Possibilities of investigation and clinical application of adult human stem cells

Multipotent adult tissue stem cells have high plasticity and transdifferentiation ability. The stem cell therapy can be the solution of curing many severe diseases such as osteogenesis imperfecta, hepatic failure, heart muscle damage after myocardial infarction, I-type diabetes, variety of central nervous system disorders such as brain injury, stroke, Parkinson's disease and other neurodegenerative disorders. Isolation of certain types of stem cells is solved nowadays, but low frequency of these cells and lack of special identification markers make their isolation and search more difficult. The more and more developed in vitro cell culture technologies, the widespread macromolecule amplification and examination techniques of molecular biology and the gene technology tools for genetic modification of stem (and other) cells contribute to research and therapeutic applications of stem cells. Transfer of new genetic material to stem cells and expression of the gene product in daughter cells--because missing or damaged genes can be replaced--is an exiting approach of the treatment of congenital (enzyme deficiencies) and acquired human diseases (cancers).     

Stem cell sources for cardiac regeneration

Cell-based cardiac repair has the ambitious aim to replace the malfunctioning cardiac muscle developed after myocardial infarction, with new contractile cardiomyocytes and vessels. Different stem cell populations have been intensively studied in the last decade as a potential source of new cardiomyocytes to ameliorate the injured myocardium, compensate for the loss of ventricular mass and contractility and eventually restore cardiac function. An array of cell types has been explored in this respect, including skeletal muscle, bone marrow derived stem cells, embryonic stem cells (ESC) and more recently cardiac progenitor cells. The best-studied cell types are mouse and human ESC cells, which have undisputedly been demonstrated to differentiate into cardiomyocyte and vascular lineages and have been of great help to understand the differentiation process of pluripotent cells. However, due to their immunogenicity, risk of tumor development and the ethical challenge arising from their embryonic origin, they do not provide a suitable cell source for a regenerative therapy approach. A better option, overcoming ethical and allogenicity problems, seems to be provided by bone marrow derived cells and by the recently identified cardiac precursors. This report will overview current knowledge on these different cell types and their application in cardiac regeneration and address issues like implementation of delivery methods, including tissue engineering approaches that need to be developed alongside.     

Mesenchymal stem cells as potential source cartilage repair

Articular cartilage damaged by disease or trauma has a limited capacity for regeneration. The end stage of cartilage loss frequently leads to osteoarthritis resulting in a significantly decreased quality of life in millions of people. The surgical treatment of articular cartilage injury has always posed difficult problems for orthopedic surgeons and regarding long-term outcomes the currently available methods are unsatisfactory. The main lack of the applied methods is the appearance of the mechanically inadequate resident fibrocartilage instead of hyalin cartilage in the place of the cartilage defect. To find reliable methods for early repair of cartilage injuries seems of huge importance. Using techniques of tissue engineering, artificial cartilage fabricated in vitro has been applied for the repair and regeneration of damaged cartilage. Mesenchymal stem cells provide a source of cells for the repair of musculoskeletal tissue. Mesenchymal stem cells are multipotent cells that are capable of differentiating into cartilage, tendon, muscle, cartilage or hematopoiesis supporting marrow stroma. To ensure the successful durable integration and function of the engineered tissue requires suitable biomechanical and biochemical circumstances, and poses the challenge of handling in vitro culture of human cells, cell biology and molecular biology.     

干细胞专利技术现状研究

目的了解国内、外干细胞相关专利的情况，为更好地应用知识产权对我国干细胞技术领域的研究成果进行保护提供合理化建议。方法根据干细胞研究专业术语确定相关主题词，以德文特（Derwent）数据库为背景，对多个专利数据库进行检索、筛查和分类，建立干细胞专利数据库。从专利的角度人手，对数据库中的2571篇国际及228篇国内干细胞专利文献进行分类分析。结果干细胞研究领域的专利申请情况总体呈上升趋势；早期专利申请主要涉及遗传工程中的DNA或RNA、载体、宿主等方面，随着研究的发展，涉及人或动物细胞或组织的专利申请逐渐增多，1998年后涉及人类细胞或组织的专利申请数量有了大幅增加，但目前仍以动物源性的细胞或组织为主（15．9％）；国内2001年以后申请的专利集中在人或动物来源的细胞或组织方面，以涉及人源细胞或组织的占首位（28．1％）。结论国内外干细胞相关专利现状的分析表明，国内在干细胞研究方面存在一定优势，应从多角度应用知识产权对研究成果进行保护。     

Derivation characteristics and perspectives for mammalian pluripotential stem cells

Pluripotential stem cells have been derived in mice and primates from preimplantation embryos, postimplantation embryos and bone marrow stroma. Embryonic stem cells established from the inner cell mass of the mouse and human blastocyst can be maintained in an undifferentiated state for a long time by continuous passage on embryonic fibroblasts or in the presence of specific inhibitors of differentiation. Pluripotential stem cells can be induced to differentiate into all the tissues of the body and are able to colonise tissues of interest after transplantation. In mouse models of disease, there are numerous examples of improved tissue function and correction of pathological phenotype. Embryonic stem cells can be derived by nuclear transfer to establish genome-specific cell lines and, in mice, it has been shown that embryonic stem cells are more successfully reprogrammed for development by nuclear transfer than somatic cells. Pluripotential stem cells are a very valuable research resource for the analysis of differentiation pathways, functional genomics, tissue engineering and drug screening. Clinical applications may include both cell therapy and gene therapy for a wide range of tissue injury and degeneration. There is considerable interest in the development of pluripotential stem cell lines in many mammalian species for similar research interests and applications.     

Mesenchymal stem cells and the immune system--immunosuppression without drugs?

Mesenchymal stem cells (MSC) - isolated from various tissues in humans and other species - are one of the most promising adult stem cell types due to their availability and the relatively simple requirements for in vitro expansion. They have the capacity to differentiate into several tissues, including bone, cartilage, tendon, muscle and adipose, and produce growth factors and cytokines that promote hematopoietic cell expansion and differentiation. In vivo, MSCs are able to repair damaged tissue from kidney, heart, liver, pancreas and gastrointestinal tract. Furthermore, they also have anti-proliferative, immunomodulatory and anti-inflammatory effects, but evoke only little immune reactivity. Although the mechanism underlying the immunosuppressive effects of MSCs has not been clearly defined, their immunosuppressive properties have already been exploited in the clinical setting. Therefore, in the future, MSCs might have implications for treatment of allograft rejection, graft-versus-host disease, rheumatoid arthritis, autoimmune inflammatory bowel disease and other disorders in which immunomodulation and tissue repair are required. The aim of this review is to critically analyze the field of MSC biology, particularly with respect to their immunomodulatory properties and potential clinical use in the future.     

A European discussion about stem cells for therapeutic use

Stem cells as a source material for growing cellular transplants to repair dysfunctional organs appear to be a new challenge for medical science. Though stem cells are also present in foetal and adult organs, embryonic stem cells from the pre-implantation embryo in particular have the potency to proliferate easily in vitro and the capacity to differentiate into all the body's organ-specific cells. Therefore, these are the ideal cells for developing new cell transplantation therapies for diseases such as Parkinson's disease, diabetes mellitus and heart failure. The use of spare in vitro fertilization (IVF) embryos or pre-implantation embryos specially created to harvest human embryonic stem cells is, however, controversial and an ethical problem. In a European discussion platform organised by the European Commission Research Directorate-General, the status quo of the progress was presented and subsequently commented upon and discussed in terms of medical-ethical, social, industrial and patient interests. The expectations of this new medical technology were high, but clinical trials seem only acceptable once the in vitro differentiation of stem cells can be adequately controlled and once it is known how in vitro prepared stem cells behave after implantation. The ethical justification of the use of in vitro pre-implantation embryos remains controversial. The prevailing view is that the interests of severely ill patients for whom no adequate therapy exists, surmounts the interest of protection of a human in vitro pre-implantation embryo, regardless of whether it was the result of IVF or of transplantation of a somatic cell nucleus of the patient in an enucleated donor egg cell (therapeutic cloning).     

Stem cells: biology and possible application to myocardial infarct

If the heart fails to recover sufficient functionality following an infarct, then heart failure develops, an important cause of death in the western world. One obvious therapy is to create more muscle tissue to supplement the damaged myocardium with new functional contractile cells, together with neovasculogenesis. Stem cells repair recipient tissue by differentiating into tissue-specific cells or by creating an environment that stimulates the process of repair by the body's own cells at the site. In animal studies the heart function stabilised following an injection of stem cells in the infarcted area. In 3 non-randomised trials in humans, bone marrow stem cells were injected via the infarcted artery or round the infarcted area; the results indicated an improved heart function. There is currently still insufficient fundamental knowledge about the behaviour of multipotent cells, about the effects of using them for treatment, and about their long-term risk for these cells to be employed in the treatment of patients with a heart infarct.     

Blutstammzelltransplantation Ein Beispiel praktizierter Stammzelltherapie

Hematopoietic stem cells (HSC) generate all blood cell lineages during ontogeny, and their continuous function is required for the maintenance of blood cells and immune tissues throughout life. HSC are characterized by certain key properties (multipotency, clonogenicity, self-renewal). These stem cell criteria also apply to non-hematopoietic stem cells. The capacity of HSC to self-renew is the basis for experimental and clinical bone marrow transplantation in which host HSC can engraft in donor bone marrow at long term (engraftment). HSC can also be used as cellular vectors for gene transfers in vivo. Most recently, several reports have suggested the exciting possibility that HSC can, in addition to blood cells, also generate non-blood cell types such as heart muscle or neuronal tissues. Is this potential for transdifferentiation a physiological HSC function? Are transdifferentiating HSC recruited to sites of tissue damage in vivo, and, if so, can this HSC property be used to “repair” adult tissues from bone marrow stem cells? The answers are, at present, highly speculative. In the present review we will thus focus primarily on the basic biology of HSC, and on some aspects of the clinical use of HSC in bone marrow transplantation.     

Stem cells: hype and hope

There is increasing interest in the use of stem cells for therapeutic purposes. The use of embryonic stem cells carries ethical and legal restrictions that limit their role in tissue regeneration. These restrictions do not apply to somatic stem cells, such as haematopoietic stem cells, which normally reside in the bone marrow. Preclinical studies have produced very promising results using these cells in experimental models of myocardial infarction. Bone-marrow cells have also been used to generate several different types of tissue. However, experimental data suggest that bone marrow also houses other non-haematopoietic stem cells, which could account for the alleged plasticity of haematopoietic stem cells. So far, the results of randomised clinical trials in patients with myocardial infarction or heart failure have been disappointing. It is clear that further research in this field is needed.     

骨髓间充质干细胞移植治疗帕金森病的研究进展

骨髓间充质干细胞是一类具有多向分化潜能的成体干细胞,它可在体外分离、培养、扩增及诱导分化,目前可分化为骨细胞、软骨细胞、肌细胞、神经细胞等,是组织工程的重要种子细胞之一。骨髓间充质干细胞转化为神经细胞并进行细胞替代或转基因治疗这一方法为神经系统退行性疾病的治疗提供了广阔的前景。     

Differentiation of embryonic and adult stem cells into insulin producing cells

Replacement of insulin producing cells represents an almost ideal treatment for patients with diabetes mellitus type 1. Transplantation of pancreatic islets of Langerhans is successful in experienced centers. The wider application of this therapy, however, is limited by the lack of donor organs. Insulin producing cells generated from stem cells represent an attractive alternative. Stem cells with the potential to differentiate into insulin producing cells include embryonic stem cells (ESC) as well as adult stem cells from various tissues including the pancreas, liver, bone marrow and adipose tissue. The use of human ESC is hampered by ethical concerns but research with human ESC may help us to decipher important steps in the differentiation process in vitro since almost all information available on pancreas development are based on animal studies. The present review summarizes the current knowledge on the development of insulin producing cells from embryonic and adult stem cells with special emphasis on pancreatic, hepatic and human mesenchymal stem cells.     

Stem cell perspectives in myocardial infarctions

Myocardial infarction is the leading cause of congestive heart failure and death in industrializated countries. The cellular cardiomyoplasty has emerged as an alternative treatment in the regeneration of infarted myocardial tissue. In animals' models, different cellular lines such as cardiomyocites, skeletal myoblasts, embryonic stem cells and adult mesenchymal stem cells have been used, resulting in an improvement in ventricular function and decrease in amount of infarcted tissue. The first three cells lines have disvantages as they are allogenics and are difficult to obtain. The adult mesenchymal stem cells are autologous and can be obtained throught the aspiration of bone marrow or from peripherical circulation, after stimulating with cytokines (G-CSF). The implantation in humans with recent and old myocardial infarction have shown improvements similar to those shown in animal models. These findings encourage the continued investigation in the mechanism of cellular differentiation and implantation methods in infarcted myocardial tissue.     

干细胞研究与女性生殖

成年卵巢可能通过干细胞而再生卵母细胞,体外培养胚胎干细胞可形成卵母细胞,为治疗性克隆提供可能的卵母细胞来源,对提高和保存女性生育力有重要意义。近年妊娠相关的干/祖细胞参与母体组织修复也引起关注。随着干细胞和组织工程研究技术的发展,用不同的方法深入研究,希望能阐明女性生殖的发育生物学机制及生殖系统疾病的发病机制,为临床治疗提供新的切入点。     

Stem cell research: licit or complicit? Is a medical breakthrough based on embryonic and fetal tissue compatible with Catholic teaching?

In November 1998 biologists announced that they had discovered a way to isolate and preserve human stem cells. Since stem cells are capable of developing into any kind of human tissue or organ, this was a great scientific coup. Researchers envision using the cells to replace damaged organs and to restore tissue destroyed by, for example, Parkinson's disease, diabetes, or even Alzheimer's. But, since stem cells are taken from aborted embryonic and fetal tissue or "leftover" in vitro embryos, their use raises large ethical issues. The National Institutes of Health (NIH) recently decided to fund research employing, not stem cells, but "cell lines" derived from them. The NIH has essentially made an ethical determination, finding sufficient "distance" between cell lines and abortion. Can Catholic universities sponsoring biological research agree with this finding? Probably not. In Catholic teaching, the concept of "complicity" would likely preclude such research. However, Catholic teaching would probably allow research done with stem cells obtained from postpartum placental tissue and from adult bone marrow and tissue. These cells, which lack the pluripotency of embryonic and fetal stem cells, are nevertheless scientifically promising and do not involve the destruction of human life.     

Somatische Stammzellen des zentralen Nervensystems

During neural development, the nervous system is created from stem cells that have the potential to proliferate, to reproduce (self-renew) themselves, and to differentiate into the appropriate neuronal and glial phenotypes. Although the adult brain has traditionally been thought of as a structure with very limited regenerative capacity, these neural stem cells have recently been shown to exist in the adult central nervous system (CNS) as well. In vitro and following transplantation, neural stem cells obtained from the fetal and adult brain are able to generate neurons, astrocytes, and oligodendrocytes, the three major CNS cell types. Therefore, neural stem cells are potential sources for specialized neural cells needed to treat a variety of neurological disorder. The present review describes how somatic stem cells of the central nervous system can be cultivated in vitro and to which extend stem cell transplantation is effective in animal models for neurological diseases. Finally, a perspective is given on the potential clinical use of human neural stem cells for the treatment of neurological diseases.     

生物技术与医学模式变革:迈向再生医学时代

基因工程、细胞工程、组织工程和整体动物工程等新的生物技术使医学模式发生变革,从以化学药物加手术刀为主要治疗手段的传统医学模式,迈向以基因治疗、细胞移植或生物人工组织器官移植为主要的治疗手段的"再生医学"模式。使用基因工程技术生产各种重组蛋白药物或疫苗越来越广泛地应用于临床。人类基因组计划(HGP)将在2003年完成全部高质量的基因组序列,HGP所开发的资源将对未来的20年的医学领域药物开发、疾病诊断、疾病易感性预测、个体化疾病预防及治疗方案设计等方面都产生巨大的影响。基因治疗从简单的单基因形式走向一整套基因的替代的复杂形式。DNA微阵列和蛋白组微阵列等科学研究技术将应用于临床诊断。核移植技术正在用于培养通用干细胞,用于移植以治疗艾滋病、糖尿病和帕金森氏病等难治性疾病。通过干细胞移植可以再生受损的组织器官。在体外构建可供移植的生物人工组织器官以取代丧失功能的组织器官,这正是组织工程的目标。再生医学存在不少科学技术困难和伦理问题。新的生物技术不仅给我们带来希望,而且还带我们带来不可预测危险。     

组织工程修复关节软骨损伤研究进展

关节软骨损伤后修复能力有限,组织工程为软骨疾病的治疗开辟新的途径。现从关节软骨的结构和功能、组织工程的种子细胞、支架材料、体外培养以及修复机理等方面阐述国内外在软骨组织工程领域的研究进展,并指出软骨组织工程存在和需要解决的问题。     

Circulating stem cells and tissue repair

Stem cells are defined as cells that have clonogenic, self-renewing capacities and the capability to differentiate into multiple cell lineages. Whereas embryonic stem cells are derived from mammalian embryos in the blastocyst stage and can generate terminally differentiated cells of all 3 embryonic germ layers, adult human stem cells are capable of maintaining, generating, and replacing terminally differentiated cells within their own specific tissue as a consequence of physiologic cell turnover or tissue injury. The traditional idea of organ-restricted stem-cell differentiation is now being challenged by the suggestion that adult stem cells retain developmental plasticity. Preclinical and clinical studies described in this review provide evidence that within the blood circulate not only progenitor cells that differentiate into hematopoietic cells, but also stem/progenitor cells which can participate in the homeostasis, repair and replacement of solid organ tissues. In addition to the occurrence of cell fusion, there are 4 suggested mechanisms of adult stem cell differentiation into solid organ cells. Preclinical data support these models particularly that of transdifferentiation as the most likely model, allowing stem/progenitor cells to differentiate across lineage, tissue, and germ layer boundaries. There is increasing evidence that we can manipulate in vivo circulating adult stem cells to repair or regenerate solid organ tissue, which offers potential clinical benefit in the treatment of many hereditary and acquired diseases.     

间充质干细胞治疗心脏疾患的研究进展

间充质干细胞(mesenchymal stem cells,MSCs)存在于多种组织内,是一种具有自我增殖和多项分化潜能的成体干细胞。MSCs体外易培养,且具有免疫调节特性,使其成为实现组织再生的种子细胞。动物心肌梗死模型证实MSCs体内移植,能够分化为心肌细胞和血管细胞,募集内源性心肌干细胞,分泌系列细胞因子,这些特性能够防止和逆转心室重构。Ⅰ期临床试验表明MSCs移植具有提高左室射血分数、抑制心室重构、减少瘢痕面积的作用。