Leukemia inhibitory factor induces endothelial differentiation in cardiac stem cells

γH2AX in mouse embryonic stem cells: Distribution during differentiation and following γ-irradiation

Phosphorylated histone H2AX (γH2AX) represents a sensitive molecular marker of DNA double-strand breaks (DSBs) and is implicated in stem cell biology. We established a model of mouse embryonic stem cell (mESC) differentiation and examined the dynamics of γH2AX foci during the process. Our results revealed high numbers of γH2AX foci in undifferentiated mESCs, decreasing as the cells differentiated towards the endothelial cell lineage. Notably, we observed two distinct patterns of γH2AX foci: the typical discrete γH2AX foci, which colocalize with the transcriptionally permissive chromatin mark H3K4me3, and the less well-characterized clustered γH2AX regions, which were only observed in intermediate progenitor cells. Next, we explored responses of mESCs to γ-radiation (137Cs). Following exposure to γ-radiation, mESCs showed a reduction in cell viability and increased γH2AX foci, indicative of radiosensitivity. Despite irradiation, surviving mESCs retained their differentiation potential. To further exemplify our findings, we investigated neural stem progenitor cells (NSPCs). Similar to mESCs, NSPCs displayed clustered γH2AX foci associated with progenitor cells and discrete γH2AX foci indicative of embryonic stem cells or differentiated cells. In conclusion, our findings demonstrate that γH2AX serves as a versatile marker of DSBs and may have a role as a biomarker in stem cell differentiation. The distinct patterns of γH2AX foci in differentiating mESCs and NSPCs provide valuable insights into DNA repair dynamics during differentiation, shedding light on the intricate balance between genomic integrity and cellular plasticity in stem cells. Finally, the clustered γH2AX foci observed in intermediate progenitor cells is an intriguing feature, requiring further exploration.

Single-Cell RNA-Seq Identifies Dynamic Cardiac Transition Program from Adipose Derived Cells Induced by Leukemia Inhibitory Factor

Adipose-derived cells (ADCs) from white adipose tissue (WAT) are promising stem cell candidates because of their large regenerative reserves and the potential for cardiac regeneration. However, given the heterogeneity of ADC and its unsolved mechanisms of cardiac acquisition, ADC-cardiac transition efficiency remains low. In this study, we explored the heterogeneity of ADCs and the cellular kinetics of 39,432 single-cell transcriptomes along the leukemia inhibitory factor (LIF) induced ADC-cardiac transition. We identified distinct ADC subpopulations that reacted differentially to LIF when entering the cardiomyogenic program, further demonstrating that ADC-myogenesis is time-dependent and initiates from transient changes in nuclear factor erythroid 2-related factor 2 (Nrf2) signaling. At later stages, pseudotime analysis of ADCs navigated a trajectory with two branches corresponding to activated myofibroblast or cardiomyocyte-like cells. Our findings offer a high-resolution dissection of ADC heterogeneity and cell fate during ADC-cardiac transition, thus providing new insights into potential cardiac stem cells.

Leukemia Inhibitory Factor: An Important Cytokine in Pathologies and Cancer

Leukemia Inhibitory Factor (LIF) is a member of the IL-6 cytokine family and is expressed in almost every tissue type within the body. Although LIF was named for its ability to induce differentiation of myeloid leukemia cells, studies of LIF in additional diseases and solid tumor types have shown that it has the potential to contribute to many other pathologies. Exploring the roles of LIF in normal physiology and non-cancer pathologies can give important insights into how it may be dysregulated within cancers, and the possible effects of this dysregulation. Within various cancer types, LIF expression has been linked to hallmarks of cancer, such as proliferation, metastasis, and chemoresistance, as well as overall patient survival. The mechanisms behind these effects of LIF are not well understood and can differ between different tissue types. In fact, research has shown that while LIF may promote malignancy progression in some solid tumors, it can have anti-neoplastic effects in others. This review will summarize current knowledge of how LIF expression impacts cellular function and dysfunction to help reveal new adjuvant treatment options for cancer patients, while also revealing potential adverse effects of treatments targeting LIF signaling.

Leukemia Inhibitory Factor (LIF) Overexpression Increases the Angiogenic Potential of Bone Marrow Mesenchymal Stem/Stromal Cells

Mesenchymal stem/stromal cells (MSCs) have the ability to secrete bioactive molecules, exerting multiple biological effects, such as tissue regeneration, reduction of inflammation, and neovascularization. The therapeutic potential of MSCs can be increased by genetic modification to overexpress cytokines and growth factors. Here we produced mouse MSCs overexpressing human leukemia inhibitory factor (LIF) to assess their proangiogenic potential in vitro and in vivo. Mouse bone marrow-derived MSCs were transduced by using a second-generation lentiviral system to express human LIF. Leukemia inhibitory factor expression was confirmed by RT-qPCR and by ELISA, allowing the quantification of the transcript and secreted protein, respectively. Flow cytometry analysis and trilineage differentiation assay showed that the MSC_LIF cell line maintained the immunophenotype and a multipotency characteristic of MSCs. The immunosuppressive activity of MSC_LIF was confirmed using a lymphoproliferation assay. Moreover, gene expression analysis demonstrated upregulation of genes coding for strategic factors in the neovascularization process, such as angiogenin, IL-8, MCP-1, and VEGF, and for the perivascular cell markers αSMA, Col4a1, SM22, and NG2. To evaluate the pro-angiogenic potential of MSC_LIF, we first tested its effects on endothelial cells obtained from umbilical vein in a scratch wound healing assay. Conditioned medium (CM) from MSC_LIF promoted a significant increase in cell migration compared to CM from control MSC. Additionally, in vitro tube formation of endothelial cells was increased by the presence of MSC_LIF, as shown in microvessel sprouting in aortic ring cultures. Finally, an in vivo Matrigel plug assay was performed, showing that MSC_LIF were more potent in promoting in vivo angiogenesis and tissue vascularization than control MSCs. In conclusion, LIF overexpression is a promising strategy to increase the proangiogenic potential of MSCs and sets precedents for future investigations of their potential applications for the treatment of ischemic diseases and tissue repair.

Three in a Box: Understanding Cardiomyocyte, Fibroblast, and Innate Immune Cell Interactions to Orchestrate Cardiac Repair Processes

Following an insult by both intrinsic and extrinsic pathways, complex cellular, and molecular interactions determine a successful recovery or inadequate repair of damaged tissue. The efficiency of this process is particularly important in the heart, an organ characterized by very limited regenerative and repair capacity in higher adult vertebrates. Cardiac insult is characteristically associated with fibrosis and heart failure, as a result of cardiomyocyte death, myocardial degeneration, and adverse remodeling. Recent evidence implies that resident non-cardiomyocytes, fibroblasts but also macrophages -pillars of the innate immunity- form part of the inflammatory response and decisively affect the repair process following a cardiac insult. Multiple studies in model organisms (mouse, zebrafish) of various developmental stages (adult and neonatal) combined with genetically engineered cell plasticity and differentiation intervention protocols -mainly targeting cardiac fibroblasts or progenitor cells-reveal particular roles of resident and recruited innate immune cells and their secretome in the coordination of cardiac repair. The interplay of innate immune cells with cardiac fibroblasts and cardiomyocytes is emerging as a crucial platform to help our understanding and, importantly, to allow the development of effective interventions sufficient to minimize cardiac damage and dysfunction after injury.

The Biological Mechanisms of Action of Cardiac Progenitor Cell Therapy

PURPOSE OF REVIEW

Cell therapy for cardiovascular diseases is regarded as a rapidly growing field within regenerative medicine. Different cellular populations enriched for cardiac progenitor cells (CPCs), or derivate a-cellular products, are currently under preclinical and clinical evaluation. Here, we have reviewed the described mechanisms whereby resident post-natal CPCs, isolated in different ways, act as a therapeutic product on the damaged myocardium.

RECENT FINDINGS

Several biological mechanisms of action have been described which can explain the multiple therapeutic effects of CPC treatment observed on cardiac function and remodelling. These mechanisms span from direct cardiovascular differentiation, through induction of resident progenitor proliferation, to paracrine effects on cardiac and non-cardiac cells mediated by exosomes and non-coding RNAs. All the reported mechanisms of action support an integrated view including cardiomyogenesis, cardioprotection, and anti-fibrotic effects. Moreover, future developments of CPC therapy approaches may support cell-free strategies, exploiting effective pleiotropic cell-derived products, such as exosomes.

Implications of Cellular Aging in Cardiac Reprogramming

Aging is characterized by a chronic functional decline of organ systems which leads to tissue dysfunction over time, representing a risk factor for diseases development, including cardiovascular. The aging process occurring in the cardiovascular system involves heart and vessels at molecular and cellular level, with subsequent structural modifications and functional impairment. Several modifications involved in the aging process can be ascribed to cellular senescence, a biological response that limits the proliferation of damaged cells. In physiological conditions, the mechanism of cellular senescence is involved in regulation of tissue homeostasis, remodeling, and repair. However, in some conditions senescence-driven tissue repair may fail, leading to the tissue accumulation of senescent cells which in turn may contribute to tumor promotion, aging, and age-related diseases. Cellular reprogramming processes can reverse several age-associated cell features, such as telomere length, DNA methylation, histone modifications and cell-cycle arrest. As such, induced Pluripotent Stem Cells (iPSCs) can provide models of progeroid and physiologically aged cells to gain insight into the pathogenesis of such conditions, to drive the development of new therapies for premature aging and to further explore the possibility of rejuvenating aged cells. An emerging picture is that the tissue remodeling role of cellular senescence could also be crucial for the outcomes of in vivo reprogramming processes. Experimental evidence has demonstrated that, on one hand, senescence represents a cell-autonomous barrier for a cell candidate to reprogramming, but, on the other hand, it may positively sustain the reprogramming capability of surrounding cells to generate fully proficient tissues. This review fits into this conceptual framework by highlighting the most prominent concepts that characterize aging and reprogramming and discusses how the aging tissue might provide a favorable microenvironment for in vivo cardiac reprogramming.

Human Cytomegalovirus Immediate-Early 1 Protein Rewires Upstream STAT3 to Downstream STAT1 Signaling Switching an IL6-Type to an IFNγ-Like Response

The human cytomegalovirus (hCMV) major immediate-early 1 protein (IE1) is best known for activating transcription to facilitate viral replication. Here we present transcriptome data indicating that IE1 is as significant a repressor as it is an activator of host gene expression. Human cells induced to express IE1 exhibit global repression of IL6- and oncostatin M-responsive STAT3 target genes. This repression is followed by STAT1 phosphorylation and activation of STAT1 target genes normally induced by IFNγ. The observed repression and subsequent activation are both mediated through the same region (amino acids 410 to 445) in the C-terminal domain of IE1, and this region serves as a binding site for STAT3. Depletion of STAT3 phenocopies the STAT1-dependent IFNγ-like response to IE1. In contrast, depletion of the IL6 receptor (IL6ST) or the STAT kinase JAK1 prevents this response. Accordingly, treatment with IL6 leads to prolonged STAT1 instead of STAT3 activation in wild-type IE1 expressing cells, but not in cells expressing a mutant protein (IE1dl410-420) deficient for STAT3 binding. A very similar STAT1-directed response to IL6 is also present in cells infected with a wild-type or revertant hCMV, but not an IE1dl410-420 mutant virus, and this response results in restricted viral replication. We conclude that IE1 is sufficient and necessary to rewire upstream IL6-type to downstream IFNγ-like signaling, two pathways linked to opposing actions, resulting in repressed STAT3- and activated STAT1-responsive genes. These findings relate transcriptional repressor and activator functions of IE1 and suggest unexpected outcomes relevant to viral pathogenesis in response to cytokines or growth factors that signal through the IL6ST-JAK1-STAT3 axis in hCMV-infected cells. Our results also reveal that IE1, a protein considered to be a key activator of the hCMV productive cycle, has an unanticipated role in tempering viral replication.

Our previous work has shown that the human cytomegalovirus (hCMV) major immediate-early 1 protein (IE1) modulates host cell signaling pathways involving proteins of the signal transducer and activator of transcription (STAT) family. IE1 has also long been known to facilitate viral replication by activating transcription. In this report we demonstrate that IE1 is as significant a repressor as it is an activator of host gene expression. Many genes repressed by IE1 are normally induced via STAT3 signaling triggered by interleukin 6 (IL6) or related cytokines, whereas many genes activated by IE1 are normally induced via STAT1 signaling triggered by interferon gamma (IFNγ). Our results suggest that the repression of STAT3- and the activation of STAT1-responsive genes by IE1 are coupled. By targeting STAT3, IE1 rewires upstream STAT3 to downstream STAT1 signaling. Consequently, genes normally induced by IL6 are repressed while genes normally induced by IFNγ become responsive to IL6 in the presence of IE1. We also demonstrate that, by switching an IL6 to an IFNγ-like response, IE1 tempers viral replication. These results suggest an unanticipated dual role for IE1 in either promoting or limiting hCMV propagation and demonstrate how a key viral regulatory protein merges two central cellular signaling pathways to divert cytokine responses relevant to hCMV pathogenesis.

mRNAs and miRNAs in whole blood associated with lung hyperplasia, fibrosis, and bronchiolo-alveolar adenoma and adenocarcinoma after multi-walled carbon nanotube inhalation exposure in mice

Inhalation exposure to multi-walled carbon nanotubes (MWCNT) in mice results in inflammation, fibrosis and the promotion of lung adenocarcinoma; however, the molecular basis behind these pathologies is unknown. This study determined global mRNA and miRNA profiles in whole blood from mice exposed by inhalation to MWCNT that correlated with the presence of lung hyperplasia, fibrosis, and bronchiolo-alveolar adenoma and adenocarcinoma. Six-week-old, male, B6C3F1 mice received a single intraperitoneal injection of either the DNA-damaging agent methylcholanthrene (MCA, 10 µg g(-1) body weight) or vehicle (corn oil). One week after injections, mice were exposed by inhalation to MWCNT (5 mg m(-3), 5 hours per day, 5 days per week) or filtered air (control) for a total of 15 days. At 17 months post-exposure, mice were euthanized and examined for the development of pathological changes in the lung, and whole blood was collected and analyzed using microarray analysis for global mRNA and miRNA expression. Numerous mRNAs and miRNAs in the blood were significantly up- or down-regulated in animals developing pathological changes in the lung after MCA/corn oil administration followed by MWCNT/air inhalation, including fcrl5 and miR-122-5p in the presence of hyperplasia, mthfd2 and miR-206-3p in the presence of fibrosis, fam178a and miR-130a-3p in the presence of bronchiolo-alveolar adenoma, and il7r and miR-210-3p in the presence of bronchiolo-alveolar adenocarcinoma, among others. The changes in miRNA and mRNA expression, and their respective regulatory networks, identified in this study may potentially serve as blood biomarkers for MWCNT-induced lung pathological changes.

Myeloid cell-derived LRG attenuates adverse cardiac remodelling after myocardial infarction

AIMS

Leucine-rich α2-glycoprotein (LRG) is considered as a biomarker of the clinical activities of chronic inflammatory diseases, including heart failure. However, its pathophysiological roles in cardiac remodelling after myocardial infarction (MI) remain to be clarified. In this study, we have addressed functional roles of LRG in cardiac remodelling after MI.

METHODS AND RESULTS

MI was generated by ligating the left coronary artery in mice. Real-time reverse transcription (RT)-PCR and immunoblot analyses revealed that the expressions of LRG transcript and protein were up-regulated in post-infarct myocardium. LRG protein was produced by heart-infiltrating myeloid cells, such as macrophages and neutrophils. To elucidate functional roles of LRG in cardiac remodelling, we generated MI in wild-type (WT) and LRG-deficient (LRG(-/-)) mice and found that LRG gene ablation aggravated myocardial fibrosis with cardiac dysfunction after MI. Immunohistochemical analyses with anti-CD31 antibody revealed that capillary density decreased at border zone in LRG(-/-) mice compared with WT mice. Consistently, the expression of apelin receptor was reduced in LRG(-/-) mice, implying that the impaired angiogenic activity is associated with adverse cardiac remodelling in LRG(-/-) mice. Moreover, LRG gene ablation suppressed the activation of smad1/5/8, a pro-angiogenic signalling pathway. Finally, the transplantation of WT bone marrow cells into LRG(-/-) mice attenuated cardiac fibrosis with functional improvement after MI, accompanied by restoration of capillary density compared with the bone marrow transplantation from LRG(-/-) mice.

CONCLUSION

LRG, produced by heart-infiltrating myeloid cells, suppresses adverse cardiac remodelling after MI as a novel cardioprotective factor. LRG signalling could be a therapeutic target against cardiovascular diseases.

Leukemia inhibitory factor (LIF)

Leukemia inhibitory factor (LIF) is the most pleiotropic member of the interleukin-6 family of cytokines. It utilises a receptor that consists of the LIF receptor β and gp130 and this receptor complex is also used by ciliary neurotrophic growth factor (CNTF), oncostatin M, cardiotrophin1 (CT1) and cardiotrophin-like cytokine (CLC). Despite common signal transduction mechanisms (JAK/STAT, MAPK and PI3K) LIF can have paradoxically opposite effects in different cell types including stimulating or inhibiting each of cell proliferation, differentiation and survival. While LIF can act on a wide range of cell types, LIF knockout mice have revealed that many of these actions are not apparent during ordinary development and that they may be the result of induced LIF expression during tissue damage or injury. Nevertheless LIF does appear to have non-redundant actions in maternal receptivity to blastocyst implantation, placental formation and in the development of the nervous system. LIF has also found practical use in the maintenance of self-renewal and totipotency of embryonic stem cells and induced pluripotent stem cells.

Interleukin-27 induces the endothelial differentiation in Sca-1+ cardiac resident stem cells

Cytokines play important roles in cardiac repair and regeneration. Recently, we demonstrated that interleukin (IL)-6 family cytokines induce the endothelial differentiation of Sca-1+ cardiac resident stem cells through STAT3/Pim-1 signaling pathway. In contrast, the biological functions of IL-12 family cytokines in heart remain to be elucidated, though they show structural homology with IL-6. In the present study, we examined the effects of IL-12 family cytokines on the transdifferentiation of cardiac Sca-1+ cells into cardiac cells. RT-PCR analyses revealed that IL-27 receptor α (IL-27Rα), but not IL-12R or IL-23R, was expressed in cardiac Sca-1+ cells. The transcript expression of IL-27 was elevated in murine hearts in cardiac injury models. Intriguingly, IL-27 stimulation for 14 days induced the endothelial cell (EC) marker genes, such as CD-31 and VE-cadherin. Immunoblot analyses clarified that IL-27 treatment rapidly phosphorylated STAT3. IL-27 upregulated the expression of Pim-1, but the overexpression of dominant negative STAT3 abrogated the induction of Pim-1 by IL-27. Finally, adenoviral transfection of dominant negative Pim-1 inhibited IL-27-induced EC differentiation of cardiac Sca-1+ cells. These findings demonstrated that IL-27 promoted the commitment of cardiac stem cells into the EC lineage, possibly leading to neovascularization as a novel biological function. IL-27 could not only regulate the inflammation but also contribute to the maintenance of the tissue homeostasis through stem cell differentiation at inflammatory sites.

The leukemia inhibitory factor (LIF) and p21 mediate the TGFβ tumor suppressive effects in human cutaneous melanoma

BACKGROUND

Cutaneous melanoma is the most lethal skin cancer and its incidence in developed countries has dramatically increased over the past decades. Localized tumors are easily treated by surgery, but advanced melanomas lack efficient treatment and are associated with very poor outcomes. Thus, understanding the processes underlying melanoma development and progression is critical. The Transforming Growth Factor beta (TGFβ) acts as a potent tumor suppressor in human melanoma, by inhibiting cell growth and preventing cellular migration and invasion.

METHODS

In this study, we aimed at elucidating the molecular mechanisms underlying TGFβ-mediated tumor suppression. Human cutaneous melanoma cell lines, derived from different patients, were used to assess for cell cycle analysis, apoptosis/caspase activity and cell migration. Techniques involved immunoblotting, immunohistochemistry, real time PCR and luciferase reporter assays.

RESULTS

We found the leukemia inhibitory factor (LIF) to be strongly up-regulated by TGFβ in melanoma cells, defining LIF as a novel TGFβ downstream target gene in cutaneous melanoma. Interestingly, we also showed that TGFβ-mediated LIF expression is required for TGFβ-induced cell cycle arrest and caspase-mediated apoptosis, as well as for TGFβ-mediated inhibition of cell migration. Moreover, we found that TGFβ-mediated LIF expression leads to activation of transcription of the cell cycle inhibitor p21 in a STAT3-dependent manner, and further showed that p21 is required for TGFβ/LIF-mediated cell cycle arrest and TGFβ-induced gene activation of several pro-apoptotic genes.

CONCLUSIONS

Together, our results define the LIF/p21 signaling cascade as a novel tumor suppressive-like pathway in melanoma, acting downstream of TGFβ to regulate cell cycle arrest and cell death, further highlight new potential therapeutic strategies for the treatment of cutaneous melanoma.

β-arrestin2/miR-155/GSK3β regulates transition of 5'-azacytizine-induced Sca-1-positive cells to cardiomyocytes

Stem-cell antigen 1–positive (Sca-1+) cardiac stem cells (CSCs), a vital kind of CSCs in humans, promote cardiac repair in vivo and can differentiate to cardiomyocytes with 5′-azacytizine treatment in vitro. However, the underlying molecular mechanisms are unknown. β-arrestin2 is an important scaffold protein and highly expressed in the heart. To explore the function of β-arrestin2 in Sca-1+ CSC differentiation, we used β-arrestin2–knockout mice and overexpression strategies. Real-time PCR revealed that β-arrestin2 promoted 5′-azacytizine-induced Sca-1+ CSC differentiation in vitro. Because the microRNA 155 (miR-155) may regulate β-arrestin2 expression, we detected its role and relationship with β-arrestin2 and glycogen synthase kinase 3 (GSK3β), another probable target of miR-155. Real-time PCR revealed that miR-155, inhibited by β-arrestin2, impaired 5′-azacytizine-induced Sca-1+ CSC differentiation. On luciferase report assay, miR-155 could inhibit the activity of β-arrestin2 and GSK3β, which suggests a loop pathway between miR-155 and β-arrestin2. Furthermore, β-arrestin2-knockout inhibited the activity of GSK3β. Akt, the upstream inhibitor of GSK3β, was inhibited in β-arrestin2-Knockout mice, so the activity of GSK3β was regulated by β-arrestin2 not Akt. We transplanted Sca-1+ CSCs from β-arrestin2-knockout mice to mice with myocardial infarction and found similar protective functions as in wild-type mice but impaired arterial elastance. Furthermore, low level of β-arrestin2 agreed with decreased phosphorylation of AKT and increased phophorylation of GSK3β, similar to in vitro findings. The β-arrestin2/miR-155/GSK3β pathway may be a new mechanism with implications for treatment of heart disease.

JAK-STAT signaling in cardiomyogenesis of cardiac stem cells

Recently various kinds of cardiac stem/progenitor cells have been identified and suggested to be involved in cardiac repair and regeneration in injured myocardium. In this review, we focus on the roles of JAK-STAT signaling in cardiac stem/progenitor cells in cardiomyogenesis. JAK-STAT signaling plays important roles in the differentiation of stem cells into cardiac lineage cells. The activation of JAK-STAT signal elicits the mobilization of mesenchymal stem cells as well, contributing to the maintenance of cardiac function. Thus we propose that JAK-STAT could be a target signaling pathway in cardiac regenerative therapy.

STAT3, a key regulator of cell-to-cell communication in the heart

The signal transducer and activator of transcription 3 (STAT3) is fundamental for physiological homeostasis and stress-induced remodelling of the heart as deregulated STAT3 circuits are sufficient to induce dilated and peripartum cardiomyopathy and adverse remodelling after myocardial infarction. STAT3 activity depends on multiple post-translational modifications (phosphorylation, acetylation, and dimerization). It is regulated by multiple receptor systems, which are coupled to positive and negative feedback loops to ensure physiological and beneficial action. Its intracellular functions are diverse as it acts as a signalling protein, a transcription factor but also participates in mitochondria energy production and protection. STAT3 modulates proliferation, differentiation, survival, oxidative stress, and/or metabolism in cardiomyocytes, fibroblasts, endothelial cells, progenitor cells, and various inflammatory cells. By regulating the secretome of these cardiac cells, STAT3 influences a broad range of intercellular communication systems. It thereby impacts on the communication between cardiomyocytes, the plasticity of the cardiac microenvironment, the vasculature, the extracellular matrix, and the inflammation in response to physiological and pathophysiological stress. Here, we sum up current knowledge on STAT3-mediated intra- and intercellular communication within the heterogeneous cellular network of the myocardium to co-ordinate complex biological processes and discuss STAT3-dependent targets as novel therapeutic concepts to treat various forms of heart disease.

Cardiac stem cells and their roles in myocardial infarction

Myocardial infarction leads to loss of cardiomyocytes, scar formation, ventricular remodeling and eventually deterioration of heart function. Over the past decade, stem cell therapy has emerged as a novel strategy for patients with ischemic heart disease and its beneficial effects have been demonstrated by substantial preclinical and clinical studies. Efficacy of several types of stem cells in the therapy of cardiovascular diseases has already been evaluated. However, repair of injured myocardium through stem cell transplantation is restricted by critical safety issues and ethic concerns. Recently, the discovery of cardiac stem cells (CSCs) that reside in the heart itself brings new prospects for myocardial regeneration and reconstitution of cardiac tissues. CSCs are positive for various stem cell markers and have the potential of self-renewal and multilineage differentiation. They play a pivotal role in the maintenance of heart homeostasis and cardiac repair. Elucidation of their biological characteristics and functions they exert in myocardial infarction are very crucial to further investigations on them. This review will focus on the field of cardiac stem cells and discuss technical and practical issues that may involve in their clinical applications in myocardial infarction.

Local activation of cardiac stem cells for post-myocardial infarction cardiac repair

The prognosis of patients with myocardial infarction (MI) and resultant chronic heart failure remains extremely poor despite continuous advancements in optimal medical therapy and interventional procedures. Animal experiments and clinical trials using adult stem cell therapy following MI have shown a global improvement of myocardial function. The emergence of stem cell transplantation approaches has recently represented promising alternatives to stimulate myocardial regeneration. Regarding their tissue-specific properties, cardiac stem cells (CSCs) residing within the heart have advantages over other stem cell types to be the best cell source for cell transplantation. However, time-consuming and costly procedures to expanse cells prior to cell transplantation and the reliability of cell culture and expansion may both be major obstacles in the clinical application of CSC-based transplantation therapy after MI. The recognition that the adult heart possesses endogenous CSCs that can regenerate cardiomyocytes and vascular cells has raised the unique therapeutic strategy to reconstitute dead myocardium via activating these cells post-MI. Several strategies, such as growth factors, mircoRNAs and drugs, may be implemented to potentiate endogenous CSCs to repair infarcted heart without cell transplantation. Most molecular and cellular mechanism involved in the process of CSC-based endogenous regeneration after MI is far from understanding. This article reviews current knowledge opening up the possibilities of cardiac repair through CSCs activation in situ in the setting of MI.

LIF and the heart: just another brick in the wall?

Multiple studies have shown that the cytokine leukemia inhibitory factor (LIF) is protective of the myocardium in the acute stress of ischemia-reperfusion. All three major intracellular signaling pathways that are activated by LIF in cardiac myocytes have been linked to actions that protect against oxidative stress and cell death, either at the level of the mitochondrion or via nuclear transcription. In addition, LIF has been shown to contribute to post-myocardial infarction cardiac repair and regeneration, by stimulating the homing of bone marrow-derived cardiac progenitors to the injured myocardium, the differentiation of resident cardiac stem cells into endothelial cells, and neovascularization. Whether LIF offers protection to the heart under chronic stress such as hypertension-induced cardiac remodeling and heart failure is not known. However, mice with cardiac myocyte restricted knockout of STAT3, a principal transcription factor activated by LIF, develop heart failure with age, and cardiac STAT3 levels are reported to be decreased in heart failure patients. In addition, endogenously produced LIF has been implicated in the cholinergic transdiffrentiation that may serve to attenuate sympathetic overdrive in heart failure and in the peri-infarct region of the heart after myocardial infarction. Surprisingly, therapeutic strategies to exploit the beneficial actions of LIF on the injured myocardium have received scant attention. Nor is it established whether the purported so-called adverse effects of LIF observed in isolated cardiac myocytes have physiological relevance in vivo. Here we present an overview of the actions of LIF in the heart with the goal of stimulating further research into the translational potential of this pleiotropic cytokine.

Therapeutic administration of IL-11 exhibits the postconditioning effects against ischemia-reperfusion injury via STAT3 in the heart

Activation of cardiac STAT3 by IL-6 cytokine family contributes to cardioprotection. Previously, we demonstrated that IL-11, an IL-6 cytokine family, has the therapeutic potential to prevent adverse cardiac remodeling after myocardial infarction; however, it remains to be elucidated whether IL-11 exhibits postconditioning effects. To address the possibility that IL-11 treatment improves clinical outcome of recanalization therapy against acute myocardial infarction, we examined its postconditioning effects on ischemia/reperfusion (I/R) injury. C57BL/6 mice were exposed to ischemia (30 min) and reperfusion (24 h), and IL-11 was intravenously administered at the start of reperfusion. I/R injury mediated the activation of STAT3, which was enhanced by IL-11 administration. IL-11 treatment reduced I/R injury, analyzed by triphenyl tetrazolium chloride staining [PBS, 46.7 ± 14.4%; IL-11 (20 μg/kg), 28.6 ± 7.5% in the ratio of infarct to risk area]. Moreover, echocardiographic and hemodynamic analyses clarified that IL-11 treatment preserved cardiac function after I/R. Terminal deoxynucleotide transferase-mediated dUTP nick-end labeling staining revealed that IL-11 reduced the frequency of apoptotic cardiomyocytes after I/R. Interestingly, IL-11 reduced superoxide production assessed by in situ dihydroethidium fluorescence analysis, accompanied by the increased expression of metallothionein 1 and 2, reactive oxygen species (ROS) scavengers. Importantly, with the use of cardiac-specific STAT3 conditional knockout (STAT3 CKO) mice, it was revealed that cardiac-specific ablation of STAT3 abrogated IL-11-mediated attenuation of I/R injury. Finally, IL-11 failed to suppress the ROS production after I/R in STAT3 CKO mice. IL-11 administration exhibits the postconditioning effects through cardiac STAT3 activation, suggesting that IL-11 has the clinical therapeutic potential to prevent I/R injury in heart.

The heme oxygenase 1 inducer (CoPP) protects human cardiac stem cells against apoptosis through activation of the extracellular signal-regulated kinase (ERK)/NRF2 signaling pathway and cytokine release

Intracoronary delivery of c-kit-positive human cardiac stem cells (hCSCs) is a promising approach to repair the infarcted heart, but it is severely limited by the poor survival of donor cells. Cobalt protoporphyrin (CoPP), a well known heme oxygenase 1 inducer, has been used to promote endogenous CO generation and protect against ischemia/reperfusion injury. Therefore, we determined whether preconditioning hCSCs with CoPP promotes CSC survival. c-kit-positive, lineage-negative hCSCs were isolated from human heart biopsies. Lactate dehydrogenase release assays demonstrated that preconditioning CSCs with CoPP markedly enhanced cell survival after oxidative stress induced by H(2)O(2), concomitant with up-regulation of heme oxygenase 1, COX-2, and anti-apoptotic proteins (BCL2, BCL2-A1, and MCL-1) and increased phosphorylation of NRF2. Apoptotic cytometric assays showed that pretreatment of CSCs with CoPP enhanced the cells' resistance to apoptosis induced by oxidative stress. Conversely, knocking down HO-1, COX-2, or NRF2 by shRNA gene silencing abrogated the cytoprotective effects of CoPP. Further, preconditioning CSCs with CoPP led to a global increase in release of cytokines, such as EGF, FGFs, colony-stimulating factors, and chemokine ligand. Conditioned medium from cells pretreated with CoPP conferred naive CSCs remarkable resistance to apoptosis, demonstrating that cytokines released by preconditioned cells play a key role in the anti-apoptotic effects of CoPP. Preconditioning CSCs with CoPP also induced an increase in the phosphorylation of Erk1/2, which are known to modulate multiple pro-survival genes. These results potentially provide a simple and effective strategy to enhance survival of CSCs after transplantation and, therefore, their efficacy in repairing infarcted myocardium.

LIF maintains progenitor phenotype of endothelial progenitor cells via Krüppel-like factor 4

BACKGROUND

Endothelial progenitor cells (EPCs) participate in post-natal vasculogenesis. Maintaining the preliminary progenitor phenotype and good proliferation capacity of EPCs is key to their use in treating cardiovascular ischemic diseases. However, transcriptional regulation in EPCs remains largely unknown. We investigated the effect of leukemia inhibitory factor (LIF) combined with vascular endothelial growth factor (VEGF) on EPCs and the potential roles of Krüppel-like transcription factors (KLFs).

METHODS AND RESULTS

Co-treatment with LIF and VEGF (100 ng/ml each) (V+L) could increase EPC colony-forming units and CD34 expression, which reflects the EPC progenitor phenotype and alleviated differentiation of EPCs. The effect was associated with Akt activation and increased expression of KLF4. Upregulation of KLF4 induced by V+L could be inhibited by transfection with dominant-negative Akt adenovirus. Furthermore, overexpression of KLF4 in EPCs enhanced the expression of CD34 and alleviated cell differentiation but did not increase the phosphorylation of Akt.

CONCLUSIONS

LIF combined with VEGF can maintain the preliminary, progenitor phenotype of EPCs and alleviate cell differentiation by upregulating KLF4, which may provide new insights into transcriptional regulation in EPCs.

Preservation of myocardial structure is enhanced by pim-1 engineering of bone marrow cells

RATIONALE

Bone marrow-derived cells to treat myocardial injury improve cardiac function and support beneficial cardiac remodeling. However, survival of stem cells is limited due to low proliferation of transferred cells.

OBJECTIVE

To demonstrate long-term potential of c-kit(+) bone marrow stem cells (BMCs) enhanced with Pim-1 kinase to promote positive cardiac remodeling.

METHODS AND RESULTS

Lentiviral modification of c-kit(+) BMCs to express Pim-1 (BMCeP) increases proliferation and expression of prosurvival proteins relative to BMCs expressing green fluorescent protein (BMCe). Intramyocardial delivery of BMCeP at time of infarction supports improvements in anterior wall dimensions and prevents left ventricle dilation compared with hearts treated with vehicle alone. Reduction of the akinetic left ventricular wall was observed in BMCeP-treated hearts at 4 and 12 weeks after infarction. Early recovery of cardiac function in BMCeP-injected hearts facilitated modest improvements in hemodynamic function up to 12 weeks after infarction between cell-treated groups. Persistence of BMCeP is improved relative to BMCe within the infarct together with increased recruitment of endogenous c-kit(+) cells. Delivery of BMC populations promotes cellular hypertrophy in the border and infarcted regions coupled with an upregulation of hypertrophic genes. Thus, BMCeP treatment yields improved structural remodeling of infarcted myocardium compared with control BMCs.

CONCLUSIONS

Genetic modification of BMCs with Pim-1 may serve as a therapeutic approach to promote recovery of myocardial structure. Future approaches may take advantage of salutary BMC actions in conjunction with other stem cell types to increase efficacy of cellular therapy and improve myocardial performance in the injured myocardium.

Glycoprotein 130 cytokine signal as a therapeutic target against cardiovascular diseases

Postnatal cardiomyocytes have only limited capacity of proliferation. Therefore, the myocardium is intrinsically equipped with cardioprotective machineries and protects itself from pathological stresses. One of the most important cardioprotective systems is the signal network of autocrine/paracrine factors, including neurohumoral factors, growth factors, and cytokines. In this review, we focus on the roles of interleukin-6 (IL-6) family cytokines, also known as glycoprotein 130 (gp130) cytokines, in cardioprotection. These cytokines make a complex with their specific cytokine receptor α-subunits. The cytokine-receptor α-subunit complex binds to gp130, a common receptor of the IL-6 family, followed by the activation of JAK/STAT, ERK, and PI3 kinase/Akt pathways. In cardiomyocytes, signals through gp130 promote cell survival and angiogenesis through the JAK/STAT pathway. Activation of gp130 in cardiac stem cells induces their endothelial transdifferentiation, leading to neovascularization. Recently, accumulating evidence has revealed that altered JAK/STAT activity is associated with heart failure, suggesting that the JAK/STAT pathway is a therapeutic target against cardiovascular diseases. Interestingly, activation of the JAK/STAT pathway with interleukin-11 (IL-11) exhibits preconditioning effects in ischemia/reperfusion model. Moreover, IL-11 treatment after coronary ligation prevents cardiac remodeling through the JAK/STAT pathway. Since IL-11 is used for patients with thrombocytopenia, we propose that IL-11 is a candidate cytokine clinically available for cardioprotection therapy.

Purification and long-term expansion of multipotent endothelial-like cells with potential cardiovascular regeneration

Endothelial progenitor cells (EPC) represent a relatively rare cell population, and expansion of sufficient cell numbers remains a challenge. Nevertheless, human adipose-derived stem cells (hASC) can be easily isolated and possess the ability to differentiate into endothelial cells. Here, we propose the isolation and characterization of multipotent endothelial-like cells (ME-LC) with the capacity to maintain their vascular progenitor properties for long periods. hASC were isolated from lipoaspirates and cultured through distinct consecutive culture stages for 2 months to enrich ME-LC: first in Dulbecco's modified Eagle's medium-fetal bovine serum (stage I), followed by a stage of culture in absent of fetal bovine serum (stage II), a culture in SFO3 medium (stage III), and, finally, the culture of ME-LC into collagen IV-coated flasks in endothelial growth medium (EGM-2) (stage IV). ME-LC display increased expression levels of endothelial and hematopoietic lineage markers (CD45, KDR, and CXCR4) and EPC markers (CD34 and CD133), whereas the expression of CD31 was barely detectable. Reverse transcription (RT)-polymerase chain reaction assays showed expression of genes involved in early stages of EPC differentiation and decreased expression of genes associated to differentiated EPC (TIE-2, DLL4, and FLT-1). ME-LC formed capillary-like structures when grown on Matrigel, secreted increased levels of stromal cell-derived factor-1 (SDF-1), and showed the ability to migrate attracted by SDF-1, vascular endothelial growth factor, and hematopoietic growth factor cytokines. Importantly, ME-LC retained the capacity to differentiate into cardiomyocyte-like cells. We present a simplified and efficient method to generate large numbers of autologous ME-LC from lipoaspirates-derived hASC, opening up potential cell-based therapies for cardiovascular regenerative medicine.

STAT3/Pim-1 signaling pathway plays a crucial role in endothelial differentiation of cardiac resident Sca-1+ cells both in vitro and in vivo

Cardiac stem cells potentially differentiate into cardiac cells, including cardiomyocytes and endothelial cells (ECs). Previously we demonstrated that STAT3 activation by IL-6 family cytokines, such as leukemia inhibitory factor (LIF), induces the endothelial differentiation of cardiac Sca-1+ cells. In this study, we addressed molecular mechanisms for EC differentiation of Sca-1+ cells. First, DNA array experiments were performed to search for the molecules induced by LIF. Among 134 genes that LIF upregulated by more than 4 fold, we focused on Pim-1 gene transcript, because Pim-1 is associated with the differentiation of some cell lineages. Real time RT-PCR analyses confirmed that LIF stimulation upregulated Pim-1 expression. Adenoviral transfection of dominant negative (dn) STAT3 inhibited LIF-mediated induction of Pim-1, while the overexpression of constitutively active STAT3 upregulated Pim-1 expression, suggesting that STAT3 activation is necessary and sufficient for Pim-1 induction. Moreover, in STAT3-deficient Sca-1+ cells, LIF failed to induce Pim-1 expression and EC differentiation. Importantly, the overexpression of dnPim-1 abrogated the induction of EC markers, indicating Pim kinase activity is indispensable for STAT3-mediated EC differentiation in vitro. Finally, Sca-1+ cells labeled with LacZ were transplanted into post-infarct myocardium and the transdifferentiation was estimated. The overexpression of wild-type STAT3 by adenovirus vector significantly promoted EC differentiation, while STAT3 gene ablation reduced the frequency of differentiating cells in post-infarct myocardium. Furthermore, transplanted Sca-1+ cells overexpressing dnPim-1 showed the reduced frequency of EC differentiation and capillary density. Collectively, Pim-1 kinase is upregulated by STAT3 activation in cardiac Sca-1+ cells and plays a pivotal role in EC differentiation both in vitro and in vivo.

Therapeutic Activation of Signal Transducer and Activator of Transcription 3 by Interleukin-11 Ameliorates Cardiac Fibrosis After Myocardial Infarction

Background— Glycoprotein 130 is the common receptor subunit for the interleukin (IL)-6 cytokine family. Previously, we reported that pretreatment of IL-11, an IL-6 family cytokine, activates the glycoprotein 130 signaling pathway in cardiomyocytes and prevents ischemia/reperfusion injury in vivo; however, its long-term effects on cardiac remodeling after myocardial infarction (MI) remain to be elucidated.

Methods and Results— MI was generated by ligating the left coronary artery in C57BL/6 mice. Real-time reverse transcription polymerase chain reaction analyses showed that IL-11 mRNA was remarkably upregulated in the hearts exposed to MI. Intravenous injection of IL-11 activated signal transducer and activator of transcription 3 (STAT3), a downstream signaling molecule of glycoprotein 130, in cardiomyocytes in vivo, suggesting that cardiac myocytes are target cells of IL-11 in the hearts. Twenty-four hours after coronary ligation, IL-11 was administered intravenously, followed by consecutive administration every 24 hours for 4 days. IL-11 treatment reduced fibrosis area 14 days after MI, attenuating cardiac dysfunction. Consistent with a previous report that STAT3 exhibits antiapoptotic and angiogenic activity in the heart, IL-11 treatment prevented apoptotic cell death of the bordering myocardium adjacent to the infarct zone and increased capillary density at the border zone. Importantly, cardiac-specific ablation of STAT3 abrogated IL-11–mediated attenuation of fibrosis and was associated with left ventricular enlargement. Moreover, with the use of cardiac-specific transgenic mice expressing constitutively active STAT3, cardiac STAT3 activation was shown to be sufficient to prevent adverse cardiac remodeling.

Conclusions— IL-11 attenuated cardiac fibrosis after MI through STAT3. Activation of the IL-11/glycoprotein 130/STAT3 axis may be a novel therapeutic strategy against cardiovascular diseases.

STAT3 induces muscle stem cell differentiation by interaction with myoD

Signal transducers and activators of transcription (STAT) family proteins transduce pivotal biological effects of various cytokines and hormones. STAT3 proteins are known to play a central role in the regulation of growth, differentiation, and survival of many types of cells. However, the function of STAT3 in myogenesis still remains largely unknown. We now provided direct evidence that STAT3 could induce myogenic differentiation and this effect might be mediated by interaction with MyoD--the essential transcription factor during myogenic differentiation. Furthermore, leukemia inhibitory factor (LIF) might be the upstream factor which activated JAK2/STAT3 pathway to stimulate muscle cell differentiation. Taken together, these results provide a molecular basis for further understanding of the muscle regeneration mechanism.

Signals through glycoprotein 130 regulate the endothelial differentiation of cardiac stem cells

OBJECTIVE

Cardiac Sca-1+ cells were originally identified as multipotent stem cells. To address the regulation of their differentiation, we investigated the effects of the proinflammatory cytokines on their endothelial differentiation.

METHODS AND RESULTS

We examined the effects of the proinflammatory cytokines including tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-1beta, IL-6, IL-11, and cardiotrophin-1 (CT-1) on the cardiac Sca-1+ cell differentiation. IL-11 and CT-1, whose receptor systems use glycoprotein 130 (gp130), induced endothelial-specific genes in Sca-1+ cells, but not TNF-alpha, IL-1beta, or IL-6, analyzed by RT-PCR and by immunocytochemistry. Immnunoblot analyses showed that IL-11 and CT-1 activated signal transducer and activator of transcription 3 (STAT3), a downstream target of gp130, but not other cytokines. Though IL-6 receptor is not endogenously expressed in Sca-1+ cells, IL-6 exhibited the activity to induce the endothelial markers in the presence of soluble IL-6 receptor, an agonistic receptor, associated with STAT3 phosphorylation. Moreover, the inhibition of STAT3, by its dominant-negative form or siRNA, suppressed the induction of endothelial specific genes by IL-11 and CT-1. Finally, LIF and IL-11 transcripts were upregulated in postinfarct myocardium, accompanied by the induction of Sca-1+/VE-cadherin+ cells.

CONCLUSIONS

Gp130/STAT3 pathway plays critical roles in the regulation of endothelial differentiation of cardiac Sca-1+ cells.

Leukemia inhibitory factor is upregulated in coronary arteries of Ossabaw miniature swine after stent placement

Leukemia inhibitory factor (LIF), an IL-6 class cytokine, is reported to be antiatherosclerotic. Thus, we hypothesized that LIF expression might be altered during in-stent neointimal hyperplasia. Ossabaw miniature swine, a unique large-animal model of metabolic syndrome and cardiovascular disease, were used for these studies. Bare-metal stents were deployed in the left anterior descending and left circumflex coronary arteries. Stents were expanded to either 1.0 x luminal diameter (in accordance with current clinical practice) or 1.3 x (overexpansion). The development of in-stent neointimal hyperplasia was assessed 28-day postimplantation using intravascular ultrasound. The atherosclerotic coverage of the vessel wall was approximately five-fold higher in 1.0 x stents and approximately nine-fold higher in 1.3 x stents 4 weeks after deployment, compared with the same segments before stenting. LIF mRNA was elevated approximately 11-fold in stented segments, relative to unstented epicardial coronary arteries. LIF expression and the intima : media ratio were strongly correlated in 1.0 x stented vessels. Further studies to investigate the nature of the association between LIF and neointimal hyperplasia revealed that vascular smooth muscle cell proliferation was inhibited by LIF treatment in an in-vitro model of atherosclerosis (coronary artery organ culture). These novel and clinically relevant studies show that elevated LIF gene expression is predictive for in-stent neointimal hyperplasia, and suggest that LIF upregulation may be a compensatory mechanism in this setting.

Endothelial cell lineages of the heart

During early gastrulation, vertebrate embryos begin to produce endothelial cells (ECs) from the mesoderm. ECs first form primitive vascular plexus de novo and later differentiate into arterial, venous, capillary, and lymphatic ECs. In the heart, the five distinct EC types (endocardial, coronary arterial, venous, capillary, and lymphatic) have distinct phenotypes. For example, coronary ECs establish a typical vessel network throughout the myocardium, whereas endocardial ECs form a large epithelial sheet with no angiogenic sprouting into the myocardium. Neither coronary arteries, veins, and capillaries, nor lymphatic vessels fuse with the endocardium or open to the heart chamber. The developmental stage during which the specific phenotype of each cardiac EC type is determined remains unclear. The mechanisms involved in EC commitment and diversity can however be more precisely defined by tracking the migratory patterns and lineage decisions of the precursors of cardiac ECs.

STAT3: a critical transcription activator in angiogenesis

Angiogenesis, the formation of new blood vessels from the pre-existing vasculature, is a complex multistage process regulated by a number of signal transduction pathways. Accumulating evidence suggests that signal transducer and activator of transcription (STATs), mainly STAT3, play an important role in angiogenesis under both physiological and pathological conditions in addition to cell survival, proliferation, differentiation, and oncogenesis. STAT3, as a critical multifunctional mediator, regulates many aspects of angiogenesis at the transcriptional level. This review will highlight the pivotal role of STAT3 in well-studied tumorous angiogenesis and cardiac angiogenesis, and summarize various potential mechanisms utilized by STAT3 to regulate the transcriptional activation of VEGF.

Leukaemia inhibitory factor is over-expressed by ischaemic brain tissue concomitant with reduced plasma expression following acute stroke

Leukaemia inhibitory factor (LIF) is a glycoprotein of the interleukin-6 family, which has potent pro-inflammatory properties and is involved in regulation of neuronal differentiation. We have previously identified its upregulation in gene microarrays following acute ischaemic stroke in man. LIF expression and localization was measured in human ischaemic stroke autopsy specimens, in a rat model of middle cerebral artery occlusion (MCAO) and in human foetal neural cell cultures following oxygen-glucose deprivation (OGD) by Western blotting and immunohistochemistry. Circulating LIF was determined in the plasma of patients in the hyper-acute stroke phase using a multiplex enzyme-linked-immunosorbent serologic assay system. Patients demonstrated an increase in LIF expression in peri-infarcted regions with localization in neurons and endothelial cells of microvessels surrounding the infarcted core. The rat MCAO model showed similar upregulation in neurons with a peak increase at 90 min. Circulating serum LIF expression was significantly decreased in the hyper-acute phase of stroke. Brain-derived neurons and glia cultured in vitro demonstrated an increase in gene/protein and protein expression respectively following exposure to OGD. Increased LIF expression in peri-infarcted regions and sequestration from the peripheral circulation in acute stroke patients are characteristic of the pathobiological response to ischaemia and tissue damage.

Identification of cardiac myocytes as the target of interleukin 11, a cardioprotective cytokine

Interleukin (IL)-6 family cytokines, which share glycoprotein 130 (gp130) as a signal-transducing receptor component, play important roles in the maintenance of cardiac homeostasis. IL-11, a member of IL-6 family cytokines, is expressed in cardiac myocytes, though it remains to be elucidated how IL-11 functions in the hearts. In the present study, first, we showed that IL-11 administration reduced the ischemia/reperfusion injury in the hearts. IL-11 receptor alpha was expressed in cardiomyocytes. IL-11 treatment rapidly activated signal transducer and activator of transcription 3 (STAT3) and extracellular signal-regulated kinase (ERK) 1/2 in cardiac myocytes. IL-11 stimulation resulted in the translocation of phosphorylated STAT3 into nuclei. Immunofluorescence microscopic analyses revealed that IL-11 treatment led to the cell elongation, as is the case with other cardiotrophic members of IL-6 family, such as leukemia inhibitory factor. Finally we showed that IL-11 treatment conferred the resistance to cell death induced by hydrogen peroxide, which was abrogated by adenoviral transfer of dominant negative STAT3, but not by the inhibition of ERK1/2 with U0126. These findings indicate that IL-11 mediates cytoprotective signals in cardiomyocytes, proposing that IL-11 has the potential to exhibit cardioprotection as a novel biological function.

Epigenetics and the plasticity of differentiation in normal and cancer stem cells

Embryonic stem cells are characterized by their differentiation to all cell types during embryogenesis. In adult life, different tissues also have somatic stem cells, called adult stem cells, which in specific niches can undergo multipotent differentiation. The use of these adult stem cells has considerable therapeutic potential for the regeneration of damaged tissues. In both embryonic and adult stem cells, differentiation is controlled by epigenetic mechanisms, and the plasticity of differentiation in these cells is associated with transcription accessibility for genes expressed in different normal tissues. Abnormalities in genetic and/or epigenetic controls can lead to development of cancer, which is maintained by self-renewing cancer stem cells. Although the genetic abnormalities produce defects in growth and differentiation in cancer stem cells, these cells have not always lost the ability to undergo differentiation through epigenetic changes that by-pass the genomic abnormalities, thus creating the basis for differentiation therapy. Like normal stem cells, cancer stem cells can show plasticity for differentiation. This plasticity of cancer stem cells is also associated with transcription accessibility for genes that are normally expressed in different tissues, including tissues other than those from which the cancers originated. This broad transcription accessibility can also contribute to the behavior of cancer cells by overexpressing genes that promote cell viability, growth and metastasis.