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Adenomyosis is a nonmalignant uterine disorder in which endometrial tissue exists within and grows into the myometrium. Animal models have generated limited insight into the still-unclear pathogenesis of adenomyosis, provided a platform for preclinical screening of many drugs and compounds with potential as therapeutics, and elucidated mechanisms underlying the pain and fertility issues that occur in many women with the disease. Spontaneous adenomyosis has been studied in nonhuman primates, primarily in the form of case reports. Adenomyosis is routinely experimentally induced in mice through methods such as neonatal tamoxifen exposure, pituitary engraftment, and human tissue xenotransplantation. Several studies have also reported hormonal or environmental toxicant exposures that give rise to murine adenomyosis, and genetically engineered models have been created that recapitulate the human-like condition, most notably involving alteration of β-catenin expression. This review describes the animal models for adenomyosis and their contributions to our understanding of the factors underpinning the development of symptoms. Animal models represent a unique opportunity for understanding the molecular basis of adenomyosis and developing efficacious treatment options for affected women. Herein, we assess their different potentials and limitations with regard to identification of new therapeutic interventions and reflect on future directions for research and drug validation.

Endometriosis is a condition of the female reproductive tract characterized by endometrium-like tissue growing outside the uterus. Though it is a common cause of pelvic pain and infertility, there is currently no reliable noninvasive method to diagnose the presence of endometriosis without surgery, and the pathophysiological mechanisms that lead to the occurrence of symptoms require further inquiry. Due to patient heterogeneity and delayed diagnosis, animal models are commonly used to study the development of endometriosis, but these are costly due to the large number of animals needed to test various treatments and experimental conditions at multiple endpoints. Here, we describe a method for synthesis of multimodal imaging gold-fluorescein isothiocyanate (FITC) nanoparticles with preclinical application via induction of nanoparticle-labeled endometriosis-like lesions in mice. Labeling donor endometrial tissue fragments with gold-FITC nanoparticles prior to induction of endometriosis in recipients enables in vivo detection of the gold-labeled lesions with photoacoustic imaging. The same imaging method can be used to visualize embryos noninvasively in pregnant mice. Furthermore, the conjugated FITC dye on the gold nanoparticles allows easy isolation of labeled lesion tissue under a fluorescence dissection microscope. After dissection, the presence of gold-FITC nanoparticles and endometrium-like histology of lesions can be verified through fluorescence imaging, gold enhancement, and immunostaining. This method for in vivo imaging of endometriosis-like lesions and fluorescence-guided dissection will permit new experimental possibilities for the longitudinal study of endometriosis development and progression as well as endometriosis-related infertility.

Though endometriosis and infertility are clearly associated, the pathophysiological mechanism remains unclear. Previous work has linked endometrial ARID1A loss to endometriosis-related endometrial non-receptivity. Here, we show in mice that ARID1A binds and regulates transcription of the Foxa2 gene required for endometrial gland function. Uterine specific deletion of Arid1a compromises gland development and diminishes Foxa2 and Lif expression. Deletion of Arid1a with Ltf-iCre in the adult mouse endometrial epithelium preserves gland development while still compromising gland function. Mice lacking endometrial epithelial Arid1a are severely sub-fertile due to defects in implantation, decidualization, and endometrial receptivity from disruption of the LIF-STAT3-EGR1 pathway. FOXA2 is also reduced in the endometrium of women with endometriosis in correlation with diminished ARID1A, and both ARID1A and FOXA2 are reduced in non-human primates induced with endometriosis. Our findings describe a role for ARID1A in the endometrial epithelium supporting early pregnancy establishment through the maintenance of gland function.

The endometrium, composed of epithelial and stromal cell compartments, is tightly regulated by the ovarian steroid hormones estrogen (E2) and progesterone (P4) during early pregnancy. Through the progesterone receptor (PGR), steroid receptor coactivators, and other transcriptional coregulators, progesterone inhibits E2-induced cell proliferation and induces the differentiation of stromal cells in a process called decidualization to promote endometrial receptivity. Although interleukin-13 receptor subunit alpha-2 (Il13ra2) is expressed in the human and mouse endometrium, its potential role in the steroid hormone regulation of the endometrium has not been thoroughly examined. In this study, we employed PGR knockout mice and steroid receptor coactivator-1 knockout mice (SRC-1−/−) to profile the expression of Il13ra2 in the murine endometrium and determine the role of these transcriptional regulators in the hormone-responsiveness of Il13ra2 expression. Furthermore, we utilized a well-established decidualization-inducing steroidogenic cocktail and a siRNA-based knockdown of IL13RA2 to determine the importance of IL13RA2 in the decidualization of primary human endometrial stromal cells. Our findings demonstrate that Il13ra2 is expressed in the subepithelial stroma of the murine endometrium in response to ovarian steroid hormones and during early pregnancy in a PGR- and SRC-1-dependent manner. Furthermore, we show that knockdown of IL13RA2 before in vitro decidualization of primary human endometrial stromal cells partially compromises the full decidualization response. We conclude that Il13ra2 is a downstream target of progesterone through PGR and SRC-1 and plays a role in mediating the stromal action of ovarian steroid hormones.

Though endometriosis and infertility are clearly associated, the pathophysiological mechanism remains unclear. Previous work has linked endometrial ARID1A loss to endometriosis-related endometrial non-receptivity. Here, we show in mice that ARID1A binds and regulates transcription of the Foxa2 gene required for endometrial gland function. Uterine specific deletion of Arid1a compromises gland development and diminishes Foxa2 and Lif expression. Deletion of Arid1a with Ltf-iCre in the adult mouse endometrial epithelium preserves gland development while still compromising gland function. Mice lacking endometrial epithelial Arid1a are severely sub-fertile due to defects in implantation, decidualization, and endometrial receptivity from disruption of the LIF-STAT3-EGR1 pathway. FOXA2 is also reduced in the endometrium of women with endometriosis in correlation with diminished ARID1A, and both ARID1A and FOXA2 are reduced in non-human primates induced with endometriosis. Our findings describe a role for ARID1A in the endometrial epithelium supporting early pregnancy establishment through the maintenance of gland function.

In the healthy endometrium, progesterone and estrogen signaling coordinate in a tightly regulated, dynamic interplay to drive a normal menstrual cycle and promote an embryo-receptive state to allow implantation during the window of receptivity. It is well-established that progesterone and estrogen act primarily through their cognate receptors to set off cascades of signaling pathways and enact large-scale gene expression programs. In endometriosis, when endometrial tissue grows outside the uterine cavity, progesterone and estrogen signaling are disrupted, commonly resulting in progesterone resistance and estrogen dominance. This hormone imbalance leads to heightened inflammation and may also increase the pelvic pain of the disease and decrease endometrial receptivity to embryo implantation. This review focuses on the molecular mechanisms governing progesterone and estrogen signaling supporting endometrial function and how they become dysregulated in endometriosis. Understanding how these mechanisms contribute to the pelvic pain and infertility associated with endometriosis will open new avenues of targeted medical therapies to give relief to the millions of women suffering its effects.

Endometrial cancer is the most common gynecologic malignancy with an estimated 63,230 new cases in 2018. Although early-stage and low grade endometrioid endometrial cancers (EEC) generally exhibit a favorable prognosis, 10-15% of tumors recur within 5 years with poor treatment outcomes and low survival rates. Therefore, there is an urgent obligation to explore the mechanism of tumor metastasis and recurrence to further elucidate the progression of EEC. Mitogen inducible gene 6 (MIG-6) plays a tumor suppressor role in endometrial cancer. Ablation of Mig-6 in the murine uterus leads to the development of endometrial hyperplasia and E2-induced EEC. However, how MIG-6 suppresses tumorigenesis and metastasis in EEC is unclear. We have developed a genetically engineered mouse model for metastatic and recurrent EEC that implicates coexistent Pten and Mig-6 mutations in EEC. We also added a double-fluorescent Cre reporter to our EEC mouse model to distinguish EEC from surrounding normal tissues. In Pgrcre/+Rosa26mTmG mice, the Pgr-positive uterine cells express GFP, while Pgr-negative cells express membrane-targeted tandem dimer Tomato. The ablation of both Mig-6 and Pten in the uterus (Pgrcre/+Mig-6f/fPtenf/f; Mig-6d/dPtend/d) dramatically accelerated the development of EEC compared to single ablation of either gene. Importantly, Pten mutation is not sufficient for distant metastasis, but mice with concurrent ablation of Mig-6 and Pten develop distant metastasis. After hysterectomy at stage I of EEC, 62% of Mig-6d/dPtend/d mice (5/8) developed recurrence of EEC in the abdomen and lung. Cholesterol metabolism plays a significant role in cancer metastasis, and Mig-6 plays a critical role in the regulation of cholesterol homeostasis and bile acid synthesis. The ingenuity pathway analysis revealed that cholesterol biosynthesis was the most significantly changed pathway in the endometrial hyperplasia from 2-week-old Mig-6d/dPtend/d mice compared with Ptend/d mice. We found 67 and 18 significantly increased or decreased transcripts, respectively, that are related cholesterol biosynthesis. HMG-coA reductase inhibitors, commonly known as statins, account for the great majority of cholesterol-lowering drug use. However, little is known about the association between statin use and incidence of most types of cancers. To determine the effect of statins on tumorigenesis of EEC in Mig-6d/dPtend/d mice, the mutant mice were treated with atorvastatin (10mg/kg/day oral administration) or vehicle for 2 months. Treatment with statins significantly reduced development and progression of EEC in Mig-6d/dPtend/d mice compared to the vehicle group. Our results demonstrate that Mig-6 suppresses metastasis and recurrence in EEC with Pten mutation by inhibiting cholesterol biosynthesis. Research reported in this publication was supported by The Mary Kay Foundation 2019 research grant. Citation Format: Tae Hoon Kim, Ryan M. Marquardt, Russell R. Broaddus, Jae-Wook Jeong. The role of Mig-6 as a tumor suppressor in metastatic and recurrent endometrial cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 428.