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The dependance on donor blood used for all kinds of medical purpose may be decreased now finally thanks to RED blood cells generated in a lab that have been successfully injected into a human volunteer for the first time. Luc Douay, of Pierre and Marie Curie University, Paris, extracted hematopoietic stem cells from a volunteer's bone marrow, and encouraged these cells to grow into red blood cells with a cocktail of growth factors. Douay's team labeled these cultured cells for tracing, and injected 10 billion of them (equalling 2 milliliters of blood) back into the marrow donor's body.

After five days, 94 to 100 per cent of the cells remained in circulation, while after 26 days, 41 to 63 per cent remained - a survival rate comparable to normal red blood cells. The cultured blood cells also gave every indication of being safe to use: they didn't transform into a malignant cell type, for example. Instead, they behaved like normal red blood cells, binding to oxygen and releasing it

This is great news for international health care. "The results show promise that an unlimited blood reserve is within reach," says Douay. The world is in dire need of a blood reserve, even with the rising donor numbers in the developed world. This need is even higher in parts of the world with high HIV infection rates, which have even lower reserves of donor-worthy blood.

Previously a type of synthetic blood was used to save a life but that was derived from cow's blood. The advantage it has that it doesn't require matching and can be stored without refrigeration for upto three years.

The stem cell method has its own pros, though. "The advantage of stem cell technology is that the product will much more closely resemble a red cell transfusion, alleviating some of the safety concerns that continue around the use of the current generations of artificial products," says Cooper.

Douay's next challenge is to scale up production to a point where the cultured blood cells can be made quickly and cheaply in sufficient quantities for blood transfusions. The 10 billion cells his team made wouldn't go very far - a transfusion typically requires 200 times that number. With his existing technology, Douay estimates that a single transfusion would require 400 litres of culture fluid, which is clearly impractical. "We are still a long way from the vision of dropping a couple of stem cells into the broth and making endless units of blood," says John Hess of the University of Maryland in Baltimore.

Douay believes that it may take several years to scale up the technology. Another possibility is to use embryonic stem cells instead, as Lanza did in 2008. "We can generate up to 100 billion red blood cells from a single six-well plate of stem cells," Lanza says.

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