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

Administration of stem cells against cardiovascular diseases with a focus on molecular mechanisms: Current knowledge and prospects

Cardiovascular diseases (CVDs) are a serious global concern for public and human health. Despite the emergence of significant therapeutic advances, it is still the leading cause of death and disability worldwide. As a result, extensive efforts are underway to develop practical therapeutic approaches. Stem cell-based therapies could be considered a promising strategy for the treatment of CVDs. The efficacy of stem cell-based therapeutic approaches is demonstrated through recent laboratory and clinical studies due to their inherent regenerative properties, proliferative nature, and their capacity to differentiate into different cells such as cardiomyocytes. These properties could improve cardiovascular functioning leading to heart regeneration. The two most common types of stem cells with the potential to cure heart diseases are induced pluripotent stem cells (iPSCs) and mesenchymal stem cells (MSCs). Several studies have demonstrated the use, efficacy, and safety of MSC and iPSCs-based therapies for the treatment of CVDs. In this study, we explain the application of stem cells, especially iPSCs and MSCs, in the treatment of CVDs with a focus on cellular and molecular mechanisms and then discuss the advantages, disadvantages, and perspectives of using this technology in the treatment of these diseases.

Unraveling and Targeting Myocardial Regeneration Deficit in Diabetes

Cardiomyopathy is a common complication in diabetic patients. Ventricular dysfunction without coronary atherosclerosis and hypertension is driven by hyperglycemia, hyperinsulinemia and impaired insulin signaling. Cardiomyocyte death, hypertrophy, fibrosis, and cell signaling defects underlie cardiomyopathy. Notably, detrimental effects of the diabetic milieu are not limited to cardiomyocytes and vascular cells. The diabetic heart acquires a senescent phenotype and also suffers from altered cellular homeostasis and the insufficient replacement of dying cells. Chronic inflammation, oxidative stress, and metabolic dysregulation damage the population of endogenous cardiac stem cells, which contribute to myocardial cell turnover and repair after injury. Therefore, deficient myocardial repair and the progressive senescence and dysfunction of stem cells in the diabetic heart can represent potential therapeutic targets. While our knowledge of the effects of diabetes on stem cells is growing, several strategies to preserve, activate or restore cardiac stem cell compartments await to be tested in diabetic cardiomyopathy.

In vitro differentiation of W8B2+ human cardiac stem cells: gene expression of ionic channels and spontaneous calcium activity

Background

Human cardiac stem cells expressing the W8B2 marker (W8B2⁺ CSCs) were recently identified and proposed as a new model of multipotent CSCs capable of differentiating into smooth muscle cells, endothelial cells and immature myocytes. Nevertheless, no characterization of ion channel or calcium activity during the differentiation of these stem cells has been reported.

Methods

The objectives of this study were thus to analyze (using the TaqMan Low-Density Array technique) the gene profile of W8B2⁺ CSCs pertaining to the regulation of ion channels, transporters and other players involved in the calcium homeostasis of these cells. We also analyzed spontaneous calcium activity (via the GCaMP calcium probe) during the in vitro differentiation of W8B2⁺ CSCs into cardiac myocytes.

Results

Our results show an entirely different electrophysiological genomic profile between W8B2⁺ CSCs before and after differentiation. Some specific nodal genes, such as Tbx3, HCN, ICaT, L, KV, and NCX, are overexpressed after this differentiation. In addition, we reveal spontaneous calcium activity or a calcium clock whose kinetics change during the differentiation process. A pharmacological study carried out on differentiated W8B2⁺ CSCs showed that the NCX exchanger and IP3 stores play a fundamental role in the generation of these calcium oscillations.

Conclusions

Taken together, the present results provide important information on ion channel expression and intrinsic calcium dynamics during the differentiation process of stem cells expressing the W8B2 marker.

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.

Retinoic acid and microRNA

Retinoic acid (RA), the biologically active metabolite of vitamin A, regulates a vast spectrum of biological processes, such as cell differentiation, proliferation, apoptosis, and morphogenesis. microRNAs (miRNAs) play a crucial role in regulating gene expression by binding to messenger RNA (mRNA) which leads to mRNA degradation and/or translational repression. Like RA, miRNAs regulate multiple biological processes, including proliferation, differentiation, apoptosis, neurogenesis, tumorigenesis, and immunity. In fact, RA regulates the expression of many miRNAs to exert its biological functions. miRNA and RA regulatory networks have been studied in recent years. In this manuscript, we summarize literature that highlights the impact of miRNAs in RA-regulated molecular networks included in the PubMed.

Epigenetic regulation of intercellular communication in the heart

The myocardium is a highly structured tissue consisting of different cell types including cardiomyocytes, endothelial cells, fibroblasts, smooth muscle cells, inflammatory cells, and stem cells. Microvascular endothelial cells are the most abundant cell type in the myocardium and play crucial roles during cardiac development, in normal adult myocardium, and during myocardial diseases such as heart failure. In the last decade, epigenetic changes have been described regulating cellular function in almost every cell type in the organism. Here, we review recent evidence on different epigenetic changes that regulate intercellular communication in normal myocardium and during myocardial diseases, including cardiac remodeling. Epigenetic changes influence many intercellular communication signaling systems, including the nitric oxide, angiotensin, and endothelin signaling systems. In this review, we go beyond discussing classic endothelial function (for instance nitric oxide secretion) and will discuss epigenetic regulation of intercellular communication.

Epigenetics and precision medicine in cardiovascular patients: from basic concepts to the clinical arena

Cardiovascular diseases (CVDs) remain the leading cause of mortality worldwide and also inflict major burdens on morbidity, quality of life, and societal costs. Considering that CVD preventive medications improve vascular outcomes in less than half of patients (often relative risk reductions range from 12% to 20% compared with placebo), precision medicine offers an attractive approach to refine the targeting of CVD medications to responsive individuals in a population and thus allocate resources more wisely and effectively. New tools furnished by advances in basic science and translational medicine could help achieve this goal. This approach could reach beyond the practitioners 'eyeball' assessment or venerable markers derived from the physical examination and standard laboratory evaluation. Advances in genetics have identified novel pathways and targets that operate in numerous diseases, paving the way for 'precision medicine'. Yet the inherited genome determines only part of an individual's risk profile. Indeed, standard genomic approaches do not take into account the world of regulation of gene expression by modifications of the 'epi'genome. Epigenetic modifications defined as 'heritable changes to the genome that do not involve changes in DNA sequence' have emerged as a new layer of biological regulation in CVD and could advance individualized risk assessment as well as devising and deploying tailored therapies. This review, therefore, aims to acquaint the cardiovascular community with the rapidly advancing and evolving field of epigenetics and its implications in cardiovascular precision medicine.

Biological properties of cardiac mesenchymal stem cells in rats with diabetic cardiomyopathy

Cardiomyopathy is a major outcome in patients with diabetes mellitus (DM) and contributes to the high morbidity/mortality observed in this disease.

AIMS

To evaluate several biological properties of cardiac mesenchymal stem cells (cMSCs) in a rat model of streptozotocin-induced DM with concomitant diabetic cardiomyopathy.

MAIN METHODS

After 10weeks of DM induction, diabetic and control rats were assessed using ECG and ventricular hemodynamics monitoring. Then, the hearts were excised and processed for histology and for extracting non-cardiomyocytic cells. A pool of these cells was plated for a colony forming units-fibroblasts (CFU-F) assay in order to estimate the number of cMSCs. The remaining cells were expanded to assess their proliferation rate as well as their osteogenic and adipogenic differentiation ability.

KEY FINDINGS

DM rats presented intense hyperglycemia and changes in ECG, LV hemodynamic, cardiac mass index and fibrosis, indicating presence of DCM. The CFU-F assay revealed a higher number of cardiac CFU-Fs in DM rats (10.4±1.1CFU-F/10⁵ total cells versus 7.6±0.7CFU-F/10⁵ total cells in control rats, p<0.05), which was associated with a significantly higher proliferative rate of cMSCs in DM rats. In contrast, cMSCs from DM rats presented a lower capacity to differentiate into both osteogenic (20.8±4.2% versus 10.1±1.0% in control rats, p<0.05) and adipogenic lineages (4.6±1.0% versus 1.3±0.5% in control rats, p<0.05).

SIGNIFICANCE

The findings suggest, for the first time, that in chronic DM rats with overt DCM, cMSCs increase in number and exhibit changes in several functional properties, which could be implicated in the pathogenesis of diabetic cardiomyopathy.

Concise Review: Mesenchymal Stem Cells in Cardiovascular Regeneration: Emerging Research Directions and Clinical Applications

Experimental and early clinical data suggest that, due to several unique properties, mesenchymal stem cells (MSCs) may be more effective than other cell types for diseases that are difficult to treat or untreatable. Owing to their ease of isolation and culture as well as their secretory and immunomodulatory abilities, MSCs are the most promising option in the field of cell‐based therapies. Although MSCs from various sources share several common characteristics, they also exhibit several important differences. These variations may reflect, in part, specific regional properties of the niches from which the cells originate. Moreover, morphological and functional features of MSCs are susceptible to variations across isolation protocols and cell culture conditions. These observations suggest that careful preparation of manufacturing protocols will be necessary for the most efficient use of MSCs in future clinical trials. A typical human myocardial infarct involves the loss of approximately 1 billion cardiomyocytes and 2–3 billion other (mostly endothelial) myocardial cells, leading (despite maximized medical therapy) to a significant negative impact on the length and quality of life. Despite more than a decade of intensive research, search for the “best” (safe and maximally effective) cell type to drive myocardial regeneration continues. In this review, we summarize information about the most important features of MSCs and recent discoveries in the field of MSCs research, and describe current data from preclinical and early clinical studies on the use of MSCs in cardiovascular regeneration. Stem Cells Translational Medicine2017;6:1859–1867

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.

Epigenetics: The third pillar of nitric oxide signaling

Nitric oxide (NO), the endogenously produced free radical signaling molecule, is generally thought to function via its interactions with heme-containing proteins, such as soluble guanylyl cyclase (sGC), or by the formation of protein adducts containing nitrogen oxide functional groups (such as S-nitrosothiols, 3-nitrotyrosine, and dinitrosyliron complexes). These two types of interactions result in a multitude of down-stream effects that regulate numerous functions in physiology and disease. Of the numerous purported NO signaling mechanisms, epigenetic regulation has gained considerable interest in recent years. There is now abundant experimental evidence to establish NO as an endogenous epigenetic regulator of gene expression and cell phenotype. Nitric oxide has been shown to influence key aspects of epigenetic regulation that include histone posttranslational modifications, DNA methylation, and microRNA levels. Studies across disease states have observed NO-mediated regulation of epigenetic protein expression and enzymatic activity resulting in remodeling of the epigenetic landscape to ultimately influence gene expression. In addition to the well-established pathways of NO signaling, epigenetic mechanisms may provide much-needed explanations for poorly understood context-specific effects of NO. These findings provide more insight into the molecular mechanisms of NO signaling and increase our ability to dissect its functional role(s) in specific micro-environments in health and disease. This review will summarize the current state of NO signaling via epigenetic mechanisms (the "third pillar" of NO signaling).

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.

Nitric oxide, the new architect of epigenetic landscapes

Nitric oxide (NO) is an endogenously produced signaling molecule with multiple regulatory functions in physiology and disease. The most studied molecular mechanisms underlying the biological functions of NO include its reaction with heme proteins and regulation of protein activity via modification of thiol residues. A significant number of transcriptional responses and phenotypes observed in NO microenvironments, however, still lack mechanistic understanding. Recent studies shed new light on NO signaling by revealing its influence on epigenetic changes within the cell. Epigenetic alterations are important determinants of transcriptional responses and cell phenotypes, which can relay heritable information during cell division. As transcription across the genome is highly sensitive to these upstream epigenetic changes, this mode of NO signaling provides an alternate explanation for NO-mediated gene expression changes and phenotypes. This review will provide an overview of the interplay between NO and epigenetics as well as emphasize the unprecedented importance of these pathways to explain phenotypic effects associated with biological NO synthesis.

Transplantation of Epigenetically Modified Adult Cardiac c-Kit+ Cells Retards Remodeling and Improves Cardiac Function in Ischemic Heart Failure Model

Cardiac c-Kit+ cells have a modest cardiogenic potential that could limit their efficacy in heart disease treatment. The present study was designed to augment the cardiogenic potential of cardiac c-Kit+ cells through class I histone deacetylase (HDAC) inhibition and evaluate their therapeutic potency in the chronic heart failure (CHF) animal model. Myocardial infarction (MI) was created by coronary artery occlusion in rats. c-Kit+ cells were treated with mocetinostat (MOCE), a specific class I HDAC inhibitor. At 3 weeks after MI, CHF animals were retrogradely infused with untreated (control) or MOCE-treated c-Kit+ cells (MOCE/c-Kit+ cells) and evaluated at 3 weeks after cell infusion. We found that class I HDAC inhibition in c-Kit+ cells elevated the level of acetylated histone H3 (AcH3) and increased AcH3 levels in the promoter regions of pluripotent and cardiac-specific genes. Epigenetic changes were accompanied by increased expression of cardiac-specific markers. Transplantation of CHF rats with either control or MOCE/c-Kit+ cells resulted in an improvement in cardiac function, retardation of CHF remodeling made evident by increased vascularization and scar size, and cardiomyocyte hypertrophy reduction. Compared with CHF infused with control cells, infusion of MOCE/c-Kit+ cells resulted in a further reduction in left ventricle end-diastolic pressure and total collagen and an increase in interleukin-6 expression. The low engraftment of infused cells suggests that paracrine effects might account for the beneficial effects of c-Kit+ cells in CHF. In conclusion, selective inhibition of class I HDACs induced expression of cardiac markers in c-Kit+ cells and partially augmented the efficacy of these cells for CHF repair.

SIGNIFICANCE

The study has shown that selective class 1 histone deacetylase inhibition is sufficient to redirect c-Kit+ cells toward a cardiac fate. Epigenetically modified c-Kit+ cells improved contractile function and retarded remodeling of the congestive heart failure heart. This study provides new insights into the efficacy of cardiac c-Kit+ cells in the ischemic heart failure model.

Use of mesenchymal stem cells for therapy of cardiac disease

Despite substantial clinical advances over the past 65 years, cardiovascular disease remains the leading cause of death in America. The past 15 years has witnessed major basic and translational interest in the use of stem and precursor cells as a therapeutic agent for chronically injured organs. Among the cell types under investigation, adult mesenchymal stem cells are widely studied, and in early stage, clinical studies show promise for repair and regeneration of cardiac tissues. The ability of mesenchymal stem cells to differentiate into mesoderm- and nonmesoderm-derived tissues, their immunomodulatory effects, their availability, and their key role in maintaining and replenishing endogenous stem cell niches have rendered them one of the most heavily investigated and clinically tested type of stem cell. Accumulating data from preclinical and early phase clinical trials document their safety when delivered as either autologous or allogeneic forms in a range of cardiovascular diseases, but also importantly define parameters of clinical efficacy that justify further investigation in larger clinical trials. Here, we review the biology of mesenchymal stem cells, their interaction with endogenous molecular and cellular pathways, and their modulation of immune responses. Additionally, we discuss factors that enhance their proliferative and regenerative ability and factors that may hinder their effectiveness in the clinical setting.

Signaling Pathways and Gene Regulatory Networks in Cardiomyocyte Differentiation

Strategies for harnessing stem cells as a source to treat cell loss in heart disease are the subject of intense research. Human pluripotent stem cells (hPSCs) can be expanded extensively in vitro and therefore can potentially provide sufficient quantities of patient-specific differentiated cardiomyocytes. Although multiple stimuli direct heart development, the differentiation process is driven in large part by signaling activity. The engineering of hPSCs to heart cell progeny has extensively relied on establishing proper combinations of soluble signals, which target genetic programs thereby inducing cardiomyocyte specification. Pertinent differentiation strategies have relied as a template on the development of embryonic heart in multiple model organisms. Here, information on the regulation of cardiomyocyte development from in vivo genetic and embryological studies is critically reviewed. A fresh interpretation is provided of in vivo and in vitro data on signaling pathways and gene regulatory networks (GRNs) underlying cardiopoiesis. The state-of-the-art understanding of signaling pathways and GRNs presented here can inform the design and optimization of methods for the engineering of tissues for heart therapies.

Multipotent stem cells of the heart-do they have therapeutic promise?

The last decade has brought a comprehensive change in our view of cardiac remodeling processes under both physiological and pathological conditions, and cardiac stem cells have become important new players in the general mainframe of cardiac homeostasis. Different types of cardiac stem cells show different capacities for differentiation into the three major cardiac lineages: myocytes, endothelial cells and smooth muscle cells. Physiologically, cardiac stem cells contribute to cardiac homeostasis through continual cellular turnover. Pathologically, these cells exhibit a high level of proliferative activity in an apparent attempt to repair acute cardiac injury, indicating that these cells possess (albeit limited) regenerative potential. In addition to cardiac stem cells, mesenchymal stem cells represent another multipotent cell population in the heart; these cells are located in regions near pericytes and exhibit regenerative, angiogenic, antiapoptotic, and immunosuppressive properties. The discovery of these resident cardiac stem cells was followed by a number of experimental studies in animal models of cardiomyopathies, in which cardiac stem cells were tested as a therapeutic option to overcome the limited transdifferentiating potential of hematopoietic or mesenchymal stem cells derived from bone marrow. The promising results of these studies prompted clinical studies of the role of these cells, which have demonstrated the safety and practicability of cellular therapies for the treatment of heart disease. However, questions remain regarding this new therapeutic approach. Thus, the aim of the present review was to discuss the multitude of different cardiac stem cells that have been identified, their possible functional roles in the cardiac regenerative process, and their potential therapeutic uses in treating cardiac diseases.

Syngeneic cardiac and bone marrow stromal cells display tissue-specific microRNA signatures and microRNA subsets restricted to diverse differentiation processes

MicroRNAs are key modulators at molecular level in different biological processes, including determination of cell fate and differentiation. Herein, microRNA expression profiling experiments were performed on syngeneic cardiac (CStC) and bone marrow (BMStC) mesenchymal stromal cells cultured in standard growth medium and then in vitro exposed to adipogenic, osteogenic, cardiomyogenic and endothelial differentiation media. Analysis identified a tissue-specific microRNA signature composed of 16 microRNAs that univocally discriminated cell type of origin and that were completely unaffected by in vitro differentiation media: 4 microRNAs were over-expressed in cardiac stromal cells, and 12 were overexpressed or present only in bone marrow stromal cells. Further, results revealed microRNA subsets specifically modulated by each differentiation medium, irrespective of the cell type of origin, and a subset of 7 microRNAs that were down-regulated by all media with respect to growth medium. Finally, we identified 16 microRNAs that were differentially modulated by the media when comparing the two tissues of origin. The existence of a tissue-specific microRNA signature surviving to any differentiation stimuli, strongly support the role if microRNAs determining cell identity related to tissue origin. Moreover, we identified microRNA subsets modulated by different culture conditions in a tissue-specific manner, pointing out their importance during differentiation processes.

microRNAs and Cardiac Cell Fate

The role of small, non-coding microRNAs (miRNAs) has recently emerged as fundamental in the regulation of the physiology of the cardiovascular system. Several specific miRNAs were found to be expressed in embryonic, postnatal, and adult cardiac tissues. In the present review, we will provide an overview about their role in controlling the different pathways regulating cell identity and fate determination. In particular, we will focus on the involvement of miRNAs in pluripotency determination and reprogramming, and specifically on cardiac lineage commitment and cell direct transdifferentiation into cardiomyocytes. The identification of cardiac-specific miRNAs and their targets provide new promising insights into the mechanisms that regulate cardiac development, function and dysfunction. Furthermore, due to their contribution in reprogramming, they could offer new opportunities for developing safe and efficient cell-based therapies for cardiovascular disorders.

The histone acetylase activator pentadecylidenemalonate 1b rescues proliferation and differentiation in the human cardiac mesenchymal cells of type 2 diabetic patients

This study investigates the diabetes-associated alterations present in cardiac mesenchymal cells (CMSC) obtained from normoglycemic (ND-CMSC) and type 2 diabetic patients (D-CMSC), identifying the histone acetylase (HAT) activator pentadecylidenemalonate 1b (SPV106) as a potential pharmacological intervention to restore cellular function. D-CMSC were characterized by a reduced proliferation rate, diminished phosphorylation at histone H3 serine 10 (H3S10P), decreased differentiation potential, and premature cellular senescence. A global histone code profiling of D-CMSC revealed that acetylation on histone H3 lysine 9 (H3K9Ac) and lysine 14 (H3K14Ac) was decreased, whereas the trimethylation of H3K9Ac and lysine 27 significantly increased. These observations were paralleled by a downregulation of the GCN5-related N-acetyltransferases (GNAT) p300/CBP-associated factor and its isoform 5-α general control of amino acid synthesis (GCN5a), determining a relative decrease in total HAT activity. DNA CpG island hypermethylation was detected at promoters of genes involved in cell growth control and genomic stability. Remarkably, treatment with the GNAT proactivator SPV106 restored normal levels of H3K9Ac and H3K14Ac, reduced DNA CpG hypermethylation, and recovered D-CMSC proliferation and differentiation. These results suggest that epigenetic interventions may reverse alterations in human CMSC obtained from diabetic patients.

Transcriptional profiling of the human fibrillin/LTBP gene family, key regulators of mesenchymal cell functions

The fibrillins and latent transforming growth factor binding proteins (LTBPs) form a superfamily of extracellular matrix (ECM) proteins characterized by the presence of a unique domain, the 8-cysteine transforming growth factor beta (TGFβ) binding domain. These proteins are involved in the structure of the extracellular matrix and controlling the bioavailability of TGFβ family members. Genes encoding these proteins show differential expression in mesenchymal cell types which synthesize the extracellular matrix. We have investigated the promoter regions of the seven gene family members using the FANTOM5 CAGE database for human. While the protein and nucleotide sequences show considerable sequence similarity, the promoter regions were quite diverse. Most genes had a single predominant transcription start site region but LTBP1 and LTBP4 had two regions initiating different transcripts. Most of the family members were expressed in a range of mesenchymal and other cell types, often associated with use of alternative promoters or transcription start sites within a promoter in different cell types. FBN3 was the lowest expressed gene, and was found only in embryonic and fetal tissues. The different promoters for one gene were more similar to each other in expression than to promoters of the other family members. Notably expression of all 22 LTBP2 promoters was tightly correlated and quite distinct from all other family members. We located candidate enhancer regions likely to be involved in expression of the genes. Each gene was associated with a unique subset of transcription factors across multiple promoters although several motifs including MAZ, SP1, GTF2I and KLF4 showed overrepresentation across the gene family. FBN1 and FBN2, which had similar expression patterns, were regulated by different transcription factors. This study highlights the role of alternative transcription start sites in regulating the tissue specificity of closely related genes and suggests that this important class of extracellular matrix proteins is subject to subtle regulatory variations that explain the differential roles of members of this gene family.

The yin and yang of nitric oxide in cancer progression

Nitric oxide (NO) is a short-lived, pleiotropic molecule that affects numerous critical functions in the body. Presently, there are markedly conflicting findings in the literature regarding NO and its role in carcinogenesis and tumor progression. NO has been shown to have dichotomous effects on cellular proliferation, apoptosis, migration, invasion, angiogenesis and many other important processes in cancer biology. It has been shown to be both pro- and antitumorigenic, depending on the concentration and the tumor microenvironment in question. NO is generated by three isoforms of NO synthase (NOS) that are widely expressed and sometimes upregulated in human tumors. Due to its vast array of physiological functions, it presents a huge challenge to researchers to discover its true potential in cancer biology and consequently, its use in anticancer therapies. In this study, we review the current knowledge in this area, with an emphasis placed on NO modulation as an anticancer therapy, focusing on NO-donating drugs and NOS inhibitors.