At the Edge of Humanity: Human Stem Cells, Chimeras, and Moral Status

Abstract

Experiments involving the transplantation of human stem cells and their derivatives into early fetal or embryonic nonhuman animals raise novel ethical issues due to their possible implications for enhancing the moral status of the chimeric individual. Although status-enhancing research is not necessarily objectionable from the perspective of the chimeric individual, there are grounds for objecting to it in the conditions in which it is likely to occur. Translating this ethical conclusion into a policy recommendation, however, is complicated by the fact that substantial empirical and ethical uncertainties remain about which transplants, if any, would significantly enhance the chimeric individual's moral status. Considerations of moral status justify either an early-termination policy on chimeric embryos, or, in the absence of such a policy, restrictions on the introduction of pluripotent human stem cells into early-stage developing animals, pending the resolution of those uncertainties.

Research on Human-animal Entities: Ethical and Regulatory Aspects in Europe

“…It is important to avoid the reductionist view that would enshrine human dignity in stem cells and specialized tissues rather than human beings [2]. It has even been argued that chimera research, just like research on non-chimeric animal species, should be governed by animal welfare principles, sufficiently developed to protect animal research subjects of human-like mind [2,24]. d) Human/nonhuman embryonic mixtures would be less human than fully human embryos and therefore pose fewer ethical problems for research [25].…”

Advancing Neuroregenerative Medicine: a Call for Expanded Collaboration Between Scientists and Ethicists

“…A central concern, however, is that chimeras will develop brains capable of human-like cognitive or mental characteristics [64]. Indeed, the bulk of the ethics literature on stem cells in NRM has centered chiefly on whether scientists would "confer humanity" on these animals [e.g., 25,31,32,53,59]. Scientists we interviewed, however, felt such concerns were misplaced; they did not believe that a human neural-grafted animal would yield human qualities such as language, cognition, and emotion.…”

Faith-based perspectives on the use of chimeric organisms for medical research

“…However the same cannot be said for the types of interspecies chimeras created through the introduction of human embryonic stem cells into a non-human embryo or fetus (Streiffer 2005). At the cellular level these creatures are mosaics such that "individual cells are derived from either the host or the donor but not both."…”

“…Even if it is a remote possibility that a being created through this process would have enhanced or 'human-like' cognitive or psychological characteristics, the 'unnaturalness' of human-animal chimeras makes many people uncomfortable eliciting a visceral reaction against their creation (HFEA 2007;Jones 2009). Biomedical ethicists and moral philosophers have responded by interrogating arguments for and against chimeric research based on premises such as: the potential for harm to the creatures created for research (Streiffer 2005); the value of species integrity and the possible risk these creatures pose to human dignity (DeGrazia 2007; Karpowicz et al 2004;Melo-Martín 2008), and the potential harms of violating natural, legal and social categories (Eberl and Ballard 2009;Haber and Benham 2012;Robert and Baylis 2003). 1 These arguments can be respectively and loosely categorized as raising objections on the basis of concern for: the welfare of research participants; the integrity of natural processes; and, the broader social consequences of permitting chimeric research practices.…”