At UC Davis, maximum period for chimera embryos is 28 days & adult chimeras can’t mate

Report of American researchers creating chimeras has created buzz on social media. On Twitter, some users air their opinion for or against the use of half-human and half-animal embryos for medical research.

Bioethicist warn that groups experimenting with the use of chimeras, such as scientists from the University of California, Davis (UCD), could be playing God, points out Jason Roberts, bioethicist at Arizona State University. But Pablo Ross, reproductive biologist at UCD, insists he is conducting the experiments for a biomedical purpose, not to see some kind of monstrous creature.

Among the measures he has put in place to address bioethical concerns is place a time limit on the development of chimeras to 28 days which is the time that organs begin to form. Ross discloses that during this period, he removes the embryo and dissects them.

Another measure is to ensure adult chimeras are not allowed to mate. He elaborates, “We are very aware and sensitive to the ethical concerns … One of the reasons we’re doing this research the way we’re doing it is because we want to provide scientific information to inform those concerns.”

Beyond UCD, MIT Technology Review reported in January that human-animal chimeras are gestating on US research farms. It interviewed three teams, one in Minnesota and two in California, and estimates there are about 20 pregnancies of pig-human or sheep-human chimeras in the last 12 months.

The chimera research pushed through despite the reversal by the National Institutes of Health (NIH) in September 2015 of its previous policy funding such type of studies. As a result, the annual grant awarded to Salk Institute for Biological Studies developmental biologist Juan Carlos Izpisua Belmonte as part of NIH’s Pioneer Award remains in limbo, reports Sciencemag.

Although there is no scientific papers yet to describe the UCD’s work, Bemonte showed unpublished data during presentations made at the NIH Maryland campus in November to comply with the request of the agency. Another researcher from the University of Minnesota showed images of a 62-day-old pig fetus in which its congenital eye defect was reversed after human cells were added.

To add to the growing public opinion on chimeras, on Tuesday, Charles Mbava, a medical scientist in embryology-reproductive medicine, published in LinkedIn, a paper on half-human, half-animal embryos. He notes that recent controversies focus on cytoplasmic embryos created by transferring nuclei with DNA from human cells into animal oocytes, or eggs, with almost all of its genetic information removed.

Mbava says the resulting embryos are more than 99 percent human, with about 0.1 percent animal component. After it is grown in the lab for a few days, it is harvested for stem cells.

The expert cites the 2008 vote in UK’s House of Commons in favour of hybrid human-animal embryos by 336 to 176. He adds that studies point to chimeras from pigs as an answer to shortage of organs for human transplant patients and from sheep foetus for liver transplant patients.

Mbava says the concept has courted controversy because of the scientific, religious and ethical dilemmas involved.