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.     

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.     

The importance of the use of stem cells for public health

Stem cells were elected 'Breakthrough of the Year' by Science(1) magazine in 1999, having shown that stem cells from adult tissues retained the ability to differentiate into other tissue types. During the previous year, the first human embryo stem cell lines were established. Since then, the number of scientific papers on stem cells has been increasing exponentially, establishing new paradigms that are rapidly challenged by subsequent experiments. This paper reviews the stem cell research field, divided into two groups: embryo and adult stem cells. While the differentiation potential of the former is well characterized in mice and humans, their use in cell therapy and research has been hampered by histocompatibility, safety and ethical issues. In contrast, adult stem cells do not present these problems. However, the extent of their plasticity is still under investigation. Nevertheless, numerous clinical trials in humans are under way, mainly with stem cells derived from bone marrow. This paper discusses discuss the importance of working with both classes of human stem cells in order to fulfill the promise of stem cell therapies.     

Bioethische und sozialethische Probleme bei der Verwendung von Geweben aus humanen embryonalen Stammzellen sowie der Aufbewahrung von Stammzellen aus dem Nabelschnurblut durch private Firmen zum autologen Gebrauch

The regulation of the European Council and Parliament on advanced therapy medicinal products also includes therapies with human embryonic stem cells. The use of these stem cells is controversially and heavily discussed. Contrary to the use of adult stem cells, medical and ethical problems concerning the use of human embryonic stem cells persists, because this use is based on the destruction of human life at the very beginning. The regulation forsees, therefore, subsidiarity within the European Member States. Although there are no ethical problems in principle with the use of stem cells from the umbilical cord blood, there are social ethical doubts with the banking of these stem cells for autologous use without any currently foreseeable medical advantage by commercial blood banks. Also in this case subsidiarity is valid.     

人胚胎干细胞建系研究中的伦理管理

目的：建立国人胚胎干细胞系递交国际干细胞库,并在此基础上建立既符合中国国情又得到国际认可的相关伦理管理体系。方法：在比尔盖茨基金会的资助下,与北京大学生命科学院再生生物学实验室合作,募集胚胎建立人胚胎干细胞系,在此过程中探讨可行的符合国际伦理原则的相关伦理管理机制。结果：成功建立了国人胚胎干细胞系及相关伦理管理体系。结论：进行干细胞研究时应充分重视伦理问题,国际干细胞伦理管理与中国相关伦理原则是可以有机结合的。     

人胚胎干细胞建系研究中的伦理管理

目的：建立国人胚胎干细胞系递交国际干细胞库,并在此基础上建立既符合中国国情又得到国际认可的相关伦理管理体系。方法：在比尔盖茨基金会的资助下,与北京大学生命科学院再生生物学实验室合作,募集胚胎建立人胚胎干细胞系,在此过程中探讨可行的符合国际伦理原则的相关伦理管理机制。结果：成功建立了国人胚胎干细胞系及相关伦理管理体系。结论：进行干细胞研究时应充分重视伦理问题,国际干细胞伦理管理与中国相关伦理原则是可以有机结合的。     

From fibroblasts and stem cells: implications for cell therapies and somatic cloning

Pluripotent embryonic stem cells (ESCs) from the inner cell mass of early murine and human embryos exhibit extensive self-renewal in culture and maintain their ability to differentiate into all cell lineages. These features make ESCs a suitable candidate for cell-replacement therapy. However, the use of early embryos has provoked considerable public debate based on ethical considerations. From this standpoint, stem cells derived from adult tissues are a more easily accepted alternative. Recent results suggest that adult stem cells have a broader range of potency than imagined initially. Although some claims have been called into question by the discovery that fusion between the stem cells and differentiated cells can occur spontaneously, in other cases somatic stem cells have been induced to commit to various lineages by the extra- or intracellular environment. Recent data from our laboratory suggest that changes in culture conditions can expand a subpopulation of cells with a pluripotent phenotype from primary fibroblast cultures. The present paper critically reviews recent data on the potency of somatic stem cells, methods to modify the potency of somatic cells and implications for cell-based therapies.     

Neonatale Stammzellen

With regard to the great social importance and ethical acceptance of cord blood stem cell research, this article is devoted to basic legal questions concerning the use of umbilical cord blood. The original legal status of the cord blood was analyzed with the result that the cord blood belongs to the child, and thus the child can claim certain personal rights regarding the cord blood. Since the newborn itself is not able to take part in legal transactions, its parents have to ensure that its personal and financial concerns are protected, as they are its legal representatives. The parents can decide together what shall happen to the cord blood because of their parental custody. They have to give their consent to the donation of the cord blood as well as to the collection of personal data of the child. The duty to obtain permission for the production of stem cell preparations derives from the German drug law. Maternity clinics and cord blood banks need this permission and those blood banks that stock up on cord blood stem cell preparations for indefinite recipients have to obtain an additional authorization because these preparations are prefabricated drugs.     

Neurogenesis and neurodegenerative diseases in human

Acute and chronic neurodegenerative diseases are the most common neurological disorders in human and affect millions of individuals worldwide. While the specific clinical presentation varies among such diseases, their common feature is neural cell death. Yet, despite major advances in the understanding of neural cell death, effective treatment for these diseases remains one of the foremost challenges for medicine today. The transplantation of embryonic cells into the diseased brain in human has emerged out a mere theory and is possible as a practical application. This advancement, however, has raised important ethical, technical and immunological concerns. Studies have documented that neurogenesis occurs in the adult brain and that endogenous neural stem/progenitor cells (NSCs) respond to neurodegenerative diseases, suggesting that it might be possible for dead or injured neural cells to be replaced by endogenous NSCs. In this regard it is especially interesting to know the biological behaviors of endogenous NSCs in response to neurodegenerative diseases. Understanding the mechanisms underlying these changes could lead to the development of new strategies for treating neurological diseases using endogenous NSC pool.     

Ethical boundary-work in the embryonic stem cell laboratory

Most accounts of the ethics of stem cell research are de- contextualised reviews of the ethical and legal literature. In this chapter we present a socially embedded account of some of the ethical implications of stem cell research, from the perspectives of scientists directly involved in this area. Based on an ethnography of two leading embryonic stem cell laboratories in the UK, our data form part of the findings from a larger project mapping the scientific, medical, social and ethical dimensions of innovative stem cell treatment, focusing on the areas of liver cell and pancreatic islet cell transplantation. We explore three key issues: what individual scientists themselves view as ethical sources of human embryos and stem cells; their perceptions of human embryos and stem cells; and how scientists perceive regulatory frameworks in stem cell research. We argue that these dimensions of laboratory practice are all examples of 'ethical boundary-work', which is becoming an integral part of the routine practice and performance of biomedical science. Our work adds to the relatively few sociological studies that explore ethics in clinical settings and to an even smaller body of work that explores scientists' views on the ethical issues relating to their research.     

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.     

An Ethical Framework for Stem Cell Research in the European Union

The European Union is a nightmare from the perspective of the ethics and regulation of science. A hitherto insoluble problem has been the task of drafting ethical principles which do not founder on the radically different attitudes taken to the question of the moral status of the human embryo. Following the conclusions reached in an international project, EUROSTEM, we suggest that this problem can be solved by concentration on the scope of principles and we emphasize that European research should be funded in a way that does not discriminate between individual states and researchers in the EU. Finally, we observe that the availability of any eventual embryonic stem cell therapies will pose a dilemma for those countries and those people that have declared stem cell research to be unacceptable.     

诱导多潜能性干细胞的研究现状与临床应用前景

胚胎干细胞可作为细胞替代治疗中很好的供体细胞来源。但由于伦理学的原因,限制了胚胎干细胞在细胞替代治疗中的应用前景,而诱导多潜能性干细胞(induced pluripotent stem cell,iPS细胞)的出现则提供了一种替代胚胎干细胞的多潜能性细胞。因为iPS细胞的建立不需要卵细胞,也不破坏发育中的胚胎,所以iPS细胞不涉及伦理学问题。而且iPS细胞的建立相对简单,重复性好。因此,iPS细胞在细胞替代治疗和再生医学中有着广泛的应用前景。本文将回顾iPS细胞技术发展的历史,介绍现有的建立iPS细胞的不同方法和评估iPS细胞质量的手段,展望iPS细胞在细胞替代治疗上有待解决的问题和应用前景。     

Would cancer stem cells affect the future investment in stem cell therapy

The common goal within the overwhelming interests in stem cell research is to safely translate the science to patients. Although there are various methods by which this goal can be reached, this editorial emphasizes the safety of mesenchymal stem cell (MSC) transplant and possible confounds by the growing information on cancer stem cells (CSCs). There are several ongoing clinical trials with MSCs and their interactions with CSCs need to be examined. The rapid knowledge on MSCs and CSCs has now collided with regards to the safe treatment of MSCs. The information discussed on MSCs can be extrapolated to other stem cells with similar phenotype and functions such as placenta stem cells. MSCs are attractive for cell therapy, mainly due to reduced ethical concerns, ease in expansion and reduced ability to be transformed. Also, MSCs can exert both immune suppressor and tissue regeneration simultaneously. It is expected that any clinical trial with MSCs will take precaution to ensure that the cells are not transformed. However, going forward, the different centers should be aware that MSCs might undergo oncogenic events, especially as undifferentiated cells or early differentiated cells. Another major concern for MSC therapy is their ability to promote tumor growth and perhaps, to protect CSCs by altered immune responses. These issues are discussed in light of a large number of undiagnosed cancers.     

干细胞向雌性生殖细胞分化的研究进展

干细胞是一类具有自我更新和多向分化潜能的细胞。根据其来源不同,干细胞可分为胚胎干细胞、成体干细胞以及诱导性多能干细胞。生殖细胞系负责跨代传递遗传和表观遗传信息,以确保新的正常个体产生。人类辅助生殖技术(ART)虽可解决部分难治性不孕不育患者的生育问题,但尚不能解决由于卵巢早衰生殖细胞缺乏导致的不孕,如果在体外可以将干细胞定向诱导分化为生殖细胞,则可能通过ART帮助卵巢早衰患者获得健康后代。雌性配子发育经历了多个严格、复杂的过程,包括原始生殖细胞(PGC)特化、增殖、迁移到生殖嵴并最终分化为成熟的卵母细胞。然而具体过程尚不明确。近年来学者已建立了干细胞向雌性生殖细胞分化的体外模型,并取得了长足进步。     

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).     

干细胞研究进展及相关伦理学问题思考

始于上世纪末,迄今仍方兴未艾的干细胞研究,由于其特殊的细胞分化,组织再生,甚至可能的器官再造特性,引起了又一次生物医学革命,被视为20世纪末最重要的生物医学成就。但同时由于胚胎干细胞涉及的人类胚胎生命及组织、器官的再生成等伦理学问题,干细胞研究从问世的第一天起,就在生物医学家、哲学家、法学家、政治家间引起广泛的争论。文章简要复习了近年来干细胞研究成果及干细胞研究引起的相关伦理学争论,并就干细胞研究引发的伦理学问题及对未来医疗发展的影响提出作者的观点。     

The ethical challenge of stem cell research.

This article analyzes the ethical issues raised by embryonic stem cell research and recent recommendations by the National Bioethics Advisory Commission (NBAC) regarding federal support for this research. The authors identify the key ethical issue as the moral significance that should be granted to early embryos and discuss arguments supporting the diverse answers to that question and the implications each view has on the formulation of rules and policies for stem cell research. The authors conclude that several of NBAC's recommendations regarding the derivation of stem cells from embryos for research are ethically justifiable and sound public policy.     

From stem cells to insulin-producing cells: towards a bioartificial endocrine pancreas

The total absence or low production of insulin by beta-cells avoids a proper control of glycemia forcing diabetic people to daily insulin injection for survival. Islet transplantation represents a hallmark in the cure of diabetes and has been successfully applied to more than 400 patients, resulting in insulin independency for periods longer than 4 years. However, transplantation trials for diabetes have to face the scarcity of islets from cadaveric donors. Therefore, the finding of renewable sources of cells could circumvent this problem. In this respect, embryonic or adult stem cells are representing an interesting alternative. Stem cells display robust proliferation and the plasticity to differentiate to other cell types, including insulin-containing cells. The current therapeutical use in the future of bioengineered insulin-secreting cells derived from stem cells needs at present to fulfill several criteria. These criteria concern to the type of stem cell to be used as starting biomaterial (embryonic or adult), the in vitro differentiation protocol applied, the functional phenotype reached for the final cell product and the transplantation associated problems (likely immune rejection and tumor formation). This review will try to focus on these different aspects in order to emphasize in the key points to consider for designing unified strategies for diabetes cell therapy.