Scientists said Tuesday that they had devised a way to grow large quantities of blood in the lab using human embryonic stem cells, potentially making blood drives a thing of the past.
But experts cautioned that although it represented a significant technical advance, the new approach required several key improvements before it could be considered a realistic alternative to donor blood.
The research team outlined a four-step process for turning embryonic stem cells into red blood cells capable of carrying as much oxygen as normal blood. The procedure was published online by the journal Blood.
The ability to make blood in the lab would guarantee that hospitals and blood banks have access to an ample supply of all types of blood, including the rare AB-negative and the universal donor type, O-negative.
It would also ensure that patients are never at risk of contracting diseases such as hepatitis C or HIV from donor blood, said Dr. Dan Kaufman, associate director of the University of Minnesota's Stem Cell Institute, who wasn't involved in the study.
"People don't usually think about these types of cells when they talk about human embryonic stem cell therapy, but it is important," Kaufman said. "There's more infections all the time, and the number of donors is more and more limited."
Researchers have tried to harness the so-called adult stem cells that are responsible for making blood in the body, but their methods were far too inefficient to be put to practical use, experts said.
In the new study, researchers were able to make as many as 100 billion red blood cells -- enough to fill two or three collection tubes -- from a single plate of embryonic stem cells.
After allowing the stem cells to begin the earliest stages of embryonic development, the researchers prompted some of them to grow into red blood cells by exposing them to a variety of proteins.
Up to 65% of the resulting cells matured to the point at which they shed their nucleus, which allows them to take on the distinctive doughnut shape of circulating red blood cells, said Dr. Robert Lanza, chief scientific officer at Advanced Cell Technology Inc. and the study's senior author.
The team, which also included researchers from the University of Illinois at Chicago and the Mayo Clinic in Rochester, Minn., produced blood of types A-positive, A-negative, B-positive, B-negative and O-positive.
The method was 100 times more efficient than previous efforts, said Eric Bouhassira, a professor of stem cell biology and regenerative medicine at Albert Einstein College of Medicine in New York. But most of the cells had embryonic or fetal versions of globin, the compound in red blood cells that carries oxygen. Only a relative few appeared to contain the adult globin that would be needed by patients, he said.
"Whether they would be good enough for transfusion is very unclear," said Bouhassira, who wasn't involved in the study. Lanza said the research team was conducting more experiments to see whether the stem cells would produce more adult globin if given more time to mature in the lab.
Even with substantial improvements, the method faces another big hurdle. Roger Dodd, director of the American Red Cross' Holland Laboratory in Rockville, Md., said that producing blood in the lab could cost thousands of dollars per unit -- far too expensive to replace the 14 million pints of red blood cells that are transfused every year. "It's a rather ambitious goal," Dodd said.