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VEGF upregulates VEGF receptor-2 on human outer root sheathcells and stimulates proliferation through ERK pathway
Wei Li • Zhong-Fa Lu • Xiao-Yong Man • Chun-Ming Li •
Jiong Zhou • Jia-Qi Chen • Xiao-Hong Yang •
Xian-Jie Wu • Sui-Qing Cai • Min Zheng
Received: 29 January 2012 / Accepted: 6 June 2012 / Published online: 16 June 2012
� Springer Science+Business Media B.V. 2012
Abstract Vascular endothelial growth factor (VEGF) is a
key regulator of physiological and pathological angiogen-
esis. The biological effects of VEGF are mediated by
receptor tyrosine kinases. VEGF receptor-2, the primary
receptor for VEGF, is thought to mediate most functional
effects. In this study, we examined the expression and roles
of VEGF receptor-2 on human outer root sheath cells
(ORS). The expression of VEGFR-2 was determined at
mRNA and protein levels by reverse transcription-poly-
merase chain reaction (RT-PCR) and Western blot.
Localization of VEGFR-2 in ORS cells was detected by
immunofluorescence. The effect of VEGF on ORS cell
proliferation was determined by MTT assays. Our data
showed the expression of VEGFR-2 on ORS cells at both
mRNA and protein levels. Immunostaining for VEGFR-2
demonstrated strong signal on cultured ORS cells. Exoge-
nous VEGF165 stimulated proliferation of ORS cells and
upregulated expression of VEGFR-2 in a dose-dependent
manner. Moreover, VEGF165 induced phosphorylation of
VEGFR-2, PLC-c1, PKC-a, MEK, and p44/42 MAPK
(ERK1/2) in a time-dependent manner. Taken together,
human ORS cells express functional VEGF receptor-2 and
exogenous VEGF165 upregulates expression of VEGFR-2
and stimulates proliferation of ORS cells via VEGFR-2
mediated ERK signaling pathway.
Keywords VEGF � VEGFR � Outer root sheath �Proliferation � ERK � Hair follicle
Abbreviations
VEGF Vascular endothelial growth factor
VEGFR Vascular endothelial growth factor receptor
ORS Outer root sheath
DPC Dermal papillae cells
MAPK Mitogen-activated protein kinase
ERK Extracellular signal regulated kinase
JNK C-Jun N-terminal protein kinase
PI3K Phosphatidylinositol-3-kinase
PLC-c Phospholipase C-cPKC-a Protein kinase C-aDKSFM Defined keratinocyte serum-free medium
Introduction
Hair follicle, the only organ that undergoes cyclic trans-
formations for entire life in the mammalian body, consists
of epidermal layers as well as dermal compartments
including dermal papilla [1]. Epidermal layers are grouped
into outer root sheath (ORS), inner root sheath (IRS) and
hair shaft. The ORS cells are morphologically similar to
Electronic supplementary material The online version of thisarticle (doi:10.1007/s11033-012-1725-6) contains supplementarymaterial, which is available to authorized users.
W. Li � Z.-F. Lu � X.-Y. Man � J. Zhou � J.-Q. Chen �X.-J. Wu � S.-Q. Cai � M. Zheng (&)
Department of Dermatology, Second Affiliated Hospital,
Zhejiang University School of Medicine, 88 Jiefang Road,
Hangzhou 310009, Zhejiang, China
e-mail: minz@zju.edu.cn
C.-M. Li
Department of Dermatology, Second Affiliated Hospital,
Nanchang University School of Medicine,
Nanchang 330000, China
X.-H. Yang
Department of Dermatology, Zhejiang Provincial Hospital
of Traditional Chinese Medicine, Hangzhou 310009, China
123
Mol Biol Rep (2012) 39:8687–8694
DOI 10.1007/s11033-012-1725-6
the basal keratinocytes of the interfollicular epidermis and
play an important role during hair cycle, hair growth and
healing of skin wounds [2–4].
Vascular endothelial growth factor (VEGF, commonly
referred to VEGF-A), which belongs to a family of growth
factors, including VEGF-B, VEGF-C, VEGF-D and pla-
cental growth factor (PLGF) in mammals, is a key regu-
lator of vessel formation during embryonic development,
wound healing and maintaining vessel homeostasis in adult
organisms [5, 6]. The biological effects of VEGF are
mainly mediated through receptor tyrosine kinases (RTK),
known as VEGF receptor-1, -2 and -3 (VEGFR1-3). The
predominant receptor for VEGF, VEGFR-2, is thought to
mediate most functional effects such as cell proliferation,
migration and survival [6–9].
We previously demonstrated that VEGF and VEGFR-2
are not only expressed in normal human epidermis, but also
regulate the functions of epidermal keratinocytes such as
enhancing proliferation and migration of keratinocytes,
decreasing the adhesion ability of keratinocytes [10–12].
Kozlowska et al. [13] had displayed expression of VEGF in
various compartments of the human hair follicle a decade
ago. However, little is known as to whether VEGFR-2 is
expressed by hair follicle and its potential roles up to now.
Recently we have shown that VEGF and VEGFR-2 are
both expressed in human anagen hair follicles including
outer root sheath and dermal papillae by immunofluores-
cence [14]. In the work presented here, we give further
evidence for the expression of functional VEGFR-2 in
human outer root sheath cells. Moreover, we show here
that VEGF up-regulated expression of VEGFR-2 and
stimulated proliferation of ORS cells through VEGFR-2
mediated extracellular signal regulated kinase (ERK) sig-
naling pathway.
Materials and methods
Chemicals and reagents
Dispase, trypsin, defined keratinocyte serum-free medium
(KSFM) supplemented with keratinocyte growth factor
(KGF), fetal bovine serum (FBS), and Trizol were obtained
from Gibco and Invitrogen (Invitrogen, Auckland, USA).
Monoclonal mouse anti-human VEGFR-2 antibodies were
purchased from R&D Systems (MAB3571, Minneapolis,
MN, USA) and Santa Cruz Biotechnology (SC-6251, Santa
Cruz, CA, USA). Rabbit anti-human phospho-VEGFR-2
(Tyr1175), phospho-PLC-c1 (Tyr783), PLC-c1, phospho-
PKC-a (Thr638/641), PKC-a, phospho-MEK (Ser217/221),
MEK, p44/42 MAP kinase antibodies and mouse anti-
human phospho-p44/42 MAPK (Thr202/Tyr204) antibody
were obtained from Cell Signaling Technology (Beverly,
MA, USA). Mouse anti-human GAPDH was from Kang-
Chen Bio-tech (Shanghai, China). Horseradish peroxidase–
linked anti-mouse IgG was from Jackson ImmunoResearch
Laboratories (West Grove, PA, USA). Polyclonal rabbit
anti-mouse immunoglobulins/FITC was from DakoCyto-
mation (Denmark). VEGF165 from Chemicon International
Inc. (Temecula, CA, USA); Moloney murine leukemia
virus (MMLV) reverse transcriptase and RNase inhibitor
from Fermentas (Amherst, NY, USA); cocktail protease
inhibitors from Roche Diagnostics (Indianapolis, IN,
USA); propidium iodide (PI) and mouse IgG from serum
from Sigma-Aldrich (St. Louis, MO, USA). Primers were
synthesized by Sangon (Shanghai, China), and purified
PCR products were directly sequenced by Genscript
(Nanjing, China).
Isolation and culture of ORS cells from human scalp
specimens
This study conformed to the principles outlined in the
Declaration of Helsinki and was approved by Zhejiang
University Institutional Review Board. Normal human
scalp specimens (n = 16, including 9 females and 7 males,
aged 18–50) were obtained as excess tissues from subjects
with informed consent, who were undergoing cosmetic
surgery without systemic disease. The specimen was cut
into small pieces and put into 0.5 % dispase for overnight
incubation at 4 �C. Hair follicles were extruded from the
specimen and then further incubated in 0.25 % trypsin with
0.03 % EDTA at 37 �C for 30 min. Trypsin activity was
neutralized by adding fetal bovine serum (FBS). To obtain
ORS cell suspension, the isolated cells were filtrated
through nylon gauze (200 lm mesh) and ORS cells were
washed twice at 500 g for 5 min prior to resuspension in
complete defined keratinocyte serum-free medium
(DKSFM). ORS cells were plated into 25 cm2 culture flask
(Corning, NY, USA), maintained at 37 �C in a humidified
atmosphere containing 5 % CO2. Passages 2 to 4 were used
in all experiments. HUVECs, expressing VEGFR-2 and
serving as a positive control, were obtained from isolated
umbilical veins by a standard method [10].
Indirect immunocytochemistry assay
Indirect immunocytochemistry assays were performed as
described previously [10, 11]. Briefly, cells were seeded on
coverslips in 24-well culture plates. When cells were
60–70 % confluence, the coverslips were then fixed with
4 % paraformaldehyde buffer for 20 min at room temper-
ature. After incubation in sodium citrate buffer (10 mM,
pH 8.5) at 95 �C for 20 min, the coverslips were perme-
abilized at room temperature for 15 min with phosphate
buffered saline (PBS) containing 0.1 % Triton-100, and
8688 Mol Biol Rep (2012) 39:8687–8694
123
incubated with 10 % normal rabbit serum for 1 h at room
temperature to prevent nonspecific binding. Fixed cover-
slips were then incubated with antibodies against VEGFR-
2 (mouse anti-human, sc-6251; Santa Cruz Biotechnology,
CA, USA) overnight at 4 �C, followed by fluorescein iso-
thiocyanate-conjugated rabbit anti-mouse secondary anti-
body (Aako Cytomation; Dako, Glostrup, Denmark)
diluted 1:40 with 10 % rabbit serum in PBS incubated for
2 h at room temperature in the dark. Coverslips were
counterstained with propidium iodide mounting medium
(Sigma-Aldrich, St Louis, MO, USA) to visualize the
nuclei and analyzed by fluorescence microscopy (Olympus,
Tokyo, Japan). For each case, a negative control incubated
with nonimmune mouse IgG (Sigma-Aldrich, St Louis,
MO, USA) was included.
Reverse transcription and polymerase chain reaction
(RT-PCR)
Total RNA was extracted from VEGF treated or untreated
ORS cells using Trizol, according to the manufacturer’s
instructions. Total RNA was reverse-transcribed into first
strand cDNA in a total reaction volume of 20 ll, as
described previously [10]. The following parameters were
used for PCR: 95 �C for 5 min, followed by 36 cycles of
95 �C for 1 min, 60 �C (for VEGFR-2) or 55 �C (for CD31
and GAPDH) for 45 s, and 72 �C for 45 s, and ending with
a full extension cycle of 72 �C for 10 min. In each
experiment, negative control (using total RNA as the
template) was included and GAPDH served as an internal
control. Sequence identity of PCR product was confirmed
by direct sequencing. Primers were designed based on
published cDNA sequences as follows:
VEGFR-2 (NM_002253).
50-GACGGACAGTGGTATGGTT-30 (forward).
50-CCGAGTCAGGCTGGAGAAT-30 (reverse).
CD31 (BC051822).
50-CTTCGCGGATGTCAGCACCAC-30 (forward).
50-CCTCAACGGGGAATTCCAGTATCA-30 (reverse).
GAPDH (NM_002046).
50-TGAAGGTCGGAGTCAACGG-30 (forward).
50-TGGAAGATGGTGATGGGAT-30 (reverse).
Western blot analysis
Western blot were carried out as previously described [10,
11]. Briefly, ORS cells grown to 80–90 % confluence were
washed twice in ice-cold PBS, scraped, and centrifuged.
The pellet was incubated for 30 min in modified RIPA
lysis buffer then centrifuged. Protein concentrations were
measured using the QuantiPro BCA assay kit (Sigma-
Aldrich). Total cellular protein was separated by sodium
dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-
PAGE) and then transferred to PVDF membrane (Hybond-
P, Amersham). Blots were blocked for 60 min at room
temperature in PBS containing 1 % Tween-20. After rins-
ing 3 times for 10 min with PBS containing 0.05 %
Tween-20, the membrane was probed with the respective
primary antibody overnight at 4 �C in PBS containing 1 %
Tween-20. Blots were then washed 4 times (5 min each) in
PBS containing 0.05 % Tween-20 and incubated for 2 h
with horseradish peroxidase–conjugated goat polyclonal
anti-mouse IgG antibody (1:5000; Jackson). The mem-
brane was washed 5 times (5 min each) with 0.05 %
Tween-20-PBS, and the immunoreactive bands were
detected using enhanced chemiluminescent (ECL) plus
reagent kit before exposure for at least 3 min to Kodak film
(Kodak, Rochester, NJ, USA). Mouse monoclonal anti-
GAPDH (diluted 1:5000) was used as a loading control.
HUVECs were used as a positive control in all panels.
Effect of VEGF165 on ORS cell proliferation
Normal human ORS cells were plated in 96-well plates at
5,000 cells/well in defined KSFM and cultured for 24 h.
Cells were then treated with various concentrations of
VEGF165 at 0, 1, 10, 50, and 100 ng/ml in basal defined
KSFM and incubated for 48 h. At the end of the incuba-
tion, freshly prepared and filtered dimethylthiazol-diphe-
nyltetrazolium bromide (MTT) (Sigma, St Louis, MO,
USA) was added and the mixture was further incubated for
4 h. After the medium was removed, cells in each well
were dissolved with 100 ll DMSO, and optical density was
read at 570 nm with a 96-well plate ELISA reader (Bio-
Rad Instruments, CA, USA).
Statistical analysis
Results are expressed as mean ± SD. All determinations
were performed in triplicate and experiments were repeated
at least 3 times. One-way ANOVA was used to evaluate
significant differences. Statistical analysis were performed
by SPSS Software (V13.0, SPSS, USA), with a
P value \ 0.05 considered to be statistically significant.
Results
Human ORS cells expressed VEGFR-2 mRNA
and protein
The expression of VEGFR-2 mRNA was detected in cul-
tured human ORS cells from all three normal donors
(Fig. 1a). Direct sequencing for PCR product was identical
Mol Biol Rep (2012) 39:8687–8694 8689
123
to published sequences of human VEGFR-2 (NM_002253).
The expression of CD31 gene was detected in HUVECs but
not in any sample of cultured ORS cells, suggesting no
contamination of endothelial cells in cultured ORS cells
(Fig. 1a).
VEGFR-2 protein was determined by Western blot. The
bands of VEGFR-2 were at about 180 and 200 kDa (indi-
cating the glycosylation or phosphorylation of VEGFR-2,
Fig. 1b). Immunostaining for VEGFR-2 showed that strong
positive signal was distributed on the membrane and in the
cytoplasm of cultured ORS cells (Fig. 1c).
VEGF165 stimulated proliferation of cultured ORS cells
in a dose-dependent manner
VEGF165 at the concentration of 50 ng/ml significantly
increased proliferation of cultured ORS cells compared to
the untreated control (p \ 0.05) (Fig. 2). Doses lower than
50 ng/ml of VEGF tended to stimulate proliferation of
ORS cells without statistical significance.
VEGF165 upregulated the expression of VEGFR-2
on cultured ORS cells in a dose-dependent manner
To investigate whether VEGF affects the expression of
VEGFR-2, ORS cells were incubated with various
concentrations of VEGF165 at 0, 1, 10, 50 and 100 ng/ml in
basal defined KSFM for 24 h. We found that VEGF165
significantly upregulated expression of VEGFR-2 mRNA
and protein in dose-dependent manners (Fig. 3a, b).
Fig. 1 Expression of VEGFR-2 in cultured human ORS cells. a RT-
PCR analysis of VEGFR-2 and CD31 gene in HUVECs and cultured
ORS cells from 3 different healthy samples. NEG is a negative control
showing no amplification from potential genomic DNA contamina-
tion. GAPDH served as an internal control for different amplification
performed for respective genes. b Immunoblot analysis of VEGFR-2
in protein extracted from 3 different cultured ORS cells. The anti-
VEGFR-2 showed bands at about 180 and 200 kDa. GAPDH served
as a loading control for protein normalization. c Immunofluorescence
staining for VEGFR-2. Strong immunostaining signal for VEGFR-2
(green color) was observed on cultured ORS cells. d Staining with
non-immune mouse IgG as a negative control. The cellular nuclei
were stained with PI (red color). Scale bar: 50 lm. (Color figure
online)
Fig. 2 Effect of VEGF165 on cultured ORS cell proliferation. MTT-
based assays were performed to determine the effects of VEGF165 for
48 h treatment. VEGF165 stimulated proliferation of cultured ORS
cells in a dose-dependent manner. Data represent the mean values of
optical density measured in 5 wells for each treatment. The
experiment was repeated at least 3 times with similar results.
(*p \ 0.05: compared to untreated control)
8690 Mol Biol Rep (2012) 39:8687–8694
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VEGF165 induced phosphorylation of VEGFR-2,
PLC-c1, PKC-a, MEK, and p44/42 MAPK (ERK1/2)
in cultured ORS cells
50 ng/ml of VEGF165 phosphorylated VEGFR-2, which
has intrinsic kinase activity. Phosphorylation of VEGFR-2
reached peak level at 15 min and regressed to the basal
level at 120 min (Fig. 4a). Phosphorylation of PLC-c1 was
elevated by VEGF165 treatment and reached the maximum
level at 15 min, sustained at 30 min, then gradually went
back to the basal level (Fig. 4b). Phosphorylation of PKC-awas found at 5 min and peaked at 15 min, then regressed to
the baseline (Fig. 4c). The phosphorylation of MEK also
reached maximal level at 15 min and maintained at
30 min, then returned to the basal level (Fig. 4d).
Enhanced ERK1/2 phosphorylation by VEGF165 was found
at 5 min and peaked at 15 min, and the activation ceased
after 60 min (Fig. 4e).
Discussion
Hair follicle is known for its cyclic transformations from
stages of rapid growth (anagen) to relative quiescence
(telogen), then to apoptosis-driven regression (catagen) and
back to anagen again [1, 3]. Accompanied with stages of
hair cycle is perifollicular vascularization, which promotes
hair growth and increases hair follicle and hair size [1, 15].
Yano and colleagues [15] reported that perifollicular
angiogenesis is temporally and spatially correlated with
upregulation of VEGF expression by ORS cells, but the
mechanism of VEGF enhancing hair growth is still
obscure. During hair cycle, both epidermal and dermal
layers undergo cyclic and dramatic changes in prolifera-
tion, differentiation and apoptosis. Central to the hair fol-
licle growth are epithelial–mesenchymal interactions,
which involve many molecular mediators such as fibroblast
growth factor (FGF), transforming growth factor (TGF)-b,
and vascular endothelial growth factor (VEGF) etc. [1–3,
16, 17], but how the dermal papillae cells (DPCs) exert
their power over epithelial layers such as ORS cells
remains unclear.
VEGF receptors were initially thought to be expressed
exclusively in endothelial cells [6, 8, 9], but recently,
growing studies have found expression of VEGF receptors
in other cell types and tissues [10, 11, 18–20]. VEGFR-2,
the primary receptor of VEGF, is implicated in all aspects
of normal and pathological vascularization and regulates
endothelial cell proliferation, migration, differentiation and
survival as well as vessel permeability and dilation [6, 8,
21]. Our previous work has demonstrated that VEGF
receptors are expressed in normal human epidermal
keratinocytes, and through activating VEGFR-2, VEGF
stimulates proliferation and migration of epidermal
Fig. 3 Effect of VEGF165 on mRNA and protein levels of VEGFR-2
in cultured ORS cells. ORS cells were cultured to 80–90 % confluent
in growth medium, then switched to basal defined KSFM with various
concentrations of VEGF165 (0, 1, 10, 50, and 100 ng/ml) for 24 h
before harvest. a RT-PCR analysis of VEGFR-2 mRNA expression in
cultured ORS cells in response to different concentrations of
VEGF165; GAPDH served as an internal control. The columnar
section was relative quantitative analysis of VEGFR-2 at mRNA
levels, which was shown after normalization to the endogenous
control GAPDH. b Western blot analysis of VEGFR-2 in cultured
ORS cells exposed to VEGF165; GAPDH served as a loading control
for protein normalization. The columnar section was relative quan-
titation of VEGFR-2 protein levels, which were shown after
normalization to the endogenous control GAPDH. Bars represented
mean ± SD in triplicate (*p \ 0.05; **p \ 0.01: compared to
untreated controls)
Mol Biol Rep (2012) 39:8687–8694 8691
123
keratinocytes [10]. Based on these important roles of
VEGF receptor-2, we hypothesized that VEGF receptor-2
might also be expressed by hair follicle, as which is lined
with epithelial cells.
A decade ago, Kozlowska et al. [13] detected VEGF
expression in human hair follicle. Recently, our study has
shown both VEGF and VEGFR-2 are expressed in human
anagen hair follicle including outer root sheath and dermal
papillae [14]. Furthermore, ORS cells were isolated from
normal human scalp hair follicles and detected by RT-PCR
and western blot analysis which showed the expression of
VEGFR-2 in cultured human ORS cells at mRNA and
protein levels (Fig. 1a, b). And intense immunostaining
signal for VEGFR-2 was observed on ORS cells (Fig. 1c).
To investigate potential effects of VEGF165 on cultured
ORS cells, we performed MTT-based assays which dem-
onstrated that exogenous VEGF165 could stimulate prolif-
eration of cultured ORS cells in a dose-dependent manner
(Fig. 2). Consistent with this, exogenous VEGF165 upreg-
ulated expression of VEGFR-2 at both mRNA and protein
levels in dose-dependent manners (Fig. 3).
The signaling pathways of VEGFR-2 have been well-
investigated in endothelial cells [6–8, 22–24]. MAPK is the
key player in VEGF-induced physiological and
pathological effects including proliferation, migration, sur-
vival and permeability [7, 8]. P38 MAPK has been impli-
cated in VEGFR-2 mediated migration [7, 25], and PI3 K/
Akt pathway is involved in VEGFR-2 mediated migration
and survival [6, 26, 27]. The signaling pathway of cell pro-
liferation induced by VEGFR-2 is extracellular signal reg-
ulated kinase (ERK) pathway, while other proliferation
signaling pathways such as SAPK/JNK, Jak/Stat are not
involved in VEGFR-2 mediated proliferation [7, 8, 21, 23,
24]. Through binding with VEGFR-2, VEGF induces auto-
phosphorylation of VEGFR-2, and then PLC-c1 binds to
phosphorylated Tyr1175 of VEGFR-2 and is tyrosine-
phosphorylated [8, 22]. Phosphorylated PLC-c1 activates
PKC-a by the generation of diacylglycerol and increased
concentration of intracellular calcium [8, 23]. The activated
PKC-a stimulates the mitogen-activated protein kinase
(MAPK)/extracellular-regulated kinase-1/2 (ERK1/2) cas-
cade and mediates the downstream proliferation effect. As
shown in Fig. 4, VEGF stimulated proliferation of cultured
ORS cells via the above VEGF/VEGFR-2/PLC-c1/PKC-a/
MEK/ERK1/2 signaling pathway.
The above data confirm our hypothesis that functional
VEGFR-2 is expressed on human ORS cells and play
important roles in hair follicle, which would improve our
Fig. 4 VEGF165 induced phosphorylation of VEGFR-2(a), PLC-
c1(b), PKC-a(c), MEK(d) and p44/42 MAPK (ERK1/2) (e) in
cultured ORS cells. Serum-starved ORS cells were either untreated or
treated with 50 ng/ml of VEGF165 for 5, 15, 30, 60 or 120 min.
Phosphorylation of VEGFR-2, PLC-c1, PKC-a, MEK and ERK1/2 in
cultured ORS cells responded to VEGF165 in a time-dependent
manner. The histogram below the WB bands show the relative
intensity of phosphorylation of indicated proteins. GAPDH served as
loading control for protein normalization
8692 Mol Biol Rep (2012) 39:8687–8694
123
understanding of hair follicle development, growth, cycling
and the role of hair follicle during wound healing.
Yano et al. [15] proposed a paracrine mechanism of
VEGF by which the proliferative epithelial compartment of
hair follicle induces enhanced vascular support to meet
highly increased nutritional needs during anagen phase, but
our findings indicate that it is not the whole story. Since
ORS cells express functional VEGFR-2, there also exists
an autocrine mechanism. VEGF derived from hair dermal
papilla cells [28], and/or from ORS cells themselves [14,
15], could exert its effects through activating VEGFR-2
expressed on ORS cells. In addition, functional VEGFR-2
expressed on ORS cells provides a novel target of treating
hair disorders such as androgenetic alopecia, the follicles of
which express much less VEGF than normal follicles [29].
Similarly, the key role of ORS cells playing during the
healing of skin wounds [30] may also be mediated by
VEGF/VEGFR-2. More detailed analysis of VEGF/VEG-
FR-2 expressed on ORS cells need further study.
In summary, the present work shows that the human
ORS cells express functional VEGF receptor-2. Exogenous
VEGF upregulates expression of VEGFR-2 and stimulates
proliferation of cultured ORS cells via VEGFR-2 mediated
ERK signaling pathway. Our findings suggest an autocrine
signaling loop in ORS cells and that molecular targeting of
VEGF/VEGFR-2 may be a useful and novel strategy for
treatment of hair disorders.
Acknowledgments This work was supported by grants from the
National Natural Science Foundation of China (NSFC) (No.
81171497, 81171496, 81171521) and Qianjiang Talent Program
2009R10045.
Conflict of interests The authors declare that there is no conflict of
interest.
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