April 16, 2021

Anna Murray 

Most recently, an event of controversial research on 132 monkey-human embryos was released to demonstrate its experimental details. A team of researchers led by Professor Juan Carlos Izpisua Belmonte, a developmental biologist at the Salk Institute for Biological Studies in La Jolla, California published on April 15 an article named "Chimeric contribution of human extended pluripotent stem cells to monkey embryos ex vivo" in the journal Cell on the first monkey embryos injected with human stem cells. In brief, members of the team had monitored human and monkey cells divide and grow together in a dish and observed at least 3 embryos survive after fertilization for 19 days.

In the past, the team has carried out a series of hybrids experiments. In 2017, they reported research findings of cow embryos grown with human cells, pig embryos grown with human cells, and rat embryos grown with mouse cells. Then, in 2019, the team published monkey embryos in a dish grow to 20 days after fertilization. Some scientists favor such human–animal hybrids, known as chimaeras, attempting to provide better test models for drugs and clone human organs for transplants. But, since 2015, the US National Institutes of Health (NIH) has banned federal funding to researches on human cells to be injected into animal embryos. 

The research has ignited debate into the ethical challenges, however, raised broad concerns about such experiments. The International Society for Stem Cell Research (ISSCR), a global, nonprofit organization that promotes excellence in stem cell science and applications to human health based at Skokie, Illinois, will tackle the issue of nonhuman-primate and human chimaeras. Meanwhile, ISSCR is expected to come up with revised international guidelines, that outlines the core principle of scientific rigor and research integrity, for stem-cell research in the coming May.

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