Michele Gomes Da Broi

Oxidative stress and oocyte quality: ethiopathogenic mechanisms of minimal/mild endometriosis-related infertility

Endometriosis, a highly prevalent gynecological disease, is often associated with infertility, even in its milder forms (minimal and mild endometriosis). However, no consensus has been established with regard to this relationship and the possible mechanisms involved have not been completely elucidated. The oocyte is believed to have an important role in the infertility presented by these patients. Hence, oxidative stress events associated with alterations in the peritoneal, serum and/or follicular microenvironments might result in poor oocyte quality and compromise the reproductive potential of these women. Here, we review possible mechanisms involved in oocyte quality impairment that might lead to infertility in patients with early endometriosis.

N-Acetyl-Cysteine and l-Carnitine Prevent Meiotic Oocyte Damage Induced by Follicular Fluid From Infertile Women With Mild Endometriosis

This study evaluated the potential protective effect of the antioxidants, l-carnitine (LC) and N-acetyl-cysteine (NAC), in preventing meiotic oocyte damage induced by follicular fluid (FF) from infertile women with mild endometriosis (ME). We performed an experimental study. The FF samples were obtained from 22 infertile women undergoing stimulated cycles for intracytoplasmic sperm injection (11 with ME and 11 without endometriosis). Immature bovine oocytes were submitted to in vitro maturation (IVM) divided into 9 groups: no-FF (No-FF); with FF from control (CFF) or ME (EFF) groups; and with LC (C + LC and E + LC), NAC (C + NAC and E + NAC), or both antioxidants (C + 2Ao and E + 2Ao). After IVM, oocytes were immunostained for visualization of microtubules and chromatin by confocal microscopy. The percentage of meiotically normal metaphase II (MII) oocytes was significantly lower in the EFF group (51.35%) compared to No-FF (86.36%) and CFF (83.52%) groups. The E + NAC (62.22%), E + LC (80.61%), and E + 2Ao (61.40%) groups showed higher percentage of normal MII than EFF group. The E + LC group showed higher percentage of normal MII than E + NAC and E + 2Ao groups and a similar percentage to No-FF and CFF groups. Therefore, FF from infertile women with ME causes meiotic abnormalities in bovine oocytes, and, for the first time, we demonstrated that the use of NAC and LC prevents these damages. Our findings elucidate part of the pathogenic mechanisms involved in infertility associated with ME and open perspectives for further studies investigating whether the use of LC could improve the natural fertility and/or the results of in vitro fertilization of women with ME.

Increased concentration of 8-hydroxy-2′-deoxyguanosine in follicular fluid of infertile women with endometriosis

Impaired oocyte quality and oxidative stress might be involved in the pathogenesis of endometriosis-related infertility. To improve our understanding of the role of oxidative stress in this condition, we compare eight oxidative stress markers from each stage, including the simultaneous analysis of lipids, proteins and DNA damage, in the serum and follicular fluid of infertile women with endometriosis and infertile controls undergoing controlled ovarian stimulation for intracytoplasmic sperm injection. In total, 87 serum samples (43 with endometriosis, 44 controls) and 61 follicular fluid samples (29 with endometriosis, 32 controls) free of blood contamination upon visual inspection and presenting granulosa cells alone or granulosa cells plus a retrieved mature oocyte were collected on the day of oocyte retrieval. Total hydroperoxides, malondialdehyde, advanced oxidation protein products, glutathione, superoxide dismutase (SOD) and total antioxidant capacity (TAC) were determined by spectrophotometry, vitamin E by high-performance liquid chromatography and 8-hydroxy-2′–deoxyguanosine (8OHdG) by enzyme-linked immunosorbent assay. The endometriosis group showed higher serum concentrations of glutathione and SOD, lower serum concentrations of TAC and higher follicular concentrations of 8OHdG and vitamin E compared with infertile controls. These data indicate both systemic and follicular oxidative stress in infertile patients with endometriosis. For the first time, we demonstrate the presence of oxidative DNA damage, represented by higher 8OHdG concentrations in the follicular microenvironment of these patients, possibly related to compromised oocyte quality and associated with the pathogenesis of endometriosis-related infertility.

Comparative Analysis of the Spindle of Fresh In Vivo-Matured Human Oocytes Through Polarized Light and Confocal Microscopy A Pilot Study

Background: Considering the scarcity of literature data about the predictive capacity of polarization microscopy (PM) in identifying meiotic normality in human in vivo-matured oocytes, the main objective of the present study was to determine whether qualitative analysis of the spindle through PM can predict meiotic normality in fresh in vivo-matured human oocytes. Methods: Infertile patients undergoing controlled ovarian stimulation to intracytoplasmic sperm injection (ICSI) were selected. Fresh in vivo-matured oocytes were evaluated by PM and, immediately afterward, fixed for confocal microscopy (CM) analysis for evaluation of the spindle and chromosome distribution. We evaluated the percentage of oocytes with meiotic normality and abnormality determined by CM among oocytes with visible and nonvisible spindle and between oocytes with the spindle located at 0° to 60° angle to the first polar body (PB; normal position) and at 60° to 90° angle to the first PB (risky position) according to PM. Results: From 23 patients, 73 oocytes were analyzed. There were no significant differences in the percentage of oocytes with meiotic abnormalities among oocytes with visible and nonvisible spindles and among oocytes with the spindle in the normal and risky positions. Conclusions: Under the conditions tested, qualitative evaluation of the spindle through PM is not consistent with CM analysis and has limited predictive value of meiotic normality in fresh in vivo-matured human oocytes, which needs to be confirmed in larger studies. Our findings make questionable the usefulness of this methodology as a tool for noninvasive oocyte selection for ICSI.

Peritoneal Fluid From Infertile Women With Minimal/Mild Endometriosis Compromises the Meiotic Spindle of Metaphase II Bovine Oocytes: A Pilot Study

Some studies have demonstrated alterations in the composition of peritoneal fluid (PF) from women with endometriosis. Controversial studies have suggested that impaired oocyte quality may be involved in the pathogenesis of endometriosis-related infertility. The aim of this study was to evaluate the spindle and chromosome distribution of in vitro–matured oocytes in the presence of 2 concentrations of PF from infertile women with minimal/mild endometriosis (EI/II) compared to fertile controls. We performed an experimental study using a bovine model. Samples of PF were obtained from 12 women who underwent videolaparoscopy—6 infertile women with EI/II and 6 fertile women without endometriosis (control group). Immature bovine oocytes underwent in vitro maturation (IVM) in the absence of PF and in the presence of 2 concentrations (1% and 10%) of PF from fertile women and from infertile women with EI/II. After 22 to 24 hours of IVM, oocytes were fixed for subsequent immunofluorescence staining for the visualization of microtubules and chromosomes by confocal microscopy. The percentage of meiotically normal oocytes was significantly lower for oocytes that underwent IVM in the presence of 1% (62.50%) and 10% (56.25%) of PF from infertile women with EI/II than in the absence of PF (88.46%) and in the presence of 1% (78.57%) and 10% (84.61%) of PF from fertile women (P < .01). We demonstrated that PF from infertile women with EI/II promotes meiotic abnormalities in in vitro–matured bovine oocytes. Therefore, our results contribute to the understanding of the etiopathogenic mechanisms of infertility related to EI/II.

Ultrastructural Evaluation of Eutopic Endometrium of Infertile Women With and Without Endometriosis During the Window of Implantation: A Pilot Study

Endometriosis is frequently associated with infertility and it is believed that the impairment of endometrial receptivity may be one of the mechanisms involved in this condition. Pinopodes are endometrial cycle-dependent structures that seem to participate in embryo implantation, and alterations in their presence and/or morphology during the window of implantation could affect the endometrial receptivity and be involved in the disease-related infertility. However, the data on pinopodes in these women are scarce and inconclusive. This pilot study aimed to evaluate the cell pattern, including the presence and developmental stage of pinopodes, in eutopic endometrium of infertile patients with and without endometriosis during the window of implantation, using scanning electron microscopy (SEM). Endometrial biopsies were performed using a Pipelle catheter, and 12 samples classified in the window of implantation (6 infertile women with endometriosis and 6 infertile controls) were analyzed by SEM. The frequencies of cell types (microvilli, ciliated, and pinopodes) and the developmental stage of pinopodes were compared between groups using Mann-Whitney U test. Although the study was limited by its sample size, no large differences were detected between the groups regarding the presence and developmental stage of pinopodes, suggesting the absence of large structural changes in the endometrium of infertile women with endometriosis during the window of implantation.

PTGS2 down-regulation in cumulus cells of infertile women with endometriosis

A deleterious effect of endometriosis on oocyte quality has been proposed. Evidence suggests that cumulus cells could be used as indirect biomarkers of oocyte quality. The PTGS2 gene, which encodes cyclooxygenase 2 (COX-2), is deregulated in endometriotic lesions and plays a crucial role in the acquisition of oocyte competence. To date, research evaluating PTGS2 expression in cumulus cells of infertile patients with endometriosis has not been conducted. The aim this study was to compare the expression levels of PTGS2 in cumulus cells of infertile women, with and without endometriosis, undergoing ovarian stimulation for intracytoplasmic sperm injection (ICSI). Therefore, a case-control study compared PTGS2 gene expression in the cumulus cells of 38 infertile patients with endometriosis and 40 without, using real-time polymerase chain reaction. For the first time, decreased expression of PTGS2 was found in cumulus cells of infertile women with endometriosis compared with controls (7.2 ± 10.5 versus 12.4 ± 15.7), which might be related to reduced levels of COX-2 in the cumulus cells of women with the disease. Consequently, we hypothesize that lower transcript levels of PTGS2 in cumulus cells may be involved in the impairment of oocyte quality, suggesting a possible mechanism involved in disease-related infertility.

Oocyte oxidative DNA damage may be involved in minimal/mild endometriosis-related infertility

Early endometriosis is associated with infertility, and oxidative stress may play a role in the pathogenesis of disease‐related infertility. This prospective case‐control study aimed to compare the presence of oxidative stress markers in the follicular microenvironment and systemic circulation of infertile women with minimal/mild endometriosis (EI/II) versus individuals undergoing controlled ovarian stimulation for intracytoplasmic sperm injection (ICSI). Seventy‐one blood samples (27 from infertile women with EI/II and 44 controls with tubal and/or male infertility factor) and 51 follicular fluid samples (19 EI/II and 32 controls) were obtained on the day of oocyte retrieval. Total hydroperoxides (FOX1), reduced glutathione, vitamin E, Superoxide dismutase, total antioxidant capacity, malondialdehyde, advanced oxidation protein products, and 8‐hydroxy‐2′‐deoxyguanosine (8OHdG) concentrations were measured in both fluids. Women with EI/II showed higher FOX1 (8.48 ± 1.72 vs. 7.69 ± 1.71 μmol/g protein) and lower total antioxidant capacity (0.38 ± 0.18 vs. 0.46 ± 0.15 mEq Trolox/L) concentrations in serum, and higher 8OHdG concentrations (24.21 ± 8.56 vs. 17.22 ± 5.6 ng/ml) in follicular fluid compared with controls. These data implicate both systemic and follicular oxidative stress may in infertile women with EI/II undergoing controlled ovarian stimulation for ICSI. Furthermore, the elevated 8OHdG concentrations in follicular fluid of women with EI/II may be related to compromised oocyte quality.

Análise invasiva e não invasiva do fuso meiótico de oócitos humanos obtidos de ciclos estimulados: dados preliminares

PURPOSE: To evaluate the concordance between polarization microscopy and confocal microscopy techniques in the evaluation of the meiotic spindle of human oocytes matured in vivo. METHODS: Prospective study that evaluated oocytes with the first polar extruded body obtained from infertile women who had undergone ovarian stimulation for intracytoplasmic sperm injection. The oocytes with the first polar extruded body were evaluated by polarization microscopy and were then immediately fixed and stained for microtubule and chromatin evaluation by high-performance confocal microscopy. We determined the correlation of polarization microscopy with confocal microscopy in the detection of meiotic oocyte anomalies, and we also evaluated the percentage of oocytes with a visible and non-visible cell spindle by polarization microscopy and with meiotic normality and abnormalities by confocal microscopy. Confidence intervals, Kappas index and concordance between the methodologies were calculated, considering immunofluorescence microscopy analysis as the golden-standard for evaluating normal spindle and oocyte chromosome distribution. RESULTS: We observed that 72.7% of metaphase II oocytes with a nonvisible meiotic spindle by polarization microscopy showed no meiotic abnormalities by confocal analysis and 55.6% of metaphase II oocytes with a visible meiotic spindle by polarization microscopy were found to be abnormal oocytes by the confocal analysis. Only 44.4% of oocytes with a visible meiotic spindle by polarization microscopy were found to be normal by confocal analysis. Concordance between the methods was 51.1% (Kappa: 0.11; 95%CI -0.0958 - 0.319). CONCLUSIONS: The low correlation between polarization microscopy and confocal microscopy in the assessment of oocyte meiotic spindle suggests that visualization of the meiotic spindle of human oocytes at metaphase II by polarization microscopy is not a good indicator of oocyte meiotic normality.