Stem cell found that may regenerate blood system

Scientists have for the first time isolated single stem cells that give rise to many different types of blood cell, from the white cells of the immune system and the platelets that help to clot blood, to the red cells that carry oxygen around the body.

The breakthrough holds out the promise that it may be possible one day to use stem cells to regenerate the entire blood system, or to isolate stem cells from individual patients in order to grow their own personal supplies of blood cells or clotting factors.

"We have isolated a single cell that makes all arms of the blood system, which is key to maximising the potential power of stem cells for use in more clinical applications. Stem cells are so rare that this is a little like finding a needle in a haystack," said John Dick of the University Health Network in Toronto, Canada, who led the study.

"Ever since stem cell science began, scientists have been searching for the elusive mother lode, the single, pure stem cell that could be controlled and expanded in culture prior to transplantation into patients," Dr Dick said.

The study, published in the journal Science, was carried out using genetically modified mice that did not have their own immune systems. This allowed the scientists to grow human bone marrow cells within the animals in order to target those that are the stem cells of the blood system.

"Recently scientists have begun to harness the stem cells found in the umbilical cord blood. However, for many patients a single donor sample is not large enough to use. These new findings are a major step to generate sufficient quantities of stem cells to enable greater clinical use and thus move closer to realising the promise of regenerative medicine for patients," Dr Dick said.

Bone marrow transplants are successfully used without knowing what stem cells look like but their identification now opens the way to understanding their genetic programming, he said.