Blood donations may one day be a thing of the past thanks to the creation of the first functional red blood cells grown in the lab. The cells were grown from human embryonic stem cells (ESCs).

"You wouldn't have to worry about shortages because you could create as many as you want," says Robert Lanza, chief scientist at Advanced Cell Technology, the company that grew the red blood cells in Worcester, Massachusetts.

The breakthrough raises the prospect of mass-producing supplies of the "universal donor" blood type O-negative, which is prized because it can be safely transfused into any patient, whatever their blood group. This type of blood is in short supply – around 8% of Caucasians have it, and just 0.3% of Asians.

Making blood from a few ESC lines instead of obtaining it from countless donors may also help to stop the spread of disease, as it is easier to ensure such artficial blood is free of pathogens such as HIV and the viruses that cause hepatitis.

To create the red blood cells, Lanza and his collaborators at the Mayo Clinic in Rochester, Minnesota, and at the University of Illinois in Chicago exposed cultures of human ESCs to a sequence of nutrients and growth factors. This turned them first into haemangioblasts, which are precursors to blood cells, and then into mature red blood cells.
Empty cells

The team's crucial achievement was getting the cells to expel their nuclei, just as they would in the body. "Experts said it was impossible, and we were pretty surprised ourselves when it worked," said Lanza.

Researchers had previously grown blood cells from ESCs, but never achieved this "enucleation" step, which is important beceause it means the cells can't divide and become cancerous. The key seems to be to grow the blood cells on connective "stromal" cells from the bone marrow, where blood cells are made in the body.

Tests on the red blood cells suggest that they deliver oxygen just as efficiently as donated red blood cells. The team was also able to produce the red blood cells in bulk, creating populations of as many as 100 billion cells.

However, the team has not yet been able to make O-negative red blood cells. This is because blood type is determined by the genes of the ESCs, and none of the ESC lines approved for use in the US are O-negative.
Universal blood

Lanza says it should still be possible to make this prized blood using skin cells from O-negative donors. Previous research has shown that adult cells can be "reprogrammed" to return to an embryonic state by using viruses to insert genes that erase a cell's developmental history.

Like ESCs, such "induced pluripotent stem cells" (iPSCs) can be coaxed to turn into other cell types. Since they have the advantage of not requiring an embryo, iPSCs could potentially be used to make blood of all types without the moral dilemmas associated with using embryos.

A spokeswoman from the American Red Cross says the breakthrough is "an important step towards the possibility of growing transfusible red blood cells in the laboratory". The next step is to test that the cells are safe and functional in animals, says Lanza.

Journal reference: Blood, DOI: 10.1182/Blood-2008-05-157198