PA) - Hair follicle stem cells are important contributors to the
wound-healing process, according to new research by investigators
at the University of Pennsylvania School of Medicine.
Using an animal model, the researchers discovered that stem cells
in the hair follicle are enlisted to help heal wounds in the skin.
This finding, published online in Nature Medicine last
week, may suggest a therapeutic target for the development of drugs
to encourage and promote wound healing.
Wounds, including skin ulcers and other dermatological problems
associated with diabetes, circulatory problems, and other diseases,
are a growing medical problem in the United States, notes senior
author George Cotsarelis, MD, Associate Professor
of Dermatology. Previous work by the Penn research team had outlined
the hair-growth process to show that stem cells in the hair follicle
"bulge" area generate new lower hair follicles, which
in turn, generate new hair. Their latest finding-that these same
stem cells play a key role in initiating wound healing-will help
lay the foundation for designing more effective wound-healing strategies.
Even minor wounding resulted in mobilization of follicle stem cells
to generate daughter cells that quickly move into the wound area.
“About one-third of the coverage of the wound came from the
stem cells in the hair follicle,” says Cotsarelis. “In
the future, we think that we will be able to design treatments that
enhance the flow of cells from the hair follicle to the epidermis
in the hope of enhancing wound healing and treating patients with
Follow the Blue Light
Clinicians have known for some time that when the skin is abraded
new cells come from the hair follicle. What remained a mystery was
the exact nature of the origins of the new cells-specifically, what
percentage stems from the deep follicle and what percentage from
the epidermis near the wound.
Cotsarelis’ team found that adult stem cells from the lowest
portion of the hair follicle, or “bulge,” quickly ascend
the follicle in response to wounding and ultimately comprise about
30 percent of the new cells in a wound when it first starts to heal.
In addition, the stem cells respond rapidly to surface wounding-within
two days-by generating short-lived “transient-amplifying”
cells that respond to acute wound-healing needs.
Using a genetically engineered mouse designed in their lab, the
researchers were able to visually follow the fate of the stem cells
as they migrated from deep within the skin to the surface wound
site. The mouse stem cells express a reporter gene that encodes
an enzyme, which can be detected with a special blue-color reaction.
“We could see blue lines coming from the follicles going toward
the center of the wound,” says Cotsarelis. “They formed
a striking radial pattern like the spokes of a wheel.”
Hope for Hair Loss?
The research also showed that stem cells might be a therapeutic
target in certain types of hair loss. Using a different engineered
mouse also designed in the Cotsarelis lab, one in which the hair-follicle
stem cells could be destroyed after administration of a drug, the
researchers discovered that the animals permanently lost all of
their hair. This hair loss mimics types of hair loss seen in humans
called scarring alopecias. But, cautions Cotsarelis, more studies
are needed to determine if the loss of hair-follicle stem cells
plays a role in hair loss in humans.
This research was funded in part by the National Institutes of Health.
Other co-authors in addition to Cotsarelis are Mayumi Ito, Yaping
Liu, Zaixin Yang, Jennifer Nguyen, and Fan Liang, all from Penn,
as well as Rebecca J. Morris from the Columbia University College
of Physicians and Surgeons, New York.
PENN Medicine is a $2.7 billion enterprise
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