Chimeras are formed by combining genetically-distinct cells, in this case human cells and animal cells. When discussing human-animal chimeras it is important to note the type of human cells being used (sexual cells, somatic cells, embryonic or adult stem cells, or induced pluripotent stem cells) as well as the possible resulting combinations and the consequences of mixing them. Judging the morality of these combinations can be complex.
Analysis Of Some Of The Experiments
Juan Carlos Izpisúa Belmonte, a developmental biologist at the Salk Institute for Biological Studies in San Diego, California, wants to mix human stem cells into very early animal embryos and let them develop, a strategy that could produce undetermined tissues or organs for transplantation.
If the human stem cells to be used are embryonic, then it is necessarily implied that a five-day-old human embryo was destroyed in order to obtain them. As we have discussed on a number of occasions, using such cells is morally illict. Period. Even if tissues or organs were eventually produced for transplant, taking the life of an embryo, even in order to heal someone else, cannot be justified. While the therapeutic principle, might allow a lesser evil be caused that a greater evil might be avoided (e.g. amputating a leg to save a body), such actions are permissible only on the same patient. You cannot take one life to save another.
Izpisúa Belmonte and others also want to create specific organs or tissues, such as the pancreas, in an animal embryo. They hope to form a human pancreas in the developing animal by injecting human pluripotent stem cells into pig embryos. They have now made chimeras that have developed for 2 to 3 weeks.
In this research, Izpisúa Belmonte uses the term human pluripotent stem cells. This is a term about which we must be very careful. Recall  that virtually all pluripotent cells come from embryos, as post-natal stem cells are usually only mutipotent. Also, it is unlikely that they are using post-natal cells because one doesn’t need to make an organ outside of the patient’s body using such cells. If using the term human pluripotent cells is a euphemism for embryonic stem cells, then this research, too, takes the life of a child and is illicit.
Hiromitsu Nakauchi’s project at the University of California and at Stanford, is to inject human induced pluripotent stem cells (IPSC ) into sheep embryos.
IPSCs are formed by the reprogramming of somatic cells (in this case skin cells), back into “embryonic-like” stem cells. This sounds well and good. However, the term “embryonic-like” is confusing since there is no biological difference between embryonic-like stem cells and embryonic stem cells. In reprogramming, the cells sometimes pass through a stage called an embryoid, a stage about which there is some debate . Furthermore, IPSCs can trigger cancer-causing genes and this too should be considered.
The stage of development of the animal embryo is also not clear. They speak of very early animal embryos. If the cells are actually injected into an enucleated animal zygote, the process would actually be a form of altered nuclear transfer, or cloning. Because the genetic material transferred is human, it could result in human cloning. This, too, is illicit.
Analysis Of The Position Of NIH
Izpisúa Belmonte asked  for the Pioneer Award from the U.S. National Institutes of Health (NIH); $500,000 annually for 5 years. On 23 September 2015, NIH issued a notice  saying that it will not fund such research, though it has invited scientists and bioethicists to a meeting on 6 November 2015 to discuss the ethical questions raised by such experiments.
In 2005, the U.S. National Research Council and the Institute of Medicine recommended limits on such research, among them that no human stem cells be added to primate embryos and that animal-human chimeras not be allowed to breed (Science, 29 April 2005, p. 611). Current NIH funding guidelines, finalized in 2009, reflect those recommendations. They prohibit breeding animals in which human stem cells might have become sperm or eggs, and they rule out primate-human experiments. They do not, however, prohibit injecting human pluripotent cells into the embryos of other animals and letting the chimeras develop.
We can see how in 10 years, ethical positions have been progressively relativized as several bioethical currents view the embryo as an object to be used for the benefit of others, rather than a human life with intrinsic value and dignity. Sadly, where objections to these currents are rightfully raised, language is twisted and manipulated to disguise the truth of what is taking place. It is a clever tactic requiring that we be ever vigilant.
In the realm of stem cell research, the focus should be placed on post-natal stem cells. This is the research which is bringing results and the research which places science at the service of the person rather the person at the service of science. These cells don’t trigger cancer-causing genes, and the method of acquiring them is correct.
If, however, the objectification of the person continues, don’t be surprised if chimeras come to be accepted, if the prohibition against using stem cells to create sperm or ova is removed, or if experiments with humans and primates are carried out, for science without a conscience is nothing more than the destruction of mankind.