Hepatocyte growth factor/Met gene transfer in cardiac stem cells--potential for cardiac repair

Development of the cardioprotective drugs class based on pathophysiology of myocardial infarction: A comprehensive review

The cardiovascular system is mainly responsible for the transport of substances necessary to cellular metabolism. However, for the good performance of this function, there is need for adequate control of blood pressure levels of tissue perfusion and systemic arterial. Acute myocardial infarction is one of the complications of the cardiovascular system, that most affects the population around the world. This condition can be defined as a disease generated by an imbalance of oxygen concentrations used in cardiovascular metabolism, this change usually occurs because coronary occlusion, which prevents myocardial blood flow. The diagnosis is based on the set of clinical and laboratory investigations, which are in the release of cardiac enzyme biomarkers, cardiovascular and hemodynamic changes and cardiac accommodations. The treatment consists in the use of concomitant cardiovascular drugs, such as: antihypertensive, antiplatelet and hypolipidemic. Despite improvements in clinical and pharmacological management, acute myocardial infarction remains the leading cause of death worldwide. This finding encourages the scientific research of new drugs for the treatment of myocardial infarction or supporting therapies aimed at reducing the levels of deaths and comorbities generated by cardiovascular diseases.

Estimating the causal effects of genetically predicted plasma proteome on heart failure

Background

Heart Failure (HF) is the end-stage cardiovascular syndrome with poor prognosis. Proteomics holds great promise in the discovery of novel biomarkers and therapeutic targets for HF. The aim of this study is to investigate the causal effects of genetically predicted plasma proteome on HF using the Mendelian randomization (MR) approach.

Methods

Summary-level data for the plasma proteome (3,301 healthy individuals) and HF (47,309 cases; 930,014 controls) were extracted from genome-wide association studies (GWASs) of European descent. MR associations were obtained using the inverse variance-weighted (IVW) method, sensitivity analyses, and multivariable MR analyses.

Results

Using single-nucleotide polymorphisms as instrumental variables, 1-SD increase in MET level was associated with an approximately 10% decreased risk of HF (odds ratio [OR]: 0.92; 95% confidence interval [CI]: 0.89 to 0.95; p = 1.42 × 10^-6), whereas increases in the levels of CD209 (OR: 1.04; 95% CI: 1.02-1.06; p = 6.67 × 10^-6) and USP25 (OR: 1.06; 95% CI: 1.03-1.08; p = 7.83 × 10^-6) were associated with an increased risk of HF. The causal associations were robust in sensitivity analyses, and no evidence of pleiotropy was observed.

Conclusion

The study findings suggest that the hepatocyte growth factor/c-MET signaling pathway, dendritic cells-mediated immune processes, and ubiquitin-proteasome system pathway are involved in the pathogenesis of HF. Moreover, the identified proteins have potential to uncover novel therapies for cardiovascular diseases.

Comparative proteomic analysis of nuclear and cytoplasmic compartments in human cardiac progenitor cells

Clinical trials evaluating cardiac progenitor cells (CPC) demonstrated feasibility and safety, but no clear functional benefits. Therefore a deeper understanding of CPC biology is warranted to inform strategies capable to enhance their therapeutic potential. Here we have defined, using a label-free proteomic approach, the differential cytoplasmic and nuclear compartments of human CPC (hCPC). Global analysis of cytoplasmic repertoire in hCPC suggested an important hypoxia response capacity and active collagen metabolism. In addition, comparative analysis of the nuclear protein compartment identified a significant regulation of a small number of proteins in hCPC versus human mesenchymal stem cells (hMSC). Two proteins significantly upregulated in the hCPC nuclear compartment, IL1A and IMP3, showed also a parallel increase in mRNA expression in hCPC versus hMSC, and were studied further. IL1A, subjected to an important post-transcriptional regulation, was demonstrated to act as a dual-function cytokine with a plausible role in apoptosis regulation. The knockdown of the mRNA binding protein (IMP3) did not negatively impact hCPC viability, but reduced their proliferation and migration capacity. Analysis of a panel of putative candidate genes identified HMGA2 and PTPRF as IMP3 targets in hCPC. Therefore, they are potentially involved in hCPC proliferation/migration regulation.

An update of the molecular mechanisms underlying doxorubicin plus trastuzumab induced cardiotoxicity

Cardiotoxicity is a major side effect of the chemotherapeutic drug doxorubicin (Dox), which is further exacerbated when it is combined with trastuzumab, a standard care approach for Human Epidermal growth factor Receptor-type 2 (HER2) positive cancer patients. However, the molecular mechanisms of the underlying cardiotoxicity of this combination are still mostly elusive. Increased oxidative stress, impaired energetic substrate uses and topoisomerase IIB inhibition are among the biological processes proposed to explain Dox-induced cardiomyocyte dysfunction. Since cardiomyocytes express HER2, trastuzumab can also damage these cells by interfering with neuroregulin-1 signaling and mitogen-activated protein kinase (MAPK), phosphoinositide 3-kinase (PI3K)/Akt and focal adhesion kinase (FAK)-dependent pathways. Nevertheless, Dox and trastuzumab target other cardiac cell types, such as endothelial cells, fibroblasts, cardiac progenitor cells and leukocytes, which can contribute to the clinical cardiotoxicity observed. This review aims to summarize the current knowledge on the cardiac signaling pathways modulated by these two antineoplastic drugs highly used in the management of breast cancer, not only focusing on cardiomyocytes but also to broaden the knowledge of the potential impact on other cells found in the heart.

Supramolecular Self-Assembled Nanofibers Efficiently Activate the Precursor of Hepatocyte Growth Factor for Angiogenesis in Myocardial Infarction Therapy

The reconstruction of blood perfusion is a crucial therapeutic method to save and protect cardiac function after acute myocardial infarction (AMI). The activation of the hepatocyte growth factor precursor (pro-HGF) has a significant effect on promoting angiogenesis and antiapoptosis. The oxygen/glucose deprivation (OGD) caused by AMI could induce vascular adventitia fibroblasts to differentiate into myofibroblasts and secrete the pro-HGF. Meanwhile, the specific Met receptor of the hepatocyte growth factor (HGF) is upregulated in endothelial cells during AMI. However, the poor prognosis of AMI suggests that the pro-HGF is not effectively activated. Improving the activation efficiency of the pro-HGF may play a positive role in the treatment of AMI. Herein, we designed supramolecular nanofibers self-assembled by compound 1 (Comp.1, Nap-FFEG-IVGGYPWWMDV), which can strongly activate the pro-HGF and initiate HGF-Met signaling. Studies have proven that Comp.1 possesses a better ability to activate the pro-HGF to perform antiapoptosis and pro-angiogenesis. In vivo results have confirmed that the retention time of Comp.1 and its accumulation in the infarct area of the heart are promoted. Moreover, Comp.1 plays an effective role in promoting angiogenesis in the marginal area of AMI, reducing myocardial fibrosis, and protecting cardiac function. Herein, we will optimize the structure of bioactive peptides through supramolecular self-assembly and amplify their therapeutic effect by improving their efficiency, providing a new strategy for the therapy of AMI.

Characterization of encapsulated porcine cardiosphere-derived cells embedded in 3D alginate matrices

Myocardial infarction is caused by an interruption of coronary blood flow, leading to one of the main death causes worldwide. Current therapeutic approaches are palliative and not able to solve the loss of cardiac tissue. Cardiosphere derived cells (CDCs) reduce scarring, and increase viable myocardium, with safety and adequate biodistribution, but show a low rate engraftment and survival after implantation. In order to solve the low retention, we propose the encapsulation of CDCs within three-dimensional alginate-poly-L-lysine-alginate matrix as therapy for cardiac regeneration. In this work, we demonstrate the encapsulation of CDCs in alginate matrix, with no decrease in viability over a month, and showing the preservation of CDCs phenotype, differentiation potential, gene expression profile and growth factor release after encapsulation, moving a step forward to clinical translation of CDCs therapy in regeneration in heart failure.

Transplantation of telomerase/myocardin-co-expressing mesenchymal cells in the mouse promotes myocardial revascularization and tissue repair

AIM

Cell therapies are hampered by poor survival and growth of grafts. We tested whether forced co-expression of telomerase reverse transcriptase (TERT) and myocardin (MYOCD) improves post-infarct revascularization and tissue repair by adipose tissue-derived mesenchymal stromal cells (AT-MSCs).

METHODS AND RESULTS

We transplanted AT-MSCs overexpressing MYOCD and TERT in a murine model of acute myocardial infarction (AMI). We characterized paracrine effects of AT-MSCs. When transplanted into infarcted hearts of C57BL/6 mice, AT-MSCs overexpressing TERT and MYOCD decreased scar tissue and the intra-scar CD3 and B220 lymphocyte infiltration; and increased arteriolar density as well as ejection fraction compared with saline or mock-transduced AT-MSCs. These effects were accompanied by higher persistence of the injected cells in the heart, increased numbers of Ki-67⁺ and CD117⁺ cells, and the expression of cardiac actin and β-myosin heavy chain. Intramyocardial delivery of the secretome and its extracellular vesicle (EV)-enriched fraction also decreased scar tissue formation and increased arteriolar density in the murine AMI model. Proteomic analysis of AT-MSCs-EV-enriched fraction predicted the activation of vascular development and the inhibition of immune cell trafficking. Elevated concentrations of miR-320a, miR-150-5p and miR-126-3p associated with regulation of apoptosis and vasculogenesis were confirmed in the AT-MSCs-EV-enriched fraction.

CONCLUSIONS

AT-MSCs overexpressing TERT and MYOCD promote persistence of transplanted aged AT-MSCs and enhance arteriolar density in a murine model of AMI. EV-enriched fraction is the component of the paracrine secretion by AT-MSCs with pro-angiogenic and anti-fibrotic activities.

Genetic Engineering as a Strategy to Improve the Therapeutic Efficacy of Mesenchymal Stem/Stromal Cells in Regenerative Medicine

Mesenchymal stem/stromal cells (MSCs) have been widely studied in the field of regenerative medicine for applications in the treatment of several disease settings. The therapeutic potential of MSCs has been evaluated in studies in vitro and in vivo, especially based on their anti-inflammatory and pro-regenerative action, through the secretion of soluble mediators. In many cases, however, insufficient engraftment and limited beneficial effects of MSCs indicate the need of approaches to enhance their survival, migration and therapeutic potential. Genetic engineering emerges as a means to induce the expression of different proteins and soluble factors with a wide range of applications, such as growth factors, cytokines, chemokines, transcription factors, enzymes and microRNAs. Distinct strategies have been applied to induce genetic modifications with the goal to enhance the potential of MCSs. This review aims to contribute to the update of the different genetically engineered tools employed for MSCs modification, as well as the factors investigated in different fields in which genetically engineered MSCs have been tested.

Hepatocyte growth factor: Molecular biomarker and player in cardioprotection and cardiovascular regeneration

The liver possesses impressive regenerative capacities. Grafts of embryonic liver explants and liver explant-conditioned media have been shown to enhance the mitotic activity of hepatocytes. Hepatocyte growth factor (HGF), also named scatter factor (SF), has been identified as a primary candidate in promoting and regulating liver regeneration. Although initially thought to be a liver-specific mitogen, HGF was later reported to have mitogenic, motogenic, morphogenic, and anti-apoptotic activities in various cell types. By promoting angiogenesis and inhibiting apoptosis, endogenous HGF may play an important role in cardioprotection as well as in the regeneration of endothelial cells and cardiomyocytes after myocardial infarction. Since serum concentration of HGF increases in the early phase of myocardial infarction and in heart failure, HGF may also play a key role as a prognostic and diagnostic biomarker of cardiovascular disease. Here we discuss the role of HGF as a biomarker and mediator in cardioprotection and cardiovascular regeneration.

bFGF promotes Sca‑1+ cardiac stem cell migration through activation of the PI3K/Akt pathway

Cardiac stem cells (CSCs) are important for improving cardiac function following myocardial infarction, with CSC migration to infarcted or ischemic myocardium important for cardiac regeneration. Strategies to improve cell migration may improve the efficiency of myocardial regeneration. Basic fibroblast growth factor (bFGF) is an essential molecule in cell migration, but the endogenous bFGF level is too low to be effective. The effect of exogenously delivered bFGF on CSC migration was observed in vitro and in vivo in the present study. The CSC migration index in response to various bFGF concentrations was demonstrated in vitro. In addition, a murine myocardial infarction model was constructed and bFGF protein expression levels and CSC aggregation following myocardial infarction were observed. To study cell migration in vivo, CM-Dil-labeled CSCs or bFGF-CSCs were injected into the peri-infarct myocardium following myocardium infarction and cell migration and maintenance in the peri-infarct/infarct area was observed 1 week later. Protein expression levels of bFGF, CXCR-4 and SDF-1 were assessed, as was myocardium capillary density. The Akt inhibitor deguelin was used to assess the role of the PI3K/Akt pathway in vitro and in vivo. The present study demonstrated that bFGF-promoted Sca-1⁺ CSC migration, with the highest migration rate occurring at a concentration of 45 ng/ml. The PI3K/Akt pathway inhibitor deguelin attenuated this increase. The phospho-Akt/Akt ratio was elevated significantly after 30 min of bFGF exposure. Transplantation of bFGF-treated Sca-1⁺ CSCs led to improved cell maintenance in the peri-infarct area and increased cell migration to the infarct area, as well as improved angiogenesis. Protein expression levels of bFGF, CXCR-4 and SDF-1 were upregulated, and this upregulation was partially attenuated by deguelin. Therefore, bFGF was demonstrated to promote Sca-1⁺ CSC migration both in vitro and in vivo, partially through activation of the PI3K/Akt pathway. This may provide a new method for facilitating CSC therapy for myocardium repair after myocardium injury.

Treatment of Myocardial Infarction with Gene-modified Mesenchymal Stem Cells in a Small Molecular Hydrogel

The effect of transplanted rat mesenchymal stem cells (MSCs) can be reduced by extracellular microenvironment in myocardial infarction (MI). We tested a novel small-molecular hydrogel (SMH) on whether it could provide a scaffold for hepatocyte growth factor (HGF)-modified MSCs and alleviate ventricular remodeling while preserving cardiac function after MI. Overexpression of HGF in MSCs increased Bcl-2 and reduced Bax and caspase-3 levels in response to hypoxia in vitro. Immunocytochemistry demonstrated that cardiac troponin (cTnT), desmin and connexin 43 expression were significantly enhanced in the 5-azacytidine (5-aza) with SMH group compared with the 5-aza only group in vitro and in vivo. Bioluminescent imaging indicated that retention and survival of transplanted cells was highest when MSCs transfected with adenovirus (ad-HGF) were injected with SMH. Heart function and structure improvement were confirmed by echocardiography and histology in the Ad-HGF-SMHs-MSCs group compared to other groups. Our study showed that: HGF alleviated cell apoptosis and promoted MSC growth. SMHs improved stem cell adhesion, survival and myocardial cell differentiation after MSC transplantation. SMHs combined with modified MSCs significantly decreased the scar area and improved cardiac function.

A collagen cardiac patch incorporating alginate microparticles permits the controlled release of hepatocyte growth factor and insulin-like growth factor-1 to enhance cardiac stem cell migration and proliferation

Cardiac stem cells (CSCs) represent a logical cell type to exploit as a regenerative treatment option for tissue damage accrued as a result of a myocardial infarction. However, the isolation and expansion of CSCs prior to cell transplantation is time consuming, costly and invasive, and the reliability of cell expansion may also prove to be a major obstacle in the clinical application of CSC-based transplantation therapy after a myocardial infarction. In order to overcome this, we propose the incorporation of growth factor-eluting alginate microparticles into collagen-based scaffolds as an implantable biomaterial to promote the recruitment and expansion of CSCs in the myocardium. In order to obtain scaffolds able to enhance the motogenic and proliferative potential of CSCs, the aim of this work was to achieve a sustained delivery of both hepatocyte growth factor and insulin-like growth factor-1. Both proteins were initially encapsulated in alginate microparticles by spray drying and subsequently incorporated into a collagen scaffold. Microparticles were seen to homogeneously distribute through the interconnected scaffold pore structure. The resulting scaffolds were capable of extending the release of both proteins up to 15 days, a three-fold increase over non-encapsulated proteins embedded in the scaffolds. In vitro assays with isolated CSCs demonstrated that the sustained release of both bioactive proteins resulted in an increased motogenic and proliferative effect. As presently practiced, the isolation and expansion of CSCs for autologous cell transplantation is slow, expensive and difficult to attain. Thus, there is a need for strategies to specifically activate in situ the intrinsic cardiac regenerative potential represented by the CSCs using combinations of growth factors obviating the need for cell transplantation. By favouring the natural regenerative capability of CSCs, it is hypothesized that the cardiac patch presented here will result in positive therapeutic outcomes in MI and heart failure patients in the future. Copyright © 2016 John Wiley & Sons, Ltd.

Improving the preclinical models for the study of chemotherapy-induced cardiotoxicity: a Position Paper of the Italian Working Group on Drug Cardiotoxicity and Cardioprotection

Although treatment for heart failure induced by cancer therapy has improved in recent years, the prevalence of cardiomyopathy due to antineoplastic therapy remains significant worldwide. In addition to traditional mediators of myocardial damage, such as reactive oxygen species, new pathways and target cells should be considered responsible for the impairment of cardiac function during anticancer treatment. Accordingly, there is a need to develop novel therapeutic strategies to protect the heart from pharmacologic injury, and improve clinical outcomes in cancer patients. The development of novel protective therapies requires testing putative therapeutic strategies in appropriate animal models of chemotherapy-induced cardiomyopathy. This Position Paper of the Working Group on Drug Cardiotoxicity and Cardioprotection of the Italian Society of Cardiology aims to: (1) define the distinctive etiopatogenetic features of cardiac toxicity induced by cancer therapy in humans, which include new aspects of mitochondrial function and oxidative stress, neuregulin-1 modulation through the ErbB receptor family, angiogenesis inhibition, and cardiac stem cell depletion and/or dysfunction; (2) review the new, more promising therapeutic strategies for cardioprotection, aimed to increase the survival of patients with severe antineoplastic-induced cardiotoxicity; (3) recommend the distinctive pathological features of cardiotoxicity induced by cancer therapy in humans that should be present in animal models used to identify or to test new cardioprotective therapies.

Novel insights in pathophysiology of antiblastic drugs-induced cardiotoxicity and cardioprotection

Despite advances in supportive and protective therapy for myocardial function, heart failure caused by various clinical conditions, including cardiomyopathy due to antineoplastic therapy, remains a major cause of morbidity and mortality. Because of the limitations associated with current therapies, investigators have been searching for alternative treatments that can effectively repair the damaged heart and permanently restore its function. Damage to the heart can result from both traditional chemotherapeutic agents, such as anthracyclines, and new targeted therapies, such as trastuzumab. Because of this unresolved issue, investigators are searching for alternative therapeutic strategies. In this article, we present state-of-the-art technology with regard to the genomic and epigenetic mechanisms underlying cardiotoxicity and cardioprotection, the role of anticancer in influencing the redox (reduction/oxidation) balance and the function of stem cells in the repair/regeneration of the adult heart. These findings, although not immediately transferable to clinical applications, form the basis for the development of personalized medicine based on the prevention of cardiotoxicity with the use of genetic testing. Proteomics, metabolomics and investigations on reactive oxygen species-dependent pathways, particularly those that interact with the production of NO and energy metabolism, appear to be promising for the identification of early markers of cardiotoxicity and for the development of cardioprotective agents. Finally, autologous cardiac stem and progenitor cells may represent future contributions in the field of myocardial protection and recovery in the context of antiblastic therapy.

Cardiac concentric hypertrophy promoted by activated Met receptor is mitigated in vivo by inhibition of Erk1,2 signalling with Pimasertib

Cardiac hypertrophy is a major risk factor for heart failure. Hence, its attenuation represents an important clinical goal. Erk1,2 signalling is pivotal in the cardiac response to stress, suggesting that its inhibition may be a good strategy to revert heart hypertrophy. In this work, we unveiled the events associated with cardiac hypertrophy by means of a transgenic model expressing activated Met receptor. c-Met proto-oncogene encodes for the tyrosine kinase receptor of Hepatocyte growth factor and is a strong inducer of Ras-Raf-Mek-Erk1,2 pathway. We showed that three weeks after the induction of activated Met, the heart presents a remarkable concentric hypertrophy, with no signs of congestive failure and preserved contractility. Cardiac enlargement is accompanied by upregulation of growth-regulating transcription factors, natriuretic peptides, cytoskeletal proteins, and Extracellular Matrix remodelling factors (Timp1 and Pai1). At a later stage, cardiac hypertrophic remodelling results into heart failure with preserved systolic function. Prevention trial by suppressing activated Met showed that cardiac hypertrophy is reversible, and progression to heart failure is prevented. Notably, treatment with Pimasertib, Mek1 inhibitor, attenuates cardiac hypertrophy and remodelling. Our results suggest that modulation of Erk1.2 signalling may constitute a new therapeutic approach for treating cardiac hypertrophies.

Mesenchymal stem/stromal cells as a delivery platform in cell and gene therapies

Regenerative medicine relying on cell and gene therapies is one of the most promising approaches to repair tissues. Multipotent mesenchymal stem/stromal cells (MSC), a population of progenitors committing into mesoderm lineages, are progressively demonstrating therapeutic capabilities far beyond their differentiation capacities. The mechanisms by which MSC exert these actions include the release of biomolecules with anti-inflammatory, immunomodulating, anti-fibrogenic, and trophic functions. While we expect the spectra of these molecules with a therapeutic profile to progressively expand, several human pathological conditions have begun to benefit from these biomolecule-delivering properties. In addition, MSC have also been proposed to vehicle genes capable of further empowering these functions. This review deals with the therapeutic properties of MSC, focusing on their ability to secrete naturally produced or gene-induced factors that can be used in the treatment of kidney, lung, heart, liver, pancreas, nervous system, and skeletal diseases. We specifically focus on the different modalities by which MSC can exert these functions. We aim to provide an updated understanding of these paracrine mechanisms as a prerequisite to broadening the therapeutic potential and clinical impact of MSC.

Transplantation of adipose tissue mesenchymal cells conjugated with VEGF-releasing microcarriers promotes repair in murine myocardial infarction

RATIONALE

Engraftment and survival of transplanted stem or stromal cells in the microenvironment of host tissues may be improved by combining such cells with scaffolds to delay apoptosis and enhance regenerative properties.

AIMS

We examined whether poly(lactic-co-glycolic acid) pharmacologically active microcarriers (PAMs) releasing vascular endothelial growth factor (VEGF) enhance survival, differentiation, and angiogenesis of adipose tissue-mesenchymal stromal cells (AT-MSCs). We analysed the efficacy of transplanted AT-MSCs conjugated with PAMs in a murine model of acute myocardial infarction (AMI).

METHODS AND RESULTS

We used fibronectin-coated (empty) PAMs or VEGF-releasing PAMs covered with murine AT-MSCs. Twelve-month-old C57 mice underwent coronary artery ligation to induce AMI, and were randomized into five treatment groups: AMI control (saline 20 µL, n = 7), AMI followed by intramyocardial injection with AT-MSCs (2.5 × 10(5) cells/20 µL, n = 5), or concentrated medium (CM) from AT-MSCs (20 µL, n = 8), or AT-MSCs (2.5 × 10(5) cells/20 µL) conjugated with empty PAMs (n = 7), or VEGF-releasing PAMs (n = 8). Sham-operated mice (n = 7) were used as controls. VEGF-releasing PAMs increased proliferation and angiogenic potential of AT-MSCs, but did not impact their osteogenic or adipogenic differentiation. AT-MSCs conjugated with VEGF-releasing PAMs inhibited apoptosis, decreased fibrosis, increased arteriogenesis and the number of cardiac-resident Ki-67 positive cells, and improved myocardial fractional shortening compared with AT-MSCs alone when transplanted into the infarcted hearts of C57 mice. With the exception of fractional shortening, all such effects of AT-MSCs conjugated with VEGF-PAMs were paralleled by the injection of CM.

CONCLUSIONS

AT-MSCs conjugated with VEGF-releasing PAMs exert paracrine effects that may have therapeutic applications.

HGF expression induced by HIF-1α promote the proliferation and tube formation of endothelial progenitor cells

Hypoxia-inducible factor-1α (HIF-1α) and hepatocyte growth factor (HGF) play important roles in postnatal neovascularization. However, the interaction of these two pathways is not fully understood. The present study utilized CoCl(2) treated-endothelial progenitor cells (EPCs) (EPCs exposure to CoCl(2) are under mimic hypoxia) to examine the expressions of HIF-1α and HGF and futher to assess whether or not the inhibitor (2-methoxyestradiol [2ME2]) of HIF-1α decrease the HGF expression. In addition, to investigate the effects of HGF on the proliferation and tube formation of EPCs under mimic hypoxia, EPCs were transfected with NK4 (HGF antagonist) plasmid and exposed to CoCl(2), then the proliferation of these EPCs was assayed by MTS and the tube formation capacity of these EPCs on Matrigel was detected. The analysis indicated that CoCl(2) treatment induced HIF-1α expression of EPCs, and futher promoted HGF expression. While after 2ME2 was used in CoCl(2) treated-EPCs, HGF expression was markedly inhibited compared with non-pretreated EPCs with 2ME2, which also showed that HGF expression in EPCs was mediated by HIF-1α. Further, the results showed that after EPCs were transfected with NK4 in spite of being exposed to CoCl(2), their proliferation activity and tube formation capacity were weakened, which in turn indicated that HGF could promote the proliferation and the tube formation of EPCs, and this process might be regulated by HIF-1α.

Hepatocyte Growth Factor Isoforms in Tissue Repair, Cancer, and Fibrotic Remodeling

Hepatocyte growth factor (HGF), also known as scatter factor (SF), is a pleotropic factor required for normal organ development during embryogenesis. In the adult, basal expression of HGF maintains tissue homeostasis and is up-regulated in response to tissue injury. HGF expression is necessary for the proliferation, migration, and survival of epithelial and endothelial cells involved in tissue repair in a variety of organs, including heart, lung, kidney, liver, brain, and skin. The administration of full length HGF, either as a protein or using exogenous expression methodologies, increases tissue repair in animal models of tissue injury and increases angiogenesis. Full length HGF is comprised of an N-terminal hairpin turn, four kringle domains, and a serine protease-like domain. Several naturally occurring alternatively spliced isoforms of HGF were also identified. The NK1 variant contains the N-terminal hairpin and the first kringle domain, and the NK2 variant extends through the second kringle domain. These alternatively spliced forms of HGF activate the same receptor, MET, but they differ from the full length protein in their cellular activities and their biological functions. Here, we review the species-specific expression of the HGF isoforms, their regulation, the signal transduction pathways they activate, and their biological activities.

Novel therapeutic strategies for cardioprotection

The morbidity and mortality from ischemic heart disease (IHD) remain significant worldwide. The treatment for acute myocardial infarction has improved over the past decades, including early reperfusion of occluded coronary arteries. Although it is essential to re-open the artery as soon as possible, paradoxically this leads to additional myocardial injury, called acute ischemia-reperfusion injury (IRI), for which currently no effective therapy is available. Therefore, novel therapeutic strategies are required to protect the heart from acute IRI in order to reduce myocardial infarction size, preserve cardiac function and improve clinical outcomes in patients with IHD. In this review article, we will first outline the pathophysiology of acute IRI and review promising therapeutic strategies for cardioprotection. These include novel aspects of mitochondrial function, epigenetics, circadian clocks, the immune system, microvesicles, growth factors, stem cell therapy and gene therapy. We discuss the therapeutic potential of these novel cardioprotective strategies in terms of pharmacological targeting and clinical application.

Spatially oriented, temporally sequential smooth muscle cell-endothelial progenitor cell bi-level cell sheet neovascularizes ischemic myocardium

BACKGROUND

Endothelial progenitor cells (EPCs) possess robust therapeutic angiogenic potential, yet may be limited in the capacity to develop into fully mature vasculature. This problem might be exacerbated by the absence of a neovascular foundation, namely pericytes, with simple EPC injection. We hypothesized that coculturing EPCs with smooth muscle cells (SMCs), components of the surrounding vascular wall, in a cell sheet will mimic the native spatial orientation and interaction between EPCs and SMCs to create a supratherapeutic angiogenic construct in a model of ischemic cardiomyopathy.

METHODS AND RESULTS

Primary EPCs and SMCs were isolated from Wistar rats. Confluent SMCs topped with confluent EPCs were spontaneously detached from the Upcell dish to create an SMC-EPC bi-level cell sheet. A rodent ischemic cardiomyopathy model was created by ligating the left anterior descending coronary artery. Rats were then immediately divided into 3 groups: cell-sheet transplantation (n=14), cell injection (n=12), and no treatment (n=13). Cocultured EPCs and SMCs stimulated an abundant release of multiple cytokines in vitro. Increased capillary density and improved blood perfusion in the borderzone elucidated the significant in vivo angiogenic potential of this technology. Most interestingly, however, cell fate-tracking experiments demonstrated that the cell-sheet EPCs and SMCs directly migrated into the myocardium and differentiated into elements of newly formed functional vasculature. The robust angiogenic effect of this cell sheet translated to enhanced ventricular function as demonstrated by echocardiography.

CONCLUSIONS

Spatially arranged EPC-SMC bi-level cell-sheet technology facilitated the natural interaction between EPCs and SMCs, thereby creating structurally mature, functional microvasculature in a rodent ischemic cardiomyopathy model, leading to improved myocardial function.

Therapeutic potential of genes in cardiac repair

Cardiovascular diseases remain the primary reason of premature death and contribute to a major percentage of global patient morbidity. Recent knowledge in the molecular mechanisms of myocardial complications have identified novel therapeutic targets along with the availability of vectors that offer the chance for designing gene therapy technique for protection and revival of the diseased heart functions. Gene transfer procedure into the myocardium is demonstrated through direct injection of plasmid DNA or through the coronary vasculature using the direct or indirect delivery of viral vectors. Direct DNA injection to the myocardium is reported to be of immense value in research studies that aims at understanding the activities of various elements in myocardium. It is also deemed vital for investigating the effect of the myocardial pathophysiology on expression of the foreign genes that are transferred. Gene therapies have been reported to heal cardiac pathologies such as myocardial ischemia, heart failure and inherited myopathies in several animal models. The results obtained from these animal studies have also encouraged a flurry of early clinical trials. This translational research has been triggered by an enhanced understanding of the biological mechanisms involved in tissue repair after ischemic injury. While safety concerns take utmost priority in these trials, several combinational therapies, various routes and dose of delivery are being tested before concrete optimization and complete potential of gene therapy is convincingly understood.

Cardiac progenitors derived from reprogrammed mesenchymal stem cells contribute to angiomyogenic repair of the infarcted heart

The strategy to reprogram somatic stem cells to pluripotency status has provided an alternative source of surrogate ES cells (ESC). We report efficient reprogramming of multipotent bone marrow (BM) mesenchymal stem cells (MSC) to pluripotent status and the resultant MSC derived iPS cells (MiPS) and their derived progenitors effectively repaired the infarcted heart. MSC from young, male, Oct4-GFP transgenic mice were reprogrammed by retroviral transduction with Oct4, Sox2, Klf4, and c-Myc stemness factors. MiPS thus generated displayed characteristics of mouse ESC including morphology, surface antigens, gene and miR expression profiles. MiPS also formed spontaneously beating cardiac progenitors which expressed cardiac specific transcription factors and protein markers including Gata4, Mef2c, Nkx2.5, myosin heavy chain, troponin-I, and troponin-T, and showed ultra structural characteristics typical of cardiomyocytes. Intramyocardial delivery of MiPS (group-2) and their derivative cardiac-like cells (MiPS-CP; group-3) in a mouse model of acute myocardial infarction showed extensive survival and engraftment at 4 weeks with resultant attenuation of infarct size (p < 0.001 vs. DMEM injected control; n = 4). Engraftment of MiPS-CP was without cardiac tumorigenesis as compared to 21 % in MiPS transplanted animals. Furthermore, angiogenesis was improved in groups-2 and 3 (p < 0.001 vs. control). Transthoracic echocardiography revealed significantly preserved indices of cardiac contractility (ejection fraction p < 0.001 and fractional shortening p < 0.001 vs. control; n = 7). MSC were successfully reprogrammed into MiPS that displayed ESC-like characteristics and differentiated into spontaneously beating cardiomyocytes. Cardiac progenitors derived from MiPS repopulated the infarcted heart without tumorigenesis and improved global cardiac function.

Activation of diverse signaling pathways by ex-vivo delivery of multiple cytokines for myocardial repair

We tested the hypothesis that simultaneous transgenic overexpression of a select quartet of growth factors activates diverse signaling pathways for mobilization and participation of various stem/progenitor cells for cardiogenesis in the infarcted heart. Human insulin growth factor-1 (IGF-1), vascular endothelial growth factor (VEGF), stromal cell-derived factor-1 (SDF-1a), and hepatocyte growth factor (HGF) plasmids were synthesized and transfected into skeletal myoblasts (SM) from young male wild-type or transgenic rats expressing green fluorescent protein (GFP). Overexpression of growth factors in transfected SM ((Trans)SM) was confirmed by reverse transcription polymerase chain reaction, western blotting, and fluorescence immunostaining. Using our custom-made growth factor array and western blotting, multiple angiogenic and prosurvival factors were detected in (Trans)SM, including secreted frizzled related protein-1,2,4,5, matrix metalloproteinases-3 and 9, connexin-43, netrin-1, Nos-2, Wnt-3, Akt, MAPK42/44, Stat3, nuclear factor kappa B (NFκB), hypoxia-inducible factor 1 (HIF-1α), and protein kinase C (PKC). The conditioned medium (CM) from (Trans)SM was cytoprotective for cardiomyocytes following H(2)O(2) treatment [P<0.01 vs. CM from native SM ((Nat)SM)], promoted a higher transwell migration of human umbilical cord vein endothelial cells (223.3±1.8, P<0.01) and in vitro tube formation (47.8±1.9, P<0.01). Intramyocardial transplantation of 1.5×10(6) (Trans)SM (group-3) in a rat model of acute myocardial infarction induced extensive mobilization of cMet(+), ckit(+), ckit(+)/GATA(4+), CXCR4(+), CD44(+), CD31(+), and CD59(+) cells into the infarcted heart on day 7 and improved integration of (Trans)SM in the heart compared to (Nat)SM (group 2) (P<0.05). Extensive neomyogenesis and angiogenesis in group-3 (P<0.01 vs. group-2), with resultant attenuation of infarct size (P<0.01 vs. group-2) and improvement in global heart function (P<0.01 vs. group-2) was observed at 8 weeks. In conclusion, simultaneous activation of diverse signaling pathways by overexpression of multiple growth factors caused massive mobilization and homing of stem/progenitor cells from peripheral circulation, the bone marrow, and the heart for accelerated repair of the infarcted myocardium.

MSCs transfected with hepatocyte growth factor or vascular endothelial growth factor improve cardiac function in the infarcted porcine heart by increasing angiogenesis and reducing fibrosis

BACKGROUND

Cell transplantation and gene therapy have been demonstrated to have beneficial effects after a myocardial infarction (MI). Here, we used a large animal model of MI to investigate the beneficial effects of mesenchymal stem cells (MSCs) transfected with hepatocyte growth factor (HGF) or vascular endothelial growth factor (VEGF) genes.

METHODS

A porcine MI model was created by balloon occlusion of the distal left anterior descending artery for 90 min followed by reperfusion. At 1 week after MI, the pigs were infused via the coronary vein with saline (n=8), MSCs + AdNull(n=8), MSC+VEGF(n=10), or MSC+HGF(n=10). Cardiac function and myocardial perfusion were evaluated by using echocardiography and gated cardiac perfusion imaging before and 4 weeks after transplantation. Morphometric and histological analyses were performed.

RESULTS

All cell-implanted groups had better cardiac function than the saline control group. There were further functional improvements in the MSC+HGF group, accompanied by smaller infarct sizes, increased cell survival, and less collagen deposition. Blood vessel densities in the damaged area and cardiac perfusion were significantly greater in the MSC+AdNull group than in the saline control group, and further increased in the MSC+VEGF/HGF groups. Tissue fibrosis was significantly less extensive in the MSC and MSC+VEGF groups than in the saline control group and was most reduced in the MSC+HGF group.

CONCLUSION

MSCs (alone or transfected with VEGF/HGF) delivered into the infarcted porcine heart via the coronary vein improved cardiac function and perfusion, probably by increasing angiogenesis and reducing fibrosis. MSC+HGF was superior to MSC+VEGF, possibly owing to its enhanced antifibrotic effect.

Secretome of apoptotic peripheral blood cells (APOSEC) attenuates microvascular obstruction in a porcine closed chest reperfused acute myocardial infarction model: role of platelet aggregation and vasodilation

Although epicardial blood flow can be restored by an early intervention in most cases, a lack of adequate reperfusion at the microvascular level is often a limiting prognostic factor of acute myocardial infarction (AMI). Our group has recently found that paracrine factors secreted from apoptotic peripheral blood mononuclear cells (APOSEC) attenuate the extent of myocardial injury. The aim of this study was to determine the influence of APOSEC on microvascular obstruction (MVO) in a porcine AMI model. A single dose of APOSEC was intravenously injected in a closed chest reperfused infarction model. MVO was determined by magnetic resonance imaging and cardiac catheterization. Role of platelet function and vasodilation were monitored by means of ELISA, flow cytometry, aggregometry, western blot and myographic experiments in vitro and in vivo. Treatment of AMI with APOSEC resulted in a significant reduction of MVO. Platelet activation markers were reduced in plasma samples obtained during AMI, suggesting an anti-aggregatory capacity of APOSEC. This finding was confirmed by in vitro tests showing that activation and aggregation of both porcine and human platelets were significantly impaired by co-incubation with APOSEC, paralleled by vasodilator-stimulated phosphoprotein (VASP)-mediated inhibition of platelets. In addition, APOSEC evidenced a significant vasodilatory capacity on coronary arteries via p-eNOS and iNOS activation. Our data give first evidence that APOSEC reduces the extent of MVO during AMI, and suggest that modulation of platelet activation and vasodilation in the initial phase after myocardial infarction contributes to the improved long-term outcome in APOSEC treated animals.

Mesenchymal stem cells neither fully acquire the electrophysiological properties of mature cardiomyocytes nor promote ventricular arrhythmias in infarcted rats

Electrophysiological properties of implanted mesenchymal stem cells (MSCs) in infarcted hearts remain unclear, and their proarrhythmic effect is still controversial. The intent of this study was to investigate electrophysiological properties and proarrhythmic effects of MSCs in infarcted hearts. Rats were randomly divided into a myocardial infarction (MI) group, a MI-DMEM group (received DMEM medium injection) and MI-MSCs group (received MSCs injection). Survival analysis showed that the majority of engrafted MSCs died at day 9 after transplantation. Engrafted MSCs expressed cardiac markers (MYH, cTnI, Cx43), cardiac ion channel genes (Kv1.4, Kv4.2 and Kir2.1) and potassium currents (I (to), I (K1) and I (KDR)), but did not express Nav1.5, Cav1.2, Na(+) current and Ca(2+) current during their survival. When induced by Ca(2+), implanted MSCs exhibited no contraction ability after being isolated from the heart. Following 8-week electrocardiography monitoring, the cumulative occurrence of ventricular arrhythmias (VAs) was not different among the three groups. However, the prolonged QRS duration in infarcted rats without VAs was significantly decreased in the MI-MSCs group compared with the other two groups. The inducibility of VAs in the MI-MSCs group was much lower than that in the MI and MI-DMEM groups (41.20 vs. 86.67 % and 92.86 %; P < 0.0125). The ventricular effective refractory period in MI-MSCs group was prolonged in comparison with that in the MI and MI-DMEM groups (56.0 ± 8.8 vs. 47.7 ± 8.8 ms and 45.7 ± 6.2 ms; P < 0.01). These results demonstrate that MSCs do not acquire the electrophysiological properties of mature cardiomyocytes during the survival period in the infarcted hearts. However, they can alleviate the electrical vulnerability and do not promote ventricular arrhythmias.

Combining adult stem cells and polymeric devices for tissue engineering in infarcted myocardium

An increasing number of studies in cardiac cell therapy have provided encouraging results for cardiac repair. Adult stem cells may overcome ethical and availability concerns, with the additional advantages, in some cases, to allow autologous grafts to be performed. However, the major problems of cell survival, cell fate determination and engraftment after transplantation, still remain. Tissue-engineering strategies combining scaffolds and cells have been developed and have to be adapted for each type of application to enhance stem cell function. Scaffold properties required for cardiac cell therapy are here discussed. New tissue engineering advances that may be implemented in combination with adult stem cells for myocardial infarction therapy are also presented. Biomaterials not only provide a 3D support for the cells but may also mimic the structural architecture of the heart. Using hydrogels or particulate systems, the biophysical and biochemical microenvironments of transplanted cells can also be controlled. Advances in biomaterial engineering have permitted the development of sophisticated drug-releasing materials with a biomimetic 3D support that allow a better control of the microenvironment of transplanted cells.

Pressure overload leads to an increase of cardiac resident stem cells

Recent studies suggest that the mammalian heart possesses some capacity for cardiac regeneration. This regenerative capacity is primarily documented postnatally and after myocardial infarction or pressure overload. Although the cell type that mediates endogenous regeneration is unclear, cardiac stem cells might be considered as potential candidates. To determine the number of c-kit + cardiac resident cells under conditions of pressure overload, we evaluated specimens derived from n = 8 patients with pressure overloaded single right ventricles in comparison to n = 4 explanted hearts from patients with dilated cardiomyopathy and n = 14 biopsies from children after heart transplantation. The age of the patients ranged from 16 days to 19 years. For quantification of cardiac stem cells, c-kit+/mast cell tryptase-/CD45- cells were counted and expressed as percent of the total nuclei. In specimens from patients with dilated cardiomyopathy, 0.13 ± 0.09% c-kit +/mast cell tryptase-/CD45- cells were detected. However, in specimens from patients with pressure overloaded single right ventricles, the numbers of c-kit+/mast cell tryptase-/CD45- cells were significantly higher (0.41 ±0.24%, p < 0.05). Under conditions of pressure overload, the right ventricle shows an approximately three-fold increase in c-kit+/mast cell tryptase-/CD45- cardiac resident cells. Despite the fact that this increased number of c-kit+ cells is not sufficient to prevent the failing heart from congestive heart failure, understanding the mechanism that leads to an increase of presumably cardiac resident stem cells under conditions of pressure overload might help to develop new strategies to enhance endogenous repair.

Left atrium of the human adult heart contains a population of side population cells

Cardiac "side population" (SP) cells have previously been found to differentiate into both endothelial cells and cardiomyocytes in mice and rats, but there are no data on SP cells in the human adult heart. Therefore, human cardiac atrial biopsies were dissociated, stained for SP cells and analyzed with FACS. Identified cell populations were analyzed for gene expression by quantitative real-time PCR and subjected to in vitro differentiation. Only biopsies from the left atrium contained a clearly distinguishable population of SP cells (0.22 ± 0.08%). The SP population was reduced by co-incubation with MDR1 inhibitor Verapamil, while the ABCG2 inhibitor FTC failed to decrease the number of SP cells. When the gene expression was analyzed, SP cells were found to express significantly more MDR1 than non-SP cells. For ABCG2, there was no detectable difference. SP cells also expressed more of the stem cell-associated markers C-KIT and OCT-4 than non-SP cells. On the other hand, no significant difference in the expression of endothelial and cardiac genes could be detected. SP cells were further subdivided based on CD45 expression. The CD45-SP population showed evidence of endothelial commitment at gene expression level. In conclusion, the results show that a SP population of cells is present also in the human adult heart.

Secretome of apoptotic peripheral blood cells (APOSEC) confers cytoprotection to cardiomyocytes and inhibits tissue remodelling after acute myocardial infarction: a preclinical study

Heart failure following acute myocardial infarction (AMI) is a major cause of morbidity and mortality. Our previous observation that injection of apoptotic peripheral blood mononuclear cell (PBMC) suspensions was able to restore long-term cardiac function in a rat AMI model prompted us to study the effect of soluble factors derived from apoptotic PBMC on ventricular remodelling after AMI. Cell culture supernatants derived from irradiated apoptotic peripheral blood mononuclear cells (APOSEC) were collected and injected as a single dose intravenously after myocardial infarction in an experimental AMI rat model and in a porcine closed chest reperfused AMI model. Magnetic resonance imaging (MRI) and echocardiography were used to quantitate cardiac function. Analysis of soluble factors present in APOSEC was performed by enzyme-linked immunosorbent assay (ELISA) and activation of signalling cascades in human cardiomyocytes by APOSEC in vitro was studied by immunoblot analysis. Intravenous administration of a single dose of APOSEC resulted in a reduction of scar tissue formation in both AMI models. In the porcine reperfused AMI model, APOSEC led to higher values of ejection fraction (57.0 vs. 40.5%, p < 0.01), a better cardiac output (4.0 vs. 2.4 l/min, p < 0.001) and a reduced extent of infarction size (12.6 vs. 6.9%, p < 0.02) as determined by MRI. Exposure of primary human cardiac myocytes with APOSEC in vitro triggered the activation of pro-survival signalling-cascades (AKT, Erk1/2, CREB, c-Jun), increased anti-apoptotic gene products (Bcl-2, BAG1) and protected them from starvation-induced cell death. Intravenous infusion of culture supernatant of apoptotic PBMC attenuates myocardial remodelling in experimental AMI models. This effect is probably due to the activation of pro-survival signalling cascades in the affected cardiomyocytes.

Interleukin-10 deficiency impairs bone marrow-derived endothelial progenitor cell survival and function in ischemic myocardium

RATIONALE

Endothelial progenitor cell (EPC) survival and function in the injured myocardium is adversely influenced by hostile microenvironment such as ischemia, hypoxia, and inflammatory response, thereby compromising full benefits of EPC-mediated myocardial repair.

OBJECTIVE

We hypothesized that interleukin-10 (IL-10) modulates EPC biology leading to enhanced survival and function after transplantation in the ischemic myocardium.

METHODS AND RESULTS

Myocardial infarction (MI)-induced mobilization of bone marrow EPC (Sca-1+Flk1+cells) into the circulation was significantly impaired in IL-10 knockout (KO) mice. Bone marrow transplantation to replace IL-10 KO marrow with wild-type (WT) marrow attenuated these effects. Impaired mobilization was associated with lower stromal cell-derived factor (SDF)-1 expression levels in the myocardium of KO mice. Interestingly, SDF-1 administration reversed mobilization defect in KO mice. In vitro, hypoxia-mediated increases in CXCR4 expression and cell survival were lower in IL-10-deficient EPCs. Furthermore, SDF-1-induced migration of WT EPCs was inhibited by AMD3100, an inhibitor of CXCR4. To further study the effect of IL-10 on in vivo EPC survival and engraftment into vascular structures, GFP-labeled EPC were injected intramyocardially after induction of MI, and the mice were treated with either saline or recombinant IL-10. The IL-10-treated group showed increased retention of transplanted EPCs in the myocardium and was associated with significantly reduced EPC apoptosis after MI. Interestingly, increased EPC retention and their association with the vascular structures was observed in IL-10-treated mice. Increased EPC survival and angiogenesis in the myocardium of IL-10-treated mice corroborated with improved left ventricular function, reduced infarct size, and fibrosis in the myocardium. In vitro, IL-10-induced increase in VEGF expression in WT EPC was abrogated by STAT3 inhibitor, suggesting IL-10 signals through STAT3 activation.

CONCLUSIONS

Taken together, our studies demonstrate that MI-induced EPC mobilization was impaired in IL-10 KO mice and that IL-10 increases EPC survival and function possibly through activation of STAT3/VEGF signaling cascades, leading to attenuation of MI-induced left ventricular dysfunction and remodeling.

Mesenchymal stromal cells mediate a switch to alternatively activated monocytes/macrophages after acute myocardial infarction

Given the established anti-inflammatory properties of mesenchymal stromal cells (MSCs), we investigated their effect on inflammatory cell infiltration of ischemic cardiac tissue and cardiac function. We employed two types of MSCs, human bone marrow-derived (BM) MSCs and human umbilical cord perivascular cells in an experimental acute myocardial infarction (MI) model with the immune-deficient NOD/SCID gamma null mouse. Cells were infused 48 h after induction of MI and mice assessed 24 h later (72 h after MI) for bone marrow (BM), circulating and cardiac tissue-infiltrating monocytes/macrophages. We showed that in the presence of either MSC type, overall macrophage/monocyte levels were reduced, including pro-inflammatory M1-type macrophages, while the proportion of alternatively activated M2-type macrophages was significantly increased in the circulation and heart but not the BM. Moreover, we found decreased expression of IL-1β and IL-6, increased IL-10 expression and fewer apoptotic cardiomyocytes without changes in angiogenesis in the infarct area. Fractional shortening was enhanced 2 weeks after cell infusion but was similar to medium controls 16 weeks after MI. In vitro studies showed that BM MSCs increased the frequency of alternatively activated monocytes/macrophages, in part by MSC-mediated secretion of IL-10. Our data suggest a new mechanism for MSC-mediated enhancement of cardiac function, possibly via an IL-10 mediated switch from infiltration of pro-inflammatory to anti-inflammatory macrophages at the infarct site. Additional studies are warranted confirming the role of IL-10 and augmenting the anti-inflammatory effects of MSCs in cardiac regeneration.

Hematopoietic cytokines for cardiac repair: mobilization of bone marrow cells and beyond

Hematopoietic cytokines, traditionally known to influence cellular proliferation, differentiation, maturation, and lineage commitment in the bone marrow, include granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage colony-stimulating factor, stem cell factor, Flt-3 ligand, and erythropoietin among others. Emerging evidence suggests that these cytokines also exert multifarious biological effects on diverse nonhematopoietic organs and tissues. Although the precise mechanisms remain unclear, numerous studies in animal models of myocardial infarction (MI) and heart failure indicate that hematopoietic cytokines confer potent cardiovascular benefits, possibly through mobilization and subsequent homing of bone marrow-derived cells into the infarcted heart with consequent induction of myocardial repair involving multifarious mechanisms. In addition, these cytokines are also known to exert direct cytoprotective effects. However, results from small-scale clinical trials of G-CSF therapy as a single agent after acute MI have been discordant and largely disappointing. It is likely that cardiac repair following cytokine therapy depends on a number of known and unknown variables, and further experimental and clinical studies are certainly warranted to accurately determine the true therapeutic potential of such therapy. In this review, we discuss the biological features of several key hematopoietic cytokines and present the basic and clinical evidence pertaining to cardiac repair with hematopoietic cytokine therapy.

Perfusion defect size predicts engraftment but not early retention of intra-myocardially injected cardiosphere-derived cells after acute myocardial infarction

Therapeutic cell retention and engraftment are critical for myocardial regeneration. Underlying mechanisms, including the role of tissue perfusion, are not well understood. In Wistar Kyoto rats, syngeneic cardiosphere-derived cells (CDCs) were injected intramyocardially, after experimental myocardial infarction. CDCs were labeled with [¹⁸F]-FDG (n = 7), for quantification of 1-h retention, or with sodium-iodide-symporter gene (NIS; n = 8), for detection of 24-h engraftment by reporter imaging. Perfusion was imaged simultaneously. Infarct size was 37 ± 9 and 38 ± 9% of LV in FDG and NIS groups. Cell signal was located in the infarct border zone in all animals. No significant relationship was observed between infarct size and 1-h CDC retention (r = −0.65; P = 0.11). However, infarct size correlated significantly with 24-h engraftment (r = 0.75; P = 0.03). Residual perfusion at the injection site was not related to cell retention/engraftment. Larger infarcts are associated with improved CDC engraftment. This observation encourages further investigation of microenvironmental conditions after ischemic damage and their role in therapeutic cell survival.

Stem cells and growth factor delivery systems for cardiovascular disease

Coronary (CAD) and peripheral (PAD) artery diseases are major causes of morbidity and mortality, and millions of CAD and PAD patients are treated by various medications, bypass surgery or angioplasty around the world. Such patients might benefit from novel stem cells and tissue engineering strategies aimed at accelerating natural processes of postnatal collateral vessel formation and repairing damaged tissues. By combining three fundamental "tools", namely stem cells, biomaterials and growth factors (GFs), such strategies may enhance the efficacy of cell therapy in several ways: (a) by supplying exogenous stem cells or GFs that stimulate resident cardiac stem cell (CSC) migration, engraftment and commitment to cardiomyocytes, and that induce and modulate arterial response to ischemia; (b) by supporting the maintenance of GFs and transplanted stem cells in the damaged tissues through the use of biocompatible and biodegradable polymers for a period of time sufficient to allow histological and anatomical restoration of the damaged tissue. This review will discuss the potential of combining stem cells and new delivery systems for growth factors, such as vehicle-based delivery strategies or cell-based gene therapy, to facilitate regeneration of ischemic tissues. These approaches would promote the ability of resident CSCs or of exogenous multipotent stem cells such as adipose tissue-derived mesenchymal stem cells (AT-MSCs) to induce the healing of damaged tissue, by recruiting and directing these cells into the damage area and by improving angiogenesis and reperfusion of ischemic tissues.

Stem cell-based therapies in ischemic heart diseases: a focus on aspects of microcirculation and inflammation

Stem cells possessing the potential to replace damaged myocardium with functional myocytes have drawn increasing attention in the past decade in treating ischemic heart diseases; these diseases are the leading cause of morbidity and mortality in the world. The adult heart has recently been shown to contain a few cardiac stem cells (CSCs) that, in theory, suggest cardiac repair following acute myocardial infarction is possible if the CSC titer could be increased. Stem cell-based therapies, including hematopoietic stem cells and mesenchymal stem cells, were proven to be marginal and transitional. Multiple factors and mechanisms, rather than direct cardiac regeneration are involved in stem cell-mediated cardiac functional improvement. This review will focus on (1) the interaction between inflammation and stem cells; (2) the fate of stem cells at the microcirculatory level, and their subsequent influences on stem cell-based therapies.

In vitro epithelial-to-mesenchymal transformation in human adult epicardial cells is regulated by TGFβ-signaling and WT1

Adult epicardial cells are required for endogenous cardiac repair. After myocardial injury, they are reactivated, undergo epithelial-to-mesenchymal transformation (EMT) and migrate into the injured myocardium where they generate various cell types, including coronary smooth muscle cells and cardiac interstitial fibroblasts, which contribute to cardiac repair. To understand what drives epicardial EMT, we used an in vitro model for human adult epicardial cells. These cells have an epithelium-like morphology and markedly express the cell surface marker vascular cell adhesion marker (VCAM-1). In culture, epicardial cells spontaneously undergo EMT after which the spindle-shaped cells now express endoglin. Both epicardial cells before and after EMT express the epicardial marker, Wilms tumor 1 (WT1). Adding transforming growth factor beta (TGFβ) induces loss of epithelial character and initiates the onset of mesenchymal differentiation in human adult epicardial cells. In this study, we show that TGFβ-induced EMT is dependent on type-1 TGFβ receptor activity and can be inhibited by soluble VCAM-1. We also show that epicardial-specific knockdown of Wilms tumor-1 (WT1) induces the process of EMT in human adult epicardial cells, through transcriptional regulation of platelet-derived growth factor receptor alpha (Pdgfrα), Snai1 and VCAM-1. These data provide new insights into the process of EMT in human adult epicardial cells, which might provide opportunities to develop new strategies for endogenous cell-based cardiac repair.

Hepatocyte growth factor mobilizes non-bone marrow-derived circulating mesoangioblasts

AIMS

The identification of factors that mobilize subsets of endogenous progenitor cells may provide new therapeutic tools to enhance the repair of ischaemic tissue. We previously identified circulating mesenchymal cells that co-express endothelial markers (so-called circulating mesoangioblasts, cMABs) in children undergoing heart surgery with cardiopulmonary bypass (CPB). However, the mechanisms by which these cells are mobilized and their origin is unclear.

METHODS AND RESULTS

Circulating CD73(+)CD45(-)KDR(+) cMABs were analysed in adults undergoing heart surgery with (n = 21) or without CPB (n = 8). During surgery with CPB, cMABs are mobilized with a maximal response at the end of the operation. In contrast, off-pump heart surgery does not stimulate cMAB mobilization, indicating that the stress mediated by CPB induces the mobilization of cMAB. Circulating mesoangioblasts were enriched in blood obtained from the coronary sinus. Histologically, CD73(+) cells were detected around vessels in the heart, indicating that the heart is one of the niches of cMABs. Consistently, studies in gender mismatched bone marrow transplanted patients demonstrated that cMABs did not originate from the bone marrow. Cytokine profiling of serum samples revealed that hepatocyte growth factor (HGF) was profoundly increased at the time point of maximal mobilization of cMABs. Hepatocyte growth factor stimulated the migration of cMABs. Importantly, injection of recombinant HGF increased cMABs in rats.

CONCLUSIONS

Hepatocyte growth factor induces mobilization of non-haematopoietic progenitor cells with a cardiac repair capacity. This newly identified function together with the known pleiotrophic effects of HGF makes HGF an attractive therapeutic option for the treatment of ischaemic heart disease.