Why Does Hair Turn Gray? Communications Problem
Between Hair Follicle and Stem Cells
Findings also offer insight into human tissue
14, 2011 Recent research may hold the answer to a question that has
perplexed millions of senior citizens: why does hair turn gray? The new
study has shows that Wnt signaling - already known to control many
biological processes in human development - between hair follicles and
melanocyte stem cells can dictate hair pigmentation.
We have known for decades that hair follicle stem
cells and pigment-producing melanocycte cells collaborate to produce
colored hair, but the underlying reasons were unknown, said
Mayumi Ito, PhD, assistant professor in the Ronald O. Pereleman
Department of Dermatology at NYU Langone Medical Center and leader of
We discovered Wnt signaling is essential for
coordinated actions of these two stem cell lineages and critical for
The Wnt signaling pathway is a network of proteins
best known for their roles in embryogenesis (the process
by which the embryo is formed and develops until it is a fetus)
and cancer, but also involved in normal physiological processes in adult
animals, according to
The study, published in the June 11, 2011 issue of
the journal Cell, suggests the manipulation of Wnt signaling may
be a novel strategy for targeting pigmentation such as graying hair.
The research study also illustrates a model for
The human body has many types of stem cells that
have the potential to regenerate other organs, said Dr. Ito.
The methods behind communication between stem
cells of hair and color during hair replacement may give us important
clues to regenerate complex organs containing many different types of
Using genetic mouse models, researchers were able
to examine how Wnt signaling pathways enabled both hair follicle stem
cells and melanocyte stem cells to work together to generate hair growth
and produce hair color.
Research also showed the depletion (or inhibition,
or abnormal) Wnt signaling in hair follicle stem cells not only inhibits
hair re-growth but also prevents melanocytes stem cell activation
required for producing hair color.
The lack of Wnt activation in melanocyte stem cells
leads to depigmented or gray hair.
The study raises the possibility that Wnt signaling
is a key pathway for the regulation of melanocyte stem cells and shows
how melanocyte behavior is associated with hair regeneration. This
insight provides further understanding of diseases in which melanocytes
are either appropriately lost such as hair graying or undergo
uncontrolled cell growth as in melanoma.