The Japanese Government has approved the first human-animal embryo experiments which could eventually lead to a new source of organs for transplant.
Dr Hiromitsu Nakauchi, lead researcher at the University of Tokyo and Stanford University in California, plans to grow human cells in mouse and rat embryos and then transplant them into surrogate animals. The long-term goal is to produce animals with organs made from human cells that could eventually be transplanted into people.
Dr Ronald Parchem, Baylor College of Medicine in Houston, who is not involved in the work, said: 'It has tremendous potential to help many people who are suffering from a broad variety of diseases or in need of different types of tissue or organ replacement.'
This approval follows a decision made in March by the Japanese education and science ministry, to lift a ban on allowing human-animal embryos to grow beyond 14 days and for such embryos to be transplanted into a surrogate and brought to term. As with previous hybrid embryo studies, concerns have been raised about the ethical and technical hurdles. To date, no human-animal hybrid embryos have been brought to term and the US National Institutes of Health has had a moratorium on funding such work since 2015.
In a report by Nature, Nakauchi said he 'plans to proceed slowly and will not attempt to bring any hybrid embryos to term for some time.' Tetsuya Ishii, science-policy researcher of Hokkaido University in Sapporo, added: 'It is good to proceed stepwise with caution, which will make it possible to have a dialogue with the public, which is feeling anxious and has concerns.'
Previously, researchers have had varying levels of success in growing human cells in animal embryos (see BioNews 939, 886 and 855) and some bioethicists have raised concerns about the possibility of the human cells straying beyond the targeted organ and potentially growing in the animal's brain.
In response, Nakauchi told nature: 'We are trying to do targeted organ generation, so the cells go only to the pancreas.' Dr Jun Wu, at the University of Texas Southwestern Medical Center in Dallas, added: 'Understanding the molecular basis and developing strategies to overcome this barrier [what limits the growth of human cells in animal embryos] will be necessary to move the field forward.'
On Saturday, the Guardian reported that a team of researchers led by Professor Juan Carlos Izpisúa Belmonte from the Salk Institute in the US have produced monkey-human chimeras in China; however, the details of the work have not been published.