How might blood cells be made?

Different groups of researchers say they have developed a way of producing blood cells from human or mouse cells that have been reprogrammed in the lab – an advance that has been touted as offering a solution to the need for blood donation. The latest studies are the result of 20 years’ work in the field.

How exactly did they do it?

The two pieces of work, published at the same time in Nature but by different research groups, take differing approaches. One study, led by George Daley at Harvard Medical School, began with human cells known as “induced pluripotent stem cells” – cells that can make any type of human cell, and which can be produced by genetically “reprogramming” adult cells, such as those in skin. These were chemically tinkered with to create a tissue that can give rise to blood stem cells and implanted into mice, where blood stem cells were made, which then churned out the different types of cells found in blood, including white blood cells and red blood cells. The approach also worked starting with human embryonic stem cells.

“The big achievement is being able to do that transition from a pluripotent stem cell to a blood stem cell, which has never been [done] before,” said Cedric Ghevaert of the Cambridge Blood Centre at the University of Cambridge. “That is a big story and there is no denying the impact of that.”

The other research, led by Raphael Lis, at Weill Cornell Medical College in New York, took a different tack, converting cells taken from the lungs of mice directly into blood stem cells. Once implanted into mice, they too churned out the panoply of blood cells.

Will these breakthroughs remove the need for blood donation?

No. Both of the approaches ultimately produced a collection of different types of blood cells. This, said Ghevaert, is not so useful for transfusions, where particular components of blood, for example, red blood cells, are needed separately. Instead, the research is more relevant for patients who need bone marrow transplants, for example, those with leukaemia.

“This is what you get when you get a bone marrow transplant – you’re given another person’s stem cells,” said Ghevaert. “That has got drawbacks because that other person is never quite a complete match to you, which is why bone marrow transplant is quite a serious procedure. For years we have been asking the question: ‘Could we make the blood stem cells from something else that belongs to the patients that needs those stem cells?’” he added. “This [research] shows the first glimpse of hope.” However, there is still some way to go. “They have generated enough to transplant a mouse, but if you wanted to transplant a human or indeed produce vast vats of blood cells, you would need an awful lot more – and by that, I don’t mean even 10 times more, you would need 1,000, 100,000 cells,” said Ghevaert. “One of biggest problems in this is the manufacturing process, because there is no point in making a pint of blood that costs £1m.” As for the second approach, carried out in mice alone, Ghevaert is more cautious. “I have seen a lot of very good things done in mice that then don’t translate to anything in humans.”

Is anyone trying to make blood for transfusions?

Yes, a number of researchers around the world are attempting to manufacture specific components of blood, including Ghevaert, who has been working on using human pluripotent stem cells to produce platelets (the component of blood that helps it to clot).

Is laboratory blood better than donated blood?

It depends. Blood given in a transfusion has to be of the right type, matching the recipient’s blood group. For most people, transfusion from donor blood will continue to be the norm – such blood is cheap, readily available and safe. But blood manufactured in a laboratory could help some. “The only advantage of producing cells in the lab is, for example, to make blood cells that are compatible with patients who are very difficult to transfuse because we simply can’t find them a blood group match,” said Ghevaert. “Donated blood works extremely well for 99.99% of people, therefore I think we have to see these products as a niche product.”

Manufactured blood, said Ghevaert, could be a boon in developing countries. “If you consider countries where the rate of HIV is 30%, and hepatitis B 60%, finding safe blood is extremely difficult,” he said. “Manufactured blood in a country where you have endemic viral infections that make the blood supply extremely unsafe, that would be extremely relevant.”

Does all this mean that we don’t need to give blood any more?

No. A spokesperson for NHS Blood and Transplant said: “It will be some time before this research leads to manufactured blood cells being used for patient treatment. Volunteer donors remain a vital lifeblood for patients and will remain so for many years to come.”

∆