The differentiation of mammalian neurons during development is a highly complex process involving regulation and coordination of gene expression at multiple steps. The P19 mouse embryonal carcinoma cell line is a suitable model system with which to analyze regulation of neuronal differentiation. These multipotential cells can be maintained and propagated in tissue culture in an undifferentiated state. Exposure of aggregated P19 cells to retinoic acid results in the differentiation of cells with many fundamental phenotypes of mammalian (...) neurons. Undifferentiated P19 cells are amenable to genetic manipulations such as transfection and establishment of stable clonal cell lines expressing introduced genes. Proteins that play a key role in the neuronal differentiation of P19 cells are beginning to be identified. These include retinoic acid receptors, the epidermal growth factor receptor and the transcription factors Oct‐3 and Brn‐2. The biological and technical advantages of this system should facilitate deeper analysis of the activities of proteins that play a role in neuronal differentiation. (shrink)

How cell commitment and differentiation are controlled in the early stages of embryogenesis is a problem that has long fascinated developmental biologists. Retinoic acidinduced differentiation of embryonal carcinoma cells in culture provides a model in which these questions can be explored. Recent work has yielded exciting insights into the central series of molecular changes which drives the commitment of these cells to formation of a new phenotype. Interacting with the key molecules in this central pathway is a (...) variety of transcription factors, many of which show changes in availability and/or activity during differentiation. In various combinations, these modulate the activities of genes involved in both cell proliferation and in the production of extracellular matrix and other proteins characteristic of differentiated cells. (shrink)

Pluripotent stem cells have gained special attraction because of their almost unlimited proliferation and differentiation capacity in vitro. These properties substantiate the potential of pluripotent stem cells in basic research and regenerative medicine. Here three types of in vitro‐cultured pluripotent stem cells (embryonic carcinoma, embryonic stem and induced pluripotent stem cells) are compared in their historical context with respect to their different origin and properties. It became evident that tumourigenicity is an inherent property (...) of pluripotent cells based on p53 down‐regulation, expression of tumour‐related genes and high telomerase activity that allow unlimited proliferation. In addition, culture‐adapted genetic and epigenetic changes may induce tumourigenicity of pluripotent cells. The use of stem cells in regenerative medicine, however, requires non‐malignant cell types and strategies that circumvent stages of malignancy. Reprogramming strategies of adult somatic cells that avoid the tumourigenic state of pluripotency may offer alternatives for future biomedical application. (shrink)

What is now familiarly referred to as the ‘embryonic stem (ES) cell’ is a recent biological category whose origins lie in research into benign and malignant teratomas carried out in the 1950s, 60s and 70s. In these studies, the question of the normal or pathological character of the ES cell was a matter of considerable debate and indeed the term ES cell was often used interchangeably with that of the embryonal carcinoma (EC) cell. This article argues that the (...) indecisiveness of the entity known as the ES cell—its refusal to commit to established demarcations between the normal and the pathological—continues to haunt the field of stem cell science. Exploring the prehistory of research into ES cells, early theories of cancer (in particular the embryonal theory expounded by Julius Cohnheim) and recent theoretical critiques of the somatic mutation theory, the article not only points to a shift in understandings of the normal and the pathological but asks under what conditions such shifts are able to take place. (shrink)

Silencing of tumor suppressor genes (TSGs), by DNA methylation, is well known in adult cancers. However, based on the “stem cell” theory of tumorigenesis, the early epigenetic events arising in malignant precursors remain unknown. A recent report1 demonstrates that, while pluripotent embryonic stem cells lack DNA methylation and possess a “bivalent” pattern of activating and repressive histone marks in numerous TSGs, analogous multipotent malignant cells derived from germ cell tumors (embryonic carcinoma cells) gain additional (...) silencing modifications to those same genes. These results suggest a possible mechanism by which aberrant differentiation, mediated by histone and DNA methylation, instigates tumor progression. BioEssays 29:842–845, 2007. © 2007 Wiley Periodicals, Inc. (shrink)

This article examines the assertion that human embryonic stem cells patents are immoral because they violate human dignity. After analyzing the concept of human dignity and its role in bioethics debates, this article argues that patents on human embryos or totipotent embryonic stem cells violate human dignity, but that patents on pluripotent or multipotent stem cells do not. Since patents on pluripotent or multipotent stem cells may still threaten human dignity by encouraging people to (...) treat embryos as property, patent agencies should carefully monitor and control these patents to ensure that patents are not inadvertently awarded on embryos or totipotent stem cells. (shrink)

The recent success in generating live offspring from embryonic stem cell –derived gametes in mice sparked visions of growing tailor-made sperm for men faced with infertility. However, although this development will almost certainly lead to new insights into the processes underlying spermatogenesis and thus in the possible causes of male infertility, it is less certain if deriving sperm from ES cells, which are in turn derived from a sterile man, can make someone a genetic parent. As the gap (...) between newly envisioned reproductive technologies and natural reproduction widens, the question thus needs to be asked if these possible therapies still lead to genetic parenthood. (shrink)

: In 1998, researchers discovered that embryonic stem cells could be derived from early human embryos. This discovery has raised a series of ethical and public-policy questions that are now being confronted by multiple international organizations, nations, cultures, and religious traditions. This essay surveys policies for human embryonic stem cell research in four regions of the world, reports on the recent debate at the United Nations about one type of such research, and reviews the positions that various (...) religious traditions have adopted regarding this novel type of research. In several instances the religious traditions seem to have influenced the public-policy debates. (shrink)

This article contributes to the current debate on human embryonic stem cell researchers’ possible complicity in the destruction of human embryos and the relevance of such complicity for the issue of commodification of human embryos. I will discuss if, and to what extent, researchers who destroy human embryos, and researchers who merely use human embryos destroyed by others, have moral use rights, and/or moral property rights, in these embryos. I argue that the moral status of the human embryo, however (...) justified, places few restrictions on the latter researchers’ use of it, and property rights in it, once it is destroyed. I argue that the former researchers have no property rights in the destroyed embryo but use rights in it to the extent allowed by the legitimate owners of the destroyed embryo. I discuss the implications of this account for previous and current US federal law regulating human embryonic stem cell research. (shrink)

The possibility of obtaining stem cells from human embryos has given rise to an intensive legal and ethical debate. In this paper, attention is paid to the normative disparity and ambiguity in Europe. An argument for the need for a minimal legal harmonization is made; and a prudent and flexible way to reach this successfully is suggested. Establishing a common legal framework seems to be the only way to guarantee true competitiveness for the European scientific community.

The potential benefits of embryonic stem cell research have been clarified by the last ten years of research so that it is necessary to re-examine the foundations for the restrictions imposed on this research. Those who believe that life begins at the moment of fertilization and is imbued with a full complement of human rights have opposed all embryonic research. As one who accepts this premise, I will demonstrate that there are certain limited circumstances in which parents may (...) donate embryos to establish stem cell lines that fully respect the rights of the embryonic person. In these circumstances, their action is morally equivalent to organ donation from a dying child to save the lives of others. (shrink)

While some people claim that the present disagreement over embryonic stem cell research cannot be resolved, others argue that developing transparency and trust are key elements that could resolve the existing disagreements over such research. This paper reveals that transparency is not necessarily a requirement for advancing ES cell research, since in Israel, for instance, there is no transparency, and research nevertheless flourishes. Moreover, trust is not independent of cultural values and religious beliefs. Because of these beliefs, the environment (...) in Israel for ES cell research has been pragmatic and liberal. The Israeli case illustrates the key role that culture and religion can play in biomedical research; it also suggests that as far as cultural values or religious beliefs of people in Western countries strongly oppose research on embryonic tissue, it would be very difficult, if not impossible, to overcome the disagreements. (shrink)

The possibility of obtaining stem cells from human embryos has given rise to an intensive legal and ethical debate. In this paper, attention is paid to the normative disparity and ambiguity in Europe. An argument for the need for a minimal legal harmonization is made; and a prudent and flexible way to reach this successfully is suggested. Establishing a common legal framework seems to be the only way to guarantee true competitiveness for the European scientific community.

Restrictions on research on therapeutic cloning are questionable as they inhibit the development of a technique which holds promise for succesful application of pluripotent stem cells in clinical treatment of severe diseases. It is argued in this article that the ethical concerns are less problematic using therapeutic cloning compared with using fertilised eggs as the source for stem cells. The moral status of an enucleated egg cell transplanted with a somatic cell nucleus is found to be more clearly (...) not equivalent to that of a human being. Based on ethical considerations alone, research into therapeutic cloning should be encouraged in order to develop therapeutic applications of stem cells. (shrink)

Embryonic Stem Cell Research raises ethical issues. In the process of research, embryos may be destroyed and, to some, such an act entails the ‘killing of human life’. Past studies have sought the views of scientists and the general public on the ethics of ESCR. This study, however, explores multi-faith ethical viewpoints, in particular, those of Buddhists, Hindus and Catholics in Malaysia, on ESCR. Responses were gathered via semi-structured, face-to-face interviews. Three main ethical quandaries emerged from the data: sanctity (...) of life, do no harm, and ‘intention’ of the research. Concerns regarding the sanctity of life are directed at particular research protocols which interfere with religious notions of human ensoulment and early consciousness. The principle of ‘do no harm’ which is closely related to ahimsa prohibits all acts of violence. Responses obtained indicate that respondents either discourage research that inflicts harm on living entities or allow ESCR with reservations. ‘Intention’ of the research seems to be an interesting and viable rationale that would permit ESCR for the Buddhists and Hindus. Research that is intended for the purpose of alleviating human suffering is seen as being ethical. This study also notes that Catholics oppose ESCR on the basis of the inviolability of human life. (shrink)

One objection to embryonic stem (ES) cell research is that it ‘cannibalizes’ human beings, that is, kills some human beings to benefit others. I grant for argument’s sake that the embryo is a person. Nonetheless, killing it may be justified. I show this through the Embryonic Stem Cell Lottery. Whether killing a person is justified depends on: (1) whether innocent people at risk of being killed for ES cell research also stand to benefit from the research and (2) (...) whether their overall chances of living are higher in a world in which killing and ES cell research is conducted. I call this kind of killing ‘risk reductive.‘. (shrink)

Embryonic stem cells are derived from the preimplantation embryo and can differentiate into virtually any other cell type, which is governed by lineage specific transcriptions factors binding to cis regulatory elements to mediate changes in gene expression. The reliance on transcriptional regulation to maintain pluripotency makes ESCs a valuable model to study the role of distal CREs such as enhancers in modulating gene expression to affect cell fate decisions. This review will highlight recent advance on transcriptional enhancers, focusing (...) on studies performed in ESCs. In addition, we argue that the Nanog locus, which encodes for an ESC-critical TF, is particularly informative because it contains multiple co-regulated genes and enhancers in close proximity to one another. The unique landscape at Nanog permits the study of ongoing questions including whether multiple enhancers function additively versus synergistically, determinants of gene specificity, and cell-to-cell variability in gene expression. Nanog encodes a transcription factor required to maintain ESC pluripotency. The Nanog locus is an ideal model to study enhancers because it contains multiple highly potent super-enhancers within a small region. Nanog and three super-enhancers are in close physical proximity but only two SEs are required for Nanog expression. (shrink)

Discussions about the use and derivation of pluripotent human embryonic stem cells are a stumbling block in developing public policy on stem cell research. On the one hand there is a broad consensus on the benefits of these cells for science and biomedicine; on the other hand there is the controversial issue of killing human embryos. I will focus on the compromise position that accepts research on spare embryos, but not on research embryos ('discarded-created-distinction', from now on (...) d-c-d). I will point out that this viewpoint is hard to maintain. The main focus is that the 'revealed beliefs' of its defenders are inconsistent with their 'professed beliefs', more specifically with their main argument, i.e. the potentiality argument. I will point out that (1) the defenders of d-c-d actually grant a relative moral status to the human embryo, (2) this moral status is dependent on internal and external criteria of potentiality, (3) potentiality seen as a variable value that also depends on external criteria cannot justify d-c-d, and (4) an approach to human embryonic stem cell-research that would also allow the use of research embryos is more compatible with the feelings, attitudes and values of those who currently defend d-c-d and, therefore, could lead to a broader consensus and to actions that alleviate individual human suffering. (shrink)

Discussions about the use and derivation of pluripotent human embryonic stem cells are a stumbling block in developing public policy on stem cell research. On the one hand there is a broad consensus on the benefits of these cells for science and biomedicine; on the other hand there is the controversial issue of killing human embryos. I will focus on the compromise position that accepts research on spare embryos, but not on research embryos (‘discarded‐created‐distinction’, from now on (...) d‐c‐d). I will point out that this viewpoint is hard to maintain. The main reason is that the ‘revealed beliefs’ of its defenders are inconsistent with their ‘professed beliefs’, more specifically with their main argument, i.e. the potentiality argument. I will point out that (1) the defenders of d‐c‐d actually grant a relative moral status to the human embryo, (2) this moral status is dependent on internal and external criteria of potentiality, (3) potentiality seen as a variable value that also depends on external criteria cannot justify d‐c‐d, and (4) an approach to human embryonic stem cell‐research that would also allow the use of research embryos is more compatible with the feelings, attitudes and values of those who currently defend d‐c‐d and, therefore, could lead to a broader consensus and to actions that alleviate individual human suffering. (shrink)

Embryonic stem cell research holds great promise for biomedical research, but involves the destruction of human embryos. Katrien Devolder explores the tension between the view that embryos should never be deliberately harmed, and the view that such research must go forward. She provides an in-depth analysis of major attempts to resolve the problem.

Discusses the ethical issues involved in the use of human embryonic stem cells in regenerative medicine.

ABSTRACT One of the most important as well as most awesome achievements of modern biotechnology is the possibility of cloning human embryonic stem cells, if not human beings themselves. The possible revolutionary role of such stem cells in curative, preventive and enhancement medicine has been voiced and chorused around the globe. However, the question of the moral status of embryonic stem cells has not been clearly and unequivocally answered. Taking inspiration from the African adage that (...) ‘the hand that reaches beneath the incubating hen is not guiltless’, I attempt answering this question, from the background of traditional African moral sensibility and sensitivity. I reach the following conclusions. Stem cells in themselves do not have human status and therefore lack moral worth/value. Embryos do have human status and a morally significant line cannot be drawn between human embryos and other human beings. What is morally at stake in stem cell research is therefore the question of the source of derivation or generation of the cells, not of the cells as such. (shrink)

Embryonic stem cells are actively debated in political and public policy arenas. However, the connections between stem cell innovation and overall health care policy are seldom elucidated. As with many controversial aspects of medical care, the stem cell debate bridges to a variety of social conversations beyond abortion. Some issues, such as translational medicine, commercialization, patient and public safety, health care spending, physician practice, and access to insurance and health care services, are core health policy concerns. Other issues, (...) such as economic development, technologic progress, fiscal politics, and tort reform, are only indirectly related to the health care system but are frequently seen through a health care lens. These connections will help determine whether the stem cell debate reaches a resolution, and what that resolution might be. (shrink)

Biological pacemakers can be achieved by various gene‐based and cell‐based approaches. Embryonic stem cells (ESCs)‐derived pacemaker cells might be the most promising way to form biological pacemakers, but there are challenges as to how to control the differentiation of ESCs and to overcome the neoplasia, proarrhythmia, or immunogenicity resulting from the use of ESCs. As a potential approach to solve these difficult problems, tissue‐engineering techniques may provide a precise control on the different cell components of multicellular aggregates (...) and the forming of a construct with‐defined architectures and functional properties. The combined interactions between ESC‐derived pacemaker cells, supporting cells, and matrices may completely reproduce pacemaker properties and result in a steady functional unit to induce rhythmic electrical and contractile activities. As ESCs have a high capability for self‐renewal, proliferation, and potential differentiation, we hypothesize that ESCs can be used as a source of pacemaker cells for tissue‐engineering applications and the ambitious goal of biological cardiac pacemakers may ultimately be achieved with ESCs via tissue‐engineering technology. (shrink)

Biological pacemakers can be achieved by various gene‐based and cell‐based approaches. Embryonic stem cells (ESCs)‐derived pacemaker cells might be the most promising way to form biological pacemakers, but there are challenges as to how to control the differentiation of ESCs and to overcome the neoplasia, proarrhythmia, or immunogenicity resulting from the use of ESCs. As a potential approach to solve these difficult problems, tissue‐engineering techniques may provide a precise control on the different cell components of multicellular aggregates (...) and the forming of a construct with‐defined architectures and functional properties. The combined interactions between ESC‐derived pacemaker cells, supporting cells, and matrices may completely reproduce pacemaker properties and result in a steady functional unit to induce rhythmic electrical and contractile activities. As ESCs have a high capability for self‐renewal, proliferation, and potential differentiation, we hypothesize that ESCs can be used as a source of pacemaker cells for tissue‐engineering applications and the ambitious goal of biological cardiac pacemakers may ultimately be achieved with ESCs via tissue‐engineering technology. -/- . (shrink)

The recent discussions about alternative sources of human embryonic stem cells , while stirring new interest in the developmental potential of the various abnormal embryos or constructs proposed as such sources, also raise questions about the potential of the derived embryonic stem cells. The data on the developmental potential of embryonic stem cells that seem relevant for ethical considerations and aspects of patentability are discussed. Particular attention is paid to the meaning of “totipotency, omnipotency (...) and pluripotency” as illustrated by a comparison of the developmental potential of three-dimensional clusters of blastomeres , embryonic stem cells, somatic or stem cells or other somatic cells. This paper focuses on embryoid bodies and on direct cloning by tetraploid complementation. Usage and patenting of these cells cannot be considered to be ethically sound as long as totipotency and tetraploid complementability of embryonic stem cells are not excluded for the specific cell line in question. Testing this poses an ethical problem in itself and needs to be discussed in the future. (shrink)

In this article I rebut conservative objections to five phases of embryonic stem cell research. I argue that researchers using existing embryonic stem cell lines are not complicit in the past destruction of embryos because beneficiaries of immoral acts are not necessary morally tainted. Second, such researchers do not encourage the destruction of additional embryos because fertility clinics presently destroy more spare embryos than researchers need. Third, actually harvesting stem cells from slated-to-be-discarded embryos is not wrong. The (...) embryos are not sacrificed for the good of others because they would have been destroyed anyway. Fourth, harvesting stem cells from embryos that are not doomed is morally acceptable, because preserving frozen embryos is futile therapy. Finally, creating embryos solely for the sake of harvesting stem cells from them is morally acceptable because the assumption that embryos have the right to life has very counterintuitive implications. (shrink)

Since their derivation, human embryonic stem (hES) cells have been used for a variety of applications including developmental biology, pathology, chemical biology, genomics, and proteomics. However, their most important potential application is the generation of cells and tissues, which can be used for cell‐based therapies. One of the main drawbacks of hES cell culture is that they are particularly sensitive to dissociation, which is required for passaging, expansion, cryopreservation, and other applications. Recently, it has been discovered that (...) an inhibitor of Rho kinase (ROCKi; Y‐27632) increases the survival rate of dissociated, single hES cells. This breakthrough has allowed new methods in hES cell culture to be developed, with the promise of increasing hES cell numbers into the realm of clinical relevance. In our studies demonstrating that ROCKi dramatically increases hES cell cryopreservation efficiency, we have observed that ROCKi treatment does not decrease hES cell's susceptibility to apoptosis. Rather, we hypothesize that ROCKi treatment desensitizes single hES cells to their environment reducing the odds that individual cells will undergo anoikis. (shrink)

We discuss in this essay the alternative techniques proposed for the isolation of human embryonic stem cells (hESCs) that attempt to satisfy moral issues surrounding killing embryos but show that these techniques are either redundant or do not achieve their intended aim. We discuss the difficulties associated with defining a human embryo and how the lack of clarity on this issue antagonises the ethical debate and impedes hESC research. We present scientific evidence showing that isolation of hESCs does (...) not necessarily "kill" human embryos. In addition, we argue that even those who accord inviolable moral status to the embryo should agree that hESC research is morally obligatory, as it is beneficial to the developmental potential of the embryo and society as a whole. (shrink)

Despite the therapeutic potential of human embryonic stem (HES) cells, many people believe that HES cell research should be banned. The reason is that the present method of extracting HES cells involves the destruction of the embryo, which for many is the beginning of a person. This paper examines a number of compromise solutions such as parthenogenesis, the use of defective embryos, genetically creating a "pseudo embryo" that can never form a placenta, and determining embryo death, and (...) argues that none of these proposals are likely to satisfy embryoists, that is, those who regard the embryo as a person. This paper then proposes a method of extracting HES cells, what might be called the Blastocyst Transfer Method, that meets the ethical requirements of embryoists, and it considers some possible concerns regarding this method. It concludes by encouraging future HES cell research to investigate this method. (shrink)

The recent discussions about alternative sources of human embryonic stem cells , while stirring new interest in the developmental potential of the various abnormal embryos or constructs proposed as such sources, also raise questions about the potential of the derived embryonic stem cells. The data on the developmental potential of embryonic stem cells that seem relevant for ethical considerations and aspects of patentability are discussed. Particular attention is paid to the meaning of “totipotency, omnipotency (...) and pluripotency” as illustrated by a comparison of the developmental potential of three-dimensional clusters of blastomeres , embryonic stem cells, somatic or stem cells or other somatic cells. This paper focuses on embryoid bodies and on direct cloning by tetraploid complementation. Usage and patenting of these cells cannot be considered to be ethically sound as long as totipotency and tetraploid complementability of embryonic stem cells are not excluded for the specific cell line in question. Testing this poses an ethical problem in itself and needs to be discussed in the future. (shrink)

Stem cell banks curating and distributing human embryonic stem cells have been established in a number of countries and by a number of private institutions. This paper identifies and critically discusses a number of arguments that are used to justify the importance of such banks in policy discussions relating to their establishment or maintenance. It is argued (1) that ‘ethical arguments’ are often more important in the establishment phase and ‘efficiency arguments’ more important in the maintenance phase, and (...) (2) that arguments relating to the interests of embryo and gamete donors are curiously absent from the particular stem cell banking policy discourse. This to some extent artificially isolates this discourse from the broader discussions about the flows of reproductive materials and tissues in modern society, and such isolation may lead to the interests of important actors being ignored in the policy making process. (shrink)

One of the most‐exciting and controversial discoveries of the last decade has been the isolation of embryonic stem cells from human embryos. The capacity of these cells to form all somatic cell types in the human body has captured the imagination of researcher and clinician alike, the perspectives that they represent for cell replacement therapies in multiple chronic disorders being used to justify the use of embryos for this purpose. However, there is a gradual realization that cell (...) therapies are in the far future and some find that the other, more immediately applicable, types of research give less justification for the use of embryos. Here, cardiomyocytes derived from human embryonic stem cells are discussed. The research opportunities created by having human heart cells available routinely in the laboratory are explored and the types of questions that can be addressed are placed in the context of alternative cell and animal models. BioEssays 29:572–579, 2007. © 2007 Wiley Periodicals, Inc. (shrink)

Given the promise of stem cell therapies, scientists throughout the world are conducting stem cell research using various kinds of stem cells including human embryonic stem cells. However, HESC research is very controversial in some societies as the extraction of stem cells involves the destruction of the human embryo. The ethical concerns of this kind of research have led scientists to search for other methods to derive stem cells that do not involve the destruction of (...) embryos. These different types of stem cell research are said to sidestep the ethical dilemma associated with HESC research and so are considered as ethically acceptable ways to obtain stem cells; possibly, they may even mark the end of HESC research. However, each of these stem cell methods presents its own challenges, scientific and ethical, as this article explores. This paper examines the impact of the emergence of different types of stem cell research and discusses whether it is still necessary for scientists to conduct the contentious HESC research. (shrink)

The debate surrounding human embryonic stem cell research plays a crucial role in the culture wars. Those who embrace post-traditional morality not only see no ethical problem with the destruction of human embryos for research and therapies, but press for their use despite the greater potential for risk from the totipotent cells that are harvested from the destruction of human embryos as opposed to other kinds of stem cells. Indeed, there have been foreseeable negative consequences from such (...) attempts at treatment. Nonetheless, from the standpoint of traditional Christianity, the destruction of human embryos is expressly forbidden regardless of any potential positive outcomes. There is a fundamental cleft within the culture on such issues. (shrink)

Essays on stem cell policy seem to fall into three categories. Some essays in this collection are about logic and principles. Others are about practices and beliefs. The former group draws lines and defends them, a normative project. The latter group attempts to explain the lines that already exist, a descriptive project that may have important normative goals. Still other essays, by scientists, are about growing stem cell lines instead of drawing them.The purpose of this essay is to situate the (...) lines being drawn around stem cell science in the larger landscape of health policy. I am interested in the things that cause health policy to take particular directions and the consequences of those directions for cost, access, and quality — all of which are determined in part by biomedical innovations such as those potentially derived from stem cells. (shrink)

Embryonic stem cells (ESCs) are now classified into two types of pluripotency: “naïve” and “primed” based upon their differing characteristics. Conventional human ESCs have much more in common with mouse epiblast stem cells and are now deemed to be primed. Naïve human ESCs that resemble mouse ESCs have recently been generated from their primed counterpart by cellular reprogramming. Isolation of naïve hESCs from human embryos has proven to be difficult. Is the inability to capture naïve hESCs the (...) result of suboptimal derivation conditions or because they are so transient they cannot be “captured” in vitro? Prevailing evidence surrounding this issue are inconclusive and require additional human embryo research. However, negative public opinion regarding human embryo research, may make this an uphill battle. The solution may come from cellular reprogramming. (shrink)

Combining human embryonic stem cells with SCNT has been a gold standard of stem cell research. Adding a particular individual's genes to pluripotent stem cells might lead to the development of personalized tissue repair or replacement. Enthusiasm for human embryonic stem cell research had flagged in recent years due to controversy over the moral status of in vitro embryos, scientific misconduct by researcher Woo Suk Hwang, and the discovery that induced pluripotent stem cells could be (...) produced from somatic cells. Energy shifted to research on somatic cells, but three successes in the United States during 2013 and 2014 may reinvigorate embryonic stem cell research. (shrink)