Granulocyte-colony-stimulating factor in acute myocardial infarction: future perspectives after FIRSTLINE-AMI and REVIVAL-2

Proteomic study of the microdissected aortic media in human thoracic aortic aneurysms

Aortic aneurysm is a complex multifactorial disease, and its molecular mechanism is not understood. In thoracic aortic aneurysm (TAA), the expansion of the aortic wall is lead by extracellular matrix (ECM) degeneration in the medial layer, which leads to weakening of the aortic wall. This dilatation may end in rupture and-if untreated-death. The aortic media is composed of vascular smooth muscle cells (VSMCs) and proteins involved in aortic elasticity and distensibility. Delineating their functional and quantitative decrease is critical in elucidating the disease causing mechanisms as well as the development of new preventive therapies. Laser microdissection (LMD) is an advanced technology that enables the isolation of the desired portion of tissue or cells for proteomics analysis, while preserving their integrity. In our study, the aortic media layers of 36 TAA patients and 8 controls were dissected using LMD technology. The proteins isolated from these tissue samples were subjected to comparative proteomic analysis by nano-LC-MS/MS, which enabled the identification of 352 proteins in aortic media. Among these, 41 proteins were differentially expressed in the TAA group with respect to control group, and all were downregulated in the patients. Of these medial proteins, 25 are novel, and their association with TAA is reported for the first time in our study. Subsequent analysis of the data by ingenuity pathway analysis (IPA) shows that the majority of differentially expressed proteins were found to be cytoskeletal-associated proteins and components of the ECM which are critical in maintaining aortic integrity. Our results indicate that the protein expression profile in the aortic media from TAA patients differs significantly from controls. Further analysis of the mechanism points to markers of pathological ECM remodeling, which, in turn, affect VSMC cytosolic structure and architecture. In the future, the detailed investigation of the differentially expressed proteins may provide insight into the elucidation of the pathological processes underlying aneurysms.

Bone marrow-derived mesenchymal stem cells migrate to healthy and damaged salivary glands following stem cell infusion

Xerostomia is a severe side effect of radiation therapy in head and neck cancer patients. To date, no satisfactory treatment option has been established. Because mesenchymal stem cells (MSCs) have been identified as a potential treatment modality, we aimed to evaluate stem cell distribution following intravenous and intraglandular injections using a surgical model of salivary gland damage and to analyse the effects of MSC injections on the recruitment of immune cells. The submandibular gland ducts of rats were surgically ligated. Syngeneic adult MSCs were isolated, immortalised by simian virus 40 (SV40) large T antigen and characterized by flow cytometry. MSCs were injected intravenously and intraglandularly. After 1, 3 and 7 days, the organs of interest were analysed for stem cell recruitment. Inflammation was analysed by immunohistochemical staining. We were able to demonstrate that, after intravenous injection, MSCs were recruited to normal and damaged submandibular glands on days 1, 3 and 7. Unexpectedly, stem cells were recruited to ligated and non-ligated glands in a comparable manner. After intraglandular injection of MSCs into ligated glands, the presence of MSCs, leucocytes and macrophages was enhanced, compared to intravenous injection of stem cells. Our data suggest that injected MSCs were retained within the inflamed glands, could become activated and subsequently recruited leucocytes to the sites of tissue damage.

Association of Stat3 with HSF1 plays a critical role in G-CSF-induced cardio-protection against ischemia/reperfusion injury

Granulocyte colony-stimulating factor (G-CSF) has been shown to be cardio-protective against ischemia through activating Jak2/Stat3 pathway, however, the mechanism is unclear. Heat shock transcription factor 1 (HSF1), a definite endogenous protective protein in cardiomyocytes, may interact with Stat family under stress conditions. We hypothesized that G-CSF could induce cardio-protection against ischemia/reperfusion (I/R) through association of HSF1 with Stat3. To test the hypothesis, we built cardiac I/R injury model with HSF1 knockout (KO) mice and wild type (WT) mice by occlusion of the left anterior descending (LAD) coronary artery for 30min and subsequent release of the occlusion for 24h. These mice were administered with G-CSF (100μg/kg/day) or vehicle subcutaneously for 3days before surgery. As expected, G-CSF induced significant cardio-protections against I/R injury, characterized by higher ejection fraction (EF%), lower left ventricular end diastolic pressure (LVEDP), increased dp/dt value and decreased infarct area as compared with the vehicle treatment in WT mice. In HSF1-KO mice, however, these cardio-protections induced by G-CSF were greatly attenuated. Inhibition of oxidative stress-induced cardiomyocyte apoptosis by G-CSF also disappeared due to the deficiency of HSF1 in vitro and in vivo. Furthermore, G-CSF increased the phosphorylation and the association of Stat3 with HSF1, which enhanced transcriptional activity of HSF1. Inhibition of either Stat3 or HSF1 by pharmacological agents suppressed G-CSF-induced association of the two proteins and anti-apoptotic effect on cardiomyocytes. Our data suggest that G-CSF stimulates phosphorylation and association of Stat3 with HSF1 and therefore enhances transcriptional activity of HSF1, leading to the cardio-protection against I/R injury.

Pregenerative medicine: developmental paradigms in the biology of cardiovascular regeneration

The ability to create new functional cardiomyocytes is the holy grail of cardiac regenerative medicine. From studies using model organisms, new insights into the fundamental pathways that drive heart muscle regeneration have begun to arise as well as a growing knowledge of the distinct families of multipotent cardiovascular progenitors that generate diverse lineages during heart development. In this Review, we highlight this intersection of the "pregenerative" biology of heart progenitor cells and heart regeneration and discuss the longer term challenges and opportunities in moving toward a therapeutic goal of regenerative cardiovascular medicine.

G-CSF induces a potentially tolerant gene and immunophenotype profile in T cells in vivo

G-CSF can induce functional immune tolerance in man. In this study, purified T cells from G-CSF-mobilized peripheral blood stem cell (PBSC) donors were analysed by gene expression profiling and immunophenotyping. Results suggested a predominantly immune tolerant profile with upregulation of genes related to Th2 and Treg cells, downregulation of genes associated with Th1 cells, cytotoxicity, antigen presentation and graft-versus-host disease (GVHD) and overexpression of negative regulators of Th17 differentiation. Immunophenotyping revealed that during G-CSF exposure donors had reduced levels of T cells with a Th17 phenotype (CD4+IL-17A+CCR6+IL-23R+), more than three times lower compared to normal controls. G-CSF also led to increased levels of CD4+CD25highCD45RO+ Treg cells. Furthermore, mRNA levels of RORgammat, a Th17-specific transcription factor, decreased in T cells isolated from G-CSF-mobilized PBSC harvests. Th17 cells have been implicated in autoimmune diseases and GVHD pathophysiology. Our study is the first to report the effect of G-CSF on the Th17 subpopulation.

Cardiomyocyte death and renewal in the normal and diseased heart

During post-natal maturation of the mammalian heart, proliferation of cardiomyocytes essentially ceases as cardiomyocytes withdraw from the cell cycle and develop blocks at the G0/G1 and G2/M transition phases of the cell cycle. As a result, the response of the myocardium to acute stress is limited to various forms of cardiomyocyte injury, which can be modified by preconditioning and reperfusion, whereas the response to chronic stress is dominated by cardiomyocyte hypertrophy and myocardial remodeling. Acute myocardial ischemia leads to injury and death of cardiomyocytes and nonmyocytic stromal cells by oncosis and apoptosis, and possibly by a hybrid form of cell death involving both pathways in the same ischemic cardiomyocytes. There is increasing evidence for a slow, ongoing turnover of cardiomyocytes in the normal heart involving death of cardiomyocytes and generation of new cardiomyocytes. This process appears to be accelerated and quantitatively increased as part of myocardial remodeling. Cardiomyocyte loss involves apoptosis, autophagy, and oncosis, which can occur simultaneously and involve different individual cardiomyocytes in the same heart undergoing remodeling. Mitotic figures in myocytic cells probably represent maturing progeny of stem cells in most cases. Mitosis of mature cardiomyocytes that have reentered the cell cycle appears to be a rare event. Thus, cardiomyocyte renewal likely is mediated primarily by endogenous cardiac stem cells and possibly by blood-born stem cells, but this biological phenomenon is limited in capacity. As a consequence, persistent stress leads to ongoing remodeling in which cardiomyocyte death exceeds cardiomyocyte renewal, resulting in progressive heart failure. Intense investigation currently is focused on cell-based therapies aimed at retarding cardiomyocyte death and promoting myocardial repair and possibly regeneration. Alteration of pathological remodeling holds promise for prevention and treatment of heart failure, which is currently a major cause of morbidity and mortality and a major public health problem. However, a deeper understanding of the fundamental biological processes is needed in order to make lasting advances in clinical therapeutics in the field.

[Cell-based strategies for salivary gland regeneration]

Xerostomia as a side effect of radiotherapy or due to Sjögren's disease leads to considerable impairment of the quality of life of the affected patients. Preventive treatment approaches such as intensity-modulated radiotherapy, surgical transfer of a submandibular gland to a site outside the radiation field or administration of amifostin during radiation treatment are not yet completely established in clinical practice and are not applicable for all patients. Symptomatic treatment with pilocarpin or synthetic saliva leads to an improvement of the symptoms only in some patients, and in the case of pilocarpin significant systemic anticholinergic side-effects might occur. Because large numbers of patients are affected and current treatment options are not satisfactory, it is essential to develop new treatment options. In parallel with the in vitro production of functional salivary gland constructs by means of tissue engineering techniques, attempts are currently under way to experimentally restore salivary gland function by genetic treatment approaches such as transfection of the affected salivary glands with aquaporins or pro-angiogenic factors. In addition, the in vivo application of stem cells is under investigation. In the present paper, we discuss the clinical and radiobiological background of xerostomia and highlight possible innovative future treatment options.

G-CSF-Based Stem Cell Therapy for the Heart?Unresolved Issues Part A: Paracrine Actions, Mobilization, and Delivery

The results of large-scale clinical trials involving granulocyte colony-stimulating factor (G-CSF)-based mobilization of bone marrow stem cells to improve cardiac remodeling and function after acute myocardial infarction have been disappointing. These trials came about as the result of an explosion of animal studies reporting dramatic successes with this therapeutic approach and small-scale nonrandomized, nonblinded clinical trials suggesting beneficial effects in humans as well. It would be rash to conclude, however, that G-CSF-based stem cell therapies for repairing the injured or failing heart are not worth pursuing. Recent advances in basic science not only help explain the failure of the larger clinical trials but have revitalized interest into using G-CSF-based or G-CSF-related therapies for the injured heart. This article will provide an overview of recent advances that have been made in the direct protective actions of G-CSF on cardiac cells, the mobilization of stem cells from the bone marrow, and the delivery of these cells to the heart. Such knowledge could be readily exploited to make G-CSF-based therapy a reality for the clinician.

Cardiac tissue engineering: a clinical perspective

Engineered myocardium may be used to repair myocardial defects. Although not clinically applicable yet, initial studies in rodents have demonstrated the feasibility of tissue engineering based myocardial repair in vivo. In order for restorative treatment to evolve into a functional treatment modality, tissue engineers have to generate human myocardium of sufficient size and with relevant contractile function to replace/repair myocardial defects. This requires the identification of a scalable and ideally autologous cardiomyocyte source as well as the development of strategies to overcome size limitations. We will further address pivotal issues pertaining to the allocation of suitable human cells for myocardial tissue engineering and discuss the translation of present myocardial tissue engineering concepts into preclinical, as well as clinical, trials.