- Alopecia is a common disease leading to hair loss from the scalp,
face and eyebrows, whose cause remains unknown.
- Current study has identified the role of regulatory T-cells (Tregs)
in promoting hair growth by triggering stem cells in the hair follicles of
T-cells in skin are critical in inducing stem cells within hair follicles to
regenerate and cause hair growth, according to scientists from UC
San Francisco. Without the Tregs,
the stem cells cannot regenerate, consequently resulting in baldness.
"Our hair follicles are constantly
recycling: when a hair falls out, the whole hair follicle has to grow
back," said Michael Rosenblum, MD, PhD, an assistant professor of
dermatology at UCSF and senior author on the new paper. "This has been
thought to be an entirely stem cell-dependent process, but it turns out Tregs
are essential. If you knock out this one immune cell type, hair just doesn't
‘Discovery of the role of immune cells called Tregs in hair growth could lead to newer therapeutic options for hair loss (alopecia) and promotion of hair growth.’
How A Possible Role of Tregs In Hair Growth Was
the course of his earlier research, Rosenblum was interested in delineating the
role of resident Tregs in overall skin health. He and his team developed a technique to remove Tregs from the skin of
mice in order to study them better. To their surprise, they noticed that hair
from these areas never grew back again
prompted Dr Rosenblum and his team to delve deeper into the matter and
investigate whether Tregs could possibly have a role in hair growth
Confirming The Suspicions About The Role of Tregs In
current study was led by post-doctoral fellow Niwa Ali. The significant
observations made by his team in the course of their research included the
- Imaging studies revealed a close association between stem cells in
hair follicles and Tregs.
- At the time of hair follicle regeneration, there was a spurt in the
number of Tregs to almost threefold.
- To further give weight to their theory, they found that removal of
Tregs within 3 days from a patch of shaved skin, blocked hair regrowth.
This is normally the time period when the stem cells are activated to
regenerate hair follicles.
- Removal of Tregs after 3 days, however, from the patch of shaved
skin had no effect on hair regrowth as hair growth had already begun.
- The role of Tregs in promoting hair growth was not in any way
related to their role in regulating skin inflammation. The stem cells were
triggered by a separate pathway
called Notch pathway whose signaling in hair follicle cells was found
to be reduced when Tregs were removed.
- Replacing Tregs in the skin with the Treg signaling protein called Jagged-1 reestablished the Notch
pathway signaling of hair follicle cells and promoted hair growth.
"It's as if the skin stem cells and
Tregs have co-evolved, so that the Tregs not only guard the stem cells against
inflammation but also take part in their regenerative work," Rosenblum
said. "Now the stem cells rely on the Tregs completely to know when it's
time to start regenerating."
Role of Tregs In Inflammation
Tregs are immune regulatory T cells that
are predominantly found in lymph nodes. They help the immune system to
distinguish between self proteins that should be left alone and not attacked, and
harmful foreign antigens which have to be dealt with summarily by the immune
If Tregs are defective, it results in
autoimmune disease due to attack of self antigens and allergies to harmless
agents like peanut protein
and animal dander.
Some Tregs which reside in host tissues
other than lymph nodes,
for instance the skin, help develop tolerance to healthy skin bacteria in mice
and also secrete substances that help in wound healing up to adulthood.
of Tregs Role In Promoting Hair Growth
hair loss is a common occurrence and is associated with patches of hair loss
from scalp, eyebrows and face.
Further studies by Dr Rosenblum have
established that genes shown to be associated with hair loss were mostly
related to Tregs. Treatment aimed at improving Treg function could help in
Rosenblum plans to further study the role
of skin Tregs in wound healing as the same hair follicle stem cells are
stimulated to regenerate following skin injury.
"We think of immune cells as coming
into a tissue to fight infection, while stem cells are there to regenerate the
tissue after it's damaged," he said. "But what we found here is that
stem cells and immune cells have to work together to make regeneration possible.
In conclusion, further research to gain a
better understanding on the role of Tregs in hair growth could generate newer therapeutic options in the promotion of hair growth.
- Niwa Ali, Bahar Zirak, Robert Sanchez Rodriguez, Mariela L. Pauli, Hong-An Truong, Kevin Lai, Richard Ahn, Kaitlin Corbin, Margaret M. Lowe, Tiffany C. Scharschmidt, Keyon Taravati, Madeleine R. Tan, Roberto R. Ricardo-Gonzalez, Audrey Nosbaum, Marta Bertolini, Wilson Liao, Frank O. Nestle, Ralf Paus, George Cotsarelis, Abul K. Abbas, Michael D. Rosenblum. "Regulatory T Cells in Skin Facilitate Epithelial Stem Cell Differentiation." Cell (2017). DOI: http://dx.doi.org/10.1016/j.cell.2017.05.002