Scientists spark ethics fears after planting human cells in monkey embryos

US scientists have grown human cells in monkey embryos with the aim of understanding more about how cells develop and communicate with each other.

Researchers from the Salk Institute in California have produced what is known as monkey-human chimeras, with human stem cells – special cells that have the ability to develop into many different cell types – inserted in macaque embryos in petri dishes in the lab.

However, some ethicists in the UK have raised concerns, saying this type of work “poses significant ethical and legal challenges” and “opens Pandora’s box to humannon-human chimeras”.

They are calling for a public discussion about the ethical and regulatory challenges associated with human-animal chimeras.

Chimeras are organisms whose cells come from two or more individuals.

In humans, chimerism can naturally occur following organ transplants, where cells from that organ start growing in other parts of the body.

The scientists, led by Professor Juan Carlos Izpisua Belmonte, say their work could pave the way in addressing the severe shortage in transplantable organs as well as help understand more about early human development, disease progression and ageing.

Prof Izpisua Belmonte said: “These chimeric approaches could be really very useful for advancing biomedical research not just at the very earliest stage of life, but also the latest stage of life.”

In 2017, Prof Izpisua Belmonte and his team created the first human-pig hybrid, where they incorporated human cells into early-stage pig tissue but found that human cells in this environment had poor molecular communication.

The team decided to investigate lab-grown chimeras using a more closely related species – macaques.

The human-monkey chimeric embryos were monitored in the lab for 19 days before being destroyed.