Donating blood saves lives, but there's never enough, especially when the difficulties of storage and matching blood types are taken into account. Artificial blood has been in the works for years, but it's held back by the fact that the stem cells it's grown from can only produce so many red blood cells. Now, researchers at the University of Bristol and NHS Blood and Transplant may have busted that barrier, by developing immortalized cell lines that can be cultured indefinitely to produce artificial blood on a much larger scale.

According to the World Health Organization (WHO), every year about 108 million donations of blood are made globally, but developing countries often miss out, lacking donor numbers as well as the capacity to store blood in large quantities and screen it for disease. To help smooth out some of those issues, previous work has grown mature red blood cells from donated stem cells to make a concoction that can be stored at room temperature, reduce the risk of disease and is compatible with any blood type.

Sounds too good to be true? At the moment, it is. The problem with these artificial substitutes is that only fairly small numbers of red blood cells can be produced before a new donation of stem cells is required, and considering one bag of blood can contain as many as two trillion red cells, mass production remains an elusive beast.

Rather than turn adult stem cells directly into mature red blood cells, the Bristol team's solution was to not cut out the middleman – in this case, premature red blood cells called erythroblasts, that then produce mature cells – but to "immortalize" these erythroblasts so a continuous supply of mature red blood cells can be generated, thereby boosting the scale of artificial blood production.

Immortalized early erythroid cells can essentially make blood cells continuously(Credit: University of Bristol)

"Previous approaches to producing red blood cells have relied on various sources of stem cells which can only presently produce very limited quantities," says Jan Frayne, first author of the study. "By taking an alternative approach we have generated the first human immortalized adult erythroid line (Bristol Erythroid Line Adult or BEL-A), and in doing so, have demonstrated a feasible way to sustainably manufacture red cells for clinical use from in vitro culture."

As important as the breakthrough is, the team is careful to note that large-scale production of artificial blood is still many years away. For now, the aim is to complement, not replace, donations, and the first people to receive the BEL-A blood will probably be those with rare blood types or chronic illnesses.

"The first therapeutic use of a cultured red cell product is likely to be for patients with rare blood groups because suitable conventional red blood cell donations can be difficult to source," says Dave Anstee, co-author of the study. "The patients who stand to potentially benefit most are those with complex and life-limiting conditions like sickle cell disease and thalassemia, which can require multiple transfusions of well-matched blood. The intention is not to replace blood donation but provide specialist treatment for specific patient groups."

NHS Blood and Transplant is planning to conduct its first human trials of artificial blood by the end of 2017, although these tests won't be of BEL-A cells, but blood manufactured through other stem cell methods.

The research was published in the journal Nature Communications.

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