Adenomyosis in mice resulting from mechanically or thermally induced endometrial–myometrial interface disruption and its possible prevention

Hypermethylation of Klotho and Peroxisome Proliferator-Activated Receptor γ Concomitant with Overexpression of DNA Methyltransferase 1 in Adenomyosis

Cellular senescence is known to be involved in tissue repair, but its role in adenomyosis remains unclear. This study was tasked to evaluate the expression of Klotho, a well-known aging-suppressing protein, as well as PPARγ and DNMT1 in adenomyotic lesions (AD) in comparison with that of control endometrium (CT). We performed immunohistochemistry analysis of markers of cellular senescence p16 and p21, along with Klotho, PPARγ and DNMT1 in CT and AD samples, followed by the quantification of gene expression of Klotho, PPARγ and DNMT1 in epithelial organoids derived from AD and CT samples and methylation-specific PCR to evaluate promoter methylation status. The effect of forced expression and knockdown of DNMT1 on Klotho and PPARγ expression in ectopic endometrial epithelial cells was evaluated. We found that both p16 and p21 immunoreactivity in AD was significantly higher while that of Klotho and PPARγ was significantly lower than CT samples, which was concomitant with elevated immunoexpression of DNMT1. The results were confirmed by transcriptional analysis using epithelial organoids derived from AD and CT samples. In addition, the promoter regions of both Klotho and PPARγ genes were hypermethylated in AD as compared with CT, and treatment with HDAC and DNMT inhibitors reactivated the expression of both Klotho and PPARγ. Forced expression of DNMT1 resulted in downregulation of both Klotho and PPARγ but its knockdown increased their expression. Thus, overexpression of DNMT1 seems to facilitate the promoter hypermethylation of both Klotho and PPARγ in AD, resulting in their reduced expression that is suggestive of the role of senescence in adenomyosis.

Meclizine improves endometrial repair and reduces simulated menstrual bleeding in mice with induced adenomyosis

BACKGROUND

Adenomyosis is one of the structural causes of abnormal uterine bleeding, which often presents as heavy menstrual bleeding. Mostly because of the poor understanding of its pathophysiology, medical management of adenomyosis-induced heavy menstrual bleeding is still a challenge. We have previously reported that glycolysis is crucial to endometrial repair following menstruation and that suppressed glycolysis can cause heavy menstrual bleeding.

OBJECTIVE

This study aimed to test the hypothesis that meclizine, a drug with an excellent safety profile, alleviates heavy menstrual bleeding in mice with induced adenomyosis using a simulated menstruation model.

STUDY DESIGN

Adenomyosis was induced in 36 female C57BL/6 mice using endometrial-myometrial interface disruption. Three months after induction, the mice were randomly divided into the following 3 groups: low-dose meclizine, high-dose meclizine, and controls. Treatment with meclizine or vehicle started shortly before the simulated menstruation procedure and ended before progesterone withdrawal. The amount of blood loss was quantified and uterine tissue was harvested for histologic evaluation of the grade of endometrial repair. We performed immunohistochemistry analysis of 4 proteins critically involved in glycolysis: Glut1 (glucose transporter 1), Hk2 (hexokinase 2), Pfkfb3 (6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3), and Pkm2 (pyruvate kinase M2). The extent of tissue fibrosis in both ectopic and eutopic endometria was evaluated using Masson trichrome staining.

RESULTS

In mice with induced adenomyosis, meclizine accelerated endometrial repair in a dose-dependent manner and reduced the amount of menstrual bleeding. Meclizine administration raised endometrial immunoexpression of Hk2 and Pfkfb3 but not of Glut1 or Pkm2. The extent of endometrial fibrosis was reduced following the meclizine administration. Remarkably, these favorable changes were accompanied by the suppression of lesional progression, as evidenced by the dose-dependent reduction in the extent of fibrosis (a surrogate for lesional progression).

CONCLUSION

These encouraging results, taken together, suggest that glycolysis may be a promising therapeutic target and that meclizine may hold therapeutic potential as a nonhormonal treatment for adenomyosis-induced heavy menstrual bleeding without exacerbating the disease.

Establishment of an immortalized cell line derived from human adenomyosis ectopic lesions

Because adenomyosis (AM) ectopic primary cells are hard to come by, have a short lifespan, and the characteristics that alter over time, their utility in AM research is constrained. This study aimed to establish a line of immortalized human adenomyosis ectopic cell (ihAMEC) to change this situation. Primary cells were obtained from AM ectopic lesion tissue and then infected with Simian Vacuolating Virus 40 Tag (SV40 T) lentivirus and screened to establish immortalized cells. We verified the main features and found that the ihAMEC could be cultured for more than 50 generations and the proliferation ability of ihAMEC was more active than that of primary cells. The cytoskeleton and cell types of ihAMEC were similar to primary cells and maintained a normal karyotype. The expression of epithelial-mesenchymal transition (EMT) markers, estrogen-metabolizing proteins, and estrogen/progesterone receptors in ihAMEC was similar to the expression seen in primary cells. In addition, the response of ihAMEC under estrogen treatment and Lipopolysaccharide intervention is similar to primary cells. The clonogenic ability of ihAMEC was lower than tumor cells and did not form tumors in tumorigenicity assays. Thus, ihAMEC can be used as in vitro cellular model for pathogenesis and drug development studies regarding AM.

Are Adenomyosis and Endometriosis Phenotypes of the Same Disease Process?

In recent literature reviews, we concluded that the possibility that endometrial molecular aberrations are the sole or a necessary determinant of endometriosis and the Tissue Injury and Repair (TIAR) theory are yet to be convincingly proven. Here, we critically examine the theory that adenomyosis and endometriosis represent different phenotypes of a single disease. A common etiopathology for adenomyosis and endometriosis has been suggested because both conditions entail the presence of endometrial tissue at locations other than the lining of the uterus. There are wide differences in reported disease incidence and prevalence and, consequently, in estimates of the coexistence of both conditions. There are some similarities but also differences in their clinical features and predisposing factors. Each condition has a range of subtypes. These differences alone pose the question of whether subtypes of endometriosis and adenomyosis have different etiopathologies, and, in turn, this raises the question of whether they all share a common etiology. It is debatable whether the recognized differences between the eutopic endometrium in adenomyosis and endometriosis compared to those in unaffected women are the cause or the effect of the disease. The finding of common mutations, particularly of KRAS, lend support to the notion of shared predisposing factors, but this alone is insufficient evidence of causation.

Reduced endometrial expression of histone deacetylase 3 in women with adenomyosis who complained of heavy menstrual bleeding

RESEARCH QUESTION

What role, if any, does histone deacetylase 3 (HDAC3) play in adenomyosis-associated heavy menstrual bleeding (HMB)?

DESIGN

Seventy-two women with adenomyosis-associated HMB were recruited. Of these, 37 women reported moderate/heavy bleeding (MHB) and the remaining 35 women reported excessive bleeding (EXB). The stiffness of adenomyotic lesions and neighbouring endometrial-myometrial interface (EMI) was measured by transvaginal elastosonography, and full-thickness uterine tissue columns were processed for Masson trichrome staining and immunohistochemistry analyses. The protein expression levels of HDAC3 in endometrial cells cultured on substrates of different stiffnesses, and the protein concentrations of nuclear factor-κB (NF-κB) p65 subunit with HDAC3 suppression were evaluated. Mouse experiments were performed to assess the effect of adenomyosis on Hdac3 expression, endometrial repair and bleeding, and to evaluate the effect of HDAC3 inhibition on endometrial repair.

RESULTS

Compared with controls, the endometrial staining of HDAC3 was significantly lower in women with adenomyosis-associated HMB, concomitant with a greater extent of fibrosis. The stiffness of lesions and neighbouring EMI was significantly higher in the EXB group compared with the MHB group, as was the extent of fibrosis in lesions, their neighboring EMI and endometrium. Expression of HDAC3 was reduced significantly when endometrial epithelial cells were cultured in stiff substrates. Suppression of HDAC3 abrogated the activation and signalling of NF-κB. Mice with induced adenomyosis exhibited reduced Hdac3 staining and elevated fibrosis in endometrium, concomitant with disrupted endometrial repair and more bleeding. Hdac3 inhibition resulted in botched inflammation and increased bleeding.

CONCLUSIONS

Lesional fibrosis results in reduced endometrial HDAC3 expression and subsequent disruption in NF-κB signalling and inflammation, leading to adenomyosis-associated HMB.

Shorter Anogenital Distance in Women with Ovarian Endometriomas and Adenomyosis, but Not Uterine Leiomyomas

We investigated whether anogenital distance (AGD) is associated with adenomyosis, endometriosis and uterine leiomyomas (UL, also called uterine fibroids). We recruited 81 women with UL, 105 with ovarian endometrioma (OE), 116 with adenomyosis, 28 with both adenomyosis and UL, and 100 control subjects with other acquired gynecological conditions but not endometriosis, adenomyosis, UL, or polycystic ovarian syndrome. Measurements from the anterior clitoral surface to the center of the anus (AGDAC), from the tip of the clitoris to the center of the anus (AGDACt), and from the posterior fourchette to the center of the anus (AGDAF) were made in all subjects. Multiple regression was performed to estimate the association between AGDs and presence of OE, adenomyosis, and UL while controlling for possible confounding factors. We found that, compared with controls, women with OE and adenomyosis, but not UL, had significantly shorter AGDAF, but not AGDAC. However, the amount of variance that could be explained by the disease status is rather moderate, suggesting that factors other than disease status, bodyweight and height were also responsible for AGD. Thus, prenatal exposure to reduced levels of androgen may increase the risk of developing endometriosis and adenomyosis. However, other factors may also contribute to the pathogenesis of endometriosis and adenomyosis.

Cyclic processes in the uterine tubes, endometrium, myometrium, and cervix: pathways and perturbations

This review leads the 2023 Call for Papers in MHR: 'Cyclical function of the female reproductive tract' and will outline the complex and fascinating changes that take place in the reproductive tract during the menstrual cycle. We will also explore associated reproductive tract abnormalities that impact or are impacted by the menstrual cycle. Between menarche and menopause, women and people who menstruate living in high-income countries can expect to experience ∼450 menstrual cycles. The primary function of the menstrual cycle is to prepare the reproductive system for pregnancy in the event of fertilization. In the absence of pregnancy, ovarian hormone levels fall, triggering the end of the menstrual cycle and onset of menstruation. We have chosen to exclude the ovaries and focus on the other structures that make up the reproductive tract: uterine tubes, endometrium, myometrium, and cervix, which also functionally change in response to fluctuations in ovarian hormone production across the menstrual cycle. This inaugural paper for the 2023 MHR special collection will discuss our current understanding of the normal physiological processes involved in uterine cyclicity (limited specifically to the uterine tubes, endometrium, myometrium, and cervix) in humans, and other mammals where relevant. We will emphasize where knowledge gaps exist and highlight the impact that reproductive tract and uterine cycle perturbations have on health and fertility.

The Role of Platelets in the Pathogenesis and Pathophysiology of Adenomyosis

Widely viewed as an enigmatic disease, adenomyosis is a common gynecological disease with bewildering pathogenesis and pathophysiology. One defining hallmark of adenomyotic lesions is cyclic bleeding as in eutopic endometrium, yet bleeding is a quintessential trademark of tissue injury, which is invariably followed by tissue repair. Consequently, adenomyotic lesions resemble wounds. Following each bleeding episode, adenomyotic lesions undergo tissue repair, and, as such, platelets are the first responder that heralds the subsequent tissue repair. This repeated tissue injury and repair (ReTIAR) would elicit several key molecular events crucial for lesional progression, eventually leading to lesional fibrosis. Platelets interact with adenomyotic cells and actively participate in these events, promoting the lesional progression and fibrogenesis. Lesional fibrosis may also be propagated into their neighboring endometrial-myometrial interface and then to eutopic endometrium, impairing endometrial repair and causing heavy menstrual bleeding. Moreover, lesional progression may result in hyperinnervation and an enlarged uterus. In this review, the role of platelets in the pathogenesis, progression, and pathophysiology is reviewed, along with the therapeutic implication. In addition, I shall demonstrate how the notion of ReTIAR provides a much needed framework to tether to and piece together many seemingly unrelated findings and how it helps to make useful predictions.

Cracking the enigma of adenomyosis: an update on its pathogenesis and pathophysiology

In brief

Traditionally viewed as enigmatic and elusive, adenomyosis is a fairly common gynecological disease but is under-recognized and under-researched. This review summarizes the latest development on the pathogenesis and pathophysiology of adenomyosis, which have important implications for imaging diagnosis of the disease and for the development of non-hormonal therapeutics.

Abstract

Traditionally considered as an enigmatic disease, adenomyosis is a uterine disease that affects many women of reproductive age and is a contributing factor for pelvic pain, heavy menstrual bleeding (HMB), and subfertility. In this review, the new development in the pathogenesis and pathophysiology of adenomyosis has been summarized, along with their clinical implications. After reviewing the progress in our understanding of the pathogenesis and describing the prevailing theories, in conjunction with their deficiencies, a new hypothesis, called endometrial-myometrial interface disruption (EMID), which is backed by extensive epidemiologic data and demonstrated by a mouse model, is reviewed, along with recent data implicating the role of Schwann cells in the EMI area in the genesis of adenomyosis. Additionally, the natural history of adenomyotic lesions is elaborated and underscores that, in essence, adenomyotic lesions are fundamentally wounds undergoing repeated tissue injury and repair (ReTIAR), which progress to fibrosis through epithelial-mesenchymal transition, fibroblast-to-myofibroblast transdifferentiation, and smooth muscle metaplasia. Increasing lesional fibrosis propagates into the neighboring EMI and endometrium. The increased endometrial fibrosis, with ensuing greater tissue stiffness, results in attenuated prostaglandin E2, hypoxia signaling and glycolysis, impairing endometrial repair and causing HMB. Compared with adenomyosis-associated HMB, the mechanisms underlying adenomyosis-associated pain are less understood but presumably involve increased uterine contractility, hyperinnervation, increased lesional production of pain mediators, and central sensitization. Viewed through the prism of ReTIAR, a new imaging technique can be used to diagnose adenomyosis more accurately and informatively and possibly help to choose the best treatment modality.

Establishment of a novel mouse model of adenomyosis suitable for longitudinal and quantitative analysis and perinatal outcome studies

The purpose of this study was to establish a novel mouse model of adenomyosis suitable for longitudinal and quantitative analyses and perinatal outcome studies. Using a 30 G needle, the entire uterine wall of one horn was mechanically punctured at a frequency of 100 times/1 cm (adenomyosis horn). The other horn was left unpunctured (control horn). Balb/c mice were sacrificed on day 14 (D14) or day 65 (D65) (n = 3 each). The uterus was fixed, paraffin-embedded, sliced, and stained. Lesions were detected and counted, and their volumes were measured. Cell proliferation and fibrosis were assessed by Ki67 and Masson's Trichrome staining, respectively. Blood vessels were detected using CD31 immunostaining. Some of the mice (n = 4), were mated and the date of delivery, litter size, number of implantations, and number and volume of postpartum lesions were measured. The number of lesions per horn did not differ between D14 and D65. The volume of the entire lesion was significantly greater on D65 than on D14 (p < 0.0001). The volume of the epithelial part of the lesion was significantly greater in D65 (p < 0.0001). The volume of the stromal part of the lesion was also greater on D65 (p < 0.0001). The percentage of Ki67 positive cells in the epithelial part of the lesion was significantly higher on D14 (p < 0.05). In contrast, the percentage of Ki67-positive cells in the stromal part was significantly higher on D65 (p < 0.01). Vascular density in the lesions was higher in on D65 (p < 0.05). The percentage of fibrotic area was significantly higher on D65 (p < 0.01). The date of delivery was slightly earlier than that reported for healthy mice of the same strain. The litter size was smaller than that reported in previous research. The number of implantation sites did not differ between the control and the adenomyosis horn. The number and volume of lesions did not differ between the non-pregnant and postpartum groups. This model can be applied to evaluate the pathogenesis of adenomyosis, validate the efficacy of therapeutic agents, and evaluate the effect of adenomyosis on pregnancy and vice versa.

Pre-clinical models to study abnormal uterine bleeding (AUB)

Abnormal Uterine Bleeding (AUB) is a common debilitating condition that significantly reduces quality of life of women across the reproductive age span. AUB creates significant morbidity, medical, social, and economic problems for women, their families, workplace, and health services. Despite the profoundly negative effects of AUB on public health, advancement in understanding the pathophysiology of AUB and the discovery of novel effective therapies is slow due to lack of reliable pre-clinical models. This review discusses currently available laboratory-based pre-clinical scientific models and how they are used to study AUB. Human and animal in vitro, ex vivo, and in vivo models will be described along with advantages and limitations of each method.

Perioperative Suppression of Schwann Cell Dedifferentiation Reduces the Risk of Adenomyosis Resulting from Endometrial–Myometrial Interface Disruption in Mice

We have recently demonstrated that endometrial–myometrial interface (EMI) disruption (EMID) can cause adenomyosis in mice, providing experimental evidence for the well-documented epidemiological finding that iatrogenic uterine procedures increase the risk of adenomyosis. To further elucidate its underlying mechanisms, we designed this study to test the hypothesis that Schwann cells (SCs) dedifferentiating after EMID facilitate the genesis of adenomyosis, but the suppression of SC dedifferentiation perioperatively reduces the risk. We treated mice perioperatively with either mitogen-activated protein kinase kinase (MEK)/extracellular-signal regulated protein kinase (ERK) or c-Jun N-terminal kinase (JNK) inhibitors or a vehicle 4 h before and 24 h, 48 h and 72 h after the EMID procedure. We found that EMID resulted in progressive SCs dedifferentiation, concomitant with an increased abundance of epithelial cells in the myometrium and a subsequent epithelial–mesenchymal transition (EMT). This EMID-induced change was abrogated significantly with perioperative administration of JNK or MEK/ERK inhibitors. Consistently, perioperative administration of a JNK or a MEK/ERK inhibitor reduced the incidence by nearly 33.5% and 14.3%, respectively, in conjunction with reduced myometrial infiltration of adenomyosis and alleviation of adenomyosis-associated hyperalgesia. Both treatments significantly decelerated the establishment of adenomyosis and progression of EMT, fibroblast-to-myofibroblast trans-differentiation and fibrogenesis in adenomyotic lesions. Thus, we provide the first piece of evidence strongly implicating the involvement of SCs in the pathogenesis of adenomyosis induced by EMID.

Unveiling the Pathogenesis of Adenomyosis through Animal Models

Background: Adenomyosis is a common gynecological disorder traditionally viewed as “elusive”. Several excellent review papers have been published fairly recently on its pathogenesis, and several theories have been proposed. However, the falsifiability, explanatory power, and predictivity of these theories are often overlooked. Since adenomyosis can occur spontaneously in rodents and many other species, the animal models may help us unveil the pathogenesis of adenomyosis. This review critically tallies experimentally induced models published so far, with a particular focus on their relevance to epidemiological findings, their possible mechanisms of action, and their explanatory and predictive power. Methods: PubMed was exhaustively searched using the phrase “adenomyosis and animal model”, “adenomyosis and experimental model”, “adenomyosis and mouse”, and “adenomyosis and rat”, and the resultant papers were retrieved, carefully read, and the resultant information distilled. All the retrieved papers were then reviewed in a narrative manner. Results: Among all published animal models of adenomyosis, the mouse model of adenomyosis induced by endometrial–myometrial interface disruption (EMID) seems to satisfy the requirements of falsifiability and has the predictive capability and also Hill’s causality criteria. Other theories only partially satisfy Hill’s criteria of causality. In particular, animal models of adenomyosis induced by hyperestrogenism, hyperprolactinemia, or long-term exposure to progestogens without much epidemiological documentation and adenomyosis is usually not the exclusive uterine pathology consequent to those induction procedures. Regardless, uterine disruption appears to be a necessary but not sufficient condition for causing adenomyosis. Conclusions: EMID is, however, unlikely the sole cause for adenomyosis. Future studies, including animal studies, are warranted to understand how and why in utero and/or prenatal exposure to elevated levels of estrogen or estrogenic compounds increases the risk of developing adenomyosis in adulthood, to elucidate whether prolactin plays any role in its pathogenesis, and to identify sufficient condition(s) that cause adenomyosis.

Mechanisms and Pathogenesis of Adenomyosis

Purpose of the Review

The purpose of this review is to provide a synopsis of all the mechanisms involved in the pathogenesis of adenomyosis. It will summarize recent advances in the field, discussing current controversies, and considering potential future directions.

Recent Findings

Adenomyosis pathogenesis is still a topic under investigation, however advancements in the understanding of disease development and mechanisms have been made. New data coming from new next generation sequencing-based studies and more-in-depth acquisitions on sex hormones imbalance, neuroangiogenesis, inflammation, fibrosis and cell proliferation have been obtained.

Summary

Adenomyosis is a uterine disorder that affects women of reproductive age, characterized by a benign invasion of the endometrium basalis (glands and stroma) within the myometrium.

So far, three theories for the pathophysiology of adenomyosis have been proposed:

In order to invade and develop, endometrial cells require a series of pathogenetic mechanisms which drive to adenomyosis. Altered sex steroids hormones receptors may be the primary event which causes increased endometrial cell proliferations and differentiation from epithelial to mesenchymal cells. Once invaded the myometrium, an inflammatory reaction is displayed, probably driven by local immune changes. The processes of neuroangiogenesis and fibrosis are also involved in the adenomyosis development and may explain some of the associated clinical symptoms (dysmenorrhea, abnormal uterine bleeding, and infertility).

How does the extent of fibrosis in adenomyosis lesions contribute to heavy menstrual bleeding?

Purpose

To investigate how the extent of fibrosis in adenomyosis lesions contributes to heavy menstrual bleeding (HMB).

Methods

We recruited 57 women with histologically confirmed adenomyosis, 29 of whom reported moderate/heavy bleeding (MHB) (menstrual blood loss (MBL) ≥20 but <100 mL) and the remaining 28, excessive MBL (EXB; ≥100 mL). Lesional stiffness was measured by transvaginal elastosonography. Full‐thickness uterine tissue columns containing the lesion and its neighboring endometrial‐myometrial interface (EMI) and endometrial tissues were evaluated for tissue fibrosis and immunohistochemical analysis of HIF‐1α, COX‐2, EP2, and EP4.

Results

The lesional stiffness in the EXB group was significantly higher than that of MHB, and consistently, the extent of lesional fibrosis and the extent of tissue fibrosis in both EMI and eutopic endometrium were also significantly higher. In adenomyotic lesions and their neighboring EMI and eutopic endometrial tissues, the immunostaining of HIF‐1α, COX‐2, EP2, and EP4 was significantly reduced. The extent of fibrosis and the immunostaining levels of HIF‐1α, COX‐2, EP2, and EP4 were negatively correlated in all tissues.

Conclusions

Lesional fibrosis begets stiffening matrix, propagating fibrosis to neighboring EMI and eutopic endometrium, resulting in reduced PGE₂ and HIF‐1α signaling, and thus likely reduced hypoxia necessary for endometrial repair, leading to HMB.

The Menstrual Endometrium: From Physiology to Future Treatments

Abnormal uterine bleeding (AUB) is experienced by up to a third of women of reproductive age. It can cause anaemia and often results in decreased quality of life. A range of medical and surgical treatments are available but are associated with side effects and variable effectiveness. To improve the lives of those suffering from menstrual disorders, delineation of endometrial physiology is required. This allows an increased understanding of how this physiology may be disturbed, leading to uterine pathologies. In this way, more specific preventative and therapeutic strategies may be developed to personalise management of this common symptom. In this review, the impact of AUB globally is outlined, alongside the urgent clinical need for improved medical treatments. Current knowledge of endometrial physiology at menstruation is discussed, focusing on endocrine regulation of menstruation and local endometrial inflammation, tissue breakdown, hypoxia and endometrial repair. The contribution of the specialised endometrial vasculature and coagulation system during menstruation is highlighted. What is known regarding aberrations in endometrial physiology that result in AUB is discussed, with a focus on endometrial disorders (AUB-E) and adenomyosis (AUB-A). Gaps in existing knowledge and areas for future research are signposted throughout, with a focus on potential translational benefits for those experiencing abnormal uterine bleeding. Personalisation of treatment strategies for menstrual disorders is then examined, considering genetic, environmental and demographic characteristics of individuals to optimise their clinical management. Finally, an ideal model of future management of AUB is proposed. This would involve targeted diagnosis of specific endometrial aberrations in individuals, in the context of holistic medicine and with due consideration of personal circumstances and preferences.

Novel microarchitecture of human endometrial glands: implications in endometrial regeneration and pathologies

BACKGROUND

Human endometrium remains a poorly understood tissue of the female reproductive tract. The superficial endometrial functionalis, the site of embryo implantation, is repeatedly shed with menstruation, and the stem cell-rich deeper basalis is postulated to be responsible for the regeneration of the functionalis. Two recent manuscripts have demonstrated the 3D architecture of endometrial glands. These manuscripts have challenged and replaced the prevailing concept that these glands end in blind pouches in the basalis layer that contain stem cells in crypts, as in the intestinal mucosa, providing a new paradigm for endometrial glandular anatomy. This necessitates re-evaluation of the available evidence on human endometrial regeneration in both health and disease in the context of this previously unknown endometrial glandular arrangement.

OBJECTIVE AND RATIONALE

The aim of this review is to determine if the recently discovered glandular arrangement provides plausible explanations for previously unanswered questions related to human endometrial biology. Specifically, it will focus on re-appraising the theories related to endometrial regeneration, location of stem/progenitor cells and endometrial pathologies in the context of this recently unravelled endometrial glandular organization.

SEARCH METHODS

An extensive literature search was conducted from inception to April 2021 using multiple databases, including PubMed/Web of Science/EMBASE/Scopus, to select studies using keywords applied to endometrial glandular anatomy and regeneration, and the references included in selected publications were also screened. All relevant publications were included.

OUTCOMES

The human endometrial glands have a unique and complex architecture; branched basalis glands proceed in a horizontal course adjacent to the myometrium, as opposed to the non-branching, vertically coiled functionalis glands, which run parallel to each other as is observed in intestinal crypts. This complex network of mycelium-like, interconnected basalis glands is demonstrated to contain endometrial epithelial stem cells giving rise to single, non-branching functionalis glands. Several previous studies that have tried to confirm the existence of epithelial stem cells have used methodologies that prevent sampling of the stem cell-rich basalis. More recent findings have provided insight into the efficient regeneration of the human endometrium, which is preferentially evolved in humans and menstruating upper-order primates.

WIDER IMPLICATIONS

The unique physiological organization of the human endometrial glandular element, its relevance to stem cell activity and scarless endometrial regeneration will inform reproductive biologists and clinicians to direct their future research to determine disease-specific alterations in glandular anatomy in a variety of endometrial pathological conditions.

Mode Switch of Ca2 + Oscillation-Mediated Uterine Peristalsis and Associated Embryo Implantation Impairments in Mouse Adenomyosis

Adenomyosis is a debilitating gynecological disease of the uterus with no medicinal cure. The tissue injury and repair hypothesis for adenomyosis suggests that uterine hyperperistalsis or dysperistalsis plays a pivotal role in establishing adenomyotic lesions. However, specific impairments in uterine peristalsis and the underlying cellular signals for these changes in adenomyosis remain elusive. Here, we report a precision-cut uterine slice preparation that preserves in vivo uterine architecture and generates peristalsis similar to that seen in the whole uterus. We found that uterine peristalsis in neonatal mice at day 14 and adult mice at day 55 presents as bursts with multiple peaks induced by intracellular Ca²⁺ oscillations. Using a mouse model of adenomyosis induced by tamoxifen, a selective estrogen receptor modulator, we discovered that uterine peristalsis and Ca²⁺ oscillations from adenomyotic uteri on days 14 and 55 become spikes (single peaks) with smaller amplitudes. The peak frequency of Ca²⁺ oscillations or peristalsis does not show a difference between control and adenomyotic mice. However, both the estimated force generated by uterine peristalsis and the total Ca²⁺ raised by Ca²⁺ oscillations are smaller in uteri from adenomyotic mice. Uteri from adenomyotic mice on day 14, but not on day 55, exhibit hyperresponsiveness to oxytocin. Embryo implantations are decreased in adenomyotic adult mice. Our results reveal a mode switch from bursts to spikes (rather than an increased peak frequency) of uterine Ca²⁺ oscillations and peristalsis and concurrent hyperresponsiveness to oxytocin in the neonatal stage are two characteristics of adenomyosis. These characteristics may contribute to embryo implantation impairments and decreased fertility in adenomyosis.

Preoperative and perioperative intervention reduces the risk of recurrence of endometriosis in mice caused by either incomplete excision or spillage and dissemination

RESEARCH QUESTION

Can preoperative or perioperative intervention reduce the risk of recurrence of endometriosis caused by either incomplete excision or spillage and dissemination?

DESIGN

A mouse model of endometriosis recurrence caused by spillage and dissemination was first established using 24 female Balb/c mice. The spillage and dissemination model was used to test the efficacy of preoperative use of ketorolac, perioperative use of aprepitant and combined use of propranolol and andrographolide in a prospective, randomized mouse experiment involving 75 mice. The efficacy of these preoperative and perioperative interventions in a mouse recurrence model caused by incomplete excision was also tested using 72 mice. In all experiments, the baseline body weight and hotplate latency of all mice were measured and recorded before the induction of endometriosis, before the primary surgery and before sacrifice. In addition, all lesions were excised, weighed and processed for quantification and immunohistochemistry analysis of E-cadherin, α-SMA, VEGF, ADRB2 and putative markers of recurrence PR-B, p-p65, as well as Masson trichrome staining.

RESULTS

All interventions substantially and significantly suppressed the outgrowth of endometriotic lesions and reduced the risk of recurrence caused by either spillage and dissemination or incomplete excision (P = 0.0007 to 0.042). These interventions also significantly attenuated the generalized hyperalgesia, inhibited the staining of α-SMA, p-p65, VEGF and ADRB2 but increased staining of E-cadherin and PR-B, resulting in reduced fibrosis.

CONCLUSION

Given the excellent safety profiles of these drugs, these data strongly suggest that preoperative and perioperative intervention may potentially reduce the risk of endometriosis recurrence effectively.

Possible involvement of neuropeptide and neurotransmitter receptors in Adenomyosis

BACKGROUND

Accumulating data indicate that sensory nerve derived neuropeptides such as substance P and calcitonin gene related-protein (CGRP) can accelerate the progression of endometriosis via their respective receptors, so can agonists to their respective receptors receptor 1 (NK1R), receptor activity modifying protein 1 (RAMP-1) and calcitonin receptor-like receptor (CRLR). Adrenergic β2 receptor (ADRB2) agonists also can facilitate lesional progression. In contrast, women with endometriosis appear to have depressed vagal activity, concordant with reduced expression of α7 nicotinic acetylcholine receptor (α7nAChR). The roles of these receptors in adenomyosis are completely unknown.

METHODS

Adenomyotic tissue samples from 30 women with adenomyosis and control endometrial tissue samples from 24 women without adenomyosis were collected and subjected to immunohistochemistry analysis of RAMP1, CRLR, NK1R, ADRB2 and α7nAChR, along with their demographic and clinical information. The extent of tissue fibrosis was evaluated by Masson trichrome staining.

RESULTS

We found that the staining levels of NK1R, CRLR, RAMP1 and ADRB2 were all significantly elevated in adenomyotic lesions as compared with control endometrium. In contrast, α7nAChR staining levels were significantly reduced. The severity of dysmenorrhea correlated positively with lesional ADRB2 staining levels.

CONCLUSIONS

Our results suggest that SP, CGRP and noradrenaline may promote, while acetylcholine may stall, the progression of adenomyosis through their respective receptors on adenomyotic lesions. Additionally, through the activation of the hypothalamic-pituitary-adrenal (HPA)-sympatho-adrenal-medullary (SAM) axes and the lesional overexpression of ADRB2, adenomyosis-associated dysmenorrhea and adenomyotic lesions may be mutually promotional, forming a viscous feed-forward cycle.