Damaged Heart Tissue Research Articles

Expression of apelin is related to oxidative damage in heart tissue of rats during chronic systemic hypoxia

Background: Chronic systemic hypoxia is severe environmental stress for the heart and might lead to the development of heart failure. Apelin is an endogenous peptide that has been shown to have various beneficial effects on cardiac function. Apelin appears to have a role to play in the ventricular dysfunction and maintaining the performance of the heart.
 Objectives: In the present study we want to investigate the adaptive response of heart tissue to chronic systemic hypoxia and the correlation with apelin expression and oxidative stress in rat. 
 Methods: An experimental study was performed using 28 Sprague-Dawley male rats, 8 weeks of age. Rats were divided into 7 groups 4 each, namely control group; normoxia (O2 atmosphere) and the treatment group of hypoxia (8% O2) for 6 hours; 1;3;5;7 and 14 days respectively. Body weight and heart weight were measured at each treatment. Ventricular thickness was measured by caliper, Apelin mRNA was measured using real-time qRT-PCR with Livak formula and malondialdehyde (MDA) level was used to assess oxidative stress due to cardiac tissue hypoxia.
 Results: Macroscopic exams showed hypertrophy at day 7th. The relative expression of Apelin mRNA in hypoxic heart is decreased at the beginning and then increased, starting from day-7 to day-14. The MDA levels were significantly increased from day-7 and were strongly correlated with relative expression Apelin.
 Conclusion: It is concluded that the increase of Apelin expression is related to oxidative stress in heart tissue of rats during chronic systemic hypoxia.

Evaluation of serum C-reactive protein and lipid profile in patients with myocardial infarction

Background and objective: Myocardial infarction is the irreversible death (necrosis) of heart muscle secondary to prolonged lack of oxygen supply (ischemia), when the blood supply to a part of the heart is interrupted, most commonly due to rupture of a vulnerable plaque. The resulting ischemia or oxygen shortage causes damage and potential death of heart tissue. It is a medical emergency, and the leading cause of death worldwide. In this study, we investigated the association of serum C-reactive protein and serum lipid profile with myocardial infarction. Methods: A cross-sectional study was carried out from January to May 2016 in College of Medicine, Hawler Medical University. The study involved 108 patients with myocardial infarction (70 men and 38 women) in comparison with 50 healthy individuals as the control group (29 men and 21 women). Results: The levels of serum C-reactive protein were significantly higher (P <0.05) in patients with myocardial infarction in both genders when compared with the control group. There was no statistically significant difference in serum total cholesterol, serum triglyceride and serum LDL-C in patients with myocardial infarction and control group. Regarding serum high-density lipoprotein (HDL-C), there was a statistically significant difference (P <0.01) in patients with myocardial infarction when compared with the control group. Conclusion: C-reactive protein may play an important role in providing clinicians and biochemists with valuable information regarding diagnosis and following up the patient with suspected myocardial infarction.

Beta-glucan prevents toxic effects of 2,3,7,8-TCDD in terms of oxidative and histopathological damage in heart tissue of rats

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a widespread environmental contaminant which causes severe toxic effects. Despite there is some suggestion concerning with TCDD induced cardiotoxicity such as formation of free radicals, the main mechanism has not been entirely explained. Beta-glucan is known as strong antioxidant matter and can scavenge free radicals. Therefore this study aimed to investigate the protective effects of beta-glucan against TCDD induced cardiotoxicity in rats. In this study, 2-3 months of age and 190-250 g in weight 32 rats were randomly divided into four equal groups (n=8 for each group). Group 1 was control; Group 2 was TCDD group (2 µg/kg/week); group 3 was the beta-glucan group(50 mg/kg/day), and group 4 was TCDD and beta-glucan treatment group. The heart samples were taken from rats after 21 days treatment. The results were shown that Despite TCDD exposure visibly caused to increase (p ≤ 0.001) in TBARS levels, It caused a visible decline in the levels of GSH, CAT, GSH-Px, and SOD. However Beta glucan significantly increased GSH, CAT, GSH-Px, SOD levels and decreased generation of TBARS. Additionally, our histopathological observations were in agreement with the biochemical results. In conclusion, Beta-glucan treatment exhibited protective activity on TCDD induced cardiotoxicity.

Tet2 Deficiency in Macrophages Undermines Heart Repair after Infarction

Background: Clonal hematopoiesis of indeterminate potential (CHIP) is often observed during aging[1]. CHIP is characterized by a clonal expansion of subset blood-cell clones without other hematological abnormalities. Recent studies reported a strong connection between CHIP and cardiovascular disease (CVD). Individuals with mutations in epigenetic regulators (e.g., DNMT3A, TET2, ASXL1 and JAK2) have a higher risk for CVD[2]. In vivo studies using mouse models confirmed that Tet2-deficient HSPCs exhibited clonal expansion. Furthermore, mice transferred with Tet2-deficient HSPCs showed increased risk of atherosclerosis and worse outcome after permanent left anterior descending artery (LAD) ligation induced myocardial infarction (MI)[3,4]. Macrophages were found to be one of the most affected cell types in Tet2 deficient hematopoietic system associated with increased CVD risk[3,4]. Tet2 deficiency in macrophages is known to cause aberrant innate immune response[5]. Tet2 knockout (KO) macrophages provide a protective microenvironment to prevent melanoma progression[6], suggesting the pivotal role of Tet2 in regulating macrophage function in different context. In this study, we aim to dissect the molecular mechanism on how Tet2 deficiency disrupts normal macrophage function during heart repair.Methods: We crossed Tet2f/f mice with lysMCre mice to yield macrophage specific Tet2 deficient mice (Tet2f/f-lysMCre). We performed LAD ligation in Tet2f/f-lysMCre mice to induce MI. Age and gender matched lysMCre mice were used as controls. Cardiac function was monitored by echocardiogram every week after MI for 4 weeks. Then we sacrificed mice and performed histological analysis to evaluate heart damage and repairs in lysMCre and Tet2f/f-lysMCre mice. During the course of the experiments, we collected peripheral blood and bone marrows to examine the impact of Tet2 loss on macrophages in response to heart damage and repair. In parallel, we also collected heart tissue from lysMCre and Tet2f/f-lysMCre mice at 1 and 4 weeks after LAD ligation followed by single-cell RNA-seq analysis to further dissect the underlying molecular mechanism.Results: Prior to MI, no significant difference in heart function and macrophage numbers were observed between lysMCre and Tet2f/f-lysMCre mice at the age of 6-8 weeks old. Upon LAD-induced MI, we observed worse heart function in Tet2f/f-lysMCre mice compared to lysMCre mice. Tet2f/f-lysMCre mice showed ~40% reduction in ejection fraction and ~50% decrease in fraction shortening compared to lysMCre mice (n = 15). Further histological analysis revealed >2-fold increase in scar areas and infarcted areas in Tet2f/f-lysMCre compared to lysMCre mice. Single cell analysis confirmed a substantial increase of the fibroblast population in Tet2f/f-lysMCre mice upon LAD ligation. Furthermore, we also observed altered expression of a large fraction of genes related to macrophage activation and tissue repair capability, suggesting that Tet2 plays important roles in regulating macrophages function within damaged heart tissues. Further epigenomic analysis on sorted cardiac-specific macrophages is anticipated provide more valuable mechanistic information.Conclusion: Taken together, our data suggest that Tet2 deficient macrophages play an important role during heart damage and repair. Inactivation mutations of TET2 detected in CHIP patients might lead to impaired macrophage function during heart damage and therefore increase the CVD risk.

Proteasomal Protein Degradation: Adaptation of Cellular Proteolysis With Impact on Virus-and Cytokine-Mediated Damage of Heart Tissue During Myocarditis.

Viral myocarditis is an inflammation of the heart muscle triggered by direct virus-induced cytolysis and immune response mechanisms with most severe consequences during early childhood. Acute and long-term manifestation of damaged heart tissue and disturbances of cardiac performance involve virus-triggered adverse activation of the immune response and both immunopathology, as well as, autoimmunity account for such immune-destructive processes. It is a matter of ongoing debate to what extent subclinical virus infection contributes to the debilitating sequela of the acute disease. In this review, we conceptualize the many functions of the proteasome in viral myocarditis and discuss the adaptation of this multi-catalytic protease complex together with its implications on the course of disease. Inhibition of proteasome function is already highly relevant as a strategy in treating various malignancies. However, cardiotoxicity and immune-related adverse effects have proven significant hurdles, representative of the target's wide-ranging functions. Thus, we further discuss the molecular details of proteasome-mediated activity of the immune response for virus-mediated inflammatory heart disease. We summarize how the spatiotemporal flexibility of the proteasome might be tackled for therapeutic purposes aiming to mitigate virus-mediated adverse activation of the immune response in the heart.

Resistin promotes cardiac homing of mesenchymal stem cells and functional recovery after myocardial ischemia-reperfusion via the ERK1/2-MMP-9 pathway.

Stem cell therapy is a potentially effective and promising treatment for ischemic heart disease. Resistin, a type of adipokine, has been found to bind to adipose-derived mesenchymal stem cells (ADSCs). However, the effects of resistin on cardiac homing by ADSCs and on ADSC-mediated cardioprotective effects have not been investigated. ADSCs were obtained from enhanced green fluorescent protein transgenic mice. C57BL/6J mice were subjected to myocardial ischemia-reperfusion (I/R) or sham operations. Six hours after the I/R operation, mice were intravenously injected with resistin-treated ADSCs (ADSC-resistin) or vehicle-treated ADSCs (ADSC-vehicle). Cardiac homing by ADSCs and cardiomyocyte apoptosis were investigated 3 days after I/R. Cardiac function, fibrosis, and angiogenesis were evaluated 4 wk after I/R. Cellular and molecular mechanisms were investigated in vitro using cultured ADSCs. Both immunostaining and flow cytometric experiments showed that resistin treatment promoted ADSC myocardial homing 3 days after intravenous injection. Echocardiographic experiments showed that ADSC-resistin, but not ADSC-vehicle, significantly improved left ventricular ejection fraction. ADSC-resistin transplantation significantly mitigated I/R-induced fibrosis and reduced atrial natriuretic peptide/brain natriuretic peptide mRNA expression. In addition, cardiomyocyte apoptosis was reduced, whereas angiogenesis was increased by ADSC-resistin treatment. At the cellular level, resistin promoted ADSC proliferation and migration but did not affect H2O2-induced apoptosis. Molecular experiments identified the ERK1/2-matrix metalloproteinase-9 pathway as a key component mediating the effects of resistin on ADSC proliferation and migration. These results demonstrate that resistin can promote homing of injected ADSCs into damaged heart tissue and stimulate functional recovery, an effect mediated through the ERK1/2 signaling pathway and matrix metalloproteinase-9. NEW & NOTEWORTHY First, intravenous injection of adipose-derived mesenchymal stem cells (ADSCs) treated with resistin significantly increased angiogenesis and reduced myocardial apoptosis and fibrosis in a murine model of ischemia-reperfusion, resulting in improved cardiac performance. Second, resistin treatment significantly increased myocardial homing of intravenously delivered ADSCs. Finally, the ERK1/2-matrix metalloproteinase 9 pathway contributed to the higher proliferative and migratory capacities of ADSCs treated with resistin.

심근유래의 줄기세포 프라이밍 및 조직공학 기술에 의한 심혈관 재생 전략

The prevalence and mortality rate of cardiovascular disease continue to increase despite the development of new drugs and treatments. Stem cell therapy is a promising strategy to repair and/or regenerate damaged cardiac tissue. Cardiac progenitor cells may be stronger candidates than other stem cells for cardiac cell therapy. Cardiac progenitor cells (CPCs) residing in the heart (also referred to as cardiosphere-derived cells (CDCs) exert a therapeutic potential in repairing heart damage. Numerous studies have identified candidate CPC cell surface markers, including c-kit, stem cell antigen 1 (Sca1), and platelet-derived growth factor receptor α (PDGFRα). CPCs are capable of differentiating into multiple mature cardiac cell types, including cardiomyocytes (CM), smooth muscle cells (SMC), and endothelial cells (EC). Owing to their unique pluripotency, various pre-clinical and clinical studies are being conducted using cardiac progenitor cells to regenerate damaged heart tissues. However, poor stem cell survival and low engraftment efficiency underlie significant reductions in therapeutic efficacy. To overcome current limitations that reduce stem cell therapeutic efficacy, many methods have been implemented that aim to improve stem cell survival and engraftment. Recently, stem cell priming and tissue engineering technologies have been suggested to enhance stem cell therapeutic efficacy. It is possible to increase survival and engraftment of cardiac progenitor cells in injured cardiac tissue by cell priming and tissue engineering technologies before use. In this review, we provide an understanding of multiple therapeutic approaches including cell priming, scaffolds, tissue engineering, 3D printing techniques and clinical prospect for cardiovascular regeneration using patient-derived CPCs.

Scientists Regrow Damaged Heart Tissue Using Stem Cells

Scientists Regrow Damaged Heart Tissue Using Stem Cells

The interstitium in cardiac repair: role of the immune-stromal cell interplay.

Cardiac regeneration, that is, restoration of the original structure and function in a damaged heart, differs from tissue repair, in which collagen deposition and scar formation often lead to functional impairment. In both scenarios, the early-onset inflammatory response is essential to clear damaged cardiac cells and initiate organ repair, but the quality and extent of the immune response vary. Immune cells embedded in the damaged heart tissue sense and modulate inflammation through a dynamic interplay with stromal cells in the cardiac interstitium, which either leads to recapitulation of cardiac morphology by rebuilding functional scaffolds to support muscle regrowth in regenerative organisms or fails to resolve the inflammatory response and produces fibrotic scar tissue in adult mammals. Current investigation into the mechanistic basis of homeostasis and restoration of cardiac function has increasingly shifted focus away from stem cell-mediated cardiac repair towards a dynamic interplay of cells composing the less-studied interstitial compartment of the heart, offering unexpected insights into the immunoregulatory functions of cardiac interstitial components and the complex network of cell interactions that must be considered for clinical intervention in heart diseases.

Abstract 204: Temporal Assessment of Human iPSC-Derived Cardiomyocytes to Assess the Maturity for Cardiac Repair Applications

Cardiovascular disease is the major cause of heart failure following myocardial infarction (MI), which leads to death in acute condition. In the recent year, stem cell therapy has shown a great potential to repair the damaged heart tissue following an MI. Both adult and embryonic stem cells (ES) have potential to repair and regenerate tissue to compensate cell death during MI. Apart from ethical concern, there are several advantages of using human iPSC cardiomyocytes (hiPSC-CMs) over human ES. Most important, the hiPSC-CMs provides autologous cells source which one side eliminate the possibility of cellular rejection while on the other side enhance the possibility of its survival in damaged cardiac tissue. However, the lack of maturity in hiPSC-CMs is a major challenge to replicate and/or replace the adult cardiomyocytes with mature cardiomyocytes at the site of MI. Temporal assessment of cardiac maturity markers and structural gene in hiPSC-CMs cultured in vitro for up to four weeks and comparison with non-failing human heart (NF). The wk-4 hiPSC-CMs has shown an increase in cardiac transcription factor (2-fold, NKX-2.5); Myosin genes (2-3 fold, MYH7, MYHL2); cardiac troponin-T (3-4 fold, TNNI3 and TNNT3); K + channel genes (20-fold, KCNJ2); Ca 2+ related genes (10-fold, CASQ2); Gap-junction genes (2-fold, GJA1) and Na + Channel gene (5-fold, SCN5A). Further, TEM showed that the myofibrils in the wk-4 cardiomyocytes were more compact, aligned and organized. The Z and I-band and specifically M-band were also prominent in the wk-4 sarcomeres. Furthermore, the maturity of hiPSC-CMs was compared with the NF human heart. This study showed a time-course assessment of cardiomyocytes morphology, structural and expression of cardiac maturity genes in hiPSC-CMs cultured for up to four weeks in vitro . Based on the study of the cardiac transcription factor, Na-K channel-related gene and TEM analysis, wk-4 cardiomyocytes showed more maturity than week-1 cardiomyocytes. Studies are ongoing to compare the contractility and action potential of hiPSC-CMs. Finally, the mature hiPSC-CMs will provide autologous cell source and have a significant impact on the functional outcome of patients with acute MI.

Risk of Infective Endocarditis After Invasive Dental Treatments: Case-Only Study.

Invasive dental treatments (IDTs) can yield temporary bacteremia and have therefore been considered a potential risk factor of infective endocarditis (IE). It is hypothesized that, through the trauma caused by IDTs, bacteria gain entry to the bloodstream and may attach to abnormal heart valves or damaged heart tissue, giving rise to IE. However, the association between IDTs and IE remains controversial. The aim of this study is to estimate the association between IDTs and IE. The data in this study were obtained from the Health Insurance Database in Taiwan. We selected 2 case-only study designs, case-crossover and self-controlled case series, to analyze the data. The advantage of these methods is that confounding factors that do not vary with time are adjusted for implicitly. In the case-crossover design, a conditional logistic regression model with exposure to IDTs was used to estimate the risks of IE following an IDT with 4, 8, 12, and 16 weeks delay, respectively. In the self-controlled case series design, a conditional Poisson regression model was used to estimate the risk of IE for the risk periods of 1 to 4, 5 to 8, 9 to 12, and 13 to 16 weeks following an IDT. In total, 9120 and 8181 patients with IE were included in case-crossover design and self-controlled case series design, respectively. In the case-crossover design, 277 cases and 249 controls received IDTs during the exposure period, and the odds ratio was 1.12 (95% confidence interval, 0.94-1.34) for 4 weeks. In the self-controlled case series design, we observed that 407 IEs occurred during the first 4 weeks after IDTs, and the age-adjusted incidence rate ratio was 1.14 (95% confidence interval, 1.02-1.26) for 1 to 4 weeks after IDTs. In both study designs, we did not observe a clinically larger risk for IE in the short periods after IDTs. We also found no association between IDTs and IE among patients with a high risk of IE. Therefore, antibiotic prophylaxis for the prevention of IE is not required for the Taiwanese population.

Reversible effects of anabolic steroid abuse on cyto-architectures of the heart, kidneys and testis in adult male mice

The importance of the present study comes from the lack of sufficient information about the reversibility of the histopathological alterations which may result from anabolic androgenic drugs abuse after some times of stop treatment, as it is one of the prior studies which explored the negative effects of Deca-Durabolin abuse in particular on the hearts, kidneys and testis structures. For this aim, study was performed on 40 male adult mices. Animals were divided into five groups of 8 animals each as follows: treated by Deca-Durabolin (nandrolone decanoate) at 30 g/kg of BW, weekly during one month (GI); two months (GII); three months (GIII); three months followed by six weeks of treatment discontinuation (GIV) and Control (C). Cytohistological exam was performed to determine histopathological damage in heart, kidney and testis tissues. Results showed that the treated animals supported very well the administrated substance. The increase in muscle strength and the absence of aggression were the most noticeable traits in longer-term treated groups. In addition, the gains in body and heart weights increase with duration of treatment and even more after stopping treatment. Our study showed important degenerative changes and disorganization of the histological structure of heart, kidney and testis in the animals of GIII. These damages worsen again 6 weeks after stopping treatment in heart and kidney, and repairs incompletely in the testis. In conclusion, these results confirmed that the use of AAS is associated with a lot of deleterious effects on the cardiac, nephritic and gonadic tissues which cannot be reversible.

Anti-apoptotic effects of adipose-derived adherent stromal cells in mesenchymal stem cells exposed to oxidative stress.

We investigated the expression levels of proteins associated with oxidation, inflammation, and apoptosis in MSCs co-cultured with isolated ADASs from 6 donors' SVFs under oxidative stress conditions. Our results imply that isolated ADASs from SVFs may inhibit oxidative stress-induced cell cycle arrest and/or apoptosis in MSCs via a p53-dependent pathway. Furthermore, we identified an anti-apoptotic mechanism involving oxidative stress-induced apoptosis by adipose-derived ADASs in MSCs for the first time. Our findings suggest that the positive effects of SVF implantation into damaged heart tissue may be attributed to the various actions of MSCs.

PTEN signaling inhibitor VO-OHpic improves cardiac myocyte survival by mediating apoptosis resistance in vitro

BackgroundAcute myocardial infarction (AMI) is a server disease effecting a large population worldwide. The pathophysiological process of ischemic/reperfusion (I/R) plays an important role for heart tissue damage. VO-OHpic, a PTEN inhibitor, has been demonstrated to be cardiac protective in sudden cardiac arrest models, but its role in AMI remains unclear. MethodsAn isolated AMI model was induced by dissecting the rat heart in a Langendorff system. Cardiac myocytes were extracted and induced ischemia in vitro. VO-OHpic was added into the above systems. The area of infarcted tissue in the heart was measured. Cardiac myocyte apoptosis was assessed by flow cytometry. Activation of Akt and GSK3β was quantified by flow cytometry. IL-10 levels were determined by ELISA. ResultsVO-OHpic reduced infarcted areas in the isolated heart, and improved cultured cardiac myocyte survival. VO-OHpic induced apoptosis resistance in cardiac myocytes. Akt-GSK3β signaling was activated by VO-OHpic administration. IL-10 levels in the medium were elevated by VO-OHpic. ConclusionVO-OHpic protects heart tissue by apoptosis resistance via activating Akt-GSK3β signaling and increasing IL-10 levels.

Quantification of DNA Damage in Heart Tissue as a Novel Prediction Tool for Therapeutic Prognosis

The understanding of the genetic and molecular pathogenesis of dilated cardiomyopathy (DCM) is rapidly increasing. Especially, accumulation of DNA damage and activation of DNA damage response (DDR) have been observed in the failing heart. However, these scientific findings are still far from the clinical application. Among various pathogenic signatures of DDR, Poly ADP-Ribose (PAR) is a well known functional marker and known to be synthesized immediately after DNA damage occurred. Here, we conducted immunofluorescence staining of PAR on the specimens of myocardial biopsy from DCM patients to verify its utility for predicting the response to medical therapy.

Methylphenidate clinically oral doses improved brain and heart glutathione redox status and evoked renal and cardiac tissue injury in rats

Methylphenidate (MPH) is a first-line stimulant drug to treat attention deficit hyperactivity disorder (ADHD). Overdiagnosis of ADHD and MPH abuse lead to serious concerns about the possible long-term adverse consequences of MPH in healthy children and adolescents. We aimed to evaluate MPH effects in adolescent male Wistar rats (postnatal day 40) using an oral dose scheme (2 daily MPH doses 5 mg/kg in a 5% sucrose solution, 5 h apart, for 7 days) that mimics the therapeutic doses given to human adolescents. Twenty-four hours after the last MPH administration, rats were sacrificed and brain areas [cerebellum, prefrontal cortex (PFC), hippocampus, and striatum], peripheral organs (liver, heart, and kidneys), and blood were collected for biochemical and histological analysis.MPH treatment did not alter rats’ body temperature or weight, neither food or water intake throughout the experiment. The ratio of reduced glutathione/oxidized glutathione (GSH/GSSG) significantly increased in the PFC and hippocampus of MPH-treated rats, meanwhile protein carbonylation remained unchanged in the brain. In the heart, the GSH/GSSG ratio and GSH levels were significantly increased, with decreased GSSG, while histology revealed significant damage, namely interstitial edema, vascular congestion, and presence of a fibrin-like material in the interstitial space. In the kidneys, MPH treatment resulted in extensive necrotic areas with cellular disorganization and cell infiltration, and immunohistochemistry analysis revealed a marked activation of nuclear factor-ĸB.This study showed that clinically relevant oral MPH doses improve the GSH redox status in the brain and heart, but evoke heart and kidney tissue damage to adolescent rats.

Telomere elongation protects heart and lung tissue cells from fatal damage in rats exposed to severe hypoxia

BackgroundThe effects of acute hypoxia at high altitude on the telomere length of the cells in the heart and lung tissues remain unclear. This study aimed to investigate the change in telomere length of rat heart and lung tissue cells in response to acute exposure to severe hypoxia and its role in hypoxia-induced damage to heart and lung tissues.MethodsForty male Wistar rats (6-week old) were randomized into control group (n = 10) and hypoxia group (n = 30). Rats in control group were kept at an altitude of 1500 m, while rats in hypoxia group were exposed to simulated hypoxia with an altitude of 5000 m in a low-pressure oxygen chamber for 1, 3, and 7 days (n = 10). The left ventricular and right middle lobe tissues of each rat were collected for measurement of telomere length and reactive oxygen species (ROS) content, and the mRNA and protein levels of telomerase reverse transcriptase (TERT), hypoxia-inducible factor1α (HIF-1α), and hypoxia-inducible factor1α (HIF-2α).ResultsIncreased exposure to hypoxia damaged rat heart and lung tissue cells and increased ROS production and telomere length. The mRNA and protein levels of TERT and HIF-1α were significantly higher in rats exposed to hypoxia and increased with prolonged exposure; mRNA and protein levels of HIF-2α increased only in rats exposed to hypoxia for 7 days. TERT was positively correlated with telomere length and the levels of HIF-1α but not HIF-2α.ConclusionsAcute exposure to severe hypoxia causes damage to heart and lung tissues due to the production of ROS but promotes telomere length and adaptive response by upregulating TERT and HIF-1α, which protect heart and lung tissue cells from fatal damage.

Automatic quantification of microscopic heart damage in a mouse model of Duchenne muscular dystrophy using optical polarization tractography.

Quantification of microscopic myocardium damage in a diseased heart is important in studying disease progression and evaluating treatment outcome. However, it is challenging to use traditional histology and existing medical imaging modalities to quantify all microscopic damages in a small animal heart. Here, a method was developed for fast visualization and quantification of focal tissue damage in the mouse heart based on the fiber alignment index of the local myofiber organization obtained in optical polarization tractography (OPT). This method was tested in freshly excised hearts of the mdx4cv mouse, a commonly used mouse model for studying Duchenne cardiomyopathy. The hearts of age-matched C57BL/6 mice were also imaged as the normal controls. The results revealed a significant amount of damage in the mdx4cv hearts. Histology comparisons confirmed the damage identified by OPT. This fast and automatic method may greatly enhance preclinical studies in murine models of heart diseases.

Functional Relevance of Macrophage-mediated Inflammation to Cardiac Regeneration.

Cardiovascular disease remains the leading cause of death worldwide and regenerative medicine is a promising therapeutic option for this disease. We have developed various techniques to attenuate the cardiac remodeling and to regenerate cardiovascular systems via stem cell application. Besides cell therapy, we are interested in the modulation of pathological inflammation mediated by macrophages in the damaged heart tissue to arouse endogenous reparative responses with biocompatible small molecules. Certainly, current understanding of mechanisms of tissue regeneration will lead to the development of innovative regenerative medicine for cardiovascular disease.

Abstract 21206: Manf, a Structurally Unique Redox-Sensitive Chaperone, Restores ER-Protein Folding in the Ischemic Heart

Rationale: In cardiomyocytes, most secreted and membrane proteins are synthesized and folded in the sarcoplasmic/endoplasmic reticulum (SR/ER). We previously showed that during myocardial ischemia, decreased oxygen creates a reducing environment in the SR/ER, preventing protein disulfide isomerases (PDIs) from forming disulfide bonds in nascent proteins, causing ER stress, i.e. the toxic accumulation of unfolded proteins which contributes to cardiomyocyte death. In response to ER stress, the transcription factor, ATF6 induces chaperones that restore SR/ER protein folding. We found that ATF6 also induces mesencephalic astrocyte-derived neurotrophic factor (MANF), a recently identified protein of unknown function. MANF is structurally unique, so its function cannot be inferred from other proteins. Since MANF is induced by ATF6, is ER-localized, and possesses a conserved pattern of cysteines found in all known species of MANF, we hypothesized that MANF is a redox-regulated chaperone that optimizes cardiomyocyte viability during ischemia. Methods: The ability of MANF to bind misfolded proteins during reductive ER stress or ischemia were assessed in neonatal rat ventricular myocytes (NRVM). The ability of recombinant MANF (rMANF) to suppress aggregation of misfolded proteins was examined in an in vitro chaperone assay. Finally, the effects of MANF loss-of-function in the ischemic heart, in vivo , were determined by generating a transgenic mouse model that expresses a cardiomyocyte-specific MANF-targeted microRNA. Results: In NRVM subjected to reductive ER stress or simulated ischemia, MANF formed disulfide-linked complexes with misfolded proteins. Under reducing conditions, rMANF suppressed aggregation of model misfolded proteins in vitro , and mutant rMANF in which the cysteine residues were mutated to alanine did not suppress misfolded protein aggregation. MANF knockdown in the heart, in vivo , increased damage from myocardial infarction, and an AAV9-based gene therapy approach rescued the effects of MANF deficiency, in vivo . Conclusions: MANF is a redox-sensitive SR/ER-resident chaperone that is a critical contributor to SR/ER protein folding during the adaptive ER stress response and decreases tissue damage in the ischemic heart.