Intrapericardial procedures for cardiac regeneration by stem cells

In view of the only modest functional and anatomical improvements achieved by bone marrow-derived cell transplantation in patients with heart disease, the question was addressed whether the intracoronary, transcoronary–venous, and intramyocardial delivery routes are adequate. It is hypothesized that an intrapericardial delivery of stem cells or activators of resident cardiac stem cells increases therapeutic benefits. From such an intrapericardial depot, cells or modulating factors, such as thymosin β4 or Ac-SDKP, are expected to reach the myocardium with sustained kinetics. Novel tools which provide access to the pericardial space even in the absence of pericardial effusion are, therefore, described. When the pericardium becomes attached to the suction head (monitored by an increase in negative pressure), the pericardium is lifted from the epicardium (“AttachLifter”). The opening of the suction head (“Attacher”) is narrowed by flexible clamps which grab the tissue and improve the vacuum seal in the case of uneven tissue. A ridge, i.e.,“needle guidance”, on the suction head excludes injury to the epicardium, whereby the pericardium is punctured by a needle which resides outside the suction head. A fiberscope can be used to inspect the pericardium prior to puncture. Based on these procedures, the role of the pericardial space and the presence of pericardial effusion in cardiac regeneration can be assessed.     

Myocardial regeneration by activation of multipotent cardiac stem cells in ischemic heart failure

In this study, we tested whether the human heart possesses a cardiac stem cell (CSC) pool that promotes regeneration after infarction. For this purpose, CSC growth and senescence were measured in 20 hearts with acute infarcts, 20 hearts with end-stage postinfarction cardiomyopathy, and 12 control hearts. CSC number increased markedly in acute and, to a lesser extent, in chronic infarcts. CSC growth correlated with the increase in telomerase-competent dividing CSCs from 1.5% in controls to 28% in acute infarcts and 14% in chronic infarcts. The CSC mitotic index increased 29-fold in acute and 14-fold in chronic infarcts. CSCs committed to the myocyte, smooth muscle, and endothelial cell lineages increased approximately 85-fold in acute infarcts and approximately 25-fold in chronic infarcts. However, p16(INK4a)-p53-positive senescent CSCs also increased and were 10%, 18%, and 40% in controls, acute infarcts, and chronic infarcts, respectively. Old CSCs had short telomeres and apoptosis involved 0.3%, 3.8%, and 9.6% of CSCs in controls, acute infarcts, and chronic infarcts, respectively. These variables reduced the number of functionally competent CSCs from approximately 26,000/cm3 of viable myocardium in acute to approximately 7,000/cm3 in chronic infarcts, respectively. In seven acute infarcts, foci of spontaneous myocardial regeneration that did not involve cell fusion were identified. In conclusion, the human heart possesses a CSC compartment, and CSC activation occurs in response to ischemic injury. The loss of functionally competent CSCs in chronic ischemic cardiomyopathy may underlie the progressive functional deterioration and the onset of terminal failure.     

间充质干细胞移植和心肌再生治疗

间充质干细胞是一种具有多向分化潜能的成体干细胞,在体内、体外可以被诱导分化为心肌细胞。心肌梗死造成大量的功能心肌细胞丧失,引起心室重构和功能失常,导致心脏功能衰竭。间充质干细胞心肌梗死后体内移植可以“归巢”到梗死区,定向分化为心肌细胞,改善受损心脏功能,被认为是细胞移植的理想种子细胞。本文综述间充质干细胞生物学特性及其体内移植心肌再生治疗心肌梗死的最新研究进展。     

骨髓间充质干细胞移植在心脏再生医学中的分子机制

骨髓间充质干细胞(BMSCs)移植治疗心血管疾病已经在不少基础研究和临床试验中证实了其有效性.但是,其改善心功能的机制仍有较多争议,该作用除与BMSCs向心肌样细胞分化有关外,还可能与其促血管生成、抑制心肌细胞凋亡、改善心脏重构、分泌大量有益细胞因子有关.本综述将重点总结目前关于BMSCs在心脏再生医学中应用的相关分子机制的假说,并探讨对各种假说的挑战.     

Resident human cardiac stem cells: role in cardiac cellular homeostasis and potential for myocardial regeneration

Current treatments for myocardial infarction have significantly reduced the acute mortality of ischemic cardiomyopathy. This reduction has resulted in the survival of a large cohort of patients left with a significant 'myocyte deficit'. Once this deficit leads to heart failure there is no available therapy to improve long-term cardiac function. Recent developments in stem cell biology have focused on the possibility of regenerating contractile myocardial tissue. Most of these approaches have entailed the transplantation of exogenous cardiac-regenerating cells. Recently, we and others have reported that the adult mammalian myocardium, including that in humans, contains a small pool of cardiac stem and progenitor cells (CSCs) that can replenish the cardiomyocyte population and, in some cases, the coronary microcirculation. The human CSCs (hCSCs) are involved in maintaining myocardial cell homeostasis throughout life and participate in remodeling in cardiac pathology. They can be isolated, propagated and cloned. The progeny of a single cell clone differentiates in vitro and in vivo into myocytes, smooth muscle and endothelial cells. Surprisingly, in response to different forms of stress, hCSCs acquire a senescent, dysfunctional phenotype. Strikingly, these nonfunctional CSCs constitute around 50% of the total CSC pool in older individuals-those most likely to be candidates for hCSC-based myocardial regeneration. Therefore, the challenge to develop clinically effective therapies of myocardial regeneration is twofold: to produce the activation of the hCSCs in situ in order to obviate the need for cell transplantation, and to elucidate the mechanisms responsible for hCSC senescence in order to prevent or reverse its development.     

干细胞再生心肌研究进展

干细胞移植使真正修复和再生心肌成为可能,是治疗缺血性心肌病的一种新方法.目前试验研究表明,由于大量移植的干细胞不能存留在心肌组织,细胞活性较低,再生心肌的能力被明显削弱.如何运用更为优化的干细胞移植策略和现实可行的方法,解决移植后干细胞再生心肌的效率成为细胞治疗的关键.此文从再生心肌的干细胞来源和选择、移植干细胞的方式...     

心脏原位干细胞修复心肌的研究

心尖和心房内存在少量的原位干细胞,在生理情况下心脏原位干细胞(cardiac stem cells,CSCs)对于维持心肌细胞稳态有重要作用.该文对CSCs用于心脏再生治疗的优势,体外扩增CSCs的技术,心脏修复机制(包括分化机制和旁分泌机制),各种心脏疾病中CSCs的变化以及目前CSCs治疗遇到的问题作一简介.     

Growth-factor-mediated cardiac stem cell activation in myocardial regeneration

The concept of an intrinsic regenerative capacity of the adult mammalian myocardium owing to the presence of cardiac stem cells (CSCs) in the atria and ventricles is starting to be accepted by the cardiovascular research community. The identification of this cell population has improved the prospects for developing successful clinical protocols for human myocardial regeneration. In the normal adult myocardium, only a small fraction of CSCs undergo amplification and differentiation to replace the parenchymal cells lost by normal wear and tear. Physiological or pathological stimuli cause substantial activation of CSCs, which is mediated by a paracrine feedback loop between myocytes and CSCs. In response to stress, the myocytes produce growth factors and cytokines, for which CSCs have receptors, and autocrine, self-sustaining activation of growth-factor production is simultaneously triggered in the CSCs. These findings from human and animal studies led us to test whether in situ activation of CSCs by growth factors would be as effective as transplantation of CSCs into the regenerating myocardium after ischemia in an animal model that has relevance to humans. In a porcine model, we produced extensive and functionally relevant myocardial regeneration. Here, we discuss the properties of endogenous myocardial stem cells that might be exploited to produce clinical myocardial regeneration without the need for cell transplantation.     

Resident cardiac stem cells

The search for sources of stem/progenitor cells the use of which has a potential to affect course of ischemic heart disease and chronic heart failure is conducted nowadays in many countries. Resident cardiac stem cells (CSC) were revealed during recent years on the basis of expression of c-kit, sca-1, MDR1, and islet-1 markers. In vitro experiments demonstrated possibility of their differentiation into cardiomyocytes, smooth muscle cell and endothelial cells. Introduction of CSC in injured myocardium in animals facilitated its partial repair and short term improvement of cardiac function. This holds promise for the use of these cells in the future. In the review we have attempted to summarize literature data on resident CSC and their application for the treatment of heart diseases.     

Human cardiac stem cells

The identification of cardiac progenitor cells in mammals raises the possibility that the human heart contains a population of stem cells capable of generating cardiomyocytes and coronary vessels. The characterization of human cardiac stem cells (hCSCs) would have important clinical implications for the management of the failing heart. We have established the conditions for the isolation and expansion of c-kit-positive hCSCs from small samples of myocardium. Additionally, we have tested whether these cells have the ability to form functionally competent human myocardium after infarction in immunocompromised animals. Here, we report the identification in vitro of a class of human c-kit-positive cardiac cells that possess the fundamental properties of stem cells: they are self-renewing, clonogenic, and multipotent. hCSCs differentiate predominantly into cardiomyocytes and, to a lesser extent, into smooth muscle cells and endothelial cells. When locally injected in the infarcted myocardium of immunodeficient mice and immunosuppressed rats, hCSCs generate a chimeric heart, which contains human myocardium composed of myocytes, coronary resistance arterioles, and capillaries. The human myocardium is structurally and functionally integrated with the rodent myocardium and contributes to the performance of the infarcted heart. Differentiated human cardiac cells possess only one set of human sex chromosomes excluding cell fusion. The lack of cell fusion was confirmed by the Cre-lox strategy. Thus, hCSCs can be isolated and expanded in vitro for subsequent autologous regeneration of dead myocardium in patients affected by heart failure of ischemic and nonischemic origin.     

Bone regeneration and Mesenchymal stem cells

Bone marrow mesenchymal stem cells have been considered to differentiate into cells in bone, cartilage, tendon, muscle, and fat. Further analyses revealed that these cell also give rise to myocardial cells, oval cells and nerve cells, indicating high plasticity of these cells. Recent researches have been focused to utilize these cells to regenerate not only bone but also the life-maintaining major organs. As a cell source for the future regeneration of multiple organs, regeneration of the bone marrow is critical and thus studies on the process of bone marrow regeneration will benefit not only bone physiology field alone but also that of many other organs.     

Human embryonic stem cells for myocardial regeneration

Terminally differentiated adult cardiomyocytes have limited regenerative capacity and therefore any significant cell loss may result in the development of progressive heart failure. Cell replacement therapy is a promising new approach for myocardial repair but has been limited by the paucity of cell sources for functional human cardiomyocytes. The recent establishment of the human pluripotent embryonic stem (ES) cell lines may present a novel solution for this cell-sourcing problem. The ES lines were derived from human blastocysts and were shown to be capable of continuous undifferentiated proliferation, in vitro, while retaining the capability to form derivatives of all three germ layers. More recently, a reproducible cardiomyocyte differentiation system was established using these unique cells. The current review describes the derivation and properties of human ES cells and the characteristics of the cardiomyocytes derived using this unique differentiating system. The possible applications in several research and clinical areas are discussed as well as the steps required to fully harness the potential of this new technology in the fields of myocardial cell replacement and tissue engineering.     

Empowering adult stem cells for myocardial regeneration

Treatment strategies for heart failure remain a high priority for ongoing research due to the profound unmet need in clinical disease coupled with lack of significant translational progress. The underlying issue is the same whether the cause is acute damage, chronic stress from disease, or aging: progressive loss of functional cardiomyocytes and diminished hemodynamic output. To stave off cardiomyocyte losses, a number of strategic approaches have been embraced in recent years involving both molecular and cellular approaches to augment myocardial structure and performance. Resultant excitement surrounding regenerative medicine in the heart has been tempered by realizations that reparative processes in the heart are insufficient to restore damaged myocardium to normal functional capacity and that cellular cardiomyoplasty is hampered by poor survival, proliferation, engraftment, and differentiation of the donated population. To overcome these limitations, a combination of molecular and cellular approaches must be adopted involving use of genetic engineering to enhance resistance to cell death and increase regenerative capacity. This review highlights biological properties of approached to potentiate stem cell-mediated regeneration to promote enhanced myocardial regeneration, persistence of donated cells, and long-lasting tissue repair. Optimizing cell delivery and harnessing the power of survival signaling cascades for ex vivo genetic modification of stem cells before reintroduction into the patient will be critical to enhance the efficacy of cellular cardiomyoplasty. Once this goal is achieved, then cell-based therapy has great promise for treatment of heart failure to combat the loss of cardiac structure and function associated with acute damage, chronic disease, or aging.     

Haematopoietic stem cells participate in muscle regeneration

It has previously been shown that bone marrow cells contribute to skeletal muscle regeneration, but the nature of marrow cell(s) involved in this process is unknown. We used an immunocompetent and an immunocompromised model of bone marrow transplantation to characterize the type of marrow cells participating regenerating skeletal muscle fibres. Animals were transplanted with different populations of marrow cells from Green Fluorescent Protein (GFP) transgenic mice and the presence of GFP(+) muscle fibres were evaluated in the cardiotoxin-injured tibialis anterior muscles. GFP(+) muscle fibres were found mostly in animals that received either CD45(-), lineage(-), c-Kit(+), Sca-1(+) or Flk-2(+) populations of marrow cells, suggesting that haematopoietic stem cells (HSC) rather than mesenchymal cells or more differentiated haematopoietic cells are responsible for the formation of GFP(+) muscle fibres. Mac-1 positive population of marrow cells was also associated with the emergence of GFP(+) skeletal muscle fibres. However, most of this activity was limited to either Mac-1(+) Sca(+) or Mac-1(+)c-Kit(+) cells with long-term haematopoietic repopulation capabilities, indicating a stem cell phenotype for these cells. Experiments in the immunocompromised transplant model showed that participation of HSC in the skeletal muscle fibre formation could occur without haematopoietic chimerism.