Discovery Of Stem Cells In The Pituitary Gland Of Mice Suggests A
Means Of Adapting To Stress And Life Changes
Article Date: 29 Apr 2008 - 2:00 PDT
A team of researchers led by scientists at Cold Spring Harbor
Laboratory have for the first time identified stem cells that allow
the pituitary glands of mice to grow even after birth. They found
that, in contrast to most adult stem cells, these cells are distinct
from those that fuel the initial growth of this important organ. The
results suggest a novel way that the hormone-secreting gland may
adapt, even in adolescents and adults, to traumatic stress or to
normal life changes like pregnancy.
Seeking Adult Stem Cells
Maturity, in some respects, brings diminished possibilities. As a
fertilized egg cell repeatedly divides to grow into a mature animal,
most of the resulting cells become ever more specialized. But a small
number of cells, known as stem cells, remain uncommitted even as they
spawn more specialized progeny. The most versatile stem cells, taken
from days-old embryos, are able to form any cell type - but studying
them in people is controversial. Even in adults, however, other types
of stem cell persist that have a more limited repertoire. Some
replace specific cells as they wear out; others help to rebuild
damaged tissues. Still other stem cells are suspected by some
scientists of starting or maintaining cancers.
In spite of their importance, stem cells are hard to spot among the
multitude of cells in complex tissue. Several years ago,
neuroscientist Grigori Enikolopov, Ph.D., an associate professor at
Cold Spring Harbor Laboratory (CSHL), and his colleagues developed a
tool to look for stem cells that give rise to new adult brain cells.
Researchers had known that a gene called Nestin was active in these
neural stem cells. The CSHL team genetically engineered mice so that
the same conditions that activate Nestin in a particular cell also
make it glow green under ultraviolet light.
Using these mice gives researchers an important pointer to cells that
may be adult stem cells. Almost 100 research teams around the world
have now used these special mice to help find adult stem cells in
hair follicles, liver, muscle, and other tissues.
Looking at the pituitary
One place where stem cells had been suspected - but never found - is
the pituitary gland. This organ, which in people is about the size of
a pea, sits at the base of the brain, where it secretes hormones that
regulate various processes throughout the body. In mice, the gland
develops in the embryo, but then has a second growth spurt. "A few
weeks after they are born," says Dr. Enikolopov, "the pituitary
undergoes massive expansion" that suggests a role for adult stem
cells.
Anatoli Gleiberman, Ph.D., a researcher in the lab of pituitary
expert M. Geoff Rosenfeld at the University of California, San Diego,
initiated a collaboration between the two labs to look for pituitary
stem cells. The researchers used the Nestin-tracking mice to identify
candidate cells in the anterior pituitary, the section of the organ
that secretes hormones. They 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
These cells differ from most adult stem cells, however. "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." The
research team demonstrated that adult stem cells in the pituitary did
not help construct the embryonic organ.
Their research, the scientists suggest, indicates that the adult
mouse pituitary includes two similar - but not identical - types of
hormone-producing cells: some that grew in the developing embryo, and
some that appeared later. They speculate that having two sets of
cells may let the organ respond differently to changing body
conditions. Dr. Enikolopov notes that hormones strongly influence
human neuropsychiatric phenomena, including stress and depression
that are 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.
"Genetic approaches identify adult pituitary stem cells" appears in
the April 29, 2008 edition of the Proceedings of the National Academy
of Sciences. Along with Dr. Enikolopov, Dr. Michael Geoff Rosenfeld,
who is a Howard Hughes Medical Institute Investigator at the
University of California at San Diego School of Medicine, is a
corresponding author of the paper. The complete citation is as
follows: Anatoli S. Gleiberman, Tatyana Michurina, Juan M. Encinas,
Jose L. Roig, Peter Krasnov, Francesca Balordi, Gord Fishell, Michael
G. Rosenfeld, and Grigori Enikolopov. Click here to access the paper
online.
Cold Spring Harbor Laboratory is a private, nonprofit research and
education institution dedicated to exploring molecular biology and
genetics in order to advance the understanding and ability to
diagnose and treat cancers, neurological diseases and other causes of
human suffering.
For more information, visit http://www.cshl.
Source: Jim Bono
Cold Spring Harbor Laboratory
http://www.medicaln
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StemCells subscribers may also be interested in these sites:
Children's Neurobiological Solutions
http://www.CNSfoundation.org/
Cord Blood Registry
http://www.CordBlood.com/at.cgi?a=150123
The CNS Healing Group
http://groups.yahoo.com/group/CNS_Healing
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