Bmi1 limits dilated cardiomyopathy and heart failure by inhibiting cardiac senescence

Unraveling the Metabolic Derangements Occurring in Non-infarcted Areas of Pig Hearts With Chronic Heart Failure

Objective: After myocardial infarction (MI), the non-infarcted left ventricle (LV) ensures appropriate contractile function of the heart. Metabolic disturbance in this region greatly exacerbates post-MI heart failure (HF) pathology. This study aimed to provide a comprehensive understanding of the metabolic derangements occurring in the non-infarcted LV that could trigger cardiovascular deterioration. Methods and Results: We used a pig model that progressed into chronic HF over 3 months following MI induction. Integrated gene and metabolite signatures revealed region-specific perturbations in amino acid- and lipid metabolism, insulin signaling and, oxidative stress response. Remote LV, in particular, showed impaired glutamine and arginine metabolism, altered synthesis of lipids, glucose metabolism disorder, and increased insulin resistance. LPIN1, PPP1R3C, PTPN1, CREM, and NR0B2 were identified as the main effectors in metabolism dysregulation in the remote zone and were found differentially expressed also in the myocardium of patients with ischemic and/or dilated cardiomyopathy. In addition, a simultaneous significant decrease in arginine levels and altered PRCP, PTPN1, and ARF6 expression suggest alterations in vascular function in remote area. Conclusions: This study unravels an array of dysregulated genes and metabolites putatively involved in maladaptive metabolic and vascular remodeling in the non-infarcted myocardium and may contribute to the development of more precise therapies to mitigate progression of chronic HF post-MI.

Integrated microarray analysis to identify potential biomarkers and therapeutic targets in dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is a primary cardiomyopathy with high mortality. The aim of the present study was to identify the related genes in DCM. The four expression profiles (GSE17800, GSE21610, GSE42955 and GSE79962) downloaded from the Gene Expression Omnibus (GEO) database were analyzed using RankProd and metaMA R packages to identify differentially expressed genes (DEGs). DEGs were uploaded to the Database for Annotation, Visualization and Integrated Discovery (DAVID), for Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis. A protein-protein interaction (PPI) network of the DEGs was constructed using the STRING database. In addition, hub genes were identified using the Cytoscape plugin cytoHubba. A mouse DCM model, which established via intraperitoneal injection with doxorubicin (DOX), was used to validate the hub genes. A total of 898 DEGs were identified across the four microarrays. Furthermore, GO analysis demonstrated that these DEGs were mainly enriched in cell adhesion, negative regulation of cell proliferation, negative regulation of apoptotic process and potassium ion transport. In addition, KEGG analysis revealed that DEGs were mainly enriched in the ECM-receptor interaction, the p53 signaling pathway, cardiac muscle contraction and the hypoxia-inducible factor signaling pathway. Proenkephalin (PENK), chordin like 1 (CHRDL1), calumenin (CALU), apolipoprotein L1, insulin-like growth factor binding protein 3 (IGFBP3) and ceruloplasmin (CP) were identified as hub genes in the PPI network. Furthermore, the expression levels of PENK, CHRDL1, IGFBP3, CP and CALU in hearts with DCM were validated using a mouse model. In conclusion, the present study identified six hub genes related to DCM. Therefore, the present results may provide a potential mechanism for DCM involving these hub genes, which may serve as biomarkers for screening and diagnosis in the clinic.

Adipose Tissue Senescence and Inflammation in Aging is Reversed by the Young Milieu

Visceral adipose tissue (VAT) inflammation plays a central role in longevity and multiple age-related disorders. Cellular senescence (SEN) is a fundamental aging mechanism that contributes to age-related chronic inflammation and organ dysfunction, including VAT. Recent studies using heterochronic parabiosis models strongly suggested that circulating factors in young plasma alter the aging phenotypes of old animals. Our study investigated if young plasma rescued SEN phenotypes in the VAT of aging mice. With heterochronic parabiosis model using young (3 months) and old (18 months) mice, we found significant reduction in the levels of pro-inflammatory cytokines and altered adipokine profile that are protective of SEN in the VAT of old mice. These data are indicative of protection from SEN of aging VAT by young blood circulation. Old parabionts also exhibited diminished expression of cyclin-dependent kinase inhibitors (CDKi) genes p16 (Cdkn2a) and p21 (Cdkn1a/Cip1) in the VAT. In addition, when exposed to young serum condition in an ex vivo culture system, aging adipose tissue-derived stromovascular fraction cells produced significantly lower amounts of pro-inflammatory cytokines (MCP-1 and IL-6) compared to old condition. Expressions of p16 and p21 genes were also diminished in the old stromovascular fraction cells under young serum condition. Finally, in 3T3-preadipocytes culture system, we found reduced pro-inflammatory cytokines (Mcp-1 and Il-6) and diminished expression of cyclin-dependent kinase inhibitor genes in the presence of young serum compared to old serum. In summary, this study demonstrates that young milieu is capable of protecting aging adipose tissue from SEN and thereby inflammation.

A Young Blood Environment Decreases Aging of Senile Mice Kidneys

Whether changes in internal body environment affect kidney aging remains unclear. Specifically, it is unknown whether transplanted kidneys from older donors recover from tissue damage after placement in younger recipients. In this study, a parabiosis animal model was established to investigate the effects of a young internal body environment on aged kidneys. The animals were divided into six groups: young (Ycon) and old control (Ocon) groups, isochronic youth-youth group (Y-IP), elderly-elderly group (O-IP), and heterochronic youth (Y-HP) and elderly (O-HP) groups. After parabiosis, tubule and interstitial tissue scores in the O-HP group were significantly lower than in the Ocon and O-IP groups. The expression of aging-related protein p16 and SA-β-gal in the O-HP group was significantly reduced compared with the Ocon and O-IP groups. Autophagy factors Atg5 and LC3BII were significantly upregulated, whereas the expression of the autophagic degradation marker (P62) was significantly downregulated in the O-HP group compared with the Ocon and O-IP groups. With the same comparison, the positive cells of TUNEL staining and the expression of IL-6 and IL-1β were significantly reduced, whereas the total/cleaved caspase-3 and total/pNF-κB were significantly increased in the O-HP group. The results demonstrated that a young blood environment significantly reduces kidney aging. These findings provide new evidence supporting an increase in the upper age limit for human kidney transplantation donors.

Activation of Wnt/β-catenin signaling by lithium chloride attenuates d-galactose-induced neurodegeneration in the auditory cortex of a rat model of aging

Degeneration of the central auditory system, which is characterized by reduced understanding of speech and source localization of sounds, is an important cause of age‐related hearing loss (presbycusis). Accumulating evidence has demonstrated that Wnt/β‐catenin signaling plays an essential role in the development of the auditory system but its potential role in presbycusis remains unclear. In this study, we used a rat model of aging, created by chronic systemic exposure to d‐galactose (d‐gal), and explored changes in Wnt/β‐catenin signaling in the auditory cortex. A decrease in Wnt/β‐catenin signaling in the auditory cortex was found in both naturally aging and d‐gal‐mimetic aging rats, as indicated by increased GSK3β activity and decreased β‐catenin activity. Moreover, lithium chloride (Licl), an activator of Wnt signaling pathway, was administered long term to 15‐month‐old d‐gal‐treated rats. Activation of Wnt/β‐catenin signaling by Licl attenuated d‐gal‐induced auditory cortex apoptosis and neurodegeneration. Bmi1, a transcription factor implicated in antiaging and resistance to apoptosis, can be modulated by β‐catenin activity. Here, we showed that the expression of Bmi1 was reduced and the expression of its downstream genes, p16^INK4a, p19^Arf, and p53 were increased in the auditory cortex both of naturally aging and d‐gal‐mimetic aging rats. In addition, Licl significantly increased Bmi1 expression and reduced p16^INK4a, p19^Arf, and p53 expression. Our results indicated that decreased Wnt/β‐catenin signaling might participate in the pathogenesis of central presbycusis through modulating the expression of Bmi1. Wnt/β‐catenin signaling might be used as a potential therapeutic target against presbycusis.

Simultaneous Assessment of Cardiomyocyte DNA Synthesis and Ploidy: A Method to Assist Quantification of Cardiomyocyte Regeneration and Turnover

Although it is accepted that the heart has a limited potential to regenerate cardiomyocytes following injury and that low levels of cardiomyocyte turnover occur during normal ageing, quantification of these events remains challenging. This is in part due to the rarity of the process and the fact that multiple cellular sources contribute to myocardial maintenance. Furthermore, DNA duplication within cardiomyocytes often leads to a polyploid cardiomyocyte and only rarely leads to new cardiomyocytes by cellular division. In order to accurately quantify cardiomyocyte turnover discrimination between these processes is essential. The protocol described here employs long term nucleoside labeling in order to label all nuclei which have arisen as a result of DNA replication and cardiomyocyte nuclei identified by utilizing nuclei isolation and subsequent PCM1 immunolabeling. Together this allows the accurate and sensitive identification of the nucleoside labeling of the cardiomyocyte nuclei population. Furthermore, 4′,6-diamidino-2-phenylindole labeling and analysis of nuclei ploidy, enables the discrimination of neo-cardiomyocyte nuclei from nuclei which have incorporated nucleoside during polyploidization. Although this method cannot control for cardiomyocyte binucleation, it allows a rapid and robust quantification of neo-cardiomyocyte nuclei while accounting for polyploidization. This method has a number of downstream applications including assessing the potential therapeutics to enhance cardiomyocyte regeneration or investigating the effects of cardiac disease on cardiomyocyte turnover and ploidy. This technique is also compatible with additional downstream immunohistological techniques, allowing quantification of nucleoside incorporation in all cardiac cell types.

Aging and Autophagy in the Heart

The aging population is increasing in developed countries. Because the incidence of cardiac disease increases dramatically with age, it is important to understand the molecular mechanisms through which the heart becomes either more or less susceptible to stress. Cardiac aging is characterized by the presence of hypertrophy, fibrosis, and accumulation of misfolded proteins and dysfunctional mitochondria. Macroautophagy (hereafter referred to as autophagy) is a lysosome-dependent bulk degradation mechanism that is essential for intracellular protein and organelle quality control. Autophagy and autophagic flux are generally decreased in aging hearts, and murine autophagy loss-of-function models develop exacerbated cardiac dysfunction that is accompanied by the accumulation of misfolded proteins and dysfunctional organelles. On the contrary, stimulation of autophagy generally improves cardiac function in mouse models of protein aggregation by removing accumulated misfolded proteins, dysfunctional mitochondria, and damaged DNA, thereby improving the overall cellular environment and alleviating aging-associated pathology in the heart. Increasing lines of evidence suggest that autophagy is required for many mechanisms that mediate lifespan extension, such as caloric restriction, in various organisms. These results raise the exciting possibility that autophagy may play an important role in combating the adverse effects of aging in the heart. In this review, we discuss the role of autophagy in the heart during aging, how autophagy alleviates age-dependent changes in the heart, and how the level of autophagy in the aging heart can be restored.

Epigenetic regulation in heart failure

PURPOSE OF REVIEW

This article provides an overview, highlighting recent findings, of a major mechanism of gene regulation and its relevance to the pathophysiology of heart failure.

RECENT FINDINGS

The syndrome of heart failure is a complex and highly prevalent condition, one in which the heart undergoes substantial structural remodeling. Triggered by a wide range of disease-related cues, heart failure pathophysiology is governed by both genetic and epigenetic events. Epigenetic mechanisms, such as chromatin/DNA modifications and noncoding RNAs, have emerged as molecular transducers of environmental stimuli to control gene expression. Here, we emphasize metabolic milieu, aging, and hemodynamic stress as they impact the epigenetic landscape of the myocardium.

SUMMARY

Recent studies in multiple fields, including cancer, stem cells, development, and cardiovascular biology, have uncovered biochemical ties linking epigenetic machinery and cellular energetics and mitochondrial function. Elucidation of these connections will afford molecular insights into long-established epidemiological observations. With time, exploitation of the epigenetic machinery therapeutically may emerge with clinical relevance.

Cardiac Bmi1(+) cells contribute to myocardial renewal in the murine adult heart

Introduction

The mammalian adult heart maintains a continuous, low cardiomyocyte turnover rate throughout life. Although many cardiac stem cell populations have been studied, the natural source for homeostatic repair has not yet been defined. The Polycomb protein BMI1 is the most representative marker of mouse adult stem cell systems. We have evaluated the relevance and role of cardiac Bmi1⁺ cells in cardiac physiological homeostasis.

Methods

Bmi1^CreER/+;Rosa26^YFP/+ (Bmi1-YFP) mice were used for lineage tracing strategy. After tamoxifen (TM) induction, yellow fluorescent protein (YFP) is expressed under the control of Rosa26 regulatory sequences in Bmi1⁺ cells. These cells and their progeny were tracked by FACS, immunofluorescence and RT-qPCR techniques from 5 days to 1 year.

Results

FACS analysis of non-cardiomyocyte compartment from TM-induced Bmi1-YFP mice showed a Bmi1⁺-expressing cardiac progenitor cell (Bmi1-CPC: B-CPC) population, SCA-1 antigen-positive (95.9 ± 0.4 %) that expresses some stemness-associated genes. B-CPC were also able to differentiate in vitro to the three main cardiac lineages. Pulse-chase analysis showed that B-CPC remained quite stable for extended periods (up to 1 year), which suggests that this Bmi1⁺ population contains cardiac progenitors with substantial self-maintenance potential. Specific immunostaining of Bmi1-YFP hearts serial sections 5 days post-TM induction indicated broad distribution of B-CPC, which were detected in variably sized clusters, although no YFP⁺ cardiomyocytes (CM) were detected at this time. Between 2 to 12 months after TM induction, YFP⁺ CM were clearly identified (3 ± 0.6 % to 6.7 ± 1.3 %) by immunohistochemistry of serial sections and by flow cytometry of total freshly isolated CM. B-CPC also contributed to endothelial and smooth muscle (SM) lineages in vivo.

Conclusions

High Bmi1 expression identifies a non-cardiomyocyte resident cardiac population (B-CPC) that contributes to the main lineages of the heart in vitro and in vivo.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-015-0196-9) contains supplementary material, which is available to authorized users.