STAT3-dependent mouse embryonic stem cell differentiation into cardiomyocytes: analysis of molecular signaling and therapeutic efficacy of cardiomyocyte precommitted mES transplantation in a mouse model of myocardial infarction

scaRNA20 promotes pseudouridylatory modification of small nuclear snRNA U12 and improves cardiomyogenesis

Non-coding RNAs, particularly small Cajal-body associated RNAs (scaRNAs), play a significant role in spliceosomal RNA modifications. While their involvement in ischemic myocardium regeneration is known, their role in cardiac development is unexplored. We investigated scaRNA20's role in iPSC differentiation into cardiomyocytes (iCMCs) via overexpression and knockdown assays. We measured scaRNA20-OE-iCMCs and scaRNA20-KD-iCMCs contractility using Particle Image Velocimetry (PIV), comparing them to control iCMCs. We explored scaRNA20's impact on alternative splicing via pseudouridylation (Ψ) of snRNA U12, analyzing its functional consequences in cardiac differentiation. scaRNA20-OE-iPSC differentiation increased beating colonies, upregulated cardiac-specific genes, activated TP53 and STAT3, and preserved contractility under hypoxia. Conversely, scaRNA20-KD-iCMCs exhibited poor differentiation and contractility. STAT3 inhibition in scaRNA20-OE-iPSCs hindered cardiac differentiation. RNA immunoprecipitation revealed increased Ψ at the 28th uridine of U12 RNA in scaRNA20-OE iCMCs. U12-KD iCMCs had reduced cardiac differentiation, which improved upon U12 RNA introduction. In summary, scaRNA20-OE in iPSCs enhances cardiomyogenesis, preserves iCMC function under hypoxia, and may have implications for ischemic myocardium regeneration.

Epigenetic Modification Factors and microRNAs Network Associated with Differentiation of Embryonic Stem Cells and Induced Pluripotent Stem Cells toward Cardiomyocytes: A Review

More research is being conducted on myocardial cell treatments utilizing stem cell lines that can develop into cardiomyocytes. All of the forms of cardiac illnesses have shown to be quite amenable to treatments using embryonic (ESCs) and induced pluripotent stem cells (iPSCs). In the present study, we reviewed the differentiation of these cell types into cardiomyocytes from an epigenetic standpoint. We also provided a miRNA network that is devoted to the epigenetic commitment of stem cells toward cardiomyocyte cells and related diseases, such as congenital heart defects, comprehensively. Histone acetylation, methylation, DNA alterations, N6-methyladenosine (m⁶a) RNA methylation, and cardiac mitochondrial mutations are explored as potential tools for precise stem cell differentiation.

Microparticles from Hyperphosphatemia-Stimulated Endothelial Cells Promote Vascular Calcification Through Astrocyte-Elevated Gene-1

Endothelial microparticles (EMPs) can be released in chronic kidney disease (CKD). Plasma concentration of high inorganic phosphate (HP) is considered as a decisive determinant of vascular calcification in CKD. We therefore explored the role of HP-induced EMPs (HP-EMPs) in the vascular calcification and its potential mechanism. We observed the shape of HP-EMPs captured by vascular smooth muscle cells (VSMCs) dynamically changed from rare dots, rosettes, to semicircle or circle. Our results demonstrated that HP-EMPs could directly promote VSMC calcification, or accelerate HP-induced calcification through signal transducers and activators of transcription 3 (STAT3)/bone morphogenetic protein-2 (BMP2) signaling pathway. AEG-1 activity was increased through HP-EMPs-induced VSMC calcification, in arteries from uremic rats, or from uremic rats treated with HP-EMPs. AEG-1 deficiency blocked, whereas AEG-1 overexpression exacerbated, the calcium deposition of VSMCs. AEG-1, a target of miR-153-3p, could be suppressed by agomiR-153-3p. Notably, VSMC-specific enhance of miR-153-3p by tail vein injection of aptamer-agomiR-153-3p decreased calcium deposition in both uremia rats treated with HP-EMPs or not. HP-EMPs could directly induce VSMCs calcification and accelerate Pi-induced calcification, and AEG-1 may act as crucial regulator of HP-EMPs-induced vascular calcification. This study sheds light on the therapeutic agents that influence HP-EMPs production or AEG-1 activity, which may be of benefit to treat vascular calcification.

Comparative analysis of human induced pluripotent stem cell-derived mesenchymal stem cells and umbilical cord mesenchymal stem cells

Generation of induced pluripotent stem cells (iPSCs) and their differentiation into mesenchymal stem/stromal cells (iMSCs) have created exciting source of cells for autologous therapy. In this study, we have compared the therapeutic potential of iMSCs generated from urinary epithelial (UE) cells with the available umbilical cord MSCs (UC‐MSCs). For this, adult UE cells were treated with the mRNA of pluripotent genes (OCT4, NANOG, SOX2, KLF4, MYC and LIN28) and a cocktail of miRNAs under specific culture conditions for generating iPSCs. Our non‐viral and mRNA‐based treatment regimen demonstrated a high reprogramming efficiency to about 30% at passage 0. These UE‐iPSCs were successfully differentiated further into ectoderm, endoderm and mesoderm lineage of cells. Moreover, these UE‐iPSCs were subsequently differentiated into iMSCs and were compared with the UC‐MSCs. These iMSCs were capable of differentiating into osteocytes, chondrocytes and adipocytes. Our qRT‐PCR and Western blot data showed that the CD73, CD90 and CD105 gene transcripts and proteins were highly expressed in iMSCs and UC‐MSCs but not in other cells. The comparative qRT‐PCR data showed that the iMSCs maintained their MSC characteristics without any chromosomal abnormalities even at later passages (P15), during which the UC‐MSCs started losing their MSC characteristics. Importantly, the wound‐healing property demonstrated through migration assay was superior in iMSCs when compared to the UC‐MSCs. In this study, we have demonstrated an excellent non‐invasive and pain‐free method of obtaining iMSCs for regenerative therapy. These homogeneous autologous highly proliferative iMSCs may provide an alternative source of cells to UC‐MSCs for treating various diseases.

Epigenetic Regulation of Cardiomyocyte Differentiation from Embryonic and Induced Pluripotent Stem Cells

With the intent to achieve the best modalities for myocardial cell therapy, different cell types are being evaluated as potent sources for differentiation into cardiomyocytes. Embryonic stem cells and induced pluripotent stem cells have great potential for future progress in the treatment of myocardial diseases. We reviewed aspects of epigenetic mechanisms that play a role in the differentiation of these cells into cardiomyocytes. Cardiomyocytes proliferate during fetal life, and after birth, they undergo permanent terminal differentiation. Upregulation of cardiac-specific genes in adults induces hypertrophy due to terminal differentiation. The repression or expression of these genes is controlled by chromatin structural and epigenetic changes. However, few studies have reviewed and analyzed the epigenetic aspects of the differentiation of embryonic stem cells and induced pluripotent stem cells into cardiac lineage cells. In this review, we focus on the current knowledge of epigenetic regulation of cardiomyocyte proliferation and differentiation from embryonic and induced pluripotent stem cells through histone modification and microRNAs, the maintenance of pluripotency, and its alteration during cardiac lineage differentiation.

Emerging Roles of Extracellular Vesicles Derived Non-Coding RNAs in the Cardiovascular System

Cardiovascular disease is the leading cause of morbidity and mortality all over the world. Emerging evidence emphasize the importance of extracellular vesicles (EVs) in the cell to cell communication in the cardiovascular system which is majorly mediated through non-coding RNA cargo. Advancement in sequencing technologies revealed a major proportion of human genome is composed of non-coding RNAs viz., miRNAs, lncRNAs, tRNAs, snoRNAs, piRNAs and rRNAs. However, our understanding of the role of ncRNAs-containing EVs in cardiovascular health and disease is still in its infancy. This book chapter provides a comprehensive update on our understanding on the role of EVs derived ncRNAs in the cardiovascular pathophysiology and their therapeutic potential.

Crystal Structures of Ternary Complexes of MEF2 and NKX2-5 Bound to DNA Reveal a Disease Related Protein-Protein Interaction Interface

MEF2 and NKX2-5 transcription factors interact with each other in cardiogenesis and are necessary for normal heart formation. Despite evidence suggesting that these two transcription factors function synergistically and possibly through direct physical interactions, molecular mechanisms by which they interact are not clear. Here we determined the crystal structures of ternary complexes of MEF2 and NKX2-5 bound to myocardin enhancer DNA in two crystal forms. These crystal structures are the first example of human MADS-box/homeobox ternary complex structures involved in cardiogenesis. Our structures reveal two possible modes of interactions between MEF2 and NKX2-5: MEF2 and NKX bind to adjacent DNA sites to recognize DNA in cis; and MEF2 and NKX bind to different DNA strands to interact with each other in trans via a conserved protein-protein interface observed in both crystal forms. Disease-related mutations are mapped to the observed protein-protein interface. Our structural studies provide a starting point to understand and further study the molecular mechanisms of the interactions between MEF2 and NKX2.5 and their roles in cardiogenesis.

CUEDC2 controls osteoblast differentiation and bone formation via SOCS3-STAT3 pathway

The CUE domain-containing 2 (CUEDC2) protein plays critical roles in many biological processes, such as the cell cycle, inflammation, and tumorigenesis. However, whether CUEDC2 is involved in osteoblast differentiation and plays a role in bone regeneration remains unknown. This study investigated the role of CUEDC2 in osteogenesis and its underlying molecular mechanisms. We found that CUEDC2 is expressed in bone tissues. The expression of CUEDC2 decreased during bone development and BMP2-induced osteoblast differentiation. The overexpression of CUEDC2 suppressed the osteogenic differentiation of precursor cells, while the knockdown of CUEDC2 showed the opposite effect. In vivo studies showed that the overexpression of CUEDC2 decreased bone parameters (bone volume, bone area, and bone mineral density) during ectopic bone formation, whereas its knockdown increased bone volume and the reconstruction percentage of critical-size calvarial defects. We found that CUEDC2 affects STAT3 activation by regulating SOCS3 protein stability. Treatment with a chemical inhibitor of STAT3 abolished the promoting effect of CUEDC2 silencing on osteoblast differentiation. Together, we suggest that CUEDC2 functions as a key regulator of osteoblast differentiation and bone formation by targeting the SOCS3–STAT3 pathway. CUEDC2 manipulation could serve as a therapeutic strategy for controlling bone disease and regeneration.

Linc02349 promotes osteogenesis of human umbilical cord-derived stem cells by acting as a competing endogenous RNA for miR-25-3p and miR-33b-5p

Objectives

Increasing evidences suggest that inducing mesenchymal stem cells to differentiate into osteoblasts has been as an especially important component in the prevention and therapy for degenerative bone disease. Here, we identify a novel lncRNA, linc02349, which increases significantly during osteogenic differentiation.

Materials and methods

Human umbilical cord‐derived stem cells (hUC‐MSCs) and dental pulp mesenchymal stem cells were used. Overexpression and knockdown of linc02349 in cell lines were generated using lentiviral‐mediated gene delivery method. Bioinformatics prediction, Ago2‐RIP assay and dual‐luciferase reporter system were employed to examine miRNA which interacts with linc02349. The RNA FISH assay was performed to identify the subcelluar location of linc02349. Alizarin Red S staining, ALP staining and qPCR were applied to identify the osteogenic differentiation. The potential linc02349‐regulated genes, miR‐25‐3p and miR‐33b‐5p, were explored by ChIP, RIP and Western blotting assays. Micro‐CT was used to measure the osteogenic content in bone formation assay in vivo.

Results

Linc02349 overexpression improves osteogenic differentiation by in vitro and in vivo analysis. Mechanistically, linc02349 acts as a molecular sponge for miR‐25‐3p and miR‐33b‐5p to control expression abundance of SMAD5 and Wnt10b, respectively, which eventually activated Dlx5/OSX pathway and hence promoted osteogenic differentiation. In addition, we revealed that STAT3 interacts with linc02349 promoter region and positively regulates the linc02349 transcriptional activity.

Conclusion

These findings identify that linc02349 modulates the osteogenic differentiation through acting as a sponge RNA of miR‐25‐3p and miR‐33b‐5p and regulating SMAD5 and Wnt10b, and proposed a new interaction between STAT3 and linc02349, which could be a potential target in the process the osteogenesis of hUC‐MSCs for future clinical application.

Non-viral reprogramming and induced pluripotent stem cells for cardiovascular therapy

Despite significant effort devoted to developing new treatments and procedures, cardiac disease is still one of the leading causes of death in the world. The loss of myocytes due to ischemic injury remains a major therapeutic challenge. However, cell-based therapy to repair the injured heart has shown significant promise in basic and translation research and in clinical trials. Embryonic stem cells have been successfully used to improve cardiac outcomes. Unfortunately, treatment with these cells is complicated by ethical and legal issues. Recent progress in developing induced pluripotent stem cells (iPSCs) using non-viral vectors has made it possible to derive cardiomyocytes for therapy. This review will focus on these non-integration-based approaches for reprogramming and their therapeutic advantages for cardiovascular medicine.

Extracellular Vesicles and the Application of System Biology and Computational Modeling in Cardiac Repair

Recent literature suggests that extracellular vesicles (EVs), secreted from most cells and containing cell-specific cargo of proteins, lipids, and nucleic acids, are major driver of intracellular communication in normal physiology and pathological conditions. The recent evidence on stem/progenitor cell EVs as potential therapeutic modality mimicking their parental cell function is exciting because EVs could possibly be used as a surrogate for the stem cell-based therapy, and this regimen may overcome certain roadblocks identified with the use of stem/progenitor cell themselves. This review provides a comprehensive update on our understanding on the role of EVs in cardiac repair and emphasizes the applications of stem/progenitor cell-derived EVs as therapeutics and discusses the current challenges associated with the EV therapy.

STAT3-Inducible Mouse ESCs: A Model to Study the Role of STAT3 in ESC Maintenance and Lineage Differentiation

Studies have demonstrated that STAT3 is essential in maintaining self-renewal of embryonic stem cells (ESCs) and modulates ESC differentiation. However, there is still lack of direct evidence on STAT3 functions in ESCs and embryogenesis because constitutive STAT3 knockout (KO) mouse is embryonic lethal at E6.5-E7.5, prior to potential functional role in early development can be assessed. Therefore, in this study, two inducible STAT3 ESC lines were established, including the STAT3 knockout (InSTAT3 KO) and pSTAT3 overexpressed (InSTAT3 CA) using Tet-on inducible system in which STAT3 expression can be strictly controlled by doxycycline (Dox) stimulation. Through genotyping, deletion of STAT3 alleles was detected in InSTAT3 KO ESCs following 24 hours Dox stimulation. Western blot also showed that pSTAT3 and STAT3 protein levels were significantly reduced in InSTAT3 KO ESCs while dominantly elevated in InSTAT3 CA ECSs upon Dox stimulation. Likewise, it was found that STAT3-null ESCs would affect the differentiation of ESCs into mesoderm and cardiac lineage. Taken together, the findings of this study indicated that InSTAT3 KO and InSTAT3 CA ESCs could provide a new tool to clarify the direct targets of STAT3 and its role in ESC maintenance, which will facilitate the elaboration of the mechanisms whereby STAT3 maintains ESC pluripotency and regulates ESC differentiation during mammalian embryogenesis.

DNMT and HDAC inhibitors together abrogate endotoxemia mediated macrophage death by STAT3-JMJD3 signaling

Acute lung injury (ALI) is a common complication of sepsis that often leads to fatal lung disease without effective therapies. It is known that bone marrow derived macrophages are important in resolving the inflammation and maintaining tissue homeostasis. Here, we hypothesize that treatment in combination of DNA methyl transferase inhibitor (DNMTi) 5-Aza 2-deoxycytidine (Aza) and histone deacetylase inhibitor (HDACi) Trichostatin A (TSA) mitigates the inflammation induced pyroptosis and apoptosis during endotoxemia induced ALI. To test this hypothesis, the mice challenged with a sublethal dose of LPS followed by one-hour post-treatment with a single dose of Aza and TSA intraperitoneally showed a substantial attenuation of apoptosis and inflammation. Importantly, we observed significant changes in the mitochondrial membrane structure, and lower levels of DNA fragmentation, reduced expression of apoptotic and pyroptotic genes both transcriptionally and translationally in LPS induced BMDMs treated by a combination of Aza and TSA than in LPS-induced BMDMs treated with either drug alone. The protection was mediated by an inhibition of JNK-ERK and STAT3-JMJD3 activated pathways. Thus, targeting these important signaling pathways with the combination of Aza and TSA would be a good treatment modality for ALI.

Regenerative Therapy for Cardiomyopathies

Despite substantial advances in the development of medical and interventional strategies in ischemic and non-ischemic heart diseases, cardiovascular diseases (CVDs) remain the leading cause of mortality and morbidity worldwide. Stem cell therapy for heart disease has gained traction over the past two decades and is an emerging option for the treatment of myocardial dysfunction. In this review, we summarize the current literature on different types of stem cells and their potential usage in ischemic and non-ischemic heart diseases. We emphasize the clinical utility of stem cells to improve myocardial structural and function, promote microvascular angiogenesis, and diminish scar size and major adverse cardiovascular events. We also discuss the therapeutic potential of microvesicles, such as exosomes, in the treatment of CVDs, which may open novel avenues for further clinical studies.

Exosomes: Outlook for Future Cell-Free Cardiovascular Disease Therapy

Cardiovascular diseases are the number one cause of death globally with an estimated 7.4 million people dying from coronary heart disease. Studies have been conducted to identify the therapeutic utility of exosomes in many diseases, including cardiovascular diseases. It has been demonstrated that exosomes are immune modulators, can be used to treat cardiac ischemic injury, pulmonary hypertension and many other diseases, including cancers. Exosomes can be used as a biomarker for disease and cell-free drug delivery system for targeting the cells. Many studies suggest that exosomes can be used as a cell-free vaccine for many diseases. In this chapter, we explore the possibility of future therapeutic potential of exosomes in various cardiovascular diseases.

Is Cardioprotection Dead?

For >4 decades, the holy grail in the treatment of acute myocardial infarction has been the mitigation of lethal injury. Despite promising initial results and decades of investigation by the cardiology research community, the only treatment with proven efficacy is early reperfusion of the occluded coronary artery. The remarkable record of failure has led us and others to wonder if cardioprotection is dead. The path to translation, like the ascent to Everest, is certainly littered with corpses. We do, however, highlight a therapeutic principle that provides a glimmer of hope: cellular postconditioning. Administration of cardiosphere-derived cells after reperfusion limits infarct size measured acutely, while providing long-term structural and functional benefits. The recognition that cell therapy may be cardioprotective, and not just regenerative, merits further exploration before we abandon the pursuit entirely.

Severe Convulsions and Dysmyelination in Both Jimpy and Cx32/47 -/- Mice may Associate Astrocytic L-Channel Function with Myelination and Oligodendrocytic Connexins with Internodal Kv Channels

The Jimpy mouse illustrates the importance of interactions between astrocytes and oligodendrocytes. It has a mutation in Plp coding for proteolipid protein and DM20. Its behavior is normal at birth but from the age of ~2 weeks it shows severe convulsions associated with oligodendrocyte/myelination deficits and early death. A normally occurring increase in oxygen consumption by highly elevated K+ concentrations is absent in Jimpy brain slices and cultured astrocytes, reflecting that Plp at early embryonic stages affects common precursors as also shown by the ability of conditioned medium from normal astrocytes to counteract histological abnormalities. This metabolic response is now known to reflect opening of L-channels for Ca2+. The resulting deficiency in Ca2+ entry has many consequences, including lack of K+-stimulated glycogenolysis and release of gliotransmitter ATP. Lack of purinergic stimulation compromises oligodendrocyte survival and myelination and affects connexins and K+ channels. Mice lacking the oligodendrocytic connexins Cx32 and 47 show similar neurological dysfunction as Jimpy. This possibly reflects that K+ released by intermodal axonal Kv channels is transported underneath a loosened myelin sheath instead of reaching the extracellular space via connexin-mediated transport to oligodendrocytes, followed by release and astrocytic Na+,K+-ATPase-driven uptake with subsequent Kir4.1-facilitated release and neuronal uptake.

The acceleration of cardiomyogenesis in embryonic stem cells in vitro by serum depletion does not increase the number of developed cardiomyocytes

The differentiation of pluripotent embryonic stem (ES) cells into various lineages in vitro represents an important tool for studying the mechanisms underlying mammalian embryogenesis. It is a key technique in studies evaluating the molecular mechanisms of cardiomyogenesis and heart development and also in embryotoxicology. Herein, modest modifications of the basic protocol for ES cell differentiation into cardiomyocytes were evaluated in order to increase the yield and differentiation status of developed cardiomyocytes. Primarily, the data show that ES cell cultivation in the form of non-adherent embryoid bodies (EBs) for 5 days compared to 8 days significantly improved cardiomyogenic differentiation. This is illustrated by the appearance of beating foci in the adherent EBs layer at earlier phases of differentiation from day 10 up to day 16 and by the significantly higher expression of genes characteristic of cardiomyogenic differentiation (sarcomeric alpha actinin, myosin heavy chain alpha and beta, myosin light chain 2 and 7, and transcriptional factor Nkx2.5) in EBs cultivated under non-adherent conditions for 5 days. The ratio of cardiomyocytes per other cells was also potentiated in EBs cultivated in non-adherent conditions for only 5 days followed by cultivation in adherent serum-free culture conditions. Nevertheless, the alteration in the percentage of beating foci among these two tested cultivation conditions vanished at later phases and also did not affect the total number of cardiomyocytes determined as myosin heavy chain positive cells at the end of the differentiation process on day 20. Thus, although these modifications of the conditions of ES cells differentiation may intensify cardiomyocyte differentiation, the final count of cardiomyocytes might not change. Thus, serum depletion was identified as a key factor that intensified cardiomyogenesis. Further, the treatment of EBs with N-acetylcysteine, a reactive oxygen species scavenger, did not affect the observed increase in cardiomyogenesis under serum depleted conditions. Interestingly, a mild induction of the ventricular-like phenotype of cardiomyocytes was observed in 5-day-old EBs compared to 8-day-old EBs. Overall, these findings bring crucial information on the mechanisms of ES cells differentiation into cardiomyocytes and on the establishment of efficient protocols for the cardiomyogenic differentiation of ES cells. Further, the importance of determining the absolute number of formed cardiomyocyte-like cells per seeded pluripotent cells in contrast to the simple quantification of the ratios of cells is highlighted.

Caveolin-1 Plays an Important Role in the Differentiation of Bone Marrow-Derived Mesenchymal Stem Cells into Cardiomyocytes

OBJECTIVES

Accumulating evidence has demonstrated that bone marrow-derived mesenchymal stem cells (BMSCs) may transdifferentiate into cardiomyocytes, making BMSCs a promising source of cardiomyocytes for transplantation. However, little is known about the molecular mechanisms underlying myogenic conversion of BMSCs.

METHODS

This study was designed to investigate the functional role of caveolin-1 in the cardiomyocyte differentiation of BMSCs and to explore the potential underlying molecular mechanisms.

RESULTS

BMSC differentiation was induced by treatment with 10 μM 5-azacytidine, and immunofluorescence assay showed that the expression of cardiomyocyte marker cardiac troponin T (cTnT) was significantly increased compared with a control group. Meanwhile, an increased caveolin-1 expression was found during the 5-azacytidine-induced BMSC differentiation. Additionally, the role of caveolin-1 in the differentiation process was then studied by using caveolin-1 siRNAs. We found that silencing caveolin-1 during induction remarkably enhanced the expression of cardiomyocyte marker genes, including cTnT, Nkx2.5 (cardiac-specific transcription factor), α-cardiac actin and α-myosin heavy chain (α-MHC). Moreover, we observed that downregulation of caveolin-1 was accompanied by inhibition of signal transducer and activator of transcription 3 (STAT3) phosphorylation.

CONCLUSIONS

Taken together, these findings demonstrate that caveolin-1 plays an important role in the differentiation of BMSCs into cardiomyocytes in conjunction with the STAT3 pathway.

Analysis of the dynamic co-expression network of heart regeneration in the zebrafish

The zebrafish has the capacity to regenerate its heart after severe injury. While the function of a few genes during this process has been studied, we are far from fully understanding how genes interact to coordinate heart regeneration. To enable systematic insights into this phenomenon, we generated and integrated a dynamic co-expression network of heart regeneration in the zebrafish and linked systems-level properties to the underlying molecular events. Across multiple post-injury time points, the network displays topological attributes of biological relevance. We show that regeneration steps are mediated by modules of transcriptionally coordinated genes, and by genes acting as network hubs. We also established direct associations between hubs and validated drivers of heart regeneration with murine and human orthologs. The resulting models and interactive analysis tools are available at http://infused.vital-it.ch. Using a worked example, we demonstrate the usefulness of this unique open resource for hypothesis generation and in silico screening for genes involved in heart regeneration.

Leukemia Inhibitory Factor Enhances Endogenous Cardiomyocyte Regeneration after Myocardial Infarction

Cardiac stem cells or precursor cells regenerate cardiomyocytes; however, the mechanism underlying this effect remains unclear. We generated CreLacZ mice in which more than 99.9% of the cardiomyocytes in the left ventricular field were positive for 5-bromo-4-chloro-3-indolyl-β-d-galactoside (X-gal) staining immediately after tamoxifen injection. Three months after myocardial infarction (MI), the MI mice had more X-gal-negative (newly generated) cells than the control mice (3.04 ± 0.38/mm², MI; 0.47 ± 0.16/mm², sham; p < 0.05). The cardiac side population (CSP) cell fraction contained label-retaining cells, which differentiated into X-gal-negative cardiomyocytes after MI. We injected a leukemia inhibitory factor (LIF)-expression construct at the time of MI and identified a significant functional improvement in the LIF-treated group. At 1 month after MI, in the MI border and scar area, the LIF-injected mice had 31.41 ± 5.83 X-gal-negative cardiomyocytes/mm², whereas the control mice had 12.34 ± 2.56 X-gal-negative cardiomyocytes/mm² (p < 0.05). Using 5-ethynyl-2'-deoxyurinide (EdU) administration after MI, the percentages of EdU-positive CSP cells in the LIF-treated and control mice were 29.4 ± 2.7% and 10.6 ± 3.7%, respectively, which suggests that LIF influenced CSP proliferation. Moreover, LIF activated the Janus kinase (JAK)signal transducer and activator of transcription (STAT), mitogen-activated protein kinase/extracellular signal-regulated (MEK)extracellular signal-regulated kinase (ERK), and phosphatidylinositol 3-kinase (PI3K)–AKT pathways in CSPs in vivo and in vitro. The enhanced green fluorescent protein (EGFP)-bone marrow-chimeric CreLacZ mouse results indicated that LIF did not stimulate cardiogenesis via circulating bone marrow-derived cells during the 4 weeks following MI. Thus, LIF stimulates, in part, stem cell-derived cardiomyocyte regeneration by activating cardiac stem or precursor cells. This approach may represent a novel therapeutic strategy for cardiogenesis.

Association of STAT3 with Cx26 and Cx43 in human uterine endometrioid adenocarcinoma

Signal transducer and activator of transcription-3 (STAT3) drives endometrial carcinogenesis, while signaling via gap junctions gets weakened during cancer progression. Connexin 26 (Cx26), Cx43 and STAT3 were immunohistochemically evaluated in 78 endometrioid adenocarcinomas: Nuclear expression of STAT3 positively correlated with cytoplasmic immunoreactivity to Cx43 (P=0.004, r=0.318) and Cx26 (P=0.006, r=0.309). STAT3 correlated with Cx43 (P=0.022, r=0.411) and Cx26 (P=0.008 r=0.466) in G1 tumors. A statistically significant linkage remained in G2 cancers between STAT3 and Cx43 (P=0.061, r=0.262) and Cx26 (P=0.016, r=0.331); however, no correlations were observed in G3 tumors. STAT3 was significantly associated with Cx 43 (p=0.003, r=0.684) and Cx26 (p=0.049, r=0.500) in estrogen receptor (ER) negative adenocarcinomas. STAT3 did not correlate with Cx43 in ER positive adenocarcinomas; however, STAT3 expression remained correlated with Cx26 expression (P=0.035, r=0.268). In progesterone receptor negative tumors STAT3 was significantly associated with Cx43 (P=0.035, r=0.451) and Cx26 (P<0.0001, r=0.707). However, in PgR positive adenocarcinomas STAT3 correlated with Cx43 (P=0.03, r=0.290) but not with Cx26. Thus, it appears that hormone dependent acceleration of cancer growth breaks the association between STAT3 and Cx expression. These associations become weaker as the tumors dedifferentiate from G1 to G3 endometrioid adenocarcinomas. The present study provides evidence that the loss of correlation between STAT3 and selected Cx proteins occurs in tumors with more aggressive behavior.

Effects of C-Reactive Protein on the Cardiac Differentiation of Mouse Embryonic Stem Cells

A major challenge in stem cell therapy for cardiac repair is how to obtain normally functioning stem cell-derived cardiomyocytes. We aim to address the effects of C-reactive protein (CRP) on the cardiac differentiation of embryonic stem (ES) cells. Immunostaining, Western blotting and electrophysiology were employed. A hundred fifty milligran/liters CRP significantly reduced the percentage of cardiomyocytes differentiated from mouse ES cells, while it may also promote sarcomere development compared to 30 mg/L CRP treatment. Further examination of the action potential (AP) in individual ES cell-derived cardiomyocytes showed that there exist three types of cardiomyocytes: artial-like (A-like), ventricular-like (V-like), and pacemaker-like (P-like). A hundred fifty milligran/liters CRP treatment decreased the P-like cardiomyocytes, whereas it increased the A-like. Such inhibitory effect and alteration were not significant at 30 mg/L CRP treatment. Moreover, 150 mg/L CRP significantly increased the APD90 (90% of duration of AP) and decreased the spontaneous firing rate of AP in P-like cells, while had little effect on other electrophysiological characteristics, including APA (AP amplitude) and MDP (maximum diastolic potential). This study revealed the effect of CRP on the cardiac differentiation of ES cells. It provides an in vitro pathological model and may be of importance to the future work of ES cell-based therapy in clinical applications and in vivo pathological studies.

Generation of Functional Cardiomyocytes from Efficiently Generated Human iPSCs and a Novel Method of Measuring Contractility

Human induced pluripotent stem cells (iPSCs) derived cardiomyocytes (iCMCs) would provide an unlimited cell source for regenerative medicine and drug discoveries. The objective of our study is to generate functional cardiomyocytes from human iPSCs and to develop a novel method of measuring contractility of CMCs. In a series of experiments, adult human skin fibroblasts (HSF) and human umbilical vein endothelial cells (HUVECs) were treated with a combination of pluripotent gene DNA and mRNA under specific conditions. The iPSC colonies were identified and differentiated into various cell lineages, including CMCs. The contractile activity of CMCs was measured by a novel method of frame-by-frame cross correlation (particle image velocimetry-PIV) analysis. Our treatment regimen transformed 4% of HSFs into iPSC colonies at passage 0, a significantly improved efficiency compared with use of either DNA or mRNA alone. The iPSCs were capable of differentiating both in vitro and in vivo into endodermal, ectodermal and mesodermal cells, including CMCs with >88% of cells being positive for troponin T (CTT) and Gata4 by flow cytometry. We report a highly efficient combination of DNA and mRNA to generate iPSCs and functional iCMCs from adult human cells. We also report a novel approach to measure contractility of iCMCs.

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.

Roles of STATs signaling in cardiovascular diseases

In cardiac and many other systems, chronic stress activates avfamily of structurally and functionally conserved receptors and their downstream signaling molecules that entail tyrosine, serine or threonine phosphorylation to transfer the messages to the genetic machinery. However, the activation of the Janus kinases (JAKs) and their downstream signal transducer and activator of transcription (STATs) proteins is both characteristic of and unique to cytokine and growth factor signaling which plays a central role in heart physiology. Dysregulation of JAK-STAT signaling is associated with various cardiovascular diseases. The molecular signaling and specificity of the JAK-STAT pathway are modulated at many levels by distinct regulatory proteins. Here, we review recent studies on the regulation of the STAT signaling pathway that will enhance our ability to design rational therapeutic strategies for stress-induced heart failure.

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.

Transcription Factor STAT3 as a Novel Molecular Target for Cancer Prevention

Signal Transducers and Activators of Transcription (STATs) are a family of transcription factors that regulate cell proliferation, differentiation, apoptosis, immune and inflammatory responses, and angiogenesis. Cumulative evidence has established that STAT3 has a critical role in the development of multiple cancer types. Because it is constitutively activated during disease progression and metastasis in a variety of cancers, STAT3 has promise as a drug target for cancer therapeutics. Recently, STAT3 was found to have an important role in maintaining cancer stem cells in vitro and in mouse tumor models, suggesting STAT3 is integrally involved in tumor initiation, progression and maintenance. STAT3 has been traditionally considered as nontargetable or undruggable, and the lag in developing effective STAT3 inhibitors contributes to the current lack of FDA-approved STAT3 inhibitors. Recent advances in cancer biology and drug discovery efforts have shed light on targeting STAT3 globally and/or specifically for cancer therapy. In this review, we summarize current literature and discuss the potential importance of STAT3 as a novel target for cancer prevention and of STAT3 inhibitors as effective chemopreventive agents.

Regenerative therapy for cardiovascular disease

Recent insights into myocardial biology uncovered a hereto unknown regenerative capacity of the adult heart. The discovery of dividing cardiomyocytes and the identification and characterization of cardiac stem and progenitor cells with myogenic and angiogenic potential have generated new hopes that cardiac regeneration and repair might become a therapeutic option. During the past decade, multiple candidate cells have been proposed for cardiac regeneration, and their mechanisms of action in the myocardium have been explored. Initial clinical trials have focused on the use of bone marrow-derived cells to promote myocardial regeneration in ischemic heart disease and have yielded very mixed results, with no clear signs of clinically meaningful functional improvement. Although the efficiency of bona fide cardiomyocyte generation is generally low, stem cells delivered into the myocardium act mainly via paracrine mechanisms. More recent studies taking advantage of cardiac committed cells (eg, resident cardiac progenitor cells or primed cardiogenic mesenchymal stem cells) showed promising results in first clinical pilot trials. Also, transplantation of cardiomyogenic cells generated by induced pluripotent stem cells and genetic reprogramming of dividing nonmyocytes into cardiomyocytes may constitute attractive new regenerative approaches in cardiovascular medicine in the future. We discuss advantages and limitations of specific cell types proposed for cell-based therapy in cardiology and give an overview of the first clinical trials using this novel therapeutic approach in patients with cardiovascular disease.

Stat3 and gap junctions in normal and lung cancer cells

Gap junctions are channels linking the interiors of neighboring cells. A reduction in gap junctional intercellular communication (GJIC) correlates with high cell proliferation, while oncogene products such as Src suppress GJIC, through the Ras/Raf/Erk and other effector pathways. High Src activity was found to correlate with high levels of the Src effector, Signal Transducer and Activator of Transcription-3 (Stat3) in its tyrosine-705 phosphorylated, i.e., transcriptionally activated form, in the majority of Non-Small Cell Lung Cancer lines examined. However, Stat3 inhibition did not restore GJIC in lines with high Src activity. In the contrary, Stat3 inhibition in normal cells or in lines with low Src activity and high GJIC eliminated gap junctional communication. Therefore, despite the fact that Stat3 is growth promoting and in an activated form acts like an oncogene, it is actually required for junctional permeability.

Differentiation of human embryonic germ cells and transplantation in rats with acute myocardial infarction

Human embryonic germ cells (hEGCs) are stem cells cultured from primordial germ cells, which reside in human embryonic genital ridges in vivo. In this study, hEGCs were induced to differentiate into cardiomyocytes by treatment with ascorbic acid in vitro and the effects of hEGC transplantation on rat models of acute myocardial infarction (AMI) were investigated. hEGCs were incubated with differentiation medium containing ascorbic acid at various concentrations. Levels of GATA-4 expression were measured to identify the optimal concentration of the inductor. Immunofluorescence microscopy was used to detect the expression of Cx43 on the induced cells. The hEGCs were injected into the myocardium of rats with AMI. The expression levels of MAB1281 and GATA-4 were used to indicate the survival, migration, distribution and differentiation of transplanted cells. The results revealed the positive expression of GATA-4, Cx43 and cardiac troponin T (cTnT) in differentiated cells, and immunocytochemistry showed that transplanted cells highly expressed GATA-4 and MAB1281. hEGCs were successfully induced to differentiate into cardiomyocytes by ascorbic acid in optimal concentrations in vitro and the transplanted hEGCs survived and differentiated into cardiomyocytes.

BMP Signaling in Regenerative Medicine

More than 40 years after the discovery of Bone Morphogenetic Proteins (BMPs) as bone inducers, a whole protein family of growth factors connected to a wide variety of functions in embryonic development, homeostasis, and regeneration has been characterized. Today, BMP2 and BMP7 are already used in the clinic to promote vertebral fusions and restoration of non-union fractures. Besides describing present clinical applications, the authors review ongoing trials highlighting the future possibilities of BMPs in medicine. Apparently, the physiological roles of BMPs have expanded their range from bone growth induction and connective tissue regeneration to cancer diagnosis/treatment and cardiovascular disease prevention.

microRNA-124 regulates cardiomyocyte differentiation of bone marrow-derived mesenchymal stem cells via targeting STAT3 signaling

Accumulating evidence demonstrated that bone marrow-derived mesenchymal stem cells (BMSCs) may transdifferentiate into cardiomyocytes and replace apoptotic myocardium so as to improve functions of damaged hearts. However, little information is known about molecular mechanisms underlying myogenic conversion of BMSCs. microRNAs as endogenous noncoding small molecules function to inhibit protein translation post-transcriptionally by binding to complementary sequences of targeted mRNAs. Here, we reported that miR-124 was remarkably downregulated during cardiomyocyte differentiation of BMSCs induced by coculture with cardiomyocytes. Forced expression of miR-124 led to a significant downregulation of cardiac-specific markers-ANP, TNT, and α-MHC proteins as well as reduction of cardiac potassium channel currents in cocultured BMSCs. On the contrary, the inhibition of endogenous miR-124 with its antisense oligonucleotide AMO-124 obviously reversed the changes of ANP, TNT, and α-MHC proteins and increased cardiac potassium channel currents. Further study revealed that miR-124 targeted the 3'UTR of STAT3 gene so as to suppress the expression of STAT3 protein but did not affect its mRNA level. STAT3 inhibitors AG490, WP1066, and S3I-201 were shown to attenuate the augmented expression of ANP, TNT, α-MHC, GATA-4 proteins, and mRNAs in cocultured BMSCs with AMO-124 transfection. Moreover, GATA-4 siRNA reduced the expression of ANP, TNT, α-MHC, and GATA-4 proteins but did not impact STAT3 protein in cocultured BMSCs, indicating GATA-4 serves as an effector of STAT3. In summary, we found that miR-124 regulated myogenic differentiation of BMSCs via targeting STAT3 mRNA, which provides new insights into molecular mechanisms of cardiomyogenesis of BMSCs.

Stat3 is a positive regulator of gap junctional intercellular communication in cultured, human lung carcinoma cells

Background

Neoplastic transformation of cultured cells by a number of oncogenes such as src suppresses gap junctional, intercellular communication (GJIC); however, the role of Src and its effector Signal transducer and activator of transcription-3 (Stat3) upon GJIC in non small cell lung cancer (NSCLC) has not been defined. Immunohistochemical analysis revealed high Src activity in NSCLC biopsy samples compared to normal tissues. Here we explored the potential effect of Src and Stat3 upon GJIC, by assessing the levels of tyr418-phosphorylated Src and tyr705-phosphorylated Stat3, respectively, in a panel of NSCLC cell lines.

Methods

Gap junctional communication was examined by electroporating the fluorescent dye Lucifer yellow into cells grown on a transparent electrode, followed by observation of the migration of the dye to the adjacent, non-electroporated cells under fluorescence illumination.

Results

An inverse relationship between Src activity levels and GJIC was noted; in five lines with high Src activity GJIC was absent, while two lines with extensive GJIC (QU-DB and SK-LuCi6) had low Src levels, similar to a non-transformed, immortalised lung epithelial cell line. Interestingly, examination of the mechanism indicated that Stat3 inhibition in any of the NSCLC lines expressing high endogenous Src activity levels, or in cells where Src was exogenously transduced, did not restore GJIC. On the contrary, Stat3 downregulation in immortalised lung epithelial cells or in the NSCLC lines displaying extensive GJIC actually suppressed junctional permeability.

Conclusions

Our findings demonstrate that although Stat3 is generally growth promoting and in an activated form it can act as an oncogene, it is actually required for gap junctional communication both in nontransformed lung epithelial cells and in certain lung cancer lines that retain extensive GJIC.

Antiangiogenic role of miR-361 in human umbilical vein endothelial cells: functional interaction with the peptide somatostatin

Somatostatin (SRIF) acts as antiangiogenic factor, but its role in the regulation of microRNAs (miRNAs) targeting proangiogenic factors is unknown. We used human umbilical vein endothelial cells (HUVEC) to investigate whether (1) miRNAs targeting proangiogenic factors are influenced by hypoxia, (2) their expression is regulated by SRIF, and (3) SRIF-regulated miRNAs affect HUVEC angiogenic phenotype. The involvement of signal transducer and activator of transcription (STAT) 3 and hypoxia inducible factor (HIF)-1 in miRNA effects was studied. Quantitative real-time PCR, Western blot, cell proliferation assays, and enzyme-linked immunosorbent assay (ELISA) were used. Using specific algorithms, three miRNAs (miR-17, miR-18b, and miR-361) were predicted to bind angiogenesis-associated factors including STAT3, HIF-1α, and vascular endothelial growth factor (VEGF). Hypoxia downregulates miR-17 and miR-361 without affecting miR-18b. SRIF restored decreased levels of miR-361 acting at the SRIF receptor sst(1). Downregulated miR-361 was also restored by HIF-1α inhibition with YC-1. Combined application of SRIF did not influence YC-1-induced miR-361 downregulation, suggesting that YC-1 and SRIF modulate miR-361 through a common mechanism involving HIF-1α. This possibility was confirmed by the result that HIF-1α activation in normoxia-downregulated miR-361 and that this downregulation was prevented by SRIF. miR-361 overexpression reduced hypoxia-induced cell proliferation and VEGF release indicating miR-361 involvement in the acquisition of an angiogenic phenotype by HUVEC. miR-361 effects on VEGF were enhanced by the coadministration of SRIF. Our results suggest that (1) SRIF regulates miR-361 expression through a control on HIF-1, (2) miR-361 affects HUVEC angiogenic phenotype, and (3) SRIF and miR-361 act cooperatively in limiting hypoxia-induced VEGF release.

MicroRNA-125b/Lin28 pathway contributes to the mesendodermal fate decision of embryonic stem cells

MicroRNAs (miRNAs) are important regulators of cell fate decisions, while the miRNAs and their targets in the regulation of stem cell differentiation are largely unidentified. Here we report novel functions of miR-125b/Lin28 axis in the regulation of mouse embryonic stem cell (mESC) lineage specification and cardiomyocyte differentiation. With a MicroRNA Array screen, we identified a number of miRNAs significantly changed during ESC differentiation, among which miR-125b showed a marked reduction during early differentiation. The abundantly expressed miR-125b in undifferentiated mESCs was dramatically downregulated to a level hardly detected during differentiation day 3 to 5, with a concomitant upregulation of Lin28. Ectopically expressing miR-125b did not alter characteristics of undifferentiated mESCs, whereas it impaired the endoderm and mesoderm development, but not the ectoderm, and inhibited cardiomyocyte formation. We further demonstrate that miR-125b targeted the 3'-untranslated region of Lin28 and reduced the abundance of Lin28 at both mRNA and protein levels. Moreover, phenotypes of miR-125b overexpressing cells were mimicked by downregulation of Lin28 and rescued by reintroduction of Lin28. In addition, the impaired cardiogenesis in miR-125b-introduced cells was greatly recovered when mimicking endoderm environment by cultivation with the condition medium from a visceral endoderm-like cell line, END-2. These results reveal that the miR-125b/Lin28 axis is an important regulator of early lineage specification and cardiomyocyte differentiation of ESCs.

Induction of cell-cycle arrest and apoptosis in glioblastoma stem-like cells by WP1193, a novel small molecule inhibitor of the JAK2/STAT3 pathway

Glioma stem-like cells (GSCs) may be the initiating cells in glioblastoma (GBM) and contribute to the resistance of these tumors to conventional therapies. Development of novel chemotherapeutic agents and treatment approaches against GBM, especially those specifically targeting GSCs are thus necessary. In the present study, we found that a novel Janus kinase 2/Signal Transducer and Activator of Transcription 3 (JAK2/STAT3) pathway inhibitor (WP1193) significantly decreased the proliferation of established glioma cell lines in vitro and inhibit the growth of glioma in vivo. To test the efficacy of WP1193 against GSCs, we then administrated WP1193 to GSCs isolated and expanded from multiple human GBM tumors. We revealed that WP1193 suppressed phosphorylation of JAK2 and STAT3 with high potency and demonstrated a dose-dependent inhibition of proliferation and neurosphere formation of GSCs. These effects were at least due in part to G1 arrest associated with down-regulation of cyclin D1 and up-regulation of p21( Cip1/Waf-1 ). Furthermore, WP1193 exposure decreased expression of stem cell markers including CD133 and c-myc, and induced cell death in GSCs through apoptosis. Taken together, our data indicate that WP1193 is a potent small molecule inhibitor of the JAK2/STAT3 pathway that shows promise as a therapeutic agent against GBM by targeting GSCs.

Induced pluripotent cells in cardiovascular biology: epigenetics, promises, and challenges

Cardiovascular diseases are still the leading cause of death worldwide. Despite the improvement shown in the prognosis of patients with acute MI, there remains still a significant mortality risk. Since the main underlying problem after an MI is the loss of cardiomyocytes and microvasculature, treatment strategies aimed at preserving or regenerating myocardial tissue have been examined as potential therapeutic modalities. Toward this goal, many cell types are being investigated as potent sources of cardiomyocytes for cell transplantation. The progress made toward the generation of induced Pluripotent Stem (iPS) cells hold great potential for future use in myocardial repair. We review critical aspects of these cell's potential, such as their generation, their differentiating ability, the known epigenetic mechanisms that allow for their reprogramming, maintenance of pluripotency, their cardiovascular differentiation and therapeutic potential, and the possibility of an epigenetic memory. Understanding the molecular circuitry of these cells will provide a better understanding of their potential as well as limitations in future clinical use.

Induction of Sca-1 via activation of STAT3 system in the duct cells of the mouse submandibular gland by ligation of the main excretory duct

To examine the very initial step that takes place immediately after tissue injury and is linked to tissue regeneration, we employed the submandibular gland (SMG), which was injured by ligation of its main excretory duct (MED). Ligation of the MED of the SMG in mice induced the expression of Sca-1, a protein marker of hematopoietic stem cells. In the normal gland, a low level of Sca-1 was expressed, which was localized predominantly in the excretory duct cells. At 1 day after ligation, Sca-1 expression increased prominently in almost all of cells in the duct system, but not in the acinar cells. The level of Sca-1 mRNA had begun to increase at 6 h after ligation and continuously rose thereafter until it reached a plateau, which occurred ∼12 h after ligation. STAT3 phosphorylated at its tyrosine-705 (p-STAT3) in the ligated gland increased immediately after ligation, and it was localized in the nuclei of all duct cells. The results of an EMSA revealed the specific binding of a nuclear extract to the sequence of the γ-interferon activation site (GAS) present in the Sca-1 promoter and confirmed that such binding increased after ligation. Thus the present study suggests that STAT3, having been phosphorylated following MED ligation, was transferred to the nucleus, where it bound to the GAS element in the promoter of Sca-1 gene, resulting in promotion of Sca-1 gene expression. Actual prevention of STAT3 phosphorylation reduced the ligation-induced Sca-1 elevation.

Improvement of cardiac function in mouse myocardial infarction after transplantation of epigenetically-modified bone marrow progenitor cells

Objective

To study usefulness of bone marrow progenitor cells (BPCs) epigenetically altered by chromatin modifying agents in mediating heart repair after myocardial infarction in mice.

Methods and Results

We tested the therapeutic efficacy of bone marrow progenitor cells treated with the clinically-used chromatin modifying agents Trichostatin A (TSA, histone deacetylase inhibitor) and 5Aza-2-deoxycytidine (Aza, DNA methylation inhibitor) in a mouse model of acute myocardial infarction (AMI). Treatment of BPCs with Aza and TSA induced expression of pluripotent genes Oct4, Nanog, Sox2, and thereafter culturing these cells in defined cardiac myocyte-conditioned medium resulted in their differentiation into cardiomyocyte progenitors and subsequently into cardiac myocytes. Their transition was deduced by expression of repertoire of markers: Nkx2.5, GATA4, cardiotroponin T, cardiotroponin I, α-sarcomeric actinin, Mef2c and MHC-α. We observed that the modified BPCs had greater AceH3K9 expression and reduced histone deacetylase1 (HDAC1) and lysine-specific demethylase1 (LSD1) expression compared to untreated BPCs, characteristic of epigenetic changes. Intra-myocardial injection of modified BPCs after AMI in mice significantly improved left ventricular function. These changes were ascribed to differentiation of the injected cells into cardiomyocytes and endothelial cells.

Conclusion

Treatment of BPCs with Aza and TSA converts BPCs into multipotent cells, which can then be differentiated into myocyte progenitors. Transplantation of these modified progenitor cells into infarcted mouse hearts improved left ventricular function secondary to differentiation of cells in the niche into myocytes and endothelial cells.

Stem and progenitor cell-based therapy in ischaemic heart disease: promise, uncertainties, and challenges

In the absence of effective endogenous repair mechanisms after cardiac injury, cell-based therapies have rapidly emerged as a potential novel therapeutic approach in ischaemic heart disease. After the initial characterization of putative endothelial progenitor cells and their potential to promote cardiac neovascularization and to attenuate ischaemic injury, a decade of intense research has examined several novel approaches to promote cardiac repair in adult life. A variety of adult stem and progenitor cells from different sources have been examined for their potential to promote cardiac repair and regeneration. Although early, small-scale clinical studies underscored the potential effects of cell-based therapy largely by using bone marrow (BM)-derived cells, subsequent randomized-controlled trials have revealed mixed results that might relate, at least in part, to differences in study design and techniques, e.g. differences in patient population, cell sources and preparation, and endpoint selection. Recent meta-analyses have supported the notion that administration of BM-derived cells may improve cardiac function on top of standard therapy. At this stage, further optimization of cell-based therapy is urgently needed, and finally, large-scale clinical trials are required to eventually proof its clinical efficacy with respect to outcomes, i.e. morbidity and mortality. Despite all promises, pending uncertainties and practical limitations attenuate the therapeutic use of stem/progenitor cells for ischaemic heart disease. To advance the field forward, several important aspects need to be addressed in carefully designed studies: comparative studies may allow to discriminate superior cell populations, timing, dosing, priming of cells, and delivery mode for different applications. In order to predict benefit, influencing factors need to be identified with the aim to focus resources and efforts. Local retention and fate of cells in the therapeutic target zone must be improved. Further understanding of regenerative mechanisms will enable optimization at all levels. In this context, cell priming, bionanotechnology, and tissue engineering are emerging tools and may merge into a combined biological approach of ischaemic tissue repair.

Myocardial injection with GSK-3β-overexpressing bone marrow-derived mesenchymal stem cells attenuates cardiac dysfunction after myocardial infarction

RATIONALE

Glycogen synthase kinase (GSK)-3β upregulates cardiac genes in bone marrow-derived mesenchymal stem cells (MSCs) in vitro. Ex vivo modification of signaling mechanisms in MSCs may improve the efficiency of cardiac cell-based therapy (CBT).

OBJECTIVE

To test the effect of GSK-3β on the efficiency of CBT with MSCs after myocardial infarction (MI).

METHODS AND RESULTS

MSCs overexpressing either GSK-3β (GSK-3β-MSCs), LacZ (LacZ-MSCs), or saline was injected into the heart after coronary ligation. A significant improvement in the mortality and left ventricular (LV) function was observed at 12 weeks in GSK-3β-MSC-injected mice compared with in LacZ-MSC- or saline-injected mice. MI size and LV remodeling were reduced in GSK-3β-MSC-injected mice compared with in LacZ-MSC- or saline-injected ones. GSK-3β increased survival and increased cardiomyocyte differentiation of MSCs, as evidenced by activation of an Nkx2.5-LacZ reporter and upregulation of troponin T. Injection of GSK-3β-MSCs induced Ki67-positive myocytes and c-Kit-positive cells, suggesting that GSK-3β-MSCs upregulate cardiac progenitor cells. GSK-3β-MSCs also increased capillary density and upregulated paracrine factors, including vascular endothelial growth factor A (Vegfa). Injection of GSK-3β-MSCs in which Vegfa had been knocked down abolished the increase in survival and capillary density. However, the decrease in MI size and LV remodeling and the improvement of LV function were still observed in MI mice injected with GSK-3β-MSCs without Vegfa.

CONCLUSIONS

GSK-3β significantly improves the efficiency of CBT with MSCs in the post-MI heart. GSK-3β not only increases survival of MSCs but also induces cardiomyocyte differentiation and angiogenesis through Vegfa-dependent and -independent mechanisms.

Hyaluronan esters drive Smad gene expression and signaling enhancing cardiogenesis in mouse embryonic and human mesenchymal stem cells

Background

Development of molecules chemically modifying the expression of crucial orchestrator(s) of stem cell commitment may have significant biomedical impact. We have recently developed hyaluronan mixed esters of butyric and retinoic acids (HBR), turning cardiovascular stem cell fate into a high-yield process. The HBR mechanism(s) remain still largely undefined.

Methodology/Principal Findings

We show that in both mouse embryonic stem (ES) cells and human mesenchymal stem cells from fetal membranes of term placenta (FMhMSCs), HBR differentially affected the patterning of Smad proteins, one of the major conductors of stem cell cardiogenesis. Real-time RT-PCR and Western blot analyses revealed that in both cell types HBR enhanced gene and protein expression of Smad1,3, and 4, while down-regulating Smad7. HBR acted at the transcriptional level, as shown by nuclear run-off experiments in isolated nuclei. Immunofluorescence analysis indicated that HBR increased the fluorescent staining for Smad1,3, and 4, confirming that the transcriptional action of HBR encompassed the upregulation of the encoded Smad proteins. Chromatin immune precipitation and transcriptional analyses showed that HBR increased the transcription of the cardiogenic gene Nkx-2.5 through Smad4 binding to its own consensus Smad site. Treatment of mouse ES cells and FMhMSCs with HBR led to the concomitant overexpression of both Smad4 and α-sarcomeric actinin. Smad4 silencing by the aid of lentiviral-mediated Smad4 shRNA confirmed a dominant role of Smad4 in HBR-induced cardiogenesis.

Conclusions/Significance

The use of HBR may pave the way to novel combinatorial strategies of molecular and stem cell therapy based on fine tuning of targeted Smad transciption and signaling leading to a high-throughput of cardiogenesis without the needs of gene transfer technologies.

Stat3 is essential for neuronal differentiation through direct transcriptional regulation of the Sox6 gene

The transcription factor Signal Transducer and Activator of Transcription 3 (Stat3) functions in various cellular processes including neuronal differentiation. We show that the SRY-box containing gene 6 (Sox6) gene, important for neuronal differentiation, is a direct target gene of Stat3. We demonstrate that in response to ligand stimulation, Stat3 binds to the Sox6 promoter and induces its expression. Furthermore, Stat3 is activated and Sox6 is induced during neuronal differentiation of P19 cells in the absence of exogenous ligand treatment. Moreover, using an RNA interference approach, we show that Stat3 is required for Sox6 expression during neuronal differentiation.

Mitogen-activated protein kinase signaling in the heart: angels versus demons in a heart-breaking tale

Among the myriad of intracellular signaling networks that govern the cardiac development and pathogenesis, mitogen-activated protein kinases (MAPKs) are prominent players that have been the focus of extensive investigations in the past decades. The four best characterized MAPK subfamilies, ERK1/2, JNK, p38, and ERK5, are the targets of pharmacological and genetic manipulations to uncover their roles in cardiac development, function, and diseases. However, information reported in the literature from these efforts has not yet resulted in a clear view about the roles of specific MAPK pathways in heart. Rather, controversies from contradictive results have led to a perception that MAPKs are ambiguous characters in heart with both protective and detrimental effects. The primary object of this review is to provide a comprehensive overview of the current progress, in an effort to highlight the areas where consensus is established verses the ones where controversy remains. MAPKs in cardiac development, cardiac hypertrophy, ischemia/reperfusion injury, and pathological remodeling are the main focuses of this review as these represent the most critical issues for evaluating MAPKs as viable targets of therapeutic development. The studies presented in this review will help to reveal the major challenges in the field and the limitations of current approaches and point to a critical need in future studies to gain better understanding of the fundamental mechanisms of MAPK function and regulation in the heart.

Stat3 directly controls the expression of Tbx5, Nkx2.5, and GATA4 and is essential for cardiomyocyte differentiation of P19CL6 cells

The transcription factor Stat3 (signal transducer and activator of transcription 3) mediates many physiological processes, including embryogenesis, stem cell self-renewal, and postnatal survival. In response to gp130 receptor activation, Stat3 becomes phosphorylated by the receptor-associated Janus kinase, forms dimers, and enters the nucleus where it binds to Stat3 target genes and regulates their expression. In this report, we demonstrate that Stat3 binds directly to the promoters and regulates the expression of three genes that are essential for cardiac differentiation: Tbx5, Nkx2.5, and GATA4. We further demonstrate that Tbx5, Nkx2.5, and GATA4 expression is dependent on Stat3 in response to ligand treatment and during ligand-independent differentiation of P19CL6 cells into cardiomyocytes. Finally, we show that Stat3 is necessary for the differentiation of P19CL6 cells into beating cardiomyocytes. All together, these results demonstrate that Stat3 is required for the differentiation of cardiomyocytes through direct transcriptional regulation of Tbx5, Nkx2.5, and GATA4.

Enhanced differentiation of human embryonic stem cells to mesenchymal progenitors by inhibition of TGF-beta/activin/nodal signaling using SB-431542

Directing differentiation of human embryonic stem cells (hESCs) into specific cell types using an easy and reproducible protocol is a prerequisite for the clinical use of hESCs in regenerative-medicine procedures. Here, we report a protocol for directing the differentiation of hESCs into mesenchymal progenitor cells. We demonstrate that inhibition of transforming growth factor beta (TGF-beta)/activin/nodal signaling during embryoid body (EB) formation using SB-431542 (SB) in serum-free medium markedly upregulated paraxial mesodermal markers (TBX6, TBX5) and several myogenic developmental markers, including early myogenic transcriptional factors (Myf5, Pax7), as well as myocyte-committed markers [NCAM, CD34, desmin, MHC (fast), alpha-smooth muscle actin, Nkx2.5, cTNT]. Continuous inhibition of TGF-beta signaling in EB outgrowth cultures (SB-OG) enriched for myocyte progenitor cells; markers were PAX7(+) (25%), MYOD1(+) (52%), and NCAM(+) (CD56) (73%). DNA microarray analysis revealed differential upregulation of 117 genes (>2-fold compared with control cells) annotated to myogenic development and function. Moreover, these cells showed the ability to contract (80% of the population) and formed myofibers when implanted intramuscularly in vivo. Interestingly, SB-OG cells cultured in 10% fetal bovine serum (FBS) developed into a homogeneous population of mesenchymal progenitors that expressed CD markers characteristic of mesenchymal stem cells (MSCs): CD44(+) (100%), CD73(+) (98%), CD146(+) (96%), and CD166(+) (88%) with the ability to differentiate into osteoblasts, adipocytes, and chondrocytes in vitro and in vivo. Furthermore, microarray analysis of these cells revealed downregulation of genes related to myogenesis: MYH3 (-167.9-fold), ACTA1 (-161-fold), MYBPH (-139-fold), ACTC (-100.3-fold), MYH8 (-45.5-fold), and MYOT (-41.8-fold) and marked upregulation of genes related to mesoderm-derived cell lineages. In conclusion, our data provides a simple and versatile protocol for directing the differentiation of hESCs into a myogenic lineage and then further into mesenchymal progenitors by blocking the TGF-beta signaling pathway.