Transcriptomic analyses of ovarian clear-cell carcinoma with concurrent endometriosis.

Introduction: Endometriosis, a benign inflammatory disease whereby endometrial-like tissue grows outside the uterus, is a risk factor for endometriosis-associated ovarian cancers. In particular, ovarian endometriomas, cystic lesions of deeply invasive endometriosis, are considered the precursor lesion for ovarian clear-cell carcinoma (OCCC). Methods: To explore this transcriptomic landscape, OCCC from women with pathology-proven concurrent endometriosis (n = 4) were compared to benign endometriomas (n = 4) by bulk RNA and small-RNA sequencing. Results: Analysis of protein-coding genes identified 2449 upregulated and 3131 downregulated protein-coding genes (DESeq2, P< 0.05, log2 fold-change > |1|) in OCCC with concurrent endometriosis compared to endometriomas. Gene set enrichment analysis showed upregulation of pathways involved in cell cycle regulation and DNA replication and downregulation of pathways involved in cytokine receptor signaling and matrisome. Comparison of pathway activation scores between the clinical samples and publicly-available datasets for OCCC cell lines revealed significant molecular similarities between OCCC with concurrent endometriosis and OVTOKO, OVISE, RMG1, OVMANA, TOV21G, IGROV1, and JHOC5 cell lines. Analysis of miRNAs revealed 64 upregulated and 61 downregulated mature miRNA molecules (DESeq2, P< 0.05, log2 fold-change > |1|). MiR-10a-5p represented over 21% of the miRNA molecules in OCCC with endometriosis and was significantly upregulated (NGS: log2fold change = 4.37, P = 2.43e-18; QPCR: 8.1-fold change, P< 0.05). Correlation between miR-10a expression level in OCCC cell lines and IC50 (50% inhibitory concentration) of carboplatin in vitro revealed a positive correlation (R2 = 0.93). MiR-10a overexpression in vitro resulted in a significant decrease in proliferation (n = 6; P< 0.05) compared to transfection with a non-targeting control miRNA. Similarly, the cell-cycle analysis revealed a significant shift in cells from S and G2 to G1 (n = 6; P< 0.0001). Bioinformatic analysis predicted that miR-10a-5p target genes that were downregulated in OCCC with endometriosis were involved in receptor signaling pathways, proliferation, and cell cycle progression. MiR-10a overexpression in vitro was correlated with decreased expression of predicted miR-10a target genes critical for proliferation, cell-cycle regulation, and cell survival including [SERPINE1 (3-fold downregulated; P< 0.05), CDK6 (2.4-fold downregulated; P< 0.05), and RAP2A (2-3-fold downregulated; P< 0.05)]. Discussion: These studies in OCCC suggest that miR-10a-5p is an impactful, potentially oncogenic molecule, which warrants further studies.

Utilizing an office based laboratory (OBL) during the COVID-19 pandemic for vascular surgical patients.

COVID-19 pandemic brought new challenges in healthcare including the need to create tiered class recommendations about which types patients to treat urgently and which surgical cases to defer. This is a report of a single center's Office Based Laboratory (OBL) system to prioritize vascular patients and preserve acute care resources and personnel. In reviewing three months of data, it appears that by continuing to provide the urgent care needed for this chronically ill population, the insurmountable backup of surgical procedures is prevented in the operating room once elective surgeries resumed. The OBL was able to continue providing care at the same pre-pandemic rate to a large intercity population.

Unintended Consequences of Antibiotic Therapy on the Microbiome Delivers a Gut Punch in Ovarian Cancer.

While the early use of antibiotics during chemotherapy may be lifesaving, antibiotic therapy is associated with worse outcomes in patients with ovarian cancer during platinum chemotherapy. The study by Chambers and colleagues in this issue of Cancer Research provides mechanistic insights into how disrupting the gut microbiome with broad-spectrum antibiotics negatively influences the survival of patients with ovarian cancer and highlights the impact of the gut microbiome on tumor progression and response to therapy. Treatment of ovarian cancer models with a broad-spectrum antibiotic cocktail (ABX, vancomycin, neomycin sulfate, metronidazole, ampicillin) changed the gut microbiome and increased tumor growth and development of cisplatin resistance. Stem cells, reported to drive resistance to chemotherapy and disease recurrence in ovarian cancer, were enriched as a surprising consequence of ABX-induced microbiome disruption. Immune-competent and immune-deficient mice revealed that ABX treatment enhanced the cisplatin-induced stemness and provided evidence for immune surveillance of ovarian cancer stem cells through the gut microbiome. Two gut-derived metabolites, indole-3-propionic acid and indoxyl sulfate, suppressed by ABX treatment and reestablished with cecal microbial transplantation colonization of ABX-treated mice, were identified as potential effectors connecting the gut microbiome to ovarian cancer growth. This clinically relevant study opens new therapeutic opportunities for patients-one aimed at interventions to increase platinum sensitivity and another aimed at preventing the potential adverse effects of broad-spectrum antibiotic treatment. Both represent paradigm changes to standard care. See related article by Chambers et al., p. 4654.

Nurse driven outpatient wound center: Reducing readmission with wound care excellence.

There is a growing need for new and innovative ways to care for patients in the ambulatory setting, including providing wound care for patients. A vascular surgery department in a large urban academic medical center noted there was an increasing number of patients with chronic wounds that needed weekly care. The number of patients, the time needed to provide wound care, and limited clinic space was creating a strain on traditional clinic hours. Collaboration between one of the vascular surgery advanced practice registered nurses (APRN) and vascular registered nurse (RN) led to the creation of a vascular wound clinic. Patients with chronic wounds were identified by vascular surgeons at one institution and referred to the wound clinic. A retrospective chart review was used to look at number of patients, number of visits per patient, surgical interventions, number of wounds closed, size of wounds, and complications. The ability to provide a single point of contact for the patient's vascular surgery and wound care needs allowed the clinic to provide comprehensive care for 29 patients and close more than 75% of wounds. The retrospective chart review found that patients receiving weekly wound care with clear communication from the multidisciplinary team, the nursing and nurse practitioner interventions kept most patients out of the hospital, with only two unplanned readmissions to the hospital, neither due to chronic wounds. This nursing led wound clinic was able to accommodate complex vascular surgery patients, heal chronic wounds, and decrease unplanned readmissions. Expanding the clinic to assist with limb salvage and more podiatric patients is providing a new patient base and improving the care for the community that it serves.

Translational Applications of Linear and Circular Long Noncoding RNAs in Endometriosis.

Endometriosis is a chronic gynecologic disease that negatively affects the quality of life of many women. Unfortunately, endometriosis does not have a cure. The current medical treatments involve hormonal manipulation with unwanted side effects and high recurrence rates after stopping the medication. Sadly, a definitive diagnosis for endometriosis requires invasive surgical procedures, with the risk of complications, additional surgeries in the future, and a high rate of recurrence. Both improved therapies and noninvasive diagnostic tests are needed. The unique molecular features of endometriosis have been studied at the coding gene level. While the molecular components of endometriosis at the small RNA level have been studied extensively, other noncoding RNAs, such as long intergenic noncoding RNAs and the more recently discovered subset of long noncoding RNAs called circular RNAs, have been studied more limitedly. This review describes the molecular formation of long noncoding and the unique circumstances of the formation of circular long noncoding RNAs, their expression and function in endometriosis, and promising preclinical studies. Continued translational research on long noncoding RNAs, including the more stable circular long noncoding RNAs, may lead to improved therapeutic and diagnostic opportunities.

Building a virtual summer research experience in cancer for high school and early undergraduate students: lessons from the COVID-19 pandemic.

BACKGROUND: The COVID-19 pandemic posed a unique challenge for summer research programs in 2020, particularly for programs aimed at hands-on experience for younger trainees. The Indiana University Melvin and Bren Simon Comprehensive Cancer Center supports two pipeline programs, which traditionally immerse high school juniors, seniors, and early undergraduate students from underrepresented populations in science in hands-on projects in cancer biology labs. However, due to social distancing policies during the pandemic and reduction of research operations, these students were not physically allowed on campus. Thus, the authors set out to strategically pivot to a wholly virtual curriculum and evaluate the Virtual Summer Research Experience in Cancer outcomes. METHODS: The virtual program included four components: 1. a core science and professional development curriculum led by high school teachers and senior undergraduates; 2. faculty-delivered didactic sessions on cancer science; 3. mentored, virtual research projects with research faculty; and 4. online networking events to encourage vertical mentoring. Outcomes data were measured using a locally created 11-item Research Preparation Scale, daily electronic feedback, and weekly structured evaluation and feedback via Zoom. RESULTS: Outcome data suggested high self-reported satisfaction with the virtual program. Outcome data also revealed the importance of coordination between multiple entities for seamless program implementation. This includes the active recruitment and participation of high school teachers and further investment in information technology capabilities of institutions. CONCLUSIONS: Findings reveal a path to educate and train high school and early undergraduate students in cancer research when hands-on, in-person training is not feasible. Virtual research experiences are not only useful to engage students during public health crises but can provide an avenue for cancer centers to expand their cancer education footprints to remotely located schools and universities with limited resources to provide such experiences to their students.

Vaginal Squamous Cell Carcinoma Develops in Mice with Conditional Arid1a Loss and Gain of Oncogenic Kras Driven by Progesterone Receptor Cre.

Oncogenic KRAS mutations are a common finding in endometrial cancers. Recent sequencing studies indicate that loss-of-function mutations in the ARID1A gene are enriched in gynecologic malignant tumors. However, neither of these genetic insults alone are sufficient to develop gynecologic cancer. To determine the role of the combined effects of deletion of Arid1a and oncogenic Kras, Arid1aflox/flox mice were crossed with KrasLox-Stop-Lox-G12D/+ mice using progesterone receptor Cre (PgrCre/+). Histologic analysis and immunohistochemistry of survival studies were used to characterize the mutant mouse phenotype. Hormone dependence was evaluated by ovarian hormone depletion and estradiol replacement. Arid1aflox/flox; KrasLox-Stop-Lox-G12D/+; PgrCre/+ mice were euthanized early because of invasive vaginal squamous cell carcinoma. Younger mice had precancerous intraepithelial lesions. Immunohistochemistry supported the pathological diagnosis with abnormal expression and localization of cytokeratin 5, tumor protein P63, cyclin-dependent kinase inhibitor 2A, and Ki-67, the marker of proliferation. Ovarian hormone deletion in Arid1aflox/flox; KrasLox-Stop-Lox-G12D/+; PgrCre/+ mice resulted in atrophic vaginal epithelium without evidence of vaginal tumors. Estradiol replacement in ovarian hormone-depleted Arid1aflox/flox; KrasLox-Stop-Lox-G12D/+; PgrCre/+ mice resulted in lesions that resembled the squamous cell carcinoma in intact mice. Therefore, this mouse can be used to study the transition from benign precursor lesions into invasive vaginal human papillomavirus-independent squamous cell carcinoma, offering insights into progression and pathogenesis of this rare disease.

Targeting progesterone signaling prevents metastatic ovarian cancer.

Effective cancer prevention requires the discovery and intervention of a factor critical to cancer development. Here we show that ovarian progesterone is a crucial endogenous factor inducing the development of primary tumors progressing to metastatic ovarian cancer in a mouse model of high-grade serous carcinoma (HGSC), the most common and deadliest ovarian cancer type. Blocking progesterone signaling by the pharmacologic inhibitor mifepristone or by genetic deletion of the progesterone receptor (PR) effectively suppressed HGSC development and its peritoneal metastases. Strikingly, mifepristone treatment profoundly improved mouse survival (∼18 human years). Hence, targeting progesterone/PR signaling could offer an effective chemopreventive strategy, particularly in high-risk populations of women carrying a deleterious mutation in the BRCA gene.

Three-Dimensional Biofabrication Models of Endometriosis and the Endometriotic Microenvironment.

Endometriosis occurs when endometrial-like tissue grows outside the uterine cavity, leading to pelvic pain, infertility, and increased risk of ovarian cancer. The present study describes the optimization and characterization of cellular spheroids as building blocks for Kenzan scaffold-free method biofabrication and proof-of-concept models of endometriosis and the endometriotic microenvironment. The spheroid building blocks must be of a specific diameter (~500 µm), compact, round, and smooth to withstand Kenzan biofabrication. Under optimized spheroid conditions for biofabrication, the endometriotic epithelial-like cell line, 12Z, expressed high levels of estrogen-related genes and secreted high amounts of endometriotic inflammatory factors that were independent of TNFα stimulation. Heterotypic spheroids, composed of 12Z and T-HESC, an immortalized endometrial stromal cell line, self-assembled into a biologically relevant pattern, consisting of epithelial cells on the outside of the spheroids and stromal cells in the core. 12Z spheroids were biofabricated into large three-dimensional constructs alone, with HEYA8 spheroids, or as heterotypic spheroids with T-HESC. These three-dimensional biofabricated constructs containing multiple monotypic or heterotypic spheroids represent the first scaffold-free biofabricated in vitro models of endometriosis and the endometriotic microenvironment. These efficient and innovative models will allow us to study the complex interactions of multiple cell types within a biologically relevant microenvironment.

Pten and Dicer1 loss in the mouse uterus causes poorly differentiated endometrial adenocarcinoma.

Endometrial cancer remains the most common gynecological malignancy in the United States. While the loss of the tumor suppressor, PTEN (phosphatase and tensin homolog), is well studied in endometrial cancer, recent studies suggest that DICER1, the endoribonuclease responsible for miRNA genesis, also plays a significant role in endometrial adenocarcinoma. Conditional uterine deletion of Dicer1 and Pten in mice resulted in poorly differentiated endometrial adenocarcinomas, which expressed Napsin A and HNF1B (hepatocyte nuclear factor 1 homeobox B), markers of clear-cell adenocarcinoma. Adenocarcinomas were hormone-independent. Treatment with progesterone did not mitigate poorly differentiated adenocarcinoma, nor did it affect adnexal metastasis. Transcriptomic analyses of DICER1 deleted uteri or Ishikawa cells revealed unique transcriptomic profiles and global miRNA downregulation. Computational integration of miRNA with mRNA targets revealed deregulated let-7 and miR-16 target genes, similar to published human DICER1-mutant endometrial cancers from TCGA (The Cancer Genome Atlas). Similar to human endometrial cancers, tumors exhibited dysregulation of ephrin-receptor signaling and transforming growth factor-beta signaling pathways. LIM kinase 2 (LIMK2), an essential molecule in p21 signal transduction, was significantly upregulated and represents a novel mechanism for hormone-independent pathogenesis of endometrial adenocarcinoma. This preclinical mouse model represents the first genetically engineered mouse model of poorly differentiated endometrial adenocarcinoma.

Unique Molecular Features in High-Risk Histology Endometrial Cancers.

Endometrial cancer is the most common gynecologic malignancy in the United States and the sixth most common cancer in women worldwide. Fortunately, most women who develop endometrial cancer have low-grade early-stage endometrioid carcinomas, and simple hysterectomy is curative. Unfortunately, 15% of women with endometrial cancer will develop high-risk histologic tumors including uterine carcinosarcoma or high-grade endometrioid, clear cell, or serous carcinomas. These high-risk histologic tumors account for more than 50% of deaths from this disease. In this review, we will highlight the biologic differences between low- and high-risk carcinomas with a focus on the cell of origin, early precursor lesions including atrophic and proliferative endometrium, and the potential role of stem cells. We will discuss treatment, including standard of care therapy, hormonal therapy, and precision medicine-based or targeted molecular therapies. We will also discuss the impact and need for model systems. The molecular underpinnings behind this high death to incidence ratio are important to understand and improve outcomes.

Uterine Epithelial Development and Enhancer of Zeste Homolog 2: It Is Important for More than Just Cancer.

This commentary highlights the article by Fang et al that describes the role of enhancer of zeste homolog 2 in endometrial development.

The Endometriotic Tumor Microenvironment in Ovarian Cancer.

Women with endometriosis are at increased risk of developing ovarian cancer, specifically ovarian endometrioid, low-grade serous, and clear-cell adenocarcinoma. An important clinical caveat to the association of endometriosis with ovarian cancer is the improved prognosis for women with endometriosis at time of ovarian cancer staging. Whether endometriosis-associated ovarian cancers develop from the molecular transformation of endometriosis or develop because of the endometriotic tumor microenvironment remain unknown. Additionally, how the presence of endometriosis improves prognosis is also undefined, but likely relies on the endometriotic microenvironment. The unique tumor microenvironment of endometriosis is composed of epithelial, stromal, and immune cells, which adapt to survive in hypoxic conditions with high levels of iron, estrogen, and inflammatory cytokines and chemokines. Understanding the unique molecular features of the endometriotic tumor microenvironment may lead to impactful precision therapies and/or modalities for prevention. A challenge to this important study is the rarity of well-characterized clinical samples and the limited model systems. In this review, we will describe the unique molecular features of endometriosis-associated ovarian cancers, the endometriotic tumor microenvironment, and available model systems for endometriosis-associated ovarian cancers. Continued research on these unique ovarian cancers may lead to improved prevention and treatment options.

Distinct molecular pathways in ovarian endometrioid adenocarcinoma with concurrent endometriosis.

Women with endometriosis, a benign growth of endometrial tissue outside the uterine cavity, are at increased risk of specific histotypes of epithelial ovarian cancer, such as ovarian endometrioid adenocarcinoma (OEA). Women with OEA who have endometriosis at time of surgical staging demonstrate improved clinical prognosis compared to women with OEA without evidence of endometriosis. However, the molecular contributions of the endometriotic tumor microenvironment to these ovarian cancers remain poorly understood. As a starting point, we used a platform for genome-wide transcriptomic profiling to compare specimens of OEA from women with and without concurrent endometriosis and benign reproductive tract tissues, including proliferative endometrium and typical and atypical endometrioma samples (n = 20). Principle component analysis revealed distinct clustering between benign and malignant samples as well as malignant samples with and without concurrent endometriosis. Examination of gene signatures revealed that OEA with concurrent endometriosis contained a unique molecular signature compared to OEA without concurrent endometriosis, distinguished by 682 unique genes differentially expressed (fold change < or >1.5, p < 0.01). Bioinformatic analysis of these differentially expressed gene products using ingenuity pathway analysis revealed activation of NFkB signaling, an inflammatory signaling pathway constitutively active in endometriosis. DAVID functional annotation clustering further revealed enrichment in RAS signaling as both cytoskeleton organization and GTPase regulator activity relied heavily on RAS protein signal transduction. Gene set enrichment analysis highlighted immune and inflammatory nodes involved in OEA with concurrent endometriosis. These observations provide novel resources for understanding molecular subtleties potentially involved in OEA within the context of the endometriotic tumor microenvironment.

The role of MicroRNA molecules and MicroRNA-regulating machinery in the pathogenesis and progression of epithelial ovarian cancer.

MicroRNA molecules are small, single-stranded RNA molecules that function to regulate networks of genes. They play important roles in normal female reproductive tract biology, as well as in the pathogenesis and progression of epithelial ovarian cancer. DROSHA, DICER, and Argonaute proteins are components of the microRNA-regulatory machinery and mediate microRNA production and function. This review discusses aberrant expression of microRNA molecules and microRNA-regulating machinery associated with clinical features of epithelial ovarian cancer. Understanding the regulation of microRNA molecule production and function may facilitate the development of novel diagnostic and therapeutic strategies to improve the prognosis of women with epithelial ovarian cancer. Additionally, understanding microRNA molecules and microRNA-regulatory machinery associations with clinical features may influence prevention and early detection efforts.

The effectiveness of a multidisciplinary, team-based approach to cesarean hysterectomy in modern obstetric practice.

OBJECTIVE: To examine the effectiveness of a multidisciplinary, team-based approach to management of cesarean hysterectomy. METHODS: In a retrospective chart review, data were analyzed from a quality assurance database of hysterectomies performed after cesarean delivery at one institution in the USA. Patients were identified through billing codes for cesarean delivery, cross-referenced to codes for hysterectomy. Demographic, reproductive, and outcome data were compared before (2000-2005) and after (2011-2013) implementation of a multidisciplinary team-based protocol. RESULTS: Across the two study periods, 107 cesarean hysterectomies were identified (69 pre-implementation, 38 post-implementation). In univariate analysis, the post-implementation group had fewer days in surgical intensive care than did the pre-implementation group (0.21 ± 0.41 vs 1.04 ± 2.44 days; P=0.011), and a lower frequency of febrile morbidity (4 [11%] vs 22 [32%]; P=0.033]. In multivariate analysis with adjustment for potential confounders, the likelihood of postoperative febrile morbidity was higher during the pre-implementation than the post-implementation period (adjusted odds ratio 3.5, 95% confidence interval 1.09-13.65; P=0.048). CONCLUSION: Outcomes were improved after the multidisciplinary team-based approach to cesarean hysterectomy was implemented. Team-based approaches to care of women undergoing cesarean hysterectomy are important to improve outcomes.

Global Transcriptome Abnormalities of the Eutopic Endometrium From Women With Adenomyosis.

OBJECTIVE: Adenomyosis is a clinical disorder defined by the presence of endometrial glands and stroma within the myometrium, the pathogenesis of which is poorly understood. We postulate that dysregulation of genes and pathways in eutopic endometrium may predispose to ectopic implantation. No study, to our knowledge, has examined the global transcriptome of isolated eutopic endometrium from women with clinically significant adenomyosis. DESIGN: Laboratory-based study with full institutional review board approval and consents. MATERIAL AND METHODS: Endometrial sampling was performed on hysterectomy specimens (proliferative phase) from symptomatic women with pathologically confirmed diffuse adenomyosis (n = 3). Controls (n = 5) were normo-ovulatory patients without adenomyosis. All patients were free from leiomyoma, endometriosis, and hormonal exposures. Isolated purified total RNA was subjected to microarray analysis using the Gene 1.0 ST Affymetrix platform. Data were analyzed with GeneSpring and Ingenuity Pathway analysis. Validation of several genes was undertaken by quantitative real-time reverse transcriptase polymerase chain reaction. RESULTS: Comparison of transcriptomes of proliferative endometrium from women with and without adenomyosis revealed 140 upregulated and 884 downregulated genes in samples from women with adenomyosis compared to controls. Highly differentially expressed genes include those involved in regulation of apoptosis, steroid hormone responsiveness, and proteins involved in extracellular matrix remodeling as well as microRNAs of unknown significance. Affected canonical pathways included eukaryotic initiation factor 2 signaling, oxidative phosphorylation, mitochondrial dysfunction, estrogen receptor signaling, and mammalian target of rapamycin signaling. CONCLUSION: The eutopic endometrium in patients with adenomyosis has fundamental abnormalities that may predispose to invasion and survival beyond the myometrial interface.

Endometrial Expression of Steroidogenic Factor 1 Promotes Cystic Glandular Morphogenesis.

Epigenetic silencing of steroidogenic factor 1 (SF1) is lost in endometriosis, potentially contributing to de novo local steroidogenesis favoring inflammation and growth of ectopic endometrial tissue. In this study, we examine the impact of SF1 expression in the eutopic uterus by a novel mouse model that conditionally expresses SF1 in endometrium. In vivo SF1 expression promoted the development of enlarged endometrial glands and attenuated estrogen and progesterone responsiveness. Endometriosis induction by autotransplantation of uterine tissue to the mesenteric membrane resulted in the increase in size of ectopic lesions from SF1-expressing mice. By integrating the SF1-dependent transcriptome with the whole genome binding profile of SF1, we identified uterine-specific SF1-regulated genes involved in Wingless and Progesterone receptor-Hedgehog-Chicken ovalbumin upstream promoter transcription factor II signaling for gland development and epithelium-stroma interaction, respectively. The present results indicate that SF1 directly contributes to the abnormal uterine gland morphogenesis, an inhibition of steroid hormone signaling and activation of an immune response, in addition to previously postulated estrogen production.

Deletion of Arid1a in Reproductive Tract Mesenchymal Cells Reduces Fertility in Female Mice.

Women with endometriosis can suffer from decreased fecundity or complete infertility via abnormal oocyte function or impaired placental-uterine interactions required for normal pregnancy establishment and maintenance. Although AT-rich interactive domain 1A (SWI-like) (ARID1A) is a putative tumor suppressor in human endometrial cancers and endometriosis-associated ovarian cancers, little is known about its role in normal uterine function. To study the potential function of ARID1A in the female reproductive tract, we generated mice with a conditional knockout of Arid1a using anti-Müllerian hormone receptor 2-Cre Female Arid1a conditional knockout mice exhibited a progressive decrease in number of pups per litter, with a precipitous decline after the second litter. We observed no tumors in virgin mice, although one knockout mouse developed a uterine tumor after pregnancy. Unstimulated virgin female knockout mice showed normal oviductal, ovarian, and uterine histology. Uteri of Arid1a knockout mice showed a normal decidualization response and appropriate responses to estradiol and progesterone stimulation. In vitro studies using primary cultures of human endometrial stromal fibroblasts revealed that small interfering RNA knockdown of ARID1A did not affect decidualization in vitro. Timed pregnancy studies revealed the significant resorption of embryos at Embryonic Day 16.5 in knockout mice in the third pregnancy. In addition to evidence of implantation site hemorrhage, pregnant Arid1a knockout mice showed abnormal placental morphology. These results suggest that Arid1a supports successful pregnancy through its role in placental function.