JBRA Assist. Reprod. 2019;23(3):273-280
REVIEW

doi: 10.5935/1518-0557.20190029

Ethiopathogenic mechanisms of endometriosis-related infertility

Michele Gomes Da Broi1, Rui Alberto Ferriani1,2, Paula Andrea Navarro1,2

1Human Reproduction Division, Department of Obstetrics and Gynecology, Ribeirão Preto School of Medicine, University of São Paulo, Ribeirão Preto, SP, Brazil
2National Institute of Hormones and Woman’s Health, CNPq, Brazil

Received October 10, 2018
Accepted March 28, 2019

Corresponding author:
Michele Gomes Da Broi
Department of Obstetrics & Gynecology
School of Medicine of Ribeirão Preto
University of São Paulo
Ribeirão Preto, SP, Brazil.
E-mail: michi.dabroi@gmail.com

CONFLICT OF INTEREST
The authors declare that they have no competing interests.

ABSTRACT
Endometriosis is a highly prevalent disease among women of reproductive age and is frequently associated to infertility. However, the mechanisms underlying endometriosis-related infertility are still not completely known. Several studies have been conducted in order to elucidate this question. Besides anatomical changes that may impair gametes and embryo transport along the tubes; a smaller ovarian reserve due to advanced endometriosis and endometriomas; and a dysregulated hypothalamic-pituitary-ovarian axis, there are pieces of evidence suggesting that the peritoneal ectopic endometrial foci may induce a local inflammatory response, with the recruitment of macrophages, cytokine release, and reactive oxygen species generation, leading to a pro-oxidant peritoneal microenvironment. These alterations may be systemically reflected and also affect the follicular microenvironment. A harmful follicular fluid may disrupt cumulus cells functions and, consequently, compromise oocyte competence. There is also evidence suggesting that the peritoneal fluid of women with endometriosis may alter sperm function. Reduced endometrial receptivity is also pointed as a possible mechanism involved in endometriosis-related infertility, which needs further investigation.

Keywords: endometriosis, infertility, etiopathogenesis

INTRODUCTION
Endometriosis is a disease defined as the presence of endometrial tissue outside the uterine cavity (Burney & Giudice, 2012; Gupta et al., 2006). It is highly prevalent among women of reproductive age (Burney & Giudice, 2012), which is very alarming, since endometriosis is also frequently associated to infertility (ASRM, 2012). It affects approximately 25 to 50% of infertile women, and 30 to 50% of endometriosis patients have difficulties to become pregnant (ASRM, 2012). Although the literature widely addresses the association between the disease and infertility (Akande et al., 2004; Carvalho et al., 2012; Da Broi & Navarro, 2016b; Gupta et al., 2008; Marcoux et al., 1997; Parazzini, 1999), the etiopathogenic mechanisms involved in this relation have not yet been fully understood.
Here, we review and discuss on the role of some possible mechanisms underlying this condition, including anatomical changes of the reproductive tract and smaller ovarian reserve possibly involved in advanced disease infertility, and also the role of peritoneal and follicular microenvironments, cumulus cells (CC), sperm function, and endometrial receptivity as possible mechanisms involved in the fertility impairment in patients with early endometriosis.

Endometriosis-related infertility
Although endometriosis is frequently associated to infertility (ASRM, 2012), the mechanisms underlying this condition are still not completely known. Several studies have been conducted in order to elucidate this question, and authors have suggested different mechanisms potentially involved in infertility impairment, including anatomical and microenvironmental conditions that may negatively impact the oocyte competence acquisition, egg fertilization, zygote transport within the tube and embryo implantation. In cases of advanced disease (rAFS III and IV), anatomical changes of the reproductive tract such as peritubal and periovarian adhesions and pelvic distortions are indicated as limiting factors, which could impair the oocyte capture by the fimbriae, its passage through the tuba, as well as the gametic interaction and the embryonic path to the uterine cavity (ASRM, 2012; Catenacci & Falcone, 2008; Schenken et al., 1984). It has also been suggested a smaller ovarian reserve in women with advanced endometriosis (Seyhan et al., 2015), especially in cases of endometrioma (Hock et al., 2001; Sanchez et al., 2014; Uncu et al., 2013). In this sense, some authors defend that ovarian endometrioma per se may affect ovarian reserve (Goodman et al., 2016; Uncu et al., 2013). It is believed that ovarian tissue may be target of toxic substances contained in the endometrioma, which could diffuse in the adjacent tissue and culminate with the reduced ovarian reserve (Sanchez et al., 2014). On the other hand, some researchers believe that surgical treatment of endometriomas promotes the damage on ovarian tissue, predisposing to low follicle count (Cranney et al., 2017; Goodman et al., 2016; Mehdizadeh Kashi et al., 2017). However, infertility presented by women with early endometriosis (rAFS I and II), where pelvic anatomical distortions are not present, raises questions about the involvement of other mechanisms in the impairment of fertility in patients with the disease (Da Broi & Navarro, 2016b; Holoch & Lessey, 2010). In this sense, it is believed that the peritoneal, follicular and endometrial microenvironments are altered in these women, with consequent damages to folliculogenesis, ovulation, oocyte quality, endometrial receptivity and, even, sperm function (Agarwal et al., 2012; Gupta et al., 2008).

Peritoneal microenvironment and immune function
Evidence from literature suggest that the immune function is possibly dysregulated in endometriosis patients (Gupta et al., 2008; Miller et al., 2017). It is questioned if women with endometriosis have immunological dysfunction preventing the removal of endometrial implants and leading to tissue adhesion in the peritoneal cavity (Ahn et al., 2015a). It is also believed that peritoneal endometrial lesions are responsible for the activation of macrophages, with consequent increase in the generation of inflammatory factors, reactive oxygen and nitrogen species, cytokines, growth factors, and prostaglandins. A marked inflammatory response, with exacerbation of reactive species and cytokines, would make the pelvic environment adverse, which would be reflected in the peritoneal fluid (PF) of these women (Agarwal et al., 2003; Gupta et al., 2006; Ruder et al., 2008; Szczepańska et al., 2003). Corroborating this reasoning, studies have shown changes in the PF composition of women with endometriosis, including changes in cellular and humoral mediators (Cheong et al., 2002; Eisermann et al., 1988; Jørgensen et al., 2017; Keenan et al., 1995), including pro-inflammatory cytokines such as tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, IL-8, IL-10, IL-13, IL-17, IL-33, monocyte chemoattractant protein (MCP)-1, macrophage migration inhibitory factor (MIF) and Regulated on Activation, Normal T Cell Expressed and Secreted (RANTES) (Ahn et al., 2015b; Bersinger et al., 2006; Harada et al., 1997; Punnonen et al., 1996; Sikora et al., 2012; Wang et al., 2018; Yoshino et al., 2003), chemokines (Margari et al., 2013), angiogenic factors (Ahn et al., 2015b; Kianpour et al., 2013; Yoshino et al., 2003), and increased activated macrophages, T-lymphocytes and natural killer cells (Lebovic et al., 2001). These alterations may lead to chronic inflammation, proliferation of lesions, local hormonal imbalance, what may lead to poor oocyte quality, poor sperm motility, embryo toxicity and reduced endometrial receptivity (Miller et al., 2017). In addition, there is evidence of altered oxidative stress (OS) markers in the PF of these women (Polak et al., 2013; Santulli et al., 2015; Shanti et al., 1999). As a consequence of these alterations, studies have suggested an adverse effect of PF on the reproductive capacity of the patients (Jianini et al., 2017; Gupta et al., 2008; Mansour et al., 2009a; Mansour et al., 2010). Because the PF bathes the ovaries and maintains direct contact with the oocyte during ovulation and in its initial course through the uterine tube, changes in this microenvironment may culminate in oocyte damage and be involved in the impairment of oocyte quality in endometriosis patients. Accordingly, studies with murine model indicate damage to spindle and chromosomes after incubation of oocytes in metaphase II with PF from women with the disease (Mansour et al., 2009a; Mansour et al., 2010) which were reduced with the addition of an antioxidant, suggesting the role of OS in promoting the oocyte alterations (Mansour et al., 2009a). In addition, in a recent study, meiotic damage to bovine oocytes was evidenced after in vitro oocyte maturation in the presence of PF from infertile patients with endometriosis, suggesting changes in this fluid could also compromise oocyte development during maturation and possibly affect oocyte quality of these patients (Jianini et al., 2017).

Follicular microenvironment
Evidences have suggested the occurrence of systemic OS in women with the disease (Andrade et al., 2010; Da Broi et al., 2016; Liu et al., 2013; Nasiri et al., 2017; Singh et al., 2013), which could consequently reach the ovaries and affect intrafollicular oocyte development, since the ovarian cortex is highly vascularized, especially in the final period of folliculogenesis (Tamanini & De Ambrogi, 2004). Different studies have investigated changes in the follicular fluid (FF) composition of women with endometriosis, such as cytokines (Singh et al., 2016; Wu et al., 2017) OS markers (Choi et al., 2015; Da Broi et al., 2016a; Huang et al., 2014; Liu et al., 2013; Nasiri et al., 2017; Prieto et al., 2012; Singh et al., 2013), growth factors (Choi et al., 2015), metals (Singh et al., 2013), prostaglandins (Du et al., 2013), macrophages activation pattern (Lamaita et al., 2012), lipidic (Cordeiro et al., 2015) and proteic profiles (Lo Turco et al., 2013). In this sense, the evidences of OS in the follicular microenvironment of these women (Choi et al., 2015; Da Broi et al., 2016a; Huang et al., 2014; Liu et al., 2013; Nasiri et al., 2017; Prieto et al., 2012; Singh et al., 2013), suggest that not only their PF, but also their FF may contain substances harmful to the acquisition of oocyte competence. In this regards, studies evaluating the effect of FF of infertile women with endometriosis on in vitro maturation of bovine oocytes showed spindle and chromosomal damage (Da Broi et al., 2014), which were prevented by the addition of antioxidants to the maturation medium, suggesting a pro-oxidant microenvironment in the ovarian follicles of these women (Giorgi et al., 2016). Possibly, these alterations are consequence of OS damage on oocyte cell structures. Recently, it was evidenced the presence of higher levels of eight-hydroxy-2-deoxyguanosine (8OHdG) in the FF of infertile women with endometriosis, suggesting oxidative DNA damage in cumulus-oocyte complexes, being a possible mechanism involved in the impairment of oocyte quality in these patients (Da Broi et al., 2016a).

Cumulus cells
The CC are considered indirect markers of oocyte quality (Assou et al., 2006; Hamamah et al., 2006; Hamel et al., 2008; Haouzi & Hamamah, 2009), since they are responsible for energetic metabolism (Downs & Utecht, 1999; Monniaux, 2016; Paczkowski et al., 2013; Saito et al., 1994), ions support (FitzHarris et al., 2007), transcriptional maintenance (Albertini et al., 2001), maturation (Li & Albertini, 2013; Tanghe et al., 2002) and defense (Albertini et al., 2001; Lolicato et al., 2015; Shaeib et al., 2016; Tanghe et al., 2002) of the female gamete, so that changes in these cells can harm follicular development and indicate damage to the oocyte. Studies comparing the expression of genes related to steroidogenesis, acquisition of oocyte competence, and OS in CC of infertile women with and without endometriosis have been performed. Accordingly, the aromatase-encoding gene (CYP19A1) (Barcelos et al., 2015; Hosseini et al., 2016), and the cyclooxygenase 2 (COX-2)-encoding gene (PTGS2) (Donabela et al., 2011) that may mediate CYP19A1 induction, seem to be both lower in CC of infertile women with endometriosis compared to infertile controls undergoing controlled ovarian stimulation for intracytoplasmic sperm injection (ICSI). In this regards, it has been suggested an epigenetic alteration may be involved in CYP19A1 gene deregulation in CC of these patients (Hosseini et al., 2016). Altogether, these data suggest reduced aromatase and, consequently, possibly altered follicular steroidogenesis and impaired oocyte quality in infertile women with endometriosis, what requires confirmation by further studies. The evaluation of enzymatic antioxidants gene expression in CC of infertile women with and without endometriosis evidenced increased superoxide dismutase 1 (SOD1) expression in the moderate/severe endometriosis group compared to women with minimal/mild endometriosis and controls. It suggests that advanced disease may induce pronounced OS and stimulate increased expression of this antioxidant as an attempt to prevent oxidative damage to oocytes (Donabela et al., 2015). Moreover, alterations in mitochondrial function of CC from infertile women with endometriosis have also been suggested as a possible mechanism involved in oocyte damage (Hsu et al., 2015). Some authors have also evidenced alterations in CC's cell cycle of infertile women with advanced disease (Toya et al., 2000), which may justify the increased apoptosis observed by others in their CC (Díaz-Fontdevila et al., 2009) and, consequently, lead to abnormal folliculogenesis in these women (Toya et al., 2000).

Hypothalamic-pituitary-ovarian Axis and Ovarian Function
Likewise, endometriosis has been identified as a disease related to changes in the hypothalamic-pituitary-ovarian axis, with abnormal luteinizing hormone (LH) and prolactin secretion (Cahill & Hull, 2000; Cunha-Filho et al., 2001), which may result in ovary dysfunction in women with the disease. Moreover, granulosa cells of infertile women with early endometriosis seem to be less sensitive to LH stimulation (Cahill et al., 2003). In this sense, studies point to the occurrence of an abnormal luteal phase (Cunha-Filho et al., 2001; 2003; Schenken et al., 1984) and a longer follicular phase (Cahill et al., 1997) in these patients, what may affect the patterns of estrogen and progesterone secretion (Cahill & Hull, 2000; Cunha-Filho et al., 2003). Accordingly, reduced estrogen, androgen and progesterone, and increased activin were found in the follicular fluid of patients with endometriosis (Cahill & Hull, 2000). Consequently, these alterations may, directly or indirectly, damage follicular growth, reduce dominant follicle size, affect follicles maturation, and compromise ovulation in women with endometriosis (Doody et al., 1988; Schenken et al., 1984; Tummon et al., 1988).

Sperm function
In addition, high growth factors, cytokines, activated macrophages, TNF-α concentrations and OS present in the PF from infertile women with endometriosis may be toxic to sperm function (Aeby et al., 1996; Liu et al., 2000; Mansour et al., 2009b). These altered factors may induce sperm DNA fragmentation (Mansour et al., 2009b), disrupt sperm membrane permeability or integrity (Said et al., 2005), reduce sperm motility (Liu et al., 2000; Oral et al., 1996), impair the interaction between the sperm and the epithelium of the uterine tube (Reeve et al., 2005), promote abnormal sperm acrosome reaction (Arumugam, 1994) and impair sperm-oocyte fusion (Aeby et al., 1996), representing another possible mechanism involved in endometriosis-related infertility.

Endometrial microenvironment
Some authors have also considered the role of the endometrium in infertility related to endometriosis, so that alterations in endometrial receptivity due to late histological maturation or biochemical disturbances in the eutopic endometrium may compromise embryo implantation in women with the disease (Bulletti et al., 2010; Giudice & Kao, 2004). Studies suggest that the endometrium may be functionally altered during the implantation window in these patients (Wei et al., 2009). Among the molecules identified with aberrant expression during the window of implantation in the eutopic endometrium of women with endometriosis there are receptors of progesterone and estrogen (Young, 2013), integrins (Giudice & Kao, 2004), leukemia inhibitory factor (LIF), glicodelin A, (GdA), osteopontin (OPN), lipolysophosphatidic acid receptor 3 (LPA3), HOXA10 (Revel, 2012), which are related to the establishment of endometrial receptivity and/or to the interaction between the endometrium and the embryo (Giudice et al., 2002). On the other hand, recent studies have discussed the relevance of endometrial factor for endometriosis-related infertility (Broi et al., 2017; Da Broi et al., 2017; Garcia-Velasco et al., 2015). Simultaneous expression of crucial genes for endometrial receptivity does not appear to undergo significant changes in infertile women with endometriosis during the implantation window (Broi et al., 2017). Likewise, the presence and stage of development of pinopods, which were once considered classic biomarkers of the implantation window in the human endometrial epithelium (Achache & Revel, 2006; Aghajanova et al., 2003; Nikas, 1999; Nikas & Makrigiannakis, 2003; Nikas & Psychoyos, 1997; Xu et al., 2012), also appear to be similar in women with the disease and controls (Da Broi et al., 2017; Ordi et al., 2003). Recently, Garcia-Velasco et al. (2015) published a pilot study in which samples of eutopic endometrium from infertile women with endometriosis and infertile controls were evaluated using a molecular diagnostic tool (ERA), and showed no difference in the expression of the genes predicted for receptivity between the groups.

CONCLUSIONS
Although the mechanisms involved in endometriosis-related infertility are still not completely understood, some evidences suggest multiple factors that may potentially affect patient's fertility. In addition to the pelvic anatomical alterations likely to compromise the gametic interaction and the altered steroidogenesis, ovulation and disrupted ovarian function, peritoneal changes seem to promote a harmful and pro-oxidative microenvironment, which may compromise the CC and the follicular microenvironment, affecting folliculogenesis and, possibly, the oocyte competence in women with endometriosis. Peritoneal alterations may also damage the spermatozoa and difficult gametes interaction. The role of compromised endometrial receptivity is still controversial; however, recent evidence points to a major role of the oocyte factor in impaired fertility of infertile women with endometriosis.

REFERENCES
Aeby TC, Huang T, Nakayama RT. The effect of peritoneal fluid from patients with endometriosis on human sperm function in vitro. Am J Obstet Gynecol. 1996;174:1779-83.
Medline Crossref

Agarwal A, Saleh RA, Bedaiwy MA. Role of reactive oxygen species in the pathophysiology of human reproduction. Fertil Steril. 2003;79:829-43.
Medline Crossref

Agarwal A, Aponte-Mellado A, Premkumar BJ, Shaman A, Gupta S. The effects of oxidative stress on female reproduction: a review. Reprod Biol Endocrinol. 2012;10:49.
Medline Crossref

Aghajanova L, Stavreus-Evers A, Nikas Y, Hovatta O, Landgren BM. Coexpression of pinopodes and leukemia inhibitory factor, as well as its receptor, in human endometrium. Fertil Steril. 2003;79:808-14.
Medline Crossref

Ahn SH, Monsanto SP, Miller C, Singh SS, Thomas R, Tayade C. Pathophysiology and Immune Dysfunction in Endometriosis. Biomed Res Int. 2015a;2015:795976.
Medline Crossref

Ahn SH, Edwards AK, Singh SS, Young SL, Lessey BA, Tayade C. IL-17A Contributes to the Pathogenesis of Endometriosis by Triggering Proinflammatory Cytokines and Angiogenic Growth Factors. J Immunol. 2015b;195:2591-600.
Medline Crossref

Akande VA, Hunt LP, Cahill DJ, Jenkins JM. Differences in time to natural conception between women with unexplained infertility and infertile women with minor endometriosis. Hum Reprod. 2004;19:96-103.
Medline Crossref

Albertini DF, Combelles CM, Benecchi E, Carabatsos MJ. Cellular basis for paracrine regulation of ovarian follicle development. Reproduction. 2001;121:647-53.
Medline Crossref

Andrade AZ, Rodrigues JK, Dib LA, Romão GS, Ferriani RA, Jordão Junior AA, Navarro PA. Serum markers of oxidative stress in infertile women with endometriosis. Rev Bras Ginecol Obstet. 2010;32:279-85.
Medline Crossref

Arumugam K. Endometriosis and infertility: raised iron concentration in the peritoneal fluid and its effect on the acrosome reaction. Hum Reprod. 1994;9:1153-7.
Medline Crossref

ASRM. Practice Committee of the American Society for Reproductive Medicine. Endometriosis and infertility: a committee opinion. Fertil Steril. 2012;98:591-8.
Medline Crossref

Assou S, Anahory T, Pantesco V, Le Carrour T, Pellestor F, Klein B, Reyftmann L, Dechaud H, De Vos J, Hamamah S. The human cumulus--oocyte complex gene-expression profile. Hum Reprod. 2006;21:1705-9.
Medline Crossref

Bersinger NA, von Roten S, Wunder DM, Raio L, Dreher E, Mueller MD. (PAPP-A and osteoprotegerin, together with interleukin-8 and RANTES, are elevated in the peritoneal fluid of women with endometriosis. Am J Obstet Gynecol. 2006;195:103-8.
Medline Crossref

Broi MGD, Rocha CV, Meola J, Martins WP, Carvalho FM, Ferriani RA, Navarro PA. Expression of PGR, HBEGF, ITGAV, ITGB3 and SPP1 genes in eutopic endometrium of infertile women with endometriosis during the implantation window: a pilot study. JBRA Assist Reprod. 2017;21:196-202.
Medline Crossref

Bulletti C, Coccia ME, Battistoni S, Borini A. Endometriosis and infertility. J Assist Reprod Genet. 2010;27:441-7.
Medline Crossref

Burney RO, Giudice LC. Pathogenesis and pathophysiology of endometriosis. Fertil Steril. 2012;98:511-9.
Medline Crossref

Cahill DJ, Wardle PG, Maile LA, Harlow CR, Hull MG. Ovarian dysfunction in endometriosis-associated and unexplained infertility. J Assist Reprod Genet. 1997;14:554-7.
Medline Crossref

Cahill DJ, Hull MG. Pituitary-ovarian dysfunction and endometriosis. Hum Reprod Update. 2000;6:56-66.
Medline Crossref

Cahill DJ, Harlow CR, Wardle PG. Pre-ovulatory granulosa cells of infertile women with endometriosis are less sensitive to luteinizing hormone. Am J Reprod Immunol. 2003;49:66-9.
Medline Crossref

Carvalho LF, Below A, Abrão MS, Agarwal A. Minimal and mild endometriosis negatively impact on pregnancy outcome. Rev Assoc Med Bras (1992). 2012;58:607-14.
Medline Crossref

Catenacci M, Falcone T. The effect of endometriosis on in vitro fertilization outcome. Minerva Ginecol. 2008;60:209-21.
Medline

Cheong YC, Shelton JB, Laird SM, Richmond M, Kudesia G, Li TC, Ledger WL. IL-1, IL-6 and TNF-alpha concentrations in the peritoneal fluid of women with pelvic adhesions. Hum Reprod. 2002;17:69-75.
Medline Crossref

Choi YS, Cho S, Seo SK, Park JH, Kim SH, Lee BS. Alteration in the intrafollicular thiol-redox system in infertile women with endometriosis. Reproduction. 2015;149:155-62.
Medline Crossref

Cordeiro FB, Cataldi TR, Perkel KJ, do Vale Teixeira da Costa L, Rochetti RC, Stevanato J, Eberlin MN, Zylbersztejn DS, Cedenho AP, Turco EG. Lipidomics analysis of follicular fluid by ESI-MS reveals potential biomarkers for ovarian endometriosis. J Assist Reprod Genet. 2015;32:1817-25.
Medline Crossref

Cranney R, Condous G, Reid S. An update on the diagnosis, surgical management, and fertility outcomes for women with endometrioma. Acta Obstet Gynecol Scand. 2017;96:633-43.
Medline Crossref

Cunha-Filho JS, Gross JL, Lemos NA, Brandelli A, Castillos M, Passos EP. Hyperprolactinemia and luteal insufficiency in infertile patients with mild and minimal endometriosis. Horm Metab Res. 2001;33:216-20.
Medline Crossref

Cunha-Filho JS, Gross JL, Bastos de Souza CA, Lemos NA, Giugliani C, Freitas F, Passos EP. Physiopathological aspects of corpus luteum defect in infertile patients with mild/minimal endometriosis. J Assist Reprod Genet. 2003;20:117-21.
Medline Crossref

Da Broi MG, Malvezzi H, Paz CC, Ferriani RA, Navarro PA. Follicular fluid from infertile women with mild endometriosis may compromise the meiotic spindles of bovine metaphase II oocytes. Hum Reprod. 2014;29:315-23.
Medline Crossref

Da Broi MG, de Albuquerque FO, de Andrade AZ, Cardoso RL, Jordão Junior AA, Navarro PA. Increased concentration of 8-hydroxy-2'-deoxyguanosine in follicular fluid of infertile women with endometriosis. Cell Tissue Res. 2016a;366:231-42.
Medline Crossref

Da Broi MG, Navarro PA. Oxidative stress and oocyte quality: ethiopathogenic mechanisms of minimal/mild endometriosis-related infertility. Cell Tissue Res. 2016b;364:1-7.
Medline Crossref

Da Broi MG, Rocha CV Jr, Carvalho FM, Martins WP, Ferriani RA, Navarro PA. Ultrastructural Evaluation of Eutopic Endometrium of Infertile Women With and Without Endometriosis During the Window of Implantation: A Pilot Study. Reprod Sci. 2017;24:1469-75.
Medline Crossref

Díaz-Fontdevila M, Pommer R, Smith R. Cumulus cell apoptosis changes with exposure to spermatozoa and pathologies involved in infertility. Fertil Steril. 2009;91:2061-8.
Medline Crossref

Donabela FC, Barcelos ID, Pavdovan CC, Meola J, Ferriani RA, Navarro PA. PTGS2 gene expression (COX2) in cummulus oophorus cells of endometriosis and control infertile patients submitted to ICSI. Fertil Steril. 2011;96:S236-7.
Crossref

Donabela F, Meola J, Padovan CC, de Paz CC, Navarro PA. Higher SOD1 Gene Expression in Cumulus Cells From Infertile Women With Moderate and Severe Endometriosis. Reprod Sci. 2015;22:1452-60.
Medline Crossref

Doody MC, Gibbons WE, Buttram VC. Linear regression analysis of ultrasound follicular growth series: evidence for an abnormality of follicular growth in endometriosis patients. Fertil Steril. 1988;49:47-51.
Medline Crossref

Downs SM, Utecht AM. Metabolism of radiolabeled glucose by mouse oocytes and oocyte-cumulus cell complexes. Biol Reprod. 1999;60:1446-52.
Medline Crossref

Du YB, Gao MZ, Shi Y, Sun ZG, Wang J. Endocrine and inflammatory factors and endometriosis-associated infertility in assisted reproduction techniques. Arch Gynecol Obstet. 2013;287:123-30.
Medline Crossref

Eisermann J, Gast MJ, Pineda J, Odem RR, Collins JL. Tumor necrosis factor in peritoneal fluid of women undergoing laparoscopic surgery. Fertil Steril. 1988;50:573-9.
Medline Crossref

FitzHarris G, Siyanov V, Baltz JM. Granulosa cells regulate oocyte intracellular pH against acidosis in preantral follicles by multiple mechanisms. Development. 2007;134:4283-95.
Medline Crossref

Garcia-Velasco JA, Fassbender A, Ruiz-Alonso M, Blesa D, D'Hooghe T, Simon C. Is endometrial receptivity transcriptomics affected in women with endometriosis? A pilot study. Reprod Biomed Online. 2015;31:647-54.
Medline Crossref

Giorgi VS, Da Broi MG, Paz CC, Ferriani RA, Navarro PA. N-Acetyl-Cysteine and l-Carnitine Prevent Meiotic Oocyte Damage Induced by Follicular Fluid From Infertile Women With Mild Endometriosis. Reprod Sci. 2016;23:342-51.
Medline Crossref

Giudice LC, Telles TL, Lobo S, Kao L. The molecular basis for implantation failure in endometriosis: on the road to discovery. Ann N Y Acad Sci. 2002;955:252-64.
Medline Crossref

Giudice LC, Kao LC. Endometriosis. Lancet. 2004;364:1789-99.
Medline Crossref

Goodman LR, Goldberg JM, Flyckt RL, Gupta M, Harwalker J, Falcone T. Effect of surgery on ovarian reserve in women with endometriomas, endometriosis and controls. Am J Obstet Gynecol. 2016;589.e1-589.e6.
Medline Crossref

Gupta S, Agarwal A, Krajcir N, Alvarez JG. Role of oxidative stress in endometriosis. Reprod Biomed Online. 2006;13:126-34.
Medline Crossref

Gupta S, Goldberg JM, Aziz N, Goldberg E, Krajcir N, Agarwal A. Pathogenic mechanisms in endometriosis-associated infertility. Fertil Steril. 2008;90:247-57.
Medline Crossref

Hamamah S, Matha V, Berthenet C, Anahory T, Loup V, Dechaud H, Hedon B, Fernandez A, Lamb N. Comparative protein expression profiling in human cumulus cells in relation to oocyte fertilization and ovarian stimulation protocol. Reprod Biomed Online. 2006;13:807-14.
Medline Crossref

Hamel M, Dufort I, Robert C, Gravel C, Leveille MC, Leader A, Sirard MA. Identification of differentially expressed markers in human follicular cells associated with competent oocytes. Hum Reprod. 2008;23:1118-27.
Medline Crossref

Haouzi D, Hamamah S. Pertinence of apoptosis markers for the improvement of in vitro fertilization (IVF). Curr Med Chem. 2009;16:1905-16.
Medline Crossref

Harada T, Yoshioka H, Yoshida S, Iwabe T, Onohara Y, Tanikawa M, Terakawa N. Increased interleukin-6 levels in peritoneal fluid of infertile patients with active endometriosis. Am J Obstet Gynecol. 1997;176:593-7.
Medline Crossref

Hock DL, Sharafi K, Dagostino L, Kemmann E, Seifer DB. Contribution of diminished ovarian reserve to hypofertility associated with endometriosis. J Reprod Med. 2001;46:7-10.
Medline

Holoch KJ, Lessey BA. Endometriosis and infertility. Clin Obstet Gynecol. 2010;53:429-38.
Medline Crossref

Hosseini E, Mehraein F, Shahhoseini M, Karimian L, Nikmard F, Ashrafi M, Afsharian P, Aflatoonian R. Epigenetic alterations of CYP19A1 gene in Cumulus cells and its relevance to infertility in endometriosis. J Assist Reprod Genet. 2016;33:1105-13.
Medline Crossref

Hsu AL, Townsend PM, Oehninger S, Castora FJ. Endometriosis may be associated with mitochondrial dysfunction in cumulus cells from subjects undergoing in vitro fertilization-intracytoplasmic sperm injection, as reflected by decreased adenosine triphosphate production. Fertil Steril. 2015;103:347-52.e1.
Medline Crossref

Huang B, Li Z, Ai J, Zhu L, Li Y, Jin L, Zhang H. Antioxidant capacity of follicular fluid from patients undergoing in vitro fertilization. Int J Clin Exp Pathol. 2014;7:2273-82.
Medline

Jianini BTGM, Giorgi VS, Da Broi MG, de Paz CC, Rosa E Silva JC, Ferriani RA, Navarro PA. Peritoneal Fluid From Infertile Women With Minimal/Mild Endometriosis Compromises the Meiotic Spindle of Metaphase II Bovine Oocytes. Reprod Sci. 2017;24:1304-11.
Medline Crossref

Jørgensen H, Hill AS, Beste MT, Kumar MP, Chiswick E, Fedorcsak P, Isaacson KB, Lauffenburger DA, Griffith LG, Qvigstad E. Peritoneal fluid cytokines related to endometriosis in patients evaluated for infertility. Fertil Steril. 2017;107:1191-9.e2.
Medline Crossref

Keenan JA, Chen TT, Chadwell NL, Torry DS, Caudle MR. IL-1 beta, TNF-alpha, and IL-2 in peritoneal fluid and macrophage-conditioned media of women with endometriosis. Am J Reprod Immunol. 1995;34:381-5.
Medline Crossref

Kianpour M, Nematbakhsh M, Ahmadi SM, Jafarzadeh M, Hajjarian M, Pezeshki Z, Safari T, Eshraghi-Jazi F. Serum and peritoneal fluid levels of vascular endothelial growth factor in women with endometriosis. Int J Fertil Steril. 2013;7:96-9.
Medline

Lamaita RM, Pontes A, Belo AV, Caetano JP, Andrade SP, Cândido EB, Carneiro MM, Silva-Filho AL. Evaluation of N-acetilglucosaminidase and myeloperoxidase activity in patients with endometriosis-related infertility undergoing intracytoplasmic sperm injection. J Obstet Gynaecol Res. 2012;38:810-6.
Medline Crossref

Lebovic DI, Mueller MD, Taylor RN. Immunobiology of endometriosis. Fertil Steril. 2001;75:1-10.
Medline Crossref

Li R, Albertini DF. The road to maturation: somatic cell interaction and self-organization of the mammalian oocyte. Nat Rev Mol Cell Biol. 2013;14:141-52.
Medline Crossref

Liu Y, Luo L, Zhao H. Changes of cytokines levels in peritoneal fluids of patients with endometriosis and its effect on reproductive activity. J Tongji Med Univ. 2000;20:163-5.
Medline Crossref

Liu F, He L, Liu Y, Shi Y, Du H. The expression and role of oxidative stress markers in the serum and follicular fluid of patients with endometriosis. Clin Exp Obstet Gynecol. 2013;40:372-6.
Medline

Lo Turco EG, Cordeiro FB, Lopes PH, Gozzo FC, Pilau EJ, Soler TB, da Silva BF, Del Giudice PT, Bertolla RP, Fraietta R, Cedenho AP. Proteomic analysis of follicular fluid from women with and without endometriosis: new therapeutic targets and biomarkers. Mol Reprod Dev. 2013;80:441-50.
Medline Crossref

Lolicato F, Brouwers JF, de Lest CH, Wubbolts R, Aardema H, Priore P, Roelen BA, Helms JB, Gadella BM. The cumulus cell layer protects the bovine maturing oocyte against fatty acid-induced lipotoxicity. Biol Reprod. 2015;92:16.
Medline Crossref

Mansour G, Abdelrazik H, Sharma RK, Radwan E, Falcone T, Agarwal A. L-carnitine supplementation reduces oocyte cytoskeleton damage and embryo apoptosis induced by incubation in peritoneal fluid from patients with endometriosis. Fertil Steril. 2009a;91:2079-86.
Medline Crossref

Mansour G, Aziz N, Sharma R, Falcone T, Goldberg J, Agarwal A. The impact of peritoneal fluid from healthy women and from women with endometriosis on sperm DNA and its relationship to the sperm deformity index. Fertil Steril. 2009b;92:61-7.
Medline Crossref

Mansour G, Sharma RK, Agarwal A, Falcone T. Endometriosis-induced alterations in mouse metaphase II oocyte microtubules and chromosomal alignment: a possible cause of infertility. Fertil Steril. 2010;94:1894-9.
Medline Crossref

Marcoux S, Maheux R, Bérubé S. Laparoscopic surgery in infertile women with minimal or mild endometriosis. Canadian Collaborative Group on Endometriosis. N Engl J Med. 1997;337:217-22.
Medline Crossref

Margari KM, Zafiropoulos A, Hatzidaki E, Giannakopoulou C, Arici A, Matalliotakis I. Peritoneal fluid concentrations of β-chemokines in endometriosis. Eur J Obstet Gynecol Reprod Biol. 2013;169:103-7.
Medline Crossref

Mehdizadeh Kashi A, Chaichian S, Ariana S, Fazaeli M, Moradi Y, Rashidi M, Najmi Z. The impact of laparoscopic cystectomy on ovarian reserve in patients with unilateral and bilateral endometrioma. Int J Gynaecol Obstet. 2017:136:200-4.
Medline Crossref

Miller JE, Ahn SH, Monsanto SP, Khalaj K, Koti M, Tayade C. Implications of immune dysfunction on endometriosis associated infertility. Oncotarget. 2017;8:7138-47.
Medline Crossref

Monniaux D. Driving folliculogenesis by the oocyte-somatic cell dialog: Lessons from genetic models. Theriogenology. 2016;86:41-53.
Medline Crossref

Nasiri N, Moini A, Eftekhari-Yazdi P, Karimian L, Salman-Yazdi R, Arabipoor A. Oxidative Stress Statues in Serum and Follicular Fluid of Women with Endometriosis. Cell J. 2017;18:582-7.
Medline Crossref

Nikas G, Psychoyos A. Uterine pinopodes in peri-implantation human endometrium. Clinical relevance. Ann N Y Acad Sci. 1997;816:129-42.
Medline Crossref

Nikas G. Pinopodes as markers of endometrial receptivity in clinical practice. Hum Reprod. 1999;14:99-106.
Medline Crossref

Nikas G, Makrigiannakis A. Endometrial pinopodes and uterine receptivity. Ann N Y Acad Sci. 2003;997:120-3.
Medline Crossref

Oral E, Arici A, Olive DL, Huszar G. Peritoneal fluid from women with moderate or severe endometriosis inhibits sperm motility: the role of seminal fluid components. Fertil Steril. 1996;66:787-92.
Medline Crossref

Ordi J, Creus M, Casamitjana R, Cardesa A, Vanrell JA Balasch J. Endometrial pinopode and alphavbeta3 integrin expression is not impaired in infertile patients with endometriosis. J Assist Reprod Genet. 2003;20:465-73.
Medline Crossref

Oral E, Arici A, Olive DL, Huszar G. Peritoneal fluid from women with moderate or severe endometriosis inhibits sperm motility: the role of seminal fluid components. Fertil Steril. 1996;66:787-92.
Medline Crossref

Ordi J, Creus M, Casamitjana R, Cardesa A, Vanrell JA Balasch J. Endometrial pinopode and alphavbeta3 integrin expression is not impaired in infertile patients with endometriosis. J Assist Reprod Genet. 2003;20:465-73.
Medline Crossref

Reeve L, Lashen H, Pacey AA. Endometriosis affects sperm-endosalpingeal interactions. Hum Reprod. 2005;20:448-51.
Medline Crossref

Revel A. Defective endometrial receptivity. Fertil Steril. 2012;97:1028-32.
Medline Crossref

Ruder EH, Hartman TJ, Blumberg J, Goldman MB. Oxidative stress and antioxidants: exposure and impact on female fertility. Hum Reprod Update. 2008;14:345-57.
Medline Crossref

Said TM, Agarwal A, Falcone T, Sharma RK, Bedaiwy MA, Li L. Infliximab may reverse the toxic effects induced by tumor necrosis factor alpha in human spermatozoa: an in vitro model. Fertil Steril. 2005;83:1665-73.
Medline Crossref

Saito T, Hiroi M, Kato T. Development of glucose utilization studied in single oocytes and preimplantation embryos from mice. Biol Reprod. 1994;50:266-70.
Medline Crossref

Sanchez AM, Viganò P, Somigliana E, Panina-Bordignon P, Vercellini P, Candiani M. The distinguishing cellular and molecular features of the endometriotic ovarian cyst: from pathophysiology to the potential endometrioma-mediated damage to the ovary. Hum Reprod Update. 2014;20:217-30.
Medline Crossref

Santulli P, Chouzenoux S, Fiorese M, Marcellin L, Lemarechal H, Millischer AE, Batteux F, Borderie D, Chapron C. Protein oxidative stress markers in peritoneal fluids of women with deep infiltrating endometriosis are increased. Hum Reprod. 2015;30:49-60.
Medline Crossref

Schenken RS, Asch RH, Williams RF, Hodgen GD. Etiology of infertility in monkeys with endometriosis: luteinized unruptured follicles, luteal phase defects, pelvic adhesions, and spontaneous abortions. Fertil Steril. 1984;41:122-30.
Medline Crossref

Seyhan A, Ata B, Uncu G. The Impact of Endometriosis and Its Treatment on Ovarian Reserve. Semin Reprod Med. 2015;33:422-8.
Medline Crossref

Shaeib F, Khan SN, Ali I, Thakur M, Saed MG, Dai J, Awonuga AO, Banerjee J, Abu-Soud HM. The Defensive Role of Cumulus Cells Against Reactive Oxygen Species Insult in Metaphase II Mouse Oocytes. Reprod Sci. 2016;23:498-507.
Medline Crossref

Shanti A, Santanam N, Morales AJ, Parthasarathy S, Murphy AA. Autoantibodies to markers of oxidative stress are elevated in women with endometriosis. Fertil Steril. 1999;71:1115-8.
Medline Crossref

Sikora J, Mielczarek-Palacz A, Kondera-Anasz Z. Imbalance in cytokines from interleukin-1 family - role in pathogenesis of endometriosis. Am J Reprod Immunol. 2012;68:138-45.
Medline Crossref

Singh AK, Chattopadhyay R, Chakravarty B, Chaudhury K. Markers of oxidative stress in follicular fluid of women with endometriosis and tubal infertility undergoing IVF. Reprod Toxicol. 2013;42:116-24.
Medline Crossref

Singh AK, Dutta M, Chattopadhyay R, Chakravarty B, Chaudhury K. Intrafollicular interleukin-8, interleukin-12, and adrenomedullin are the promising prognostic markers of oocyte and embryo quality in women with endometriosis. J Assist Reprod Genet. 2016;33:1363-72.
Medline Crossref

Szczepańska M, Koźlik J, Skrzypczak J, Mikołajczyk M. Oxidative stress may be a piece in the endometriosis puzzle. Fertil Steril. 2003;79:1288-93.
Medline Crossref

Tamanini C, De Ambrogi M. Angiogenesis in developing follicle and corpus luteum. Reprod Domest Anim. 2004;39:206-16.
Medline Crossref

Tanghe S, Van Soom A, Nauwynck H, Coryn M, de Kruif A. Minireview: Functions of the cumulus oophorus during oocyte maturation, ovulation, and fertilization. Mol Reprod Dev. 2002;61:414-24.
Medline Crossref

Toya M, Saito H, Ohta N, Saito T, Kaneko T, Hiroi M. Moderate and severe endometriosis is associated with alterations in the cell cycle of granulosa cells in patients undergoing in vitro fertilization and embryo transfer. Fertil Steril. 2000;73:344-50.
Medline Crossref

Tummon IS, Maclin VM, Radwanska E, Binor Z, Dmowski WP. Occult ovulatory dysfunction in women with minimal endometriosis or unexplained infertility. Fertil Steril. 1988;50:716-20.
Medline Crossref

Uncu G, Kasapoglu I, Ozerkan K, Seyhan A, Oral Yilmaztepe A, Ata B. Prospective assessment of the impact of endometriomas and their removal on ovarian reserve and determinants of the rate of decline in ovarian reserve. Hum Reprod. 2013;28:2140-5.
Medline Crossref

Wang XM, Ma ZY, Song N. Inflammatory cytokines IL-6, IL-10, IL-13, TNF-α and peritoneal fluid flora were associated with infertility in patients with endometriosis. Eur Rev Med Pharmacol Sci. 2018;22:2513-8.
Medline Crossref

Wei Q, St Clair JB, Fu T, Stratton P, Nieman LK. Reduced expression of biomarkers associated with the implantation window in women with endometriosis. Fertil Steril. 2009;91:1686-91.
Medline Crossref

Wu G, Bersinger NA, Mueller MD, von Wolff M. Intrafollicular inflammatory cytokines but not steroid hormone concentrations are increased in naturally matured follicles of women with proven endometriosis. J Assist Reprod Genet. 2017;34:357-64.
Medline Crossref

Xu B, Sun X, Li L, Wu L, Zhang A, Feng Y. Pinopodes, leukemia inhibitory factor, integrin-β3, and mucin-1 expression in the peri-implantation endometrium of women with unexplained recurrent pregnancy loss. Fertil Steril. 2012;98:389-95.
Medline Crossref

Yoshino O, Osuga Y, Koga K, Hirota Y, Tsutsumi O, Yano T, Morita Y, Momoeda M, Fujiwara T, Kugu K, Taketani Y. Concentrations of interferon-gamma-induced protein-10 (IP-10), an antiangiogenic substance, are decreased in peritoneal fluid of women with advanced endometriosis. Am J Reprod Immunol. 2003;50:60-5.
Medline Crossref

Young SL. Oestrogen and progesterone action on endometrium: a translational approach to understanding endometrial receptivity. Reprod Biomed Online. 2013;27:497-505.
Medline Crossref