Nitric oxide determines mesodermic differentiation of mouse embryonic stem cells by activating class IIa histone deacetylases: potential therapeutic implications in a mouse model of hindlimb ischemia

Nitric Oxide Prevents Glioblastoma Stem Cells' Expansion and Induces Temozolomide Sensitization

Glioblastoma multiforme (GBM) has high mortality and recurrence rates. Malignancy resilience is ascribed to Glioblastoma Stem Cells (GSCs), which are resistant to Temozolomide (TMZ), the gold standard for GBM post-surgical treatment. However, Nitric Oxide (NO) has demonstrated anti-cancer efficacy in GBM cells, but its potential impact on GSCs remains unexplored. Accordingly, we investigated the effects of NO, both alone and in combination with TMZ, on patient-derived GSCs. Experimentally selected concentrations of diethylenetriamine/NO adduct and TMZ were used through a time course up to 21 days of treatment, to evaluate GSC proliferation and death, functional recovery, and apoptosis. Immunofluorescence and Western blot analyses revealed treatment-induced effects in cell cycle and DNA damage occurrence and repair. Our results showed that NO impairs self-renewal, disrupts cell-cycle progression, and expands the quiescent cells' population. Consistently, NO triggered a significant but tolerated level of DNA damage, but not apoptosis. Interestingly, NO/TMZ cotreatment further inhibited cell cycle progression, augmented G0 cells, induced cell death, but also enhanced DNA damage repair activity. These findings suggest that, although NO administration does not eliminate GSCs, it stunts their proliferation, and makes cells susceptible to TMZ. The resulting cytostatic effect may potentially allow long-term control over the GSCs' subpopulation.

Novel Peptides Derived from Sea Cucumber Intestine Promotes Osteogenesis by Upregulating Integrin-Mediated Transdifferentiation of Growth Plate Chondrocytes to Osteoblasts

The sea cucumber intestine is a major by-product of sea cucumber processing and contains high levels of protein. In this study, we isolated and identified 28 novel osteogenic peptides from sea cucumber intestinal hydrolysis by the activity-tracking method for the first time. In vitro experimental results showed that compared with high molecular weight, the peptides from sea cucumber intestine (SCIP) with molecular weight <3 kDa more significantly promoted the proliferation and mineralized nodules of MC3T3-E1 cell and exhibited potential integrin binding capacity. In vivo experimental results showed that the SCIP supplement significantly increased the longitudinal bone length and elevated the height of the growth plate (especially the hypertrophic zone, 37.2%, p < 0.01) in adolescent mice. Further, immunofluorescence labeling results indicated that the SCIP supplement increased chondrocyte transdifferentiate to osteoblast in the growth plate close to the diaphysis. Mechanistically, transcriptome analysis revealed that the SCIP supplement induced the dedifferentiation of chondrocyte to osteoprogenitor cell via integrin-mediated histone acetylation and then redifferentiated to osteoblast via integrin-mediated Wnt/β-catenin signaling. These results reported for the first time that sea cucumber intestine had the potential to develop into a dietary supplement for promoting osteogenic, and provide new evidence for the mechanism of dietary promotes chondrocyte to osteoblast transdifferentiation.

KLF2 up-regulates IRF4/HDAC7 to protect neonatal rats from hypoxic-ischemic brain damage

Neonatal brain hypoxic ischemic injury is a devastating event causing permanent brain damage. The current study set out to explore the role of Kruppel-like factor 2 (KLF2) and its downstream molecular mechanism on hypoxic-ischemic brain damage (HIBD) in neonatal rats. First, we adopted a modified Rice method to develop a HIBD model in postnatal day seven Sprague Dawley (SD) rat pups. Next, neuronal damage, morphological changes, and neuronal apoptosis were documented in the vulnerable hippocampal CA1 region and evaluated using Nissl staining, H&E staining, and TUNEL assay, respectively. Meanwhile, a hypoxic-ischemic model using the oxygen-glucose deprivation (OGD) method was established in cortical neurons isolated from day one SD rat pups, followed by MTT and flow cytometry detections of the cell survival rate and apoptotic ability. Experimental findings revealed that KLF2 was poorly-expressed in the brain tissues of HIBD rats and in the OGD-induced neurons. We found that KLF2 overexpression inhibited neuron apoptosis in vitro and in vivo, which was also observed to inhibit brain injury in the HIBD rats and alleviate neuronal damage of OGD-treated neurons. Besides, as dual luciferase reporter gene assay and chromatin immunoprecipitation established that KLF2 bound to the interferon regulatory factor 4 (IRF4) promoter, which promoted the binding of IRF4 in the promoter of histone deacetylase 7 (HDAC7) to augment its expression, thereby inhibiting neuronal apoptosis and brain damage. In conclusion, our findings indicated that KLF2 could increase the expression of IRF4 to up-regulate the expression of HDAC7, which protects against HIBD in neonatal rats.

NO-HDAC dual inhibitors

HDAC inhibitors and NO donors have both demonstrated independently broad therapeutic potential in a variety of diseases. Borretto et al. presented the topic of NO-HDAC dual inhibitors for the first time in 2013 as an attractive new topic. Here we collected the general structure of all synthesized NO-HDAC dual inhibitors, lead compounds, synthesis methods and biological features of the most potent dual NO-HDAC inhibitor in each category with the intention of assisting in the synthesis and optimization of new drug-like compounds for diverse diseases. Based on studies done so far, NO-HDAC dual inhibitors have displayed satisfactory results against wound healing (3), heart hypertrophy (3), inflammatory, cardiovascular, neuromuscular illnesses (11a-11e) and cancer (6a-6o, 9a-9d, 10a-10d, 16 and 17). NO-HDAC dual inhibitors can have high therapeutic potential for various diseases due to their new properties, NO properties, HDAC inhibitor properties and also due to the effects of NO on HDAC enzymes.

Regulation of endothelial cell differentiation in embryonic vascular development and its therapeutic potential in cardiovascular diseases

During vertebrate development, the cardiovascular system begins operating earlier than any other organ in the embryo. Endothelial cell (EC) forms the inner lining of blood vessels, and its extensive proliferation and migration are requisite for vasculogenesis and angiogenesis. Many aspects of cellular biology are involved in vasculogenesis and angiogenesis, including the tip versus stalk cell specification. Recently, epigenetics has attracted growing attention in regulating embryonic vascular development and controlling EC differentiation. Some proteins that regulate chromatin structure have been shown to be directly implicated in human cardiovascular diseases. Additionally, the roles of important EC signaling such as vascular endothelial growth factor and its receptors, angiopoietin-1 and tyrosine kinase containing immunoglobulin and epidermal growth factor homology domain-2, and transforming growth factor-β in EC differentiation during embryonic vasculature development are briefly discussed in this review. Recently, the transplantation of human induced pluripotent stem cell (iPSC)-ECs are promising approaches for the treatment of ischemic cardiovascular disease including myocardial infarction. Patient-specific iPSC-derived EC is a potential new target to study differences in gene expression or response to drugs. However, clinical application of the iPSC-ECs in regenerative medicine is often limited by the challenges of maintaining cell viability and function. Therefore, novel insights into the molecular mechanisms underlying EC differentiation might provide a better understanding of embryonic vascular development and bring out more effective EC-based therapeutic strategies for cardiovascular diseases.

Stem cells and new intervention measures as emerging therapy in cardiac surgery

Cardiovascular disease (CVD) presents a great burden for elderly patients, their caregivers, and health systems. Structural and functional alterations of vessels accumulate throughout life, culminating in increased risk of developing CVD. Several inflammatory pathway are involved in vascular ageing. The growing elderly population worldwide highlights the need to understand how aging promotes CVD in order to develop new strategies to confront this challenge. In this review we analyzed the role of stem cells and new intervention measures as emerging drugs for vascular aging.

Nitric-Oxide-Releasing Biomaterial Regulation of the Stem Cell Microenvironment in Regenerative Medicine

Stem cell therapy has proven to be an attractive solution for the treatment of degenerative diseases or injury. However, poor cell engraftment and survival within injured tissues limits the successful use of stem cell therapy within the clinical setting. Nitric oxide (NO) is an important signaling molecule involved in various physiological processes. Emerging evidence supports NO's diverse roles in modulating stem cell behavior, including survival, migration, differentiation, and paracrine secretion of proregenerative factors. Thus, there has been a shift in research focus to concentrate efforts on the delivery of therapeutic concentration ranges of NO to the target tissue sites. Combinatory therapies utilizing biomaterials that control NO generation and support stem cell delivery can be holistic and synergistic approaches to significantly improve tissue regeneration. Here, the focus is on recent developments of various therapeutic platforms, engineered to both transport NO and to enhance stem-cell-mediated regeneration of damaged tissues. New and emerging revelations of how the stem cell microenvironment can be regulated by NO-releasing biomaterials are also highlighted.

BDNF (Brain-Derived Neurotrophic Factor) Promotes Embryonic Stem Cells Differentiation to Endothelial Cells Via a Molecular Pathway, Including MicroRNA-214, EZH2 (Enhancer of Zeste Homolog 2), and eNOS (Endothelial Nitric Oxide Synthase)

Objective- The NTs (neurotrophins), BDNF (brain-derived neurotrophic factor) and NT-3 promote vascular development and angiogenesis. This study investigated the contribution of endogenous NTs in embryonic stem cell (ESC) vascular differentiation and the potential of exogenous BDNF to improve the process of ESC differentiation to endothelial cells (ECs). Approach and Results- Mouse ESCs were differentiated into vascular cells using a 2-dimensional embryoid body (EB) model. Supplementation of either BDNF or NT-3 increased EC progenitors' abundance at day 7 and enlarged the peripheral vascular plexus with ECs and SM22α⁺ (smooth muscle 22 alpha-positive) smooth muscle cells by day 13. Conversely, inhibition of either BDNF or NT-3 receptor signaling reduced ECs, without affecting smooth muscle cells spread. This suggests that during vascular development, endogenous NTs are especially relevant for endothelial differentiation. At mechanistic level, we have identified that BDNF-driven ESC-endothelial differentiation is mediated by a pathway encompassing the transcriptional repressor EZH2 (enhancer of zeste homolog 2), microRNA-214 (miR-214), and eNOS (endothelial nitric oxide synthase). It was known that eNOS, which is needed for endothelial differentiation, can be transcriptionally repressed by EZH2. In turn, miR-214 targets EZH2 for inhibition. We newly found that in ESC-ECs, BDNF increases miR-214 expression, reduces EZH2 occupancy of the eNOS promoter, and increases eNOS expression. Moreover, we found that NRP-1 (neuropilin 1), KDR (kinase insert domain receptor), and pCas¹³⁰ (p130 Crk-associated substrate kinase), which reportedly induce definitive endothelial differentiation of pluripotent cells, were increased in BDNF-conditioned ESC-EC. Mechanistically, miR-214 mediated the BDNF-induced expressional changes, contributing to BDNF-driven endothelial differentiation. Finally, BDNF-conditioned ESC-ECs promoted angiogenesis in vitro and in vivo. Conclusions- BDNF promotes ESC-endothelial differentiation acting via miR-214.

Zeb1-Hdac2-eNOS circuitry identifies early cardiovascular precursors in naive mouse embryonic stem cells

Nitric oxide (NO) synthesis is a late event during differentiation of mouse embryonic stem cells (mESC) and occurs after release from serum and leukemia inhibitory factor (LIF). Here we show that after release from pluripotency, a subpopulation of mESC, kept in the naive state by 2i/LIF, expresses endothelial nitric oxide synthase (eNOS) and endogenously synthesizes NO. This eNOS/NO-positive subpopulation (ESNO+) expresses mesendodermal markers and is more efficient in the generation of cardiovascular precursors than eNOS/NO-negative cells. Mechanistically, production of endogenous NO triggers rapid Hdac2 S-nitrosylation, which reduces association of Hdac2 with the transcriptional repression factor Zeb1, allowing mesendodermal gene expression. In conclusion, our results suggest that the interaction between Zeb1, Hdac2, and eNOS is required for early mesendodermal differentiation of naive mESC.

Epigenetic reprogramming converts human Wharton's jelly mesenchymal stem cells into functional cardiomyocytes by differential regulation of Wnt mediators

Background

Lineage commitment of mesenchymal stem cells (MSCs) to cardiac differentiation is controlled by transcription factors that are regulated by epigenetic events, mainly histone deacetylation and promoter DNA methylation. Here, we studied the differentiation of human Wharton’s jelly MSCs (WJMSCs) into the cardiomyocyte lineage via epigenetic manipulations.

Methods

We introduced these changes using inhibitors of DNA methyl transferase and histone deacetylase, DC301, DC302, and DC303, in various combinations. We characterized for cardiogenic differentiation by assessing the expression of cardiac-specific markers by immunolocalization, quantitative RT-PCR, and flow cytometry. Cardiac functional studies were performed by FURA2AM staining and Greiss assay. The role of Wnt signaling during cardiac differentiation was analyzed by quantitative RT-PCR. In-vivo studies were performed in a doxorubicin-induced cardiotoxic mouse model by injecting cardiac progenitor cells. Promoter methylation status of the cardiac transcription factor Nkx2.5 and the Wnt antagonist, secreted frizzled-related protein 4 (sFRP4), after cardiac differentiation was studied by bisulfite sequencing.

Results

By induction with DC301 and DC302, WJMSCs differentiated into cardiomyocyte-like structures with an upregulation of Wnt antagonists, sFRP3 and sFRP4, and Dickkopf (Dkk)1 and Dkk3. The cardiac function enhancer, vinculin, and DDX20, a DEAD-box RNA helicase, were also upregulated in differentiated cardiomyocytes. Additionally, bisulfite sequencing revealed, for the first time in cardiogenesis, that sFRP4 is activated by promoter CpG island demethylation. In vivo, these MSC-derived cardiac progenitors could not only successfully engraft to the site of cardiac injury in mice with doxorubicin-induced cardiac injury, but also form functional cardiomyocytes and restore cardiac function.

Conclusion

The present study unveils a link between Wnt inhibition and epigenetic modification to initiate cardiac differentiation, which could enhance the efficacy of stem cell therapy for ischemic heart disorders.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-017-0638-7) contains supplementary material, which is available to authorized users.

Transcription Factor CREM Mediates High Glucose Response in Cardiomyocytes and in a Male Mouse Model of Prolonged Hyperglycemia

This study aims at investigating the epigenetic landscape of cardiomyocytes exposed to elevated glucose levels. High glucose (30 mM) for 72 hours determined some epigenetic changes in mouse HL-1 and rat differentiated H9C2 cardiomyocytes including upregulation of class I and III histone deacetylase protein levels and activity, inhibition of histone acetylase p300 activity, increase in histone H3 lysine 27 trimethylation, and reduction in H3 lysine 9 acetylation. Gene expression analysis focused on cardiotoxicity revealed that high glucose induced markers associated with tissue damage, fibrosis, and cardiac remodeling such as Nexilin (NEXN), versican, cyclic adenosine 5'-monophosphate-responsive element modulator (CREM), and adrenoceptor α2A (ADRA2). Notably, the transcription factor CREM was found to be important in the regulation of cardiotoxicity-associated genes as assessed by specific small interfering RNA and chromatin immunoprecipitation experiments. In CD1 mice, made hyperglycemic by streptozotoicin (STZ) injection, cardiac structural alterations were evident at 6 months after STZ treatment and were associated with a significant increase of H3 lysine 27 trimethylation and reduction of H3 lysine 9 acetylation. Consistently, NEXN, CREM, and ADRA2 expression was significantly induced at the RNA and protein levels. Confocal microscopy analysis of NEXN localization showed this protein irregularly distributed along the sarcomeres in the heart of hyperglycemic mice. This evidence suggested a structural alteration of cardiac Z-disk with potential consequences on contractility. In conclusion, high glucose may alter the epigenetic landscape of cardiac cells. Sildenafil, restoring guanosine 3', 5'-cyclic monophosphate levels, counteracted the increase of CREM and NEXN, providing a protective effect in the presence of hyperglycemia.

Low Concentration of Sodium Nitroprusside Promotes Mesenchymal Stem Cell Viability and Proliferation Through Elevation of Metabolic Activity

Background: Sodium nitroprusside (SNP) releases nitric oxide which has signaling role. Objectives: This study was conducted to understand the role of low concentration of SNP on viability, proliferation and biochemical properties of rat bone marrow mesenchymal stem cells (MSCs). Materials and Methods: MSCs were used to evaluate the viability and morphology in presence of SNP (1 to 100 µM) at 12, 24 and 36 hours. Then 10, 50 and 100 µM of SNP as well as 24 hours were selected for further study. Cell proliferation was investigated by colony forming assay and population doubling number (PDN). Calcium (Ca2+) potassium (K+) and sodium (Na+) level as well as activity of alanine transaminase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP) and lactate dehydrogenase (LDH) were measured. Results: The MSCs viability increased when treatment with 1 and 10 µM at all the treatment periods while 90 and 100 µM caused significant reduction after 24 and 36 hours. Also 10 µM caused elevation whereas 50 and 100 µM showed reduction of proliferation ability. We observed morphological changes and significant reduction of all the investigated enzymes with 100 µM. Activity of ALT and AST were elevated with 10 µM after 24 hours, whereas LDH and ALP activities were not changed. Na+, K+ and Ca2+ was not changed due to 10 and 50 µM treatments, whereas 100 µM only elevated the level of calcium and sodium ions. Conclusions: Low concentration of SNP caused increase of viability and proliferation due to metabolic activity elevation. But the high concentration of SNP induced cell viability and proliferation reduction caused by metabolic and ionic imbalance as well as infrastructure alteration.

MC1568 inhibits HDAC6/8 activity and influenza A virus replication in lung epithelial cells: role of Hsp90 acetylation

AIM

Histone deacetylases (HDACs) regulate the life cycle of several viruses. We investigated the ability of different HDAC inhibitors, to interfere with influenza virus A/Puerto Rico/8/34/H1N1 (PR8 virus) replication in Madin-Darby canine kidney and NCI cells.

RESULTS

3-(5-(3-Fluorophenyl)-3-oxoprop-1-en-1-yl)-1-methyl-1H-pyrrol-2-yl)-N-hydroxyacrylamide (MC1568) inhibited HDAC6/8 activity and PR8 virus replication, with decreased expression of viral proteins and their mRNAs. Such an effect may be related to a decrease in intranuclear content of viral polymerases and, in turn, to an early acetylation of Hsp90, a major player in their nuclear import. Later, the virus itself induced Hsp90 acetylation, suggesting a differential and time-dependent role of acetylated proteins in virus replication.

CONCLUSION

The inhibition of HDAC6/8 activity during early steps of PR8 virus replication could lead to novel anti-influenza strategy.

The double life of cardiac mesenchymal cells: Epimetabolic sensors and therapeutic assets for heart regeneration

Organ-specific mesenchymal cells naturally reside in the stroma, where they are exposed to some environmental variables affecting their biology and functions. Risk factors such as diabetes or aging influence their adaptive response. In these cases, permanent epigenetic modifications may be introduced in the cells with important consequences on their local homeostatic activity and therapeutic potential. Numerous results suggest that mesenchymal cells, virtually present in every organ, may contribute to tissue regeneration mostly by paracrine mechanisms. Intriguingly, the heart is emerging as a source of different cells, including pericytes, cardiac progenitors, and cardiac fibroblasts. According to phenotypic, functional, and molecular criteria, these should be classified as mesenchymal cells. Not surprisingly, in recent years, the attention on these cells as therapeutic tools has grown exponentially, although only very preliminary data have been obtained in clinical trials to date. In this review, we summarized the state of the art about the phenotypic features, functions, regenerative properties, and clinical applicability of mesenchymal cells, with a particular focus on those of cardiac origin.

Anacardic acid and thyroid hormone enhance cardiomyocytes production from undifferentiated mouse ES cells along functionally distinct pathways

The epigenetics of early commitment to embryonal cardiomyocyte is poorly understood. In this work, we compared the effect of thyroid hormone and that of anacardic acid, a naturally occurring histone acetylase inhibitor, or both in combination, on mouse embryonic stem cells (mES) differentiating into embryonal cardiomyocyte by embryoid bodies (EBs) formation. Although the results indicated that anacardic acid (AA) and thyroid hormone were both efficient in promoting cardiomyocyte differentiation, we noticed that a transient exposure of mES to AA alone was sufficient to enlarge the beating areas of EBs compared to those of untreated controls. This effect was associated with changes in the chromatin structure at the promoters of specific cardiomyogenic genes. Among them, a rapid induction of the transcription factor Castor 1 (CASZ1), important for cardiomyocytes differentiation and maturation during embryonic development, was observed in the presence of AA. In contrast, thyroid hormone (T 3) was more effective in stimulating spontaneous firing, thus suggesting a role in the production of a population of cardiomyocyte with pacemaker properties. In conclusion, AA and thyroid hormone both enhanced cardiomyocyte formation along in apparently distinct pathways.

Retinoic Acid Induces Embryonic Stem Cell Differentiation by Altering Both Encoding RNA and microRNA Expression

Retinoic acid (RA) is a vitamin A metabolite that is essential for early embryonic development and promotes stem cell neural lineage specification; however, little is known regarding the impact of RA on mRNA transcription and microRNA levels on embryonic stem cell differentiation. Here, we present mRNA microarray and microRNA high-output sequencing to clarify how RA regulates gene expression. Using mRNA microarray analysis, we showed that RA repressed pluripotency-associated genes while activating ectoderm markers in mouse embryonic stem cells (mESCs). Moreover, RA modulated the DNA methylation of mESCs by altering the expression of epigenetic-associated genes such as Dnmt3b and Dnmt3l. Furthermore, H3K4me2, a pluripotent histone modification, was repressed by RA stimulation. From microRNA sequence data, we identified two downregulated microRNAs, namely, miR-200b and miR-200c, which regulated the pluripotency of stem cells. We found that miR-200b or miR-200c deficiency suppressed the expression of pluripotent genes, including Oct4 and Nanog, and activated the expression of the ectodermal marker gene Nestin. These results demonstrate that retinoid induces mESCs to differentiate by regulating miR-200b/200c. Our findings provide the landscapes of mRNA and microRNA gene networks and indicate the crucial role of miR-200b/200c in the RA-induced differentiation of mESCs.

Histone deacetylases and cardiovascular cell lineage commitment

Cardiovascular diseases (CVDs), which include all diseases of the heart and circulation system, are the leading cause of deaths on the globally. During the development of CVDs, choric inflammatory, lipid metabolism disorder and endothelial dysfunction are widely recognized risk factors. Recently, the new treatment for CVDs that designed to regenerate the damaged myocardium and injured vascular endothelium and improve recovery by the use of stem cells, attracts more and more public attention. Histone deacetylases (HDACs) are a family of enzymes that remove acetyl groups from lysine residues of histone proteins allowing the histones to wrap the DNA more tightly and commonly known as epigenetic regulators of gene transcription. HDACs play indispensable roles in nearly all biological processes, such as transcriptional regulation, cell cycle progression and developmental events, and have originally shown to be involved in cancer and neurological diseases. HDACs are also found to play crucial roles in cardiovascular diseases by modulating vascular cell homeostasis (e.g., proliferation, migration, and apoptosis of both ECs and SMCs). This review focuses on the roles of different members of HDACs and HDAC inhibitor on stem cell/ progenitor cell differentiation toward vascular cell lineages (endothelial cells, smooth muscle cells and Cardiomyocytes) and its potential therapeutics.

Transient Downregulation of Nanog and Oct4 Induced by DETA/NO Exposure in Mouse Embryonic Stem Cells Leads to Mesodermal/Endodermal Lineage Differentiation

The function of pluripotency genes in differentiation is a matter of investigation. We report here that Nanog and Oct4 are reexpressed in two mouse embryonic stem cell (mESC) lines following exposure to the differentiating agent DETA/NO. Both cell lines express a battery of both endoderm and mesoderm markers following induction of differentiation with DETA/NO-based protocols. Confocal analysis of cells undergoing directed differentiation shows that the majority of cells expressing Nanog express also endoderm genes such as Gata4 and FoxA2 (75.4% and 96.2%, resp.). Simultaneously, mRNA of mesodermal markers Flk1 and Mef2c are also regulated by the treatment. Acetylated histone H3 occupancy at the promoter of Nanog is involved in the process of reexpression. Furthermore, Nanog binding to the promoter of Brachyury leads to repression of this gene, thus disrupting mesendoderm transition.

Intramyocardial injection of hypoxia-preconditioned adipose-derived stromal cells treats acute myocardial infarction: an in vivo study in swine

Hypoxic preconditioning is a promising method for improving the anti-apoptotic and paracrine signaling capabilities of adipose-derived stromal cells (ADSCs). The purpose of this study was to analyze the influence of different hypoxic conditions on ADSCs and the therapeutic effects of hypoxia-preconditioned ADSCs (HPADSCs) on an animal model of myocardial infarction (MI). For the in vitro studies, ADSCs were divided into five groups and cultured in different oxygen concentrations (1, 3, 5, 10, and 21 %). After 24 h, RT-PCR and western blots showed that 3 % oxygen preconditioning could improve the viability and cytokine secretion of the ADSCs. A Matrigel assay indicated that the HPADSC-conditioned medium could stimulate endothelial cells to form capillary-like tubes. For the in vivo studies, MI was induced by coronary occlusion in 24 mature Chinese minipigs. The animals were divided into three groups and treated by intramyocardial injection with vehicle alone (saline group), with 1 × 10(8) ADSCs cultured in normoxic conditions (ADSCs group) or with 1 × 10(8) ADSCs precultured in 3 % oxygen (HPADSCs group). SPECT and echocardiography demonstrated that cardiac function was improved significantly in the HPADSC transplant group compared with the vehicle control group (P < 0.05). Immunofluorescence showed fewer apoptotic cells and more small- to medium-sized vessels in the HPADSC transplantation group (P < 0.05). Three percent oxygen is the optimum preconditioning treatment for ADSCs. HPADSC transplantation can prevent ventricular remodeling and reduce the infarct size.

The ciliary proteins Meckelin and Jouberin are required for retinoic acid-dependent neural differentiation of mouse embryonic stem cells

The dysfunction of the primary cilium, a complex, evolutionarily conserved, organelle playing an important role in sensing and transducing cell signals, is the unifying pathogenetic mechanism of a growing number of diseases collectively termed "ciliopathies", typically characterized by multiorgan involvement. Developmental defects of the central nervous system (CNS) characterize a subset of ciliopathies showing clinical and genetic overlap, such as Joubert syndrome (JS) and Meckel syndrome (MS). Although several knock-out mice lacking a variety of ciliary proteins have shown the importance of primary cilia in the development of the brain and CNS-derived structures, developmental in vitro studies, extremely useful to unravel the role of primary cilia along the course of neural differentiation, are still missing. Mouse embryonic stem cells (mESCs) have been recently proven to mimic brain development, giving the unique opportunity to dissect the CNS differentiation process along its sequential steps. In the present study we show that mESCs express the ciliary proteins Meckelin and Jouberin in a developmentally-regulated manner, and that these proteins co-localize with acetylated tubulin labeled cilia located at the outer embryonic layer. Further, mESCs differentiating along the neuronal lineage activate the cilia-dependent sonic hedgehog signaling machinery, which is impaired in Meckelin knock-out cells but results unaffected in Jouberin-deficient mESCs. However, both lose the ability to acquire a neuronal phenotype. Altogether, these results demonstrate a pivotal role of Meckelin and Jouberin during embryonic neural specification and indicate mESCs as a suitable tool to investigate the developmental impact of ciliary proteins dysfunction.

Epigenetic programming and risk: the birthplace of cardiovascular disease?

Epigenetics, through control of gene expression circuitries, plays important roles in various physiological processes such as stem cell differentiation and self renewal. This occurs during embryonic development, in different tissues, and in response to environmental stimuli. The language of epigenetic program is based on specific covalent modifications of DNA and chromatin. Thus, in addition to the individual identity, encoded by sequence of the four bases of the DNA, there is a cell type identity characterized by its positioning in the epigenetic "landscape". Aberrant changes in epigenetic marks induced by environmental cues may contribute to the development of abnormal phenotypes associated with different human diseases such as cancer, neurological disorders and inflammation. Most of the epigenetic studies have focused on embryonic development and cancer biology, while little has been done to explore the role of epigenetic mechanisms in the pathogenesis of cardiovascular disease. This review highlights our current knowledge of epigenetic gene regulation and the evidence that chromatin remodeling and histone modifications play key roles in the pathogenesis of cardiovascular disease through (re)programming of cardiovascular (stem) cells commitment, identity and function.

Synthesis and Biological Evaluation of the First Example of NO-Donor Histone Deacetylase Inhibitor

The NO-donor histone deacetylase inhibitor 2, formally obtained by joining Entinostat 1, a moderately selective Class I histone deacetylases (HDACs) inhibitor, to a 4-(methylaminomethyl)furoxan-3-carbonitrile scaffold, is described and its preliminary biological profile discussed. This hybrid regulates Classes I and II HDACs. Nitric oxide (NO) released by the compound activates soluble guanylate cyclase (sGC), causing Class II nuclear shuttling and chromatin modifications, with consequences on gene expression. The hybrid affects a number of micro-RNAs not modulated by its individual components; it promotes myogenic differentiation, inducing the formation of larger myotubes with significantly more nuclei per fiber, in a more efficient manner than the 1:1 mixture of its two components. The hybrid is an example of a new class of NO-donor HDACs now being developed, which should be of interest for treating a number of diseases.

Transcriptional analysis of histone deacetylase family members reveal similarities between differentiating and aging spermatogonial stem cells

The differentiation of adult stem cells involves extensive chromatin remodeling, mediated in part by the gene products of histone deacetylase (HDAC) family members. While the transcriptional downregulation of HDACs can impede stem cell self-renewal in certain contexts, it may also promote stem cell maintenance under other circumstances. In self-renewing, differentiating, and aging spermatogonial stem cells (SSCs), the gene expression dynamics of HDACs have not yet been characterized. To gain further insight with these studies, we analyzed the transcriptional profiles of six HDAC family members, previously identified to be the most highly expressed in self-renewing SSCs, during stem cell differentiation and aging. Here we discovered that in both differentiating and aging SSCs the expression of Sirt4 increases, while the expression of Hdac2, Hdac6, and Sirt1 decreases. When SSCs are exposed to the lifespan-enhancing drug rapamycin in vivo, the resultant HDAC gene expression patterns are opposite of those seen in the differentiating and aging SSCs, with increased Hdac2, Hdac6, and Sirt1 and decreased Hdac8, Hdac9, and Sirt4. Our findings suggest that HDACs important for stem cell maintenance and oxidative capacity are downregulated as adult stem cells differentiate or age. These results provide important insights into the epigenetic regulation of stem cell differentiation and aging in mammals.

A nitric oxide-dependent cross-talk between class I and III histone deacetylases accelerates skin repair

In a mouse model of skin repair we found that the class I-IIa histone deacetylase inhibitor trichostatin A accelerated tissue regeneration. Unexpectedly, this effect was suppressed by Sirtinol, a class III histone deacetylase (HDAC) (sirtuin)-selective inhibitor. The role of sirtuins (SIRTs) was then investigated by using resveratrol and a novel SIRT1-2-3 activator, the MC2562 compound we synthesized recently. Both resveratrol and MC2562 were effective in accelerating wound repair. The local administration of natural or synthetic SIRT activators, in fact, significantly accelerated skin regeneration by increasing keratinocyte proliferation. In vitro experiments revealed that the activation of SIRTs stimulated keratinocyte proliferation via endothelial NO synthase phosphorylation and NO production. In this condition, the class I member HDAC2 was found S-nitrosylated on cysteine, a post-transduction modification associated with loss of activity and DNA binding capacity. After deacetylase inhibitor or SIRT activator treatment, ChIP showed, in fact, a significant HDAC2 detachment from the promoter region of insulin growth factor I (IGF-I), fibroblast growth factor 10 (FGF-10), and Epithelial Growth Factor (EGF), which may be the final recipients and effectors of the SIRT-NO-HDAC signaling cascade. Consistently, the effect of SIRT activators was reduced in the presence of NG-nitro-L-arginine methyl ester (L-NAME), a general inhibitor of NO synthesis. In conclusion, the NO-dependent cross-talk among class III and I histone deacetylases suggests an unprecedented signaling pathway important for skin repair.

In vitro epigenetic reprogramming of human cardiac mesenchymal stromal cells into functionally competent cardiovascular precursors

Adult human cardiac mesenchymal-like stromal cells (CStC) represent a relatively accessible cell type useful for therapy. In this light, their conversion into cardiovascular precursors represents a potential successful strategy for cardiac repair. The aim of the present work was to reprogram CStC into functionally competent cardiovascular precursors using epigenetically active small molecules. CStC were exposed to low serum (5% FBS) in the presence of 5 µM all-trans Retinoic Acid (ATRA), 5 µM Phenyl Butyrate (PB), and 200 µM diethylenetriamine/nitric oxide (DETA/NO), to create a novel epigenetically active cocktail (EpiC). Upon treatment the expression of markers typical of cardiac resident stem cells such as c-Kit and MDR-1 were up-regulated, together with the expression of a number of cardiovascular-associated genes including KDR, GATA6, Nkx2.5, GATA4, HCN4, NaV1.5, and α-MHC. In addition, profiling analysis revealed that a significant number of microRNA involved in cardiomyocyte biology and cell differentiation/proliferation, including miR 133a, 210 and 34a, were up-regulated. Remarkably, almost 45% of EpiC-treated cells exhibited a TTX-sensitive sodium current and, to a lower extent in a few cells, also the pacemaker I(f) current. Mechanistically, the exposure to EpiC treatment introduced global histone modifications, characterized by increased levels of H3K4Me3 and H4K16Ac, as well as reduced H4K20Me3 and H3s10P, a pattern compatible with reduced proliferation and chromatin relaxation. Consistently, ChIP experiments performed with H3K4me3 or H3s10P histone modifications revealed the presence of a specific EpiC-dependent pattern in c-Kit, MDR-1, and Nkx2.5 promoter regions, possibly contributing to their modified expression. Taken together, these data indicate that CStC may be epigenetically reprogrammed to acquire molecular and biological properties associated with competent cardiovascular precursors.

VEGF-mediated phosphorylation of eNOS regulates angioblast and embryonic endothelial cell proliferation

To evaluate potential roles of nitric oxide (NO) in the regulation of the endothelial lineage and neovascular processes (vasculogenesis and angiogenesis) we evaluated endothelial nitric oxide synthase (eNOS) and phosphorylated eNOS (p-eNOS) expression in 7.2-8.5 days post-coitum (dpc) mouse embryos. Analysis revealed that p-eNOS((S1177)) but not P-eNOS((S617)) or P-eNOS((T495)) was expressed in a subpopulation of angioblasts (TAL-1(+)/Flk-1(+)/CD31(-)/CD34(-)/VE-Cadherin(-)) at 7.2 dpc. A role of the VEGF/Akt1/eNOS signaling pathway in the regulation of the endothelial cell (EC) lineage was suggested by the strong correlation observed between cell division and p-eNOS((S1177)) expression in both angioblasts and embryonic endothelial cells (EECs, TAL-1(+)/Flk-1(+)/CD31(+)/CD34(+)/VE-Cadherin(+)). Our studies using Akt1 null mouse embryos show a reduction in p-eNOS((S1177)) expression in angioblast and EECs that is correlated with a decrease in endothelial cell proliferation and results in changes in VEGF-induced vascular patterning. Further, we show that VEGF-mediated cell proliferation in Flk-1(+) cells in allantoic cultures is decreased by pharmacological inhibitors of the VEGF/Akt1/eNOS signaling pathways. Taken together, our findings suggest that VEGF-mediated eNOS phosphorylation on Ser1177 regulates angioblast and EEC division, which underlies the formation of blood vessels and vascular networks.

NO-β-catenin crosstalk modulates primitive streak formation prior to embryonic stem cell osteogenic differentiation

Nitric oxide (NO) has been shown to play a crucial role in bone formation in vivo. We sought to determine the temporal effect of NO on murine embryonic stem cells (ESCs) under culture conditions that promote osteogenesis. Expression profiles of NO pathway members and osteoblast-specific markers were analyzed using appropriate assays. We found that NO was supportive of osteogenesis specifically during an early phase of in vitro development (days 3-5). Furthermore, ESCs stably overexpressing the inducible NO synthase showed accelerated and enhanced osteogenesis in vitro and in bone explant cultures. To determine the role of NO in early lineage commitment, a stage in ESC differentiation equivalent to primitive streak formation in vivo, ESCs were transfected with a T-brachyury-GFP reporter. Expression levels of T-brachyury and one of its upstream regulators, β-catenin, the major effector in the canonical Wnt pathway, were responsive to NO levels in differentiating primitive streak-like cells. Our results indicate that NO may be involved in early differentiation through regulation of β-catenin and T-brachyury, controlling the specification of primitive-streak-like cells, which may continue through differentiation to later become osteoblasts.

Epigenetic landscape of pluripotent stem cells

SIGNIFICANCE

Derived from the inner cell mass of the preimplantation embryo, embryonic stem cells are prototype pluripotent stem (PS) cells that have the ability of self-renewal and differentiation into almost all cell types. Exploration of the mechanisms governing this pluripotency is important for understanding reprogramming mechanisms and stem cell behavior of PS cells and can lead to enhancing reprogramming efficiency and other applications.

RECENT ADVANCES

Induced pluripotent stem cells are recently discovered PS cells that can be derived from somatic cells by overexpression of pluripotency-related transcription factors. Recent studies have shown that transcription factors and their epigenetic regulation play important roles in the generating, maintaining, and differentiating these PS cells. Recent advances in sequencing technologies allow detailed analysis of target epigenomes and microRNAs (miRs), and have revealed unique epigenetic marks and miRs for PS cells.

CRITICAL ISSUES

Epigenetic modifications of genes include histone modifications, DNA methylation, and chromatin remodeling. Working closely with epigenetic modifiers, miRs play an important role in inducing and maintaining pluripotency.

FUTURE DIRECTIONS

The dynamic changes in epigenetic marks during reprogramming and their role in cell fate changes are being uncovered. This review focuses on these new advances in the epigenetics of PS cells.

The SDF-1/CXCR4 axis in stem cell preconditioning

We review the pivotal role of the stromal derived factor (SDF)-1 chemokine in tissue ischaemia and how it orchestrates the rapid revascularization of injured, ischaemic, and regenerating tissues via the CXC chemokine receptors CXCR4 and CXCR7. Furthermore, we discuss the effects of preconditioning (PC), which is a well-known protective phenomenon for tissue ischaemia. The positive effect of both hypoxic and acidic PC on progenitor cell therapeutic potential is reviewed, while stressing the role of the SDF-1/CXCR4 axis in this process.

Splicing of histone deacetylase 7 modulates smooth muscle cell proliferation and neointima formation through nuclear β-catenin translocation

OBJECTIVE

Vascular smooth muscle cell (SMC) proliferation has an indispensable role in the pathogenesis of vascular disease, but the mechanism is not fully elucidated. The epigenetic enzyme histone deacetylase 7 (HDAC7) is involved in endothelial homeostasis and SMC differentiation and could have a role in SMC proliferation. In this study, we sought to examine the effect of 2 HDAC7 isoforms on SMC proliferation and neointima formation.

METHODS AND RESULTS

We demonstrated that overexpression of unspliced HDAC7 (HDAC7u) could suppress SMC proliferation through downregulation of cyclin D1 and cell cycle arrest, whereas spliced HDAC7 (HDAC7s) could not. Small interfering RNA (siRNA)-mediated knockdown of HDAC7 increased SMC proliferation and induced nuclear translocation of β-catenin. Additional experiments showed that only HDAC7u could bind to β-catenin and retain it in the cytoplasm. Reporter gene assay and reverse transcription polymerase chain reaction revealed a reduction of β-catenin activity in cells overexpressing HDAC7u but not HDAC7s. Deletion studies indicated that the C-terminal region of HDAC7u is responsible for the interaction with β-catenin. However, the addition of amino acids to the N terminus of HDAC7u disrupted the binding, further strengthening our hypothesis that HDAC7s does not interact with β-catenin. The growth factor platelet-derived growth factor-BB increased the splicing of HDAC7 while simultaneously decreasing the expression of HDAC7u. Importantly, in an animal model of femoral artery wire injury, we demonstrated that knockdown of HDAC7 by siRNA aggravates neointima formation in comparison with control siRNA.

CONCLUSION

Our findings demonstrate that splicing of HDAC7 modulates SMC proliferation and neointima formation through β-catenin nuclear translocation, which provides a potential therapeutic target in vascular disease.

Nitric oxide-cyclic GMP signaling in stem cell differentiation

The nitric oxide-cyclic GMP (NO-cGMP) pathway mediates important physiological functions associated with various integrative body systems including the cardiovascular and nervous systems. Furthermore, NO regulates cell growth, survival, apoptosis, proliferation, and differentiation at the cellular level. To understand the significance of the NO-cGMP pathway in development and differentiation, studies have been conducted both in developing embryos and in stem cells. Manipulation of the NO-cGMP pathway, by employing activators and inhibitors as pharmacological probes, and genetic manipulation of NO signaling components have implicated the involvement of this pathway in the regulation of stem cell differentiation. This review focuses on some of the work pertaining to the role of NO-cGMP in the differentiation of stem cells into cells of various lineages, particularly into myocardial cells, and in stem cell-based therapy.

Stem cell senescence and regenerative paradigms

The term "cellular senescence" denotes a cellular response to several stressors that results in irreversible growth arrest, alterations of the gene expression profile, epigenetic modifications, and an altered secretome, all of which eventually impair the reparative properties of primitive cells, adding a layer of complexity to the field of regenerative medicine. The purpose of this review is to illustrate how cellular senescence could affect tissue repair and to propose interventions that aim at interfering with it.

Ex vivo acidic preconditioning enhances bone marrow ckit+ cell therapeutic potential via increased CXCR4 expression

Aims

The chemokine receptor CXCR4 modulates endothelial progenitor cell migration, homing, and differentiation, and plays a key role in cardiovascular regeneration. Here we examined the effect of ex vivo acidic preconditioning (AP) on CXCR4 expression and on the regenerative potential of mouse bone marrow (BM) ckit⁺ cells.

Methods and results

Acidic preconditioning was achieved by exposing BM ckit⁺ cells to hypercarbic acidosis (pH 7.0) for 24 h; control cells were kept at pH 7.4. Acidic preconditioning enhanced CXCR4 and stromal cell-derived factor 1 (SDF-1) mRNA levels, as well as CXCR4 phosphorylation. Acidic preconditioning ability to modulate CXCR4 expression depended on cytosolic calcium [Ca²⁺]_i mobilization and on nitric oxide (NO), as determined by [Ca²⁺]_i buffering with BAPTA, and by treatment with the NO donor (DETA/NO) and the NO synthase inhibitor (L-NAME). Further, AP increased SDF-1-driven chemotaxis, transendothelial migration, and differentiation toward the endothelial lineage in vitro. In a mouse model of hindlimb ischaemia, control and AP ckit⁺ cells were transplanted into the ischaemic muscle; AP cells accelerated blood flow recovery, increased capillary, and arteriole number as well as the number of regenerating muscle fibres vs. control. These effects were abolished by treating AP cells with L-NAME.

Conclusion

Acidic preconditioning represents a novel strategy to enhance BM ckit⁺ cell therapeutic potential via NO-dependent increase in CXCR4 expression.

Histone deacetylase inhibition enhances self renewal and cardioprotection by human cord blood-derived CD34 cells

Background

Use of peripheral blood- or bone marrow-derived progenitors for ischemic heart repair is a feasible option to induce neo-vascularization in ischemic tissues. These cells, named Endothelial Progenitors Cells (EPCs), have been extensively characterized phenotypically and functionally. The clinical efficacy of cardiac repair by EPCs cells remains, however, limited, due to cell autonomous defects as a consequence of risk factors. The devise of “enhancement” strategies has been therefore sought to improve repair ability of these cells and increase the clinical benefit.

Principal Findings

Pharmacologic inhibition of histone deacetylases (HDACs) is known to enhance hematopoietic stem cells engraftment by improvement of self renewal and inhibition of differentiation in the presence of mitogenic stimuli in vitro. In the present study cord blood-derived CD34⁺ were pre-conditioned with the HDAC inhibitor Valproic Acid. This treatment affected stem cell growth and gene expression, and improved ischemic myocardium protection in an immunodeficient mouse model of myocardial infarction.

Conclusions

Our results show that HDAC blockade leads to phenotype changes in CD34⁺ cells with enhanced self renewal and cardioprotection.

Smad-interacting protein-1 and microRNA 200 family define a nitric oxide-dependent molecular circuitry involved in embryonic stem cell mesendoderm differentiation

OBJECTIVE

Smad-interacting protein-1 (Sip1/ZEB2) is a transcriptional repressor of the telomerase reverse transcriptase catalytic subunit (Tert) and has recently been identified as a key regulator of embryonic cell fate with a phenotypic effect similar, in our opinion, to that reported for nitric oxide (NO). Remarkably, SIP1/ZEB2 is a known target of the microRNA 200 (miR-200) family. In this light, we postulated that Sip1/ZEB2 and the miR-200 family could play a role during the NO-dependent differentiation of mES.

METHODS AND RESULTS

The results of the present study show that Sip1/ZEB2 expression is downregulated during the NO-dependent expression of mesendoderm and early cardiovascular precursor markers, including Flk1 and CXCR4 in mES. Coincidently, members of the miR-200 family, namely miR-429, -200a, -200b, and -200c, were transcriptionally induced in parallel to mouse Tert. This regulation occurred at the level of chromatin. Remarkably, miR-429/miR-200a overexpression or Sip1/ZEB2 knockdown by short hairpin RNA interference elicited a gene expression pattern similar to that of NO regardless of the presence of leukemia inhibitory factor.

CONCLUSIONS

These results are the first demonstrating that the miR-200 family and Sip1/ZEB2 transcription factor are regulated by NO, indicating an unprecedented molecular circuitry important for telomerase regulation and early differentiation of mES.