Penn
study on gut cell regeneration reconciles long-standing research controversy
The lining of the intestine regenerates
itself every few days as compared to say red blood cells that turn over every
four months. The cells that help to absorb food and liquid that humans consume
are constantly being produced. The various cell types that do this come from
stem cells that reside deep in the inner recesses of the accordion-like folds
of the intestines, called villi and crypts.
 |
This is a stem cell (blue) from the
intestinal crypt. Credit: Norifumi
Takeda,
Raj Jain and Jon Epstein,
Perelman School of
Medicine,
University of Pennsylvania.
|
But exactly where the most important
stem cell type is located — and how to identify it — has been something of a
mystery. In fact, two types of intestinal stem cells have been proposed to
exist but the relationship between them has been unclear. One type of stem cell
divides slowly and resides at the sides of intestinal crypts. The other divides
much more quickly and resides at the bottom of the crypts.
Some researchers have been proponents
of one type of stem cell or the other as the "true" intestinal stem cell. Recent work published this
week in Science from the lab of Jonathan
Epstein, MD, chairman of the Department of Cell and Developmental Biology
from the Perelman School of Medicine at
the University of Pennsylvania, may
reconcile this controversy. The findings suggest that these two types of stem
cells are related. In fact, each can produce the other, which surprised the
researchers.
"We
actually began our studies by looking at stem cells in the heart and other
organs," Epstein said.
"In
other tissues in the body, slowly dividing cells can sometimes give rise to
more rapidly dividing stem cells that are called to action when tissue
regeneration is required. Our finding that this can happen in reverse in the
intestine was not expected."
The discovery that rapidly cycling gut
stem cells can regenerate the quiescent stem cells — slowly dividing and probably
long-lived — suggests that the developmental pathways in human organs that
regenerate quickly like in the gut, skin, blood, and bone, may be more flexible
than previously appreciated.
"This
better appreciation and understanding may help us learn how to promote the
regeneration of tissue-specific adult stem cells that could subsequently help
with tissue regeneration," says Epstein.
"It
may also help us to understand the cell types that give rise to cancer in the
colon and stomach."
Contact: Karen Kreeger
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