Mammalian Myocardium Research Articles

Beneficial effects of the Achillea millefolium green-formulated zinc nanoparticles in mice with heart failure following myocardial infarction

Myocardial infarction is a significant contributor to illness and death on a global scale. Limited advancements have been made in regenerative therapies due to the inadequate natural regeneration of the adult mammalian myocardium and difficulties in drug delivery. Nanocarriers such as exosomes, nanoparticles, and liposomes present numerous potential benefits for treating myocardial infarction, such as enhanced drug delivery, extended, and retention therapeutic effects. Nevertheless, numerous obstacles have hindered the extensive clinical application of these technologies. Zinc nanoparticles (Zn NPs) are frequently used in the healthcare industry, specifically in cardiovascular treatments. The research documented a sustainable method for synthesizing Zn NPs by Achillea millefolium extract, utilizing eco-friendly practices. Ultraviolet–visible (UV–VIS) spectrophotometry, field emission scanning electron microscope (FE-SEM), energy dispersive X-ray (EDX), transmission electron microscopy (TEM) and Fourier-transform infrared spectroscopy (FTIR) were utilized to examine the Zn NPs, while also exploring their potential in treating myocardial infarction. The Achillea millefolium extract contains tannin at 16.49 %, phenols at 39.19 %, saponin at 14.21 %, steroids at 22.84 %, flavonoids at 7.11 %, and alkaloids at 0.16 %. The animals were classified into three separate groups: (1) isoproterenol; (2) control; (3) Zn NPs + isoproterenol (100 μg/ml). Mice were given isoproterenol to induce myocardial infarction. Real-time PCR and western blot techniques were employed to quantify the activation of PPAR-Υ/NF-κB and the subsequent release of cytokines induced by lipopolysaccharide. Following the administration of varying doses of Zn NPs, the assessment of cardiac function was carried out through biochemical, histochemical, and electrocardiogram (ECG) analysis. The nanoparticles displayed a round shape when they were created. Recent research indicates that Zn NPs exhibit cardioprotective characteristics against myocardial infarction, potentially by suppressing NF-κB signaling and stimulating PPAR-γ. Zn NPs administration led to a reduction in interleukin 6 (IL-6), IL-1β, and TNF-α in the mice hearts. The use of Zn NPs notably decreased cell death and inflammatory cytokines expression. The beneficial impacts of Zn NPs may potentially stem from the gene expression normalization in PPAR-Υ/NF-κB/ΙκB-α/ΙΚΚα/β and PPAR-Υ phosphorylation pathways. The levels of myocardial injury markers are significantly inhibited by Zn NPs, leading to a reduction in mortality rates and an amelioration in the ventricular wall infarction condition. Furthermore, the administration of Zn NPs effectively prevents the characteristic ST segment depression observed in animals with myocardial infarction.

MicroRNA205: A Key Regulator of Cardiomyocyte Transition from Proliferative to Hypertrophic Growth in the Neonatal Heart.

The mammalian myocardium grows rapidly during early development due to cardiomyocyte proliferation, which later transitions to cell hypertrophy to sustain the heart's postnatal growth. Although this cell transition in the postnatal heart is consistently preserved in mammalian biology, little is known about the regulatory mechanisms that link proliferation suppression with hypertrophy induction. We reasoned that the production of a micro-RNA(s) could serve as a key bridge to permit changes in gene expression that control the changed cell fate of postnatal cardiomyocytes. We used sequential expression analysis to identify miR205 as a micro-RNA that was uniquely expressed at the cessation of cardiomyocyte growth. Cardiomyocyte-specific miR205 deletion animals showed a 35% increase in heart mass by 3 months of age, with commensurate changes in cell cycle and Hippo pathway activity, confirming miR205's potential role in controlling cardiomyocyte proliferation. In contrast, overexpression of miR205 in newborn hearts had little effect on heart size or function, indicating a complex, probably redundant regulatory system. These findings highlight miR205's role in controlling the shift from cardiomyocyte proliferation to hypertrophic development in the postnatal period.

Myocardial matrix hydrogel acts as a reactive oxygen species scavenger and supports a proliferative microenvironment for cardiomyocytes

As the native regenerative potential of adult cardiac tissue is limited post-injury, stimulating endogenous repair mechanisms in the mammalian myocardium is a potential goal of regenerative medicine therapeutics. Injection of myocardial matrix hydrogels into the heart post-myocardial infarction (MI) has demonstrated increased cardiac muscle and promotion of pathways associated with cardiac development, suggesting potential promotion of cardiomyocyte turnover. In this study, the myocardial matrix hydrogel was shown to have native capability as an effective reactive oxygen species scavenger and protect against oxidative stress induced cell cycle inhibition in vitro. Encapsulation of cardiomyocytes demonstrated an enhanced turnover in in vitro studies, and in vivo assessments of myocardial matrix hydrogel treatment post-MI showed increased thymidine analog uptake in cardiomyocyte nuclei compared to saline controls. Overall, this study provides evidence that properties of the myocardial matrix material provide a microenvironment mitigating oxidative damage and supportive of cardiomyocytes undergoing DNA synthesis, toward possible DNA repair or cell cycle activation. Statement of significanceLoss of adult mammalian cardiomyocyte turnover is influenced by shifts in oxidative damage, which represents a potential mechanism for improving restoration of cardiac muscle after myocardial infarction (MI). Injection of a myocardial matrix hydrogel into the heart post-MI previously demonstrated increased cardiac muscle and promotion of pathways associated with cardiac development, suggesting potential in promoting proliferation of cardiomyocytes. In this study, the myocardial matrix hydrogel was shown to protect cells from oxidative stress and increase proliferation in vitro. In a rat MI model, greater presence of tissue free thiol content spared from oxidative damage, lesser mitochondrial superoxide content, and increased thymidine analog uptake in cardiomyocytes was found in matrix injected animals compared to saline controls. Overall, this study provides evidence that properties of the myocardial matrix material provide a microenvironment supportive of cardiomyocytes undergoing DNA synthesis, toward possible DNA repair or cell cycle activation.

Nanocarrier-Based Targeted Therapies for Myocardial Infarction.

Myocardial infarction is a major cause of morbidity and mortality worldwide. Due to poor inherent regeneration of the adult mammalian myocardium and challenges with effective drug delivery, there has been little progress in regenerative therapies. Nanocarriers, including liposomes, nanoparticles, and exosomes, offer many potential advantages for the therapy of myocardial infarction, including improved delivery, retention, and prolonged activity of therapeutics. However, there are many challenges that have prevented the widespread clinical use of these technologies. This review aims to summarize significant principles and developments in the field, with a focus on nanocarriers using ligand-based or cell mimicry-based targeting. Lastly, a discussion of limitations and potential future direction is provided.

Seasonal changes of electrophysiological heterogeneities in the rainbow trout ventricular myocardium.

IntroductionThermal adaptation in fish is accompanied by morphological and electrophysiological changes in the myocardium. Little is known regarding seasonal changes of spatiotemporal organization of ventricular excitation and repolarization processes. We aimed to evaluate transmural and apicobasal heterogeneity of depolarization and repolarization characteristics in the rainbow trout in-situ ventricular myocardium in summer and winter conditions.MethodsThe experiments were done in summer-acclimatized (SA, 18°C, n = 8) and winter-acclimatized (WA, 3°C, n = 8) rainbow trout (Oncorhynchus mykiss). 24 unipolar electrograms were recorded with 3 plunge needle electrodes (eight lead terminals each) impaled into the ventricular wall. Activation time (AT), end of repolarization time (RT), and activation-repolarization interval (ARI, a surrogate for action potential duration) were determined as dV/dt min during QRS-complex, dV/dt max during T-wave, and RT-AT difference, respectively.ResultsThe SA fish demonstrated relatively flat apicobasal and transmural AT and ARI profiles. In the WA animals, ATs and ARIs were longer as compared to SA animals (p≤0.001), ARIs were shorter in the compact layer than in the spongy layer (p≤0.050), and within the compact layer, the apical region had shorter ATs and longer ARIs as compared to the basal region (p≤0.050). In multiple linear regression analysis, ARI duration was associated with RR-interval and AT in SA and WA animals. The WA animals additionally demonstrated an independent association of ARIs with spatial localization across the ventricle.ConclusionCold conditions led to the spatial redistribution of repolarization durations in the rainbow trout ventricle and the formation of repolarization gradients typically observed in mammalian myocardium.

Intrauterine growth restriction elevates circulating acylcarnitines and suppresses fatty acid metabolism genes in the fetal sheep heart.

At birth, the mammalian myocardium switches from using carbohydrates as the primary energy substrate to free fatty acids as the primary fuel. Thus, a compromised switch could jeopardize normal heart function in the neonate. Placental embolization in sheep is a reliable model of intrauterine growth restriction (IUGR). It leads to suppression of both proliferation and terminal differentiation of cardiomyocytes. We hypothesized that the expression of genes regulating cardiac fatty acid metabolism would be similarly suppressed in IUGR, leading to compromised processing of lipids. Following 10 days of umbilicoplacental embolization in fetal sheep, IUGR fetuses had elevated circulating long-chain fatty acylcarnitines compared with controls (C14: CTRL 0.012 ± 0.005nmol/ml vs. IUGR 0.018 ± 0.005nmol/ml, P < 0.05; C18: CTRL 0.027 ± 0.009nmol/mol vs. IUGR 0.043 ± 0.024nmol/mol, P < 0.05, n = 12 control, n = 12 IUGR) indicative of impaired fatty acid metabolism. Uptake studies using fluorescently tagged BODIPY-C12-saturated free fatty acid in live, isolated cardiomyocytes showed lipid droplet area and number were not different between control and IUGR cells. mRNA levels of sarcolemmal fatty acid transporters (CD36, FATP6), acylation enzymes (ACSL1, ACSL3), mitochondrial transporter (CPT1), β-oxidation enzymes (LCAD, HADH, ACAT1), tricarboxylic acid cycle enzyme (IDH), esterification enzymes (PAP, DGAT) and regulator of the lipid droplet formation (BSCL2) gene were all suppressed in IUGR myocardium (P < 0.05). However, protein levels for these regulatory genes were not different between groups. This discordance between mRNA and protein levels in the stressed myocardium suggests an adaptive protection of key myocardial enzymes under conditions of placental insufficiency. KEY POINTS: The fetal heart relies on carbohydrates in utero and must be prepared to metabolize fatty acids after birth but the effects of compromised fetal growth on the maturation of this metabolic system are unknown. Plasma fatty acylcarnitines are elevated in intrauterine growth-restricted (IUGR) fetuses compared with control fetuses, indicative of impaired fatty acid metabolism in fetal organs. Fatty acid uptake and storage are not different in IUGR cardiomyocytes compared with controls. mRNA levels of genes regulating fatty acid transporter and metabolic enzymes are suppressed in the IUGR myocardium compared with controls, while protein levels remain unchanged. Mismatches in gene and protein expression, and increased circulating fatty acylcarnitines may have long-term implications for offspring heart metabolism and adult health in IUGR individuals. This requires further investigation.

Ересек егеуқұйрықтардың жүрегінің оң жақ қарынша миокардының жиырылғыштығына серотонин мен адреналиннің жоғарылаған концентрацияларының əсері

Соңғы жылдары ағзаның физиологиялық жəне патологиялық процестеріне серотониннің(5-HT) рөлі мен оның əсер ету механизмдеріне аса көңіл бөлініп келеді. Серотониндік жүйенің қалыпты жағдайдан ауытқуы атеросклероз, артериялық гипертензия, жүректің ишемиялық ауруын тудыруына себепболатыны кеңінен талқылануда. Бүгінгі таңда сүтқоректілер мен адамдардың миокардында анықталған серотонин рецепторларының екі түрі белгілі— 5-НТ2 жəне5-НТ4. Жүрек қызметін басқаратын негізгі механизмдердің бірі кардиомиоциттердің адренорецепторларына катехоламиндердің əсер етуімен байланысты. Адам мен жануарлардың жүрегінде кардиомиоциттердің жиырылуына β1, β4 жəне α1A адренорецепторлары қатысады. Серотонин мен адреналин физиологиялық процестерін реттеуші модуляторлары болып, патология жағдайында аурудың дамуына ықпал ететін факторларға айналады. Ересек ұрғашы егеуқұйрықтардың миокардының серотонин мен адреналиннің түрлі концентрацияларына жиырылу күшін in vitro зерттеу барысында анықтадық. Нəтижесінде, серотониннің концентрациясының жоғарылауымен оң қарыншаның миокардында дозаға тəуелді оң инотропты əсер байқалды. Серотониннің соңғы концентрациясына оң жақ қарыншаның жиырылу күші алғашқы концентрациясымен салыстырғанда 48,3 % жоғарылаған. Алайда, адреналин концентрациясының жоғарылауымен оң инотропты реакция əлсірейді. Адреналиннің максималды10,0 mM концентрациясына алдыңғы концентрациясымен салыстырғанда10,4 % теріс инотропты əсер байқалды. Осылайша, жүректегі серотониндік рецепторлардың таралуы мен функционалды рөлі адренергиялық рецепторлармен сəйкес болса да, кардиомиоциттердің серотонин мен адреналинге инотропты реакциясы əртүрлі болды.

Eugenol interacts with cardiac sodium channel and reduces heart excitability and arrhythmias

AimsEugenol is a natural compound found in the essential oils of many aromatic plants. The compound is used as a local anesthetic because of its inhibitory effect on the voltage-gated Na+ channels (Nav), which are expressed in the nociceptive neurons. Eugenol has shown wide range of activities in the cardiovascular system; most of these activities are attributed to the modulation of voltage-sensitive Ca2+ channels. However, its action on Nav1.5, the main subtype of Nav expressed in the mammalian myocardium, is unknown. The interaction of eugenol with Nav1.5 could also contribute to its antiarrhythmic properties in vitro and ex vivo. We investigated the compound's effect on sodium current (INa) and its possible cardiac antiarrhythmic activity. MethodsThe effect of eugenol on cardiac contractility was investigated using isolated atrium from guinea pig (for isometric force measurements). The compound's effect on INa was evaluated using human embryonic cell transiently expressing human Nav1.5 and patch-clamp technique. Key findingsEugenol caused negative inotropic and chronotropic effects in the atria. In the ex vivo arrhythmia model, eugenol decreased atrial pacing disturbance induced by ouabain. Eugenol reduced the INa in a concentration-dependent manner. Furthermore, the compound left-shifted the stationary inactivation curve, delayed recovery from inactivation of the INa, and preferentially blocked the channel in the inactivated state. Importantly, eugenol was able to attenuate the late sodium current. All these aspects are considered to be antiarrhythmic. SignificanceOverall, our findings demonstrate that eugenol has antiarrhythmic activity due, at least in part, to its interaction with Nav1.5.

Cumulative cardiotoxic effect of bleomycin in experiment

The aim of the study was to evaluate the cumulative toxic effect of bleomycin under experimental conditions&#x0D; Material and Methods. The study was conducted in the Research Institute of Transport Medicine during 2016-2021. The experimental model of the cardiotoxic effect of the bleomycin was performed using the medication "Bleocin" manufactured by Nippon Kayaku Co., Ltd. (Japan). According to the task, the study was performed on 10 mature rats of both sexes of the Wistar line with a body weight of 237 ± 20 g.&#x0D; Rats were housed in standard vivarium conditions of Odessa National Medical University. Animals were divided into 2 groups: experimental group (n = 5) and control (n = 5). Bleomycin animals of the experimental group were obtained intraperitoneally at a dose of 0.5 IU / kg on 1st and 8th days. Withdrawal of animals from the experiment was performed on the 5th, 14th and 28th day of the experiment, followed by morphological and morphometric examination.&#x0D; The material after weighing and morphometry was fixed with a neutral 10% formalin solution and poured into paraffin. Histological sections were stained with hematoxylin-eosin, MSB, Van Gizon. Performed light microscopy.&#x0D; After two weeks there was a decrease in myocardial weight by 7-10% from baseline, there were pronounced dystrophic changes in the myocardium. Repeated administration of bleomycin has a cumulative cardiotoxic effect leading to irreversible changes in the myocardium and endothelial dysfunction clinically manifested by heart attack, vascular pathology at significant cumulative doses of bleomycin. Morphofunctional changes of the right ventricle are prominent and considered to be pathognomic for bleomycin toxicity.&#x0D; Conclusions: 1. Bleomycin has a cumulative toxic effect on the myocardium of mammals&#x0D; 2. The severity of the cardiotoxic effect of bleomycin is proportional to the tissue concentration of the drug, which is proportional to the duration of exposure

Excitability and propagation of the electrical impulse in Venus flytrap; a comparative electrophysiological study of unipolar electrograms with myocardial tissue

Mammalian heart cells and cells of leaves of Dionaea muscipula share the ability to generate propagated action potentials, because the excitable cells are electrically coupled. In the heart the propagated action potential causes synchronized contraction of the heart muscle after automatic generation of the impulse in the sinus node. In Dionaea propagation results in closure of the trap after activation of trigger hairs by an insect. The electrical activity can be recorded in the extracellular space as an extracellular electrogram, resulting from transmembrane currents. Although the underlying physiological mechanism that causes the electrogram is similar for heart and Dionaea cells, the contribution of the various ions to the transmembrane current is different. We recorded extracellular electrograms from Dionaea leaves and compared the recorded signals with those known from the heart. The morphology of the electrograms differed considerably. In comparison to activation in mammalian myocardium, electrograms of Dionaea are more temporally and spatially variable. Whereas electrograms in healthy myocardium recorded at some distance from the site of activation reveal a simple biphasic pattern, Dionaea activation showed positive, negative or biphasic deflections. Comparison of patch clamp data from plant cells and cardiomyocytes suggests a role of temperature and ion concentrations in extracellular space for the diversity of morphologies of the Dionaea electrograms.

Abstract 16335: Metabolic Reprogramming From Glycolysis to Amino Acid Utilization in Cardiac Hif1 Alpha Deficient Mice

Introduction: Hypoxia is an important environmental cue implicated in several physiopathological processes, including cardiac development. Several gain of function models described before indicate that HIF1 signaling needs to be tightly regulated to ensure proper heart formation. However, there is lack of consensus about the functional outcomes of cardiac HIF1 elimination. We have previously reported that HIF1alpha expression is spatiotemporally regulated along cardiogenesis, establishing metabolic territories in the embryonic myocardium and controlling a switch from glycolysis to fatty acid oxidation (FAO) essential for chamber formation and cardiomyocyte maturation. Objectives and Hypothesis: We aim to assess the consequences of cardiac deletion of HIF1alpha during heart development and identify the adaptations to HIF1 signaling loss. Based on the tight regulation of HIF1alpha expression during cardiogenesis, we anticipated significant alterations of cardiac metabolism as well as functional and structural defects in HIF1alpha mutants. Methods and Results: A new conditional Hif1alpha knock out was generated in NKX2.5 cardiac progenitors. By means of histology, electron microscopy and high-throughput genomics, proteomics and metabolomics, we found that deletion of Hif1alpha leads to impaired embryonic glycolysis without influencing cardiomyocyte size or proliferation and results in increased mitochondrial number, transient activation of amino acid response and upregulation of HIF2alpha and ATF4. HIF1alpha mutants display normal FAO metabolic profile and do not show cardiac dysfunction in the adulthood. Conclusions: We demonstrated that HIF1 signaling is dispensable for heart development and uncovered the metabolic flexibility of the mammalian embryonic myocardium, able to utilize alternative fuels to carbohydrates in contrast to other vertebrates like zebrafish. This data highlights the importance of HIF in cardiac metabolic programing and could explain the distinct proliferative and regenerative capacity of cardiomyocytes from different species in response to cardiac injury.

Novel ultrastructural findings on cardiac mitochondria of huddling Brandt's voles in mild cold environment

Reduced ambient temperature has a damaging effect on mammalian myocardium. Huddling as a cooperative behavior has evolved in social mammals as a strategy to maximize adaptation to environmental cooling. Here, we studied the effects of huddling behavior on mitochondrial morphology, number, and function in the myocardia of Brandt's voles (Lasiopodomys brandtii) under cool environmental temperatures (15 °C). Results showed (1) mitochondrial swelling and cristae disruption in the cool huddling group (CH) and cool separated group (CS). Compared to the control group (CON, 22 °C), damaged mitochondria in the cool huddling and separated groups reached >90%; however, total number of mitochondria in the CH group was similar to that in the CON group. (2) ATP synthase activity was lowest in the CS group, whereas citrate synthetase activity was maintained among the three treatment groups. (3) Bax/bcl2 protein expression in the CH and CS groups was higher than that in the CON group, whereas DNA fragmentation, nuclear number, and caspase3 activity showed no significant differences among the three groups. (4) The protein expression levels of dynamin-related protein1 and mitochondrial fission factor were highest in the CH group. (5) Both protein expression of PINK1 and phosphorylation ratio of Parkin showed the pattern CS > CH > CON. (6) Total number of mitochondria was higher in males than in females. In general, the increased mitochondrial fission level observed in huddling voles partially counteracted the decrease in myocardial mitochondria caused by the increase in autophagy.

Inducing Endogenous Cardiac Regeneration: Can Biomaterials Connect the Dots?

Heart failure (HF) after myocardial infarction (MI) due to blockage of coronary arteries is a major public health issue. MI results in massive loss of cardiac muscle due to ischemia. Unfortunately, the adult mammalian myocardium presents a low regenerative potential, leading to two main responses to injury: fibrotic scar formation and hypertrophic remodeling. To date, complete heart transplantation remains the only clinical option to restore heart function. In the last two decades, tissue engineering has emerged as a promising approach to promote cardiac regeneration. Tissue engineering aims to target processes associated with MI, including cardiomyogenesis, modulation of extracellular matrix (ECM) remodeling, and fibrosis. Tissue engineering dogmas suggest the utilization and combination of two key components: bioactive molecules and biomaterials. This chapter will present current therapeutic applications of biomaterials in cardiac regeneration and the challenges still faced ahead. The following biomaterial-based approaches will be discussed: Nano-carriers for cardiac regeneration-inducing biomolecules; corresponding matrices for their controlled release; injectable hydrogels for cell delivery and cardiac patches. The concept of combining cardiac patches with controlled release matrices will be introduced, presenting a promising strategy to promote endogenous cardiac regeneration.

Warmer, faster, stronger: Ca2+ cycling in avian myocardium.

Birds occupy a unique position in the evolution of cardiac design. Their hearts are capable of cardiac performance on par with, or exceeding that of mammals, and yet the structure of their cardiomyocytes resembles those of reptiles. It has been suggested that birds use intracellular Ca2+ stored within the sarcoplasmic reticulum (SR) to power contractile function, but neither SR Ca2+ content nor the cross-talk between channels underlying Ca2+-induced Ca2+ release (CICR) have been studied in adult birds. Here we used voltage clamp to investigate the Ca2+ storage and refilling capacities of the SR and the degree of trans-sarcolemmal and intracellular Ca2+ channel interplay in freshly isolated atrial and ventricular myocytes from the heart of the Japanese quail (Coturnix japonica). A trans-sarcolemmal Ca2+ current (ICa) was detectable in both quail atrial and ventricular myocytes, and was mediated only by L-type Ca2+ channels. The peak density of ICa was larger in ventricular cells than in atrial cells, and exceeded that reported for mammalian myocardium recorded under similar conditions. Steady-state SR Ca2+ content of quail myocardium was also larger than that reported for mammals, and reached 750.6±128.2 μmoll-1 in atrial cells and 423.3±47.2 μmoll-1 in ventricular cells at 24°C. We observed SR Ca2+-dependent inactivation of ICa in ventricular myocytes, indicating cross-talk between sarcolemmal Ca2+ channels and ryanodine receptors in the SR. However, this phenomenon was not observed in atrial myocytes. Taken together, these findings help to explain the high-efficiency avian myocyte excitation-contraction coupling with regard to their reptilian-like cellular ultrastructure.

Alterations of protein expression of phospholamban, ZASP and plakoglobin in human atria in subgroups of seniors

The mature mammalian myocardium contains composite junctions (areae compositae) that comprise proteins of adherens junctions as well as desmosomes. Mutations or deficiency of many of these proteins are linked to heart failure and/or arrhythmogenic cardiomyopathy in patients. We firstly wanted to address the question whether the expression of these proteins shows an age-dependent alteration in the atrium of the human heart. Right atrial biopsies, obtained from patients undergoing routine bypass surgery for coronary heart disease were subjected to immunohistology and/or western blotting for the plaque proteins plakoglobin (γ-catenin) and plakophilin 2. Moreover, the Z-band protein cypher 1 (Cypher/ZASP) and calcium handling proteins of the sarcoplasmic reticulum (SR) like phospholamban, SERCA and calsequestrin were analyzed. We noted expression of plakoglobin, plakophilin 2 and Cypher/ZASP in these atrial preparations on western blotting and/or immunohistochemistry. There was an increase of Cypher/ZASP expression with age. The present data extend our knowledge on the expression of anchoring proteins and SR regulatory proteins in the atrium of the human heart and indicate an age-dependent variation in protein expression. It is tempting to speculate that increased expression of Cypher/ZASP may contribute to mechanical changes in the aging human myocardium.

LYMPHATIC MICROVESSELS IN THE MYOCARDIUM: ARTIFACT OR OBJECTIVE REALITY?

Most of the current information on the lymphatic flow bed of the heart was obtained by the method of interstitial injection of various dyes, including the masses of Gerot. Low information content and numerous artifacts do not allow us to consider the data obtained by this method on lymphatic microvessels of myocardium reliable. The purpose of the work is to confirm or refute the data on the presence of lymphatic microvessels in the myocardium, using various methods for their detection. The vessels of the microvascular flow bed of the myocardium of intact experimental animals, rats (n = 7), cats (n = 3), rabbits (n = 3) was detected by the methods of Grant and Ranvier-Goyer in modification II. Markov. As a control, a universal method for the impregnation of argyrophilic structures was used. The data obtained give unambiguously reason to believe that there are no lymphatic microvessels in the myocardium of mammals.

Adult Cardiac Stem Cell Aging: A Reversible Stochastic Phenomenon?

Aging is by far the dominant risk factor for the development of cardiovascular diseases, whose prevalence dramatically increases with increasing age reaching epidemic proportions. In the elderly, pathologic cellular and molecular changes in cardiac tissue homeostasis and response to injury result in progressive deteriorations in the structure and function of the heart. Although the phenotypes of cardiac aging have been the subject of intense study, the recent discovery that cardiac homeostasis during mammalian lifespan is maintained and regulated by regenerative events associated with endogenous cardiac stem cell (CSC) activation has produced a crucial reconsideration of the biology of the adult and aged mammalian myocardium. The classical notion of the adult heart as a static organ, in terms of cell turnover and renewal, has now been replaced by a dynamic model in which cardiac cells continuously die and are then replaced by CSC progeny differentiation. However, CSCs are not immortal. They undergo cellular senescence characterized by increased ROS production and oxidative stress and loss of telomere/telomerase integrity in response to a variety of physiological and pathological demands with aging. Nevertheless, the old myocardium preserves an endogenous functionally competent CSC cohort which appears to be resistant to the senescent phenotype occurring with aging. The latter envisions the phenomenon of CSC ageing as a result of a stochastic and therefore reversible cell autonomous process. However, CSC aging could be a programmed cell cycle-dependent process, which affects all or most of the endogenous CSC population. The latter would infer that the loss of CSC regenerative capacity with aging is an inevitable phenomenon that cannot be rescued by stimulating their growth, which would only speed their progressive exhaustion. The resolution of these two biological views will be crucial to design and develop effective CSC-based interventions to counteract cardiac aging not only improving health span of the elderly but also extending lifespan by delaying cardiovascular disease-related deaths.

Characterization of a small molecule that promotes cell cycle activation of human induced pluripotent stem cell-derived cardiomyocytes

BackgroundSince regenerative capacity of adult mammalian myocardium is limited, activation of the endogenous proliferative capacity of existing cardiomyocytes is a potential therapeutic strategy for treating heart diseases accompanied by cardiomyocyte loss. Recently, we performed a compound screening and developed a new drug named TT-10 (C11H10FN3OS2) which promotes the proliferation of murine cardiomyocytes via enhancement of YES-associated protein (YAP)-transcriptional enhancer factor domain (TEAD) activity and improves cardiac function after myocardial infarction in adult mice. Methods and resultsTo test whether TT-10 can also promote the proliferative capacity of human cardiomyocytes, we investigated the efficacy of TT-10 on human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes (hiPSCMs). The hiPSCs were established from monocytes obtained from healthy donors and cardiac differentiation was performed using a chemically defined protocol. As was observed in murine cardiomyocytes, TT-10 markedly promoted cell cycle activation and increased cell division of hiPSCMs. We then evaluated other effects of TT-10 on the functional properties of hiPSCMs by gene expression and cell motion analyses. We observed that TT-10 had no unfavorable effects on the expression of functional and structural genes or the contractile properties of hiPSCMs. ConclusionsOur results suggest that the novel drug TT-10 effectively activated the cell cycle of hiPSCMs without apparent functional impairment of myocardium, suggesting the potential of clinical usefulness of this drug.

A collagen hydrogel loaded with HDAC7-derived peptide promotes the regeneration of infarcted myocardium with functional improvement in a rodent model

Myocardial infarction (MI) leads to the loss of cardiomyocytes, left ventricle (LV) dilation, and cardiac dysfunction, eventually developing into heart failure. Most of the strategies for MI therapy require biomaterials that can support tissue regeneration. In this study, we hypothesized that the extracellular matrix (ECM)-derived collagen I hydrogel loaded with histone deacetylase 7 (HDAC7)-derived-phosphorylated 7-amino-acid peptide (7Ap) could restrain LV remodeling and improve cardiac function after MI. An MI model was established by ligation of the left anterior descending coronary artery (LAD) of C57/B6 mice. The 7Ap-loaded collagen I hydrogel was intramyocardially injected to the infarcted region of the LV wall of the heart. After local delivery, the 7Ap-collagen increased neo-microvessel formation, enhanced stem cell antigen-1 positive (Sca-1+) stem cell recruitment and differentiation, decreased cellular apoptosis, and promoted cardiomyocyte cycle progression. Furthermore, the 7Ap-collagen restricted the fibrosis of the LV wall, reduced the infarct wall thinning, and improved cardiac performance significantly at 2 weeks post-MI. These results highlight the promising implication of 7Ap-collagen as a novel candidate for MI therapy. Statement of SignificanceThe mammalian myocardium has a limited regenerative capability following myocardial infarction (MI). MI leads to extensive loss of cardiomyocytes, thus culminating in adverse cardiac remodeling and congestive heart failure. In situ tissue regeneration through endogenous cell mobilization has great potential for tissue regeneration. A 7-amino-acid-peptide (7A) domain encoded by a short open-reading frame (sORF) of the HDAC7 gene. The phosphorylated from of 7A (7Ap) has been reported to promote in situ tissue repair via the mobilization and recruitment of endogenous stem cell antigen-1 positive (Sca-l+) stem cells. In this study, 7Ap was shown to improve H9C2 cell survival, in vitro. In vivo investigations in a mouse MI model demonstrated that intra-myocardial delivery of 7Ap-loaded collagen hydrogel promoted neovascularization, stimulated Sca-l+ stem cell recruitment and differentiation, reduced cardiomyocyte apoptosis and promoted cell cycle progression. As a result, treated infarcted hearts had increased wall thickness, had improved heart function and exhibited attenuation of adverse cardiac remodeling, observed for up to 2 weeks. Overall, these results highlighted the positive impact of implanting 7Ap-collagen as a novel constituent for MI repair.

In situ cardiac regeneration by using neuropeptide substance P and IGF-1C peptide eluting heart patches.

Cardiovascular diseases cause huge socio-economic burden worldwide. Although a mammalian myocardium has its own limited healing capability, scaffold materials capable of releasing stem cell recruiting/engrafting factors may facilitate the regeneration of the infarcted myocardium. The aim of this research was to develop cardiac patches capable of simultaneously eluting substance P (SP) and insulin-like growth factor-1C (IGF-1C) peptide. Polycaprolactone/collagen type 1-based patches with or without SP and IGF-1C peptide were fabricated by co-electrospinning, which exhibited nanofibrous morphology. SP and IGF-1C/SP patches recruited significantly higher numbers of bone marrow-mesenchymal stem cells than that of the negative control and patch-only groups in vitro. The developed patches were transplanted in an infarcted myocardium for up to 14 days. Mice underwent left anterior descending artery ligation and received one of the following treatments: (i) sham, (ii) saline, (iii) patch-only, (iv) IGF-1C patch, (v) SP patch and (vi) IGF-1C/SP patch. SP and IGF-1C/SP patch-treated groups exhibited better heart function and attenuated adverse cardiac remodeling than that of the saline, patch-only and individual peptide containing cardiac patches. SP patch and IGF-1C/SP patch-treated groups also showed higher numbers of CD31-positive vessels and isolectin B4-positive capillaries than that of other groups. IGF-1C/SP-treated group also showed thicker left ventricular wall in comparison to the saline and patch-only groups. Moreover, IGF-1C/SP patches recruited significantly higher numbers of CD29-positive cells and showed less numbers of Tunel-positive cells compared with the other groups. These data suggest that SP and IGF-1C peptides may act synergistically for in situ tissue repair.