Cognitive deficits were produced in rats by different methods of damaging the brain: chronic ingestion of alcohol, causing widespread damage to diffuse cholinergic and aminergic projection systems; lesions (by local injection of the excitotoxins, ibotenate, quisqualate, and AMPA) of the nuclei of origin of the forebrain cholinergic projection system (FCPS), which innervates the neocortex and hippocampal formation; transient cerebral ischaemia, producing focal damage especially in the CA1 pyramidal cells of the dorsal hippocampus; and lesions (by local injection of the neurotoxin, (...) colchicine) of the granule cells of the dentate gyrus. Following chronic alcohol or lesions of the FCPS, transplants of cholinergically rich fetal brain tissue into the terminal areas (neocortex and/or hippocampus) restored performance almost to control levels, with a time course consistent with growth of the transplants and integration with host tissue; transplants of cholinergically poor fetal tissue (hippocampus) were without effect, as were transplants of cholinergically rich tissue into the region containing the nuclei of origin of the FCPS. Grafts of primary cells enriched in glia and cultured neuroblastoma cells into the terminal areas of the FCPS were equally effective, suggesting that there are multiple mechanisms by which neural transplants can restore cognitive function following diffuse cholinergic damage. In contrast, after ischaemia- or neurotoxin-induced damage to CA1 or dentate granule cells respectively, cholinergically rich fetal transplants into the damaged hippocampal formation were ineffective in restoring performance. After ischaemic damage, however, performance was restored by suspension grafts of CA1 cells but not by transplants containing CA3 pyramidal cells or granule cells; and after colchicine damage it was restored by solid grafts containing granule but not CA1 pyramidal cells. Furthermore, electrophysiological evidence has demonstrated functional, graft type-specific host-graft functional neuronal connectivity. Thus, restoration of cognitive function by neural transplants is possible after damage to either diffuse (cholinergic) or point-to-point (intrahippocampal) forebrain systems, but the transplant must be appropriate to the damage to be repaired. Because the different types of brain damage studied provide analogues of human alcoholic dementia, Alzheimer's disease, and heart attack, these results are encouraging with regard to the eventual application of neural transplant surgery to the treatment of cognitive deficits in humans. (shrink)

Despite reports of recovery of function after neural transplantation, the biological interactions between transplanted neurons and the host brain that are necessary to mediate recovery are unclear at present. One source of confusion is in the variety of models and protocols used in these studies. It is suggested that multisite experimentation using standard protocols, models, and recovery criteria would be helpful in moving neural transplantation from the laboratory to the clinic.

Parkinson’s disease (PD) is a common neurodegenerative disorder of the nervous system that affects about 1 in 800 people and for which we have symptomatic but not curative therapies. At the core of the disease is the loss of a specific population of dopaminergic neurons within the brain, and replacement of dopamine through drug therapies has provided clinically significant benefit for many patients. However this therapy only ever offers a temporary amelioration of symptoms and with time this symptomatic therapy becomes (...) less efficacious and produces its own unique side-effects. As a result more effective curative therapies have been sought, including the use of cell based therapies to replace the lost dopaminergic neurons. In this review I am going to discuss PD and its possible repair using neural transplants. In particular I am going to discuss which type of cells are best considered as a reparative therapy, where they should be transplanted in the brain, when in the disease course and in which type of patient. By considering these issues, I hope to be able to make some recommendations as to the future use of this approach in PD. (shrink)

Research on neural transplantation has great potential societal importance in part because of the expanding proportion of the population that is elderly. Transplantation studies can benefit from the guidance of research on cognitive aging, especially in connection with the assessment of behavioral outcomes. Speech for example, might be explored using avian models.

In contrast to the views put forth by Stein & Glasier, we support the use of inbred strains of rodents in studies of the immunobiology of neural transplants. Inbred strains demonstrate homology of the major histocompatibility complex (MHC). Virtually all experimental work in transplantation immunology is performed using inbred strains, yet very few published studies of immune rejection in intracerebral grafts have used inbred animals.

The lesion and transplantation data cited by Sinden et al., when considered in tandem, seem to harbor an internal inconsistency, raising questions of false localization of function. The extrapolation of such data to cognitive impairment and potential treatment strategies in Alzheimer's disease is problematic. Patients with focal basal forebrain lesions (e.g., anterior communicating artery aneurysm rupture) might be a more appropriate target population.

A lesion to the brain is not necessary for a successful neural transplantation. Embryonic Purkinje cells placed on the surface of an uninjured adult cerebellum can develop and migrate into the host molecular layer. Both the Purkinje cells that migrated into the host cerebellum and those that remained in the graft were innervated by collateral sprouting of adult intact climbing fibers.

The neural transplantation research described by Sinden and colleagues provides part of the rationale for the clinical application of neural transplantation. The authors are asked to clarify their view of the role of the cholinergic system in cognition, to address extrahippocampal damage caused by transient forebrain ischemia, and to consider the effects of delayed neural degeneration in their structure-function analysis.

Neural fetal tissue transplantation offers promise as a treatment for devasting neurologic conditions such as Parkinson's disease. Two types of issues arise from this procedure: those associated with the use of fetuses, and those associated with the use of neural tissue. The former issues have been examined in many forums; the latter have not. This paper reviews issues and arguments raised by the use of fetal tissue in general, but focuses on the implications of the use of (...) class='Hi'>neural tissue for basic concepts of personnood and personal identity. (shrink)

Neural transplantation as a recovery strategy for neuro-degenerative diseases in humans has used mainly grafting following acute denervation strategies in young adult hosts. Our work in aged mice and rats demonstrates an age-related increase in susceptibility to oxidative damage from neurotoxins, a remarkably poor recovery of C57BL/6 mice from MPTP insult with transplantation and growth factors, even at 12 months of age, and diminished plasticity of host neurons. We believe that extrapolation of data from young adult animal models to (...) aged humans without thorough investigation of transplantation and host response in aged recipients is scientifically and ethically inappropriate. (shrink)

Over the past two decades, research on neural transplantation in animal models of neurodegeneration has provided provocative in sights into the therapeutic use of grafted tissue for various neurological diseases. Although great strides have been made and functional benefits gained in these animal models, much information is still needed with regard to transplantation in human patients. Several factors are unique to human disease, for example, age of the recipient, duration of disease, and drug interaction with grafted cells; these need (...) to be explored before grafting can be considered a safe and effective therapeutic tool. (shrink)

Neural cell transplants have been introduced in clinical practice during the last decade with mixed results, encouraged by success with simple animal models. This commentary is a reminder that although the ideas and techniques of transplantation appear simple, the variables involved in host-transplant integration still require further study. The field may benefit from a concerted, multidisciplinary approach.

New possibilities to modify function and direct repair in the central nervous system (CNS) have been established by the merger of gene transfer technology with neural transplantation. Rapid advances in viral‐mediated DNA‐delivery procedures permit the study of novel gene expression in neurons and glial cells. Foreign genes, transferred by a virus vector, can be used to generate new cell lines, identify transplanted cells, and express growth factors or enzymes for neurotransmitter synthesis. In addition to CNS cell types, non‐neural (...) cells are also being studied with transgene technology in the nervous system. Functional effects have been obtained with grafts of genetically modified cells in animal models of several nervous system disorders, and the recent results set the stage for potential application of these techniques to human CNS gene therapy. (shrink)

The procurement of fetal tissue for transplantation may promise great benefit to those suffering from various pathologies, e.g., neural disorders, diabetes, renal problems, and radiation sickness. However, debates about the use of fetal tissue have proceeded without much attention to ethical theory and application. Two broad moral questions are addressed here, the first formal, the second substantive: Is there a framework from other moral paradigms to assist in ethical debates about the transplantation of fetal tissue? Does the use of (...) fetal tissue entail cooperation in abortion? To answer these questions I develop a theoretical framework by combining the paradigm of just-war reasoning with canons governing the use of cadaverous tissue. The kinds of safeguards provided by this paradigm allow fetal tissue to be procured without the taint of association with abortion. Central to solving the problem of cooperation is the distinction between intending and foreseeing a moral misdeed. Fetal researchers may foresee fetal death in elective abortions without intending such deaths to occur. Thus, even those who object unequivocally to elective abortion may condone the procurement of fetal tissue, if sufficient reason exists. Keywords: fetal tissue, casuistry, prima facie duties, just-war tenets, complicity CiteULike Connotea Del.icio.us What's this? (shrink)

In spite of Stein and Glasier's justifiable conclusion that initial optimism concerning the immediate clinical applicability of neural transplantation was premature, there exists much experimental evidence to support the potential for incorporating this procedure into a therapeutic arsenal in the future. To realize this potential will require continued evolution of our knowledge at multiple levels of the clinical and basic neurosciences.

Stem cells isolated from adult mammalian tissues may provide new approaches for the autologous treatment of disease and tissue repair. Although the potential of adult stem cells has received much attention, it has also recently been brought into question. This article reviews the recent work describing the ability of non‐hematopoietic stem cells derived from adult bone marrow to form neural derivatives and their potential for brain repair. Earlier transplantation experiments imply that grafted adult stem cells can differentiate into (...) class='Hi'>neural derivatives. Recent reports suggest, however, that such findings may be misleading and grafted cells acquiring different identities may merely be explained by their fusion with host cells and not the result of radical changes to their program of cellular differentiation. Nonetheless, in vitro studies have shown that neural development by bone‐marrow‐derived stem cells also appears possible. Understanding the molecular mechanisms that specify the neural lineage will lead to the development of tools for the targeted production of neural cell types in vitro that may ultimately provide a source of material to treat specific neurological deficits. BioEssays 24:708–713, 2002. © 2002 Wiley Periodicals, Inc. (shrink)

Alongside in vitro studies, researchers are increasingly exploring the transplantation of human brain organoids (HBOs) into non-human animals to study brain development, disease, and repair. This paper focuses on ethical issues raised by such transplantation studies. In particular, it investigates the possibility that they might yield enhanced brain function in recipient animals (especially non-human primates), thereby fundamentally altering their moral status. I assess the critique, raised by major voices in the bioethics and science communities, according to which such concerns are (...) premature and misleading. I identify the assumptions underlying this skeptical critique, and mention some objections against them, followed by some possible replies. I proceed to argue that the skeptical position is ultimately implausible, because it presupposes an unreasonably high standard of full moral status. My argument appeals to David DeGrazia’s idea of a “borderline person”, and to the need for consistency with existing animal research regulations. I outline the practical implications of my view for the conduct of studies that might result in the development of full moral status in a transplanted animal. I also discuss some of the ethical implications of animal enhancement (particularly of rodents) below the threshold associated with full moral status. I conclude that far from being premature, further debate on these issues is urgently needed to help clarify the prospects that a neural chimera might attain full moral status in the foreseeable future, and the level of quality of life required to make it acceptable to knowingly create such a being via HBO transplantation. (shrink)

Studies on the snailMelampusreveal that connectivity is crucial to the survival of transplanted ganglia. Transplanted CNS ganglia can innervate targets or induce supernumerary structures. Neuron survival is optimized by the neural incorporation that occurs when a transplanted ganglion is substituted for an excised ganglion. Better provision for the trophic requirements of neurons will improve the success of mammalian fetal transplants.

Researchers are enthusiastically concerned about neural stem cell (NSC) therapy in a wide array of diseases, including stroke, neurodegenerative disease, spinal cord injury (SCI) and depression. Although enormous evidences have demonstrated that neurobehavioral improvement may benefit from NSC-supporting regeneration in animal models, approaches to endogenous and transplanted NSCs are blocked by hurdles of migration, proliferation, maturation and integration of NSCs. Electrical stimulation (ES) may be a selective nondrug approach for mobilizing NSCs in the central nervous system (CNS). This technique (...) is suitable for clinic application, because it is well established and its potential complications are manageable. Here, we provide a comprehensive review of the emerging positive role of different electrical cues in regulating NSC biology in vitro and in vivo, as well as biomaterial-based and chemical stimulation of NSCs. In the future, ES combined with stem cell therapy or other cues probably becomes an approach for promoting brain repair. (shrink)

Neural crest cells are multipotent progenitors, capable of producing diverse cell types upon differentiation. Recent studies have identified significant heterogeneity in both the fates produced and genes expressed by different premigratory crest cells. While these cells may be specified toward particular fates prior to migration, transplant studies show that some may still be capable of respecification at this time. Here we summarize evidence that extracellular signals in the local environment may act to specify premigratory crest and thus generate diversity (...) in the population. Three main classes of signals–Wnts, BMP2/BMP4 and TGFβ1,2,3–have been shown to directly influence the production of particular neural crest cell fates, and all are expressed near the premigratory crest. This system may therefore provide a good model for integration of multiple signaling pathways during embryonic cell fate specification. BioEssays 22:708–716, 2000. © 2000 John Wiley & Sons, Inc. (shrink)

Grafts of embryonic neural tissue into the brains of adult patients are currently being used to treat Parkinson's disease and are under serious consideration as therapy for a variety of other degenerative and traumatic disorders. This target article evaluates the use of transplants to promote recovery from brain injury and highlights the kinds of questions and problems that must be addressed before this form of therapy is routinely applied. It has been argued that neural transplantation can promote (...) functional recovery through the replacement of damaged nerve cells, the reestablishment of specific nerve pathways lost as a result of injury, the release of specific neurotransmitters, or the production of factors that promote neuronal growth. The latter two mechanisms, which need not rely on anatomical connections to the host brain, are open to examination for nonsurgical, less intrusive therapeutic use. Certain subjective judgments used to select patients who will receive grafts and in assessment of the outcome of graft therapy make it difficult to evaluate the procedure. In addition, little long-term assessment of transplant efficacy and effect has been done in nonhuman primates. Carefully controlled human studies, with multiple testing paradigms, are also needed to establish the efficacy of transplant therapy. (shrink)

Neural crest cells are multipotent progenitors, capable of producing diverse cell types upon differentiation. Recent studies have identified significant heterogeneity in both the fates produced and genes expressed by different premigratory crest cells. While these cells may be specified toward particular fates prior to migration, transplant studies show that some may still be capable of respecification at this time. Here we summarize evidence that extracellular signals in the local environment may act to specify premigratory crest and thus generate diversity (...) in the population. Three main classes of signals–Wnts, BMP2/BMP4 and TGFβ1,2,3–have been shown to directly influence the production of particular neural crest cell fates, and all are expressed near the premigratory crest. This system may therefore provide a good model for integration of multiple signaling pathways during embryonic cell fate specification. BioEssays 22:708–716, 2000. © 2000 John Wiley & Sons, Inc. (shrink)

This commentary reviews data supporting circuitry reconstruction, replacement neurotransmitters, and trophic action as mechanisms whereby transplants promote recovery of function. Issue is taken with the thesis of Sinden et al. that adequate data exist to indicate that reconstruction of hippocampal circuitry damaged by hypoxia with CA1 transplants is a confirmed mechanism whereby these transplants produce recovery. Sinden et al.'s and Stein & Glasier's proposal that there is definitive evidence showing that all transplants produce trophic effects is (...) also questioned. (shrink)

This article investigates a critical yet underexplored structural aspect of consciousness in the context of the practical ethics of neural organoid research: the unity of consciousness. We advocate for the necessity of the unified field, which has garnered substantial support from both philosophical and empirical standpoints, although the debate remains unresolved. We highlight the brainstem as a potential source of the unified conscious field, a structure already under scrutiny in neural organoid research in relation to conditions such as (...) Parkinson’s disease and post-COVID-19 syndromes. We argue that if unity is a necessary feature of consciousness, consciousness is contingent upon a specific biological system without which consciousness cannot arise, thereby narrowing the range of neural organoids of ethical concern. Furthermore, the transplantation of neural organoids into animals has emerged as a practical concern, with ethical implications varying based on the necessity of the unity of consciousness. We argue that transplantation evades a significant ethical dilemma if unity is necessary and if the organoids to be transplanted lack the neural basis for the unified field of consciousness. (shrink)

The current debate regarding the suitability of anencephalics as organ donors is due primarily to misunderstandings. The anatomical and neurophysiological literature shows that the anencephalic lacks a cerebrum because of the failure of neuralplate fusion. However, even the incomplete function of an atrophic brain stem is currently accepted at law in most if not all countries as sufficient for brain life: which is to say, cessation of breathing is currently required in order to make the diagnosis of brain death. Because (...) of the extensive incompleteness of the anencephalic's brain, it is not possible to postpone death significantly by mechanical ventilation and intravenous feeding. It is acceptable to maintain life for a short period of time in order to allow organ transplantation subsequent to the declaration of death at the point of cessation of the capacity for spontaneous respiration. The most important issue is not transplantation, but the issue of brain life raised by the case of anencephalics. Since brain life in any significant sense begins only after the closure of the neural tube on the 30th day after conception, it is reasonable to take this as the point at which brain life begins. Laws should be amended in all countries to allow the abortion of anencephalics at any time, in that they do not at any time possess brain life. (shrink)

Three experiments on neural grafting with adult rat hosts are described. Working memory impairments were produced by lesioning the hippocampus or severing its connections with the septum by ablating the fimbria-fornix. The results suggest that the survival and growth of a neural graft, whether an autograft or a xenograft, is not a necessary condition for functional recovery on a task tapping working memory.

Brain states, which correlate with specific motor, cognitive, and emotional states, may be monitored with noninvasive techniques such as electroencephalography and magnetoencephalography that measure macroscopic cortical activity manifested as oscillatory network dynamics. These rhythmic cortical signatures provide insight into the neuronal activity used to identify pathological cortical function in numerous neurological and psychiatric conditions. Sensory and transcranial stimulation, entraining the brain with specific brain rhythms, can effectively induce desired brain states correlated with such cortical rhythms. Because brain states have distinct (...) neural correlates, it may be possible to induce a desired brain state by replicating these neural correlates through stimulation. To do so, we propose recording brain waves from a “donor” in a particular brain state using EEG/MEG to extract cortical signatures of the brain state. These cortical signatures would then be inverted and used to entrain the brain of a “recipient” via sensory or transcranial stimulation. We propose that brain states may thus be transferred between people by acquiring an associated cortical signature from a donor, which, following processing, may be applied to a recipient through sensory or transcranial stimulation. This technique may provide a novel and effective neuromodulation approach to the noninvasive, non-pharmacological treatment of a variety of psychiatric and neurological disorders for which current treatments are mostly limited to pharmacotherapeutic interventions. (shrink)

Stem cells are likely to be used as an alternate source of biological material for neural transplantation to treat Parkinson’s disease in the not too distant future. Among the several ethical criteria that must be fulfilled before proceeding with clinical research, a favourable benefit to risk ratio must be obtained. The potential benefits to the participant and to society are evaluated relative to the risks in an attempt to offer the participants a reasonable choice. Through examination of preclinical studies (...) transplanting stem cells in animals and the transplantation of fetal tissue in patients with Parkinson’s disease, a current set of potential benefits and risks for neural transplantation of stem cells in clinical research of Parkinson’s disease are derived. The potential benefits to research participants undergoing stem cell transplantation are relief of parkinsonian symptoms and decreasing doses of parkinsonian drugs. Transplantation of stem cells as a treatment for Parkinson’s disease may benefit society by providing knowledge that can be used to help determine better treatments in the future. The risks to research participants undergoing stem cell transplantation include tumour formation, inappropriate stem cell migration, immune rejection of transplanted stem cells, haemorrhage during neurosurgery and postoperative infection. Although some of these risks are general to neurosurgical transplantation and may not be reduced for participants, the potential risk of tumour formation and inappropriate stem cell migration must be minimised before obtaining a favourable potential benefit to risk calculus and to provide participants with a reasonable choice before they enrol in clinical studies. (shrink)

The use of neural transplantation to alleviate cognitive deficits is still in its infancy. We have an inadequate understanding of the deficits induced by different types of brain damage and their homologies in animal models against which to assess graft-induced recovery, and of the ways in which graft growth and function are influenced by factors within the host brain and the environment in which the host is operating. Further, use of fetal tissue may only be a transitory phase in (...) the search for appropriate donor sources. Nevertheless, findings from our laboratory and elsewhere have made a prima facie case for successful cognitive reconstruction by graft methods. (shrink)

Despite some clinical promise, using fetal transplants for degenerative and traumatic brain injury remains controversial and a number of issues need further attention. This response reexamines a number of questions. Issues addressed include: temporal factors relating to neural grafting, the role of behavioral experience in graft outcome, and the relationship of rebuilding of neural circuitry to functional recovery. Also discussed are organization and type of transplanted tissue, the of transplant viability, and whether transplants are really needed (...) to obtain functional recovery after brain damage. (shrink)

The concept of structure, operation, and functionality, as they may be understood by clinicians or researchers using neural transplantation techniques, are briefly defined. Following Stein & Glasier, we emphasize that the question of whether an intracerebral graft is really functional should be addressed not only in terms of what such a graft does in a given brain structure, but also in terms of what it does at the level of the organism.

In lieu of an abstract, here is a brief excerpt of the content:Fetal Tissue ResearchMary Carrington Coutts (bio)I. IntroductionThe use of tissue from fetal remains for transplantation and biomedical research has become a controversial issue in recent years, involving scientists, doctors, patients, and the federal government. Fetal tissue is potentially useful in a wide range of treatments for a number of serious diseases, some of them affecting millions of people. Despite the promise, transplantation research using fetal tissue from induced abortion (...) slowed dramatically in the U.S. in 1988, when a moratorium was declared on federal funding for such research involving humans. That moratorium was lifted by President Clinton on January 21, 1993. Though the future of fetal tissue transplantation research is brighter, public debate on the issue is likely to continue, exacerbated by the "acrimonious abortion debate" (VI, Post 1991, p. 14).Using fetal tissue in biomedical research and in transplantation is not a new practice. As early as 1928 unsuccessful attempts were made to transplant fetal pancreas cells into diabetics (VII, Fichera 1928). Fetal tissue was used effectively in biomedical research during the 1950s, and was instrumental in the culture of the polio virus, which led to the development of the polio vaccine. Fetal tissue cultures were also essential in the development of the rubella vaccine, and continue to be used in virology research. Transplantation of fetal thymus cells into patients with DiGeorge Syndrome has been recognized as effective therapy since the late 1960s.Many of the therapeutic applications involving fetal tissue are still experimental, so it is difficult to pinpoint fetal tissue transplantation's therapeutic potential. One promising application is the transplantation of human fetal brain cells into the substantia nigra of patients with Parkinson's disease to restore motor function. Fetal neural transplants have also shown promise for patients suffering from Alzheimer's disease, spinal cord and other neural tissue injuries, and possibly some forms of cortical blindness. Fetal liver cells may be useful for treatment of some kinds of bone marrow disease seen in leukemia and aplastic anemia patients. [End Page 81] Fetal tissue transplantation may also help those suffering from blood clotting disorders, such as sickle cell anemia, thalassemia, and hemophilia. Fetal pancreatic tissue has potential applications in the treatment of diabetes, especially juvenile onset diabetes. Human gene therapy may also employ embryonic and early fetal cells.The Center for Biomedical Ethics at the University of Minnesota reports that more than 1,000 patients have received transplanted fetal tissue worldwide. Countries where fetal tissue transplantation has occurred include: Australia, Canada, China, the Commonwealth of Independent States (formerly the U.S.S.R.), Cuba, Czechoslovakia, Finland, France, Germany, Great Britain, Hungary, India, Italy, Mexico, Norway, Spain, Sweden, and Yugoslavia (IV, Vawter 1992, p. 2; I, Spain 1988; VII, Reinikainen 1989).Fetal tissue has unique characteristics that make it especially valuable in some treatments. Fetal cells develop much faster than adult cells, hastening the therapeutic effect—a potentially significant benefit for gravely ill patients. They are also less likely to be rejected by transplant recipients because they are less antigenic than adult cells. This reduces the need for the exact tissue matches that can be so difficult to obtain. Fetal tissue is also easier to culture and proliferates more readily than comparable adult tissue. Furthermore, fetal tissue is in greater supply, due to the number of elective abortions.Questions about the use of fetuses and fetal tissue in biomedical research were raised in the United States in the early 1970s. Between 1969 and 1973, all 50 states enacted the Uniform Anatomical Gift Act, allowing for the donation of all or part of the body of a dead fetus for research or therapeutic research. Prospects for the use of fetal tissue increased after the Supreme Court decision in Roe v. Wade legalized abortion. As the availability of fetal tissue increased so did the concern over the potential for controversial research on living, soon-to-be-aborted fetuses, and anxiety over maltreatment of dead abortuses. Vivid examples include Geoffrey Chamberlain's 1968 report of an experiment on a fetus of 26 weeks gestational age. Delivered by hysterotomy from a 14-year-old patient, the fetus was attached to an "artificial placenta" and kept alive for more than... (shrink)

In 2008, researchers created human three-dimensional neural tissue – known as the pioneering work of “brain organoids.” In recent years, some researchers have transplanted human brain organoids into animal brains for applicational purposes. With these experiments have come many ethical concerns. It is thus an urgent task to clarify what is ethically permissible and impermissible in brain organoid research. This paper seeks (1) to sort out the ethical issues related to brain organoid research and application and (2) to propose (...) future directions for additional ethical consideration and policy debates in the field. Toward (1), this paper first outlines the current state of brain organoid research, and then briefly responds to previously raised related ethical concerns. Looking next at anticipated scientific developments in brain organoid research, we will discuss (i) ethical issues related to in vitro brain organoids, (ii) ethical issues raised when brain organoids form complexes or have relationships with other entities, and (iii) ethical issues of research ethics and governance. Finally, in pursuit of (2), we propose research policies that are mindful of the ethics of brain organoid research and application and also suggest the need for an international framework for research and application of brain organoids. (shrink)

: The transplantation of adult human neural stem cells into prenatal non-humans offers an avenue for studying human neural cell development without direct use of human embryos. However, such experiments raise significant ethical concerns about mixing human and nonhuman materials in ways that could result in the development of human-nonhuman chimeras. This paper examines four arguments against such research, the moral taboo, species integrity, "unnaturalness," and human dignity arguments, and finds the last plausible. It argues that the transfer (...) of human brain or retinal stem cells to nonhuman embryos would not result in the development of human-nonhuman chimeras that denigrate human dignity, provided such stem cells are dissociated. The article provides guidelines that set ethical boundaries for conducting such research that are consonant with the requirements of human dignity. (shrink)

This article describes two features of technoscience, which are significant for the consideration of the prospects of human improvement projects. The first feature of technoscience is that the object of its research is artificial in origin which means created by person. As an example of new objects, situations and problems are given projects to create «designer children», development of transplantation, creating implantable neural interface. The second feature of technoscience is that the well-established methods can't be applied to determine the (...) results of the implementation of human improvement projects. As an example, the article discussed neo-eugenics projects. The article concludes that today in the social sciences there is no clear position on the grounds of human improvement projects. However, this is not an obstacle for the development of technoscience. (shrink)

This book is a critical examination of the philosophical and moral issues in relation to human enhancement and the various related medical developments that are now rapidly moving from the laboratory into the clinical realm. In the book, the author critically examines technologies such as genetic engineering, neural implants, pharmacologic enhancement, and cryonic suspension from transhumanist and bioconservative positions, focusing primarily on moral issues and what it means to be a human in a setting where technological interventions sometimes impact (...) strongly on our humanity. The author also introduces the notion that death is a process rather than an event, as well as identifies philosophical and clinical limitations in the contemporary determination of brain death as a precursor to organ procurement for transplantation. The discussion on what exactly it means to be dead is later applied to explore philosophical and clinical issues germane to the cryonics movement. Written by a physician/ scientist and heavily referenced to the peer-reviewed medical and scientific literature, the book is aimed at advanced students and academics but should be readable by any intelligent reader willing to carry out some side-reading. No prior knowledge of moral philosophy is assumed, as the various key approaches to moral philosophy are outlined early in the book. (shrink)

Neurophenomenology maintains that the intelligent behavior we recognize in living beings is based on the fact that they are intentionally directed toward and are embodied and embedded in a world, which they actively constitute. This is the way in which it understands the intentionality of the mind and its meaning-making essence. Meaning-making, however, presupposes organization and synthesis of sensed reality elements within a horizon of temporality. But whence is the opening-up of this horizon given to the living? Attempts have been (...) made to “transplant” Husserl’s transcendental phenomenological analysis of temporality (“internal timeconsciousness”) into the neural infrastructure of living organisms. We critique the main available relevant views and proposals put forward, focusing on the problematic way in which they assimilate Husserl’s analysis of intentionality and temporality. After distinguishing the desiderative (ephetic) phenomena on different levels of organization of the living being, we develop the argument that temporality, in the sense of the temporal horizon of lived time, is rooted in the deepest desiderative phenomenon, that of primordial orexis. Primordial orexis is directed not toward concrete or specific objects or sensory contents, but toward evolutionarily/survivally significant values. Then, we interpret Panksepp’s psychological and behavioral neuro-ethological findings regarding a SEEKING system in dopaminergic circuits in the subcortical frontal brain as an orectic value-seeking neural system and show that Panksepp’s results underpin our idea that such a system makes possible the opening-up of the primordial temporal horizon. As an application of the idea, we claim that primordial orexis (also) relates to truth or evidence as value and, in perception, conditions the meaning-giving process leading to the evident appearing of the perceptual object as a constitution that unfolds in the context of the orectically opened-up temporal horizon. (shrink)

BackgroundNeuroethics describes several interdisciplinary topics exploring the application and implications of engaging neuroscience in societal contexts. To explore this topic, we present Part 3 of a four-part bibliography of neuroethics’ literature focusing on the “ethics of neuroscience.”MethodsTo complete a systematic survey of the neuroethics literature, 19 databases and 4 individual open-access journals were employed. Searches were conducted using the indexing language of the U.S. National Library of Medicine. A Python code was used to eliminate duplications in the final bibliography.ResultsThis bibliography (...) consists of 1137 papers, 56 books, and 134 book chapters published from 2002 through 2014, covering ethical issues in neuroimaging, neurogenetics, neurobiomarkers, neuro-psychopharmacology, brain stimulation, neural stem cells, neural tissue transplants, pediatric-specific issues, dual-use, and general neuroscience research issues. These works contain explanations of recent research regarding neurotechnology, while exploring ethical issues in future discoveries and use. (shrink)

Stem cells derived from pluripotent cells offer the hope of new treatments for diseases for which current therapy is inadequate. Clinical trials are essential in developing effective and safe stem cell therapies and fulfilling this promise. However, such clinical trials raise ethical issues that are more complex than those raised in clinical trials using drugs, cord blood stem cells, or adult stem cells. Several clinical trials are now being carried out with stem cells derived from pluripotent cells, and many more (...) can be expected in light of the rapid scientific progress in the field.Degenerative neurological diseases are desirable targets for stem cell clinical trials. The FDA has approved Phase 1 clinical trials of neural stem cell transplantation for Batten Disease, Pelizaeus-Merzbacher Disease, and spinal cord injury. In Parkinson Disease, stem cell transplantation could correct the primary pathophysiological defect — inadequate levels of the neurotransmitter dopamine. Current treatment is unsatisfactory in late-stage PD. (shrink)

Organoids are three-dimensional biological structures grown in vitro from different kinds of stem cells that self-organise mimicking real organs with organ-specific cell types. Recently, researchers have managed to produce human organoids which have structural and functional properties very similar to those of different organs, such as the retina, the intestines, the kidneys, the pancreas, the liver and the inner ear. Organoids are considered a great resource for biomedical research, as they allow for a detailed study of the development and pathologies (...) of human cells; they also make it possible to test new molecules on human tissue. Furthermore, organoids have helped research take a step forward in the field of personalised medicine and transplants. However, some ethical issues have arisen concerning the origin of the cells that are used to produce organoids and their properties. In particular, there are new, relevant and so-far overlooked ethical questions concerning cerebral organoids. Scientists have created so-called mini-brains as developed as a few-months-old fetus, albeit smaller and with many structural and functional differences. However, cerebral organoids exhibit neural connections and electrical activity, raising the question whether they are or will one day be somewhat sentient. In principle, this can be measured with some techniques that are already available, which are used for brain-injured non-communicating patients. If brain organoids were to show a glimpse of sensibility, an ethical discussion on their use in clinical research and practice would be necessary. (shrink)

Research with human–animal chimera raises a number of ethical concerns, especially when neural stem cells are transplanted into the brains of non-human primates . Besides animal welfare concerns and ethical issues associated with the use of embryonic stem cells, the research is also regarded as controversial from the standpoint of NHPs developing cognitive or behavioural capabilities that are regarded as “unique” to humans. However, scientists are urging to test new therapeutic approaches for neurological diseases in primate models as they (...) better mimic human physiology than all current animal models. As a response, various countries have issued reports on the topic. Our paper summarizes the ethical issues raised by research with human–animal brain chimeras and compares the relevant regulatory instruments and different recommendations issued in national reports from three important European research nations: Germany, Switzerland and the United Kingdom. We assess and discuss the focus and priorities set by the different reports, review various reasons for and perspectives on the importance of the brain in chimera research, and identify critical points in the reports that warrant further specification and debate. (shrink)

Microbes in the gastrointestinal tract are under selective pressure to manipulate host eating behavior to increase their fitness, sometimes at the expense of host fitness. Microbes may do this through two potential strategies: (i) generating cravings for foods that they specialize on or foods that suppress their competitors, or (ii) inducing dysphoria until we eat foods that enhance their fitness. We review several potential mechanisms for microbial control over eating behavior including microbial influence on reward and satiety pathways, production of (...) toxins that alter mood, changes to receptors including taste receptors, and hijacking of the vagus nerve, the neural axis between the gut and the brain. We also review the evidence for alternative explanations for cravings and unhealthy eating behavior. Because microbiota are easily manipulatable by prebiotics, probiotics, antibiotics, fecal transplants, and dietary changes, altering our microbiota offers a tractable approach to otherwise intractable problems of obesity and unhealthy eating. (shrink)

Cerebral organoid models in-of-themselves are considered as an alternative to research animal models. But their developmental and biological limitations currently inhibit the probability that organoids can fully replace animal models. Furthermore, these organoid limitations have, somewhat ironically, brought researchers back to the animal model via xenotransplantation, thus creating hybrids and chimeras. In addition to attempting to study and overcome cerebral organoid limitations, transplanting cerebral organoids into animal models brings an opportunity to observe behavioral changes in the animal itself. Traditional animal (...) ethics frameworks, such as the well-known three Rs (reduce, refine, and replace), have previously addressed chimeras and xenotransplantation of tissue. But these frameworks have yet to completely assess the neural-chimeric possibilities. And while the three Rs framework was a historical landmark in animal ethics, there are identifiable gaps in the framework that require attention. The authors propose to utilize an expanded three Rs framework initially developed by David DeGrazia and Tom L. Beauchamp, known as the Six Principles (6Ps). This framework aims to expand upon the three Rs, fill in the gaps, and be a practical means for assessing animal ethical issues like that of neural-chimeras and cerebral organoid xenotransplantation. The scope of this 6Ps application will focus on two separate but recent studies, which were published in 2019 and 2020. First, they consider a study wherein cerebral organoids were grown from donors with Down syndrome and from neurotypical donors. After these organoids were grown and studied, they were then surgically implanted into mouse models to observe the physiological effects and any behavioral change in the chimera. Second, they consider a separate study wherein neurotypical human embryonic stem cell-derived cerebral organoids were grown and transplanted into mouse and macaque models. The aim was to observe if such a transplantation method would contribute to therapies for brain injury or stroke. The authors place both studies under the lens of the 6Ps framework, assess the relevant contexts of each case, and provide relevant normative conclusions. In this way, they demonstrate how the 6Ps could be applied in future cases of neural-chimeras and cerebral organoid xenotransplantation. (shrink)

The use of human brain tissue in neuroscience research is increasing. Recent developments include transplanting neural tissue, growing or maintaining neural tissue in laboratories and using surgically removed tissue for experimentation. Also, it is likely that in the future there will be attempts at partial or complete brain transplants. A discussion of the ethical issues of using human brain tissue for research and brain transplantation has been organized around nine broadly defined topic areas. Criteria for human brain (...) tissue transplantation and laboratory use of brain tissue are proposed. (shrink)

The choroid plexuses (CPs) are involved in the most-basic aspects of neural function including maintaining the extracellular milieu of the brain by actively modulating chemical exchange between the CSF and brain parenchyma, surveying the chemical and immunological status of the brain, detoxifying the brain, secreting a nutritive “cocktail” of polypeptides and participating in repair processes following trauma. This diversity of functions may mean that even modest changes in the CP can have far-reaching effects. Indeed, changes in the anatomy and (...) physiology of the CP have been linked to aging and several CNS diseases. It is also possible that replacing diseased or transplanting healthy CP might be useful for treating acute and chronic brain diseases. This review focuses on the wide-ranging and under-appreciated functions of the CP, alterations of these functions in aging and neurodegeneration, and recent demonstrations of the therapeutic potential of transplanted CP for neural trauma. BioEssays 27:262–274, 2005. © 2005 Wiley Periodicals, Inc. (shrink)

This article describes two features of technoscience, which are significant for the consideration of the prospects of human improvement projects. The first feature of technoscience is that the object of its research is artificial in origin which means created by person. As an example of new objects, situations and problems are given projects to create «designer children», development of transplantation, creating implantable neural interface. The second feature of technoscience is that the well-established methods can't be applied to determine the (...) results of the implementation of human improvement projects. As an example, the article discussed neo-eugenics projects. The article concludes that today in the social sciences there is no clear position on the grounds of human improvement projects. However, this is not an obstacle for the development of technoscience. (shrink)

The extent of neurogenesis in Drosophila is under the control of the so‐called neurogenic genes, named for their mutant phenotype of causing neural hyperplasia. Their wild‐type products appear to be responsible for a signal chain that decides the fate of ectodermal cells in the embryo. Various kinds of data, from cell transplantation experiments as well as from genetic and molecular analyses, suggest that the proteins encoded by the genes Notch and Delta may act at the membrane of the signal‐transmitting (...) cells to provide a ligand to a still unknown receptor molecule; in contrast, the locus of Enhancer of split codes for several functions related to the transduction and further processing of the signal. (shrink)

It is often presumed that effects of neural tissue transplants are due to release of neurotransmitter. In many cases, however, effects attributed to transplants may be related to phenomena such as trophic effects mediated by glial cells or even tissue reactions to injury. Any conclusion regarding causation of graft effects must be based on the control groups or other comparisons used. In human clinical studies, for example, comparing the same subject before and after transplantation allows for many (...) interpretations of the causes of clinical changes. (shrink)