Changing prostaglandin E2 (PGE2) signaling during lesional progression and exacerbation of endometriosis by inhibition of PGE2 receptor EP2 and EP4

The role of fibrosis in endometriosis: a systematic review

BACKGROUND

Fibrosis is an important pathological feature of endometriotic lesions of all subtypes. Fibrosis is present in and around endometriotic lesions, and a central role in its development is played by myofibroblasts, which are cells derived mainly after epithelial-to-mesenchymal transition (EMT) and fibroblast-to-myofibroblast transdifferentiation (FMT). Transforming growth factor-β (TGF-β) has a key role in this myofibroblastic differentiation. Myofibroblasts deposit extracellular matrix (ECM) and have contracting abilities, leading to a stiff micro-environment. These aspects are hypothesized to be involved in the origin of endometriosis-associated pain. Additionally, similarities between endometriosis-related fibrosis and other fibrotic diseases, such as systemic sclerosis or lung fibrosis, indicate that targeting fibrosis could be a potential therapeutic strategy for non-hormonal therapy for endometriosis.

OBJECTIVE AND RATIONALE

This review aims to summarize the current knowledge and to highlight the knowledge gaps about the role of fibrosis in endometriosis. A comprehensive literature overview about the role of fibrosis in endometriosis can improve the efficiency of fibrosis-oriented research in endometriosis.

SEARCH METHODS

A systematic literature search was performed in three biomedical databases using search terms for 'endometriosis', 'fibrosis', 'myofibroblasts', 'collagen', and 'α-smooth muscle actin'. Original studies were included if they reported about fibrosis and endometriosis. Both preclinical in vitro and animal studies, as well as research concerning human subjects were included.

OUTCOMES

Our search yielded 3441 results, of which 142 studies were included in this review. Most studies scored a high to moderate risk of bias according to the bias assessment tools. The studies were divided in three categories: human observational studies, experimental studies with human-derived material, and animal studies. The observational studies showed details about the histologic appearance of fibrosis in endometriosis and the co-occurrence of nerves and immune cells in lesions. The in vitro studies identified several pro-fibrotic pathways in relation to endometriosis. The animal studies mainly assessed the effect of potential therapeutic strategies to halt or regress fibrosis, for example targeting platelets or mast cells.

WIDER IMPLICATIONS

This review shows the central role of fibrosis and its main cellular driver, the myofibroblast, in endometriosis. Platelets and TGF-β have a pivotal role in pro-fibrotic signaling. The presence of nerves and neuropeptides is closely associated with fibrosis in endometriotic lesions, and is likely a cause of endometriosis-associated pain. The process of fibrotic development after EMT and FMT shares characteristics with other fibrotic diseases, so exploring similarities in endometriosis with known processes in diseases like systemic sclerosis, idiopathic pulmonary fibrosis or liver cirrhosis is relevant and a promising direction to explore new treatment strategies. The close relationship with nerves appears rather unique for endometriosis-related fibrosis and is not observed in other fibrotic diseases.

REGISTRATION NUMBER

N/A.

Endometriotic tissue fragments are viable after cryopreservation in an ex vivo tissue model recapitulating the fibrotic microenvironment

STUDY QUESTION

Is it possible to establish an ex vivo endometriosis model using cryopreserved endometriotic tissue fragments?

SUMMARY ANSWER

Cryopreserved endometriotic tissue fragments remain viable after thawing and during at least 3 days of culture and can therefore be used to establish an ex vivo endometriosis model to efficiently test potential therapeutic agents.

WHAT IS KNOWN ALREADY

Endometriosis is the most prevalent benign gynecologic disease with an enormous societal burden; however, curative therapies are still lacking. To efficiently test potential new therapies, an ex vivo model based on previously cryopreserved endometriotic tissue that recapitulates the different endometriosis subtypes and their microenvironment is highly desirable.

STUDY DESIGN, SIZE, DURATION

Endometriotic tissue fragments of three different subtypes were obtained from 28 patients by surgical resection. After cryopreservation and thawing, viability and metabolic activity of these tissue fragments were assessed. Viability was compared with fresh fragments from 11 patients directly after surgical removal. Experimental intervention studies were performed in cryopreserved and thawed tissue fragments from two patients to confirm the usability of these tissues for ex vivo intervention studies.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Endometriotic tissue fragments (n = 45) were cryopreserved according to three different protocols. After thawing, fragments were cultured for 24 h. A resazurin-based assay was performed to assess the metabolic activity of the tissue fragments. In addition, cell type-specific viability was analyzed by VivaFix, Hoechst 33342, and α-smooth muscle actin immunofluorescence staining and confocal microscopy. The presence of endometriosis was histologically confirmed based on hematoxylin-eosin staining. Cryopreserved and thawed tissue fragments were treated for 72 h with pirfenidone or metformin and COL1A1 and CEMIP gene expressions were assessed using RT-PCR and RT-qPCR, either in the whole tissue fragments or in myofibroblasts isolated by laser capture microdissection.

MAIN RESULTS AND THE ROLE OF CHANCE

Metabolic activity of endometriotic tissue fragments obtained from peritoneal (PER), ovarian (OMA), and deep (DE) endometriotic lesions was well preserved after cryopreservation in a dimethyl sulfoxide-based medium and was comparable with fresh tissue fragments. Relative metabolic activity compared to fresh tissue was 70% (CI: 92-47%) in PER, 43% (CI: 53-15%) in OMA and 94% (CI: 186-3%) in DE lesions. In fragments from PE lesions 92% (CI: 87-96%), from OMA lesions 95% (CI: 91-98%), and from DE lesions 88% (CI: 78-98%) of cells were viable after cryopreservation and thawing followed by a 24-h culture period. Differences in gene expression of fibrotic markers COL1A1 and CEMIP after 72-h treatment with pirfenidone or metformin could be detected in whole tissue fragments and in isolated myofibroblasts, indicating that cryopreserved and thawed endometriotic tissue fragments are suitable for testing anti-fibrotic interventions.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

Viability and metabolic activity of the endometriotic tissue fragments may have been partially compromised by damage sustained during the surgical procedure, contributing to inter-sample variance.

WIDER IMPLICATIONS OF THE FINDINGS

The storage of viable endometriotic tissue fragments for later usage in an ex vivo model creates the possibility to efficiently test potential new therapeutic strategies and facilitates the exchange of viable endometriotic tissue between different research laboratories.

STUDY FUNDING/COMPETING INTEREST(S)

This study was not financially supported by external funding. The authors declare no competing interest.

TRIAL REGISTRATION NUMBER

N/A.

Role of oxylipins in ovarian function and disease: A comprehensive review

Ovaries are essential for healthy female reproduction, with the follicles as their fundamental functional units, which consist of an oocyte and surrounding granulosa cells. The development and formation of follicles in the ovaries are closely linked to reproductive health. Oxylipins refer to oxidative metabolites produced from the oxidation of polyunsaturated fatty acids, either through automatic oxidation or with the help of specific enzymes. They play crucial regulatory roles in the immune system, oxidative stress, and inflammatory reactions and are intimately linked to the development of numerous illnesses, such as diabetes, heart disease, asthma, and Alzheimer's disease. Furthermore, oxylipins have a complex relationship with ovarian function, and both prostaglandins and leukotrienes produced by arachidonic acid affect processes such as follicle growth and development, ovulation, and hormone regulation. The synthesis and metabolism of oxylipins in the ovaries are finely regulated. Oxylipin dysregulation has been linked to various ovarian diseases, including endometriosis, polycystic ovary syndrome, ovarian cancer, and premature ovarian insufficiency. In addition, potential therapeutic targets and interventions targeting the oxylipin pathway for the treatment of ovarian diseases have become a prominent research focus, including regulating the enzymes responsible for oxylipin synthesis, using anti-inflammatory agents, and regulating lipid metabolism. Recent research has been directed towards improving the reproductive outcomes of women with ovarian diseases through this series of interventions. An overview of the role of oxylipins in ovarian function and disease is provided in this article, which will aid researchers in understanding the current state of the field and in identifying future directions.

Endometriosis: recent advances that could accelerate diagnosis and improve care

Endometriosis is a common disorder associated with pain, gastrointestinal and urinary symptoms, infertility, and fatigue. It is defined by the presence of endometrial-like lesions found predominantly in the pelvis. Mechanisms that contribute to disease aetiology include changes in hormonal, inflammatory, and pain pathways. In this article, we focus on recent developments in imaging technologies, on our improved understanding of mechanisms contributing to infertility, on drug therapies that are in clinical trials, and on insights from studies on the gut that offer potential to support self-management strategies. We postulate that improvements in the quality of life of patients will be accelerated by reframing endometriosis as a multi-system disorder and learning from treatments targeting symptoms shared between endometriosis, neuroinflammatory, and gastrointestinal disorders.

Progressively Diminished Prostaglandin E2 Signaling in Concordance with Increasing Fibrosis in Ectopic Endometrium

The prostaglandin E2 (PGE2) signaling has traditionally been viewed to play a pivotal role in endometriosis, linking inflammation and hyperestrogenism. We have previously reported that asectopic endometrium becomes more fibrotic, the expression of both COX-2 and PGE2 receptors (EP2 and EP4) are reduced. This study further investigatedwhether the expression levels of genes involved in the biosynthesis and metabolism of PGE2in ectopic endometrium diminish in concordance with increasing lesional fibrosis. We performed immunohistochemistry analyses of COX-2, mPGES-1, mPGES-2, cPGES, 15-PGDH, EP2 and EP4 and Masson trichrome staining for ovarian endometrioma (OE), adenomyosis (AD), and deep endometriosis (DE) tissue samples and control endometrial tissue samples (CT). Gene and protein expression analyses were performed by real-time RT-PCR and Western blotting, respectively. We found that as the extent of lesional fibrosis increased, immunoexpression of COX-2, mPGES-1/2, cPGES, EP2 and EP4 in OE lesions was increased but no change in these genes/proteins in DE lesions as compared with CT. Immunoexpression of COX-2 was found to be reduced while that of 15-PGDH was found to be elevated in DE lesions. In AD lesions, only EP2 and COX-2 were overexpressed. Thus, our data indicate that when the extent of lesional fibrosis is high, the PGE2 signaling pathway is depressed, manifesting as reduced COX-2 expression and elevated expression of 15-PGDH. They underscore the fact that not all ectopic endometria are the same and equal, and highlight the importance of the extracellular matrix in shaping the lesional behavior and response to drug treatment.

Reduced endometrial glycolysis concomitant with increased lesional fibrosis in patients with adenomyosis who complained of heavy menstrual bleeding

RESEARCH QUESTION

What role, if any, does the extent of lesional fibrosis play in impaired glycolysis leading to adenomyosis-associated heavy menstrual bleeding (ADM-HMB)?

DESIGN

Forty-eight patients with ADM-HMB were recruited, among them 25 reported moderate to heavy bleeding (MHB), and the remaining 23, excessive bleeding (EXB). The full-thickness uterine tissue columns were processed for Masson trichrome staining and immunohistochemistry analyses. The expression levels of HIF-1α, GLUT1, HK2, PFKFB3 and PKM2 proteins that are critically involved in glycolysis in endometrial epithelial cells cultured on substrates of different stiffness, and the levels of glycolysis were quantitated. A mouse experiment with induced adenomyosis and simulated menstrual bleeding was conducted to assess the effect of adenomyosis on immunoexpression of proteins involved in glycolysis and inflammation as well as on endometrial repair and bleeding.

RESULTS

The endometrial staining of HIF-1α, GLUT1, HK2, PFKFB3 and PKM2 was significantly lower in the EXB group as compared with MHB patients, concomitant with higher extent of fibrosis. The expression of HIF-1α, GLUT1, HK2, PFKFB3 and PKM2 was significantly reduced when endometrial epithelial cells were cultured in stiff substrate, concomitant with reduced glycolysis. Mice with induced adenomyosis had reduced immunoexpression of Hif-1α, as well as those proteins each of which plays a vital, rate-limiting role in different steps of the glycolysis pathway, such as Glut1, Hk2, Pfkfb3 and Pkm2, and elevated fibrosis in endometrium, concomitant with disrupted endometrial repair and more bleeding.

CONCLUSIONS

Lesional fibrosis results in reduced endometrial glycolysis in eutopic endometrium and subsequent imbalance in pro-inflammatory and anti-inflammatory response, leading to ADM-HMB.

Adenomyosis and Abnormal Uterine Bleeding: Review of the Evidence

BACKGROUND

Thomas Cullen described bleeding abnormalities and dysmenorrhea as the "expected" presentations of adenomyomas. Adenomyosis is included within the FIGO classification of structural causes of abnormal uterine bleeding (AUB). Nevertheless, this long-standing association has been questioned by some authors who reported a high incidence of adenomyosis in uteri removed for indications other than AUB or dysmenorrhea. Here, we examine evidence for the link between adenomyosis and AUB.

METHODS

A comprehensive Medline literature review of all publications to October 2023.

RESULTS

Sixty-three articles were identified and included in the review. Despite a large body of studies, the available literature does not provide conclusive evidence of a link between adenomyosis and AUB. This is because of unsuitable study design, or poor characterization of the study population or of the inclusion or exclusion criteria. Additional challenges arise because of the lack of agreed criteria for diagnosing adenomyosis and the often absence of detailed assessment of menstrual blood loss. Adenomyosis often coexists with other conditions that have also been linked to similar symptoms, and many cases of adenomyosis are asymptomatic.

CONCLUSION

Most of the existing literature and studies that addressed treatment outcome of adenomyosis started from the premise that a link between the condition and AUB had been proven. Yet, published information shows that aspects such a relationship is still uncertain. Further research is needed to address the relation between AUB and adenomyosis burden (or subtypes), distribution, and concomitant pathology.

Systematic review and meta-analysis of reproductive outcomes after high-intensity focused ultrasound (HIFU) treatment of adenomyosis

High-intensity focused ultrasound (HIFU) has emerged as a promising uterus-sparing and possibly fertility-sparing treatment modality for women with adenomyosis, especially those who desire to conceive. We conducted this systematic review and performed a meta-analysis on clinical studies aimed to improve reproduction in women with adenomyosis. After extensive search of PubMed and CNKI, we identified 10 studies published in English and Chinese involving a total of 557 patients with adenomyosis who desired to conceive after HIFU treatment. We found a pooled estimate of pregnancy rate of 53.4% and of the live birth rate of 35.2%, and there was a substantial heterogeneity among these studies. While there is a potential for HIFU treatment to improve fertility for patients with adenomyosis who desired to conceive, such evidence is very weak as of now. Comparative studies with much higher methodological rigor, preferably randomized clinical trials, are badly needed to further illuminate this issue.

Digestive system deep infiltrating endometriosis: What do we know

Digestive system infiltrating endometriosis (DSIE) is an uncommon form of endometriosis in the digestive system. DSIE often occurs in the intestines (especially the sigmoid rectum), liver, gallbladder and pancreas. Clinically, DSIE presents with the same symptoms as endometriosis, including cyclic pain, bleeding and infertility, in addition to specific biliary/intestinal obstruction and gastrointestinal bleeding. Compared to general endometriosis, DSIE has unique biological behaviour and pathophysiological mechanisms. Most DSIEs are deep invasive endometrioses, characterized by metastasis to the lymph nodes and lymphatic vessels, angiogenesis, peripheral nerve recruitment, fibrosis and invasion of surrounding tissues. DSIE-related peripheral angiogenesis is divided into three patterns: angiogenesis, vasculogenesis and inosculation. These patterns are regulated by interactions between multiple hypoxia-hormone cytokines. The nerve growth factors regulate the extensive neurofibril recruitment in DSIE lesions, which accounts for severe symptoms of deep pain. They are also associated with fibrosis and the aggressiveness of DSIE. Cyclic changes in DSIE lesions, recurrent inflammation and oxidative stress promote repeated tissue injury and repair (ReTIAR) mechanisms in the lesions, accelerating fibril formation and cancer-related mutations. Similar to malignant tumours, DSIE can also exhibit aggressiveness derived from collective cell migration mediated by E-cadherin and N-cadherin. This often makes DSIE misdiagnosed as a malignant tumour of the digestive system in clinical practice. In addition to surgery, novel treatments are urgently required to effectively eradicate this lesion.

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.

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.

Aberrant expression of histone deacetylase 8 in endometriosis and its potential as a therapeutic target

Purpose

To screen Zn2+-dependent histone deacetylase (HDAC) 1-11 in endometriotic cells and then evaluated the HDACs identified from the screening in ovarian endometrioma (OE) and deep endometriotic (DE) lesions, and to evaluate the therapeutic potential of HDAC8 inhibition in mice.

Methods

Quantification of gene and protein expression levels of HDAC1-11 in endometriotic cells stimulated by TGF-β1, and immunohistochemistry analysis of Class I HDACs and HDAC6 in OE/DE lesion samples. The therapeutic potential of HDAC8 inhibition was evaluated by a mouse model of deep endometriosis.

Results

The screening identified Class I HDACs and HDAC6 as targets of interest. Immunohistochemistry analysis found a significant elevation in HDAC8 immunostaining in both OE and DE lesions, which was corroborated by gene and protein expression quantification. For other Class I HDACs and HDAC6, their lesional expression was more subtle and nuanced. HDAC1 and HDAC6 staining was significantly elevated in DE lesions while HDAC2 and HDAC3 staining was reduced in DE lesions. Treatment of mice with induced deep endometriosis with an HDAC8 inhibitor resulted in significantly longer hotplate latency, a reduction of lesion weight by nearly two-thirds, and significantly reduced lesional fibrosis.

Conclusions

These findings highlight the progression-dependent nature of specific HDAC aberrations in endometriosis, and demonstrate, for the first titme, the therapeutic potential of suppressing HDAC8.

Corroborating evidence for aberrant expression of histone deacetylase 8 in endometriosis

Purpose

The aim of this study was to evaluate the dynamic change in staining of Class I HDACs and Hdac6 in lesions harvested serially from different time points in mice with induced endometriosis. In addition, the effect of Hdac8 activation as well as Hdac8 and Hdac6 inhibition on lesional progression and fibrogenesis was evaluated.

Methods

Immunohistochemistry analysis of Class I HDACs and Hdac6 in serially harvested lesion samples in mouse. Hdac8 activation, as well as Hdac6/8 inhibition, was evaluated in mice with induced endometriosis.

Results

We found a progressive increase in lesional staining of Hdac1, Hdac8, and Hdac6 and gradual decrease in Hdac2 staining and consistently reduced staining of Hdac3 during the course of lesional progression. The stromal Hdac8 staining correlated most prominently with all markers of lesional fibrosis. Hdac8 activation significantly accelerated the progression and fibrogenesis of endometriotic lesions. In contrast, specific inhibition of Hdac8 or Hdac6, especially of Hdac8, significantly hindered lesional progression and fibrogenesis.

Conclusions

Hdac8 is progressively and aberrantly overexpressed as endometriotic lesions progress. This, along with the documented HDAC1 upregulation in endometriosis and the overwhelming evidence for the therapeutic potentials of HDACIs, calls for further and in-depth investigation of epigenetic aberrations of endometriosis in general and of HDACs in particular.