receptor signaling and capsaicin inhibitory effects
Contained in the human hair follicle is something known as the
Vanillioid receptor-1 or "TRPV". Scientists have recently
discovered that this Vanillioid receptor-1 is very significant
for hair growth. The receptor
can be signaled by certain processes so as to inspire new hair growth where
there was previously very little. Alternatively, the signaling of this receptor
can be inhibited by other agents, one of which is known as Capsaicin. Capsaicin
is a chemical that is found in hot peppers can be used to de-activate the
Vanilloid receptor and thereby regulate the growth of hair. Other proteins
and genetic building blocks such as TGF-b2 have also been tested to see
the affects on the Vanillioid receptor. So far, however, Capsaicin has proven
to have the most potent effect.
The Vanillioid receptor-1 or "TRPV" as it is sometimes
referred, can be activated in certain cells of the skin such as
mast cells, glial cells, bronchial epithelial cells, uroepithelial
cells and keratinocytes. When the TRPV expressing cells are activated
in hair follicles, there is often a change in the cell proliferation
of hair follicles. Scientists have experimented with these findings
in order to discover not just the basic proliferation changes
but the effects on hair elongation, pigmentation and growth cycle
patterns of hair follicles.
A study was done in which hair follicles were first taken from
a number of female patients who were undergoing facelift surgery.
The hair follicles were individually measured at the start of
the experiment so as to test for any changes that would come about
later in the experiment. Some hair follicles were also examined
to determine the presenceo f distribution of different proteins
and cell receptors. The follicles were prepared under 24 different
plates, treated with the various agents and often colored with
certain pigments to determine various results.
Early in the experiment, scientists measured the protein and
calcium changes in the hair follicles after they were combined
with certain agents. Some proteins and calcium changes were discovered
and documented in relation to their affect on hair growth. Scientists
also measured other changes such as the proliferation change which
came about in the presence of TRPV. This proliferation change
was measured through a process known as flow cytometry.
On the human scalp, it was discovered that specific localized
expression of TRPV existed in two important areas of the hair
follicle. The most prominent area was found to be the outer root
sheath or ORS and the less prominent area was the hair matrix.
With these initial findings, scientists were able to focus their
observations on other agents and the more specific effects that
they had on TRPV and hair growth.
It was later discovered that the signaling of TRPV by certain
proteins and chemical agents had a profound effect on the production
of keratinocyte proliferation. With an increase in keratinocyte
proliferation, there was a significant increase in hair growth
and a change in growth characteristics. Once these initial discoveries
were made, an alternate approach was ready for testing.
Capsaicin was added to the areas where TRPV had been originally
expressed but, instead of getting positive changes as had first
been the case, there was a reverse in the process of TRPV signaling.
The Capsaicin inhibited the elongation of the hair follicles by
slowing down the activity of the TRPV and keratinocyte proliferation
in the follicles. The pigmentation was also depleted in the hair
follicles when Capsaicin was applied.
Capsaicin was observed in relation to many features but only
one feature remained unchanged by its effects. The in situ differentiation
of the hair follicles was not affected by the Capsaicin. This
differentiation was the only quality of the hair follicles that
remained unaffected. Although scientists had discovered that Capsaicin
could produce inhibitory effects on the TRPV in terms of the proliferation
of hair follicles, the elongation and the pigmentation of the
hair follicles, it had not affected the differentiation characteristics
TGF-b2, was also experimented with in combination with the Capsaicin
to see the resultant effect on the TRPV signaling. Scientists
wanted to know if TGF-b2 would also have an inhibitory affect
on hair growth and help along the work of the Capsaicin. In fact,
the TGF-b2 showed a tendency to partially negate the effects of
the Capsaicin. The hair growth was no longer inhibited as it had
been by using the Capsaicin agent alone. Other experiments like
this one have become an ongoing focus for scientists.
Other proteins and organic agents have been tested to determine
the effects that different genes may have in TRPV signaling. Some
of these agents include activin BA and matrix GLA-protein precursor.
These studies into the effects of genetic manipulation in hair
follicles promise new discoveries for patients who wish to remove
unwanted hair and to inspire new growth in areas where there has
been unwanted hair loss.
receptor signaling and capsaicin inhibitory effects references
- Bodo E, Biro T, Telek A, Czifra G, Griger Z,
Toth BI, Mescalchin A, Ito T, Bettermann A, Kovacs L, Paus R.
A hot new twist to hair biology: involvement of vanilloid receptor-1
(VR1/TRPV1) signaling in human hair growth control. Am J Pathol.
2005 Apr;166(4):985-98. PMID: 15793280