The stem cells that produce our blood have been created in the lab for the first time. These could one day be used to treat people who have blood diseases and leukaemia with their own cells, rather than bone marrow transplants from a donor. They could also be used to create blood for transfusions.

“This is a very big deal,” says Carolina Guibentif at the University of Cambridge, who was not involved in the research. “If you can develop [these cells] in the lab in a safe way and in high enough numbers, you wouldn’t be dependent on donors.”

In a healthy adult, blood stem cells are found in bone marrow, where they replenish the supply of red and white blood cells and platelets. “They are sort of master cells,” says George Daley at Harvard Medical School.

When these cells don’t work properly, they fail to maintain an adequate supply of blood cells. As a result, not enough oxygen reaches the body’s tissues. This can cause serious disease if organs such as the heart are affected. Blood stem cells can also be wiped out by chemotherapy for leukaemia and other cancers.

People with these disorders tend to be treated with bone marrow – complete with blood stem cells – from a healthy donor. The difficulty is finding a match. There is a one in four chance of achieving this from a healthy sibling, but the odds are slashed to one in a million if a stranger needs to be found, says Daley.

Making cells

In an attempt to create blood stem cells in the lab, Daley and his colleagues started with human pluripotent stem cells – which have the potential to form almost any other type of body cell.

The team then searched for chemicals that might encourage these to become blood stem cells.

After studying the genes involved in blood production, the researchers identified proteins that control these genes and applied them to their stem cells.

They tested many combinations of the proteins, and found five that worked together to encourage their stem cells to become blood stem cells. When they put these into mice, they went on to produce new red and white blood cells and platelets. “It’s very cool,” says Daley. “We’re very excited about the results.”

A separate team has achieved the same feat with stem cells taken from adult mice. Raphael Lis at Weill Cornell Medical College in New York and his colleagues started with cells taken from the walls of the animals’ lungs, based on the idea that similar cells in an embryo eventually form the body’s first blood stem cells. The team identified a set of four factors that could encourage these lung stem cells to make them.

Big step forward

Both sets of results represent a “breakthrough”, says Guibentif. “This is something people have been trying to achieve for a long time,” she says. By working with adult mouse epithelial cells, Lis and his team show that the feat could potentially be achieved with cells taken from an adult person. Daley’s team used human stem cells that could in theory be made from skin cells, bolstering the prospect that lab-made human blood could be next.

The lab-made stem cells are not quite ready to be used in people just yet, says Daley. Although all of his mice were healthy throughout the experiments, there is a risk that the cells could mutate and cause cancer. And the cells are not quite as efficient at making blood as those found in the body.

But once Daley and his team have honed their procedure, they might be able to make platelets and red blood cells for hospital use. These cell types don’t have a nucleus, so are unable to divide and potentially cause cancer. He hopes this procedure could be used within the next couple of years.

Eventually, Daley hopes his cells could be used to create whole blood suitable for transfusions. Not only would such a supply be more reliable than that from donors, but it would also be free of disease. “When new pathogens like Zika pop up, you have to make sure that blood is safe,” says Daley. “We’d be able to have more quality control.”