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Departments of Obstetrics and Gynecology (J.J.K., A.T.F.) and Physiology and Biophysics (R.C.J., A.T.F.), University of Illinois at Chicago, Chicago, Illinois 60212-7313
Address all correspondence and requests for reprints to: Dr. A. T. Fazleabas, Department of Obstetrics and Gynecology, University of Illinois at Chicago, 820 South Wood Street (M/C 808), Chicago, Illinois 60612. E-mail: asgi{at}uic.edu
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Abstract |
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Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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The sequence of biochemical and molecular events associated with the
transformation of a stromal fibroblast to a secretory decidual cell
remains unclear. We have previously demonstrated that the baboon
endometrium undergoes a complex series of changes during the
establishment of pregnancy and that the conceptus is essential to
regulate these changes (6, 7). Specifically, stromal fibroblasts
sequentially express 
-smooth muscle actin (SMA), a cytoskeletal
protein, followed by IGFBP-1 (6, 7, 8). SMA and IGFBP-1 are not
expressed in stromal fibroblasts during the menstrual cycle in the
baboon.
Cytoskeletal proteins are important in mitosis, cell growth, changes in
cell shape, and for the regulation of protein secretion (9). Several
studies have demonstrated the importance of the actin cytoskeleton or
actin binding proteins in cellular differentiation of granulosa cells
(10), chondrocytes (11), and HL-60 cells (12). In the baboon, specific
staining for SMA was observed in the stromal fibroblasts during
early pregnancy or simulated pregnancy (8). As cells subsequently
expressed IGFBP-1 as part of the decidualization process, SMA
staining disappeared. This phenomenon has also been demonstrated
in vitro (13). Stromal cells from nonpregnant baboons
expressed SMA spontaneously after attachment and spreading. After 17
days of continuous hormone and (Bu)2cAMP treatment,
significant levels of IGFBP-1 were produced with a corresponding
decrease in SMA expression. This transitory expression of SMA
demonstrated in vivo and in vitro and its
association with an alteration in cell morphology and the appearance of
IGFBP-1 in pregnant baboons suggested that SMA is associated with
the transformation of a stromal fibroblast to a decidual cell. We
hypothesize that restructuring of the cytoskeleton is required for
expression of the IGFBP-1 gene. In the present study, we have
demonstrated that disruption of the cytoskeleton in vitro
potentiates the expression of IGFBP-1. Furthermore, this expression
requires de novo protein synthesis. As a comparison, the
expression of IGFBP-1 in stromal cells from pregnant and simulated
pregnant animals was also analyzed. In vivo priming of these
cells by pregnancy-associated factors induces the expression of SMA
in the stromal fibroblasts (8). Induction of IGFBP-1 and the associated
down-regulation of SMA occurs at the site of implantation and
requires the presence of the conceptus (13, 14). The in
vitro studies described herein also demonstrate that
(Bu)2cAMP potentiates IGFBP-1 expression in stromal cells
that are expressing SMA in vivo with a requirement for
de novo protein synthesis.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Cell culture
Endometrial tissues were obtained from cycling (day 9–10
postovulation), human CG (hCG)-treated (simulated pregnant), and day 22
pregnant baboons (Papio anubis) by endometriectomy or after
hysterectomy. All animal studies were approved by the Animal Care
Committee of the University of Illinois at Chicago. The day of
ovulation was designated to be 2 days after the estradiol surge and was
confirmed by prospective measurement of peripheral serum levels of
estradiol and progesterone (14). To simulate pregnancy, normally
cycling animals received increasing dosages of recombinant hCG
(Serono Laboratories, Inc., Norwell, MA). This treatment
regimen resulted in peripheral levels of hormones comparable to those
measured on day 18 of pregnancy (14).
The tissue was minced thoroughly in calcium- and magnesium-free HBSS and placed in an enzyme solution containing 0.5% collagenase and 0.02% deoxyribonuclease (DNase). They were incubated for 20 min at 37 C in a shaking water bath. The supernatant was recovered and placed at 4 C. The remaining tissue was further digested in an enzyme solution consisting of 0.5% collagenase, 0.02% DNase, 0.1% hyaluronidase, and 0.1% pronase and processed as described above. The cell suspensions from the first and second digestions were centrifuged at 1,500 x g for 5 min, and the pellet was resuspended in HBSS. The cells were then passed through a 95-µm nylon mesh folllowed by a 20-µm nylon mesh (Small Parts, Inc., Miami Lakes, FL). The filtrates were pooled and centrifuged again at 1,500 x g for 5 min. The pellet was resuspended in 30% Percoll solution and overlayed on top of a 60% Percoll solution. After centrifugation at 800 x g for 30 min, the cells that sedimented at the 30%–60% interface were collected. The cells were then resuspended in phenol red-free RPMI-1640 supplemented with 0.1 mM sodium pyruvate, 100 U/ml penicillin, 100 µg/ml streptomycin, and 10% FBS depleted of steroids by treatment with dextran-coated charcoal (stripped). Cells were seeded at 1 x 105 cells/cm2 and incubated overnight at 37 C and 5% C02. The medium was changed the next day and subsequently every 3 days. Cell purity was assessed by immunocytochemistry using antibodies against cytokeratin (Dako Corp., Carpenteria, CA), vimentin (Zymed Laboratories, Inc., San Francisco, CA) and Factor VIII (Dako Corp.). The purity of the stromal cell preparations used in these studies was more than 97%.
Treatment of cells
At approximately 80% confluency, the cell culture medium was
changed to RPMI-1640 supplemented with sodium pyruvate,
penicillin/streptomycin, 10% stripped FBS, with or without 5
µM cytochalasin D. Cytochalasin D is a specific inhibitor
of the actin microfilament assembly (15). Photographs of cells were
taken at 10 min, 30 min, 50 min, 100 min, 2 h, 3 h, 4 h,
and 5 h of cytochalasin D treatment. Cells were also treated with
6.7 µM nocodazole, a microtubule-dissociating drug, for
5 h. Medium was then changed to RPMI-1640, 2% stripped FBS, 5
µM cytochalasin D, with or without hormones (36
nM 17ß-estradiol, 1 µM MPA, and 100
ng/ml highly purified porcine relaxin, kindly provided by Dr. David
Sherwood, University of Illinois, Urbana), and with or without 0.1
mM (Bu)2cAMP. Treatment continued for an
additional 24 or 48 h. For cycloheximide studies, 5 h after
initiation of cytochalasin D treatment, cells were pretreated with
cycloheximide for 1 h by changing medium to RPMI-1640 plus 2%
stripped FBS, 5 µM cytochalasin D, and 10 µg/ml
cycloheximide. The concentrations of cytochalasin D and nocodazole used
in these studies were based on previous reports describing
actin-mediated gene transcription in fibroblasts (15, 16). The
concentrations were confirmed as being nontoxic to the cells by the
measurement of lactate dehydrogenase (LDH) in the media at various time
points. Cyclohexamide was used at a concentration that had been
previously reported to inhibit IGFBP-1 synthesis in vitro
(17).
After pretreatment, the medium was changed again to RPMI-1640, 2% stripped FBS, 10 µg/ml cycloheximide, 5 µM cytochalasin D, with or without hormones, with or without 0.1 mM (Bu)2cAMP for 24 and 48 h. The medium was collected and IGFBP-1 present in the culture medium was measured using an enzyme-linked immunosorbent assay (ELISA) kit (Diagnostic Systems Laboratories, Inc., Webster, TX). Cells were lysed with TriReagent (Molecular Research Center, Inc., Cincinnati, OH) and RNA and protein were extracted using the protocol provided by the manufacturer. Cellular protein content was measured using the Micro BCA protein assay kit (Pierce, Rockford, IL).
RT-PCR
The RNA preparation isolated from cells was treated with 1
U/µl DNase (Promega Corp.). RT was then performed in a
final volume of 20 µl with 1 µg RNA and 50 U/µl MuLV reverse
transcriptase at 42 C for 30 min. PCR amplification was performed with
the RT product, the appropriate primers (50 pmol/tube), 0.5 µl of 5
U/ml Taq polymerase (Gibco BRL), and 0.25 µl
of 10 mCi/ml [32P]deoxycytosine triphosphate.
After an initial incubation at 94 C for 10 min, 24 amplification cycles
consisting of 94 C (1 min), 60 C (2 min), and 72 C (3 min) were
performed followed by 15 min of final extension at 72 C. Primers for
H3.3, IGFBP-1, and SMA, described in Kim et al. (13),
were added together in a single tube so that amplification of the cDNAs
for H3.3, IGFBP-1, and SMA occurred in the same tube. The PCR
products were electrophoresed in 1.5% agarose gels, and the gels were
dried and exposed to film.
Immunofluorescent staining
Stromal cells isolated from baboons on day 10 post ovulation
were grown on glass coverslips. Cells were treated with cytochalasin D,
as described above, followed by incubation in the presence or absence
of 0.1 mM (Bu)2cAMP for 72 h. Control
cells were not treated with cytochalasin D. The additional 24-h
incubation time for the immunocytochemical studies was to ensure that
we could detect an effect of (Bu)2cAMP on IGFBP-1 synthesis
in the control cells (13).
At the end of the incubation period the medium was removed and cells were washed three times with PBS. Cells were fixed in 4% paraformaldehyde for 10 min and washed three times with PBS. The cells were then permeabilized with 0.1% Triton X-100/0.1% deoxycholate in PBS for 10 min. After a PBS wash the permeabilized cells were incubated with a filtered solution of 1% BSA in PBS for 10 min. A monoclonal IGFBP-1 antibody [1:1000 in 1% BSA in PBS (17)] was added to the cells and incubated overnight at 4 C. Cells were washed three times with PBS and incubated with a fluorescein-conjugated antimouse IgG second antibody (10 µg/ml; Vector Laboratories, Inc., Burlingame, CA). In conjuction with the fluorescein-conjugated second antibody, rhodamine-labeled phalloidin (1:100; Sigma Chemical Co.) was also added. Incubations were done in the dark at room temperature for 1 h. The cells were washed with PBS and the cover slips were mounted on glass microscope slides with a drop of Vectashield mounting medium (Vector Laboratories, Inc., Burlingame, CA). Fluorescence corresponding to the antigen-antibody complexes for actin and IGFBP-1 were photographed using an inverted IM35 fluorescent microscope (Carl Zeiss, Thornwood, NY). Double exposures for the colocalization of actin and IGFBP-1 were created by superimposing the rhodamine signal (exposure time 1 sec) on the IGFBP-1 fluorescence signal (exposure time 5 sec) using Kodak Gold 200 ASA color film (Eastman Kodak Co., Rochester, NY).
Statistical analysis
Data were analyzed by least-squares ANOVA using the SuperANOVA
software package (Abacus Concepts, Inc., Berkeley, CA). Sources of
variation included experiment (defined as tissues from different
animals), treatment (presence or absence of
hormones/(Bu)2cAMP), drug (presence or absence of
cytochalasin D or nocodazole), and their interactions. Data were log
transformed, and orthogonal contrasts were used to compare the means of
the different treatments with their corresponding controls. The pattern
of IGFBP-1 protein expression at 24 h and 48 h were the same
and thus the data at these two time points were pooled (Fig. 4A
).
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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) similar to endometrial stromal cells
from other species. Within 10 min of the addition of 5 µM
cytochalasin D, cytoplasmic contractions were apparent under the
phase-contrast microscope (Fig. 1B). Cells continued to contract (Fig. 1, C–I) and by 5 h, cells had lost their fibroblast-like shape
and had become rounded with numerous thin filopodia (Fig. 1I). Cell
viability at this time was assessed by assaying for LDH in the culture
media. No LDH activity was detected.
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). Within 1 h of drug removal,
cells reverted back to their fibroblastic shape (Fig. 2F), although the
morphology was not identical to untreated stromal cells (Fig. 1A
),
i.e. stress fibers (Fig. 2F) were not as evident as those of
the untreated cells (Fig. 1A). To determine whether these morphological
changes were specifically associated with the disruption of the actin
filaments, cells were also treated with the microtubule dissociating
drug, nocodazole (6.7 µM). The morphological changes
associated with this treatment (Fig. 3B)
were not significantly different from those observed in untreated cells
(Fig. 3A). Cells remained fibroblastic.
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, A and B). In contrast, when cells were
treated with cytochalasin D, further treatment with
(Bu)2cAMP only (P 
0.05), hormones only
(P 0.05), and hormones in conjunction with
(Bu)2cAMP (P 0.05), increased IGFBP-1
protein (Fig. 4A) and mRNA (Fig. 4B) expression within 24 and 48
h. Cells with disrupted actin filaments that were treated with hormones
alone produced lower levels of IGFBP-1 compared with treatments with
(Bu)2cAMP alone and hormones plus (Bu)2cAMP.
When cells resumed their fibroblastic shape after the withdrawal of
cytochalasin D, IGFBP-1 was induced in response to hormones and
(Bu)2cAMP, irrespective of repolymerization of actin
microfilaments, albiet to a significantly lower concentration (6.7
ng/ml) than in the presence of cytochalasin D (26 ng/ml). The protein
concentrations were reflective of the IGFBP-1 mRNA levels as
determined by semiquantitative RT-PCR (data not shown).
The localization of IGFBP-1 in cells treated with (Bu)2cAMP
with or without the disruption of the cytoskeleton is shown in Figure 5. As we had previously demonstrated,
incubation of stromal fibroblasts with (Bu)2cAMP induces
low levels of IGFBP-1 [Fig. 5B (13)]. In contrast, the disruption of
the cytoskeleton with cytochalasin D results in a marked increase in
IGFBP-1 immunolocalization (Fig. 5D). In the absence of
(Bu)2cAMP, no staining for IGFBP-1 is evident (Fig. 5, A
and C).
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0.05).
IGFBP-1 expression in response to (Bu)2cAMP alone and
hormones alone did not significantly differ from control cells
with the same treatments. In addition, levels of IGFBP-1 expression
in nocodazole-treated cells in response to hormones plus
(Bu)2cAMP were much lower than that observed for
cytochalasin D- treated cells.
IGFBP-1 expression requires de novo protein synthesis
After treatment with cytochalasin D, cycloheximide was added to
the cells together with the different hormone treatments. If cells in
which the actin filaments were disrupted by cytochalasin D treatment
were exposed to cycloheximide at the same time as hormones and/or
(Bu)2cAMP addition, the IGFBP-1 mRNA levels remained below
the limits of detection. This suggests that de novo protein
synthesis is required for IGFBP-1 mRNA to be expressed in response to
hormones and/or (Bu)2cAMP.
Physiological priming in vivo promotes IGFBP-1 induction in
vitro
Our data show that IGFBP-1 is induced in response to hormones and
(Bu)2cAMP in stromal cells isolated from nonpregnant
baboons within 24–48 h after the disruption of the cytoskeleton. We
hypothesized that in response to pregnancy or simulated pregnancy,
stromal cells are modulated in vivo, which allows for the
expression of IGFBP-1 in vitro. Stromal cells from early
pregnant and simulated pregnant (long-term hCG treatment) baboons were
isolated and grown to 80% confluency. They were then treated with
(Bu)2cAMP alone, hormones alone, and hormones plus
(Bu)2cAMP. Control cells were treated with media
alone. Control cells from pregnant baboons expressed low levels of
IGFBP-1 (Fig. 6). Within 48 h, cells
that were treated with (Bu)2cAMP alone, hormones alone, and
hormones plus (Bu)2cAMP expressed IGFBP-1. Cycloheximide
treatment inhibited IGFBP-1 expression, implicating the involvement of
an intermediate proteinaceous factor(s). Stromal cells isolated from
long-term hCG-treated baboons also expressed IGFBP-1 mRNA and protein
in response to (Bu)2cAMP, hormones, and hormones plus
(Bu)2cAMP (Fig. 7).
Cycloheximide inhibited IGFBP-1 expression in all treatment groups. In
addition, the absence of measurable IGFBP-1 protein in the conditioned
media (Figs. 6A and 7A) also indicates that cyclohexamide was effective
in blocking any additional protein synthesis downstream of the
transcriptional response to (Bu)2cAMP. It is interesting to
note that in both pregnant and hCG-treated baboons, the stromal cells
produced more IGFBP-1 in response to hormones alone than in response to
(Bu)2cAMP alone. In cytochalasin D-treated cells from
nonpregnant baboons, IGFBP-1 production was greater with
(Bu)2cAMP treat-ment alone than with hormones alone.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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SMA (13). In this study we demonstrated
that IGFBP-1 can be induced by (Bu)2cAMP within 24–48 h
after the disruption of the cytoskeleton suggesting that the presence
of actin inhibits IGFBP-1 gene expression. This was shown by both
pharmacologically disrupting the cytoskeleton in vitro and
by activating stromal cells isolated during pregnancy or hormonally
simulated pregnancy that are expressing SMA in vivo.
Furthermore, we showed that the expression of IGFBP-1 under these
experimental conditions requires the synthesis of an intermediary
protein(s).
Decidualization in the baboon requires the presence of the conceptus
(6). Furthermore, stromal cells isolated from a receptive baboon
endometrium require at least 12–17 days of continuous hormone
(estradiol, MPA, relaxin) and (Bu)2cAMP treatment to
produce significant levels of IGFBP-1 (13). What happens within
these cells in response to hormones over such an extended time span
remains an enigma. Here, we showed that the disruption of the actin
filaments or microtubules with cytochalasin D or nocodazole,
respectively, increased the level of IGFBP-1 expression in response to
(Bu)2cAMP. The role of the cytoskeleton in regulating gene
expression has been reported by other investigators. Carbajal and
Vitale (21) suggested that the cortical actin cytoskeleton of cultured
lactotropes is involved in the control of PRL secretion. Local
dismantling of the cortical actin network permits the excluded granules
to reach the plasma membrane for exocytosis. Tomasek et al.
(15) demonstrated that disruption of the cytoskeleton by cytochalasin D
in fibroblasts dramatically increased gelatinase A activity, a matrix
metalloproteinase involved in both connective tissue remodeling and
tumor invasion. Nocodazole treatment, however, did not promote
gelatinase A activation. Disruption of the cytoskeleton has also been
shown to induce transcription of the c-fos gene within 15
min of cytochalasin D treatment (22). Whether the disruption of the
cytoskeleton using pharmacological agents and the events that follow
mirrors normal physiological processes associated with decidualization
is not known at this time. The association of the cytoskeleton with
IGFBP-1 gene regulation is possible, given that the cytoskeleton is
important in cell growth, changes in cell shape, regulation of protein
secretion, and cell signaling (9). Furthermore, SMA, a cytoskeletal
actin protein that is induced in predecidualizing baboon
endometrial stromal cells disappears when the cells express IGFBP-1 (6, 8).
Baboon endometrial stromal cells in culture require continuous exposure to hormones and (Bu)2cAMP for 6 days before detectable levels of IGFBP-1 are observed (13). Disruption of the actin filaments and microtubules promoted IGFBP-1 expression within 24 h of hormone and (Bu)2cAMP treatment. Assuming that (Bu)2cAMP is acting on protein kinase A (PKA) in baboon stromal cells, as has been shown in human endometrial stromal cells (23), it is possible that the cytoskeleton inhibits PKA from acting on target molecules. Lester et al. (24) demonstrated that the hormone, glucagon-like peptide 1, induces insulin secretion from pancreatic cells via the cAMP-signaling pathway and that the correct subcellular location of PKA was necessary for this process. The selectivity of PKA action has been attributed to proteins that bind and anchor PKA to specific subcellular structures, termed A-kinase anchor proteins (AKAPs) (reviewed in Ref. 25). In neuronal and nonneuronal cells, AKAPs are associated with the cytoskeleton (26, 27). Perhaps the anchoring of PKA through AKAPs to the correct subcellular location or the release of PKA from the cytoskeletal complex is important in the cAMP-signaling pathway for the regulation of IGFBP-1 expression.
The mechanism of induction of the IGFBP-1 gene by (Bu)2cAMP
is not known. Telgmann et al. (23) demonstrated that the PRL
promoter, when transfected into human endometrial stromal cells, is
activated by cAMP in two steps. There is an initial weak induction
after 12 h of stimulation and a subsequent, more pronounced
induction. While the first induction depended on the cAMP-response
element (CRE), the second induction was not driven by the CRE.
They proposed that an intermediate endometrial stromal cell-specific
factor(s) was involved in inducing the second major transcriptional
response of the PRL promoter. In our study, we demonstrated that
inhibition of de novo protein synthesis by cycloheximide
inhibits the expression of IGFBP-1 in response to
hormone/(Bu)2cAMP treatments. This was shown in both the
cytochalasin D- treated cells and in cells from pregnant and simulated
pregnant baboons. It is possible that cAMP is required to induce an
intermediary protein, acting as a transcription factor(s) either
directly or indirectly on the IGFBP-1 promoter to regulate its
expression. It has been demonstrated that hepatocyte nuclear
factor-1 and the glucocorticoid receptor synergistically
activate transcription of the IGFBP-1 gene in the rat (28). The Sp3
protein, found in human decidual cells, has been implicated in the
transcriptional regulation of IGFBP-1 by acting on distal promoter
regions [
-2.6 kb (29)]. Finally, given that cAMP induces IGFBP-1
expression in our system, it is possible that the transcription factor
CREB (CRE-binding protein) may be the required protein that is
synthesized. However, Gellersen et al. (30) demonstrated
that CREB was equally expressed in both nondecidualized and in
decidualized human endometrial stromal cells. Furthermore,
Mukherjee et al. (31) demonstrated that in the rat ovary,
CREB mRNA and protein levels change only minimally in response to
gonadotropins but that the phosphorylation of preexisting CREB protein
on serine 133 is regulated by gonadotropins. It is possible that
although CREB appears to be fairly ubiquitously expressed in a number
of cell systems, its regulation by other molecules is necessary for
activating gene expression through the CRE. We are currently
investigating which protein(s) is involved in activating the
IGFBP-1 gene in baboon stromal cells during decidualization.
Finally, it was interesting to note a difference in the pattern of
IGFBP-1 expression in response to hormones/(Bu)2cAMP
treatment in cells with disrupted actin filaments vs. cells
from pregnant or simulated pregnant animals. Cytochalasin D-treated
cells exhibited significantly elevated expression of IGFBP-1 in
response to (Bu)2cAMP only (P 0.05)
compared with controls. IGFBP-1 expression was higher in these cells
than when cells were treated with hormones alone. Alternatively, cells
from pregnant or simulated pregnant animals expressed higher levels of
IGFBP-1 in response to hormones alone than (Bu)2cAMP alone.
This observation suggests that the events involved with IGFBP-1 gene
regulation in cytochalasin D-treated cells are not identical to that of
the in vivo primed cells. However, both groups of cells did
require de novo protein synthesis for the expression
of IGFBP-1. We have previously shown that IGFBP-1 is hormonally
regulated in glandular epithelial cells (17). IGFBP-1 staining was
evident in the deep basal glands of the baboon endometrium at day 10
post ovulation and increased thereafter (17). In stromal cells, IGFBP-1
staining is absent throughout the menstrual cycle. However, as shown in
this report, cells taken from an early pregnant or simulated
pregnant animal expressed IGFBP-1 in response to hormones only. It is
possible that in response to an embryonic signal(s), stromal cell
physiology changes, allowing steroids to increase the expression of the
IGFBP-1 gene. Alternatively, cytochalasin D-treated cells have not been
exposed to the embryonic signal and thus are not physiologically
identical to cells that have seen this signal. IGFBP-1 expression in
cytochalasin D-treated cells after (Bu)2cAMP exposure may
be a response that provides possible clues toward the mechanisms
associated with the structural differentiation of the endometrial
stromal cell. Perhaps in vivo, the factors associated with
pregnancy are conducive to the restructuring of the cytoskeleton, which
in turn potentiate stromal cells to induce IGFBP-1 in response to the
appropriate stimulus. Moreover, long-term hormone/cAMP treatment
in vitro of stromal cells from a nonpregnant animal may
alter the cytoskeletal arrangement, which then promotes IGFBP-1
expression in response to hormones and/or (Bu)2cAMP
in vitro. It has been shown, in mouse endometrial stromal
cells, that stress fibers or bundles of microfilaments that run
parallel to the long axis of the cell become shorter and thicker,
running in many different orientations and concentrating at the
periphery with stromal cell differentiation (32). Furthermore, Babiarz
et al. (32) have demonstrated parallel remodeling of the
extracellular matrix with changes in cell morphology, both of which
occur during the decidualization process in vivo.
In summary, it is apparent that IGFBP-1, a marker for decidualizing cells, can be regulated by altering the cytoskeleton and by exposing the cells to a pregnant or simulated pregnant environment. The investigation of the association of the cytoskeleton with IGFBP-1 gene regulation is a novel approach to identifying the biochemical and molecular events involved in the decidualization process.
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Acknowledgments |
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Footnotes |
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Received June 5, 1998.
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References |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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1-globulin
(1-PEG), in decidua of the baboon (Papio anubis)
placenta. Biol Reprod 40:873–885[Abstract]
-subunit functions synergistically with
progesterone to stimulate differentiation of cultured human endometrial
stromal cells to decidualized cells: a novel role for free -subunit
in reproduction. Endocrinology 137:1332–1339[Abstract]
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