Activation of PKA, p38 MAPK and ERK1/2 by gonadotropins in cumulus cells is critical for induction of EGF-like factor and TACE/ADAM17 gene expression during in vitro maturation of porcine COCs.

Abstract

During ovulation, it has been shown that LH stimulus induces the expression of numerous genes via PKA, p38 MAPK, PI3K and ERK1/2 in cumulus cells and granulosa cells. Our recent study showed that EGF-like factor and its protease (TACE/ADAM17) are required for the activation of EGF receptor (EGFR), cumulus expansion and oocyte maturation of porcine cumulus-oocyte complexes (COCs). In the present study, we investigated which signaling pathways are involved in the gene expression of EGF-like factor and in Tace/Adam17 expression in cumulus cells of porcine COC during in vitro maturation.
Areg, Ereg, Tace/Adam17, Has2, Tnfaip6 and Ptgs2 mRNA expressions were detected in cumulus cells of porcine COCs by RT-PCR. Protein level of ERK1/2 phosphorylation in cultured cumulus cells was analyzed by westernblotting. COCs were visualized using a phase-contrast microscope.
When COCs were cultured with FSH and LH up to 2.5 h, Areg, Ereg and Tace/Adam17 mRNA were expressed in cumulus cells of COCs. Areg, Ereg and Tace/Adam17 gene expressions were not suppressed by PI3K inhibitor (LY294002), whereas PKA inhibitor (H89), p38 MAPK inhibitor (SB203580) and MEK inhibitor (U0126) significantly suppressed these gene expressions. Phosphorylation of ERK1/2, and the gene expression of Has2, Tnfaip6 and Ptgs2 were also suppressed by H89, SB203580 and U0126, however, these negative effects were overcome by the addition of EGF to the medium, but not in the U0126 treatment group.
The results showed that PKA, p38 MAPK and ERK1/2 positively controlled the expression of EGF-like factor and TACE/ADMA17, the latter of which impacts the cumulus expansion and oocyte maturation of porcine COCs via the EGFR-ERK1/2 pathway in cumulus cells.

Full text

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BioMed Central
Page 1 of 9
(page number not for citation purposes)
Journal of Ovarian Research
Open Access
Research
Activation of PKA, p38 MAPK and ERK1/2 by gonadotropins in
cumulus cells is critical for induction of EGF-like factor and TACE/
ADAM17 gene expression during in vitro maturation of porcine
COCs
Yasuhisa Yamashita1, Mitsugu Hishinuma1 and Masayuki Shimada*2
Address: 1School of Veterinary Medicine, Faculty of Agriculture, Tottori University, 4-101 Koyamachou-minami, Tottori, 680-8553, Japan and
2Graduate School of Biosphere Science, Hiroshima University, 1-4-4 Kagamiyama, Higashi-Hiroshima, 739-8528, Japan
Email: Yasuhisa Yamashita - yamayasu@muses.tottori-u.ac.jp; Mitsugu Hishinuma - mhishi@muses.tottori-u.ac.jp;
Masayuki Shimada* - mashimad@hiroshima-u.ac.jp
* Corresponding author
Abstract
Objectives: During ovulation, it has been shown that LH stimulus induces the expression of
numerous genes via PKA, p38 MAPK, PI3K and ERK1/2 in cumulus cells and granulosa cells. Our
recent study showed that EGF-like factor and its protease (TACE/ADAM17) are required for the
activation of EGF receptor (EGFR), cumulus expansion and oocyte maturation of porcine cumulus-
oocyte complexes (COCs). In the present study, we investigated which signaling pathways are
involved in the gene expression of EGF-like factor and in Tace/Adam17 expression in cumulus cells
of porcine COC during in vitro maturation.
Methods: Areg, Ereg, Tace/Adam17, Has2, Tnfaip6 and Ptgs2 mRNA expressions were detected in
cumulus cells of porcine COCs by RT-PCR. Protein level of ERK1/2 phosphorylation in cultured
cumulus cells was analyzed by westernblotting. COCs were visualized using a phase-contrast
microscope.
Results: When COCs were cultured with FSH and LH up to 2.5 h, Areg, Ereg and Tace/Adam17
mRNA were expressed in cumulus cells of COCs. Areg, Ereg and Tace/Adam17 gene expressions
were not suppressed by PI3K inhibitor (LY294002), whereas PKA inhibitor (H89), p38 MAPK
inhibitor (SB203580) and MEK inhibitor (U0126) significantly suppressed these gene expressions.
Phosphorylation of ERK1/2, and the gene expression of Has2, Tnfaip6 and Ptgs2 were also
suppressed by H89, SB203580 and U0126, however, these negative effects were overcome by the
addition of EGF to the medium, but not in the U0126 treatment group.
Conclusion: The results showed that PKA, p38 MAPK and ERK1/2 positively controlled the
expression of EGF-like factor and TACE/ADMA17, the latter of which impacts the cumulus
expansion and oocyte maturation of porcine COCs via the EGFR-ERK1/2 pathway in cumulus cells.
Published: 24 December 2009
Journal of Ovarian Research 2009, 2:20 doi:10.1186/1757-2215-2-20
Received: 27 July 2009
Accepted: 24 December 2009
This article is available from: http://www.ovarianresearch.com/content/2/1/20
© 2009 Yamashita et al; licensee BioMed Central Ltd.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0),
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Background
In mammals, luteinizing hormone (LH) stimulation
induces morphological and physiological changes in
granulosa cells and cumulus cells, causing them to
progress to the ovulation process [1]. During this period,
cumulus cells expressed cumulus expansion-related genes,
Hyaluronan synthase 2 (Has2) [2,3], Tumor necrosis factor α-
induced protein 6 (Tnfaip6) [4,5], and Pentraxin 3 (Ptx3)
[6,7], which is necessary for the synthesis and stability of
hyaluronan-rich extracellular matrix. In Tnfaip6 null mice
[5] or Ptx3 null mice [7], number of ovulated oocytes
decreased and in vivo fertilization was completely inter-
rupted, suggesting that cumulus expansion was essential
for both ovulation and fertilization processes.
It is known that since LH receptor (Lhcgr) is mainly
expressed in granulosa cells, the EGF-like factor produced
in granulosa cells by LH surge acts on cumulus cells to
induce cumulus expansion. Some factors were introduced
to transmit the LH signal from granulosa cells to cumulus
cells. For example, prostagrandin E2 (PGE2) that pro-
duced from granulosa cells and cumulus cells by prosta-
gradin synthase 2 (PTGS2) was required for induction of
Has2 and Tnfaip6 gene, cumulus expansion and oocyte
meiotic resumption [8]. The EGF-like factors, Amphiregu-
lin (AREG), Epiregulin (EREG) and β-cellulin (BTC) were
also recently reported as potent factor. The EGF-like factor
was induced by LH stimuli in granulusa cells, and EGF
receptor (EGFR) was localized on cumulus cells [9-11].
When mouse COCs were cultured with AREG, Has2,
Tnfaip6 and Ptgs2 were expressed in cumulus cells. TACE/
ADAM17, the cleavage enzyme of EGF-like factor to solu-
ble forms, was also expressed in porcine granulosa cells in
vivo in response to hCG administration [12]. Thus, in vivo
during the ovulation process, LH induces EGF-like factor
expression in granulosa cells and the release of the EGF
domain by TACE/ADAM17 acts on cumulus cells, which
induce cumulus expansion.
In in vitro maturation of oocytes, COCs were recovered
from antral follicles and cultured with FSH and/or LH. We
previously showed that FSH and LH up-regulate EGF-like
factor and Tace/Adam17 mRNA expression, and gonado-
tropins-induced cumulus expansion and oocyte matura-
tion of porcine COCs were suppressed by EGF receptor
tyrosine kinase inhibitor or TACE/ADAM17 inhibitor
[13]. The results suggested that FSH- and LH-induced
cumulus expansion was dependent on the expression and
functions of EGF-like factors. Although the regulation of
EGF-like factor expression in cancer cell lines has been
reported [14,15], the mechanisms of EGF-like factor and
TACE/ADAM17 expression in cumulus cells cultured with
FSH and/or LH have remained unclear during in vitro mat-
uration of porcine COCs.
The binding of FSH and/or LH in granulosa cells to its
own receptors led to rapidly and nongenomic activation
of PKA, p38 MAPK, and PI3K in a cAMP-dependent man-
ner [16] and of ERK1/2 via the SRC/RAS-dependent path-
way [17]. In mice, since each inhibitor of PKA, p38 MAPK,
PI3K or ERK1/2 suppressed the expression of cumulus
expansion-related gene [10,18,19], cumulus expansion
[18,19] or meiotic maturation of oocyte [20], we esti-
mated that these signaling pathways induced by gonado-
tropin overlap the EGF-like factor-EGFR pathway, which
induces full cumulus expansion and oocyte maturation.
In this study, to clarify the intracellular pathway involved
in EGF-like factor and Tace/Adam17 expression in cumu-
lus cells, we examined the effect of PKA inhibitor (H89),
p38 MAPK inhibitor (SB203580), PI3K inhibitor
(LY294002) and MEK inhibitor (U0126) on Areg, Ereg
and Tace/Adam17 expression in cumulus cells during in
vitro maturation of porcine COCs. Additionally, we inves-
tigated the effect of these drugs on ERK1/2 phosphoryla-
tion, cumulus expansion and oocyte meiotic resumption
in pig.
Methods
Materials
High purified porcine FSH and porcine LH were gifts from
the National Hormone and Pituitary Program (Rockville,
MD, USA). Fetal calf serum (FCS) was obtained from Inv-
itrogen (Carlsbad, CA, USA). Oligonucleotide poly- (dT)
was purchased from Amersham Pharmacia Biotech
(Newark, NJ, USA). Avian myeloblastosis virus reverse
transcriptase and Taq DNA Polymerase were from
Promega (Madison, WI). Routine chemicals and reagents
were obtained from Nakarai Chemical Co. (Osaka, Japan)
or Sigma (Sigma Chemical Co., St. Louis, MO, USA).
In vitro culture of porcine COCs
Isolation of porcine COCs was described previously [21].
Briefly, porcine ovaries were recovered from 5- to 7-
month-old prepubertal gilts at a local slaughterhouse.
COCs were collected from the surfaces of intact healthy
antral follicles measuring from 3 to 5 mm in diameter.
The 20 COCs were cultured up to 40 h with both 20 ng/
ml highly purified porcine FSH (NIDDK, Torrance, CA)
and 500 ng/ml porcine LH (NIDDK). The maturation
medium was modified NCSU37 [22] supplemented with
10% (v/v) FCS (Gibco BRL, Grand Island, NY) and 7 mM
Taurine (Sigma St Louis, MO). At selected time intervals,
COCs were collected for RNA and protein isolation.
The assessment of cumulus expansion was observed using
phase-contrast microscopy (Olympus IMT2, Olympus,
Tokyo Japan) and a 10× objective.

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Treatment with inhibitors
In the case of treatment with each specific inhibitor,
namely PKA, H89 (10 uM) (Sigma), p38 MAPK,
SB203580 (20 uM) (Sigma), PI3K, LY294002 (20 uM)
(Sigma) or MEK, U0126 10 uM (Sigma), COCs were cul-
tured for 0, 2.5, 5, 10, 20 or 40 h with each of these inhib-
itors. H89 was dissolved in maturation medium at 10 mM
and stored at -20°C. SB203580, LY294002 and U0126
were dissolved in dimethylsulfoxide (DMSO) at 20 mM
and 10 mM, respectively, and stored at -20°C. The final
concentration of each compound (as described above)
was obtained by dilution (1:1000) with the maturation
medium. The final concentration of vehicles (DMSO) was
0.1% (vol/vol), which did not affect the function of
cumulus cells during meiotic resumption of porcine
oocytes [23].
RNA isolation
After cumulus cells were cultured, they were washed three
times in PBS. Total RNA was extracted from cumulus cells
using the SV Total RNA Isolation System (Promega)
according to the instruction manual, and dissolved in
nuclease-free water. The final RNA concentrations were
determined by absorbance using a spectrophotometer.
RT-PCR
RT-PCR analyses were performed as previously described
[22]. Briefly, total RNA was reverse-transcribed using 500
ng poly-dT and 0.25 U of avian myeloblastosis virus-
reverse transcriptase at 42°C for 75 min and 95°C for 5
min. PCR conditions were set as follows: cDNA was
amplified for X cycles (Table 1) of denaturation at 94°C
for 30 sec, primer annealing at Y°C (Table 1) for 1 min,
and extension at 68°C for 1 min, with a final extension
step of 7 min at 68°C. β-actin was used as a control for
reaction efficiency and variations in concentration of
mRNA in the original RT reaction. The amplified products
were analyzed by electrophoresis on 2% agarose gels. The
intensity of the objective bands was quantified by densit-
ometric scanning using a Gel-Pro Analyzer. Specific
primer pairs were selected and analyzed as indicated in
Table 1.
Western blot analysis
Cumulus cells were lysed in Laemmli sample buffer and
protein extracts were stored at -80°C until use. After dena-
turing by boiling for 5 min, 10 ul of each samples contain-
ing equal amounts of protein (10 ug) was separated by
SDS-PAGE on 10% polyacrylamide gel, then transferred
onto PVDF membrane (GE Healthcare). The membrane
was blocked with 5% (w/v) nonfat dry milk (GE Health-
care) in PBS. Primary antibodies were added in 2.5% (w/
v) nonfat dry milk in 0.1% (v/v) Tween 20 (Sigma)/PBS
(PBS-T), and incubated overnight at 4°C. Anti-phospho-
ERK1/2 and β-ACTIN were purchased from Cell Signaling
Technology, Inc (Beverly, MA) and diluted at 1:2,000 or
1:10,000, respectively. After four washes in PBS-T, the
membranes were incubated for 1 h with a 1:2,000 dilu-
tion of goat anti-rabbit IgG HRP-linked antibody (Cell
Signaling Technology, Inc) in 2.5% (w/v) nonfat dry milk
in PBS-T at room temperature. After five washes of 10 min
each with PBS-T, peroxidase activity was visualized using
the ECL Western blotting detection system (GE Health-
care) according to the manufacturer's instructions.
Statistical analysis
Statistical analyses of all data from three or four replicates
for comparison were carried out by one-way ANOVA fol-
lowed by Duncan's multiple-range test (Statview; Abacus
Concepts, Inc., Berkeley, CA). All percentage data were
subjected to arcsine transformation before analysis.
Results
Effect of each specific inhibitor of PKA, p38 MAPK, PI3K
and MEK on the gonadotropin-induced Areg, Ereg and
Tace/Adam17 mRNA expression during in vitro maturation
of porcine COCs
COCs were cultured with FSH, LH and/or PKA inhibitor
(H89), p38 MAPK inhibitor (SB203580), MEK inhibitor
(U0126) or PI3K inhibitor (LY294002) for 2.5 h. The
results showed that high levels of Areg, Ereg and Tace/
Adam17 mRNA were observed when COCs were cultured
with FSH and LH, and that the levels were not affected by
LY294002 (Figure 1A, B, C). However, treatment with
H89, SB203580 or U0126 significantly decreased these
Table 1: List of primers employed for RT-PCR
GeneForward PrimerReverse Primer Anneling
temprature
(X)
Cycle (Y)
-actin
Areg
Ereg
Tace/
Adam17
Has2
Tnfaip6
Ptgs2
5'-CTA CAA TGA GCT GCG TGT GG-3'
5'-CAC CAG AAC AAA AAG GTT CTG TC-3'
5'AAG ACA ATC CAC GTG TGG CTC AAG-3'
5'-GAC ATG AAT GGC AAA TGT GAG AAA C-3' 5'-AGT CTG TGC TGG GGT CTT CCT GGA-3'
5'-TAG CTC TTC TCC AGG GAG GA-3'
5'-AAG TCC ATG AAG ACT CAC ACC AT-3'
5'-CGA TTT TTG TAC CAT CTG CAG AAA-3'
58
58
58
58
31
35
35
34
5'-GAA TTA CCC AGT CCT GGC TT-3'
5'-TCA TAA CTC CAT ATG GCT TGA AC-3'
5'-CTG CCG TGT CGC TCT GCA CTG-3'
5'-GGA TAA ACT GGT AGC CAA CA-3'
5'-TCT TCG TAC TCA TTT GGG AAG CC-3'
5'-TCA TAA CTC CAT ATG GCT TGA AC-3'
54
54
58
35
32
35

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mRNA expression levels in cumulus cells (Figure 1A, B,
C).
Effect of each specific inhibitor of PKA, p38 MAPK and
MEK on ERK1/2 phosphorylation in cumulus cells during in
vitro maturation of porcine COCs
When COCs were cultured with FSH and LH for 5 h, the
phosphorylation status of ERK1/2 was detected. The addi-
tion of H89 or SB20580 to the medium significantly
decreased the intensity of bands as compared with those
in cumulus cells of COCs cultured without any inhibitor,
and these inhibitory effects were overcome by addition of
EGF (Figure 2). Treatment with U0126 also significantly
suppressed ERK1/2 phophorylation in cumulus cells as
compared with those in cumulus cells of COCs cultured
without U0126; however, the addition of EGF to U0126-
contained medium did not affect the phosphorylation.
High levels of Has2, Tnfaip6 and Ptgs2 expression were
observed in cumulus cells of COCs cultured for 10 h with
FSH and LH as compared with those cultured without
FSH and LH. The addition of H89, SB20580 or U0126 sig-
nificantly suppressed FSH- and LH-induced Has2, Tnfaip6
and Ptgs2 expressions (Figure. 3A, B, C). Although the
lower level of these gene expressions resulting from the
addition of U0126 was not overcome by the addition of
EGF, the addition of EGF to H89- or SB203580-contain-
ning medium overcame the negative effect of each inhib-
itor on these gene expressions (Figure. 3A, B, C).
Effect of each specific inhibitor of PKA, p38 MAPK and
MEK on meiotic resumption of oocytes and cumulus
expansion during in vitro maturation of porcine COCs
When COCs were cultured without FSH and LH for 20 h,
the proportion of oocytes exhibiting GVBD was less than
25%. FSH and LH significantly increased the proportion
of oocytes exhibiting GVBD. This higher rate was signifi-
cantly decreased by H89 or SB20580, and the suppression
was counteracted by the addition of EGF (Figure 4). Treat-
ment with U0126 also significantly suppressed the GVBD
rate, whereas the addition of EGF did not overcome the
negative effects.
The culture of COCs with FSH and LH for 40 h induced
the full expansion of COCs (Figure. 5). The expansion was
completely suppressed by treatment with H89, SB20580
or U0126 for 40 h. Although the negative effects of H89
and SB20580 were overcome by the addition of EGF, the
treatment with EGF did not overcome the negative effects
of U0126.
Discussion
Recently, it has been showed that the novel paracrine/
autocrine factors expressed in granulosa cells and cumu-
lus cells by LH stimuli acted on cumulus cells to induce
cumulus expansion, meiotic maturation of oocytes and
ovulation in mouse [9-11]. Since the suppression of the
EGF receptor tyrosine kinase activity by specific inhibitor
completely suppressed cumulus expansion and meiotic
maturation of oocytes during in vitro maturation of
mouse COCs [9], the EGF-like factor was quite important
for ovulatory process. During in vitro maturation of por-
cine COCs, the addition of EGF to maturation medium
significantly elevated developmental competence of
oocytes to blastocyst stage [12], indicating that investiga-
tion of the transcriptional mechanism of the EGF-like fac-
tor and TACE/ADAM17 was essential for not only
ovulatory process, but also cytoplasamic maturation of
oocyte.
It has been reported that during the ovulation process the
PKA-dependent pathway involving the ligand activation
of G protein-coupled receptors by their ligands in cumu-
lus and/or granulosa cells induced the expression of ovu-
lation-related genes, including Cyp11a1 [24], Star [25]
and Ptgs2 [26]. Other reports documented that, in rat
granulosa cells, FSH and LH up-regulated the phosphor-
ylation of p38 MAPK by a PKA-independent mechanism
that might be involved in Epac [27]. Furthermore, a recent
report showed that FSH nongenomically activates ERK1/2
via SRC/RAS dependent pathway in rat granulosa cells
[17], indicating that the activation of ERK1/2 was not
directly activated by cAMP-activated PKA or p38 MAPK
pathway. In this study, when porcine COCs were cultured
for 2.5 h with PKA inhibitor, p38 MAPK inhibitor or MEK
inhibitor, FSH- and LH-induced Areg, Ereg, and Tace/
Adam17 mRNA expressions were significantly suppressed.
In osteoblastic cells, the promoter region of the Areg gene
had a putative CRE site, and the region was quite impor-
tant for parathyroid hormone-induced Areg gene induc-
tion via CREB phosphorylation [28]. In rat granulosa
cells, it has been reported that the phosphorylation of
CREB was induced by FSH within 1.5 h [29]. Our recent
study showed in rat granulosa cells that phosphorylation
of CREB was induced by FSH dependent manner and the
phosphorylation of CREB was essential for transcription
of Areg mRNA via its promoter region of CRE site (Shitan-
aka et al., unpublished data). We also showed in granu-
lose-specific Erk1/2 knockout mice that Areg expression
level was significantly lower than that in wild-type mice
[30]. It is known that CREB has the sites phosphorylated
by ERK1/2 and p38 MAPK [31,32]. Thus, at early in the
process, p38 MAPK and ERK1/2 might be involved in the
phosphorylation of CREB, which would induce Areg gene
expression in cumulus cells of porcine COCs.
Our previous study showed that EGFR tyrosine kinase
inhibitor or TACE/ADAM17 inhibitor suppressed the
phosphorylation of ERK1/2 and the meiotic resumption
of oocytes [13]. In this study, the addition of EGF to PKA

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Effect of H89, SB203580, LY294002 or U0126 on Areg(A), Ereg(B) or Tace/Adam17(C) mRNA
Figure 1
Effect of H89, SB203580, LY294002 or U0126 on Areg(A), Ereg(B) or Tace/Adam17(C) mRNA. For reference, the
0 h COC value was set as 1 and the data presented as the fold strength. Values are mean +/- SEM of 3 replicates. *: The signif-
icant differences were observed as compared with that in COCs cultured with FSH and LH for 2.5 h. The respective value of
among Areg, Ereg, and Adam17 mRNA were normalized according to those of -actin mRNA to evaluate arbitrary units of the
relative abundance of the targets. Free: COCs were cultured without FSH and LH for 2.5 h; Cont: COCs were cultured with
FSH and LH for 2.5 h; H89: COCs were cultured with FSH, LH and H89 for 2.5 h; SB: COCs were cultured with FSH, LH and
SB203580 for 2.5 h; LY: COCs were cultured with FSH, LH and LY294002 for 2.5 h; U0126: COCs were cultured with FSH,
LH and U0126 for 2.5 h
Tace/Adam17?
*?
C?
*?
0
1
2
3
4
5
FreeContH89 SBLY U0126
Fold strength
*?
Ereg?
B?
*?
*?
0
5
10
15
20
25
30
35
40
FreeContH89SBLY U0126
Fold strength
*?
Areg?
A?
*?
*?
0
40
80
120
160
200
FreeCont H89SBLY U0126
Fold strength
*?

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Effect of H89, SB203580 or U0126 on ERK1/2 phosphoryla-tion in cumulus cells
Figure 2
Effect of H89, SB203580 or U0126 on ERK1/2 phos-
phorylation in cumulus cells. For reference, the COC
that were cultured without FSH and LH for 5 h value was set
as 1 and the data presented as the fold strength. Values are
mean +/- SEM of 3 replicates. *: The significant differences
were observed as compared with that in COCs cultured
with FSH and LH for 5 h. **: The significant differences were
observed as compared with that in COCs cultured with FSH,
LH, H89 and EGF for 5 h. ***: The significant differences
were observed as compared with that in COCs cultured
with FSH, LH SB230580 and EGF for 5 h. The respective
value of protein levels of ERK1/2 phosphorylation were nor-
malized according to those of β-ACTIN to evaluate arbitrary
units of the relative abundance. FSH(-): COCs were cultured
without FSH and LH for 5 h; FSH(+): COCs were cultured
with FSH and LH for 5 h; EGF(-): COCs were cultured with-
out EGF for 5 h; EGF(+): COCs were cultured with EGF for
5 h; +H89: COCs were cultured with H89 for 5 h; +SB:
COCs were cultured with SB203580 for 5 h; +U0126: COCs
were cultured with U0126 for 5 h
Effect of H89, SB203580 or U0126 on expression of
Has2(A), Tnfaip6(B) or Ptgs2(C) mRNA
Figure 3
Effect of H89, SB203580 or U0126 on expression of
Has2(A), Tnfaip6(B) or Ptgs2(C) mRNA. For reference,
the 0 h COC value was set as 1 and the data presented as
the fold strength. Values are mean +/- SEM of 3 replicates. *:
The significant differences were observed as compared with
that in COCs cultured with FSH and LH for 10 h. **: The sig-
nificant differences were observed as compared with that in
COCs cultured with FSH, LH, H89 and EGF for 10 h. ***:
The significant differences were observed as compared with
that in COCs cultured with FSH, LH, SB230580 and EGF for
10 h. The respective value of among Has2, Tnfaip6 and Ptgs2
mRNA were normalized according to those of -actin mRNA
to evaluate arbitrary units of the relative abundance of the
targets. FSH(-): COCs were cultured without FSH and LH
for 10 h; FSH(+): COCs were cultured with FSH and LH for
10 h; EGF(-): COCs were cultured without EGF for 10 h;
EGF(+): COCs were cultured with EGF for 10 h; +H89:
COCs were cultured with H89 for 10 h; +SB: COCs were
cultured with SB203580 for 10 h; +U0126: COCs were cul-
tured with U0126 for 10 h
Has2?
A?
B?
C?
0
2
4
6
8
10
12
14
16
Fold strength
*?
*?
*?
***?
**?
0
5
10
15
20
25
Fold strength
0
1
2
3
4
5
6
7
8
9
Fold strength
*?
*?
*?
***?
**?
Ptgs2?
Tnfaip6?
*?
*?
*?
***?
**?
FSH+LH?
??
??
??
??
??
??
??
??
EGF?
??
??
??
+H89?
+SB?
+U0126?
??
??
??
??
??

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or p38 MAPK inhibitor-containing medium overcame the
negative effects or cumulus expansion and oocyte meiotic
resumption. However, when COCs were cultured with
U0126, the treatment with EGF did not overcome the
U0126 effects. Thus, the MEK-ERK1/2 pathway played
dual roles in cumulus cells. One role is the induction of
EGF-like factor and TACE/ADAM17 expression. The other
is direct induction of cumulus expansion of porcine
COCs. In granulosa cell specific Erk1/2 knockout mice,
the cumulus expansion was completely suppressed via the
low induction of Ptgs2 expression. In this study, the Ptgs2
expression level was suppressed by U0126, suggesting that
EGF-like factor was required for the induction of cumulus
expansion and oocyte meiotic resumption in porcine
COCs as well as in mice.
Conclusion
Herein, we showed that the expression of EGF-like factor
and TACE/ADAM17 in cumulus cells was induced by a
PKA-, p38 MAPK- and ERK1/2-dependent mechanism
during in vitro maturation of porcine COCs. The intracel-
lular mechanism of induction of the expression of EGF-
like factor and TACE/ADAM17 further induce EGF-like
factor and Tace/Adam17 mRNA expressions in cumulus
cells via ERK1/2 activation. Thereby, the ERK1/2 main-
tained its activity via the EGF domain-EGFR-ERK1/2 path-
way, which resulted in full cumulus expansion, and
oocyte maturation during in vitro maturation of porcine
COCs.
Effect of H89, SB203580 or U0126 on rate of oocyte exhibit-ing GVBD
Figure 4
Effect of H89, SB203580 or U0126 on rate of oocyte
exhibiting GVBD. Values are mean +/- SEM of 3 replicates.
*: The significant differences were observed as compared
with that in COCs cultured with FSH and LH for 20 h. **:
The significant differences were observed as compared with
that in COCs cultured with FSH, LH, H89 and EGF for 20 h.
***: The significant differences were observed as compared
with that in COCs cultured with FSH, LH, SB230580 and
EGF for 20 h. FSH(-): COCs were cultured without FSH and
LH for 20 h; FSH(+): COCs were cultured with FSH and LH
for 20 h; EGF(-): COCs were cultured without EGF for 20 h;
EGF(+): COCs were cultured with EGF for 20 h; +H89:
COCs were cultured with H89 for 20 h; +SB: COCs were
cultured with SB203580 for 20 h; +U0126: COCs were cul-
tured with U0126 for 20 h
0
10
20
30
40
50
60
70
80
90
100
GVBD (%)
*?
*?
*?
***?
**?
FSH+LH?
??
??
??
??
??
??
??
??
EGF?
??
??
??
+H89?
+SB?
+U0126?
??
??
??
??
??
Effect H89, SB203580 or U0126 on cumulus expansion of cultured COCs
Figure 5
Effect H89, SB203580 or U0126 on cumulus expan-
sion of cultured COCs. Without FSH and LH: COCs were
cultured without FSH and LH for 40 h; With FSH and LH:
COCs were cultured with FSH and LH for 40 h; +H89:
COCs were cultured with FSH, LH and H89 for 40 h;
+H89+EGF: COCs were cultured with FSH, LH, H89 and
EGF for 40 h; +SB: COCs were cultured with FSH, LH and
SB203580 for 40 h; +SB+EGF: COCs were cultured with
FSH, LH, SB and EGF for 40 h; +U0126: COCs were cultured
with FSH, LH and U0126 for 40 h; +U0126+EGF: COCs
were cultured with FSH, LH, U0126 and EGF for 40 h.

Page 8

Journal of Ovarian Research 2009, 2:20http://www.ovarianresearch.com/content/2/1/20
Page 8 of 9
(page number not for citation purposes)
Abbreviations
FSH: follicle stimulating hormone; LH: luteinizing hor-
mone; EGF-like factor: epidermal growth factor-like fac-
tor; TACE/ADAM17: tumor necrosis factor α converting
enzyme/a disinteglin and metalloptotease 17; Has2:
hyaluronan synhase 2; Tnfaip6; tumor necrosis factor α-
induced protein 6; Ptx3: pentraxin 3; PGE2: prostagrandin
E2; PTGS2; prostagrandin synthase 2; AREG; amphiregu-
lin; EREG: epiregulin; BTC: β-cellulin; EGFR: EGF recep-
tor; hCG: human chorionic gonadotropin; COC:
cumulus-oocyte complex; PKA: protein kinase A; p38
MAPK: p38 mitogen-activated protein kinase; PI3K: phos-
phatidylinositol 3-kinase; ERK: extracellular-signal regu-
lated protein; SRC: rous sarcoma oncogene; RAS: rat
sarcoma viral oncogene.
Competing interests
The authors declare that they have no competing interests.
Authors' contributions
YY and MS conceived of the study, participated in its
design and coordination and drafted the manuscript. All
authers read and approved the final manuscript.
Acknowledgements
Supported, in part, by grant-in-Aid for Scientific Research (Y.Y., No.
19880020) and (M.S., No. 18688016) from the Japan Society for the Pro-
motion of Science (JSPS). Porcine FSH and LH were kindly provided by Dr.
A.F. Parlow, the National Hormone and Pituitary Program, the National
Institute of Diabetes and Digestive and Kidney Disease, USA. We thank Mr.
I Kawashima, Mr. T. Mizukami, Mr. T. Koike, and Ms. M. Okamoto for tech-
nical assistance. We also thank the staff of the Meat Inspection Office in
Hiroshima City and Tottori prefecture for supplying the porcine ovaries.
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