Scientists a step closer to creating supplies of blood

American scientists have for the first time turned human embryonic stem cells into blood cells, a key step toward creating supplies of blood for medical therapies.

Researchers at the University of Wisconsin said the achievement would help scientists to understand better how blood cells developed and one day might lead to sources of laboratory-grown blood for transfusions or treatments.

"There are potential clinical therapies that may develop in the future, but it's very clear that those therapies are many years off," said Dan Kaufman, a haematologist and the study's lead author.

Embryonic stem cells are early master cells that can transform into almost any other cell type in the body. Experts believe they may eventually lead to treatments for a variety of serious conditions.

Scientists are just beginning to learn how to coax human embryonic stem cells into becoming various cell types in the laboratory.

Mr Kaufman and his colleagues placed human embryonic stem cells on a "feeder" of mouse bone marrow cells that contained nutrients to promote blood cell development. The cells were put into a medium containing a fetal bovine serum, and they grew into primitive blood cells, known as haematopoietic precursor cells.

The precursor cells, when exposed to other growth factors, then formed colonies of red blood cells, white blood cells and platelets identical to those produced from human adult bone marrow cells, according to the study published in the Proceedings of the National Academy of Sciences. Similar work had been done using mouse embryonic stem cells.

Growing blood cells from stem cells may one day help to alleviate shortages of blood needed for transfusions, or provide cells for blood or bone marrow transplants for patients with leukaemia or other cancers, Mr Kaufman said.

Scientists also believe that using blood derived from embryonic stem cells might help to stop the body rejecting a transplant of an organ or tissue made using stem cells from the same embryo, he said.