCO1-TGxRGF) to enable the analysis of autophagic flux using confocal microscopy. Myocardial ischemia was induced by permanent ligation of left anterior descending artery (LAD). Mice were analyzed 3 days and 30 days post LAD ligation. Cardiac function (ejection fraction, EF) and left ventricular (LV) mass were measured by echocardiography. Myocardial fibrosis, Midline Infarct size (%) and LV circumference were assessed in Masson's Trichrome stainings. Autophagy activaty was analyzed by Western blot for LC3 II and LC3 II/LC3 I. Furthermore, Evans blue/TTC staining was performed to assess the area at risk and to define perfused, ischemic and necrotic area post LAD. Results In FYCO1-TGxRGFP mice 3 days post LAD we observed an overall increased autophagic flux demonstrated by significantly increased LC3 II protein levels (WT sham: 1±0,3; WT LAD: 1,3±0,2; TG sham: 10,8±1,2; TG LAD: 8,8±0,9) and LC3 II/LC3 I ratios (WT sham: 1±0,3; WT LAD: 0,99±0,1; TG sham: 10,5±1,2; TG LAD: 5,6±1) post LAD. Moreover, using confocal microscopy revealed a shift in autophagosomal transport towards plus-end-directed transport, shown by peripheral accumulation of autophagosomes (WT: 1,4±0,8; TG: 46,6±5,8) and increased levels of autolysosomes (WT: 79,2±19,2; TG: 181,1±36,7). In Evans blue/TTC staining, FYCO1-TGxRGFP mice demonstrated comparable ischemic but markedly decreased necrotic area (ischemic: 1,9±1,8%; necrotic: 37,1±11,5%) within the LV as compared to WT (ischemic: 2,1±1,9%; necrotic: 53,4±31,4%). Fibrosis in LV (WT: 19,6±1,8%; TG: 10,6±1,6%) and infarct size (WT: 34,5±3,9%; TG: 5,5±2%) were found significantly decreased in FYCO1-TGxRGFP-mice. FYCO1-TGxRGFP mice presented with increased LV mass (WT: 106,2±25,5 mg; TG: 114,2±38,3mg) but comparable LV circumference/tibia length (WT: 11,1±0,9; TG: 11,4±1,5). Importantly, global heart function of FYCO1-TGxRGFP-mice was significantly improved post LAD compared to WT (EF WT: 36,7±6,3%; TG: 46,3±18,3%). Conclusion Our study demonstrates that the activation of autophagy via FYCO1 overexpression protects against adverse cardiac remodeling and improves cardiac function post myocardial ischemia. These findings may thus offer translational potential in the treatment of myocardial infarction. Funding Acknowledgement Type of funding sources: None.

Differences in mitochondrial efficiency and heart function after different modes of exercise training in hypertension

Abstract Physical exercise is often used for the cardioprotective purpose in hypertension. However, it's not clear whether the mitochondrial efficacy will depend on the intensity and mode of physical exercise. The aim of the work is to investigate the effect of different modes of exercise training on mitochondria function and cardyohemodynamic in hypertension. All experimental procedures were performed in accordance with the European Communities Council Directive of 24 November 1986 (86/609 /EEC). Six-month-old spontaneously hypertensive rats (SHR) and normotensive control–Wistar rats were randomly assigned to 2 different training modes: moderate (20 min) and enhanced (45 min). Swimming training was done five times per week for 5–6 weeks. The functional cardiohemodynamic indicators were registered via microcatheter and Millar Pressure-Volume System. Mitochondrial oxygen consumption registered by Oxygraph. Moderate exercise training mode in SHR had a positive effect on the respiratory chain of mitochondria, respiratory control increased by 25,3%, the mitochondrial membrane potential increased by 47,8%. Moderate exercise training mode protected mitochondrial permeability transition pore (MPTP) formation. The threshold of MPTP opening increased by 1.4 times and the sensitivity of MPTP to inductor Ca2+ decreased. It was shown that end-systolic and end-diastolic pressure of SHR was decreased by 23,8% and 32,7% respectively. Moderate exercise improves end-diastolic heart function in SHR by increasing dP/dtmin and reducing the end-diastolic myocardial stiffness in 8,3 times. Stroke volume increased in 3,3 times, stroke work decreased by 17.2%, which may indicate the heart work efficiency increased after moderate exercise training. The Frank-Starling mechanism efficiency after moderate exercise was increased by 3,7 times. After enhanced exercise mode we didn't observe a protected effect on heart mitochondria and heart function in SHR. The mitochondrial membrane potential didn't increase, mitochondrial respiration in states V2, V3, V4 were significantly decreased. In conclusion, we showed that a moderate mode of exercise in SHR rats increased mitochondrial efficiency and improved heart function. The enhanced mode of exercise was excessive for SHR which was confirmed by suppressing the mitochondrial respiration and end-diastolic function of the heart. Funding Acknowledgement Type of funding sources: None.

Activation of mitochondrial telomerase reverses relative lymphopenia post myocardial infarction: results from the randomised, double-blinded TACTIC phase IIa pilot trial

Abstract Background Immune ageing is a phenomenon which includes lymphopenia, expansion of pro-inflammatory T-lymphocyte subsets and telomere shortening. While lymphopenia predicts mortality after myocardial infarction (MI), MI itself leads to both an increase in terminally differentiated memory CD8+ T-lymphocytes (CD8+ TEMRAs) and a decrease in telomere length. Activation of telomerase has been shown to ameliorate lymphopenia, and improve heart function after MI in mouse models. TA-65 is an oral telomerase activator, which may ameliorate immune ageing and improve outcome after MI. Methods This double-blinded, randomized placebo-controlled pilot study evaluated the use of TA-65 in 90 MI patients over 65 years, the average onset age for immune ageing. Patients were randomised to either TA-65 (16 mg daily, n=45) or placebo (n=45) for 12 months. The majority of patients underwent percutaneous coronary intervention (87%) or coronary artery bypass surgery (2%) as treatment for their index MI. The pre-defined primary endpoint was the proportion of CD8+ TEMRA T-lymphocytes at 12 months, a marker of immune ageing. A linear mixed effects model was used for the analysis. Results The proportion of CD8+ TEMRAs after 12 months did not differ between the 2 treatment groups, although only increased significantly in the placebo group (+2.2%, 95% CI: 0.14–4.24). TA-65 was well tolerated, with total adverse events lower in the treatment group (TA-65 vs. placebo group: n=130 vs. n=185). We observed at 12 months a 62% reduction in mean high-sensitivity CRP (hsCRP: TA-65 vs. placebo group: 1.1±0.9 vs. 2.9±6.4 mg/L) and a 15%-increase in mean peripheral blood lymphocytes in TA-65 after 12 months. In the whole sample, among those who were treated with TA-65 compared to Placebo, after 12 months peripheral blood lymphocytes increased (+285 cells /μl, 95% CI: 117–452). The latter was due to significant increases in the TA-65 group from baseline to 12 months across all major lymphocyte populations: CD3+ (+15%), CD4+ (+14%),CD8+ T-lymphocytes (+19%), B-lymphocytes (+17%) and natural killer cells (+12%), while no changes occurred in major lymphocyte populations in the placebo group over the course of the study. Conclusion In this randomised clinical trial, we found that while CD8+ TEMRAs were not significantly altered after 12 months, the telomerase activator TA-65 significantly increased all major lymphocyte subsets and substantially reduced hsCRP at 12 months in patients with MI. These findings suggest TA-65 holds great promise in potentially reducing inflammation while improving an age-related decline in major lymphocyte populations, thereby enhancing immunity. A larger, multicentre, powered phase IIb efficacy trial to examine the potential effect of TA-65 in prognosis and heart function after MI is therefore warranted. Funding Acknowledgement Type of funding sources: Private company. Main funding source(s): TA-Science, New York, USA

Dapagliflozin but not empagliflozin prevents atrial fibrillation in an experimental whole-heart model

Abstract Background The SGLT2 inhibitors dapagliflozin and empagliflozin have an evolving role in heart failure therapy. Observational data suggest a lower risk of atrial fibrillation (AF) for patients on SGLT2 inhibitors. So far, it is unclear whether this is related to a direct antiarrhythmic potential of SGLT2 inhibitors or just a marker of improved heart function. Experimental data on the impact of SGTL2 inhibitors on atrial electrophysiology is scarce. Purpose This study aimed at evaluating the effects of the two SGLT2 inhibitors dapagliflozin and empagliflozin on atrial electrophysiology. Methods 25 rabbit hearts were explanted and retrogradely perfused employing the Langendorff-setup. Two catheters were placed on both atria to record monophasic action potentials. Hearts were paced at three different cycle lengths (350ms, 250ms, 150ms), thereby obtaining cycle-length dependent atrial action potential durations (aAPD90) and effective refractory periods (aERP). Atrial post-repolarization (aPRR) refractoriness was determined by the difference between aERP and aAPD90. AF was induced in the presence of acetylcholine (ACh, 1μM) and isoproterenol (Iso, 1μM). Thereafter, hearts were treated with dapagliflozin (n=13, 3 μM) or empagliflozin (n=12, 3 μM). Results Ach/Iso abbreviated aAPD90, aERP and prolonged aPRR in both groups (dapagliflozin group: aAPD90: −49 ms, p<0.01; aERP: −33 ms, p<0.01; aPRR: +18 ms, p=0.06; empagliflozin group: aAPD90: −40 ms, p<0.01; aERP: −25 ms, p<0.05; aPRR: +18 ms, p=0.05). Further treatment with dapagliflozin increased aAPD90 (+13 ms, p<0.01), aERP (+34 ms, p<0.05) and aPRR (+6 ms, p=ns). Additional administration of empagliflozin had no significant effect on aAPD90 (−8 ms, p=ns), aERP (−1 ms, p=ns) or aPRR (+9 ms, p=ns). Vulnerability to AF was assessed by a standardized protocol consisting of several trains of burst pacing. Ach/Iso increased the vulnerability to AF episodes in both groups (dapagliflozin group: 71 episodes vs. 1 under baseline conditions, p<0.01; empagliflozin group: 27 episodes vs. 2 under baseline conditions, p=0.08). Additional perfusion of dapagliflozin significantly reduced the occurrence of AF (to 30 episodes, p<0.05) while additional empagliflozin treatment had no significant antiarrhythmic effect (32 episodes, p=ns). Conclusion Dapagliflozin and empagliflozin had opposing effects on atrial electrophysiology. Dapagliflozin prolonged aAPD90 and aERP, thereby preventing AF. In contrast, empagliflozin did not change aAPD90 or aERP, resulting in no antiarrhythmic effect. Our findings hint at a potential antiarrhythmic benefit of dapagliflozin. Funding Acknowledgement Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Hans and Gertie Fischer-Foundation (to C.E.)

Diagnostic ultrasound-mediated microbubble cavitation dose-dependently improves diabetic cardiomyopathy through angiogenesis.

Ultrasound-mediated microbubble cavitation (UMMC) induces therapeutic angiogenesis to treat ischemic diseases. This study aimed to investigate whether diagnostic UMMC alleviates diabetic cardiomyopathy (DCM) and, if so, through which mechanisms. DCM model was established by injecting streptozocin into rats to induce hyperglycemia, followed by a high-fat diet. The combined therapy of cation microbubble with low-intensity diagnostic ultrasound (frequency = 4 MHz), with a pulse frequency of 20 Hz and pulse length (PL) of 8, 18, 26, or 36 cycles, was given to rats twice a week for 8 consecutive weeks. Diagnostic UMMC therapy with PL at 8, 18, and 26 cycles, but not 36 cycles, dramatically prevented myocardial fibrosis, improved heart functions, and increased angiogenesis, accompanied by increased levels of PI3K, Akt, and eNOS proteins in the DCM model of rats. In cultured endothelial cells, low-intensity UMMC treatment (PL = 3 cycles, sound pressure level = 50%, mechanical index = 0.82) increased cell viability and activated PI3K-Akt-eNOS signaling. The combination of diagnostic ultrasound with microbubble destruction dose-dependently promoted angiogenesis, thus improving heart function through PI3K-Akt-eNOS signaling in diabetes. Accordingly, diagnostic UMMC therapy should be considered to protect the heart in patients with diabetes.

Gene Therapy Hits Its Stride in the Clinic

Gene Therapy Hits Its Stride in the Clinic

Different Doses of Empagliflozin in Patients with Heart Failure with Reduced Ejection Fraction.

It was unclear whether there are discrepancies among the efficacy and safety of different doses of empagliflozin in patients with heart failure with reduced ejection fraction (HFrEF). The aim of this study was to compare the efficacy and safety of 25 mg and 10 mg of empagliflozin in HFrEF patients.In this 3-month, single-center, open-label, randomized, positive-controlled, parallel-group study, 100 patients with HFrEF were divided into two groups, namely, groups A (n = 50) and B (n = 50), which were given 25 mg/day and 10 mg/day of empagliflozin, respectively. Cardiac function indexes at baseline and at the end of the third month were compared between the two groups, as well as adverse events during the 3-month follow-up period. The primary outcome of this study was the change in the left ventricular ejection fraction (LVEF), and the secondary outcomes were the change in the left ventricular end-diastolic diameter (LVEDD) and the incidences of hypotension, acute kidney injury (AKI), and genitourinary infections.At the end of the third month, the changes in the LVEF and LVEDD were greater in group A than those in group B (P < 0.05). During the 3-month follow-up period, the differences in the incidences of hypotension, AKI, and genitourinary infections between the two groups were statistically insignificant (P > 0.05).The results from this study suggested that 25 mg of empagliflozin might be better than 10 mg in improving heart function in HFrEF patients, and the safety profiles of 25 mg and 10 mg of empagliflozin are comparable. Further studies are expected to substantiate our speculations.

Stem cell laden nano and micro collagen/PLGA bimodal fibrous patches for myocardial regeneration

BackgroundAlthough the use of cardiac patches is still controversial, cardiac patch has the significance in the field of the tissue engineered cardiac regeneration because it overcomes several shortcomings of intra-myocardial injection by providing a template for cells to form a cohesive sheet. So far, fibrous scaffolds fabricated using electrospinning technique have been increasingly explored for preparation of cardiac patches. One of the problems with the use of electrospinning is that nanofibrous structures hardly allow the infiltration of cells for development of 3D tissue construct. In this respect, we have prepared novel bi-modal electrospun scaffolds as a feasible strategy to address the challenges in cardiac tissue engineering .MethodsNano/micro bimodal composite fibrous patch composed of collagen and poly (D, L-lactic-co-glycolic acid) (Col/PLGA) was fabricated using an independent nozzle control multi-electrospinning apparatus, and its feasibility as the stem cell laden cardiac patch was systemically investigated.ResultsNano/micro bimodal distributions of Col/PLGA patches without beaded fibers were obtained in the range of the 4-6% collagen concentration. The poor mechanical properties of collagen and the hydrophobic property of PLGA were improved by co-electrospinning. In vitro experiments using bone marrow-derived mesenchymal stem cells (BMSCs) revealed that Col/PLGA showed improved cyto-compatibility and proliferation capacity compared to PLGA, and their extent increased with increase in collagen content. The results of tracing nanoparticle-labeled as well as GFP transfected BMSCs strongly support that Col/PLGA possesses the long-term stem cells retention capability, thereby allowing stem cells to directly function as myocardial and vascular endothelial cells or to secrete the recovery factors, which in turn leads to improved heart function proved by histological and echocardiographic findings.ConclusionCol/PLGA bimodal cardiac patch could significantly attenuate cardiac remodeling and fully recover the cardiac function, as a consequence of their potent long term stem cell engraftment capability.

Changes in Some Observational Cardiac Parameters and Cardiac PGC1-α Expression Following Eight Weeks of Endurance Training and Saffron Consumption in Animal Models of Alzheimer’s Disease

Introduction: The link between Alzheimer’s disease (AD) and heart disease has recently been reported. Previous studies have reported the beneficial role of endurance training (ET) and saffron (Sa) on the heart and nervous system health, but their interactive effect is not yet well known. Therefore, the aim of this study was to determine changes in some observational cardiac parameters and cardiac PGC1-α expression after 8 weeks of ET and Sa consumption in animal models of AD. Methods: In this experimental trial, 40 rats with AD (by intraperitoneal injection of 8 mg/kg neurotoxin trimethyltin) were divided into (1) AD, (2) sham (Sh), (3) Sa, (4) ET, and (5) ET+Sa groups. Additionally, to evaluate the effect of AD induction on the research variables, 8 healthy rats were included in the healthy control (HC) group. Groups 4 and 5 ran for 8 weeks, three 15-30 minute sessions per week at a speed of 20-15 m/min. Groups 3 and 5 received 25 mg/ kg aqueous extract of Sa peritoneally each day. To analyze the data, dependent samples t test, one-way analysis of variance and Tukey’s post hoc test, analysis of covariance with Bonferroni’s post hoc test in SPSS version 22.0 were used (P≥0.05). Results: In the Sa and ET+Sa groups, heart weight, heart weight to body weight ratio, and cardiac PGC1-α expression were higher and the body weight of these groups was significantly lower compared with the AD group (P≤0.05). Moreover, in the ET group, heart weight was higher than body weight and total body weight was lower compared to the AD group (P≤0.05). Conclusion: It seems that Sa and ET+Sa interaction improve heart function and some parameters related to heart health by increasing PGC1-α expression, but the effect of training depends on its type and intensity, which should be further studied.

Bone marrow-derived naïve B lymphocytes improve heart function after myocardial infarction: a novel cardioprotective mechanism for empagliflozin.

The role of adaptive immunity in myocardial recovery post myocardial infarction (MI), particularly the immune response by B lymphocytes, remains elusive. Bone marrow immune microenvironment in response to MI is remotely regulated by the hypothalamic pituitary adrenal (HPA) axis. We utilized the cardioprotective actions of SGLT2 inhibitor to identify and characterize bone marrow B cell subsets that respond to myocardial injury. Initially, we preformed ligation of left anterior descendant (LAD) coronary artery in male C57BL/6J mice to monitor the dynamic changes of immune cells across tissues. Mechanistic insights from mouse models demonstrated arrest of bone marrow B cell maturation and function 24h post MI. A secondary MI model (twice MIs) in mice was established for the first time to evaluate the dosage-dependent cardioprotection of empagliflozin (EMPA). Single-cell RNA-Seq further demonstrated that EMPA restored bone marrow naïve B cell (B220+CD19+CD43-IgM+IgD+) counts and function. Additionally, we recruited 14 acute MI patients with single LAD disease, and profiled B cells post percutaneous coronary intervention (PCI) (compared to 18 matched no-MI controls). We revealed a positive correlation of increased B cell counts with enhanced ejection fraction in MI patients with PCI while lymphopenia was associated with patients with heart failure. Mechanistically, MI triggers the release of glucocorticoids from neuroendocrine system, inducing NHE1-mediated autophagic death of bone marrow B cells while repressing B cell progenitor proliferation and differentiation. Infusion of B cells derived from bone marrow significantly improved cardiac function and diminished infarct size post MI. These findings provide new mechanistic insights into regulation of adaptive immune response post MI, and support targeting bone marrow B cell development for improved ventricular remodeling and reduced heart failure after MI.

Naringenin promotes angiogenesis of ischemic myocardium after myocardial infarction through miR-223-3p/IGF1R axis

IntroductionNaringenin exerts a protective effect on myocardial ischemia and reperfusion. It has been reported that miR-223-3p is a potential target for the treatment of myocardial infarction (MI). In view of the unreported correlation between Naringenin and miR-223-3p, this study was designed to confirm that the ameliorative effects of Naringenin on MI is directly related to the regulation of miR-223-3p.MethodsThrough electrocardiogram detection, Masson pathological staining and immunohistochemistry of angiogenesis-related factors, alleviative effects of Naringenin on heart function, myocardial injury and angiogenesis in MI mice were observed individually. Hypoxic HUVECs were selected in the in vitro experimental model. The cell viability, angiogenesis and migration ability were analyzed to fathom out the pro-angiogenesis potential of Naringenin. The effect of Naringenin on miR-223-3p, as well as the downstream molecular mechanism was verified through bioinformatics analysis and rescue experiments.ResultsNaringenin improved heart functions of MI mice, reduced degree of myocardial fibrosis, stimulated expressions of angiogenic factors and down-regulated level of miR-223-3p in myocardial tissue. In in vitro experiments, Naringenin increased the viability of hypoxic HUVECs, as well as the abilities of tube formation and migration, and further inhibited the expression of miR-223-3p. In the rescue trial, miR-223-3p mimic reversed the therapeutic effect of Naringenin. Type 1 insulin-like growth factor receptor (IGF1R), as a downstream target gene of miR-223-3p, partially offset the cellular regulatory effects of miR-223-3p after overexpression of IGF1R.ConclusionsNaringenin improves the angiogenesis of hypoxic HUVECs by regulating the miR-223-3p/IGF1R axis, and has the potential to promote myocardial angiogenesis in MI mice.

Dietary administration of L-carnitine during the fattening period of early feed restricted lambs modifies liver transcriptomic and plasma metabolomic profiles

Early feed restriction of lambs promotes a permanent mitochondrial dysfunction that impairs feed efficiency along the whole life. Dietary L-carnitine, a compound that plays an essential role in energy metabolism transferring long-chain fatty acids to mitochondria for subsequent β-oxidation, has demonstrated positive effects (e.g., improved markers or muscle/heart function) in early feed restricted lambs. The purpose of the present study is to ascertain the underlying mechanisms under these effects using samples of the same lambs in a liver transcriptomic and metabolomic approach. Twenty-two male Merino lambs were separated from the dams for 9 h daily to allow feed restriction during the suckling period. Once weaned, the lambs were allocated to a control group (CTRL, n = 11) being fed ad libitum a complete pelleted diet during the fattening phase, whereas the second group (CARN, n = 11) received the same diet formulated with 3 g/kg of L-carnitine. The most relevant results of this study revealed that the administration of 3 g of L-carnitine/ kg diet during the fattening period of early feed restricted lambs caused no differential expression of genes involved directly in β-oxidation. However the increased expression of genes related to the excretion of cholesterol as bile acids was in agreement with the higher amounts of glycodeoxycholic acid and other intermediates of cholesterol metabolism in the CARN group, and might have contributed to achieve an improved heart function. Moreover, the increased expression of ribosomes and translation pathways in the liver also allowed explaining the positive effects observed in the CARN group. It can be concluded that the improved markers or muscle/heart function achieved by the administration of 3 g of L-carnitine/kg diet to early feed restricted lambs are caused, mainly, by the increased expression of genes related either to ribosomes or cholesterol excretion.

Oct4 cooperates with c-Myc to improve mesenchymal-to-endothelial transition and myocardial repair of cardiac-resident mesenchymal stem cells

BackgroundCardiac-resident mesenchymal stem cells (cMSCs) can exhibit fibrotic, proinflammatory, and proangiogenic phenotype in response to myocardial ischemia (Isch). How their phenotypic fate decisions are determined remains poorly understood. Here, we demonstrate that the cooperation of Oct4 and c-Myc in cMSCs creates a preferable mesenchymal-to-endothelial transition (MEndoT) to promote angiogenesis and consequent myocardial repair.MethodsWe collected MSCs from cardiac and peripheral blood of rat with left ventricular Isch (LV Isch) 30 days after myocardial infarction (MI) or sham operation. After a comparison of characterization between cMSCs and peripheral blood MSCs (pbMSCs), we conducted transcriptome analysis and RNA sequencing of cMSCs. Using loss/gain-of-function approaches to understand the cooperation of c-Myc and Oct4 on MEndoT of cMSCs under hypoxic condition, we explored the mechanisms through transcriptome and functional experiment, and chromatin immunoprecipitation. Next, we transplanted male cMSCs with overexpression or inhibition of c-Myc/Oct4 into the infarcted myocardium of female rats and evaluated infarct size, cell retention, inflammation, remodeling, and function after 30 days.ResultsLV Isch switched cMSCs toward both inflammatory and proangiogenic phenotypes, with increased secretion of inflammatory cytokines as well as decreased expression of proangiogenic factors. The effect of LV Isch on pbMSCs was less remarkable. Gene expression heatmap showed imbalance in expression of Oct4 and c-Myc regulating genes associated with remodeling of cMSCs. We provided evidence that cMSCs-specific c-Myc- versus Oct4-overexpression showed divergent genomic signatures, and their corresponding target genes play an important role in regulating cMSCs phenotypic changes. In particular, Oct4 accelerated angiogenesis induced by c-Myc overexpression in cMSCs and inhibited their phenotypic transition into inflammatory cells and fibroblast. Mechanistically, exogenous Oct4 caused c-Myc to translocate from the nucleus to the cytoplasm and activated some of its target signalings including VEGF signaling. Although transplantation of cMSCs alone did not improve LV remodeling and function, cMSCs co-transfected with c-Myc and Oct4 promoted a more positive effect in their survival and reparative properties, increased animal survival, reduced infarct size, decreased scar thickness, inhibited LV remodeling, and improved heart function 30 days after MI. Significantly, Oct4 promoted MEndoT (“Rescue me” signal) of cMSCs after both c-Myc stimulation in vitro and transplantation into the infarcted heart.ConclusionsMyocardial Isch drives resident cMSCs toward multiple phenotypes. Oct4 interacts with c-Myc to promote MEndoT capacity of cMSCs and improve their survival and reparative effects through upregulation of angiogenesis-related signaling pathways. These findings may identify novel targets for stem cell therapy.

Oxidant stress-sensitive circRNA Mdc1 controls cardiomyocyte chromosome stability and cell cycle re-entry during heart regeneration

Targeting cardiomyocyte plasticity has emerged as a new strategy for promoting heart repair after myocardial infarction. However, the precise mechanistic network underlying heart regeneration is not completely understood. As noncoding RNAs, circular RNAs (circRNAs) play essential roles in regulating cardiac physiology and pathology. The present study aimed to investigate the potential roles of circMdc1 in cardiac repair after injury and elucidate its underlying mechanisms. Here, we identified that circMdc1 levels were upregulated in postnatal mouse hearts but downregulated in the regenerative myocardium. The expression of circMdc1 in cardiomyocytes is sensitive to oxidative stress, which was attenuated by N-acetyl-cysteine. Enforced circMdc1 expression inhibited cardiomyocyte proliferation, while circMdc1 silencing led to cardiomyocyte cell cycle re-entry. In vivo, the cardiac-specific adeno-associated virus-mediated knockdown of circMdc1 promoted cardiac regeneration and heart repair accompanied by improved heart function. Conversely, circMdc1 overexpression blunted the regenerative capacity of neonatal hearts after apex resection. Moreover, circMdc1 was able to block the translation of its host gene Mdc1 specifically by binding to PABP, affecting DNA damage and the chromosome stability of cardiomyocytes. Furthermore, overexpression of Mdc1 caused damaged mouse hearts to regenerate and repair after myocardial infarction in vivo. Oxidative stress-sensitive circMdc1 plays an important role in cardiac regeneration and heart repair after injury by regulating DNA damage and chromosome stability in cardiomyocytes by blocking the translation of the host gene Mdc1.

β-Catenin promotes long-term survival and angiogenesis of peripheral blood mesenchymal stem cells via the Oct4 signaling pathway

Stem cell therapy has been extensively studied to improve heart function following myocardial infarction; however, its therapeutic potency is limited by low rates of engraftment, survival, and differentiation. Here, we aimed to determine the roles of the β-catenin/Oct4 signaling axis in the regulation of long-term survival and angiogenesis of peripheral blood mesenchymal stem cells (PBMSCs). These cells were obtained from rat abdominal aortic blood. We showed that β-catenin promotes the self-renewal, antiapoptotic effects, and long-term survival of PBMSCs by activating the Oct4 pathway through upregulation of the expression of the antiapoptotic factors Bcl2 and survivin and the proangiogenic cytokine bFGF and suppression of the levels of the proapoptotic factors Bax and cleaved caspase-3. β-Catenin overexpression increased Oct4 expression. β-Catenin knockdown suppressed Oct4 expression in PBMSCs. However, β-catenin levels were not affected by Oct4 overexpression or knockdown. Chromatin immunoprecipitation assays proved that β-catenin directly regulates Oct4 transcription in PBMSCs. In vivo, PBMSCs overexpressing β-catenin showed high survival in infarcted hearts and resulted in better myocardial repair. Further functional analysis identified Oct4 as the direct upstream regulator of Ang1, bFGF, HGF, VEGF, Bcl2, and survivin, which cooperatively drive antiapoptosis and angiogenesis of engrafted PBMSCs. These findings revealed the regulation of β-catenin in PBMSCs by the Oct4-mediated antiapoptotic/proangiogenic signaling axis and provide a breakthrough point for improving the long-term survival and therapeutic effects of PBMSCs.

Cardiac resynchronization therapy in heart failure patients by using left bundle branch pacing.

BackgroundLeft bundle branch pacing (LBBP) is emerging as an effective alternative to achieve cardiac resynchronization therapy (CRT) and improve heart function. The purpose of our study was to investigate the feasibility and efficacy of LBBP in heart failure patients with left ventricular ejection fraction (LVEF) <50% and left bundle branch block (LBBB).MethodsAll patients with complete LBBB and LVEF <50% were retrospectively included in the study from April 2018 to April 2021 and underwent CRT via LBBP implantation. ECG, pacing parameters, the New York Heart Association (NYHA) functional class, echocardiographic measurements, and complications were recorded and analyzed at implant and during follow-up of 1, 6, and 12 months.ResultsLeft bundle branch pacing was successful in all 34 patients (mean age 65.6 ± 11.2 years, 67.6% men). A significant decrease in QRS duration (QRSd) was observed after the LBBP operation for 1 month (153.2 ± 1.7 vs. 111.9 ± 2.6 ms, p < 0.01). LBB capture threshold and R-wave amplitude remained stable at 12-month follow-up when compared with implantation values (0.62 ± 0.13 V @ 0.4 ms vs. 0.73 ± 0.21 V @ 0.4 ms, 12.02 ± 5.68 mV vs. 8.58 ± 4.09 mV, respectively). LVEF increased significantly (35.28 ± 1.70% vs. 51.09 ± 1.71%, p < 0.01) accompanied with reduced left ventricular end-diastolic dimension (LVEDd; 65.3 ± 1.99 vs. 53.58 ± 2.07 mm, p < 0.01) and left atrial dimension (LAD; 49.03 ± 1.32 vs. 40.67 ± 1.58 mm, p < 0.01). Normalized LVEF (LVEF ≥ 50%) was found in 70.5% of patients at 12 months. The NYHA classification, brain natriuretic peptide (BNP), and 6-minute walk test (6MWT) were significantly improved at follow-up of 12 months (all p < 0.01 vs. baseline). No deaths or heart failure hospitalizations were observed during the follow-up period.ConclusionThe current work suggested that LBBP was feasible with a high success implantation rate and effective to correct LBBB and improved left ventricular structure and function with a low and stable pacing threshold.

CXCR4+ Sorted Adipose-Derived Stem Cells Enhance Their Functional Benefits and Improve Cardiac Function after Myocardial Infarction.

Objective The homing of adipose-derived stem cells (ASCs) to infarcted myocardium, which is important for improved cardiac function, has been investigated previously, but with poor efficiency. Substantial improvements in engraftments are required to optimize ASC treatment. Stromal derived factor-1α (SDF-1α) is upregulated early after MI, and its endogenous receptor, chemokine receptor 4 (CXCR4), is pivotal in stem cell survival, migration, and engraftment. We examined whether CXCR4+ ASCs enhance their efficacy of migration and engraftment posttransplantation and improve heart function following myocardial infarction (MI). Methods and Results CXCR4+ ASC subpopulations were sorted by fluorescence-activated cell sorting. CXCR4+ sorted ASCs exhibited the stronger cell viability, the faster proliferation rate, and the better migration capability in comparison with unfractionated ASCs. CXCR4+ sorted ASCs secreted a higher level of angiogenic growth factors including VEGF, HGF, and IGF-1 relative to unfractionated ASCs. Fewer apoptotic cells under oxygen-glucose deprivation were detected in CXCR4+ sorted ASCs than in unfractionated ASCs. Osteogenic and angiogenic differentiation were more pronounced in CXCR4+ sorted ASCs than in unfractionated ASCs. At 3 days after acute MI, rats were randomly allocated to receive intramyocardial injection of cell culture medium, CXCR4+ sorted ASCs, and unfractionated ASCs. Left ventricular function was assessed echocardiographically 4 weeks thereafter. Explanted hearts were then processed for the immunofluorescence detection of survived cells, quantification of angiogenesis, and cell engraftment. CXCR4+ sorted ASCs more obviously engrafted into infarcted myocardium, more markedly inhibited collagen remodeling, and more effectively improved heart function and promoted capillary formation than did unfractionated ASCs. Conclusion CXCR4+ sorted ASCs are superior to unfractionated ASCs due to better viability, faster proliferation, more cytokine secretion, and stronger migration. CXCR4+ sorted ASCs provide better curative benefits on MI than do unfractionated ASCs and can be efficiently harvested and purified from adipose tissue, they may serve as a promising candidate for MI.

Sustained over-expression of calpain-2 induces age-dependent dilated cardiomyopathy in mice through aberrant autophagy.

Calpains have been implicated in heart diseases. While calpain-1 has been detrimental to the heart, the role of calpain-2 in cardiac pathology remains controversial. In this study we investigated whether sustained over-expression of calpain-2 had any adverse effects on the heart and the underlying mechanisms. Double transgenic mice (Tg-Capn2/tTA) were generated, which express human CAPN2 restricted to cardiomyocytes. The mice were subjected to echocardiography at age 3, 6, 8 and 12 months, and their heart tissues and sera were collected for analyses. We showed that transgenic mice over-expressing calpain-2 restricted to cardiomyocytes had normal heart function with no evidence of cardiac pathological remodeling at age 3 months. However, they exhibited features of dilated cardiomyopathy including increased heart size, enlarged heart chambers and heart dysfunction from age 8 months; histological analysis revealed loss of cardiomyocytes replaced by myocardial fibrosis and cardiomyocyte hypertrophy in transgenic mice from age 8 months. These cardiac alterations closely correlated with aberrant autophagy evidenced by significantly increased LC3BII and p62 protein levels and accumulation of autophagosomes in the hearts of transgenic mice. Notably, injection of 3-methyladenine, a well-established inhibitor of autophagy (30 mg/kg, i.p. once every 3 days starting from age 6 months for 2 months) prevented aberrant autophagy, attenuated myocardial injury and improved heart function in the transgenic mice. In cultured cardiomyocytes, over-expression of calpain-2 blocked autophagic flux by impairing lysosomal function. Furthermore, over-expression of calpain-2 resulted in lower levels of junctophilin-2 protein in the heart of transgenic mice and in cultured cardiomyocytes, which was attenuated by 3-methyladenine. In addition, blockade of autophagic flux by bafilomycin A (100 nM) induced a reduction of junctophilin-2 protein in cardiomyocytes. In summary, transgenic over-expression of calpain-2 induces age-dependent dilated cardiomyopathy in mice, which may be mediated through aberrant autophagy and a reduction of junctophilin-2. Thus, a sustained increase in calpain-2 may be detrimental to the heart.

Dexmedetomidine attenuates myocardial ischemia/reperfusion-induced ferroptosis via AMPK/GSK-3β/Nrf2 axis

The present study aimed to investigate whether dexmedetomidine (Dex) exerts cardioprotection effect through inhibiting ferroptosis. Myocardial ischemia/reperfusion injury (MIRI) was induced in Sprague-Dawley rats in Langendorff preparation. The hemodynamic parameters were recorded. Triphenyltetrazolium chloride (TTC) staining was used to determine infarct size. In the in vitro study, the model of hypoxia/reoxygenation (HR) was established in H9c2 cells. Cell viability and apoptosis were detected using cell counting kit 8 (CCK-8), and AV/PI dual staining respectively. Lipid peroxidation as measured by the fluorescence of the fatty acid analog C11-BODIPY581/591 probe and intracellular ferrous iron levels were measured by fluorescence of Phen Green SK (PGSK) probe, whereas immunofluorescence and transmission electron microscopy were also used to examine ferroptosis. Protein levels were investigated by Western blot. The interactions of AMPK/GSK-3β signaling with Nrf2 were also assessed through AMPK inhibition and GSK-3β overexpression. Our findings indicated that Dex significantly alleviated myocardial infarction, improved heart function, and decreased HR-induced accumulation of Fe2+ and lipid peroxidation in cardiomyocytes. Dex significantly increased the expression levels of Nrf2, SLC7A11, and GPX4. However, inhibition of Nrf2 by ML385 blunted the protective effect of Dex in HR-treated H9c2 cells. Inhibition of AMPK with a specific inhibitor or siRNA decreased the expression levels of phosphorylation of GSK-3β and Nrf2 induced by Dex. Overexpression of GSK-3β resulted in lower levels of nuclear Nrf2, whereas depression of GSK-3β enhanced expressions of nuclear Nrf2. In conclusion, Dex protects hearts against MIRI-induced ferroptosis via activation of Nrf2 through AMPK/GSK-3β signaling pathway.