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 Research & Giving News Article  These cells may help people adapt to stress and life changes The pituitary secretes hormones that control many processes throughout the body. Pea-sized in humans, it sits at the base of the brain. It starts developing before birth through the work of stem cells. In embryos, stem cells can divide to spawn nearly any type of cell; however, they show less flexibility in adults. Even so, adult stem cells can give rise to a limited number of cell types, such as red blood cells, white blood cells, and platelets in the case of blood stem cells. Some replace specific cells as they wear out; others help rebuild damaged tissue. Some may even foster cancer. Seeking adult stem cells in the pituitary Dr. Enikolopov, an associate professor at Cold Spring Harbor Laboratory (CSHL), and his colleagues had reason to expect to find adult stem cells in the pituitary of mice. “A few weeks after they are born,” said Dr. Enikolopov, “the pituitary undergoes massive expansion” that suggests the work of adult stem cells. Yet, stem cells are hard to spot among the many cells that form complex tissue. Several years ago, Dr. Enikolopov and his colleagues developed a tool to help locate stem cells that give rise to new adult brain cells. Knowing that a gene called Nestin was active in these neural stem cells, they genetically engineered mice so that the same conditions that activate Nestin in a cell also make it glow green under ultraviolet light—in effect, highlighting cells that might be adult stem cells. Almost 100 research teams around the world have now used these special mice to find adult stem cells in hair follicles, liver, muscle, and other tissues. To search for pituitary stem cells, Anatoli Gleiberman, Ph.D., a researcher in the lab of pituitary expert M. Geoff Rosenfeld at the University of California, San Diego, started a collaboration between that lab and CSHL. In the April 29, 2008 issue of the Proceedings of the National Academy of Sciences, first author Dr. Gleiberman and his collaborators, including Dr. Enikolopov, reported the results. The researchers used the Nestin-tracking mice to identify candidate cells in the anterior pituitary and then used other techniques to show that these are true stem cells. “There are six main lineages in the adult pituitary,” says Dr. Enikolopov, “and we can demonstrate that one adult stem cell can generate all six lineages,” with each cell type secreting a different hormone. A distinct kind of stem cell The researchers found that these adult stem cells in the pituitary differ from the majority of stem cells in adults. “In most cases that we know,” says Dr. Enikolopov, “cells that become stem cells of the adult have been also contributing to embryonic development and continue to serve as stem cells in the adult.” In contrast, the study showed, the adult stem cells in the pituitary played no meaningful role in its formation before birth but started functioning soon afterwards. The scientists suggest that the hormone-producing cells that descend from embryonic and adult stem cells in the pituitary may differ. In addition, they speculate that the resulting “mosaic” of cells gives the gland added flexibility to adapt to changing conditions. They write, “Our results argue that the anterior pituitary exemplifies an unusual strategy for using stem cells to maintain the tissue and respond to incoming signals.” In explaining the importance of these findings for mental health, Dr. Enikolopov notes that hormones strongly influence human neuropsychiatric phenomena, including the stress and depression that comprise his main research focus. “All are mediated through the pituitary,” he said, so changes that happen during the later growth of the gland could have lasting effects. This study complements the work of other NARSAD investigators who have been studying the hypothalamic-pituitary-adrenal axis, a key regulator of the body’s response to stress, emotion, energy use, and other functions. Through these efforts, the relationship of this axis to depression, bipolar disorder, anxiety, and other psychiatric conditions is becoming clearer. This article was adapted by NARSAD with permission of Cold Spring Harbor Laboratory. |
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