U.S. researchers reported that they have devised a way to grow red blood cells in limitless quantities in the lab by using embryonic stem cells. Published online by the journal Blood, the findings by the Advanced Cell Technology, Massachusetts, represent a significant technical advance but needed several key improvements before they could be considered as a reliable and realistic alternative to donor blood.

Dr. Robert Lanza, scientific director of the company said, "I think it's really a big break for us."   He is one of the few commercial ventures trying to make a business out of the emerging stem cell field. This technology uses stem cells taken from embryos and has the ability to produce any cell type. Dubbed as the body’s master cells, stem cells replenish various cells and tissues as they die. They are looked at as the ideal way for doctors to study disease and doctors hope to use them to provide customized transplants to patients. The only hitch that is foreseen is that the patient’s immune system may reject tissues that have been grown from someone else’s stem cells.

Lanza and colleagues at the University of Illinois at Chicago and the Mayo Clinic feel red blood cells may be an exception to this rule as they do not have a nucleus. "You don't have to worry about the DNA going haywire," he said.

"The ability to, on-demand, make as much as you want is obviously very, very attractive," Lanza said. He foresees being able to grow batches of cells from human embryos in all the different blood types of A, B, O, AB in both Rh versions of negative and positive. Lanza feels O negative would be the most desirable as it is a universal blood type and can be safely transfused to any other blood type person.

Embryonic stem cells were first coaxed into differentiating into blood precursor cells and then researchers found a way to make them change into erythrocytes or the red blood cells that carry oxygen through the body. The researchers said these cells carried the oxygen and seemed capable of delivering it to the tissue. "We can currently generate up to a 100 billion red blood cells from a single six-well plate of stem cells," Lanza said

Due to the controversial nature of the embryonic stem cell research involving the use of human embryos, the U.S. federal government limits its funding towards it.  Lanza and his team are attempting to use induced pluripotent stem cells which are ordinary skin cells and several genes that re-program them back to an embryonic-like state, to make blood cells.

"Right now, it's tough," said Lanza, who felt funding was difficult for such research.  "For a while we had the phones off. It's tough going but the people who are here, we believe in this and we are riding it out."