July 21, 2004

New Findings Reopen Debate About Adult Stem Cell Plasticity

Salk News

New Findings Reopen Debate About Adult Stem Cell Plasticity

La Jolla, CA – Adult stem cells in the brain can change their destiny and become blood vessel cells instead of nerve cells, a Salk Institute study has found.

The study, published in the July 15 issue of Nature, revived the possibility that adult stem cells retain the ability to change their fate and become other cell types. The concept of such stem-cell ‘plasticity’ has been challenged recently by studies showing that stem cells merely fuse with surrounding cells to take on new characteristics.

Fred H. Gage, the Vi and John Adler Chair for Research on Age-Related Neurodegenerative Diseases, and his colleagues incubated mouse neural stem cells with human endothelial cells that form the lining of blood vessels. Within five days, six percent of the stem cells were showing the biochemical and structural characteristics of endothelial cells. The new cells had only one nucleus and contained only mouse chromosomes, indicating that they had, indeed, changed character and not simply fused with the surrounding endothelial cells.

“This indicates that neural stem cells have a broader developmental potential, or plasticity, than was previously believed,” said Gage.

The Salk team confirmed their results in an experimental set-up closer to real life, by transplanting adult neural stem cells into the brains of embryonic mice. Within two days, approximately two percent of the stem cells had started converting to endothelial cells.

The Salk findings also have dramatic implications for angiogenesis, the life-giving repair process by which endothelial cells migrate from the blood vessel wall to forge new networks of blood vessels into oxygen-deprived tissues. Although the prospect is far off, understanding how to harness angiogenesis could prove valuable for producing successful transplanted cells and possibly organs.

“Our work raises the possibility that angiogenesis does not exclusively account for the formation of new endothelial cells in adults, but that stem cells in the brain function along with angiogenesis to create new endothelial cells,” said Andrew Wurmser, a research associate working with Gage. “Equally exciting is the prospect that this model for endothelial cell formation may ultimately be shown to be used by stem cells in other tissues.”

The Salk Institute for Biological Studies, located in La Jolla, Calif., is an independent nonprofit organization dedicated to fundamental discoveries in the life sciences, the improvement of human health and conditions, and the training of future generations of researchers. Jonas Salk, M.D., founded the institute in 1960 with a gift of land from the City of San Diego and the financial support of the March of Dimes Birth Defects Foundation.

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