According to the World Health Organization, approximately 107 million blood donations are collected globally every year. Nonetheless, blood is often in short supply – particularly in developing nations. Despite new safeguards, there's also still the risk of incompatibility, or of infections being transmitted from donors to recipients. Charitable organization the Wellcome Trust hopes to address these problems, by developing the ability to manufacture blood outside of the body. Last week, it announced that test subjects should begin receiving transfusions of blood made with lab-grown red blood cells by late 2016.

The research program is being led by the Scottish National Blood Transfusion Service, thanks to the Wellcome Trust's £5 million (US$8.4 million) Strategic Award grant. Institutions collaborating on the project include the University of Glasgow, the University of Edinburgh, Loughborough University, NHS Blood and Transplant, the Irish Blood Transfusion Service, Roslin Cells Ltd and the Cell Therapy Catapult, in collaboration with Bristol University and the University of Cambridge.

The project has already created type O- red blood cells that are "fit for clinical transfusion," according to a report in The Telegraph. These were manufactured from induced pluripotent stem cells.

"We must first make the stem cells become a mesoderm – one of the body layers that makes things like muscle, bone and blood – and then get it to turn into blood cells," explained the University of Glasgow's Dr. Joanne Mountford. "Then we have to make it develop into a red blood cell specifically and finally make it eject its nuclei and mature properly."

The choice of type O- is significant, as patients with all other blood types can receive it.

While it is hoped that trials on human patients could begin within three years, there's still plenty of work to be done before so-called "blood factories" are a reality.

"Every single bag of transfused blood has about two trillion red blood cells in it," said Mountford. "It’s a ludicrously high number to make in the lab. We use two million of those bags every year in the UK alone. Ensuring that any industrially produced blood can be made economically viable is quite a task."