Antidiabetic gliptins in combination with G-CSF enhances myocardial function and survival after acute myocardial infarction

Background

Medical stimulation of endogenous progenitor cell circulation may serve as a new therapeutic tool for treatment of acute myocardial infarction. We analyzed the effects of antidiabetic gliptins plus GCSF (granulocyte colony stimulating factor) on myocardial regeneration after myocardial infarction in a mouse model.

Methods and results

After surgical LAD-ligation (left anterior descending artery), Sitagliptin/Vildagliptin was applied yielding sufficient blood levels verified by mass spectrometry and significantly reducing activity of dipeptidyl peptidase (DPP) IV. GCSF or saline was administered intraperitoneally for 6 days. We assessed stem cell mobilization and homing (flow cytometry), infarct size (histology), neovascularization and cellular proliferation (immunohistology), heart function (Millar tip catheterization) and survival (Kaplan–Meier-curves). Gliptins ± GCSF administration increased mobilization and cardiac homing of bone-marrow derived stem cells by stabilization of cardiac SDF1 (stromal cell-derived factor). For Sitagliptin, it could be shown that resident cardiac stem cells were stimulated, neovascularization was enhanced and cardiac remodeling was reduced. These effects finally improved myocardial function and increased survival for both gliptins. Although gliptins as a mono therapy lead to remarkable effects in a dose dependent manner and were superior to G-CSF mono-therapy, dual application of GCSF and gliptins revealed the best results. Since both gliptins yielded comparable effects concerning stem cell homing, cardiac function and survival, we suggest a class-effect of DPP-IV-inhibitors.

Conclusions

Thus, gliptins + GCSF and in high concentrations even as mono therapy have beneficial effects on cardiac regeneration after myocardial infarction beyond its anti-diabetic potential.     

Circulating progenitor cells in stable coronary heart disease and acute coronary syndromes: relevant reparatory mechanism?

Bone marrow-derived cells which may be involved in cardiac repair/regeneration after ischaemic injury must undergo mobilisation into peripheral blood with subsequent homing and engraftment into the target organ. Mobilisation of the heterogeneous population of stem/progenitor cells in endothelial injury or myocardial ischaemia has been described recently. The number of circulating stem/progenitor cells reflects the endothelial damage, and turnover may be a surrogate marker reflecting the burden of cardiovascular risk factors and prognostic markers in stable coronary heart disease and acute coronary syndromes. Acute coronary syndromes are associated with increased levels of inflammatory and haematopoietic cytokines which, in turn, can mobilise progenitor cells from the bone marrow. Myocardial infarction increases the number of endothelial progenitor cells and other less well-defined subpopulations, such as CD34/c-kit(+) and CD34/CXCR4(+) cells, which may take part in cardiac repair after ischaemic injury. Data on mobilisation of stem/progenitor cells in acute coronary syndromes are summarised here. Cell types, mechanisms of mobilisation, homing and engraftment are discussed and their relevance to clinical outcomes.     

Bone-marrow-derived cell transfer after ST-elevation myocardial infarction: lessons from the BOOST trial

Emerging evidence suggests that bone-marrow-derived stem and progenitor cells can be used to improve cardiac function after acute myocardial infarction. We tested this concept in the randomized, controlled, BOOST (bone marrow transfer to enhance ST-elevation infarct regeneration) clinical trial. Following successful percutaneous coronary intervention for acute ST-elevation myocardial infarction, patients received an intracoronary transfer of autologous bone marrow cells (BMCs). After 6 months, global left ventricular ejection fraction, as determined by magnetic resonance imaging, was significantly improved in the BMC-treated group compared with the control group. BMC transfer enhanced left ventricular systolic function, primarily in myocardial segments adjacent to the infarcted area, and also had a positive effect on diastolic function. BMC transfer did not increase the risk of adverse clinical events and did not promote in-stent re-stenosis or proarrhythmic effects. In principle, the effects of BMC transfer on ejection fraction were sustained at 18-month follow-up. Notably, radioactive labeling of BMCs and positron emission tomography showed that these beneficial effects are achieved with limited cardiac homing of BMCs after intracoronary application. Taken together, our studies indicate that intracoronary transfer of autologous BMCs is a safe, promising, and novel approach to further improving systolic function in patients with successful reperfusion after acute myocardial infarction.     

Signaling factors in stem cell-mediated repair of infarcted myocardium

Myocardial infarction leads to scar formation and subsequent reduced cardiac performance. The ultimate therapy after myocardial infarction would pursue stem cell-based regeneration. The aim of stem cell-mediated cardiac repair embodies restoration of cardiac function by regeneration of healthy myocardial tissue, which is accomplished by neo-angiogenesis and cardiogenesis. A major reservoir of adult autologous stem cells distal from the heart is the bone marrow. Adequate regulation of signaling between the bone marrow, the peripheral circulation and the infarcted myocardium is important in orchestrating the process of mobilization, homing, incorporation, survival, proliferation and differentiation of stem cells, that leads to myocardial regeneration. In this review, we discuss key signaling factors, including cytokines, chemokines and growth factors, which are involved in orchestrating the stem cell driven repair process. We focus on signaling factors known for their mobilizing and chemotactic abilities (SDF-1, G-CSF, SCF, IL-8, VEGF), signaling factors that are expressed after myocardial infarction involved in the patho-physiological healing process (TNF-alpha, IL-8, IL-10, HIF-1alpha, VEGF, G-CSF) and signaling factors that are involved in cardiogenesis and neo-angiogenesis (VEGF, EPO, TGF-beta, HGF, HIF-1alpha, IL-8). The future therapeutic application and capacity of secreted factors to modulate tissue repair after myocardial infarction relies on the intrinsic potency of factors and on the optimal localization and timing of a combination of signaling factors to stimulate stem cells in their niche to regenerate the infarcted heart.     

Myocardial regeneration induced by granulocyte-colony-stimulating factor mobilization of stem cells in patients with acute or chronic ischaemic heart disease: a non-invasive alternative for clinical stem cell therapy?

Mobilization of stem cells into the peripheral circulation for myocardial regeneration using subcutaneous injections of granulocyte-colony-stimulating factor (G-CSF) has been tested in both patients with acute myocardial infarction (AMI) and patients with chronic myocardial ischaemia. G-CSF treatment seems to be safe and unblinded trials in patients with AMI were encouraging. However, larger double-blind placebo-controlled trials have not been able to demonstrate effect of G-CSF treatment. In patients with chronic myocardial ischaemia, small-unblinded G-CSF trials did not show effect on myocardial perfusion and function. In both patient populations, G-CSF did mobilize stem cells of known importance to myocardial regeneration, but there seemed to be a general lack of homing of the stem cells into the ischaemic myocardium. In AMI, factors of importance to homing of stem cells, stem cell derived factor-1, are maximally elevated in plasma 3 weeks after infarction, suggesting that this time point could be the optimal time for stem cell mobilization treatment. The known complex interaction of stem cells and cytokines for induction of vasculogenesis should be implemented in future clinical trials, to elucidate whether G-CSF mobilization of stem cells might be useful as a new regenerative treatment in patients with ischaemic heart disease.     

Stammzelltherapie nach akutem Myokardinfarkt

Therapeutic successes in the area of stem cell research have opened up many new avenues for treating cardiovascular diseases, especially with respect to the prevention of the development of cardiac failure due to acute myocardial infarction or chronic coronary artery disease. Currently, the delivery of bone marrow-derived stem cells and circulating progenitor cells via the coronary artery, intravenous, the left ventricle (transendocardial) as well as directly into the heart muscle during cardiac bypass surgery (intramyocardial) is being investigated intensively for the treatment of acute myocardial infarction and chronic coronary artery disease. All application modes pursue the same objective of regenerating damaged myocardium. In clinical studies, the concept of myocardial regeneration by injection of adult autologous stem cells or circulating progenitor cells has been transferred. In the majority of controlled and randomised trials as well as in several meta-analysis the therapeutic impact of intracoronary stem cell application in myocardial infarction is affirmed by a beneficial effect of stem cells or progenitor cells on mortality and morbidity in patients with reduced cardiac function after acute myocardial infarction.     

Pharmacologic and genetic strategies to enhance cell therapy for cardiac regeneration

Cell-based therapy is emerging as an exciting potential therapeutic approach for cardiac regeneration following myocardial infarction (MI). As heart failure (HF) prevalence increases over time, development of new interventions designed to aid cardiac recovery from injury are crucial and should be considered more broadly. In this regard, substantial efforts to enhance the efficacy and safety of cell therapy are continuously growing along several fronts, including modifications to improve the reprogramming efficiency of inducible pluripotent stem cells (iPS), genetic engineering of adult stem cells, and administration of growth factors or small molecules to activate regenerative pathways in the injured heart. These interventions are emerging as potential therapeutic alternatives and/or adjuncts based on their potential to promote stem cell homing, proliferation, differentiation, and/or survival. Given the promise of therapeutic interventions to enhance the regenerative capacity of multipotent stem cells as well as specifically guide endogenous or exogenous stem cells into a cardiac lineage, their application in cardiac regenerative medicine should be the focus of future clinical research. This article is part of a special issue entitled “Key Signaling Molecules in Hypertrophy and Heart Failure.”     

Cardiac stem cell therapy for myocardial regeneration. A clinical perspective

Myocardial infarction and other pathologic conditions of the heart result in loss of cardiomyocytes, scar formation, ventricular remodeling, and eventually heart failure. Since pharmacologic and interventional strategies fail to regenerate dead myocardium, heart failure continues to be a major health problem worldwide. Recent studies in animal models of myocardial infarction and heart failure have demonstrated that various subsets of adult primitive cells can regenerate functional cardiomyocytes and cardiac vasculature with improvement in cardiac structure and function. Small clinical trials of cell therapy in patients with myocardial infarction and ischemic cardiomyopathy have recapitulated these beneficial effects in humans with infarct size reduction and improvement in ejection fraction, myocardial perfusion, and wall motion. Several phenotypically distinct cell populations have been utilized for cardiac regeneration, and the relative merits of one cell over another remain to be determined. The recent discovery of adult cardiac stem cells has sparked intense hope for myocardial regeneration with cells that are from the heart itself and are thereby inherently programmed to reconstitute cardiac tissue. The purpose of this review is to summarize the evidence regarding the feasibility of cardiac repair in humans via adult stem/progenitor cells, and to discuss the potential utility of cardiac stem cells for therapeutic myocardial regeneration.     

Autologous stem cells for functional myocardial repair

Recent experimental studies based on innovative hypothesis utilizing cell therapy for the damaged myocardium are recently becoming increasingly promising. The naturally occurring myocardial reparative process is apparently complex and relatively inefficient. It consists of up-regulation of progenitor cell release from the bone marrow after myocardial infarction, homing of these cells to the injured tissue, and differentiation of these progenitor cells into vascular cells and cardiomyocytes within the infarcted tissue. Accordingly, there are two main strategies to regenerate myocardium with autologous stem cells: (1) Extracting stem cells from the bone marrow and injecting these cells into the damaged area, (2) Increasing the efficiency of the naturally occurring reparative process by increasing the mobilization of bone marrow–derived stem cells after myocardial infarction.This review summarizes the growing field of autologous stem cell utilization over the past decade and outlines scientific and clinical hurdles that need to be overcome before this therapy can fully reach its clinical potential.     

The stem cell movement

Stem or progenitor cell-based strategies to combat ischemic heart disease and myocardial infarction, whether autologous transplantation or stimulation of resident populations, not only require detailed insight into transdifferentiation potential and functional coupling, but the efficacy of this approach is underpinned by the need to induce appropriate migration and homing to the site of injury. This review focuses on existing insights into the trafficking of stem cells in the context of cardiac regenerative therapy, with particular focus on the wide variety of potential sources of cells, critical factors that may regulate their migration, and how extrapolating from embryonic stem/progenitor cell behavior during cardiogenesis may reveal pathways implicit in the adult heart postinjury.     

成体干细胞移植治疗急性心肌梗死的研究进展

干细胞治疗心血管疾病正处在起步阶段,在治疗急性心肌梗死方面已表现出传统方法无可比拟的优越性。骨髓干细胞、骨骼肌成肌细胞和内皮祖细胞等已被应用于心肌的再生。研究表明,干细胞可在梗死的心肌中分化形成有功能活性心肌、血管等组织,可改善心脏功能,但其作用机制尚不完全明了。本研究对成体干细胞移植治疗心肌梗死研究中取得的成就、有待解决的问题以及临床应用前景做一评述。     

Local injection of stem cell factor (SCF) improves myocardial homing of systemically delivered c-kit + bone marrow-derived stem cells

AIMS: Recent studies have shown that stem cell therapy may alleviate the detrimental effects of myocardial infarction. Yet, most of these reports observed only modest effects on cardiac function, suggesting that there still is need for improvement before widespread clinical use. One potential approach would be to increase migration of stem cells to the heart. We therefore tested whether local administration of stem cell factor (SCF) improves myocardial homing of intravenously infused lin-/c-kit+ stem cells after myocardial infarction. METHODS AND RESULTS: Myocardial infarction was induced in mice via ligation of the left anterior descending artery and 2.5 microg of SCF were injected into the peri-infarct zone. Sham-operated mice and animals with intramyocardial injection of phosphate-buffered saline (PBS) served as controls. Twenty-four hours after myocardial infarction, lin-/c-kit+ stem cells were separated from murine bone marrow by magnetic cell sorting, labelled with the green fluorescent cell tracker CFDA or 111 Indium, and subsequently 750 000 labelled cells were systemically infused via the tail vein. Another 24 or 72 h later, respectively (i.e. 48 and 96 h after myocardial infarction), hearts were removed and analysed for myocardial homing of stem cells. Green fluorescent stem cells were exclusively detected in the peri-infarct zone of animals having prior SCF treatment. Radioactive measurements revealed that an intramyocardial SCF injection significantly amplified myocardial homing of lin-/c-kit+ stem cells compared to animals with PBS injections (3.58 +/- 0.53 vs. 2.28 +/- 0.23 cpm/mg/10(6)cpm, +60%, P < 0.05) and sham-operated mice without myocardial infarction (3.58 +/- 0.53 vs. 1.95 +/- 0.22 cpm/mg/10(6)cpm, +85%, P < 0.01). Similar results were obtained 72 h after stem cell injection. CONCLUSION: We demonstrate that intramyocardial administration of SCF sustainably directs more lin-/c-kit+ stem cells to the heart. Future studies will have to show whether higher levels of myocardial SCF (i.e. by virus-mediated gene transfer) can further improve homing of systemically delivered c-kit+ stem cells and thus favourably influence cardiac remodelling following myocardial infarction.     

Autologous cell transplantation for the treatment of damaged myocardium

Autologous cell transplantation for the treatment of damaged myocardium after myocardial infarction is becoming an increasingly promising strategy. This form of treatment can be divided into 2 treatment strategies: The first uses differentiated cell types to replace the scarred tissue with living cells, while the second strategy uses stem cells in an attempt to regenerate myocardium. Over the past decade, multiple cell types have been used in animal studies, and clinical trials to determine the safety of injecting and engrafting skeletal myoblasts into damaged myocardium are presently being conducted. Animals studies focused on using stem cells to regenerate damaged myocardium have shown a naturally occurring reparative process that consists of up-regulation of progenitor cell release from the bone marrow after myocardial infarction, homing of these cells to the injured tissue, and differentiation of these progenitor cells into vascular cells and cardiac myocytes within the infarcted tissue. Unfortunately, this process occurs with great infrequency. Strategies to regenerate myocardium with stem cells either extract stem cells from the bone marrow and inject these cells into the damaged area or they attempt to increase the efficiency of the natural reparative process by increasing the mobilization of bone marrow-derived stem cells after myocardial infarction. This review summarizes the field of cell transplantation over the past decade, discusses areas of controversy, and proposes an outline of advancements that need to be made in both the clinical and scientific arenas for autologous cell transplantation to fully reach its clinical potential.     

Mechanisms of action of mesenchymal stem cells in cardiac repair: potential influences on the cardiac stem cell niche

Clinical and basic studies of cell-based myocardial therapy have proceeded at a rapid pace. Cell therapy could lead to successful cardiac regeneration or repair by any of three general mechanisms: differentiation of the administered cells into all of the cellular constituents of the heart; release of factors capable of paracrine signaling from the administered cells; and fusion of the administered cells with the existing constituents of the heart. Here, we argue that a fourth general mechanism could be operative: stimulation of endogenous repair by injected cells, which and might cause the regeneration of stem cell niches. In a porcine model of myocardial infarction, allogeneic mesenchymal stem cells stimulated substantial improvement in the ejection fraction, reduction of infarct size, and the growth of a rim of new cardiac tissue in the region in which the mesenchymal stem cells were injected. These effects occurred in the absence of definitive cardiac myocyte differentiation. After myocardial infarction, porcine hearts exhibit evidence of cardiac myocytes that have entered the cell cycle, neovascularization, and reduced levels of apoptosis. These data, in addition to new insights regarding the presence of endogenous cardiac stem cells, strongly support the concept that the heart could contain stem cell niches. Effective cell therapy could lead to restoration of these niches through multifaceted cell-cell interactions.     

Cardiac side population cells: moving toward the center stage in cardiac regeneration

Over the past decade, extensive work in animal models and humans has identified the presence of adult cardiac progenitor cells, capable of cardiomyogenic differentiation and likely contributors to cardiomyocyte turnover during normal development and disease. Among cardiac progenitor cells, there is a distinct subpopulation, termed "side population" (SP) progenitor cells, identified by their unique ability to efflux DNA binding dyes through an ATP-binding cassette transporter. This review highlights the literature on the isolation, characterization, and functional relevance of cardiac SP cells. We review the initial discovery of cardiac SP cells in adult myocardium as well as their capacity for functional cardiomyogenic differentiation and role in cardiac regeneration after myocardial injury. Finally, we discuss recent advances in understanding the molecular regulators of cardiac SP cell proliferation and differentiation, as well as likely future areas of investigation required to realize the goal of effective cardiac regeneration.     

Cardiogenic small molecules that enhance myocardial repair by stem cells

The clinical success of stem cell therapy for myocardial repair hinges on a better understanding of cardiac fate mechanisms. We have identified small molecules involved in cardiac fate by screening a chemical library for activators of the signature gene Nkx2.5, using a luciferase knockin bacterial artificial chromosome (BAC) in mouse P19CL6 pluripotent stem cells. We describe a family of sulfonyl-hydrazone (Shz) small molecules that can trigger cardiac mRNA and protein expression in a variety of embryonic and adult stem/progenitor cells, including human mobilized peripheral blood mononuclear cells (M-PBMCs). Small-molecule-enhanced M-PBMCs engrafted into the rat heart in proximity to an experimental injury improved cardiac function better than control cells. Recovery of cardiac function correlated with persistence of viable human cells, expressing human-specific cardiac mRNAs and proteins. Shz small molecules are promising starting points for drugs to promote myocardial repair/regeneration by activating cardiac differentiation in M-PBMCs.     

Do stem cells in the heart truly differentiate into cardiomyocytes?

Chronic congestive heart failure (CHF) is a common consequence of heart muscle or valve damage and remains a major cause of morbidity and mortality worldwide. There are increasing interests to treat cardiac failure by stem cell-based therapy. Many types of stem cells or progenitor cells have been suggested for cellular therapy of heart failure. While stem cell-based therapy was initially thought to be achieved by transdifferentiation of stem cells into myocardial cells including cardiomyocytes it has become clear that this may be rather an infrequent event. Instead cardiac regeneration may result from vascular differentiation of stem cells or even from stem cell-mediated reverse remodelling. Thus the term stem cell-mediated cardiac regeneration covers the spectrum from stem cell transdifferentiation into cardiomyocytes to cell-mediated pharmacotherapy. In this review we revise stem cell-based cardiac regeneration both in experimental models and in clinical application. We have limited our discussion on some selected types of stem cells, with particular emphasis on their differentiation potential, current status and perspectives on their future applications.     

The adult human heart as a source for stem cells: repair strategies with embryonic-like progenitor cells

Adequate cell-based repair of adult myocardium remains an elusive goal because most cells that are used cannot generate mature myocardium sufficient to promote large functional improvements. Embryonic stem cells can generate both mature cardiocytes and vasculature, but their use is hampered by associated teratoma formation and the need for an allogeneic source. The detection of sca-1(+), c-kit(+), or isl-1(+) cardiac precursors and the creation of cardiospheres from adult heart tissues suggest that a persistent population of immature progenitor cells is present in the mature myocardium. These cell populations probably represent stages along a continuum of cardiac stem cell development and differentiation. We report isolation from ventricle of uncommitted cardiac progenitor cells, which appear to resemble the more immature, common pool of embryonic lateral plate mesoderm progenitors that yield both myocardial and endocardial cells during normal cardiac development. Under controlled in vitro conditions and in vivo, these cells can differentiate into endothelial, smooth muscle, and cardiomyocyte lineages and can be isolated and expanded to clinically relevant numbers from adult rat myocardial tissue. In this article, we discuss the potential for autologous repair or even cardiac regeneration with cells that follow a developmental pathway similar to embryonic cardiac precursors but without the inherent limitations associated with undifferentiated embryonic stem cells.     

Transcoronary delivery of bone marrow cells to the infarcted murine myocardium

Efficient strategies for labelling and delivery of bone marrow derived stem cells (BMCs) are required to elucidate the cellular kinetics and therapeutic effects after BMC transfer for myocardial infarction (MI). Lineage negative (lin-) BMCs, labelled ex vivo in a simple procedure with the cell tracker dye tetramethyl-rhodamine (TAMRA), were reliably detected by fluorescence microscopy with higher specificity than retroviral enhanced green fluorescence protein (EGFP) marking and detection. Only few cells entered the ischemic myocardium after intravenous (i.v.) application, but this number increased more than 18-fold after transcoronary delivery. Time course and kinetic analysis over 12 h revealed that myocardial colonization seems to be a biphasic process of first order decay with different elimination half-lives. Most cells are eliminated rapidly during the first 2 h (t1/2 40 min), but the remaining cells are retained significantly longer in the ischemic heart (t1/2 5.2 h). In contrast, BMC colonization of the spleen increased rather in a linear fashion. Although transcoronary BMC transfusion did not alter infarct size, it increased capillary density in the infarct border zone and improved LV function 4 weeks after MI.In conclusion, BMCs delivered by transcoronary injection increase capillary density and improve LV function after MI although homing to the ischemic heart is only transient.