Endometriosis-Associated Infertility

1 „Dr Panait Sarbu” Hospital of Obtetrics and Gynaecology, Bucharest, Romania 2 „Carol Davila” University of Medicine and Pharmacy, Bucharest, Romania 3 Department of Public Health and Management, Bucharest, Romania 4 Clinic of Urology, Emergency University Central Military Hospital, Bucharest, Romania 5 Academy of Romanian Scientists Corresponding author: Elvira Bratila, „Dr Panait Sarbu” Hospital of Obtetrics and Gynaecology, Bucharest, Romania. E-mail: elvira.bratila@umfcd.ro Abstract


INTRODUCTION
Endometriosis is defi nined as the presence of endometrial-like tissue outside the uterine cavity and it presumably aff ects 10-15% of reproductive aged women.Th e prevalence of endometriosis appears to be higher in women in Philippines, Indian, Japanese and Korean origin. 1 Clinical manifestations depend upon the site where the ectopic endometrial tissue is located and include dysmenorrhea, dyspareunia, chronic pelvic pain, infertility, but the possibility of being asymptomatic exists.A major drawback that could result in late that region [10][11][12][13][14][15][16][17] , aff ecting by infi ltration or compression many anatomical structures [18][19][20][21][22][23][24] .
Another possible pathogenesis of endometriosis comes from newer research in stem cells.It was proven that de novo endometrial tissue can develop from endogenous stem cells 6,7 .In a study dating back from 2004 it was demonstrated that female bone marrow transplant recipients who received bone marrow from a single mismatched related donor had donor-derived endometrial cells in endometrial biopsies 25 .Th is implies that non-uterine stem cells can regenerate endometrial tissue, but may also lead to ectopic implants.

INFERTILITY IN ENDOMETRIOSIS
Endometriosis is a leading cause of infertility through various mechanism, but not all women with endometriosis have a diffi culty in conceiving.
Th e main mechanism is the altered anatomy.Pelvic adhesions lead to impaired oocyte release and ostial pick-up, altered sperm mobility, myometrial contractions which in turn lead to altered embryo transport and fertilization.In fact, endometriosis aff ects all stages of the reproduction process.Th e infl ammatory cells in the peritoneal fl uid and endometriomas have damaging eff ects upon the oocyte, embryo and sperm, impair tubal function and decrease tubal mobility 7 .All this leads to a lower fertilization rate both in natural and in vitro cycles.
Th e ectopic endometrial cells interact with immune mechanisms, the starting point is the activation of repairing mechanisms of the destroyed tissue.Infl ammatory mediators are released by macrophages, dendritic cells and mast cells leading to vasodilation, increased endothelial permeability and extravasation of white blood cells.In the peritoneal fl uid there are elevated levels of interleukines (IL 1, 6, 7, 8, 17) TNF, VEGF which create a hostile environment for folliculogenesis, sperm and implantation 1,7,26 .
Even superfi cial peritoneal implants produce infl ammatory cytokines and chemokines causing an increased oxidative stress and an altered hormonal profile.Th e endometriomas directly aff ect folliculogenesis leading to poor oocyte and embryo quality and also poor response during ovarian stimulation 27 .Hemolysis of trapped blood leads to high iron level within the cyst suggesting cytotoxic oxidative stress 1 .
Endometriosis negatively aff ects the physiology of granulosa cells, leading to increased apoptosis and alteration of steroidogenesis by decreasing the expressi-novaginography with ultrasound gel should be performed in conjunction with transvaginal sonography 3 .
Another challenge is diagnosing colorectal endometriosis.Th is is one of the most severe forms of the disease and it is almost impossible to detect at physical examination alone, especially when the implants are located above the sigmoid colon 4 .Magnetic resonance imaging is considered an useful diagnostic tool in this situation, but recently a diff erent approach has been studied.Th e combination of magnetic resonance imaging and computed tomography-based virtual colonoscopy leads to greater accuracy in the assessment of both small and large bowel endometriosis 5,6 .
Th e pathogenesis of endometriosis is mainly explained by various theories.Th e most well known and accepted theory is the one proposed by Sampson in 1920' which states that during menstruation, a certain number of endometrial cells migrate via the tubal ostia into the peritoneal cavity where they attach, proliferate and create an independent blood supply 2,7 .However, not all women with retrograde menstruation have endometriosis, so other factors must contribute to its development.Retrograde menstruation has a higher prevalence in women with congenital mullerian anomalies.
Another theory states that ectopic endometrial implants arise from coelomic metaplasia.Th is was proposed by Ferguson in the 1960' 2,7 .Th e coelomic cells in the peritoneum can diff erentiate into endometrial cells due to undetermined stimuli.One important contributing factor is altered immunity.Patients with endometriosis have an altered cell mediated immnity translating into defective activity of leukocytes and NK-cells.Th is prevents the proper clearance of the refl uxed endometrial cells 7 .
Rare extraperitoneal locations of endometriosis such as pulmonary, cerebral or umbilical cannot be explained neither by retrograde menstruation nor by coelomic metaplasia, but by lymphovascular spread of viable endometrial cells.Secondary umbilical endometriosis is unusual and is mainly associated with abdominal surgery involving the umbilicus, but primary umbilical endometriosis (Villar's nodule) is even more uncommon.Few such cases have been reported, so the pathogenesis of this condition is controversial.Some theories imply that the endometrial cells migrate to the umbilicul through the abdominal cavity, the lymphatic system and the umbilical vessels or the endometrial cells proliferate from initial extraperitoneal disease along the urachus 8,9 .
Migration of endometrial cells in retroperitoneum can develop symptomatology similar with any mass in on of aromatase.Th is causes an imbalance in estrogen production, lower estradiol concentration at the preovulatory stage and at the LH surge.Th e duration of the follicular phase is extended in these patients, as the LH surge is delayed or biphasic leading to an altered postovulatory progesterone secretion that might aff ect oocyte maturation 1,28 .
Endometriosis modifi es the follicular oxidative stress status and the subsequent reactive oxygen species produce meiotic abnormalities and chromosomic instability and thereby reducing the oocyte quality.Th ese oocytes have a streghtened zona pellucida and this might aff ect fertilization, dissolution of the zona pellucida and the ability of the embryo to undergo hatching and implantation.Studies in this fi eld are somewhat limited due to ethical reasons and the oocyte quality was mostly studied indirectly by evaluating the cumulus cells and the follicular fl uid 28 .
Recently, the spindle morphology is used as a marker of oocyte quality.A study from 2014 revealed that the oocytes retrieved from women with endometriosis had a higher percentage of spindle abnormalities compared to women undergoing IVF due to male factor (66.7% versus 16%) as well a higher apoptosis level (80% versus 22.2%) 28,29 .
Cytoplasm composition is another indicator of oocyte and embryo development.Compared to other cells, the cytoplasm of mature oocytes has a higher mitochondrial content, up to 105 mitochondria.It was discovered that the oocytes of women with endometriosis have a higher percentage of abnormal mitochondria and a lower number overall (84.6±39.8versus 50.7±288.5) 27,30.
Eff ects of endometriosis upon the endometrium are also of great importance.A study from 2012 proved that cells can migrate from ectopic endometrial implants back to the uterine endometrium.Th ese migrating cells had a Wn7A up-regulation expression which led to endometrial disturbance during implantation window.Th e Wn7A gene is involved in estrogen-mediated uterine growth and implantion 7,31 .Another gene involved is the Hoxa 10 .Cyclical endometrial expression of this gene leads to endometrial regeneration.Women with endometriosis have lower levels of the Hoxa 10 gene and this could explain the lower implantation rates.Lower implantation rates are also attributed to high levels of matrix metalloproteinase which cause persistent endometrial breakdown and low levels of -integrin which impair embryo attachment 7 .

MEDICAL MANAGEMENT
Current available treatment options for endometriosis mainly address pain.Th ese incluse combined oral contraceptives, progestins, androgens, GnRh agonists 2,32 .All of them aim at reducing the circulating estrogen levels, but no do not have any eff ect upon infertility.Moreover, they delay the moment of conception, so they are not considered an option for women desiring a pregnancy.A valid example is depot medroxyprogesterone acetate.Although it is highly eff ective in relieving pain, it has lasting eff ects upon ovulation suppresion long beyond the duration of treatment33.A exception to this are women undergoing in vitro fertilization.It was proven that GnRh agonist treatment before ovarian stimulation leads to increased oocytes and higher implantation rates.However a review from 2010 stipulated that although pretreatment with GnRh agonists led to an improved ovarian response and a greater number of mature oocytes, it did not increase the overall pregnancy rate. 7

SURGICAL MANAGEMENT
Nowadays it is generally accepted that laparoscopy is the gold standard in endometriosis, as it is both diagnostic and therapeutic.However, the decision to operate a patient with endometriosis should be tailored according to the individual's characteristics: age, symptoms, stage of disease, ovarian reserve, length of infertility, associated factors of infertility.Taking all of them into account this patient has to be managed by a multidisciplinary team, including a gynecologist, a general surgeon, a fertility specialist and a radiologist.Th e benefi ts of surgery are the restoration of normal pelvic anatomy, excision of endometriotic implants and ovarian endometriomas, thus reducing the infl amatory milieu.
An important aspect has to be taken into consideration when dealing with a patient with endometriosis wishing to conceive: counselling the patient about her real changes to conceive before and after surgery 27 .A well known detrimental eff ect of surgery is the further decline in ovarian reserve in an already infertile patient.Retrospective studies have demonstrated a signifi cantly lower antral follicle count and ovarian volume after laparoscopic excision 33 .
Fertility specialists have stipulated that medical treament with GnRh agonists after surgery improves pregnancy rates in women with endometriosis undergoing IVF (in vitro fertilization).When taking account metriosis negatively impacts preganancy rates in natural and in vitro cycles, but still IVF is the best chance for a woman to get pregnant.A meta-analysis of 22 studies including over 2000 in vitro cycles of women with endometriosis and over 4000 IVF cycles for other causes of infertility proved that fertilization rates, implantation rates and pregnancy rates were all lower in the endometriosis group 33 .
In patients with stage I/II endometriosis IVF is the best option for an increased pregnancy rate, but it is not clear whether surgery would further improve the outcome in this scenario.But a study from 2015 strongly recommends surgery as a fi rst line tool before IVF even in minimal-mild endometriosis, as it doubles the pregnancy rate.Also, in patients who failed to conceive spontaneously after surgery, IVF is more eff ective than repeat surgery 40 .Pregnancy rates are improved when GnRh agonists are administered prior to IVF, but don't have any benefi cial eff ect upon women aiming at spontaneous conception, while also adding an unwanted time delay 1 .After GnRh agonists administration, higher FSH doses and a longer stimulation period are required.
When dealing with older women, surgery may not be the fi rst option, as it leads to a decline in ovarian reserve, except for cases with large ovarian masses which intercept the access to the ovary during oocyte pickup 1 .
Oocyte donation programs can be taken into consideration as a last resort.Patients with endometriosis have a similar implantation and pregnancy rate as other recipients when the oocytes came from healthy donors.However, patients who receive embryos derived from endometriotic ovaries display a lower implantation rate and presumably this is derived from the oocyte quality 28 .

CONCLUSION
Endometriosis is a heterogeneous disease with numerous implications in the reproductive process, including mechanical, molecular and genetical.Th e best method for treatment of infertility is IVF, but the decision should be made on an individual basis, also taking into account the age, ovarian reserve, other causes of infertility, duration of infertility and the male partner.Undoubtedly the management of these patients should be done by a multidisciplinary team.
the technique used, it seems that excisional surgery is associated with better spontaneous pregnancy rates in a 9-12 months interval as opposed to ablative surgery 27 .Two randomized control studies of laparoscopic management of endometriomas have demonstrated an increased pregnancy rate when performing cyst wall excision as opposed to cyst wall ablation, with pregnancy rates of 61% versus 23.4% after a two year interval 33 .
Deep infi ltrating endometriosis (DIE) also negatively aff ects pregnancy rates.A retrospective study from 2009 compared the IVF results in women with DIE submitted to laparoscopic treatment before IVF to women not operated before IVF.Th e study included 179 women divided in two groups, IVF only (105) and surgery and IVF (64).Th e pregnancy rates were 2.45 times higher in the group of women submitted to surgery before IVF.When DIE is associated with endometriomas, the pregnancy rate is declined furthermore, as compared to DIE alone (82.5% versus 69.4%) 27,34,35 .
A new scoring system has proved useful in the last years, the endometriosis fertility index (EFI).EFI is used for the prediction of fertility following surgery.It has a more positive correlation when estimating the pregnancy rate than AFS (American Fertility Society) classifi cation.Patients with EFI >5 after twelve months from surgery are candidates for IVF 1,36 .
Following surgery it is important to off er hormonal treatment until the woman decides to procreate because endometriosis is a chronic relapsing disease.Studies have shown that an individualised approach is needed forasmuch as the laparoscopic description of the ectopic implants does not off er adequate information about the aggressiveness or the progression capacity of the disease.One direction is choosing the treatment based on the molecular markers identifi ed in the ectopic implants using immunohistochemistry: estrogen receptors, progesterone receptors, the cellular proliferation marker Ki-67 and the marker of inhibition of cellular apoptosis Bcl-2.Estrogen and progesteron receptors expression is modifi ed in endometriotic implants compared with normal endometrium.Th e low expression of the hormonal receptors could explain the persistence of symptoms and the progression of the disease under hormonal treatment 37,38,39 .

ENDOMETRIOSIS AND IVF
Treatment options in managing infertility associated with endometriosis include surgical intervention and ovarian stimulation with IVF.As stated above, endo-Th e authors declare that all the procedures and experiments of this study respect the ethical standards in the Helsinki Declaration of 1975, as revised in 2008(5), as well as the national law.Informed consent was obtained from all the patients included in the study.

Compliance with ethics requirements:
Th e authors declare no confl ict of interest regarding this article.