ACTIVATING HAIR GROWTH BY MODIFYING IMMUNE CELLS
How to restore hair
loss is a task not undertaken exclusively by beauty practitioners. The
discovery, now published by a group from the Spanish National Cancer Research
Centre (CNIO), reveals a novel angle to spur hair follicle growth. This also
adds new knowledge to a broader problem: how to regenerate tissues in an adult
organism, especially the skin.
The regenerative
ability of stem cells allows skin replenishment during a lifetime. But
different factors can reduce their regenerative properties or promote their
uncontrolled growth. When things go wrong, this can lead to aging and disease,
including skin carcinomas. The discovery that macrophages activate skin stem
cells may also have further implications beyond the possibility to develop
therapeutic approaches for hair loss, but may also be relevant for cancer
research.
The authors of the
study are Mirna Perez-Moreno and Donatello Castellana, from the Epithelial Cell
Biology Group of the BBVA Foundation-CNIO Cancer Cell Biology Programme, along
with Ralf Paus, a hair immunobiology expert from the University of Manchester
and Münster.
"We have
discovered that macrophages, cells whose main function is traditionally
attributed to fight infections and wound repair, are also involved in the
activation of hair follicle stem cells in non inflamed skin," says
Perez-Moreno.
The researchers did
not investigate the relationship between macrophages and hair for fun. This
work emerged more than four years ago from an observation made by Perez-Moreno
while working on another research project. The mice she had been working with
at that time received anti-inflammatory drugs, a treatment that also
reactivated hair growth. Convinced that the explanation could reside in the
existence of close communication between stem cells and immune cells --the
Perez-Moreno's lab began to experiment with the different types of cells involved
in the body´s defense system.
After years of
investigation, they discovered that when stem cells are dormant, a fraction of
macrophages die, due to a process known as apoptosis. This stimulated the
secretion of factors from dying and living macrophages, which in turn activated
stem cells, and that is when hairs began to grow again.
Reproducing natural
process
Macrophages secrete a
number of factors including a class of proteins called Wnt.
Researchers
demonstrated the participation of macrophage-derived Wnts by artificially
reproducing the natural process by treating macrophages with a Wnt inhibitor
drug encapsulated in liposomes. As expected, when they used this drug, the
activation of hair growth was delayed.
Although this study
has been completed in mice, the researchers believe their discovery "may
facilitate the development of novel treatment strategies" for hair growth
in humans.
The possibility of
attacking one type of cell to affect another might have broader applications
that go beyond "just" growing hair. Furthermore, the use of liposomes
as a way of drug delivery to specific cells, is a very promising line of
experimentation, which may have implications for the study of several
pathologies, says Donatello Castellana.
From a more
fundamental perspective, this research is an effort to understand how modifying
the environment that surrounds adult skin stem cells can regulate their
regenerative capabilities. "One of the current challenges in the stem cell
field is to regulate the activation of endogenous stem cell pools in adult
tissues to promote regeneration without the need of transplantation," says
Perez-Moreno.
Biochemical dialogue
It is now known that
macrophages are key cells involved in the biochemical dialogue that exists in
the environment surrounding stem cells.
"Our study
underlines the importance of macrophages as modulators in skin regenerative
processes, going beyond their primary function as phagocytes [immune system
cells]," say the authors in PLoS Biology.
The researcher´s next
goal is to characterise the class of macrophage(s) that are involved in the
activation of skin stem cells and their implications in the regulation of stem
cells under pathological conditions, including skin carcinomas.
As Perez-Moreno
explains, "macrophages are a very diverse cell population. It was only
less that ten years ago that scientists discovered that besides from the bone
marrow, macrophages originate from the yolk sac during pregnancy, and there are
even other macrophages that proliferate within tissues. The diversity of the
sources from which skin resident macrophages originate is not fully
understood."
Comments
Post a Comment