| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
Short Communication |




From the Departments of Obstetrics and
Gynecology*
and Molecular
Pathology,
University of Tuebingen, Tuebingen,
Germany; and the Center for Reproductive
Sciences,
University of California, San
Francisco, California
| Abstract |
|---|
|
|
|---|
showed this cytokine to be
localized to stromal and epithelial compartments of the endometriotic
implant with weak staining in unaffected ovarian tissue. Subconfluent
monolayers of endometriotic stromal cells were tested for RANTES gene
expression in situ, but we could only detect
RANTES mRNA in isolated stromal cells after treatment with TNF-
. No
RANTES mRNA was observed in unstimulated stromal cells or TNF-
stimulated or unstimulated epithelial cells. The data are consistent
with a model in which proinflammatory cytokines (eg, TNF-
)
induce RANTES gene expression limited to specific cells within
endometrial and endometriotic stroma. Production of this
chemokine, in turn, stimulates recruitment of
CD68-positive macrophages into these tissues.
| Introduction |
|---|
|
|
|---|
Resident leukocytes within the stroma of endometriotic lesions have been characterized histologically.5,6 As noted in the surrounding pelvic fluid, endometriotic implants predominantly contain macrophages and T cells, and eosinophils have been reported recently.7 We and others have proposed that recruitment of leukocytes to the vicinity of endometriotic lesions is mediated by specific chemokines synthesized by cells within the implants. Leukocyte chemoattractants, such as monocyte chemotactic protein-1 (MCP-1),8,9 vascular endothelial growth factor,10,11 interleukin-8,12-14 and eotaxin15 are expressed in endometriotic implants. Because of the phenotypic inflammatory exudate of endometriosis, we studied the expression of regulated on activation, normal T cell expressed and secreted (RANTES), a ß-chemokine selective for macrophage and T-cell recruitment. RANTES protein was identified immunohistochemically in stromal cells of normal endometrium and ectopic implants16 and could be detected in high concentrations in peritoneal fluid of women with endometriosis.4 The current experiments were designed to verify RANTES synthesis within the endometrium and endometriotic implants and to identify which cells were responsible for RANTES gene expression. In situ mRNA hybridization, combined with immunohistochemistry to localize specific cell types within the implants, was used to achieve this objective. The findings support our hypothesis that local cytokine networks regulate RANTES gene expression and the attraction of macrophages and T cells into eutopic and ectopic endometrium.
| Materials and Methods |
|---|
|
|
|---|
Healthy ovulatory women, who had not received hormones or GnRH agonist therapy for at least 6 months before surgery, were recruited after they had provided written informed consent under a study protocol approved by the Committee on Human Research at the University of California, San Francisco. Women with ovarian endometriomata (n = 8) were identified laparoscopically and staged according to a modification of the revised American Fertility Society system.12 Controls also were evaluated by laparoscopy and were women with subserosal leiomyomata or without pelvic pathology (n = 11).
Sources of Tissues
Tissue specimens were obtained at the time of laparoscopy, which was scheduled during the mid-proliferative phase of the cycle. Endometrial and endometriosis biopsies were collected under sterile conditions and prepared for histochemistry or cell culture, as described previously.16
Preparation of Hybridization Probes
For in situ hybridization, 202-bp RANTES cDNA templates
were synthesized by polymerase chain reaction, having engineered T7 RNA
polymerase-binding site sequences 5' to the antisense oligomers for the
gene products (Table 1)
. Run-off
transcripts were synthesized by incubation of T7 RNA polymerase with
35S-UTP and unlabeled rNTPs as described
previously.17
|
Endometrial and endometrioma tissues were fixed for 24 hours in
2% paraformaldehyde and 0.5% glutaraldehyde, paraffin-embedded, cut
in serial sections of 5 µm, and stained using the Vectastain Elite
ABC kit (Vector Laboratories, Burlingame, CA). Immunoperoxidase
staining was performed overnight at 4°C, using mouse monoclonal IgG
antibodies against human cytokeratin-18 (1:2000 dilution; Sigma, St.
Louis, MO), human CD-68 (dilution 1:100; DAKO Corp., Carpinteria, CA),
human RANTES (dilution 1:100; R&D Systems, Minneapolis, MN), or TNF-
(dilution 1:100, R&D Systems). Controls for the immunostaining
specificity of TNF-
included sections stained with anti-TNF-
antibodies immunoabsorbed with 10 µg/ml of recombinant human TNF-
(R&D Systems). Diaminobenzidine (Zymed, South San Francisco, CA) was
used as the chromagen. All sections also were lightly counterstained
with hematoxylin.
In Situ Hybridization of Tissue Sections
For detection of RANTES mRNA, paraffin-embedded endometriotic and endometrial specimens were dewaxed and hybridized as described previously.17,18 After pretreatment with proteinase K (1 µg/ml), serial tissue sections were incubated in a hybridization mixture containing the 35S-labeled RANTES antisense RNA probe (500 ng/ml) or RANTES sense RNA control probe (500 ng/ml) in 10 mmol/L Tris-HCl, pH 7.4, 50% (v/v) deionized formamide, 600 mmol/L NaCl, 1 mmol/L ethylenediaminetetraacetic acid, 0.02% polyvinylpyrrolidone, 0.02% Ficoll, 0.05% bovine serum albumin, 10% dextran sulfate, 10 mmol/L dithiothreitol, 200 µg/ml denatured sonicated salmon sperm DNA, and 100 µg/ml rabbit liver tRNA. Hybridization was performed overnight at 42°C. After hybridization, tissue sections were washed as described previously.17 Nonhybridized single-stranded RNA probes were digested by RNase A (20 µg/ml) in 10 mmol/L of Tris-HCl (pH 8.0)/0.5 mol/L NaCl for 30 minutes at 37°C. For autoradiography, slides were dipped in Kodak NTB-2 nuclear track emulsion (Integra Biosciences, Inc., Woburn, MA). After exposure for 4 weeks at 4°C, slides were developed and counterstained with hematoxylin and eosin.
Human Endometrial and Endometriosis Cell Cultures
Primary endometrial and endometriotic cell cultures were prepared from biopsies as described previously.16 Glandular epithelial cells were separated from stromal cells and debris by filtration through narrow gauge sieves. Stromal cells were subcultured twice to eliminate contamination by macrophages or other leukocytes. Extensive characterization of cell cultures prepared using this protocol confirmed that they were >95% pure and retained functional markers of their endometrial and endometriotic origin in vivo.12
Preparation of Cells for in Situ Hybridization
Endometriotic stromal and epithelial cells were plated onto
Lab-Tek four-chamber slides (NUNC, Rochester, NY). The complete
medium was removed and replaced with fresh minimal essential
medium-
containing 2.5% fetal calf serum and antibiotics and
the cells were cultured for 48 hours in the absence or presence of
TNF-
(100 ng/ml, Sigma Chemical Co.), and fixed in 95% ethanol.
In situ hybridization was performed as described above.
| Results |
|---|
|
|
|---|
In situ hybridization was used to localize RANTES mRNA
in fixed tissues. A section of normal mid-proliferative endometrium is
shown in Figure 1A
. RANTES gene
expression could be detected in the stromal compartment adjacent to
epithelial glands, but the glands themselves did not contain any RANTES
message. No specific autoradiographic signals were observed when serial
endometrial tissue sections were hybridized with the RANTES sense
RNA-control probe (Figure 1B)
. Similar results were observed in 8 of 11
normal endometrial biopsies. Endometriotic implants of the ovary also
showed RANTES mRNA in the stromal compartment indicated by black arrows
and white arrows. The epithelial cell lining subjacent to the stroma
and the unaffected ovarian stroma (top) did not contain RANTES mRNA
(Figure 1C)
. No specific autoradiographic signals were observed when
the endometriotic tissue sections were hybridized with the RANTES sense
RNA-control probe (Figure 1D)
. Similar results were observed in seven
of eight endometriotic sections.
|
showed that this
cytokine was diffusely present in both stromal and epithelial
compartments of the endometriotic implant. Regions of the ovary
uninvolved with endometriosis showed less intense TNF-
immunostaining (Figure 1G)
antibodies
immunoabsorbed with excess TNF-
protein (Figure 1H)RANTES in Situ Hybridization in Purified Endometrial Cell Populations
Isolated endometriotic stromal and epithelial cells were examined
subsequently for RANTES mRNA expression by in situ
hybridization. Subconfluent monolayers of endometriotic stromal cells
were cultured for 48 hours. No RANTES mRNA was detectable under
conditions in which the medium contained no added cytokine (Figure 2A)
. After culturing the cells in the
presence of TNF-
(100 ng/ml) for 48 hours (Figure 2B)
, RANTES mRNA
was identified in 10 to 20% of the stromal cells. No
specific autoradiographic signals were observed when TNF-
-stimulated
endometriotic stromal cells were hybridized with the RANTES sense
RNA-control probe (Figure 2C)
. Subconfluent monolayers of endometriotic
epithelial cells also did not reveal evidence of RANTES mRNA
expression, even after 48 hours of cytokine stimulation (Figure 2D)
.
|
| Discussion |
|---|
|
|
|---|
and ß. These chemokines are
ligands with variable affinities for the receptors CCR1 to CCR5, which
are expressed on the surface of responsive immune cells.19
As the predominant leukocytes within peritoneal fluid1
and
ectopic implants5
of women with endometriosis include
macrophages and T cells, our laboratory has focused on the expression
of one chemokine, RANTES, with activity for both cell types. RANTES
originally was isolated as a cDNA from CD8+ T cells20
that
encodes an 8-kd secreted chemokine protein. Expression of RANTES can be
induced within hours of stimulation by proinflammatory stimuli, such as
TNF-
.21
In the current study we found that RANTES mRNA was localized to stroma,
consistent with protein localization and in vitro expression
in isolated endometrial cells.16
CD68-positive macrophages
were co-localized with RANTES mRNA-expressing stromal cells (black
arrows, Figure 1C
), however, some RANTES mRNA-positive stromal regions
(white arrows, Figure 1C
) were devoid of macrophages. A plausible
interpretation of this observation is that CD68-positive macrophages
are recruited to areas of stromal RANTES expression. The distribution
of TNF-
protein in endometriosis implants is very similar to that
described in the functionalis region of normal eutopic
endometrium.22
Our in situ hybridization data indicated that RANTES
mRNA-positive stromal cells were in proximity to TNF-
-positive
epithelial and stromal cells. This observation suggested that the
latter cells are potential paracrine or autocrine sources,
respectively, of cytokines that stimulate RANTES mRNA production in
endometrial and endometriotic stroma. Endometrial expression of TNF-
mRNA is increased in the late secretory phase and during
endometrial bleeding.23
This is consistent with our
observation that normal endometrial RANTES mRNA concentrations, as
determined by solution hybridization experiments, were highest in the
secretory phase.16
However, our immunohistochemistry
analyses were not sensitive or quantitative enough to verify this
finding.16
To optimize reproducibility we limited the
current study to proliferative phase sampling of normal and
endometriosis biopsies, which precluded further analysis of the effects
of ovulatory cycle stage and endocrine milieu on RANTES expression. Our
group previously investigated the effects of 10 nmol/L of
17ß-estradiol on RANTES secretion by endometrial and endometriosis
stromal cells in vitro, but we observed no stimulatory
action.24
Recently, however, Akoum and
colleagues25
studying the related MCP-1 chemokine in mixed
endometriotic cell cultures, observed that 10 nmol/L of estradiol
increased interleukin-1ß-induced MCP-1 mRNA production by 200% and
protein secretion by 65%. They suggested that the effects of estradiol
on MCP-1 expression are indirectly mediated via enhanced cytokine
sensitivity.
Our in vitro findings (Figure 2B)
suggest that a
subpopulation of endometriotic stromal cells is responsible for RANTES
mRNA expression. This result was unanticipated based on total RNA from
solubilized stromal cell cultures16
and differs from the
apparently more generalized distribution of RANTES protein. This
observation is of interest given the recent appreciation of
heterogeneity among mesenchymal cells in certain tissues. The emergence
of a discrete subpopulation of stromal cells may occur during
endometriotic differentiation as has been described for presumed stem
cells within bone marrow stroma.26
Current studies in the
laboratory are directed to characterize the subset of endometriotic
stromal cells responsible for robust synthesis of RANTES gene
transcripts.
In summary, this study confirmed that cells within the eutopic and
ectopic endometrial stroma are the sites of RANTES mRNA transcription.
A combination of in situ hybridization and
immunohistochemistry in tissue specimens, coupled with primary
endometriotic cell cultures, was used. The findings support the
hypothesis that TNF-
, produced by endometriotic implant epithelial
and/or stromal cells, can induce expression of RANTES mRNA in a subset
of endometriotic stromal cells. These cells, in turn, synthesize RANTES
protein, which serves to recruit the accumulation of CD68-expressing
macrophages into the endometriotic lesion. We postulate that the
inflammatory environment created by this cascade contributes to the
clinical symptoms that typify endometriosis.
| Acknowledgements |
|---|
| Footnotes |
|---|
Supported by Fortune-Project F1241133, the Deutsche Forschungs-gemeinschaft (to D. H.), and a grant from the National Institutes of Health/National Institute of Child Health and Human Development, through cooperative agreement U54-HD37321, as part of the Specialized Cooperative Centers Program in Reproduction Research (to D. H. and R. N. T.).
Accepted for publication March 9, 2001.
| References |
|---|
|
|
|---|
messenger ribonucleic acid and protein in human endometrium. Biol Reprod 1992, 47:141-147[Abstract]
mRNA expression in endometrial cells by TNF-
and by oestrogen withdrawal. Mol Hum Reprod 1999, 5:1141-1149This article has been cited by other articles:
![]() |
G. Weiss, L. T. Goldsmith, R. N. Taylor, D. Bellet, and H. S. Taylor Inflammation in Reproductive Disorders Reproductive Sciences, February 1, 2009; 16(2): 216 - 229. [Abstract] [PDF] |
||||
![]() |
L. Fraccaroli, J. Alfieri, L. Larocca, M. Calafat, G. Mor, C. P. Leiros, and R. Ramhorst A potential tolerogenic immune mechanism in a trophoblast cell line through the activation of chemokine-induced T cell death and regulatory T cell modulation Hum. Reprod., January 1, 2009; 24(1): 166 - 175. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. L. Hull, C. R. Escareno, J. M. Godsland, J. R. Doig, C. M. Johnson, S. C. Phillips, S. K. Smith, S. Tavare, C. G. Print, and D. S. Charnock-Jones Endometrial-Peritoneal Interactions during Endometriotic Lesion Establishment Am. J. Pathol., September 1, 2008; 173(3): 700 - 715. [Abstract] [Full Text] [PDF] |
||||
![]() |
T. L. Thirkill, H. Vedagiri, and G. C. Douglas Macaque Trophoblast Migration toward RANTES Is Inhibited by Cigarette Smoke-Conditioned Medium Toxicol. Sci., June 1, 2006; 91(2): 557 - 567. [Abstract] [Full Text] [PDF] |
||||
![]() |
A. Akoum, A. Lemay, and R. Maheux Estradiol and Interleukin-1{beta} Exert a Synergistic Stimulatory Effect on the Expression of the Chemokine Regulated upon Activation, Normal T Cell Expressed, and Secreted in Endometriotic Cells J. Clin. Endocrinol. Metab., December 1, 2002; 87(12): 5785 - 5792. [Abstract] [Full Text] [PDF] |
||||
![]() |
D. Zhao, E. A. Pritts, V. A. Chao, J.-F. Savouret, and R. N. Taylor Dioxin stimulates RANTES expression in an in-vitro model of endometriosis Mol. Hum. Reprod., September 1, 2002; 8(9): 849 - 854. [Abstract] [Full Text] [PDF] |
||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |