Neonatal cardiomyocyte ploidy reveals critical windows of heart development

Polyploidy Promotes Hypertranscription, Apoptosis Resistance, and Ciliogenesis in Cancer Cells and Mesenchymal Stem Cells of Various Origins: Comparative Transcriptome In Silico Study

Mesenchymal stem cells (MSC) attract an increasing amount of attention due to their unique therapeutic properties. Yet, MSC can undergo undesirable genetic and epigenetic changes during their propagation in vitro. In this study, we investigated whether polyploidy can compromise MSC oncological safety and therapeutic properties. For this purpose, we compared the impact of polyploidy on the transcriptome of cancer cells and MSC of various origins (bone marrow, placenta, and heart). First, we identified genes that are consistently ploidy-induced or ploidy-repressed through all comparisons. Then, we selected the master regulators using the protein interaction enrichment analysis (PIEA). The obtained ploidy-related gene signatures were verified using the data gained from polyploid and diploid populations of early cardiomyocytes (CARD) originating from iPSC. The multistep bioinformatic analysis applied to the cancer cells, MSC, and CARD indicated that polyploidy plays a pivotal role in driving the cell into hypertranscription. It was evident from the upregulation of gene modules implicated in housekeeping functions, stemness, unicellularity, DNA repair, and chromatin opening by means of histone acetylation operating via DNA damage associated with the NUA4/TIP60 complex. These features were complemented by the activation of the pathways implicated in centrosome maintenance and ciliogenesis and by the impairment of the pathways related to apoptosis, the circadian clock, and immunity. Overall, our findings suggest that, although polyploidy does not induce oncologic transformation of MSC, it might compromise their therapeutic properties because of global epigenetic changes and alterations in fundamental biological processes. The obtained results can contribute to the development and implementation of approaches enhancing the therapeutic properties of MSC by removing polyploid cells from the cell population.

Cardiovascular Remodeling Post-Ischemia: Herbs, Diet, and Drug Interventions

Cardiovascular disease (CVD) is a serious health burden with increasing prevalence, and CVD continues to be the principal global source of illness and mortality. For several disorders, including CVD, the use of dietary and medicinal herbs instead of pharmaceutical drugs continues to be an alternate therapy strategy. Despite the prevalent use of synthetic pharmaceutical medications, there is currently an unprecedented push for the use of diet and herbal preparations in contemporary medical systems. This urge is fueled by a number of factors, the two most important being the common perception that they are safe and more cost-effective than modern pharmaceutical medicines. However, there is a lack of research focused on novel treatment targets that combine all these strategies-pharmaceuticals, diet, and herbs. In this review, we looked at the reported effects of pharmaceutical drugs and diet, as well as medicinal herbs, and propose a combination of these approaches to target independent pathways that could synergistically be efficacious in treating cardiovascular disease.

Long-Term Transcriptomic Changes and Cardiomyocyte Hyperpolyploidy after Lactose Intolerance in Neonatal Rats

Many cardiovascular diseases originate from growth retardation, inflammation, and malnutrition during early postnatal development. The nature of this phenomenon is not completely understood. Here we aimed to verify the hypothesis that systemic inflammation triggered by neonatal lactose intolerance (NLI) may exert long-term pathologic effects on cardiac developmental programs and cardiomyocyte transcriptome regulation. Using the rat model of NLI triggered by lactase overloading with lactose and the methods of cytophotometry, image analysis, and mRNA-seq, we evaluated cardiomyocyte ploidy, signs of DNA damage, and NLI-associated long-term transcriptomic changes of genes and gene modules that differed qualitatively (i.e., were switched on or switched off) in the experiment vs. the control. Our data indicated that NLI triggers the long-term animal growth retardation, cardiomyocyte hyperpolyploidy, and extensive transcriptomic rearrangements. Many of these rearrangements are known as manifestations of heart pathologies, including DNA and telomere instability, inflammation, fibrosis, and reactivation of fetal gene program. Moreover, bioinformatic analysis identified possible causes of these pathologic traits, including the impaired signaling via thyroid hormone, calcium, and glutathione. We also found transcriptomic manifestations of increased cardiomyocyte polyploidy, such as the induction of gene modules related to open chromatin, e.g., "negative regulation of chromosome organization", "transcription" and "ribosome biogenesis". These findings suggest that ploidy-related epigenetic alterations acquired in the neonatal period permanently rewire gene regulatory networks and alter cardiomyocyte transcriptome. Here we provided first evidence indicating that NLI can be an important trigger of developmental programming of adult cardiovascular disease. The obtained results can help to develop preventive strategies for reducing the NLI-associated adverse effects of inflammation on the developing cardiovascular system.

Polyploidy and Myc Proto-Oncogenes Promote Stress Adaptation via Epigenetic Plasticity and Gene Regulatory Network Rewiring

Polyploid cells demonstrate biological plasticity and stress adaptation in evolution; development; and pathologies, including cardiovascular diseases, neurodegeneration, and cancer. The nature of ploidy-related advantages is still not completely understood. Here, we summarize the literature on molecular mechanisms underlying ploidy-related adaptive features. Polyploidy can regulate gene expression via chromatin opening, reawakening ancient evolutionary programs of embryonality. Chromatin opening switches on genes with bivalent chromatin domains that promote adaptation via rapid induction in response to signals of stress or morphogenesis. Therefore, stress-associated polyploidy can activate Myc proto-oncogenes, which further promote chromatin opening. Moreover, Myc proto-oncogenes can trigger polyploidization de novo and accelerate genome accumulation in already polyploid cells. As a result of these cooperative effects, polyploidy can increase the ability of cells to search for adaptive states of cellular programs through gene regulatory network rewiring. This ability is manifested in epigenetic plasticity associated with traits of stemness, unicellularity, flexible energy metabolism, and a complex system of DNA damage protection, combining primitive error-prone unicellular repair pathways, advanced error-free multicellular repair pathways, and DNA damage-buffering ability. These three features can be considered important components of the increased adaptability of polyploid cells. The evidence presented here contribute to the understanding of the nature of stress resistance associated with ploidy and may be useful in the development of new methods for the prevention and treatment of cardiovascular and oncological diseases.

Polyploidy as a Fundamental Phenomenon in Evolution, Development, Adaptation and Diseases

DNA replication during cell proliferation is 'vertical' copying, which reproduces an initial amount of genetic information. Polyploidy, which results from whole-genome duplication, is a fundamental complement to vertical copying. Both organismal and cell polyploidy can emerge via premature cell cycle exit or via cell-cell fusion, the latter giving rise to polyploid hybrid organisms and epigenetic hybrids of somatic cells. Polyploidy-related increase in biological plasticity, adaptation, and stress resistance manifests in evolution, development, regeneration, aging, oncogenesis, and cardiovascular diseases. Despite the prevalence in nature and importance for medicine, agri- and aquaculture, biological processes and epigenetic mechanisms underlying these fundamental features largely remain unknown. The evolutionarily conserved features of polyploidy include activation of transcription, response to stress, DNA damage and hypoxia, and induction of programs of morphogenesis, unicellularity, and longevity, suggesting that these common features confer adaptive plasticity, viability, and stress resistance to polyploid cells and organisms. By increasing cell viability, polyploidization can provide survival under stressful conditions where diploid cells cannot survive. However, in somatic cells it occurs at the expense of specific function, thus promoting developmental programming of adult cardiovascular diseases and increasing the risk of cancer. Notably, genes arising via evolutionary polyploidization are heavily involved in cancer and other diseases. Ploidy-related changes of gene expression presumably originate from chromatin modifications and the derepression of bivalent genes. The provided evidence elucidates the role of polyploidy in evolution, development, aging, and carcinogenesis, and may contribute to the development of new strategies for promoting regeneration and preventing cardiovascular diseases and cancer.

Neonatal Heart Responds to Pressure Overload With Differential Alterations in Various Cardiomyocyte Maturation Programs That Accommodate Simultaneous Hypertrophy and Hyperplasia

Pressure overload is one of the pathophysiological conditions commonly associated with right-sided congenital heart disease (CHD). Patients suffer from this condition right after birth. However, little is known about how neonatal heart reacts to it. We have previously established a pulmonary artery banding (PAB) model in neonatal rat. Here we show that PAB accelerated transition of mononuclear cardiomyocytes into multinucleated cells to promote hypertrophic growth in neonatal heart. The elevated afterload significantly increased the mitotic activities of neonatal cardiomyocytes. Consistent with the proliferative potential, the elevated pressure overload also increased cytokinetic marker counts of cardiomyocytes. Using cardiomyocyte-specific lineage tracing, we noticed a clonal expansion of rare unlabeled cardiomyocytes in the PAB group, revealing a subgroup of cardiomyocytes with a strong capability of proliferation. In addition, PAB hearts at post-banding day 7 didn’t have the accumulation of macrophages, which is an immune response essential for neonatal heart regeneration in injury models. Transcriptomic analyses revealed that neonatal PAB induced an expression profile featuring both cardiomyocyte hypertrophy, such as highly activated translation, oxidative phosphorylation, and mitochondrial biogenesis programs etc., and immature cardiomyocyte, such as enhanced cell cycle activities and glycolytic metabolism, down-regulated cytoskeleton and ion channel gene expression, and maintenance of fetal-specific sarcomeric isoforms etc. It indicates that pressure overload has differential impacts on various cardiomyocyte maturation (CM) programs that may contribute to the concurrent cardiomyocyte hypertrophy and hyperplasia. The bivalent status of transcriptional profile highlights the plasticity of neonatal cardiomyocytes that can be exploited to adapt the postnatal environment.

Cardiac interstitial tetraploid cells can escape replicative senescence in rodents but not large mammals

Cardiomyocyte ploidy has been described but remains obscure in cardiac interstitial cells. Ploidy of c-kit+ cardiac interstitial cells was assessed using confocal, karyotypic, and flow cytometric technique. Notable differences were found between rodent (rat, mouse) c-kit+ cardiac interstitial cells possessing mononuclear tetraploid (4n) content, compared to large mammals (human, swine) with mononuclear diploid (2n) content. In-situ analysis, confirmed with fresh isolates, revealed diploid content in human c-kit+ cardiac interstitial cells and a mixture of diploid and tetraploid content in mouse. Downregulation of the p53 signaling pathway provides evidence why rodent, but not human, c-kit+ cardiac interstitial cells escape replicative senescence. Single cell transcriptional profiling reveals distinctions between diploid versus tetraploid populations in mouse c-kit+ cardiac interstitial cells, alluding to functional divergences. Collectively, these data reveal notable species-specific biological differences in c-kit+ cardiac interstitial cells, which could account for challenges in extrapolation of myocardial from preclinical studies to clinical trials.

Regulation of cardiomyocyte maturation during critical perinatal window

A primary limitation in the use of pluripotent stem cell-derived cardiomyocytes (PSC-CMs) for both patient health and scientific investigation is the failure of these cells to achieve full functional maturity. In vivo, cardiomyocytes undergo numerous adaptive structural, functional and metabolic changes during maturation. By contrast, PSC-CMs fail to fully undergo these developmental processes, instead remaining arrested at an embryonic stage of maturation. There is thus a significant need to understand the biological processes underlying proper CM maturation in vivo. Here, we discuss what is known regarding the initiation and coordination of CM maturation. We postulate that there is a critical perinatal window, ranging from embryonic day 18.5 to postnatal day 14 in mice, in which the maturation process is exquisitely sensitive to perturbation. While the initiation mechanisms of this process are unknown, it is increasingly clear that maturation proceeds through interconnected regulatory circuits that feed into one another to coordinate concomitant structural, functional and metabolic CM maturation. We highlight PGC1α, SRF and the MEF2 family as transcription factors that may potentially mediate this cross-talk. We lastly discuss several emerging technologies that will facilitate future studies into the mechanisms of CM maturation. Further study will not only produce a better understanding of its key processes, but provide practical insights into developing a robust strategy to produce mature PSC-CMs.

Cytogenetic and Transcriptomic Analysis of Human Endometrial MSC Retaining Proliferative Activity after Sublethal Heat Shock

Temperature is an important exogenous factor capable of leading to irreversible processes in the vital activity of cells. However, the long-term effects of heat shock (HS) on mesenchymal stromal cells (MSC) remain unstudied. We investigated the karyotype and DNA repair drivers and pathways in the human endometrium MSC (eMSC) survived progeny at passage 6 after sublethal heat stress (sublethal heat stress survived progeny (SHS-SP)). G-banding revealed an outbreak of random karyotype instability caused by chromosome breakages and aneuploidy. Molecular karyotyping confirmed the random nature of this instability. Transcriptome analysis found homologous recombination (HR) deficiency that most likely originated from the low thermostability of the AT-rich HR driving genes. SHS-SP protection from transformation is provided presumably by low oncogene expression maintained by tight co-regulation between thermosensitive HR drivers BRCA, ATM, ATR, and RAD51 (decreasing expression after SHS), and oncogenes mTOR, MDM2, KRAS, and EGFR. The cancer-related transcriptomic features previously identified in hTERT transformed MSC in culture were not found in SHS-SP, suggesting no traits of malignancy in them. The entrance of SHS-SP into replicative senescence after 25 passages confirms their mortality and absence of transformation features. Overall, our data indicate that SHS may trigger non-tumorigenic karyotypic instability due to HR deficiency and decrease of oncogene expression in progeny of SHS-survived MSC. These data can be helpful for the development of new therapeutic approaches in personalized medicine.

The roles of mechanotransduction, vascular wall cells, and blood cells in atheroma induction

BACKGROUND

This paper describes and analyzes the cellular and molecular mechanisms underlying atherosclerosis development. In particular, the roles of monocytes/macrophages, smooth muscle cells, and vascular endothelium in the formation of stable/unstable atheromatous plaques, and the contributions of some processes to atheroma formation.

METHODS AND RESULTS

In this study we analyzed endothelium: function, dysfunction, and involvement into atherogenesis; cell proteins mediating mechanotransduction; proatherogenic role of monocytes; the role of macrophages in the development of unstable atheromatous plaques and smooth muscle cell origin in atherosclerosis. Smooth muscle cell phenotypic switching; their functioning; the ability to retain cholesterol and lipoproteins as well as secretion of pro- and anti-inflammatory molecules and extracellular matrix proteins, their response to extracellular stimuli secreted by other cells, and the effect of smooth muscle cells on the cells surrounding atheromatous plaques are fundamentally important for the insight into atherosclerosis molecular basis.

CONCLUSION

Atheromatous plaque transcriptome studies will be helpful in the identification of the key genes involved in atheroma transformation and development as well as discovery of the new targets for diagnosis and therapy.

Glucocorticoids, antenatal corticosteroid therapy and fetal heart maturation

Glucocorticoids are essential in mammals to mature fetal organs and tissues in order to survive after birth. Hence, antenatal glucocorticoid treatment (termed antenatal corticosteroid therapy) can be life-saving in preterm babies and is commonly used in women at risk of preterm birth. While the effects of glucocorticoids on lung maturation have been well described, the effects on the fetal heart remain less clear. Experiments in mice have shown that endogenous glucocorticoid action is required to mature the fetal heart. However, whether the potent synthetic glucocorticoids used in antenatal corticosteroid therapy have similar maturational effects on the fetal heart is less clear. Moreover, antenatal corticosteroid therapy may increase the risk of cardiovascular disease in adulthood. Here, we present a narrative review of the evidence relating to the effects of antenatal glucocorticoid action on the fetal heart and discuss the implications for antenatal corticosteroid therapy.

Somatic polyploidy is associated with the upregulation of c-MYC interacting genes and EMT-like signature

The dependence of cancer on overexpressed c-MYC and its predisposition for polyploidy represents a double puzzle. We address this conundrum by cross-species transcription analysis of c-MYC interacting genes in polyploid vs. diploid tissues and cells, including human vs. mouse heart, mouse vs. human liver and purified 4n vs. 2n mouse decidua cells. Gene-by-gene transcriptome comparison and principal component analysis indicated that c-MYC interactants are significantly overrepresented among ploidy-associated genes. Protein interaction networks and gene module analysis revealed that the most upregulated genes relate to growth, stress response, proliferation, stemness and unicellularity, as well as to the pathways of cancer supported by MAPK and RAS coordinated pathways. A surprising feature was the up-regulation of epithelial-mesenchymal transition (EMT) modules embodied by the N-cadherin pathway and EMT regulators from SNAIL and TWIST families. Metabolic pathway analysis also revealed the EMT-linked features, such as global proteome remodeling, oxidative stress, DNA repair and Warburg-like energy metabolism. Genes associated with apoptosis, immunity, energy demand and tumour suppression were mostly down-regulated. Noteworthy, despite the association between polyploidy and ample features of cancer, polyploidy does not trigger it. Possibly it occurs because normal polyploidy does not go that far in embryonalisation and linked genome destabilisation. In general, the analysis of polyploid transcriptome explained the evolutionary relation of c-MYC and polyploidy to cancer.

Transgenerational epigenetics: the role of maternal effects in cardiovascular development

Transgenerational epigenetics, the study of non-genetic transfer of information from one generation to the next, has gained much attention in the past few decades due to the fact that, in many instances, epigenetic processes outweigh direct genetic processes in the manifestation of aberrant phenotypes across several generations. Maternal effects, or the influences of maternal environment, phenotype, and/or genotype on offsprings' phenotypes, independently of the offsprings' genotypes, are a subcategory of transgenerational epigenetics. Due to the intimate role of the mother during early development in animals, there is much interest in investigating the means by which maternal effects can shape the individual. Maternal effects are responsible for cellular organization, determination of the body axis, initiation and maturation of organ systems, and physiological performance of a wide variety of species and biological systems. The cardiovascular system is the first to become functional and can significantly influence the development of other organ systems. Thus, it is important to elucidate the role of maternal effects in cardiovascular development, and to understand its impact on adult cardiovascular health. Topics to be addressed include: (1) how and when do maternal effects change the developmental trajectory of the cardiovascular system to permanently alter the adult's cardiovascular phenotype, (2) what molecular mechanisms have been associated with maternally induced cardiovascular phenotypes, and (3) what are the evolutionary implications of maternally mediated changes in cardiovascular phenotype?

Maternal obesity and the developmental programming of hypertension: a role for leptin

Mother-child cohort studies have established that both pre-pregnancy body mass index (BMI) and gestational weight gain are independently associated with cardio-metabolic risk factors in young adult offspring, including systolic and diastolic blood pressure. Animal models in sheep and non-human primates provide further evidence for the influence of maternal obesity on offspring cardiovascular function, whilst recent studies in rodents suggest that perinatal exposure to the metabolic milieu of maternal obesity may permanently change the central regulatory pathways involved in blood pressure regulation. Leptin plays an important role in the central control of appetite, is also involved in activation of efferent sympathetic pathways to both thermogenic and non-thermogenic tissues, such as the kidney, and is therefore implicated in obesity-related hypertension. Leptin is also thought to have a neurotrophic role in the development of the hypothalamus, and altered neonatal leptin profiles secondary to maternal obesity are associated with permanently altered hypothalamic structure and function. In rodent studies, maternal obesity confers persistent sympathoexcitatory hyper-responsiveness and hypertension acquired in the early stages of development. Experimental neonatal hyperleptinaemia in naive rat pups provides further evidence of heightened sympathetic tone and proof of principle that hyperleptinaemia during a critical window of hypothalamic development may directly lead to adulthood hypertension. Insight from these animal models raises the possibility that early-life exposure to leptin in humans may lead to early onset essential hypertension. Ongoing mother-child cohort and intervention studies in obese pregnant women provide a unique opportunity to address associations between maternal obesity and offspring cardiovascular function. The goal of the review is to highlight the potential importance of leptin in the developmental programming of hypertension in obese pregnancy.

Early origins of heart disease: low birth weight and determinants of cardiomyocyte endowment

1. World-wide epidemiological and experimental animal studies demonstrate that adversity in fetal life, resulting in intrauterine growth restriction, programmes the offspring for a greater susceptibility to ischaemic heart disease and heart failure in adult life. 2. After cardiogenesis, cardiomyocyte endowment is determined by a range of hormones and signalling pathways that regulate cardiomyocyte proliferation, apoptosis and the timing of multinucleation/terminal differentiation. 3. The small fetus may have reduced cardiomyocyte endowment owing to the impact of a suboptimal intrauterine environment on the signalling pathways that regulate cardiomyocyte proliferation, apoptosis and the timing of terminal differentiation.

Germline deletion of FAK-related non-kinase delays post-natal cardiomyocyte mitotic arrest

The cardiomyocyte phenotypic switch from a proliferative to terminally differentiated state impacts normal heart development and pathologic myocardial remodeling, yet the signaling mechanisms that regulate this vital process are incompletely understood. Studies from our lab and others indicate that focal adhesion kinase (FAK) is a critical regulator of cardiac growth and remodeling and we found that expression of the endogenous FAK inhibitor, FAK-related non kinase (FRNK) coincided with postnatal cardiomyocyte arrest. Mis-expression of FRNK in the embryonic heart led to pre-term lethality associated with reduced cardiomyocyte proliferation and led us to speculate that the postnatal FRNK surge might be required to promote quiescence in this growth promoting environment. Herein, we provide strong evidence that endogenous FRNK contributes to post-mitotic arrest. Depletion of FRNK promoted DNA synthesis in post-natal day (P) 10 hearts accompanied by a transient increase in DNA content and multi-nucleation by P14, indicative of DNA replication without cell division. Interestingly, a reduction in tri- and tetra-nucleated cardiomyocytes, concomitant with an increase in bi-nucleated cells by P21, indicated the possibility that FRNK-depleted cardiomyocytes underwent eventual cytokinesis. In support of this conclusion, Aurora B-labeled central spindles (a hallmark of cytokinesis) were observed in tetra-nucleated P20 FRNK(-/-) but not wt cardiomyocytes, while no evidence of apoptosis was observed. Moreover, hearts from FRNK null mice developed ventricular enlargement that persisted until young adulthood which resulted from myocyte expansion rather than myocyte hypertrophy or interstitial growth. These data indicate that endogenous FRNK serves an important role in limiting DNA synthesis and regulating the un-coupling between DNA synthesis and cytokinesis in the post-natal myocardium.

Developmental trajectories, critical windows and phenotypic alteration during cardio-respiratory development

Embryo-environment interactions affecting cardio-respiratory development in vertebrates have been extensively studied, but an equally extensive conceptual framework for interpreting and interrelating these developmental events has lagged behind. In this review, we consider the conceptual constructs of "developmental plasticity", "critical windows", "developmental trajectory" and related concepts as they apply to both vertebrate and invertebrate development. Developmental plasticity and the related phenomenon of "heterokairy" are considered as a subset of phenotypic plasticity, and examples of cardiovascular, respiratory and metabolic plasticity illustrate the variable outcomes of embryo-environment interactions. The concept of the critical window is revealed to be overarching in cardio-respiratory development, and events originating within a critical window, potentially mitigated by "self-repair" capabilities of the embryo, are shown to result in modified developmental trajectories and, ultimately, modified adult phenotype. Finally, epigenetics, fetal programming and related phenomena are considered in the context of potentially life-long cardio-respiratory phenotypic modification resulting from embryo-environment interactions.

Somatic polyploidy promotes cell function under stress and energy depletion: evidence from tissue-specific mammal transcriptome

Polyploid cells show great among-species and among-tissues diversity and relation to developmental mode, suggesting their importance in adaptive evolution and developmental programming. At the same time, excessive polyploidization is a hallmark of functional impairment, aging, growth disorders, and numerous pathologies including cancer and cardiac diseases. To shed light on this paradox and to find out how polyploidy contributes to organ functions, we review here the ploidy-associated shifts in activity of narrowly expressed (tissue specific) genes in human and mouse heart and liver, which have the reciprocal pattern of polyploidization. For this purpose, we use the modular biology approach and genome-scale cross-species comparison. It is evident from this review that heart and liver show similar traits in response to polyploidization. In both organs, polyploidy protects vitality (mainly due to the activation of sirtuin-mediated pathways), triggers the reserve adenosine-5'-triphosphate (ATP) production, and sustains tissue-specific functions by switching them to energy saving mode. In heart, the strongest effects consisted in the concerted up-regulation of contractile proteins and substitution of energy intensive proteins with energy economic ones. As a striking example, the energy intensive alpha myosin heavy chain (providing fast contraction) decreased its expression by a factor of 10, allowing a 270-fold increase of expression of beta myosin heavy chain (providing slow contraction), which has approximately threefold lower ATP-hydrolyzing activity. The liver showed the enhancement of immunity, reactive oxygen species and xenobiotic detoxication, and numerous metabolic adaptations to long-term energy depletion. Thus, somatic polyploidy may be an ingenious evolutionary instrument for fast adaptation to stress and new environments allowing trade-offs between high functional demand, stress, and energy depletion.