Withholding amino acid depletes blood stem cells

Withholding amino acid depletes blood stem cells

The researchers showed that a diet deficient in the essential amino acid valine could effectively deplete the population of blood stem cells in mice and allow them to be successfully transplanted with blood stem cells from other mice. The researchers also showed that human blood stem cells in the laboratory were affected by a lack of access to valine, suggesting that the same therapeutic approach may work in humans.

A paper describing the findings is published in Science.

The effect of a valine-deficient diet is fairly specific to blood stem cells, but there seem to be other sorts of stem cells that may also be affected, author said, including hair stem cells and some T cells. Although other types of stem cells may also be affected, the effects are not nearly as widespread or extreme as those caused by chemotherapy or radiation therapy, author said.

The new study came about when the senior author was reviewing the scientific literature and found an article in a 1946 issue of Science. It was co-authored by the late Stanford researcher Arthur Kornberg, who would go on to receive the 1959 Nobel Prize in Physiology or Medicine. In his 1946 research, Kornberg and his colleagues showed that certain types of anemia in rats could be treated by giving them mixtures of purified amino acids.

The researchers found that in a lab dish, a lack of valine or another amino acid, cysteine, would make the growth of mouse blood stem cells impossible. Then, the researchers asked a company to create mouse food that was deficient in only these specific amino acids, and fed the mice this diet for four weeks.

They found that the valine-deficient diet, but not the cysteine-deficient diet, depleted blood stem cells in the mice. "Unlike valine, cysteine is not an essential amino acid, which means that the body can make some of it itself," author said. "All of our valine has to come from our diet, however."

The current dietary method complements other work recently reported by Stanford scientists for using antibodies instead of chemotherapy or radiotherapy to clear out blood stem cells in preparation for bone marrow transplantation. "The two methods might even be used together to provide an even more effective, gentler therapy," author said.

The mechanism by which amino acid deficiency affects blood stem cells is unknown, author said, but that will be the focus of future research. Now that this amino acid has shown promise as the basis for a dietary therapy, scientists may find other specific kinds of stem cells that are affected by the presence or absence of particular amino acids.