Mammals can regenerate
20 May 2007
Mammals have the power to switch on dormant genes capable
of regenerating cells, according to new research reported in Nature.
Researchers at the University of Pennsylvania School of Medicine have
found that hair follicles in adult mice regenerate by re-awakening genes
once active only in developing embryos. These findings provide unequivocal
evidence for the first time that, like other animals such as newts and
salamanders, mammals have the power to regenerate.
Researchers previously believed that adult mammal skin could not
regenerate hair follicles. In fact, investigators generally believe that
mammals had essentially no true regenerative qualities. (The liver can
regenerate large portions, but it is not de novo regeneration; some of the
original liver has to remain so that it can regenerate.)
A better understanding of the process involved in the regeneration could
lead to novel treatments for hair loss, other skin and hair disorders, and
“We showed that wound healing triggered an embryonic state in the skin
which made it receptive to receiving instructions from wnt proteins,” says
senior author George Cotsarelis, MD, Associate Professor of Dermatology.
“The wnts are a network of proteins implicated in hair-follicle
In this study, researchers found that wound healing in a mouse model
created an “embryonic window” of opportunity. Dormant embryonic molecular
pathways were awakened, sending stem cells to the area of injury.
Unexpectedly, the regenerated hair follicles originated from
non-hair-follicle stem cells.
“We’ve found that we can influence wound healing with wnts or other
proteins that allow the skin to heal in a way that has less scarring and
includes all the normal structures of the skin, such as hair follicles and
oil glands, rather than just a scar,” explains Cotsarelis.
By introducing more wnt proteins to the wound, the researchers found that
they could take advantage of the embryonic genes to promote hair-follicle
growth, thus making skin regenerate instead of just repair. Conversely by
blocking wnt proteins, they also found that they could stop the production
of hair follicles in healed skin.
Increased wnt signaling doubled the number of new hair follicles. This
suggests that the embryonic window created by the wound-healing process can
be used to manipulate hair-follicle regeneration, leading to novel ways to
treat hair loss and hair overgrowth.
These findings go beyond just a possible treatment for male-pattern
baldness. If researchers can effectively control hair growth, then they
could potentially find cures for people with hair and scalp disorders, such
as scarring alopecia where the skin scars, and hair overgrowth.
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