Role of endocrine status and cell type in adhesion of human endometrial cells to the peritoneum in nude mice

LncRNA MEG3-210 regulates endometrial stromal cells migration, invasion and apoptosis through p38 MAPK and PKA/SERCA2 signalling via interaction with Galectin-1 in endometriosis

BACKGROUND

Endometriosis is a benign gynaecological disease with malignant characteristics that severely affects women's quality of life. Long noncoding RNA maternally expressed gene 3 (LncRNA MEG3) is a tumour suppressor that is downregulated in various cancer cells and tissues, and regulates multiple biological processes. Emerging studies have revealed that the interactions between MEG3 and proteins are involved in disease progression. Galectin-1 affects cell motility, signal transduction and vascularization, and is overexpressed in endometriosis. Our study is the first to explore the role of MEG3-210 transcript in endometriosis and to reveal the regulatory mechanism mediated by the interaction between MEG3-210 and Galectin-1.

MATERIALS AND METHODS

Endometrial tissues and sera from patients with endometriosis and controls were collected. qRT-PCR was performed to detect the expression of MEG3-210 in the endometrium and endometrial stromal cells (ESCs). The CCK-8 assay, the Transwell assay, flow cytometry and animal models were conducted to evaluate the functions of MEG3-210 in vitro and in vivo. Bioinformatic analysis, Western blot assays, RNA-pull down assays and RNA immunoprecipitation were used to explore the potential mechanism of MEG3-210 in endometriosis.

RESULTS

Our results showed that MEG3-210 expression was lower in the eutopic endometrium of women with endometriosis. MEG3-210 downregulation promoted ESCs migration, invasion, anti-apoptosis in vitro and growth of endometriotic lesions in vivo. Furthermore, MEG3-210 downregulation could activate p38 mitogen-activated protein kinase (p38 MAPK) and inhibit cAMP-dependent protein kinase A/sarcoplasmic reticulum Ca²⁺ ATPase 2 (PKA/SERCA2) signalling, which was mediated by Galectin-1. The protein levels of Galectin-1 in patients with endometriosis were elevated, and Galectin-1 siRNA could reduce the size of lesions.

CONCLUSION

MEG3-210 regulates ESCs through p38 MAPK and PKA/SERCA signalling via interaction with Galectin-1. The novel regulatory mechanism may provide new insights into drug therapy and the diagnosis of endometriosis.

Animal Models in Endometriosis Research

The initiation of endometriosis in women is difficult to investigate, because there is usually a delay of several years from the onset of lesion development to the clinical diagnosis. Animal models of endometriosis, on the other hand, provide an important contribution to the investigation of the disease pathogenesis and the efficacy of therapeutic intervention strategies.

Establishment of long-term model throughout regular menstrual cycles in immunodeficient mice

PROBLEM

The number of uterus natural killer (NK) cells change through the menstrual cycle, but the origin of uterus NK cell was not unclear. Our aims are to study whether we can reproduce repetition of menstrual cycle and to reveal the origin of uterus NK cells.

METHOD OF STUDY

Endometrial samples were obtained from fertile women, and the tissues were transplanted into ovariectomized non-obese diabetic (NOD)/severe combined immunodeficiency (SCID)/γCnull (NOG) mice. Mice were treated with sex hormones which were in accord with human menstrual cycle.

RESULTS

The replants showed similar histological changes as in eutopic endometrium repeatedly. CD56-positive, CD16-negative NK cells increased significantly during the treatment with estradiol and progesterone combination.

CONCLUSION

Histological assessment demonstrated that this model of NOG mice repeatedly exhibited regular menstrual cycles, and this model mimicked not 'ectopic endometrium', but 'eutopic endometrium' in humans. Change in number of NK cells suggested that NK cell might be derived from the endometrium.

Comprehensive analysis of leukocytes, vascularization and matrix metalloproteinases in human menstrual xenograft model

In our previous study, menstrual-like changes in mouse were provoked through the pharmacologic withdrawal of progesterone with mifepristone following induction of decidualization. However, mouse is not a natural menstruation animal, and the menstruation model using external stimuli may not truly reflect the occurrence and development of the human menstrual process. Therefore, we established a model of menstruation based on human endometrial xenotransplantation. In this model, human endometrial tissues were transplanted subcutaneously into SCID mice that were ovarectomized and supplemented with estrogen and progestogen by silastic implants with a scheme imitating the endocrinological milieu of human menstrual cycle. Morphology, hormone levels, and expression of vimentin and cytokeratin markers were evaluated to confirm the menstrual-like changes in this model. With 28 days of hormone treatment, transplanted human endometrium survived and underwent proliferation, differentiation and disintegration, similar to human endometrium in vivo. Human CD45+ cells showed a peak of increase 28 days post-transplantation. Three days after progesterone withdrawal, mouse CD45+ cells increased rapidly in number and were significantly greater than human CD45+ cell counts. Mouse CD31+ blood vascular-like structures were detected in both transplanted and host tissues. After progesterone withdrawal, the expression levels of matrix metalloproteinases (MMP) 1, 2, and 9 were increased. In summary, we successfully established a human endometrial xenotransplantation model in SCID mice, based on the results of menstrual-like changes in which MMP-1, 2 and 9 are involved. We showed that leukocytes are originated from in situ proliferation in human xenografts and involved in the occurrence of menstruation. This model will help to further understand the occurrence, growth, and differentiation of the endometrium and the underlying mechanisms of menstruation.

Inhibition of transcription, expression, and secretion of the vascular epithelial growth factor in human epithelial endometriotic cells by romidepsin

OBJECTIVE

To investigate whether the histone deacetylase (HDAC) inhibitor romidepsin down-regulates VEGF (vascular endothelial growth factor) gene expression and abrogates VEGF protein secretion in human epithelial endometriotic cells.

DESIGN

In vitro study with human immortalized epithelial endometriotic cells.

SETTING

University hospital.

PATIENT(S)

Not applicable.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Real-time reverse-transcriptase polymerase chain reaction to evaluate VEGF gene expression, immunoblot analysis to evaluate protein expression, and enzyme-linked immunosorbent assay to evaluate VEGF protein secretion into the culture medium.

RESULT(S)

Treatment of 11z human endometriotic cells with romidepsin statistically significantly inhibited VEGF gene transcription and down-regulated VEGF protein expression. Moreover, romidepsin abrogated the secretion of VEGF protein into the culture medium. Romidepsin also reduced the expression of hypoxia-inducible factor-1α (HIF-1α), which is implicated in the transcription of the VEGF gene, in cobalt chloride-pretreated (to mimic hypoxic conditions) 11z cultures.

CONCLUSION(S)

Romidepsin targets VEGF at the transcriptional level, which subsequently leads to the reduction of secreted VEGF (the "active" form of VEGF). Therefore, romidepsin may be a potential therapeutic candidate against angiogenesis in endometriosis.

Estrous cycle modulates ovarian carcinoma growth

PURPOSE

The effects of reproductive hormones on ovarian cancer growth are not well understood. Here, we examined the effects of estrous cycle variation and specific reproductive hormones on ovarian cancer growth.

EXPERIMENTAL DESIGN

We investigated the role of reproductive hormones in ovarian cancer growth using both in vivo and in vitro models of tumor growth.

RESULTS

In vivo experiments using the HeyA8 and SKOV3ip1 ovarian cancer models showed that tumor cell inoculation during proestrus significantly increased tumor burden (251-273%) compared with injection during the estrus phase. Treatment of ovariectomized mice with 17beta-estradiol resulted in a 404% to 483% increase in tumor growth compared with controls. Progestins had no significant effect, but did block estrogen-stimulated tumor growth. Tumors collected from mice sacrificed during proestrus showed increased levels of vascular endothelial growth factor (VEGF) and microvessel density compared with mice injected during estrus. HeyA8, SKOV3ip1, and mouse endothelial (MOEC) cells expressed estrogen receptor alpha and beta and progesterone receptor at the protein and mRNA levels, whereas 2774 ovarian cancer cells were estrogen receptor-negative. In vitro assays showed that 17beta-estradiol significantly increased ovarian cancer cell adhesion to collagen in estrogen receptor-positive, but not in estrogen receptor-negative cells. Additionally, 17beta-estradiol increased the migratory potential of MOEC cells, which was abrogated by the mitogen-activated protein kinase (MAPK) inhibitor, PD 09859. Treatment with 17beta-estradiol activated MAPK in MOEC cells, but not in HeyA8 or SKOV3ip1 cells.

CONCLUSION

Our data suggest that estrogen may promote in vivo ovarian cancer growth, both directly and indirectly, by making the tumor microenvironment more conducive for cancer growth.

Induction of peritoneal endometriosis in nude mice with use of human immortalized endometriosis epithelial and stromal cells: a potential experimental tool to study molecular pathogenesis of endometriosis in humans

OBJECTIVE

To determine whether a mixed population of immortalized human endometriosis epithelial and stromal cells is able to induce peritoneal endometriosis in nude mice.

DESIGN

Prospective experimental study. Human immortalized endometriosis epithelial and stromal cells were xenografted into ovariectomized nude mice. Macroscopically, the number of induced endometriosis-like lesions and their color were determined. Microscopically, histomorphology of endometriosis glands and their structure were analyzed, and comparisons were made with tissue from spontaneous endometriosis in women.

SETTING

College of Veterinary Medicine and Biomedical Sciences, Texas A&M University.

ANIMALS

Seven ovariectomized nude mice.

INTERVENTION(S)

Minimal invasive procedures were performed to administer estrogen pellets and transplant immortalized human endometriosis epithelial and stromal cells into nude mice.

MAIN OUTCOME MEASURE(S)

Peritoneal endometriosis-like lesions induced in nude mice were characterized and compared with spontaneous peritoneal endometriosis in women.

RESULT(S)

Xenografts of human immortalized endometriosis epithelial and stromal cells into the peritoneal cavity of the recipient nude mice are able to proliferate, attach, invade, reorganize, and establish peritoneal endometriosis. Endometriosis glands at different stages of growth were present in induced endometriosis-like lesions. Proliferating cell nuclear antigen, metalloproteinase 2, estrogen receptor-alpha, cyclooxygenase-2, and prostaglandin E(2) receptors EP2 and EP4 proteins were expressed in both endometriosis glandular epithelial and stromal cells of the induced endometriosis-like lesions.

CONCLUSION(S)

This xenograft model could be used as a potential experimental tool to understand the molecular and cellular aspects of the pathogenesis of endometriosis in humans.

Evaluation of the macroscopic growth degree of experimental endometriosis in rats

PURPOSE

To evaluate macroscopically the growth degree of self-transplantation of endometriosis in rats.

METHODS

Forty female rats, after a 7-day period for adpating and evaluating of the estrous cycle regularity, underwent tail abdominal midline laparotomy with 3-cm cuts. The average third of the left uterine horn was removed, 4mm x 4mm patches in liquid environment were made, and self-transplanted in the rat mesenterium with a single stitch, and the endometrial surface of the endometriotic implant facing the lumen of the peritoneal cavity. The rats were programmed to die after three weeks. The abdominal cavity displaying was held and self-transplants were identified and classified.

RESULTS

The results achieved were: one case for degree 0 (2,5%), three cases for degree 1 (7,5%), eleven cases for degree II (27,5%) and twenty-five cases for degree III (62,5%).

CONCLUSION

The experimental endometriosis development, through the self-transplantation technique, showed to be most common in degrees 3 and 2 of development.

[Pathogenesis of endometriosis]

Endometriosis, defined by the development of endometrial tissue outside the uterus, is a benign disease responsible for infertility and pelvic pain. The diagnosis based on a detailed gynecological history and a careful clinical examination should be done as early as possible in order to treat patients correctly. Medical treatment is not appropriate in all cases and surgical treatment should be proposed but morbidity is related to the severity of the lesion. Ectopic implantation of endometrial cells needs complex interactions between host tissue and epithelial endometrial cells. The conditions for the development of endometriosis are estrogeno-dependent growth of endometrial cells, induction of angiogenesis and lymphangiogenesis. Principal cellular and molecular factors of angiogenesis, lymphangiogenesis and fibrosis should be identified in order to develop new therapeutic strategies of endometriosis.

Tyrosine receptor kinase B (TrkB) protein expression in the human endometrium

Tyrosine kinase receptor B (TrkB) gene expression, a neurotrophic factor receptor expressed in the brain and ovary, has recently been identified in deep infiltrating endometriosis by gene array. TrkB is thought to be important in resistance to anchorage independent apoptosis (ANOIKIS) and thus could be important in the pathogenesis of endometriosis. However, TrkB protein expression in the eutopic endometrium of women with and without endometriosis is unknown. Therefore, we examined TrKB protein expression in the endometrium by Western blot (n = 50) and immunohistochemistry (n = 17). Immunoblots of endometrial biopsies were prepared from women with endometriosis (n = 21) vs. healthy controls (n = 29) undergoing benign gynecological surgery at McMaster University Medical Centre. TrkB protein expression was significantly higher in immunoblots from women with endometriosis compared to women without endometriosis. In samples of archived paraffin-embedded endometrial tissue TrkB was localized to the cytoplasm of epithelial cells of the eutopic endometrium from women with endometriosis (n = 7) and without endometriosis (n = 10). We conclude that TrkB protein is expressed in human endometrium. Our results also suggest that TrkB expression may be greater in women with endometriosis compared to women without endometriosis.

Human endometrial epithelial cells (EEC) constitutively express more intercellular adhesion molecule (ICAM)-1 than endometrial stromal cells (ESC) in culture

PROBLEM

Intercellular adhesion molecule-1 (ICAM-1) is thought to play an important role in pathophysiological processes in endometrial tissue. The aim of this study was to quantify and compare the expression of ICAM-1 mRNA and protein in cultured endometrial epithelial cells (EEC) versus endometrial stromal cells (ESC).

METHOD OF STUDY

EEC and ESC were isolated from human endometrium and cultured. At confluency, ICAM-1 mRNA was measured by real-time reverse transcriptase-polymerase chain reaction, the membrane-bound form (mICAM-1) by immunocytodensitometry, and the soluble form (sICAM-1) by enzyme-linked immunosorbent assay.

RESULTS

At the transcriptional level, we observed a 1.7-fold increase in ICAM-1 expression in EEC versus ESC. mICAM-1 immunostaining in EEC [cell-relative membrane-bound signal-specific optical density (CR-M-SOD): 0.056 +/- 0.05] was stronger (P < 0.05) than in ESC (CR-M-SOD: 0.009 +/- 0.07). EEC were found to secrete more (P < 0.01) sICAM-1 ([sICAM-1] = 15.59 +/- 2.96 ng/mL) than ESC ([sICAM-1] = 5.14 +/- 2.61 ng/mL).

CONCLUSIONS

Cultured EEC constitutively express significantly more ICAM-1 mRNA and protein than ESC.

Animal models in endometriosis research

Endometriosis is a common gynaecological disease, defined as the presence of endometrial tissue outside the uterus, causing pelvic pain and subfertility in approximately 10% of women of reproductive age. Current therapies lead to pain relief, however, do not address the causes and entail severe side effects. Still little is known about the pathogenic processes leading to the development and maintenance of endometriosis. Because endometriosis occurs spontaneously only in humans and some non-human primates, animal models of induced endometriosis have been developed and are of high value for the evaluation of pathophysiological mechanisms underlying the development of this disease. These experimental models include the autotransplantation of uterine fragments into the peritoneal cavity of rodents and non-human primates or the heterotransplantation of human endometrial or endometriotic tissue to immunodeficient mice or onto the chicken chorioallantoic membrane (CAM). This review describes the animal models for endometriosis and assesses their different potentials and limitations in regard to endometriosis research, with the aim of developing novel non-invasive diagnostic tools and improved strategies for the treatment of endometriosis in women.

Quantification of endometriotic lesions in a murine model by fluorimetric and morphometric analyses

BACKGROUND

In animal models of endometriosis, the identification and quantification of lesions originating from human endometrium is often hampered by the small size of the implants and their embedding in murine tissue. The purpose of the present study was to develop two new methods of quantifying endometriosis-like lesions in a nude mouse model: fluorimetry and morphometry.

METHODS

Human menstrual endometrium was labelled using a fluorescent tracker, carboxyfluorescein diacetate, succinimidyl ester (CFDA-SE), and transplanted into the pelvic cavity of mice by injection through the peritoneum after performing a cutaneous incision. After 5 days, lesions were recovered by laparotomy. The fluorescence of the recovered endometriotic lesions was measured. Endometrial stroma and glands were immunostained in lesion sections with anti-CD10 and anti-CK22 antibodies, and their surface area was evaluated by morphometric analysis.

RESULTS

Fluorescent labelling allows identification of lesions not visible macroscopically. A good correlation was observed between fluorimetry and morphometry (r=0.88) applied for lesion quantification.

CONCLUSIONS

Fluorimetric evaluation combined with morphometric analysis of endometriosis-like lesions allows objective and reliable recording of endometriosis development in a nude mouse model. This quantification method could therefore be useful for future pharmacological and toxicological studies.

Reproduction of menstrual changes in transplanted human endometrial tissue in immunodeficient mice

BACKGROUND

Cultures of human endometrial tissue are useful for analysing the mechanisms underlying the menstrual cycle. However, long-term culture of endometrial tissue is difficult in vitro. Xenotransplantation of normal human endometrial tissue into immunodeficient mice could allow prolonged survival of the transplanted tissues.

METHODS

Proliferative-phase endometrial tissue samples from three women were transplanted into the subcutaneous space of ovariectomized, immunodeficient, non-obese diabetic (NOD)/severe combined immunodeficiency (SCID)/gammaC(null) (NOG) mice. The mice were treated with 17beta-estradiol (E2) for the first 14 days after transplantation, followed by E2 plus progesterone for the next 14 days. The transplants were investigated morphologically and immunohistochemically at various times after implantation.

RESULTS

The transplanted tissues contained large numbers of small glands, pseudostratification of the nuclei and dense stroma after treatment with E2 alone. After treatment with E2 plus progesterone, subnuclear vacuolation, luminal secretion and decidualization of the stroma were observed. When the hormone treatment ceased, tissue destruction occurred and the transplants returned to the proliferative phase. Lymphocytes were identified immunohistochemically: the numbers of CD56-positive and CD16-negative cells increased significantly in the stroma during the late secretory phase (day 28).

CONCLUSIONS

Human endometrial tissue transplanted into NOG mice showed similar histological changes to eutopic endometrial tissue during treatment with sex steroid hormones for 1 month. Moreover, lymphocytes were produced in the transplanted human endometrial tissue. This system represents a new experimental model of the human endometrium in vivo.

Quantitative assessment of human endometriotic tissue maintenance and regression in a noninvasive mouse model of endometriosis

Endometriosis is a prevalent disease characterized by the estrogen-dependent ectopic growth of endometrial tissue. Most of the current medical therapies consist in inducing a hypoestrogenic state in patients, but these treatments are associated with severe side effects and high recurrence rates. The development of convenient and reliable endometriosis animal models would be instrumental to accelerate the emergence of new therapeutic alternatives. Recently, we developed an improved experimental model for endometriosis, relying on the infection of human endometrial fragments by an adenovirus carrying the green fluorescent protein. Following injection of fluorescent fragments into nude mice, the implantation and growth of endometriotic-like lesions could be followed noninvasively. In the present work, we demonstrate that this model can be used to quantify the size of fluorescent endometriotic lesions by in vivo imaging. To this end, we repeatedly measured lesion size over a 4-week period in mice supplemented or not with estradiol. The model was adequate to confirm previous results showing that estrogen is dispensable for the implantation phase of endometrial tissue, whereas it is required for lesion maintenance. As a proof of concept for inducing regression of established lesions, ganciclovir was used to treat animals implanted with human fluorescent endometrial fragments expressing thymidine kinase. A significant decrease in lesion size was observed by in vivo imaging in ganciclovir-treated mice. Together, the data indicate that the noninvasive animal model described here provides a tool for drug testing and/or gene target validation in endometriosis.

Animal studies in endometriosis: a review

Endometriosis is a common women's health problem that is characterized by the presence of tissue resembling endometrium outside the uterus. The condition causes painful periods, chronic pelvic pain, and subfertility, which are potentially debilitating; and it affects millions of women worldwide. The diagnosis is made on visual inspection of the pelvis, usually at laparoscopy. The natural history is unknown, and well-controlled experiments are difficult to perform because of the need for repeated surgical procedures to assess endometriotic lesions over time. Thus, despite over 50 years' research, the cause of endometriosis remains unclear, and treatment options are limited. Animal models provide an invaluable tool to study risk factors, prevalence, and the natural history of endometriosis especially in those menstruating nonhuman primates that develop the disease spontaneously. Many of the practical problems associated with studying the disease in humans can therefore be overcome. The pathophysiology of endometriosis can also be investigated and new treatments assessed in both nonprimates and nonhuman primates, with "disease" induced by placing autologous uterine tissue in ectopic sites, or human endometrium in the case of nude mice. However, although nonprimates have obvious advantages as a model, the extent to which the induced lesions are truly representative of the disease itself is debatable. This review explores the value of the experimental models that have been used to date.

Reduction of apoptosis and proliferation in endometriosis

OBJECTIVE

To evaluate whether endometriosis could be related to an impaired balance between apoptosis and proliferation, two processes which could be modulated by hormonal status.

DESIGN

Immunohistochemical study.

SETTING

Academic research laboratory.

INTERVENTION(S)

Endometriotic samples obtained from peritoneum of women aged 26-40 years who were undergoing laparoscopy for pain or infertility.

MAIN OUTCOME MEASURE(S)

Apoptotic cells were detected with the use of the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assay. The production of p53 and bcl-2, estrogen and Progesterone (P) receptors, and cellular proliferation were assessed by immunohistochemistry in eutopic and ectopic endometria from 30 patients with endometriosis throughout the menstrual cycle. Results were compared with those from normal endometria from 15 fertile patients.

RESULT(S)

Endometriotic lesions were characterized by reduced TUNEL and p53 stainings and by enhanced bcl-2 staining. No correlation between apoptosis and estrogen receptor or P receptor levels was found. A lower amount of steroid receptor was found in endometriotic tissues, without cyclic modulation, compared with the eutopic endometrium.

CONCLUSION(S)

Our results suggest that when endometrial tissue is located at ectopic locations, it differs from eutopic endometrium by its proliferation rate, steroid hormone levels, and markers of apoptosis. A reduced sensitivity of endometriotic cells to apoptosis could promote the dissemination and implantation of these cells to ectopic sites.

Adhesion of endometrial cells labeled with 111Indium-tropolonate to peritoneum: a novel in vitro model to study endometriosis

OBJECTIVE

To evaluate, in a new original in vitro assay, putative factors that could modulate the adhesion of endometrial cells to peritoneum.

DESIGN

Prospective, controlled in vitro study.

SETTING

Academic research laboratory.

PATIENT(S)

Fourteen nonmenopausal women undergoing hysterectomy or laparoscopy for benign gynecologic indication.

INTERVENTION(S)

Endometrial cells obtained from women with regular cycles without endometriosis were labeled with 111Indium and confronted in vitro with mouse peritoneum in the presence of various cytokines and/or antiadhesive compounds.

MAIN OUTCOME MEASURE(S)

Radioactivity in 111Indium-labeled endometrial cells.

RESULT(S)

The adhesion of human endometrial cells to mouse peritoneum was increased by treatment with pro-inflammatory cytokines (interleukin IL-1beta, IL-6, TNF alpha, TGF-beta1). Whereas heparan sulfate had no effect on cell adhesion, a gel of ferric hyaluronate (Intergel) was able to counteract the pro-adhesive effect of cytokines. Interestingly, the pretreatment of peritoneum with cytokines, 24 hours before cell seeding in the presence of the ferric hyaluronate gel, restored the cytokine-promoting effect on cell adhesion.

CONCLUSION(S)

Proinflammatory cytokines promote the in vitro peritoneal adhesion of endometrial cells. An antiadhesive hyaluronate gel used in clinics decreases the adhesion in a dose-dependent manner and reduces cytokine bioavailability.