This article is the lead piece in a special report that presents the results of a bioethical investigation into chimeric research, which involves the insertion of human cells into nonhuman animals and nonhuman animal embryos, including into their brains. Rapid scientific developments in this field may advance knowledge and could lead to new therapies for humans. They also reveal the conceptual, ethical, and procedural limitations of existing ethics guidance for human‐nonhuman chimeric research. Led by bioethics researchers working closely with an (...) interdisciplinary work group, the investigation focused on generating conceptual clarity and identifying improvements to governance approaches, with the goal of helping scholars, funders, scientists, institutional leaders, and oversight bodies (embryonic stem cell research oversight [ESCRO] committees and institutional animal care and use committees [IACUCs]) deliver principled and trustworthy oversight of this area of science. The article, which focuses on human‐nonhuman animal chimeric research that is stem cell based, identifies key ethical issues in and offers ten recommendations regarding the ethics and oversight of this research. Turning from bioethics’ previous focus on human‐centered questions about the ethics of “humanization” and this research's potential impact on concepts like human dignity, this article emphasizes the importance of nonhuman animal welfare concerns in chimeric research and argues for less‐siloed governance and oversight and more‐comprehensive public communication. (shrink)

In this conversation, four experts in animal research oversight—Christopher Stodgell, Lori Hill, Robert Kesterson, and Angelika Rehrig—discuss the complexities of stem cell-based chimeric animal experiments, especially in relation to traditional animal welfare practices. Each expert shares their experiences and suggestions for how best to conduct chimeric animal research, including discussing the importance of communication and collaboration between experts in animal behavior and welfare and the investigators conducting or proposing chimeric research studies.

The use of nonhuman animals in research has long been a source of bioethical and scientific debate. We consider the oversight and use of nonhuman animals in chimeric research. We conducted interviews with twelve members of embryonic stem cell research oversight committees, nine members of institutional animal care and use committees, and fourteen scientists involved in human–nonhuman‐animal chimeric research in different areas of the United States. Interviews addressed animal welfare and conceptual issues associated with moral status and humanization of nonhuman (...) animals that contain human cells. Our findings suggest that concepts of enhanced moral status and consciousness are not very useful in human–nonhuman‐animal chimeric research in part because their meanings are not easily defined, which presents challenges to applying the concepts in research. Instead, scientists and oversight committee members we interviewed seemed to rely on standard assessments of changes in animal welfare when focusing on the ethics of human‐animal chimeric research. (shrink)

In this conversation, three researchers from the fields of developmental biology and stem cell science—Ali Brivanlou, Lorenz Studer, and May Schwarz—speak about the importance of conducting chimeric animal experiments. The scientists describe some of the stem cell-based chimeric research being conducted in the United States, responsibilities they have in using modified animals for experiments, and things they would like the public to understand about this research. This conversation illuminates not only what chimeric animal researchers are doing in the lab but (...) also how their work may benefit society and where this science might go in the future. (shrink)