Infertility is one of the major increasing gynecological problems worldwide. When comprehensive investigations of the infertile couple are normal, about 15-25 % of couples still have no apparent reason for their infertility and are thus classified as unexplained infertility. Unexplained infertility may arise from a subtle defect in the fecundability that cannot be detected with routine infertility evaluation, diminished ovarian reserve, disordered oogenesis, subtle endometriosis or suboptimal endometrial receptivity.
Impaired uterine receptivity is one of the major reasons for the failure of pregnancy in unexplained infertility, recurrent pregnancy loss and assisted reproductive techniques (ART). It is estimated that up to two-thirds of implantation failures are due to defects in endometrial receptivity.
Implantation occurs during a very short period in the secretory phase of the menstrual cycle called the window of implantation between days 20 and 24. It is a complex process that requires synchronization of events in the developing embryo and receptive endometrium .This period is manifested by the expression of certain peptides and proteins that can serve as biomarkers of uterine receptivity. Some of these markers are leukemia inhibitory factor (LIF), integrin-b3, heparin-binding epidermal growth factor–like growth factor (HB-EGF), and Mucin- 1 (MUC-1). LIF is a polyfunctional cytokine that was expressed along with its receptor(LIFR) in the endometrium ,it was found that maximal expression occur in the mid-luteal phase this explain its important role in implantation.
As an anti-adhesion molecule, MUC-1 prevents the adherence of blastocysts to the endometrium except at a specific site. The expression of MUC-1 is extraordinarily lower in the endometrium of women with unexplained infertility during the implantation window compared with normal fertile women, so MUC-1 is an important factor in determining endometrial receptivity in unexplained infertility &RIF.
Angiogenesis and good uterine blood flow are essential for both endometrial growth and embryo development. As a result endometrial vascularity has been considered to play a critical role in endometrial receptivity formation and pregnancy maintenance. Using ultrasound examination of the endometrium is a commonly used non invasive method to assess the endometrial receptivity.
Over the last decade, research to improve success rates in reproductive medicine has focused predominantly on the understanding and optimization of embryo quality. However, the emergence of personalized medicine in ovulation induction and embryology has shifted the focus to assess the individual status of the endometrium. The endometrial receptivity array(ERA) was developed in 2011.The ERA consists of a customized microarray based on the transcriptomic signature of human ER, specifically when the human endometrium is receptive to blastocyst adhesion this leads to the idea “personalized embryo transfer” (pET) or transferring an embryo based on the woman's personalized WOI.
In this study sixty women presented to the Gynecological Outpatient Clinic at Benha University Hospital, were recruited and divided into study and control groups:
Study group included 30 patients, with primary unexplained infertility for at least 2 years as diagnosed by the following criteria: Normal semen analysis according to modified WHO 2010 criteria-Tubal patency proved by hysterosalpingography- Ovulatory women proved by; mid-luteal serum progesterone level≥ 10ng/ml.
Control group included 30 healthy fertile women with no history of recurrent abortion (had at least one live child) .
All patients were subjected to Full history taking and transvaginal sonography was done starting from the nineth day of the cycle every other day until the dominant follicle size reached 18 mm then urinary LH test was initiated, Once the dipstick test was positive, each subject would return to our clinic within 48 hours and pelvic ultrasonography was done to confirm ovulation then at the 7th day after natural ovulation (mid luteal phase = implantation window) the following were done:
A) Ultrasound examination: The endometrial thickness and pattern were assessed then Uterine and Spiral artery Doppler examination was performed transvaginally in the 2D mode, the gate of the Doppler was positioned until the vessel with good signals was identified on the screen. Pulsed Doppler waveforms was obtained and pulsatility index (PI) and resistance index (RI), were calculated electronically for both arteries.
B) Endometrial biopsy: Endometrial biopsy specimens were obtained using sterile Novak’s curette . The samples were washed immediately in normal saline and were placed in 10% buffered formalin and sent for immunohistochemical examination to Study: The expression of LIF, and MUC1 by use of a streptavidin–biotin complex (SABC) method: by use of primary antibody, (LIF: Rabbit polyclonal IgG antibody, 1:100, Gene Tex) and (MUC-1 : Rabbit polyclonal IgG antibody, ready to use, Thermo Scientific).
Comparison between both groups regarding patients characteristics (age ,cycle length) there was no statistically significant difference. Also ultrasound examination showed no statistically significant difference between study and control group as regard endometrial thickness (9.26±1.24 vs 9.30±1.03) respectively and endometrial pattern, multilayered pattern (70% vs 83.3% ) respectively , but uterine RI and PI in the study group were significantly increased (0.90±0.06 vs 0.77±0.04 and 2.06±0.13 vs 1.81±0.10) respectively .Both RI and PI of spiral arteries showed significantly high impedance (0.61±0.05 vs 0.47±0.04 and 0.85±0.05 vs 0.65±0.06 ) respectively.
The endometrial expression of LIF was found to be impaired in the infertility group, the results were observed to be of weak expression ( 46.7%) in study groug vs (13.3% )in the control group and negative expression (30 %) vs (13.3%) respectively with high statistical significant difference between both groups.
For MUC-1 our results observed weak expression (40%) in study group vs (10%) in the control group and negative expression (16.7%) vs (0.0%) respectively with high statistical significant difference between both groups.
In conclusion, Peri-implantation endometrial perfusion is impaired in women with unexplained infertility and also the expression of Leukemia Inhibitory Factor (LIF) and Mucin-1(MUC-1) in the endometrium, that could be used as a biochemical marker of endometrial receptivity in unexplained infertility and repeated implantation failure.
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