Comprehensive transcriptional atlas of human adenomyosis deciphered by the integration of single-cell RNA-sequencing and spatial transcriptomics

The human endometrium: atlases, models, and prospects

Approximately every month, the human endometrium undergoes a cycle of proliferation, differentiation, and, in the absence of pregnancy, shedding and repair. Each cycle relies on intricate interorgan coordination of hormonal secretions. Endometrial dysfunction causes significant health complications, including abnormal menstrual bleeding and endometriosis. However, effective diagnosis and treatments are hampered by understudied aetiology. Recent single-cell profiling has disentangled the diverse and dynamic nature of the endometrium, revealing regulatory roles of WNT, NOTCH, and TGFβ signalling. These insights have informed mechanistic studies enabled by advanced in vitro models that capture endometrial cellular heterogeneity and structure. In this review, we outline key single-cell transcriptomics atlases and models that provided new avenues for studying endometrial biology, discuss their limitations, and propose future directions.

Adenomyosis-associated infertility: an update of the immunological perspective

Adenomyosis is characterized by the invasion of endometrial glands and stroma into the myometrium. Its clinical manifestations often include dysmenorrhoea, excessive menstrual bleeding and infertility. Reduced pregnancy and live birth rates and an increased miscarriage rate are observed in women with adenomyosis. This review summarizes relevant advances and presents the underlying mechanisms of adenomyosis-associated infertility from an immunological perspective. Individuals with adenomyosis exhibit imbalances in immune cell subpopulations and the endocrine hormone-immunomodulatory axis. These immunological alterations may be key contributors to, or at least accomplices in, impaired endometrial receptivity. In addition, adenomyosis often occurs in association with endometriosis, uterine leiomyoma or endometrial polyps, which are pathogenetically relevant; their similarities and differences are discussed from an immunological perspective. The clinical diagnostic criteria of adenomyosis are not perfect, and the pathogenesis remains to be fully explored. Therefore screening for effective targets for early diagnosis and treatment at the cellular and molecular levels from the immunological point of view holds great potential, which will be of great importance in preventing this disease and improving women's reproductive health.

From Invaginating Site to Deep Lesion: Spatial Transcriptomics Unravels Ectopic Endometrial Penetration Features in Adenomyosis

Adenomyosis, characterized by clinical intractability, significantly impacts female fertility and life quality due to the absence of definitive diagnostic markers and effective treatment options. The invagination theory is a primary hypothesis for adenomyosis, but the underlying molecular mechanisms remain unclear. In this study, a spatial transcriptional landscape of adenomyosis with an evident invagination structure is mapped from the endometrial invaginating site to ectopic lesions utilizing spatial transcriptomics and single-cell RNA sequencing. In addition, the authors employ bulk RNA sequencing deconvolution to assess the significance of core spatial ecotypes, use histological techniques to target specific cell types, and conduct in vitro experiments for validation. At the invagination site, SFRP5+ epithelial cells promote endometrial proliferation and angiogenesis through secretion of IHH. During the invading process, ESR1+ smooth muscle cells (SMCs) facilitate invasion by creating migratory tracts via collagen degradation. Within deep lesions, CNN1+ stromal fibroblasts induce fibrosis by undergoing a fibroblast-to-myofibroblast transition (FMT) in response to pathologic profibrogenic signals in the microenvironment of lesions. This work offers an in-depth understanding of the molecular mechanisms underlying the pathological processes of adenomyosis with invagination. Furthermore, this work introduces the first transcriptomics web source of adenomyosis, which is expected to be a valuable resource for subsequent research.

Emerging targets for advancing endometrial therapeutics

The endometrium plays a crucial role in female health. Globally, millions of women are affected by endometrial/uterine disorders, yet the endometrium and its role in gynaecological pathologies have been understudied. Gaining insight into the detailed endometrial architecture, gene expression, spatial and temporal cellular interactions, and microenvironment is essential for understanding the physiology and pathophysiology of this dynamic tissue. The current paper highlights the latest targets for advancing endometrial research that include single-cell RNA sequencing, spatial transcriptomics, the microbiome, organoid models, analysis of menstrual blood and the less-studied endometrial ageing. The authors hope that this summary will provide more insight into the novel methods, highlight advancing endometrial therapeutics and inspire readers to generate fresh ideas for future research avenues.

Mapping Human Uterine Disorders Through Single-Cell Transcriptomics

Disruptions in uterine tissue function contribute to disorders such as endometriosis, adenomyosis, endometrial cancer, and fibroids, which all significantly impact health and fertility. Advances in transcriptomics, particularly single-cell RNA sequencing, have revolutionized uterine biological research by revealing the cellular heterogeneity and molecular mechanisms underlying disease states. Single-cell RNA sequencing and spatial transcriptomics have mapped endometrial and myometrial cellular landscapes, which helped to identify critical cell types, signaling pathways, and phase-specific dynamics. Said transcriptomic technologies also identified stromal and immune cell dysfunctions, such as fibroblast-to-myofibroblast transitions and impaired macrophage activity, which drive fibrosis, chronic inflammation, and lesion persistence in endometriosis. For endometrial cancer, scRNA-seq uncovered tumor microenvironmental complexities, identifying cancer-associated fibroblast subtypes and immune cell profiles contributing to progression and therapeutic resistance. Similarly, studies on adenomyosis highlighted disrupted signaling pathways, including Wnt and VEGF, and novel progenitor cell populations linked to tissue invasion and neuroinflammation, while single-cell approaches characterized smooth muscle and fibroblast subpopulations in uterine fibroids, elucidating their roles in extracellular matrix remodeling and signaling pathways like ERK and mTOR. Despite challenges such as scalability and reproducibility, single-cell transcriptomic approaches may have potential applications in biomarker discovery, therapeutic target identification, and personalized medicine in gynecological disorders.

Hormone receptor profile of ectopic and eutopic endometrium in adenomyosis: a systematic review

STUDY QUESTION

What is the hormone receptor profile of adenomyosis lesions in comparison to correctly located endometrium?

SUMMARY ANSWER

Adenomyosis lesions exhibit increased oestrogen receptor (ER) expression compared to the eutopic endometrium; there are conflicting results regarding progesterone receptor (PR) expression and a lack of studies on androgen receptor (AR) expression.

WHAT IS KNOWN ALREADY

Adenomyosis lesions express hormone receptors indicating an influence from ovarian steroid hormones. However, hormone treatments are often ineffective in controlling adenomyosis symptoms, which suggests alternate hormonal responses and, potentially, a distinct hormone receptor expression profile within adenomyosis lesions compared to the eutopic endometrium.

STUDY DESIGN SIZE DURATION

This systematic review with a thematic analysis retrieved studies from the PubMed, Ovid Medline, Embase, Scopus, and Cochrane Library databases, and searches were conducted from inception through to May 2024. Human studies were included and identified using a combination of exploded MeSH terms ('adenomyosis') and free-text search terms ('oestrogen receptor', 'progesterone receptor', 'androgen receptor', 'hormone receptor').

PARTICIPANTS/MATERIALS SETTING METHODS

This review was reported in accordance with the PRISMA guidelines. All studies reporting original data concerning hormone receptors in adenomyosis lesions compared to eutopic endometrium in adenomyosis were included. Studies that did not report original data or provide a review of the field were excluded. Bias analysis was completed for each study using the Newcastle-Ottawa scoring system.

MAIN RESULTS AND THE ROLE OF CHANCE

There were 1905 studies identified, which were screened to include 12 studies that met the eligibility criteria, including 11 proteomic studies and one transcriptional study, with a total of 555 individual participants. ER expression was consistently increased in adenomyosis lesions compared to the eutopic endometrium, specifically in the secretory phase. When endometrial subregion was considered, this difference was specific to the endometrial functionalis only. When different isoforms were considered, this increase in ER expression was specific to ERα rather than ERβ. There were conflicting results on PR expression, with most studies showing no significant difference or reduced levels in adenomyosis lesions compared to the eutopic endometrium. There is a paucity of data on AR expression in adenomyosis lesions, with only one study of small sample size included.

LIMITATIONS REASONS FOR CAUTION

A high risk of bias arose from studies grouping endometrial samples across different menstrual cycle phases for analysis. The coexistence of gynecological conditions like endometriosis may also confound the hormone receptor profile of the eutopic endometrium. Most studies employing immunostaining did not comment on region-specific differences in the endometrium. Given the well-documented cyclical variations in hormone receptor expression within the endometrium, the need for more attention to region-specific differences represents a notable limitation in the current body of literature.

WIDER IMPLICATIONS OF THE FINDINGS

The systematic review highlights oestrogen dominance through elevated ERα levels in adenomyosis lesions, which agrees with the literature suggesting local hyper-oestrogenism in adenomyosis lesions. Heterogeneity in menstrual cycle timing and lack of endometrial region specificity prevent conclusions on progesterone resistance within adenomyosis lesions in this study. Future investigations should minimize the bias through well-defined cohorts, leading to robust exploration of hormone receptor profiles in adenomyosis lesions to identify therapeutic targets and deepen our understanding of adenomyosis pathogenesis.

STUDY FUNDING/COMPETING INTERESTS

This work was supported by Wellbeing of Women Research Project grants RG1073 and RG2137 (D.K.H.), a Wellbeing of Women Entry-Level Scholarship ELS706 and a Medical Research Council grant MR/V007238/1 (A.M. and D.K.H.), as well as the University of Liverpool (L.T.). There are no conflicts of interest.

HROPEN-24-0294R2

The review protocol was published in the PROSPERO Register of Systematic Reviews on 27 September 2023, registration number CRD4202346.

Role of PRMT5 mediated HOXA10 arginine 337 methylation in endometrial epithelial cell receptivity

A successful embryo implantation relies heavily on the receptivity of the endometrial epithelium, a process regulated by various molecular mechanisms. Evaluating endometrial receptivity in infertility patients undergoing assisted reproductive treatment, particularly those with adenomyosis related infertility, poses significant challenges due to limitations associated with conventional assessment methods. In this study, we collected residual endometrial epithelial cells from the tips of embryo transfer catheters in patients with adenomyosis related infertility. High throughput sequencing revealed a marked downregulation of protein arginine methyltransferase 5 (PRMT5) in these cells. Functional assays demonstrated that PRMT5 interacts with and methylates homeobox A10 (HOXA10), a crucial transcription factor for endometrial receptivity and implantation. The methylation of HOXA10 at arginine 337 by PRMT5 enhances its stability and promotes the transcriptional activation of genes essential for endometrial differentiation and adhesion. The downregulation of PRMT5 led to decreased HOXA10 activity, resulting in impaired endometrial receptivity and subsequent implantation failure. These findings elucidate a critical pathway where PRMT5 downregulation negatively impacts HOXA10 function, providing new insights into the molecular mechanisms underlying implantation failure in adenomyosis related infertility. This study not only advances our understanding of the regulatory mechanisms governing endometrial receptivity but also identifies potential therapeutic targets for enhancing endometrial function in affected patients.

Enhanced purification of uterine smooth muscle cells from adenomyosis using a novel dual-enzyme digestion method

Uterine adenomyosis causing attention to the abnormal smooth muscle layer has recently received increasing attention, which has created the need for a method that can efficiently collect high purity uterine smooth muscle cells (USMC) in a laboratory setting. In this study, we explored the composition ratios of the digestion solution to obtain the optimal digestion solution (DM4). Furthermore, we tested the superiority of the two methods of obtaining adenomyotic uterine smooth muscle by comparing DM4 with the conventional tissue adhesion method by growth rate, single-cell RNA sequencing, and purity of fluorescence identification. The results demonstrated that USMCs produced by the DM4 digestion method exhibited significantly higher rates of proliferation and were more effective in generating mature smooth muscle cells of high purity compared to those obtained using tissue adherence methods, which is more inclined to isolate the progenitor cell population. This study presents a reliable method for isolating USMCs and provides a solid foundation for future studies on the etiology and mechanism of adenomyosis.