IMPORTANCE OF L-ARGININE FOR HUMAN HAIR ELONGATION
Michelet J.F1, Bernard B.A2, Juchaux F1, Michelin C3, El Rawadi C1, Loussouarn G3, Pereira R1
1
L’Oréal Research & Innovation, Aulnay sous Bois, France - 2 L’Oréal Research & Innovation, Asnières-sur-Seine, France
3
L’Oréal Research & Innovation, Saint-Ouen, France
ABSTRACT
Excessive hair loss may affect up to 60% of men and 40% of women at some point in their life. Topical treatment applied on scalp to fight hair loss and /or to increase hair growth
in dermatology clinics remains mainly minoxidil. Alternatively, hair transplantation is proposed as surgical option. One of the cosmetic approaches to reduce hair loss is to take
into account some aspects of the hair follicle environment, in the goal to improve it and to favor hair growth. In view of this, data from the literature (1) have established that the
concentration of the semi-essential amino acid L-Arginine varied in the human plasma during a 24h period. L-Arginine is well known to be involved in the control of cell proliferation
(polyamines pathway) as well as a precursor of the nitric oxide vascular mediator. For these reasons, we decided to study the impact of various L-Arginine concentrations on in vitro
human hair elongation studies and on the modulation of keys genes in the polyamines pathway. The results demonstrated a clear L-Arginine dose-effect on in vitro hair elongation. A
clinical study showed an anti-hair loss effect of L-Arginine characterized by an increase of anagen (growing) and a decrease of telogen (resting) hair densities. These results confirmed
the interest of an exogenous supplementation of L-Arginine in hair care.
INTRODUCTION
L-Arginine plasma concentration varies during the day and hair shaft contains
8.8 to 9.6% of L-Arginine. Moreover L-Arginine is a precursor of both polyamine
and Nitric oxyde pathways . Considering the high cell proliferative activity of
hair follicle matrix cells on the one hand, and the hair growth dependence
upon vasculature on the other hand, it appeared important to study the role
of L-Arginine in hair follicle physiology and to study how changes in L-Arginine
plasma level could impact human hair elongation.
Figure 1: Effect of diet on average plasma L-arginine
concentration during the day. (From Tangphao et al. 1999)
MATERIALS AND METHODS
For the in vitro study, microdissected hair follicles (volunteer donors with
informed consent) were cultured for 24 hours in Williams’ E medium
w/o L-arginine supplemented with 2 mM L-glutamine, 10 µg/ml insulin,
0.004 µg/ ml hydrocortisone and antibiotics. Hair follicles were then treated
with L-Arginine (tested from 30 µM to 300 µM) for 24 hours (gene expression
analysis), for 3 days (Ki67 expression) or for 12 days (elongation analysis) with
renewal of culture medium and treatment every 48 hours. All the experimental
conditions were performed with 12 follicles each. Effects on hair elongation
were evaluated by measuring the length of each follicle at the beginning of
the assay and every two days. Gene expression analysis was performed by
RT-qPCR after extraction of RNA. Ki67 antigen expression was evaluated by
immunofluorescence on cryosections.
For the in vivo evaluation, one double-blind and randomized clinical study
was conducted on healthy male subjects aged 18-55 with AGA grade III to
V according to Hamilton’s classification. 1.5% L-arginine in hydro-alcoholic
lotion was assessed versus vehicle using the phototrichogram technique (PTG).
33 subjects received the L-arginine lotion (6 ml/day for 1.5 months) and 30
subjects received the placebo (6 ml/day for 1.5 months).
RESULTS
Figure 2: Effects of L-arginine
on hair elongation in vitro.
Microdissected hair follicles
were cultured in customized
Williams’E medium
(w/o arginine) with increasing
concentrations of L-arginine
(0, 0.015, 0.05 and 0.2 g/L).
Effects on hair elongation
were evaluated by measuring
the length of each follicle as a
function of time.
Table 1: Effects of L-arginine on the
expression of selected transcripts in
in vitro human hair follicle.
Microdissected human hair follicles
(volunteer donors, informed consent)
were cultured for 24 hours in Williams’E
medium with increasing concentrations
of L-arginine. Gene expression analysis
was performed by two steps RT-qPCR.
ODC : ornithine decarboxylase 1 (ID: 4953)
ARG2 : arginase 2(ID: 384)
KRT14 : keratin 14 (ID: 3861)
L-arginine deficiency clearly impairs in vitro human hair elongation (fig .2). An
alteration of the hair shaft, reminiscent of anagen-to-catagen transition, with a
dramatic decrease of Ki67 expression by the hair matrix-keratinocytes was also
observed in the absence of L-arginine (Fig.3). At 0.015 g/L, a residual inhibition
of hair growth was still detected. To further characterize the effect of arginine,
a RT-qPCR study was performed on selected genes (Table 1). L-arginine deficiency provoked a clear increase of ODC and ARG2 gene expression while the
expression of KRT14 was clearly decreased. On the opposite, upon Arginine
supplementation, ODC and ARG2 gene expression was repressed, while K14
expression was increased. These modulations were observed on the 18 donors
evaluated (Table 1). The expression of other genes was also assessed but the
modulations observed were donor dependent (Data not showed).
Figure 3: Effects of L-arginine on Ki67
expression in human hair follicle cultured
in vitro. Microdissected hair follicles were
cultured in the presence (0.2 g/L) or absence
of L-Arginine. Ki67 expression was evaluated
by immunohistochemistry on frozen sections
after 1 and 3 days of treatment.
Figure 4: Effects of 1.5% L-arginine
lotion on anagen hair density.
Anagen hairs were counted
using Phototrichogram analysis
before and after 1.5 months of
treatment. *:p<0.05
Figure 5: Effects of 1.5%
L-arginine lotion on modulation
of % of telogen hairs. Telogen
hairs were counted using PTG
before and after 1.5 months of
treatment. *: p<0.05
The in vivo study showed, after 1.5 month of treatment, an increased number of
anagen hair follicles in the L-arginine-treated group (+10 %, Figure 4) compared
to the placebo group (+5 %, Figure 4). In parallel, a decrease of telogen hair
follicles was observed in the L-arginine treated group (-2.2 points, Figure 5).
CONCLUSION
This study highlighted the importance of L-arginine and polyamines pathway for human hair physiology. In the absence of L-arginine, in vitro hair elongation ceased and
the expression of polyamine pathway implicated genes clearly increased. It is well known that, under normal arginine supply, the polyamine pathway is activated at a
basal level. In view of these results, one can hypothesize on the existence of a biological trigger activating the polyamine pathway once hair follicles enter conditions that
deprive growth. In addition, the clinical study showed an anti-hair loss effect of L-Arginine characterized by an increase of anagen hair density (hair in a growth status) and
a decrease of the telogen hair rate (resting status). These results confirmed the interest of an exogenous supplement of arginine in hair care.
REFERENCES
Tangphao, O., et al. "L-arginine and nitric oxide-related compounds in plasma:
comparison of normal and arginine-free diets in a 24-h crossover study." Vasc.Med. 4.1 (1999): 27-32