Getting to Know Endometriosis-Related Infertility Better: A Review on How Endometriosis Affects Oocyte Quality and Embryo Development

The Effects of Endometriosis on Oocyte and Embryo Quality

Endometriosis is a complex and multifaceted gynecological disorder characterized by the abnormal growth and presence of endometrial-like tissue outside the confines of the uterine cavity. It can lead to a wide range of distressing symptoms, including chronic pelvic pain, heavy and/or irregular menstrual bleeding, and significant challenges with fertility. While the association between endometriosis and infertility is well recognized, the precise mechanisms through which the disease affects oocyte and embryo quality remain controversial. Studies that utilized transcriptomic, metabolomic, and ultrastructural analyses indicated dysregulated energy metabolism, oxidative stress, mitochondrial dysfunction, and inflammatory alterations in the ovarian microenvironment. The impact of endometriosis on fertilization, embryo development, and implantation remains debated, with conflicting findings across different study designs. Some investigations reported impaired oocyte morphology, reduced fertilization rates, and poorer embryo quality, while others suggested that endometriosis does not significantly affect ART outcomes when confounding factors are controlled. Recent studies highlight the importance of distinguishing the disease severity, lesion location, and prior surgical interventions when assessing reproductive outcomes. The need for standardized methodologies in evaluating oocyte and embryo quality, alongside personalized treatment approaches, is emphasized. Further research is warranted to elucidate the precise molecular mechanisms underlying these effects and to develop targeted therapeutic strategies aimed at improving ART success in women with endometriosis. This narrative review provides a thorough examination of the previous research on the impact of endometriosis on oocyte and embryo quality, highlighting both the known mechanisms and the areas that require further investigation. This will help to guide future research and clinical management strategies to improve reproductive outcomes for women with endometriosis.

The effect of endometriosis on oocyte quality: mechanisms, diagnosis and treatment

Endometriosis significantly impacts the physical and mental health of women of reproductive age. While some patients can achieve pregnancy through surgery or in vitro fertilization (IVF), many still struggle with IVF failure due to poor oocyte quality. This presents a major clinical challenge that requires immediate attention. The causes of oocyte quality decline in endometriosis patients are diverse and have not yet been definitively identified. Furthermore, effective diagnostic mechanisms and therapeutic strategies remain elusive. To provide possible clinical solutions to improve pregnancy rates in patients with endometriosis, this review evaluates the current literature on the impact of endometriosis on oocyte quality, the possible mechanisms and management strategies of endometriosis leading to poor oocyte quality.

Single-cell dual-omics reveals translational and transcriptional landscapes and regulations in oocytes from ovarian endometriosis patients

Introduction

A significant proportion of women in their reproductive years are afflicted by endometriosis. And one of the major contributing factors to infertility linked to ovarian endometriosis is thought to be oocyte quality. The precise molecular mechanisms are still unknown. Furthermore, because of transcriptional silence, translatome is better able to explain molecular behavior in oocytes than transcriptome sequencing, which has been used widely in recent years.

Methods

We conducted single-cell transcriptome and translatome sequencing on oocytes obtained from patients with ovarian endometriosis, as well as from control subjects with infertility due to tubal or male factors.

Results

For the first time, we characterized the translational and transcriptional profiles of mRNA in GV-stage oocytes from patients with ovarian endometriosis and control subjects. Our translational analysis identified 2,480 differentially expressed genes in oocytes from ovarian endometriosis patients. Furthermore, we demonstrated that global translational activity in human oocytes is significantly altered by ovarian endometriosis. Key pathways such as "oxidative stress," "oocyte meiosis," and "spliceosome" were identified as critical factors influencing oocyte quality in ovarian endometriosis patients.

Discussion

This study elucidated the molecular characteristics and potential mechanisms underlying poor oocyte quality in patients with ovarian endometriosis. Our findings provided new insights into the pathogenesis of endometriosis-associated infertility and highlighted potential therapeutic targets for improving oocyte quality and reproductive outcomes.

Effects of various controlled ovarian hyperstimulation protocols and surgery on pregnancy outcomes in women with endometriosis

Endometriosis is a common gynecological condition in women of childbearing age that causes symptoms such as menstrual changes and dysmenorrhea, and is also a major cause of infertility. Therefore, women with endometriosis usually need to use assisted reproductive technology (ART), such as in vitro fertilization or intracytoplasmic sperm injection, to increase their chances of conceiving. Numerous clinical observations and studies have indicated that endometriosis can affect the success of ART, such that women with endometriosis who use ART have a lower live-birth rate than those without endometriosis who use ART. Therefore, this article reviews the impact of various controlled ovarian hyperstimulation protocols and surgery on the pregnancy outcomes of women with endometriosis using ART to explore the selection of individualized treatment.

Endometriosis: A Comprehensive Exploration of Inflammatory Mechanisms and Fertility Implications

Endometriosis is a prevalent gynecological disorder characterized by the ectopic growth of endometrial-like tissue outside the uterus. This condition poses significant challenges due to its chronic nature, debilitating symptoms such as pelvic pain and infertility, and substantial impact on quality of life. Central to the pathogenesis of endometriosis are inflammatory mechanisms that perpetuate tissue proliferation, adhesion formation, and immune dysregulation within the pelvic cavity. Inflammation plays a pivotal role in the development and progression of endometriosis, influencing the severity of symptoms and complications associated with the disease. Dysregulated immune responses contribute to the persistence of ectopic endometrial implants, exacerbating pelvic pain and other symptoms experienced by affected individuals. Moreover, the inflammatory milieu created by endometriotic lesions disrupts normal ovarian function, impairs follicular development, and compromises reproductive outcomes, thereby posing challenges to fertility. This review comprehensively explores the inflammatory mechanisms underlying endometriosis and their implications for fertility. Synthesizing current research and clinical insights elucidates the intricate interplay between inflammation, disease progression, and reproductive health outcomes. Understanding these complex interactions is essential for developing targeted diagnostic strategies and optimizing therapeutic approaches tailored to alleviate symptoms and improve fertility outcomes in individuals with endometriosis. Ultimately, this review aims to enhance the understanding of endometriosis pathophysiology, inform clinical practice, and stimulate further research to advance personalized care and management strategies for this challenging condition.

The Role of One-Carbon Metabolism and Methyl Donors in Medically Assisted Reproduction: A Narrative Review of the Literature

One-carbon (1-C) metabolic deficiency impairs homeostasis, driving disease development, including infertility. It is of importance to summarize the current evidence regarding the clinical utility of 1-C metabolism-related biomolecules and methyl donors, namely, folate, betaine, choline, vitamin B12, homocysteine (Hcy), and zinc, as potential biomarkers, dietary supplements, and culture media supplements in the context of medically assisted reproduction (MAR). A narrative review of the literature was conducted in the PubMed/Medline database. Diet, ageing, and the endocrine milieu of individuals affect both 1-C metabolism and fertility status. In vitro fertilization (IVF) techniques, and culture conditions in particular, have a direct impact on 1-C metabolic activity in gametes and embryos. Critical analysis indicated that zinc supplementation in cryopreservation media may be a promising approach to reducing oxidative damage, while female serum homocysteine levels may be employed as a possible biomarker for predicting IVF outcomes. Nonetheless, the level of evidence is low, and future studies are needed to verify these data. One-carbon metabolism-related processes, including redox defense and epigenetic regulation, may be compromised in IVF-derived embryos. The study of 1-C metabolism may lead the way towards improving MAR efficiency and safety and ensuring the lifelong health of MAR infants.

A Novel Classification of Endometriosis Based on Clusters of Comorbidities

Endometriosis is a heterogeneous, complex, and still challenging disease, due to its epidemiological, etiological and pathogenic, diagnostic, therapeutic, and prognosis characteristics. The classification of endometriosis is contentious, and existing therapies show significant variability in their effectiveness. This study aims to capture and describe clusters of women with endometriosis based on their comorbidity. With data extracted from electronic records of primary care, this study performs a hierarchical clustering with the Ward method of women with endometriosis with a subsequent analysis of the distribution of comorbidities. Data were available for 4055 women with endometriosis, and six clusters of women were identified: cluster 1 (less comorbidity), cluster 2 (anxiety and musculoskeletal disorders), cluster 3 (type 1 allergy or immediate hypersensitivity); cluster 4 (multiple morbidities); cluster 5 (anemia and infertility); and cluster 6 (headache and migraine). Clustering aggregates similar units into similar clusters, partitioning dissimilar objects into other clusters at a progressively finer granularity-in this case, groups of women with similarities in their comorbidities. Clusters may provide a deeper insight into the multidimensionality of endometriosis and may represent diverse "endometriosis trajectories" which may be associated with specific molecular and biochemical mechanisms. Comorbidity-based clusters may be important to the scientific study of endometriosis, contributing to the clarification of its clinical complexity and variability. An awareness of those comorbidities may help elucidate the etiopathogenesis and facilitate the accurate earlier diagnosis and initiation of treatments targeted toward particular subgroups.

Impact of moderate-to-severe endometriosis on IVF cumulative live birth rate: a retrospective matched cohort study

RESEARCH QUESTION

Does moderate-to-severe endometriosis have an impact on cumulative live birth rates (cLBR) and IVF outcomes?

DESIGN

In this retrospective matched cohort study, women with moderate-to-severe endometriosis undergoing IVF or intracytoplasmic sperm injection treatment from January 2015 to December 2020 were matched 1:2 to women with other causes of infertility (control group). The main outcome was cLBR per cycle and per woman, and secondary outcomes were number of oocytes retrieved and number of mature oocytes, fertilization rate, total number of embryos and usable embryos, implantation rate, clinical pregnancy rate and miscarriage rate per cycle.

RESULTS

In total, 195 women with endometriosis were matched with 390 women without endometriosis (323 and 646 cycles, respectively). Women with endometriosis had significantly fewer oocytes retrieved than women in the control group (P=0.003) despite higher doses of gonadotropins, but had a similar number of mature oocytes, fertilization rate, and total number of embryos and usable embryos. cLBR per cycle and per women did not differ significantly between the endometriosis group and the control group (19.8% versus 24.3%, P = 0.12; 32.3% versus 37.2%, P = 0.24, respectively). In women with endometrioma, a history of cystectomy did not impact cLBR per cycle (28.3% versus 31.9%, P = 0.68). We did not observe any significant impact of tobacco use in the endometriosis group compared with the control group (16.4% versus 25.9%, P = 0.13).

CONCLUSION

This matched cohort study did not observe a significant impact of moderate-to-severe endometriosis on cLBR among women undergoing IVF. These data are reassuring for the counselling of infertile women with endometriosis before IVF.

Concomitant Autoimmunity in Endometriosis Impairs Endometrium-Embryo Crosstalk at the Implantation Site: A Multicenter Case-Control Study

Endometriosis and autoimmune diseases share a hyper-inflammatory state that might negatively impact the embryo-endometrium crosstalk. Inflammatory and immune deregulatory mechanisms have been shown to impair both endometrial receptivity and embryo competence at the implantation site. The aim of this study was to investigate the potential additional impact of co-existing autoimmunity in women affected by endometriosis on the early stages of reproduction. This was a retrospective, multicenter case-control study enrolling N = 600 women with endometriosis who underwent in vitro fertilization-embryo transfer cycles between 2007 and 2021. Cases were women with endometriosis and concomitant autoimmunity matched based on age and body mass index to controls with endometriosis only in a 1:3 ratio. The primary outcome was the cumulative clinical pregnancy rate (cCPR). The study found significantly lower cleavage (p = 0.042) and implantation (p = 0.029) rates among cases. Autoimmunity (p = 0.018), age (p = 0.007), and expected poor response (p = 0.014) were significant negative predictors of cCPR, with an adjusted odds ratio of 0.54 (95% CI, 0.33-0.90) for autoimmunity. These results suggest that the presence of concomitant autoimmunity in endometriosis has a significant additive negative impact on embryo implantation. This effect might be due to several immunological and inflammatory mechanisms that interfere with both endometrial receptivity and embryo development and deserves further consideration.

The Impact of Endometrioma on Embryo Quality in In Vitro Fertilization: A Retrospective Cohort Study

The influence of endometrioma on oocyte and embryo competence is inconclusive. Furthermore, the benefits of surgical treatment remain uncertain. This study aimed to investigate the effect of endometrioma on oocyte and embryo quality from a morphological perspective and further explore whether surgery could contribute to improving oocyte and embryo competence. A total of 664 IVF cycles with endometrioma (538 cycles underwent surgeries) and 3133 IVF cycles from the control group were included. The propensity score matching was used to balance the baseline differences between groups. There was a lower MII oocyte rate (85.0% versus 87.8%, p < 0.001; 84.9% versus 87.6%, p = 0.001) and a similar good-quality embryos rate in women with endometrioma (and those who underwent surgeries) compared with control group. For women with endometrioma, the rates of blastocyst development (67.1% versus 60.2%; p = 0.013) and good blastocyst development (40.7% versus 35.2%; p = 0.049) were significantly higher in those who had undergone surgical treatment compared with those who had not, but the rates of MII oocytes (79.9% versus 87.7%; p < 0.001) and normal fertilization (55.2% versus 66.2%; p < 0.001) were lower. The study indicates that endometrioma, including its surgical treatment, compromises the oocyte maturity not the embryo quality at the cleavage stage; however, the surgery seems to contribute to improving blastocyst development.

Implantation Failure in Endometriosis Patients: Etiopathogenesis

Embryo implantation requires adequate dialogue between a good quality embryo and a receptive endometrium. This implantation is still considered as the black box of reproductive medicine. Endometriosis is a highly prevalent chronic inflammatory disease, concerning about 10% of women of reproductive age and is one of the major causes of female infertility. The mechanisms involved in endometriosis-related infertility, an event not yet completely understood, are multifactorial and include anatomical changes, reduction in ovarian reserve, endocrine abnormalities, genetic profile, immunity markers, inflammatory mediators, or altered endometrial receptivity. In this article, we will focus on the impact of endometriosis on embryo quality and on endometrial receptivity. Results: Poor oocyte and embryo quality seem to promote a lower pregnancy rate, more than the endometrium itself in women with endometriosis. Other studies report the contrary. In addition, hormonal imbalance observed in the endometrium could also alter the embryo implantation. Conclusions: Controversial results in the literature add difficulties to the understanding of the mechanisms that lead to embryo implantation disorders. Furthermore, either oocyte/embryo impairment, altered endometrium, or both may cause impaired implantation. New prospective, randomized, and controlled studies are necessary to determine the origin of the defects that make conception more difficult in the case of endometriosis and adenomyosis.

Infertile women with endometriosis possess differences in cytokine levels in various tissues

OBJECTIVE

(1) To characterize the cytokine expression profiles of endometriosis related infertile women in comparison to fertile women with endometriosis; (2) to investigate the correlation of the cytokine levels from different tissues.

METHODS

100 stage IV endometriosis patients were recruited and grouped by infertility status (n = 50, separately). Concentrations of TNF-α, TGF-β1, IL-10, and IL-17A from the serum, peritoneal fluid (PF), eutopic, and ectopic endometrium samples were measured.

RESULTS

(1) In the infertile group, the concentrations of IL-10 within serum, PF and eutopic endometrium were all significantly higher (p = .022 and <.01, .013, respectively), the levels of TGF-β1 in serum and eutopic endometrium samples were both higher (p = .025 and p < .01), the levels of IL-17A in the PF, eutopic, and ectopic endometrium were all lower (p < .01, all). (2) Significant positive correlation was observed between IL-17A from PF and the ectopic endometrium (p = .014), IL-17A from PF and eutopic endometrium (p < .01). The PF IL-10 levels positively correlated with those in the serum (p = .007).

CONCLUSIONS

This is the first study comparing the levels of cytokines within four different tissues of endometriosis women with or without infertility. The study revealed that endometriosis-related infertile women possess significant differences in cytokine levels in comparison to fertile women with endometriosis. The levels of inflammatory factors from different tissues had certain positive correlations. Infertility may indicate the progress of the disease.

Research Progress on the Mechanism Between Polycystic Ovary Syndrome and Abnormal Endometrium

As a highly dynamic tissue, the endometrium is periodically shed in response to the secretion of estrogen and progesterone. After menarche, the endometrium of healthy women proliferates and differentiates under the action of steroid hormones (e.g., 17β-estradiol and progesterone) that are secreted by the ovaries to provide appropriate conditions for embryo implantation. Polycystic ovary syndrome (PCOS), a prevalent endocrine and metabolic disorder in reproductive-aged women, is usually associated with multiple cysts within the ovaries and excess levels of androgen and is characterized by hirsutism, acne, menstrual irregularity, infertility, and increased risk of insulin resistance. Multiple factors, such as anovulation, endocrine-metabolic abnormalities, and inflammation, can disrupt the endometrium in PCOS patients and can lead to endometrial hyperplasia, pregnancy complications, or even cancer. Despite many recent studies, the relationship between PCOS and abnormal endometrial function is still not fully understood. In this review, we investigate the correlation of PCOS patient endometrium with anovulation, hyperandrogenemia, insulin resistance, progesterone resistance, and inflammatory cytokines, aiming to provide a theoretical basis for the treatment of disorders caused by endometrial dysfunction in PCOS patients.

Molecular Drivers of Developmental Arrest in the Human Preimplantation Embryo: A Systematic Review and Critical Analysis Leading to Mapping Future Research

Developmental arrest of the preimplantation embryo is a multifactorial condition, characterized by lack of cellular division for at least 24 hours, hindering the in vitro fertilization cycle outcome. This systematic review aims to present the molecular drivers of developmental arrest, focusing on embryonic and parental factors. A systematic search in PubMed/Medline, Embase and Cochrane-Central-Database was performed in January 2021. A total of 76 studies were included. The identified embryonic factors associated with arrest included gene variations, mitochondrial DNA copy number, methylation patterns, chromosomal abnormalities, metabolic profile and morphological features. Parental factors included, gene variation, protein expression levels and infertility etiology. A valuable conclusion emerging through critical analysis indicated that genetic origins of developmental arrest analyzed from the perspective of parental infertility etiology and the embryo itself, share common ground. This is a unique and long-overdue contribution to literature that for the first time presents an all-inclusive methodological report on the molecular drivers leading to preimplantation embryos’ arrested development. The variety and heterogeneity of developmental arrest drivers, along with their inevitable intertwining relationships does not allow for prioritization on the factors playing a more definitive role in arrested development. This systematic review provides the basis for further research in the field.

Pathogenesis of Endometriosis: The Origin of Pain and Subfertility

Endometriosis (EM) and adenomyosis (AM) are common conditions with pain and infertility as the principal symptoms. The pathophysiology of pain in EM and AM comprises sensory and somatoform pain mechanisms. Over time, these may aggravate and lead to individual complex disease patterns if not diagnosed and treated. Despite the known facts, several years often pass between the onset of symptoms and diagnosis. Chronic pain disorders with changes on a neuronal level frequently arise and are linked to depressive disorders, with the process becoming a vicious cycle. Additionally, women with EM and AM suffer from sub- and infertility. Low fecundity rates are caused by anatomical changes in combination with behavioral changes in the sexual activity of women with chronic pain as well as local proinflammatory factors that not only decrease implantation rates but also promote early abortions.