成体心肌干细胞的研究进展

研究表明,成熟机体的心脏组织中,存在具有高度自我更新能力和特异性心肌分化潜能的成体心肌干细胞,其能够分化为心肌细胞、内皮细胞及平滑肌细胞等心脏结构细胞。成体心肌干细胞是目前被认为最有希望以完全心肌再生应用于缺血性心脏病及其他终末期心脏病替代治疗的干细胞类型。该文综述了成体心肌干细胞的定义和分布、分类和功能、在心肌微环境中的影响因素以及目前研究中存在的问题与展望。     

干细胞在心肌梗死治疗中的研究进展

细胞移植治疗的出现为众多心衰患者带来了新的希望,干细胞是主要的细胞来源。胚胎干细胞能分化为真正的心肌细胞,是心肌修复治疗中一种理想的细胞来源,但其受免疫和伦理学方面的限制；成体干细胞作为自体细胞移植治疗对研究者来说则具有很大的吸引力,但其分化潜能则不如胚胎干细胞。目前,用于基础研究和临床试验的成体干细胞主要来源于骨髓,且认为只有骨髓间充质干细胞能分化为心肌细胞。本文主要讨论了不同于细胞移植在受损心肌修复治疗中的作用。     

骨髓成体干细胞在心血管疾病发病中的病理生理意义

成体干细胞研究的深入进一步揭示了一些常见心血管疾病的病理生理机制,它们既能参与心肌再生、血管形成和损伤动脉再内皮化等疾病的修复过程,也能促进动脉粥样硬化、再狭窄等疾病的进展过程。骨髓是成体干细胞研究较为深入的组织,本文就骨髓成体干细胞在常见心血管疾病发病中的生理和病理意义作一综述。     

心肌再生生物学机制研究现状

心肌组织一直被认为是不可再生组织,对其损伤后的治疗一般也只能采用保守方法.近年来,在成年大鼠心脏中发现的Lin-c-kitPOS细胞有向心肌细胞分化的潜力,说明成年机体心肌组织中仍可能存在干细胞;而对胚胎干细胞及骨髓干细胞在修复损伤心肌方面的相关研究也显示这些干细胞可通过分化成心肌细胞而改善心肌功能;对多种细胞因子的广泛研究也发现其能促进心肌细胞的分裂增生,多种研究结果提示心肌再生并非不可能.虽然在后续的几个大规模临床前研究中未能取得令人期待的结果,以及伦理问题和机体对不同干细胞的免疫排斥反应等问题仍待解决,但心肌再生的研究前景仍然光明.     

心肌损伤、心肌再生与心力衰竭(二)

4干细胞源性细胞 干细胞有几种不同的来源,包括胚胎、胎儿和成人组织的干细胞.虽然胚胎干细胞认为是功能细胞,成人干细胞以前认为仅在它们残存的组织中增生.最近的研究表明,来自其他器官系统的祖细胞在缺乏内源性细胞再生能力的情况下,能够再生心肌组织.循环和骨髓中的干细胞能够在移植心肌中再生心肌和血管.这些研究提示这种祖细胞的移植具有治疗的价值.下面将讨论成人胚胎及胎儿细胞用于心血管系统的治疗潜能.     

心肌干细胞与心肌修复

心肌干细胞有c-kit 、MDR 和Sca-1 等多能干细胞的表面标志,体外实验证明,心肌干细胞可以分化为心肌细胞.在缺血性心脏病中,缺血、梗死区附近的心肌干细胞可以迁移、增殖,进行心肌修复.心肌干细胞还与心室肥厚和心肌衰老有关.这为心脏疾病的治疗提供了新思路:动员原位心肌干细胞.     

成体干细胞在心血管疾病中的研究进展

近年来,干细胞尤其是成体干细胞的研究进展,给心血管疾病的治疗带来了新的希望。骨髓间质干细胞、脂肪源性干细胞、造血干细胞、骨骼肌成肌细胞、心肌干细胞等已被应用于心肌的再生。而干细胞与基因治疗的结合,带来了更广阔的应用前景。现对成体干细胞移植在心血管疾病方面研究中取得的成就、有待解决的问题以及临床应用前景作一综述。     

心肌再生生物学机制研究现状

心肌组织一直被认为是不可再生组织,对其损伤后的治疗一般也只能采用保守方法。近年来,在成年大鼠心脏中发现的Lin—c—kitPOS细胞有向心肌细胞分化的潜力,说明成年机体心肌组织中仍可能存在干细胞;而对胚胎干细胞及骨髓干细胞在修复损伤心肌方面的相关研究也显示这些干细胞可通过分化成心肌细胞而改善心肌功能;对多种细胞因子的广泛研究也发现其能促进心肌细胞的分裂增生,多种研究结果提示心肌再生并非不可能。虽然在后续的几个大规模临床前研究中未能取得令人期待的结果,以及伦理问题和机体对不同干细胞的免疫排斥反应等问题仍待解决,但心肌再生的研究前景仍然光明。     

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...     

心肌干细胞与心肌修复

心肌干细胞有c-kit~+、MDR+和Sca-1~+等多能干细胞的表面标志,体外实验证明,心肌干细胞可以分化为心肌细胞。在缺血性心脏病中,缺血、梗死区附近的心肌干细胞可以迁移、增殖,进行心肌修复。心肌干细胞还与心室肥厚和心肌衰老有关。这为心脏疾病的治疗提供了新思路：动员原位心肌干细胞。     

Epithelial-mesenchymal transition of epicardial mesothelium is a source of cardiac CD117-positive stem cells in adult human heart

Epithelial-mesenchymal transition is implicated in the remodelling of tissues during development and in the adult life. In the heart, it gives origin to progenitors of fibroblasts, coronary endothelium, smooth muscle cells, and cardiomyocytes. Moreover, epicardially-derived cells determine myocardial wall thickness and Purkinje fibre network. Recently, the presence of numerous cardiac stem cells in the subepicardium of the adult human heart has been described and the hypothesis that epicardially-derived cells can contribute to the population of cardiac stem cells in the adult heart has been advanced. In an effort to test this hypothesis and establish a possible link between epicardium, epicardially-derived cells and cardiac stem cells in the adult human heart we have examined epicardial mesothelial cells in the normal and pathological adult human heart with ischemic cardiomyopathy in vivo and we have induced and documented their epithelial-mesenchymal transition in vitro. Noticeably, epicardial cells were missing from the surface of pathological hearts and the cells with the expression of epithelial and mesenchymal markers populated thick subepicardial space. When the fragments of epicardium from the normal hearts were cultured on the specific substrate formed by extracellular matrix derived from cardiac fibroblasts, we obtained the outgrowth of the epithelial sheet with the mRNA and protein expression characteristic of epicardium. TGFβ induced cellular and molecular changes typical of epithelial-mesenchymal transition. Moreover, the epicardially-derived cells expressed CD117 antigen. Thus, this study provides evidence that cardiac stem cells can originate from epithelial-mesenchymal transition of the epicardial cells in the adult human heart.     

Embryonic Template-Based Generation and Purification of Pluripotent Stem Cell-Derived Cardiomyocytes for Heart Repair

Cardiovascular disease remains a leading cause of death in Western countries. Many types of cardiovascular diseases are due to a loss of functional cardiomyocytes, which can result in irreversible cardiac failure. Since the adult human heart has limited regenerative potential, cardiac transplantation is still the only effective therapy to address this cardiomyocyte loss. However, drawbacks, such as immune rejection and insufficient donor availability, are limiting this last-resort solution. Recent developments in the stem cell biology field have improved the potential of cardiac regeneration. Improvements in reprogramming strategies of differentiated adult cells into induced pluripotent stem cells, together with increased efficiency of directed differentiation of pluripotent stem cells toward cardiac myocytes, have brought cell-based heart muscle regeneration a few steps closer to the clinic. In this review, we outline the status of research on cardiac regeneration with a focus on directed differentiation of pluripotent stem cells toward the cardiac lineage.     

Cardiogenic differentiation and transdifferentiation of progenitor cells

In recent years, cell transplantation has drawn tremendous interest as a novel approach to preserving or even restoring contractile function to infarcted hearts. A typical human infarct involves the loss of approximately 1 billion cardiomyocytes, and, therefore, many investigators have sought to identify endogenous or exogenous stem cells with the capacity to differentiate into committed cardiomyocytes and repopulate lost myocardium. As a result of these efforts, dozens of stem cell types have been reported to have cardiac potential. These include pluripotent embryonic stem cells, as well various adult stem cells resident in compartments including bone marrow, peripheral tissues, and the heart itself. Some of these cardiogenic progenitors have been reported to contribute replacement muscle through endogenous reparative processes or via cell transplantation in preclinical cardiac injury models. However, considerable disagreement exists regarding the efficiency and even the reality of cardiac differentiation by many of these stem cell types, making these issues a continuing source of controversy in the field. In this review, we consider approaches to cell fate mapping and establishing the cardiac phenotype, as well as the present state of the evidence for the cardiogenic and regenerative potential of the major candidate stem cell types.     

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.     

Isolation and expansion of functionally-competent cardiac progenitor cells directly from heart biopsies

The adult heart contains reservoirs of progenitor cells that express embryonic and stem cell-related antigens. While these antigenically-purified cells are promising candidates for autologous cell therapy, clinical application is hampered by their limited abundance and tedious isolation methods. Methods that involve an intermediate cardiosphere-forming step have proven successful and are being tested clinically, but it is unclear whether the cardiosphere step is necessary. Accordingly, we investigated the molecular profile and functional benefit of cells that spontaneously emigrate from cardiac tissue in primary culture. Adult Wistar-Kyoto rat hearts were minced, digested and cultured as separate anatomical regions. Loosely-adherent cells that surround the plated tissue were harvested weekly for a total of five harvests. Genetic lineage tracing demonstrated that a small proportion of the direct outgrowth from cardiac samples originates from myocardial cells. This outgrowth contains sub-populations of cells expressing embryonic (SSEA-1) and stem cell-related antigens (c-Kit, abcg2) that varied with time in culture but not with the cardiac chamber of origin. This direct outgrowth, and its expanded progeny, underwent marked in vitro angiogenic/cardiogenic differentiation and cytokine secretion (IGF-1, VGEF). In vivo effects included long-term functional benefits as gauged by MRI following cell injection in a rat model of myocardial infarction. Outgrowth cells afforded equivalent functional benefits to cardiosphere-derived cells, which require more processing steps to manufacture. These results provide the basis for a simplified and efficient process to generate autologous cardiac progenitor cells (and mesenchymal supporting cells) to augment clinically-relevant approaches for myocardial repair.     

Human progenitor cells derived from cardiac adipose tissue ameliorate myocardial infarction in rodents

Myocardial infarction caused by vascular occlusion results in the formation of nonfunctional fibrous tissue. Cumulative evidence indicates that cell therapy modestly improves cardiac function; thus, novel cell sources with the potential to repair injured tissue are actively sought. Here, we identify and characterize a cell population of cardiac adipose tissue-derived progenitor cells (ATDPCs) from biopsies of human adult cardiac adipose tissue. Cardiac ATDPCs express a mesenchymal stem cell-like marker profile (strongly positive for CD105, CD44, CD166, CD29 and CD90) and have immunosuppressive capacity. Moreover, cardiac ATDPCs have an inherent cardiac-like phenotype and were able to express de novo myocardial and endothelial markers in vitro but not to differentiate into adipocytes. In addition, when cardiac ATDPCs were transplanted into injured myocardium in mouse and rat models of myocardial infarction, the engrafted cells expressed cardiac (troponin I, sarcomeric α-actinin) and endothelial (CD31) markers, vascularization increased, and infarct size was reduced in mice and rats. Moreover, significant differences between control and cell-treated groups were found in fractional shortening and ejection fraction, and the anterior wall remained significantly thicker 30 days after cardiac delivery of ATDPCs. Finally, cardiac ATDPCs secreted proangiogenic factors under in vitro hypoxic conditions, suggesting a paracrine effect to promote local vascularization. Our results indicate that the population of progenitor cells isolated from human cardiac adipose tissue (cardiac ATDPCs) may be valid candidates for future use in cell therapy to regenerate injured myocardium.     

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.     

骨髓间质干细胞静脉移植治疗大鼠急性心肌梗死的实验研究

目的:观察多次静脉移植骨髓间质干细胞治疗心肌梗死的可行性及对心肌梗死后心功能的影响。方法:骨髓间质干细胞培养传至5代后,制备成终浓度为4×109个/L的悬液备用。将40只SD大鼠均结扎冠状动脉左前降支,建立急性心肌梗死模型后,随机分为3组:①对照组(10只):只静脉注射0.85%氯化钠溶液;②静脉移植组(15只):心肌梗死模型制备后24h,从尾静脉注射骨髓间质干细胞0.5ml(含2×109个/L)连续7d;③心外膜移植组(15只):心肌梗死模型制备后1~3h,于梗死周边区(心肌颜色苍白区周边)分6点注射骨髓间质干细胞,每点50μl。5周后,观察3组的生存情况及心脏的结构功能。结果:心肌梗死对照组有3只大鼠死亡,其他组无死亡。与对照组相比,静脉移植组、心外膜移植组的左室结构与功能明显改善(P<0·05),静脉移植组与心外膜移植组差异无统计学意义(P>0·05)。结论:骨髓间质干细胞可以在体外大量扩增,异体输入无不良反应,静脉注射与直接心肌注射无明显差别,方法可行。     

Adult stem cells and tissue repair

Recently, adult stem cells originating from bone marrow or peripheral blood have been suggested to contribute to repair and genesis of cells specific for liver, cardiac and skeletal muscle, gut, and brain tissue. The mechanism involved has been termed transdifferentiation, although other explanations including cell fusion have been postulated. Using adult stem cells to generate or repair solid organ tissue obviates the immunologic, ethical, and teratogenic issues that accompany embryonic stem cells.     

Cardiac stem cells: isolation, expansion and experimental use for myocardial regeneration

Cellular cardiomyoplasty (myogenic cell grafting) is actively being explored as a novel method to regenerate damaged myocardium. The adult human heart contains small populations of indigenous committed cardiac stem cells or multipotent cardiac progenitor cells, identified by their cell-surface expression of c-kit (the receptor for stem cell factor), P-glycoprotein (a member of the multidrug resistance protein family), and Sca-1 (stem cell antigen 1, a mouse hematopoietic stem cell marker) or a Sca-1-like protein. Cardiac stem cells represent a logical source to exploit in cardiac regeneration therapy because, unlike other adult stem cells, they are likely to be intrinsically programmed to generate cardiac tissue in vitro and to increase cardiac tissue viability in vitro. Cardiac stem cell therapy could, therefore, change the fundamental approach to the treatment of heart disease.