1,721,063 research outputs found
Prometheus’s Heart: what lies beneath
No full textA heart attack kills off many cells in the heart. Parts of the heart become thin and fail to contract properly following the replacement oflost cells by scar tissue. However, the notion that the same adult cardiomyocytes beat throughout the lifespan of the organ and organism,without the need for a minimum turnover, gives way to a fascinating investigations. Since the late 1800s, scientists and cardiologistswanted to demonstrate that the cardiomyocytes cannot be generated after the perinatal period in human beings. This curiosity hasbeen passed down in subsequent years and has motivated more and more accurate studies in an attempt to exclude the presence ofrenewed cardiomyocytes in the tissue bordering the ischaemic area, and then to confirm the dogma of the heart as terminally differentiated organ. Conversely, peri-lesional mitosis of cardiomyocytes were discovered initially by light microscopy and subsequently confirmed by more sophisticated technologies. Controversial evidence of mechanisms underlying myocardial regeneration has shown that adult cardiomyocytes are renewed through a slow turnover, even in the absence of damage. This turnover is ensured by the activationof rare clusters of progenitor cells interspersed among the cardiac cells functionally mature. Cardiac progenitor cells continuously interactwith each other, with the cells circulating in the vessels of the coronary microcirculation and myocardial cells in auto-/paracrine manner.
Much remains to be understood; however, the limited functional recovery in human beings after myocardial injury clearly demonstrates weak regenerative potential of cardiomyocytes and encourages the development of new approaches to stimulate this process
Endogenous cardiac stem cells.
No full textAbstract In the past few years it has been established that the heart contains a reservoir of stem and progenitor cells. These cells are positive for various stem/progenitor cell markers (Kit, Sca-1, Isl-1, and Side Population (SP) properties). The relationship between the various cardiac stem cells (CSC) and progenitor cells described awaits clarification. Furthermore, they may open a new therapeutic strategies of cardiac repair based on the regeneration potential of cardiac stem cells. Currently, cellular cardiomyoplasty is actively explored as means of regenerating damaged myocardium using several different cell types. CSCs seem a logical cell source to exploit for cardiac regeneration therapy. Their presence into the heart, the frequent co-expression of early cardiac progenitor transcription factors, and the capability for ex vivo and in vivo differentiation toward the cardiac lineages offer promise of enhanced cardiogenicity compared to other cell sources. CSCs, when isolated from various animal models by selection based on c-Kit, Sca-1, and/or MDR1, have shown cardiac regeneration potential in vivo following injection in the infracted myocardium. Recently, we have successfully isolated CSCs from small biopsies of human myocardium and expanded them ex vivo by many folds without losing differentiation potential into cardiomyocytes and vascular cells, bringing autologous transplantation of CSCs closer to clinical evaluation. These cells are spontaneously shed from human surgical specimens and murine heart samples in primary culture. This heterogeneous population of cells forms multi-cellular clusters, dubbed cardiospheres (CSs), in suspension culture. CSs are composed of clonally-derived cells, consist of proliferating c-Kit positive cells primarily in their core and differentiating cells expressing cardiac and endothelial cell markers on their periphery. Although the intracardiac origin of adult myocytes has been unequivocally documented, the potential of an extracardiac source of cells, able to repopulate the lost CSCs in pathological conditions (infarct) cannot be excluded and will be discussed in this review. The delivery of human CSs or of CSs-derived cells into the injured heart of the SCID mouse resulted in engraftment, migration, myocardial regeneration and improvement of left ventricular function. Our method for ex vivo expansion of resident CSCs for subsequent autologous transplantation back into the heart, may give these cell populations, the resident and the transplanted one, the combined ability to mediate myocardial regeneration to an appreciable degree, and may change the way in which cardiovascular disease will be approached in the future
Epigenetic regulation of myocardial homeostasis, self-regeneration and senescence
No full textThe adult myocardium has limited capacity to preserve, renew or rejuvenate itself. The local microenvironment may induce epigenetic changes affecting the survival, proliferation, function and senescence of cardiac cells at rest and following the exposure to different stressors. The cellular response to microenvironment is characterized by the release of ions, oxygen free radicals, auto/paracrine factors and RNAs that drive the magnitude of gene reprogramming through the interaction with specific promoters. The epigenetic alterations may act at transcriptional and post-transcriptional level and change cardiac physiological traits. The abnormal DNA methylation underlies the progressive decay of contractile function and the angiogenic ability; while, the histone acetylation promotes the survival, function and proliferation of cardiac cells in the presence of ischemic microenvironment. At least, the expression and secretion of microRNAs and long noncoding RNAs may regulate the threshold to stress tolerance of adult cardiac cells and induce the matrix turnover as well. Natural or synthetic active compounds effectively modulate the epigenetic state of cardiac cells. Plant foods contain many active compounds with epigenetic properties and might assume a clinical significance as natural cardiac regenerators or rejuvenators. Our review describes novel epigenetic mechanisms that underpin myocardial remodeling, repair/ regeneration or senescence in order to support the development of most effective and reproducible rescue therapy of adult heart
Potential role of mycophenolate mofetil in the management of neuroblastoma patients
No full textIn human neuroblastoma cell lines (LAN5, SHEP and IMR32), mycophenolic acid (MPA) at concentrations (10(-7) -10(-6) M) readily attainable during immunosuppressive therapy with mycophenolate mofetil (Cellcept), induces guanine nucleotide depletion leading to cell cycle arrest and apoptosis through a p53 mediated pathway (up-regulation of p53, p21 and bax and down-regulation of bcl-2 and survivin). MPA-induced apoptosis is also associated to a marked decrease of p27 protein. In the same cell lines MPA, at lower concentrations (50 nM), corresponding to the plasma levels of the active free drug during Cellcept therapy, induces differentiation toward the neuronal phenotype by causing a partial chronic guanine nucleotide depletion. MPA-induced differentiation is not associated to p27 accumulation as occurs using retinoic acid. At a fixed concentration of MPA a higher percentage of apoptotic or differentiated cells is obtained when non dialysed serum substitutes for the dialysed one, due to the higher hypoxanthine concentration in the former (about 10 muM) leading to competition on HPRT-mediated salvage of guanine. At hypoxanthine or oxypurinol concentrations higher than 1 muM (up to 100 mu) no further enhancement of MPA effects was obtained, in agreement with the recently described safety of the allopurinol-mycophenolate mofetil combination in the treatment of hyperuricemia of kidney transplant recipients. The apoptotic effects of MPA do not appear to be significantly increased by the UDP-glucuronosyltransferase inhibitor niflumic acid
Cyclic nucleotides and neuroblastoma differentiation
No full textWe have shown that intracellular cGMP levels increase during retinoic acid- and mycophenolic acid-induced neuroblastoma differentiation and that a 6 days treatment with 1 mM dbcGMP lead LAN5 cell to elaborate a network of neuritic processes suggesting an involvement of cGMP in neuroblastoma differentiation. We have also investigated the effects of some specific inhibitors of phosphodiesterases (PDE1, PDE3, PDE4 and PDE5) on human neuroblastoma (LAN5 and SHEP) growth and differentiation. After six days of incubation in the presence of each specific inhibitor at 10 x IC50 levels a cytostatic and differentiating effect was only observed with the PDE5 inhibitors Zaprinast and MY-5445. The cytostatic effect of these compounds increased increasing their concentrations far above their IC50 levels for PDE5, suggesting that these compounds could act by interfering with other molecular events than direct cGMP-PDE inhibition. No appreciable effect was observed using Dipyridamole, another specific PDE5 inhibitor
Message in a Bottle: Upgrading Cardiac Repair into Rejuvenation
Full text linkIschaemic cardiac disease is associated with a loss of cardiomyocytes and an intrinsic lack of myocardial renewal. Recent work has shown that the heart retains limited cardiomyocyte proliferation, which remains inefficient when facing pathological conditions. While broadly active in the neonatal mammalian heart, this mechanism becomes quiescent soon after birth, suggesting loss of regenerative potential with maturation into adulthood. A key question is whether this temporary regenerative window can be enhanced via appropriate stimulation and further extended. Recently the search for novel therapeutic approaches for heart disease has centred on stem cell biology. The “paracrine effect” has been proposed as a promising strategy to boost endogenous reparative and regenerative mechanisms from within the cardiac tissue by exploiting the modulatory potential of soluble stem cell-secreted factors. As such, growing interest has been specifically addressed towards stem/progenitor cell-secreted extracellular vesicles (EVs), which can be easily isolated in vitro from cell-conditioned medium. This review will provide a comprehensive overview of the current paradigm on cardiac repair and regeneration, with a specific focus on the role and mechanism(s) of paracrine action of EVs from cardiac stromal progenitors as compared to exogenous stem cells in order to discuss the optimal choice for future therapy. In addition, the challenges to overcoming translational EV biology from bench to bedside for future cardiac regenerative medicine will be discussed
Evolving Strategies for Extracellular Vesicles as Future Cardiac Therapeutics: From Macro- to Nano-Applications
No full textCardiovascular disease represents the foremost cause of mortality and morbidity worldwide, with a steadily increasing incidence due to the growth of the ageing population. Cardiac dysfunction leading to heart failure may arise from acute myocardial infarction (MI) as well as inflammatory- and cancer-related chronic cardiomyopathy. Despite pharmacological progress, effective cardiac repair represents an unmet clinical need, with heart transplantation being the only option for end-stage heart failure. The functional profiling of the biological activity of extracellular vesicles (EVs) has recently attracted increasing interest in the field of translational research for cardiac regenerative medicine. The cardioprotective and cardioactive potential of human progenitor stem/cell-derived EVs has been reported in several preclinical studies, and EVs have been suggested as promising paracrine therapy candidates for future clinical translation. Nevertheless, some compelling aspects must be properly addressed, including optimizing delivery strategies to meet patient needs and enhancing targeting specificity to the cardiac tissue. Therefore, in this review, we will discuss the most relevant aspects of the therapeutic potential of EVs released by human progenitors for cardiovascular disease, with a specific focus on the strategies that have been recently implemented to improve myocardial targeting and administration routes
Exosomes from human cardiac progenitor cells, but not those from patient-matched bone marrow-derived mesenchymal stem cells,improve cardiac function after myocardial infarction in vivo
No full textBackground: Both human cardiac progenitor cells (CPC) and bone marrow-derived mesenchymal stem cells (MSC) have been tested in clinical trials of cell transplantation in patients with myocardial infarction (MI). We have recently shown that Exosomes (secreted nanovesicles; Exo) from CPC account for cardioprotective and proangiogenic activities of these cells both in vitro and in vivo. This study aimed to compare Exo-CPC and Exo-MSC in terms of cardioprotective effects and functional improvement after MI. The role of microRNA (miRNA) and ischemic preconditioning (IPC) were assessed.
Methods: CPC and MSC were derived from right atrial appendage and bone aspirate from patients undergoing heart valve surgery. Samples from both tissues were obtained for a patient-matched comparison of Exo from the two cell lines. Exo were isolated by differential ultracentrifugation of conditioned media from CPC or MSC. Anti-apoptotic and proangiogenic effects of Exo-CPC and Exo-MSC were assessed in vitro and compared with Exo from human dermal fibroblast cell line (Exo-F). IPC was performed by subjecting CPC or MSC to two short rounds of hypoxia and glucose deprivation. miRNA profiles of Exo were assessed by real-time PCR. Exo-CPC and Exo-MSC from 8 patients were injected intramyocardially in 8 rats each after permanent ligation of the left anterior descending coronary artery. Left ventricular ejection fraction (LVEF) was measured by echocardiography 1 and 4 weeks after MI.
Results: Although both Exo-CPC and Exo-MSC inhibited cardiomyocyte (CM) apoptosis after serum starvation in vitro if compared with Exo-F, Exo-CPC showed higher efficacy (21±4% Exo-CPC; 28±4% Exo-MSC; 40±5% Exo-F). IPC of Exo-producing cells further reduced numbers of apoptotic CM (17±1% Exo-CPC; 23±3% Exo-MSC). Exo-CPC, but not Exo-F, were proangiogenic in HUVEC cells. miR-210, miR132 and miR-146a were among the most highly enriched miRNA in Exo-CPC. CM transfected with miR-210 or miR-132 mimics showed increased tolerance to apoptosis, whereas siRNA specific for these miRNA had opposite effects. In vivo, LVEF was significantly improved in hearts injected with Exo-CPC compared to those injected with patient-matched Exo-MSC both at 1 week (87.0±9.9% vs 61.1±11.9; p<0.05) and 4 weeks after MI (75.4±8.9% vs 58.7±18.4%; p<0.05).
Conclusion: These results from patient-matched analyses show, for the first time, that Exo-CPC is superior to Exo-MSC at inhibiting CM apoptosis in vitro, and at improving cardiac function after MI in vivo. As a cell-free approach, Exo could streamline clinical translation of regenerative heart therapy
Exosomes from Human Cardiac Progenitor Cells Preserve Cardiac Function Long Term after Myocardial Infarction
No full textIntroduction: Recent evidence suggests cardiac progenitor cells (CPC) may improve cardiac function after injury. The
underlying mechanisms are indirect, but their mediators remain unidentified. Exosomes (Exo) act as paracrine signalling
mediators. Here we report that Exo secreted by human CPC are crucial cardioprotective agents that improve left
ventricular ejection fraction (LVEF %) in long term animal model of infarct.
Methods: Medium from CPC or normal human dermal fibroblasts (NHDF) was conditioned for 5-7 days and subjected to
differential centrifugation for Exo isolation. Exo from CPC (Exo-CPC) were tested in-vitro for their functional activity such
as anti-apoptotic and pro-angiogenic effects and compared with Exo from NHDF (Exo-F). The content of micro-RNA
(miRNA) has been analysed by real-time PCR in Exo-CPC vs Exo-F. Exo-CPC derived from six patients were pooled and
intramyocardially injected in-vivo in animal model of permanent left anterior descending (LAD) coronary ligation. One and
four weeks after injection LVEF was evaluated by echocardiography and hearts were processed for histological analysis.
Results: Exo-CPC inhibited apoptosis in cardiomyocytes, while enhancing tube formation in human endothelial cells invitro
compared to Exo-F. Exo-CPC were enriched in miR-210, miR-132, miR-146a, and miR-181a compared to Exo-F. In
gain-of-function studies, miR-210 and miR-146a inhibited apoptosis in cardiomyocytes by downregulating their targets
ephrinA3/PTP1b and Nox4 respectively. miR-132 downregulated its target RasGAP-p120 and enhanced angiogenesis.
Moreover, Exo-CPC, but not Exo-F, downregulated anti-apoptotic factors in cardiomyocytes. Infarcted hearts injected
with Exo-CPC significantly preserved the LVEF after one week (84.00±1.6%) and the effect was preserved after four
weeks (80.57±2.3%) compared with animals injected with Exo-F (60.71±7.4%; 48.00±4.6% one and four weeks
respectively). Moreover Exo-CPC injected hearts showed significantly reduced scar size (6.7±2.0% Exo-CPC vs
19.25±3.4% Exo-F).
Summary/Conclusion: Exo are the active component of the paracrine secretion of human CPC. They are enriched in
miRNA with cardioprotective and proangiogenic activities. Exo-CPC preserve heart function in a long term animal model
of permanent LAD ligation. As a cell-free approach, Exo could circumvent many of the limitations of cell transplantation
Low levels of mycophenolic acid induce differentiation of human neuroblastoma cell lines
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