Examining stem cell biology from a philosophy of science perspective, this book clarifies the field's central concept, the stem cell, as well as its aims, methods, models, explanations and evidential challenges. The first chapters discuss what stem cells are, how experiments identify them, and why these two issues cannot be completely separated. The basic concepts, methods and structure of the field are set out, as well as key limitations and challenges. The second part of (...) the book shows how rigorous explanations emerge from stem cell experiments, and compares these to other kinds of scientific explanation. Model organisms, the role of genes, and the significance of collaboration are also discussed. The last part of the book considers relations to systems biology and clinical medicine, arguing that both the mathematical models of the former, and ethical principles of the latter, are necessary for stem cell biology to deliver on its promises. (shrink)

Stem cell scientists and ethicists have focused intently on questions relevant to the developmental stage and developmental capacities of stem cells. Comparably less attention has been paid to an equally important set of questions about the nature of stem cells, their common characteristics, their non‐negligible differences and their possible developmental species specificity. Answers to these questions are essential to the project of justly inferring anything about human stem cell biology from studies in non‐human (...) model systems—and so to the possibility of eventually developing human therapies based on stem cell biology. After introducing and discussing these questions, I conclude with a brief discussion of the creation of novel model systems in stem cell biology: human‐to‐animal embryonic chimeras. Such novel model systems may help to overcome obstacles to extrapolation, but they are also scientifically and ethically contentious. BioEssays 26:1005‐1012, 2004. © 2004 Wiley Periodicals, Inc. (shrink)

This review surveys three central issues in philosophy of stem cell biology: the nature of stem cells, stem cell experiments, and explanations of stem cell capacities. First, I argue that the fundamental question ‘what is a stem cell?’ has no single substantive answer. Instead, the core idea is explicated via an abstract model, which accounts for many features of stem cell experiments. The second part of this essay examines (...) several of these features: uncertainty, model organisms, and manipulability. The results shed light on the form of our emerging knowledge of stem cells: mechanistic explanations. The third part of the essay sketches some key features of these explanations, which are constructed by a collaborative experimenting community. (shrink)

Stem cell biology is driven by experiment. Its major achievements are striking experimental productions: "immortal" human cell lines from spare embryos (Thomson et al. 1998); embryo-like cells from "reprogrammed" adult skin cells (Takahashi and Yamanaka 2006); muscle, blood and nerve tissue generated from stem cells in culture (Lanza et al. 2009, and references therein). Well-confirmed theories are not so prominent, though stem cell biologists do propose and test hypotheses at a profligate rate. 1 (...) This paper aims to characterize the role of experiment in stem cell biology, so as to answer the following question: how do experiments contribute to our knowledge of stem cells and related phenomena? The .. (shrink)

The complexities of modern science are not adequately reflected in many bioethical discussions. This is especially problematic in highly contested cases where there is significant pressure to generate clinical applications fast, as in stem cell research. In those cases a more integrated approach to bioethics, which we call systems bioethics, can provide a useful framework to address ethical and policy issues. Much as systems biology brings together different experimental and methodological approaches in an integrative way, systems bioethics (...) integrates aspects of the history and philosophy of science, social and political theory, and normative analysis with the science in question. In this paper we outline how a careful analysis of the science of stem cell research can help to refocus the discussions related to the clinical applications of stem cells. We show how inaccurate or inadequate scientific assumptions help to create a set of unrealistic expectations and badly inform ethical deliberations and policy development. Systems bioethics offers resources for moving beyond the current impasse. (shrink)

Previous work has suggested that many stem cells can be found in microanatomic niches, where adjacent somatic cells of the niche control the differentiation and proliferation states of their resident stem cells. Recently published work examining intestinal stem cells (ISCs) in the adult Drosophila midgut suggests a new paradigm where some stem cells actively control the cell fate decisions of their daughters. Here, we review recent literature(1) demonstrating that, in the absence of a detectable (...) class='Hi'>stem cell niche, multipotent Drosophila ISCs modulate the Notch signaling pathway in their adjacent daughter cells in order to specify the differentiated lineages of their descendants. These observations made in Drosophila are challenging and advancing our understanding of stem cell biology. BioEssays 30:107–109, 2008. © 2008 Wiley Periodicals, Inc. (shrink)

Ubiquitination plays a central role in the regulation of stem cell self‐renewal, propagation, and differentiation. In this review, the functions of ubiquitin dynamics in a myriad of cellular processes, acting along side the pluripotency network, to regulate embryonic stem cell identity are highlighted. The implication of deubiquitinases (DUBs) and E3 Ubiquitin (Ub) ligases in cellular functions beyond protein degradation is reported, including key functions in the regulation of mRNA stability, protein translation, and intra‐cellular trafficking; and how (...) it affects cell metabolism, the micro‐environment, and chromatin organization is discussed. Finally, unsolved issues in the field are emphasized and will need to be tackled in order to fully understand the contribution of ubiquitin dynamics to stem cell self‐renewal and differentiation. (shrink)

The limbus is a narrow band of tissue that encircles the cornea, the transparent ‘window’ into the eye. The outermost layer of the cornea is the epithelium, which is necessary for clear vision. The limbus acts as a ‘reservoir’ for limbal stem cells which maintain and regenerate the corneal epithelium. It also functions as a barrier to the conjunctiva and its blood vessels. Limbal stem cell deficiency is a general term for diseases which are characterised by the (...) impairment of the limbus, limbal stem cells and their ability to replenish the corneal epithelium through proliferation and differentiation. Consequently, sufferers experience chronic pain and progressive blindness. This paper will highlight the salient milestones of limbal stem cell biology and potential future treatments for limbal stem cell deficiency. (shrink)

This chapter brings a philosophical perspective to the concept of stem cell. Three general questions both clarify the concept of stem cell and emphasize its ambiguities: (1) How should we define stem cells? (2) What makes them different from non-stem cells? (3) What is their ontology? (i.e. what kind of property is “stemness”?) Following this last question, the Chapter distinguishes four conceptions of stem cells and highlights their respective consequences for the cancer (...) class='Hi'>stem cell theory. Determining what kind of property stemness is, in what context, is an urgent question, at least for therapeutic strategies against cancers. I hope that this chapter also illustrates how philosophy can be useful to biology. -/- The Chapter starts by clarifying the notions of self-renewal and differentiation. This leads to the question “can we (and if so, how) distinguish stem cells from non-stem cells through these two properties?”. From that will follow an interrogation on whether stem cells belong to a natural kind. On this issue, biologists and philosophers have framed the following alternative: either the concept of stem cell refers to entities (the cells that belong to the stem cell natural kind) or it refers to a transient and reversible cell state. I will argue that four conceptions of stemness should be distinguished rather than two. Finally, I will develop the case of the cancer stem cell (CSC) theory in order to show why it is crucial to answer the ontological question: some therapies might or might not be efficient depending on what stemness is. (shrink)

This paper aims to bring the epistemic dimensions of stem cell experiments out of the background, and show that they can be critically evaluated. After introducing some basic concepts of stem cell biology, I set out the current “gold standard” for experimental success in that field (§2). I then trace the origin of this standard to a 1988 controversy over blood stem cells (§3). Understanding the outcome of this controversy requires attention to the details (...) of experimental techniques, the organization of epistemic communities, and relations between the two (§4). With its resolution, a standard for experimental success was established for HSC research, which in turn serves as an exemplar for studies of other stem cells. This historical case study reveals a robust standard for experimental success in stem cell biology: to trace processes of development at the single-cell level, in the form of cell lineage hierarchies. Experiments conforming to this standard can be further critically assessed as means to the therapeutic end of stem cell research: use of stem cells to repair human organs and tissues. (shrink)

Sarah Franklin’s Biological relatives: IVF, stem cells, and the future of kinship and Charis Thompson’s Good science: the ethical choreography of stem cell research, examine recently normalized biotechnologies. Franklin’s monograph extends her previous work on in vitro fertilization , deconstructing the success of a technology that, she argues, has grown “curiouser and curiouser” while taking hold in scientific and social life. IVF in its diverse aspects becomes a lens for scrutinizing our ambivalence about new technology, which Franklin (...) articulates by putting disparate literatures into conversation: feminist science studies, political economy, fine art, and more. Thompson’s Good science focuses more concretely on the first decade of human pluripotent stem cell research, tracing the field from the innovation of cultured human embryonic stem cells through Bush-era policy debates, to current acceptance of stem cell research as a part of the scientific and policy landscape. Th .. (shrink)

Melinda Fagan’s book on the philosophy of stem cell biology is a superb discussion of this exciting field of contemporary science, and the first book-length philosophical treatment of the subject. It contains a detailed and insightful examination of stem cell science, its structure, methods, and challenges.The book does not require any previous knowledge of stem cell biology—all the relevant scientific details and concepts, the central experimental procedures and results, as well as the (...) historical development of the field, are presented in as clear and accessible a way as possible. The presentation of the science starts in Chapter 1, with a general characterisation of stem cell biology, and continues throughout the book, with every chapter deepening and complicating the initial picture. Fagan’s lucid style makes even the more technical and detailed discussions of the research on human embryonic stem cells and on blood stem cells easy to follow.After the first in .. (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)

A new therapeutic strategy could break the stalemate in the war on cancer by targeting not all cancerous cells but the small fraction that lie at the root of cancers. Lucie Laplane offers a comprehensive analysis of cancer stem cell theory, based on an original interdisciplinary approach that combines biology, biomedical history, and philosophy.

If stem cell-based therapies are developed, we will likely confront a difficult problem of justice: for biological reasons alone, the new therapies might benefit only a limited range of patients. In fact, they might benefit primarily white Americans, thereby exacerbating long-standing differences in health and health care.

Stem cell biology and systems biology are two prominent new approaches to studying cell development. In stem cell biology, the predominant method is experimental manipulation of concrete cells and tissues. Systems biology, in contrast, emphasizes mathematical modeling of cellular systems. For scientists and philosophers interested in development, an important question arises: how should the two approaches relate? This essay proposes an answer, using the model of Waddington’s landscape to triangulate between (...) class='Hi'>stem cell and systems approaches. This simple abstract model represents development as an undulating surface of hills and valleys. Originally constructed by C. H. Waddington to visually explicate an integrated theory of genetics, development and evolution, the landscape model can play an updated unificatory role. I examine this model’s structure, representational assumptions, and uses in all three contexts, and argue that explanations of cell development require both mathematical models and concrete experiments. On this view, the two approaches are interdependent, with mathematical models playing a crucial but circumscribed role in explanations of cell development. (shrink)

This paper examines a case of failed interdisciplinary collaboration, between experimental stem cell research and theoretical systems biology. Recently, two groups of theoretical biologists have proposed dynamical systems models as a basis for understanding stem cells and their distinctive capacities. Experimental stem cell biologists, whose work focuses on manipulation of concrete cells, tissues and organisms, have largely ignored these proposals. I argue that ‘failure to communicate’ in this case is rooted in divergent views of (...) explanation: the theoretically-inclined modelers are committed to a version of the covering-law view, while experimental stem cell biologists aim at mechanistic explanations. I propose a way to reconcile these two explanatory approaches to cell development, and discuss the significance of this result for interdisciplinary collaboration in systems biology and beyond. (shrink)

Ontologies of living things are increasingly grounded on the concepts and practices of current life science. Biological development is a process, undergone by living things, which begins with a single cell and (in an important class of cases) ends with formation of a multicellular organism. The process of development is thus prima facie central for ideas about biological individuality and organismality. However, recent accounts of these concepts do not engage developmental biology. This paper aims to fill the gap, (...) proposing the lineage view of stem cells as an ontological framework for conceptualizing organismal development. This account is grounded on experimental practices of stem cell research, with emphasis on new techniques for generating biological organization in vitro. On the lineage view, a stem cell is the starting point of a cell lineage with a specific organismal source, time-interval of existence, and ‘tree topology’ of branch-points linking the stem to developmental termini. The concept of ‘enkapsis’ accommodates the cell-organism relation within the lineage view; this hierarchical notion is further explicated by considering the methods and results of stem cell experiments. Results of this examination include a (partial) characterization of stem cells’ developmental versatility, and the context-dependence of developmental processes involving stem cells. (shrink)

Much of the current research in regenerative medicine concentrates on stem-cell therapy that exploits the regenerative capacities of stem cells when injected into different types of human tissues. Although new therapeutic paths have been opened up by induced pluripotent cells and human mesenchymal cells, the rate of success is still low and mainly due to the difficulties of managing cell proliferation and differentiation, giving rise to non-controlled stem cell differentiation that ultimately leads to cancer. (...) Despite being still far from becoming a reality, these studies highlight the role of physical and biological constraints (e.g., cues and morphogenetic fields) placed by tissue microenvironment on stem cell fate. This asks for a clarification of the coupling of stem cells and microenvironmental factors in regenerative medicine. We argue that extracellular matrix and stem cells have a causal reciprocal and asymmetric relationship in that the 3D organization and composition of the extracellular matrix establish a spatial, temporal, and mechanical control over the fate of stem cells, which enable them to interact and control (as well as be controlled by) the cellular components and soluble factors of microenvironment. Such an account clarifies the notions of stemness and stem cell regeneration consistently with that of microenvironment. (shrink)

We review recent progress in the stem cell biology of the respiratory system, and discuss its scientific and translational ramifications. Several studies have defined novel stem cells in postnatal lung and airways and implicated their roles in tissue homeostasis and repair. In addition, significant advances in the generation of respiratory epithelium from pluripotent stem cells (PSCs) now provide a novel and powerful platform for understanding lung development, modeling pulmonary diseases, and implementing drug screening. Finally, breakthroughs (...) have been made in the generation of decellularized lung matrices that can serve as a scaffold for repopulation with respiratory cells derived from either postnatal or PSCs. These studies are a critical step forward towards the still distant goal of stem cell‐based regenerative medicine for diseases of lung and airways. (shrink)

What is a stem cell? The answer is seemingly obvious: a cell that is also a stem, or point of origin, for something else. Upon closer examination, however, this combination of ideas leads directly to fundamental questions about biological development. A cell is a basic category of living thing; a fundamental 'unit of life.' A stem is a site of growth; an active source that supports or gives rise to something else. Both concepts are (...) deeply rooted in biological thought, with rich and complex histories. The idea of a stem cell unites them, but the union is neither simple nor straightforward. This book traces the origins of the stem cell concept, its use in stem cell research today, and implications of the idea for stem cell experiments, their concrete results, and hoped-for clinical advances. (shrink)

Understanding aging and how it affects an organism's lifespan is a fundamental problem in biology. A hallmark of aging is stem cell senescence, the decline of functionality, and number of somatic stem cells, resulting in an impaired regenerative capacity and reduced tissue function. In addition, aging is characterized by profound remodeling of the immune system and a quantitative decline of adequate immune responses, a phenomenon referred to as immune‐senescence. Yet, what is causing stem cell (...) and immune‐senescence? This review discusses experimental studies of potentially immortal Hydra which have made contributions to answering this question. Hydra transcription factor FoxO has been shown to modulate both stem cell proliferation and innate immunity, lending strong support to a role of FoxO as critical rate‐of‐aging regulator from Hydra to human. Constructing a model of how FoxO responds to diverse environmental factors provides a framework for how stem cell factors might contribute to aging. (shrink)

In 2003, Ruth Faden and eighteen other colleagues argued that a.

“Stem Cells Dependently Arising and Empty” May 2021, Buddhism and Culture (a Korean-language Buddhist magazine sponsored by the Foundation for the Promotion of Korean Buddhism), Korea.

Stem cells have the capacity both to self‐renew and to give rise to differentiated progeny, and are vital to the organization of multicellular organisms. Stem cells raise a number of fundamental questions regarding lineage restriction and cellular differentiation, and they hold enormous promise for cell‐based therapies. Here I propose a theoretical framework for stem cell biology based on the concepts of autopoiesis (self‐production) and complementarity. I argue that stem cells are pivotal in the (...) self‐production of the organism and that we need complementary approaches to understand their probabilistic behavior. I discuss how this framework generates testable hypotheses regarding stem‐cell functions. BioEssays 26:1013‐1016, 2004. © 2004 Wiley Periodicals, Inc. (shrink)

This article looks at the history of the stem cell as an experimental life-form and situates it within the context of biological theories of cellular ageing which emerged in the 1960s, under the banner of ‘biogerontology’. The field of biogerontology, I argue, is crucially concerned not only with the internal limits to a cell's lifespan, but also with the possibility of overcoming limits. Hence, the sense of ‘revolution’ that has surrounded the isolation of human embryonic stem (...) cells. The article goes on to situate the problematic of cellular ageing within the larger historical transition from Fordist to post-Fordist modes of production – a transition whose effects on the life sciences have been insufficiently theorized – and points to resonances between the concerns of biogerontology and an emerging political rhetoric on the crisis of ageing and limits to growth. Having surfaced in parallel with the neo-liberal euphoria of the 1990s, the field of regenerative medicine presents itself as a biomedical solution to the problem of limits to growth. What is at stake in the contemporary biosciences, I suggest, is not so much the mass commodification of life itself as its transformation into a source of speculative surplus value. (shrink)

The prelims comprise: Introduction The Mother of All Cells Embryonic Stem (ES) Cells Specialized Stem Cells Therapeutic Implications of Stem Cell Biology Cellular Philosophy and the Mind Problem The New Alchemists Stem Cell Biology: God in a Test Tube?

Stem cell research has entered the public consciousness through the media. Proponents and opponents of all such research, or of human embryonic stem cell research specifically, engage in heated exchanges in the modern public forum where stakeholders negotiate, the agora. One common claim that emerges from the fray is that a particular type of stem cell research should be pursued as the most promising path toward the reduction of suffering and untimely death for all (...) of humanity. Upon evaluation, experimental data regarding the potential role of stem cells in regenerative therapies for three conditions—spinal cord injury, type 1 diabetes, and cardiovascular disease—tell distinct, complex, and inconclusive stories. Further analyses in this article incorporate realistic considerations of a broad range of relevant factors--limited funding for biomedical research, media motives, the discordance hypothesis of evolutionary medicine, the relationship between religion and science, medical care in developing nations, and culture wars over abortion. Holistic investigation inspired by the current agora conversation supports the need to drastically change interactions regarding stem cell research so that its potential to benefit humanity may be more fully realized. (shrink)

Egg or sperm? The mechanism of sexual fate decision in germ cells has been a long‐standing issue in biology. A recent analysis identified foxl3 as a gene that determines the sexual fate decision of germ cells in the teleost fish, medaka. foxl3/Foxl3 acts in female germline stem cells to repress commitment into male fate (spermatogenesis), indicating that the presence of mitotic germ cells in the female is critical for continuous sexual fate decision of germ cells in medaka gonads. (...) Interestingly, foxl3 is found in most vertebrate genomes except for mammals. This provides the interesting possibility that the sexual fate of germ cells in mammals is determined in a different way compared to foxl3‐possessing vertebrates. Considering the fact that germline stem cells are the cells where foxl3 begins to express and sexual fate decision initiates and mammalian ovary does not have typical germline stem cells, the mechanism in mammals may have been co‐evolved with germline stem cell loss in mammalian ovary. (shrink)

Stem cells and the emerging field of regenerative medicine are at the frontiers of modern medicine. These areas of scientific inquiry suggest that in the future, damaged tissue and organs might be repaired through personalized cell therapy as easily as the body repairs itself, revolutionizing the treatment of numerous diseases. Yet the use of stem cells is fraught with ethical and public policy dilemmas that challenge scientists, clinicians, the public health community, and people of good will everywhere. (...) How shall we deal with these amazing biomedical advances, and how can we talk about potential breakthroughs with both moral and scientific intelligence? This book provides an innovative look at these vexing issues through a series of innovative Socratic dialogues that elucidate key scientific and ethical points in an approachable manner. Addressing the cultural and value issues underlying stem cell research while also educating readers about stem cells' biological function and medical applications, _Stem Cell Dialogues_ features fictional characters engaging in compelling inquiry and debate. Participants investigate the scientific, political, and socioethical dimensions of stem cell science using actual language, analysis, and arguments taken from scientific, philosophical, and popular literature. Each dialogue centers on a specific, recognizable topic, such as the policies implemented by the George W. Bush administration restricting the use of embryonic stem cells; the potential role of stem cells in personalized medicine; the ethics of cloning; and the sale of eggs and embryos. Additionally, speakers debate the use of stem cells to treat paralysis, diabetes, stroke effects, macular degeneration, and cancer. Educational, entertaining, and rigorously researched, _Stem Cell Dialogues_ should be included in any effort to help the public understand the science, ethics, and policy concerns of this promising field. (shrink)

The clonal evolution model and the cancer stem cell model are two independent models of cancers, yet recent data shows intersections between the two models. This article explores the impacts of the CSC model on the CE model. I show that CSC restriction, which depends on CSC frequency in cancer cell populations and on the probability of dedifferentiation of cancer non-stem cells into CSCs, can favor or impede some patterns of evolution and some processes of evolution. (...) Taking CSC restriction into account for the CE model thus has implications for the way in which we understand the patterns and processes of evolution, and can also provide new leads for therapeutic interventions. (shrink)

In this chapter, I review some of the background thinking concerning matters of moral status that I had developed in previous years and that I would now bring to the work of the Human Embryo Research Panel. Two ideas were at the forefront of my thinking. First, that biology usually offers not decisive "events" but only continuous processes of development. Second, in making status determinations we do not so much "identify" a point on a developmental continuum where moral respect (...) should be accorded as "choose" that point. These choices are "balancing decisions" in which the community of moral agents weighs its interests in protecting an entity against the burdens of doing so. After illustrating these two contentions, I consider some of the reasons why thinkers on the "right" and "left" of our bioethics debates have resisted or missed this basic insight. (shrink)

On 25 April 2002, the German Parliament has passed a strict new law referring to stem cell research. This law took effect on July 1, 2002. The so-called embryonic Stem Cell Act ( Stammzellgesetz — StZG ) permits the import of embryonic stem (ES) cells isolated from surplus IvF-embryos for research reasons. The production itself of ES cells from human blastocysts has been prohibited by the German Embryo Protection Act of 1990, with the exception of (...) the use of ES cells which exist already. The debate on the legitimate use of ES cells escalated, after the main German research funding agency, the Deutsche Forschungsgemeinschaft (DFG), unexpectedly published new guidelines recommending are stricted use of human ES cells for research. Meanwhile, the debate has ethically dividedsociety, political parties, government and church members into a group supporting and a group rejecting ES cell research. The arguments in favour of such a research can be summarized as arguments derived from a new ethics ofhealing calling for a therapeutic imperative, whereas the arguments against can be summarized as arguments violating the fundamental principle of human dignity as they imply the destruction of human embryos. This article willtry to present and evaluate various ethical arguments founded on the latest biological and medical data on the potential use of stem cell technologies. It will finally come to the conclusion that ES cell research is opposed to human dignity, since the procedures of isolating ES cells require the destruction and instrumentalization of human embryos. Human embryos are human beings at a very early stage of their development, fully possessing the ability of completing their development. At this very early stage, human embryos are extremely dependent and fragile, and thus vulnerable corporealities. Vulnerability and human dignity demand the protection of the embryo's corporeal integrity. Hence, this essay will try to propagate research with adult stem(AS) cells, a procedure which does not require the destruction of human embryos; with regard to the necessary plasticity, it should be emphasized that AS cells very much resemble ES cells. (shrink)

Epithelial hair follicle stem cells (eHFSCs) are required to generate, maintain and renew the continuously cycling hair follicle (HF), supply cells that produce the keratinized hair shaft and aid in the reepithelialization of injured skin. Therefore, their study is biologically and clinically important, from alopecia to carcinogenesis and regenerative medicine. However, human eHFSCs remain ill defined compared to their murine counterparts, and it is unclear which murine eHFSC markers really apply to the human HF. We address this by reviewing (...) current concepts on human eHFSC biology, their immediate progeny and their molecular markers, focusing on Keratin 15 and 19, CD200, CD34, PHLDA1, and EpCAM/Ber‐EP4. After delineating how human eHFSCs may be selectively targeted experimentally, we close by defining as yet unmet key challenges in human eHFSC research. The ultimate goal is to transfer emerging concepts from murine epithelial stem cell biology to human HF physiology and pathology. (shrink)

Recent studies of prostate cancer and other tumor types have revealed significant support, as well as unexpected complexities, for the application of concepts from normal stem cell biology to cancer. In particular, the cell of origin and cancer stem cell models have been proposed to explain the heterogeneity of tumors during the initiation, propagation, and evolution of cancer. Thus, a basis of intertumor heterogeneity has emerged from studies investigating whether stem cells and/or non‐ (...) class='Hi'>stem cells can serve as cells of origin for cancer and give rise to tumor subtypes that vary in disease outcome. Furthermore, analyses of putative cancer stem cells have revealed the genetically diverse nature of cancers and expanded our understanding of intratumor heterogeneity and clonal evolution. Overall, the principles that have emerged from these stem cell studies highlight the challenges to be surmounted to develop effective treatment strategies for cancer. (shrink)

Stem-cell nomenclature is in a muddle! So-called stem cells may be self-renewing or emergent, oligopotent (uni- and multipotent) or pluri- and totipotent, cells with perpetual embryonic features or cells that have changed irreversibly. Ambiguity probably seeped into stem cells from common usage, flukes in biology's history beginning with Weismann's divide between germ and soma and Haeckel's biogenic law and ending with contemporary issues over the therapeutic efficacy of adult versus embryonic cells. Confusion centers on tissue (...) dynamics, whether stem cells are properly members of emerging or steady-state populations. Clarity might yet be achieved by codifying differences between cells in emergent populations, including embryonic stem and embryonic germ (ES and EG) cells in tissue culture as opposed to self-renewing (SR) cells in steady-state populations. BioEssays 28: 301–308, 2006. © 2006 Wiley Periodicals, Inc. (shrink)

Cell‐based therapies for degenerative diseases of the musculature remain on the verge of feasibility. Myogenic cells are relatively abundant, accessible, and typically harbor significant proliferative potential ex vivo. However, their use for therapeutic intervention is limited due to several critical aspects of their complex biology. Recent insights based on mouse models have advanced our understanding of the molecular mechanisms controlling the function of myogenic progenitors significantly. Moreover, the discovery of atypical myogenic cell types with the ability to (...) cross the blood‐muscle barrier has opened exciting new therapeutic avenues. In this paper, we outline the major problems that are currently associated with the manipulation of myogenic cells and discuss promising strategies to overcome these obstacles. (shrink)

Mesenchymal stem cells (MSCs) are present in fat tissues throughout the body, yet little is known regarding their biological role within epidural fat. We hypothesize that debridement of epidural fat and/or subsequent loss of MSCs within this tissue, disrupts homeostasis in the vertebral environment resulting in increased inflammation, fibrosis, and decreased neovascularization leading to poorer functional outcomes post‐injury/operatively. Clinically, epidural fat is commonly considered a space‐filling tissue with limited functionality and therefore typically discarded during surgery. However, the presence of (...) MSCs within epidural fat suggests that itis more biologically active than historically believed and may contribute to the regulation of homeostasis and regeneration in the dural environment. While the current literature supports our hypothesis, it will require additional experimentation to determine if epidural fat is an endogenous driver of repair and regeneration and if so, this tissue should be minimally perturbed from its original location in the spinal canal. Also see the video abstract here https://youtu.be/MIol_IWK1os. (shrink)

Recent reports that human pluripotent stem cells can be captured in a spectrum of states with variable properties has prompted a re‐evaluation of how pluripotency is acquired and stabilised. The latest additions to the stem cell hierarchy open up opportunities for understanding human development, reprogramming, and cell state transitions more generally. Many of the new cell lines have been collectively termed ‘naïve’ human pluripotent stem cells to distinguish them from the conventional ‘primed’ cells. Here, (...) several transcriptional and epigenetic hallmarks of human pluripotent states in the recently described cell lines are reviewed and evaluated. Methods to derive and identify human naïve pluripotent stem cells are also discussed, with a focus on the uses and future developments of state‐specific reporter cell lines and cell‐surface proteins. Finally, opportunities and uncertainties in naïve stem cell biology are highlighted, and the current limitations of human naïve pluripotent stem cells considered, particularly in the context of differentiation. (shrink)

In a thought experiment we want to test how the emergence of adult neural stem cells could constitute an example for a scientific revolution in the sense of Thomas Kuhn. In his major work, The structure of scientific revolutions, 3rd edn, University of Chicago Press, Chicago (Kuhn 1996), the philosopher of science, Thomas Kuhn, states that scientific progress is not a cumulative process, but new theories appear by a rather revolutionary sequence of events. Kuhn built his theory on landmark (...) events taken from chemistry and physics, lacking examples from biology. Beginning with Ramon y Cajal’s famous quote, no new neurons after birth , from the early years of the twentieth century, and Reynolds and Weiss’s conflicting finding in 1992 of adult neural stem cells giving rise to new neurons, we will test how the finding of neural stem cells in the adult brain matches with Kuhn’s theory. The pivotal problem of defining a paradigm will be our main focus, since the emergence of adult neural stem cells has been acclaimed by the scientific community as the rebuttal of Ramon y Cajal’s paradigm. (shrink)

This paper examines potential ethical and legal issues arising during the research, develop- ment and clinical use of a proposed strategy in personalized medicine (PM): using human induced pluripotent stem cell (iPSC)-derived tissue cultures as predictive models of individ- ual patients to inform treatment decisions. We focus on epilepsy treatment as a likely early application of this strategy, for which early-stage stage research is underway. In relation to the research process, we examine issues associated with biological samples; data; (...) health; vulnerable populations; neural organoids; and what level of accuracy justifies using the iPSC-derived neural tissue system. In relation to clinical use, we examine potential uses in pre-natal screening, and effects on clinical decision-making. Although our focus is providing recommendations for researchers developing work in this area, we identify the novel issue of deciding on an acceptable accuracy level for the system. We also emphasize an issue thus far neglected in the ethics of PM: PM tends to represent treatment decisions as though they should be directed solely by biomedical information, but this in itself could be detri- mental to best personalizing treatment decisions in the clinic. (shrink)

Often the only treatment available for patients suffering from diseased and injured organs is whole organ transplant. However, there is a severe shortage of donor organs for transplantation. The goal of organ engineering is to construct biological substitutes that will restore and maintain normal function in diseased and injured tissues. Recent progress in stem cell biology, biomaterials, and processes such as organ decellularization and electrospinning has resulted in the generation of bioengineered blood vessels, heart valves, livers, kidneys, (...) bladders, and airways. Future advances that may have a significant impact for the field include safe methods to reprogram a patient's own cells to directly differentiate into functional replacement cell types. The subsequent combination of these cells with natural, synthetic and/or decellularized organ materials to generate functional tissue substitutes is a real possibility. This essay reviews the current progress, developments, and challenges facing researchers in their goal to create replacement tissues and organs for patients. (shrink)

After a long and successful career in tracheal surgery and lung cancer, Paolo Macchiarini became very famous in 2008 with the transplantation of a trachea from a cadaver that then apparently used the patient’s own stem cells to supposedly regenerate new trachea, i.e., tissue-engineered tracheae. Among the nine patients that received this revolutionary treatment, using biological or artificial tracheae, under Macchiarini’s supervision, six have reportedly died. Although several critics had expressed concerns with the procedures, allegations of misconduct against Macchiarini (...) first arose in August of 2014 by four Karolinska Institutet (KI) colleagues, and an independent investigation was called for by KI based on claims made in seven published papers. Among the claims were the fact that the procedure constituted a high risk, information on the patients was incomplete and that there was no or incomplete ethical approval, thus constituting misconduct. His CV was also shown to contain inaccuracies. By September 10, 2016, most of these claims have now proved to be true, and Macchiarini was found guilty of misconduct by KI. This paper looks primarily at earlier published papers by Macchiarini and his collaborators in a search for clues to better understand the evolution of altruism, or narcissism. An assessment of the controversial papers, and of letters written by critics and skeptics like Pierre R. Delaere, indicate that insufficient experimental evidence was presented for several case studies, and that claims made about the success of the procedures exceeded what was shown by the evidence. A domino effect of personal and professional tragedies ensued, in rapid succession, between 2014 and 2016. The effect on the field of stem cell research has been chilling, and the side-effects have taken their toll, with several high-profile resignations, primarily at KI, within the Swedish education system and in the Nobel Committee. This case has mesmerized the bioethics and biomedical communities for years. (shrink)

This paper presents an account of the nature of stem cells based on the philosophical concept of disposition. It is argued that stem cells can be conceived as dispositional objects, and adopting this attitude allows overcoming some of the controversies surrounding the nature of stemness (most notably, the state vs. entity debate) because it offers a framework that accommodates the lessons from different theories. Additionally, the account is simultaneously useful for interpreting stem cell experiments and guiding (...) potential interventions. The account shows how different levels, both molecular and emergent network-level, play the primary causal role in explaining some empirical results, and hence they suggest that the explanations can be mechanistic or topological, respectively. The realization that any of these levels may play a more prominent causal role than another allows suggesting interventions at the genetic, molecular and population levels. (shrink)

Armed with expanded federal funding for human embryonic stem cell research and new methods for deriving pluripotent stem cells, stem cell researchers in the U.S. are poised to proceed with unprecedented speed toward the development of new clinical therapies. Staring into the new dawn of regenerative medicine, many observers may assume that the only responsible route to the clinic, both scientifically and ethically, is through FDA-approved clinical trials processes. Conventional wisdom dictates that, like pharmaceutical drugs (...) and the use of biological therapeutics, stem cell-based therapies will have to pass through a series of controlled studies — initially to assess safety and toxicity, then efficacy and comparative efficacy — before they can be justifiably administered to patients outside a clinical trials context. (shrink)