Systemic oxidative stress as a possible mechanism underlying the pathogenesis of mild endometriosis-related infertility

Beyond the surface: Does stage I-II endometriosis impact fertility? Exploring the challenges of mild disease

Endometriosis is one of the most common gynecologic conditions that women face throughout their lives. Despite advances in technology, diagnosis and treatment of this relapsing and remitting condition is still challenging for many women. This review focuses on literature pertaining to minimal/mild (stage I/II) endometriosis and its impact on fertility. The effectiveness of medical interventions to improve infertility and obstetric outcomes in both natural and assisted reproductive technologies cycles remains debated. The recent ESHRE guidelines suggests that operative laparoscopy could be considered for rASRM stage I/II endometriosis as it improves ongoing pregnancy rates.

How Can Selected Dietary Ingredients Influence the Development and Progression of Endometriosis?

Endometriosis is a chronic, hormone-dependent disease characterized by the presence of endometrial tissue in ectopic locations. Since the treatment options for this disease are still limited, and the cure rate is unsatisfactory, the search for ways to treat symptoms and modify the course of the disease is of key importance in improving the quality of life of patients with endometriosis. So far, the literature has shown that nutrition can influence endometriosis through hormonal modification and altering the inflammatory or oxidative response. Since the importance of nutrition in this disease is still a subject of scientific research, we aimed to summarize the current knowledge on the role of dietary modifications in endometriosis. Our review showed that nutrients with anti-inflammatory and antioxidant properties, including most vitamins and several trace elements, may influence the pathogenesis of endometriosis and can be considered as the nutrients preventing the development of endometriosis. However, despite the many discoveries described in this review, further interdisciplinary research on this topic seems to be extremely important, as in the future, it may result in the development of personalized therapies supporting the treatment of endometriosis.

Ovarian endometrioma increases the embryo aneuploid rate: an analysis of 7092 biopsied blastocysts from fertile monogenetic disease carriers

BACKGROUND

Endometriosis affects many reproductive aged patients with fertility decline and poor outcomes of assisted reproductive treatments, mainly by decreased ovarian reserve and lower fertilization and implantation rates. In recent decade, altered oocyte microenvironments and abnormal spindle organization have been reported to be critical to oocyte chromosomal segregation, organization and aneuploid formation. However, clinical evidences are still limited on whether endometriosis influences oocyte and embryo development. We aimed to figure out the impact of endometrioma on embryo aneuploid formation.

METHOD

This retrospective cohort study included 1,021 patients (7,092 biopsied embryos) from January 2012 to December 2020. Fertile patients without a history of miscarriage who underwent PGT-M treatment with aneuploid screening were included. Patients with ovarian endometrioma were defined as the study group, while patients without endometriosis were defined as the control group. All demographic, controlled ovarian stimulation treatment and aneuploid screening data were recorded and compared.

RESULTS

The incidence of endometrioma in our study population was 6.5%. There were 7,092 embryos biopsied in total, with 308 embryos in the study group and 6,784 embryos in the control groups. The demographic characteristics were comparable between the two groups except the basal FSH level (6.02 IU/L vs. 5.52 IU/L, p = 0.012). The euploid rate of the study group was significantly lower than that of the control group (52.6% vs. 61.8%, p = 0.012), while the oocyte maturation, fertilization, usable embryo and blastocyst formation rates were comparable. Adjusted for basal FSH level, starting stimulating gonadotropin dosage, total gonadotropin dosage and FSH level on hCG day, euploid rate was still negatively related to endometrioma status.

CONCLUSIONS

Endometrioma status disturbs oocyte and embryo development. For infertile patients with endometrioma who require assisted reproductive treatment, pre-treatment is necessary to improve treatment outcomes.

TRIAL REGISTRATION

Not applicable.

Oxidative Stress as a Potential Underlying Cause of Minimal and Mild Endometriosis-Related Infertility

Oxidative stress (OS) plays an important role in a variety of physiological and pathological processes of the female reproductive system. In recent years the relationship between OS and endometriosis has been of particular interest, and a theory has been suggested that OS may be a cause of endometriosis development. While the link between endometriosis and infertility is well established, minimal or mild stages of endometriosis are not considered to cause infertility. Increasing evidence of OS as a leading agent in the development of endometriosis has brought up a theory of minimal/mild endometriosis itself being one of the manifestations of high OS rather than a separate disease which directly causes infertility. Moreover, further development of the disease is thought to contribute to an increased production of reactive oxygen species (ROS) thus leading to the progression of endometriosis itself as well as to other pathological processes in the female reproductive system. Therefore, in case of minimal or mild endometriosis, the less invasive treatment could be offered in order to stop the ongoing cycle of endometriosis-reinforced excess ROS production and to reduce their harmful effects. In this article the existing connection between OS, endometriosis, and infertility is explored.

The Impact of Controlled Ovarian Stimulation on Serum Oxidative Stress Markers in Infertile Women with Endometriosis Undergoing ICSI

Endometriosis-related infertility is associated with oxidative stress (OS). The present study aims to compare serum OS markers of infertile women with endometriosis and controls during the follicular phase of the natural cycle (D1), after pituitary downregulation using a GnRH agonist (D2), after controlled ovarian stimulation (COS) on the day of human chorionic gonadotropin administration (D3), and on the day of oocyte retrieval (D4). One hundred and eight serum samples (58 controls and 35 early and 18 advanced endometriosis cases) were collected at these four timepoints. OS markers were compared among the groups and timepoints using a linear regression model with mixed effects and a post-test using orthogonal contrasts. The significance was set at 5%. We observed altered OS markers in the endometriosis patients during the D1, D2, D3, and D4 timepoints compared to the controls. The evidence of systemic OS in infertile patients with endometriosis during COS suggests the mobilization of potent antioxidants in an attempt to protect the oocyte from oxidative damage, especially on the day of oocyte retrieval.

Effects of iron-related compounds and bilirubin on redox homeostasis in endometriosis and its malignant transformations

OBJECTIVES

The balance between oxidative stress and antioxidant defense has been reported to differ between women with endometriosis and patients with its malignant transformation. The aim of this study is to investigate changes in redox balance in endometriosis and endometriosis-related ovarian cancer (EAOC) by simultaneously measuring iron-related compounds and bilirubin.

METHODS

This study included 235 patients with a histopathologically confirmed diagnosis of endometriosis (n=178) and EAOC (n=57). Cyst fluid samples were collected in Nara Medical University hospital from January 2013 to May 2019. The levels of iron-related compounds (total iron, heme iron, free iron, oxyhemoglobin [oxyHb], methemoglobin [metHb], and metHb/oxyHb ratio) and bilirubin were measured.

RESULTS

Total iron, heme iron, free iron, metHb/oxyHb ratio, and bilirubin were significantly elevated in endometriosis compared to EAOC. In both endometriosis and EAOC, iron-related compounds in the cyst were correlated with each other. There was no statistically significant difference in oxyHb and metHb levels between the two groups, but the metHb/oxyHb ratio was significantly higher in endometriosis than in EAOC. Bilirubin was positively correlated with total iron and free iron in EAOC, but there was no correlation between bilirubin and iron-related compounds in endometriosis.

CONCLUSIONS

Iron-induced oxidative stress in endometriosis may exceed bilirubin-dependent antioxidant capability, while redox homeostasis in EAOC can be maintained by at least bilirubin.

Is There a Balance in Oxidative-Antioxidant Status in Blood Serum of Patients with Advanced Endometriosis?

Can redox homeostasis indicators be potential non-invasive markers, crucial in the diagnosis and treatment of endometriosis? We checked if the differences in levels of serum oxidative-antioxidant balance parameters (TAS, FRAP, albumin, total bilirubin, uric acid, iron, SIRT3, SIRT5, SIRT6, telomerase, AOPP) are significant between patients with advanced endometriosis (E), healthy women (control group, C) and non-endometriosis women, but with other gynecological disorders (NE). The FRAP concentrations were significantly higher in E and NE group than in the control group (p = 0.015 and p = 0.017, respectively). The telomerase concentrations were significantly higher in the endometriosis group than in the control group (p = 0.004). Significantly higher concentrations of AOPP were observed in E (p < 0.001) and NE groups (p = 0.028) in comparison to the control subjects. Between stages III and IV of endometriosis, a significant difference existed only in concentration of iron (p = 0.013). There were no significant differences between the studied groups in the values of the remaining parameters. Based on the results of ROC curve analysis, we can conclude that the levels of serum FRAP, telomerase and AOPP may be taken into account as promising diagnostics markers that reflect the degree of oxidative stress accompanying advanced endometriosis.

Oxidative Stress in Reproduction: A Mitochondrial Perspective

Mitochondria are fundamental organelles in eukaryotic cells that provide ATP through oxidative phosphorylation. During this process, reactive oxygen species (ROS) are produced, and an imbalance in their concentrations can induce oxidative stress (OS), causing cellular damage. However, mitochondria and ROS play also an important role in cellular homeostasis through a variety of other signaling pathways not related to metabolic rates, highlighting the physiological relevance of mitochondria–ROS interactions. In reproduction, mitochondria follow a peculiar pattern of activation, especially in gametes, where they are relatively inactive during the initial phases of development, and become more active towards the final maturation stages. The reasons for the lower metabolic rates are attributed to the evolutionary advantage of keeping ROS levels low, thus avoiding cellular damage and apoptosis. In this review, we provide an overview on the interplay between mitochondrial metabolism and ROS during gametogenesis and embryogenesis, and how OS can influence these physiological processes. We also present the possible effects of assisted reproduction procedures on the levels of OS, and the latest techniques developed to select gametes and embryos based on their redox state. Finally, we evaluate the treatments developed to manage OS in assisted reproduction to improve the chances of pregnancy.

Association of Urinary Levels of Bisphenols A, F, and S with Endometriosis Risk: Preliminary Results of the EndEA Study

Aim: The aim of this study was to explore associations of urinary concentrations of bisphenols A (BPA), S (BPS), and F (BPF) and of thiobarbituric acid reactive substances (TBARS) with the risk of endometriosis in women of childbearing age. Methods: This case-control study enrolled 124 women between January 2018 and July 2019: 35 women with endometriosis (cases) and 89 women without endometriosis undergoing abdominal surgery for other reasons (controls). Endometriosis was diagnosed (cases) or ruled out (controls) by laparoscopic inspection of the pelvis and the biopsy of suspected lesions (histological diagnosis). Fasting urine samples were collected before surgery to determine concentrations of BPA, BPS, BPF, and TBARS. Associations of bisphenol and TBARS concentrations with endometriosis risk were explored with multivariate logistic and linear regression analyses. Results: After adjustment for urinary creatinine, age, BMI, parity, and residence, endometriosis risk was increased with each 1 log unit of BPA [OR 1.5; 95%CI 1.0-2.3] and Σbisphenols [OR 1.5; 95%CI 0.9-2.3] but was not associated with the presence of BPS and BPF. Classification of the women by tertiles of exposure revealed statistically significant associations between endometriosis risk and the second tertile of exposure to BPA [OR 3.7; 95%CI 1.3-10.3] and Σbisphenols [OR 5.4; 95%CI 1.9-15.6]. In addition, TBARS concentrations showed a close-to-significant relationship with increased endometriosis risk [OR 1.6; 95%CI 1.0-2.8], and classification by TBARS concentration tertile revealed that the association between endometriosis risk and concentrations of BPA [OR 2.0; 95%CI 1.0-4.1] and Σbisphenols [OR 2.2; 95%CI 1.0-4.6] was only statistically significant for women in the highest TBARS tertile (>4.23 μM). Conclusion: Exposure to bisphenols may increase the risk of endometriosis, and oxidative stress may play a crucial role in this association. Further studies are warranted to verify these findings.