The ethics of human-animal chimeras?
Chimeras are organisms composed of cells or tissues from more than one individual. Chimeras have been produced for research for many years, but when human and animal cells are mixed in the laboratory, there is a clear need for heightened ethical consideration. Cells from different organisms can be combined either in the early developmental stages (for example, introducing human cells into a mouse blastocyst to observe certain developmental processes) or after an individual is fully developed (for example, implanting human stem cells-derived pancreatic cells into a mouse to test their ability to function in a living body). Chimeras are considered essential for advancing stem cells research to viable therapies, since no therapy can be tested in humans without research in animals first,