Ethical aspects of creating human–nonhuman chimeras capable of human gamete production and human pregnancy

Monash Bioeth. Rev. (2015) 33:181–202 DOI 10.1007/s40592-015-0031-1 ORIGINAL ARTICLE Ethical aspects of creating human–nonhuman chimeras capable of human gamete production and human pregnancy César Palacios-González1 Published online: 12 October 2015  The Author(s) 2015. This article is published with open access at Springerlink.com Abstract In this paper I explore some of the moral issues that could emerge from the creation of human–nonhuman chimeras (HNH-chimeras) capable of human gamete production and human pregnancy. First I explore whether there is a cogent argument against the creation of HNH-chimeras that could produce human gametes. I conclude that so far there is none, and that in fact there is at least one good moral reason for producing such types of creatures. Afterwards I explore some of the moral problems that could emerge from the fact that a HNH-chimera could become pregnant with a human conceptus. I focus on two sets of problems: problems that would arise by virtue of the fact that a human is gestated by a nonhuman creature, and problems that would emerge from the fact that such pregnancies could affect the health of the HNH-chimera. Keywords Chimeras
Human gametes
Xenopregnancy
Human–nonhuman chimeras
Biotechnology
Part human 1 Introduction In the second half of the twentieth century, interspecific chimeras went from the realm of mythology and literary studies to being created and studied by the faculties of life sciences around the world. Today, most human–nonhuman chimeras (henceforth HNH-chimeras) are used to investigate and model human biological functions and diseases that would be difficult to study in other settings (e.g. cell cultures or computer simulations). & César Palacios-González 1 Institute for Science Ethics and Innovation, The University of Manchester, Room 3.383, Stopford Building, Oxford Road, Manchester M13 9PL, UK 123 182 C. Palacios-González Chimeras are formed by combining whole cells of genetically different organisms into a single functional organism. The UK Academy of Medical Sciences provides this definition: Chimæras are formed by mixing together whole cells originating from different organisms. The new organism that results is made up of a ‘‘patchwork’’ of cells from the two different sources. Each cell of a chimæra contains genes from only one of the organisms from which it is made. (…) Primary chimæras are formed by mixing together two early embryos, or an early embryo with isolated embryonic cell types obtained from a different embryo or cultured stem cell line. The resulting chimæra has cells of different origins, in many tissues. Secondary chimæras are formed experimentally by transplanting (or grafting) cells or tissues into animals at later stages of development, including late fetal stages, post-natal or even adult animals. The donor cells are only present in a few tissues (The Academy of Medical Sciences 2011, pp. 18–19). HNH-chimeras (in particular humanized mice) have been used in research into human autoimmunity, hematopoiesis, and cancer biology (Shultz et al. 2007). They may further serve in the development of vaccines against deadly diseases (Bhan et al. 2010; Davis and Stanley 2003; Sacci Jr. et al. 2006), and the development of human organs for transplantation (Rashid et al. 2014). It should be emphasised that the number and origin of the cells, and the timing of the mixing could produce very different outcomes in respect to the kinds of characteristics a chimera could possess (Greely et al. 2007; Karpowicz et al. 2005; The Academy of Medical Sciences 2011). In most respects, the creation and use of HNH-chimeras for research purposes is not regarded as presenting additional ethical concerns alongside those related to the destruction of human embryos, animal ethics, and research ethics. In part, this has been the case because such entities have been predominantly constituted by nonhuman components, with only a few human cells. Nonetheless, there are three specific types of HNH-chimeras that have raised red flags among policymakers, researchers, and ethicists: (1) (2) (3) HNH-chimeras that could have brains predominantly constituted by human brain cells; HNH-chimeras that could look human-like; HNH-chimeras capable of human gamete production and human pregnancy. Of these three cases, the one that has generated the most academic debate is the possible creation of HNH-chimeras with brains predominantly constituted by human brain cells (e.g. the neuron mouse, Greely et al. 2007). The other two cases have not been comprehensively explored; I presume that this is in part due to the fact that the ethics debate around the creation of HNH-chimeras is fairly recent. In fact, only Greely (2013) has explored some of the ethical issues regarding the creation of these three types of ‘sensitive’ cases. The aim of this paper is to further discuss the moral 123 Ethical aspects of creating human–nonhuman chimeras capable… 183 issues surrounding the creation of HNH-chimeras capable of human gamete production and human pregnancy. At this point, someone could state that the ethics of creating HNH-chimeras capable of human gamete production and human pregnancy has been dealt with by three major advisory groups (the UK Academy of Medical Sciences, the German Ethics Council, and the US Committee on Guidelines for Human Embryonic Stem Cell Research), and that all of them have recommended either not creating HNHchimeras that could produce human gametes or not letting HNH-chimeras breed. To such a claim I would reply that these three groups have only stated that such courses of action should not be taken; they have not elaborated on the ethical reasons that ground such prescriptive measures. Next I present the recommendations of these groups. The Academy of Medical Sciences has stated that: A very narrow range of experiments should not, for now, be licensed because they either lack compelling scientific justification or raise very strong ethical concerns. The list of such experiments should be kept under regular review by the proposed national expert body, but should at present include: (…) Breeding of animals that have, or may develop, human derived germ cells in their gonads, where this could lead to the production of human embryos or true hybrid embryos within an animal (The Academy of Medical Sciences 2011, p. 111). The Committee on Guidelines for Human Embryonic Stem Cell Research has recommended that: Embryonic Stem Cell Research Oversight (ESCRO) committees or their equivalents should divide research proposals into three categories [a, b and c] in setting limits on research and determining the requisite level of oversight: (…) (c) Research that should not be permitted at this time. (…) (iii) No animal into which hES cells have been introduced at any stage of development should be allowed to breed (National Academies of Science 2005, p. 58). While the US and UK groups focused on the reproduct (...truncated)