From the Boston Globe:

Biologists announced yesterday a way to dramatically expand populations of blood stem cells, a discovery that could improve bone marrow transplants and make them available to more patients.
Bone marrow transplants save the lives of thousands of Americans every year, mainly cancer patients, but many others are denied treatment because the cells that give the transplants their regenerative power — blood stem cells — are quite rare, and doctors have no way of substantially increasing their number before giving a transplant to a patient.
The new technique, discovered in mouse experiments by biologists at the Whitehead Institute for Biomedical Research in Cambridge, uses a cocktail of growth factors to multiply the stem cells up to thirtyfold. If the discovery can be adapted to humans, scientists said, it would transform the field — saving patients who can’t be helped today, in part because of a shortage of bone marrow donors.
”This is a very significant step forward,” said Dr. Guy Sauvageau, who was not involved in the Whitehead work and is scientific director of the Institute for Research in Immunology and Cancer in Montreal.