I. Aging of the human endometrium: a basic morphological and immunohistochemical study

Endometrial receptivity in women of advanced age: an underrated factor in infertility

BACKGROUND

Modern lifestyle has led to an increase in the age at conception. Advanced age is one of the critical risk factors for female-related infertility. It is well known that maternal age positively correlates with the deterioration of oocyte quality and chromosomal abnormalities in oocytes and embryos. The effect of age on endometrial function may be an equally important factor influencing implantation rate, pregnancy rate, and overall female fertility. However, there are only a few published studies on this topic, suggesting that this area has been under-explored. Improving our knowledge of endometrial aging from the biological (cellular, molecular, histological) and clinical perspectives would broaden our understanding of the risks of age-related female infertility.

OBJECTIVE AND RATIONALE

The objective of this narrative review is to critically evaluate the existing literature on endometrial aging with a focus on synthesizing the evidence for the impact of endometrial aging on conception and pregnancy success. This would provide insights into existing gaps in the clinical application of research findings and promote the development of treatment options in this field.

SEARCH METHODS

The review was prepared using PubMed (Medline) until February 2023 with the keywords such as 'endometrial aging', 'receptivity', 'decidualization', 'hormone', 'senescence', 'cellular', 'molecular', 'methylation', 'biological age', 'epigenetic', 'oocyte recipient', 'oocyte donation', 'embryo transfer', and 'pregnancy rate'. Articles in a language other than English were excluded.

OUTCOMES

In the aging endometrium, alterations occur at the molecular, cellular, and histological levels suggesting that aging has a negative effect on endometrial biology and may impair endometrial receptivity. Additionally, advanced age influences cellular senescence, which plays an important role during the initial phase of implantation and is a major obstacle in the development of suitable senolytic agents for endometrial aging. Aging is also accountable for chronic conditions associated with inflammaging, which eventually can lead to increased pro-inflammation and tissue fibrosis. Furthermore, advanced age influences epigenetic regulation in the endometrium, thus altering the relation between its epigenetic and chronological age. The studies in oocyte donation cycles to determine the effect of age on endometrial receptivity with respect to the rates of implantation, clinical pregnancy, miscarriage, and live birth have revealed contradictory inferences indicating the need for future research on the mechanisms and corresponding causal effects of women's age on endometrial receptivity.

WIDER IMPLICATIONS

Increasing age can be accountable for female infertility and IVF failures. Based on the complied observations and synthesized conclusions in this review, advanced age has been shown to have a negative impact on endometrial functioning. This information can provide recommendations for future research focusing on molecular mechanisms of age-related cellular senescence, cellular composition, and transcriptomic changes in relation to endometrial aging. Additionally, further prospective research is needed to explore newly emerging therapeutic options, such as the senolytic agents that can target endometrial aging without affecting decidualization. Moreover, clinical trial protocols, focusing on oocyte donation cycles, would be beneficial in understanding the direct clinical implications of endometrial aging on pregnancy outcomes.

Contemporary evaluation of women and girls with abnormal uterine bleeding: FIGO Systems 1 and 2

Abnormal uterine bleeding (AUB) is common, often debilitating, and may affect over 50% of reproductive-aged women and girls. Whereas AUB is a collection of symptoms that include intermenstrual bleeding and abnormalities in period duration, cycle length, and regularity, it is heavy menstrual bleeding (HMB) that is most contributory to iron deficiency and related anemia. It is apparent that AUB, in general, and HMB, in particular, remain underrecognized and underreported. FIGO created two systems for assessing and classifying AUB. FIGO System 1 defines the bleeding pattern using four primary descriptors: frequency, duration, regularity, and flow volume. FIGO System 2 provides a structured classification system of possible causes of AUB, using the acronym PALM-COEIN. "PALM" refers to structural causes of AUB (Polyp, Adenomyosis, Leiomyoma, Malignancy), and "COEI" refers to nonstructural causes (Coagulopathy, Ovulatory dysfunction, Endometrial, and Iatrogenic). The "N" is reserved for those entities that are currently not otherwise classified. Using FIGO System 1 as a gateway to FIGO System 2 streamlines the investigation of reproductive-aged women and girls with AUB. Understanding the pathogenesis of the FIGO System 2 "PALM-COEIN" causes helps interpret investigations and the onward management of AUB. Numerous evidence gaps exist concerning AUB; however, if researchers and trialists universally adopt FIGO Systems 1 and 2 for the assessment and diagnosis of AUB, clear translatable research findings can be applied globally.

Digital Cell Atlas of Mouse Uterus: From Regenerative Stage to Maturational Stage

Endometrium undergoes repeated repair and regeneration during the menstrual cycle. Previous attempts using gene expression data to define the menstrual cycle failed to come to an agreement. Here we used single-cell RNA sequencing data of C57BL/6J mice uteri to construct a novel integrated cell atlas of mice uteri from the regenerative endometrium to the maturational endometrium at the single-cell level, providing a more accurate cytological-based elucidation for the changes that occurred in the endometrium during the estrus cycle. Based on the expression levels of proliferating cell nuclear antigen, differentially expressed genes, and gene ontology terms, we delineated in detail the transitions of epithelial cells, stromal cells, and immune cells that happened during the estrus cycle. The transcription factors that shaped the differentiation of the mononuclear phagocyte system had been proposed, being Mafb, Irf7, and Nr4a1. The amounts and functions of immune cells varied sharply in two stages, especially NK cells and macrophages. We also found putative uterus tissue-resident macrophages and identified potential endometrial mesenchymal stem cells (high expression of Cd34, Pdgfrb, Aldh1a2) in vivo. The cell atlas of mice uteri presented here would improve our understanding of the transitions that occurred in the endometrium from the regenerative endometrium to the maturational endometrium. With the assistance of a normal cell atlas as a reference, we may identify morphologically unaffected abnormalities in future clinical practice. Cautions would be needed when adopting our conclusions, for the limited number of mice that participated in this study may affect the strength of our conclusions.

Uterine bleeding: how understanding endometrial physiology underpins menstrual health

Menstruation is a physiological process that is typically uncomplicated. However, up to one third of women globally will be affected by abnormal uterine bleeding (AUB) at some point in their reproductive years. Menstruation (that is, endometrial shedding) is a fine balance between proliferation, decidualization, inflammation, hypoxia, apoptosis, haemostasis, vasoconstriction and, finally, repair and regeneration. An imbalance in any one of these processes can lead to the abnormal endometrial phenotype of AUB. Poor menstrual health has a negative impact on a person's physical, mental, social, emotional and financial well-being. On a global scale, iron deficiency and iron deficiency anaemia are closely linked with AUB, and are often under-reported and under-recognized. The International Federation of Gynecology and Obstetrics have produced standardized terminology and a classification system for the causes of AUB. This standardization will facilitate future research endeavours, diagnosis and clinical management. In a field where no new medications have been developed for over 20 years, emerging technologies are paving the way for a deeper understanding of the biology of the endometrium in health and disease, as well as opening up novel diagnostic and management avenues.

Predictive factors for successful pregnancy in an egg-sharing donation program

Objective

To investigate the predictive factors for successful pregnancy in oocyte recipient ICSI cycles in an egg-sharing donation program.

Methods

Analysed data were obtained via chart review of 1505 vitrified oocytes donated from 268 patients to 225 oocyte recipients, undergoing 307 ICSI cycles. Patients were participating in an egg-sharing donation program between January 2015 and May 2017. Adjusted generalised linear models were used to investigate the impact of oocyte donor and recipient characteristics on recipients’ pregnancy achievement.

Results

Implantation rate in the oocyte donor was highly correlated with pregnancy achievement in the oocyte recipient’s cycles (ExpB: 1.181, CI: 1.138-1.226, p<0.001). The ROC curve analysis demonstrated that the implantation rate in the oocyte donor has a strong predictive value for pregnancy success in the oocyte recipient (area under the curve: 0.98, CI: 0.95-0.99, p<0.001). Pregnancy in oocyte donors and recipients were highly associated (ExpB: 54.6, CI: 28.1-105.8, p<0.001), regardless of the oocyte recipient’s age. In oocyte recipients, the high-quality embryos rates on days 2 (ExpB: 3.397, CI: 1.635-7.054, p=0.001) and 3 (ExpB: 6.629, CI: 1.185-37.092, p=0.031), and blastocyst development rates (ExpB: 2.331, CI: 1.086-5.001, p=0.030) were positively associated with pregnancy outcome.

Conclusion

The strong association in pregnancy success between donors and recipients, and the lack of correlation between donor characteristics and cycles’ outcomes, demonstrate the power of oocyte quality on the success of ICSI treatment.

No. 346-Advanced Reproductive Age and Fertility

OBJECTIVE

To improve awareness of the natural age-related decline in female and male fertility with respect to natural fertility and assisted reproductive technologies (ART), provide recommendations for their management, and to review investigations in the assessment of ovarian aging.

OPTIONS

This guideline reviews options for the assessment of ovarian reserve and fertility treatments using ART with women of advanced reproductive age presenting with infertility.

OUTCOMES

The outcomes measured are the predictive value of ovarian reserve testing and pregnancy rates with natural and assisted fertility.

EVIDENCE

Published literature was retrieved through searches of PubMed or Medline, CINAHL, and The Cochrane Library in June 2010, using appropriate key words ("ovarian aging," "ovarian reserve," "advanced maternal age," "advanced paternal age," and "assisted reproductive technology"). Results were restricted to systematic reviews, randomized controlled trials/controlled clinical trials, and observational studies. There were no date or language restrictions. Searches were updated on a regular basis and incorporated into the guideline to December 2010.

VALUES

The quality of evidence was rated using the criteria described in the Report of the Canadian Task Force on Preventive Health Care. Recommendations for practice were ranked according to the method described in that report.

BENEFITS, HARMS, AND COSTS

Primary and specialist health care providers and women will be better informed about ovarian aging and the age-related decline in natural fertility and about options for ART.

RECOMMENDATIONS

N o 346-Âge génésique avancé et fertilité

OBJECTIFS

Sensibiliser la population à la baisse naturelle de la fertilité avec l'âge, chez les femmes et les hommes, et à l'égard de la reproduction naturelle et des technologies de procréation assistée (TPA); formuler des recommandations de prise en charge; et analyser les méthodes d'évaluation du vieillissement ovarien.

OPTIONS

La présente directive clinique passe en revue les options offertes pour l'évaluation de la réserve ovarienne et pour le traitement de l'infertilité faisant appel aux TPA chez les femmes d'âge génésique avancé infertiles.

ISSUES

Les issues mesurées sont les valeurs prédictives de l'évaluation de la réserve ovarienne et les taux de grossesse découlant de la fertilité naturelle et de la fertilité assistée. DONNéES: Nous avons examiné des études publiées récupérées au moyen de recherches dans PubMed, Medline, CINAHL et la Bibliothèque Cochrane en juin 2010 à l'aide de mots-clés appropriés (ovarian aging, ovarian reserve, advanced maternal age, advanced paternal age, et assisted reproductive technology). Nous n'avons tenu compte que des résultats provenant de revues systématiques, d'essais cliniques, randomisés ou non, et d'études observationnelles. Aucune restriction de date ou de langue n'a été employée. Les recherches ont été refaites régulièrement, et les résultats ont été incorporés à la directive clinique jusqu'en décembre 2010.

VALEURS

La qualité des données a été évaluée au moyen des critères énoncés dans le rapport du Groupe d'étude canadien sur les soins de santé préventifs. Les recommandations quant à la pratique ont été classées conformément à la méthode décrite dans ce rapport. AVANTAGES, DéSAVANTAGES ET COûTS: Les patientes et les fournisseurs de soins primaires et spécialisés seront mieux renseignés sur le vieillissement ovarien, la baisse de la fertilité naturelle liée à l'âge et les TPA.

RECOMMENDATIONS

Long-term progestin contraceptives (LTPOC) induce aberrant angiogenesis, oxidative stress and apoptosis in the guinea pig uterus: A model for abnormal uterine bleeding in humans

Background

Irregular uterine bleeding is the major side effect of, and cause for, discontinuation of long-term progestin-only contraceptives (LTPOCs). The endometria of LTPOC-treated women display abnormally enlarged, fragile blood vessels (BV), decreased endometrial blood flow and oxidative stress. However, obtaining sufficient, good quality tissues have precluded elucidation of the mechanisms underlying these morphological and functional vascular changes.

Methods

The current study assessed the suitability of the guinea pig (GP) as a model for evaluating the uterine effects of LTPOC administration. Thus GPs were treated with a transdermal pellet for 21 days and examined for endometrial histology, angiogenic markers as well as markers of oxidative stress and apoptosis.

Results and Discussion

We now demonstrate that GP uteri were enlarged by both estradiol (E2) and medroxyprogesterone acetate (MPA) (p < 0.001). Effects of MPA on uterine weight differed significantly depending on E2 levels (p < 0.001), where MPA opposed the E2 effect in combined treatments. Angiogenesis parameters were similarly impacted upon: MPA alone increased BV density (p = 0.036) and BV average area (p = 0.002). The presence of E2 significantly decreased these parameters. These changes were associated with highly elevated of the lipid peroxidation product, 8-isoprostane (8-isoP) content in E2+MPA-treated and by nuclear 8-OH-deoxyguanosine (8oxoG) staining compared to all other groups (p < 0.001). Abnormalities in the E2+MPA group were consistent with chromatin redistribution, nuclear pyknosis, karyolysis and increased apoptosis as observed by a marked increase in TUNEL labeling.

Conclusions

LTPOC exposure alters endometrial vascular and tissue morphology consistent with oxidative stress and apoptosis in a complex interplay with endogenous estrogens. These findings are remarkably similar to in vivo change observed in the human uterus following LTPOC administration. Hence, the GP is an excellent model for the study of LTPOC effects on the uterus and will be extremely useful in determining the mechanistic pathways involved in this process which cannot be conducted on humans.

Follicular and luteal phase endometrial thickness and echogenic pattern and pregnancy outcome in oocyte donation cycles

PURPOSE

To study the effect of endometrial thickness (ET) and echogenic pattern (EP) in oocyte donation cycles upon pregnancy outcomes.

METHODS

Seventy-nine cycles resulting in blastocyst embryo transfer were evaluated. Donors underwent ovarian hyperstimulation using rFSH and GnRH-antagonist. Recipients were synchronized to donors using GnRH-agonist down-regulation followed by fixed dose of estrogen (E2) and progesterone (P4) following hCG. Transvaginal ultrasound (US) obtained ET and EP 10-11 days after initiation of E2 and on day of embryo transfer. Primary outcome was ET and EP in pregnant and non-pregnant cycles. Stimulation and embryology data was analyzed in donors to assess differences prior to transfer.

RESULTS

Fifty-nine cycles resulted in clinical pregnancy. No differences were observed in pregnant vs. non-pregnant cycles in proliferative or secretory ET and EP. Similar baseline and stimulation characteristics were found in pregnant and non-pregnant cycles. Regression analysis showed end thickness were not predictive of pregnancy outcomes.

CONCLUSIONS

Endometrial characteristics in recipients prior to and following progesterone were not predictive of pregnancy outcomes.

Subfertility: causes, treatment and outcome

Common causes of subfertility include ovulatory disorders, tubal disease, peritoneal adhesions, endometriosis, uterine abnormalities, abnormalities of sperm and advancing female age. Infertility is unexplained after thorough evaluation in about 5-10% of cases. Significant caveats must be attached to the interpretation of available data regarding infertility treatments. Successful ovulation induction in anovulatory women is possible for nearly all women except in cases of ovarian failure. Surgery is an option for some patients with tubal damage, adhesions, endometriosis and uterine abnormalities. Male factor infertility may be amenable to treatment of a specific cause, but is often empirical with the use of intra-uterine insemination (IUI) or in vitro fertilization (IVF). Egg donation is currently the most effective treatment available for age-related infertility when other treatments have not been successful. Couples with unexplained infertility may be effectively treated with ovulation induction plus IUI or IVF.

Cell cycle analysis and detection of proliferative cell nuclear antigen of the endometrium after hormone replacement therapy

BACKGROUND

To understand the effect of sequential combined hormone replacement therapy (HRT) on the postmenopausal endometrium.

METHODS

Sonographic endometrial thickness, endometrial histopathology, flow cytometric cell cycle analysis and the level of proliferative cell nuclear antigen (PCNA) were studied.

RESULTS

One hundred and thirty-eight postmenopausal women were enrolled in this study. Among which, 97 women had their endometrium being adequately obtained; the most frequent type of histopathology was normal endometrium (91.8%). Endometrial hyperplasia was found in seven patients (7.2%), including typical simple hyperplasia (n=1, 1%), focal simple hyperplasia (n=5, 5.2%) and complex hyperplasia without atypia (n=1, 1%). The proliferative fractions (PF; S plus G2-M phase) of cells from normal and hyperplastic endometrium of menopausal women after HRT were 8.18 and 8.95%, respectively, which were lower than those from 29 premenopausal women without HRT. The level of PCNA of normal and hyperplastic endometrium in postmenopausal women after HRT was about 80 and 84%, respectively, of that from premenopausal endometrium.

CONCLUSIONS

Our study showed the PF of the cell cycle and the level of PCNA were not increased in the menopausal endometrium under HRT as compared to the premenopausal controls.

Endocrine changes of the perimenopause

Reproductive aging in women is closely tied to the loss of ovarian follicles through atresia. The sentinel endocrinologic finding is the monotropic FSH rise, associated with a decline in ovarian inhibin B secretion. Fertility becomes significantly compromised long before overt clinical signs occur, such as cycle irregularity. Compromised fertility is primarily related to oocyte dysfunction. As women with regular cycles near the end of the reproductive years, the following changes are usually manifested: 1) the selection and development of a dominant follicle occurs earlier; 2) there is earlier ovulation; 3) there is a short follicular phase and total cycle length; and 4) ovarian steroid secretion is normal. The relationships, if any, between the monotropic FSH rise, accelerated follicular atresia, shortened follicular phase, and oocyte quality remain to be determined. The next phase of reproductive aging is the perimenopause. Lack of predictability is the rule with regard to the nature and duration of the perimenopause. Long cycles are interspersed with short ones, and intermittent ovulatory cycles are intermingled with periods that are hormonally indistinct from the postmenopausal state. Even after the last menstrual period, evidence of intermittent ovarian estradiol production may still be detected. Although fertility is severely compromised during the perimenopause, ovulation may occur without warning and contraception must be practiced if pregnancy is not desired. Further studies are needed to elucidate the factors contributing to oocyte abnormalities in women of advanced reproductive age, as well as the factors that determine the rate of follicle atresia and the length of the reproductive life span.

Expression of 112-kDa estrogen receptor in mouse brain cortex and its autoregulation with age

The mouse brain cortex expresses ER whose size is larger than uterus and level changes with age and hormonal treatment. Western blot analysis shows the presence of 66 kDa ER in uterus but 112 and 116 kDa ER in the brain. Whereas 116 kDa ER is phosphorylated and predominantly present in nuclei, 112 kDa ER is unphosphorylated and present in both cytosol as well as nuclei. Similar to uterus, the level of ER decreases drastically in the brain cortex of old mice. Hormonal regulation of ER shows age-specific pattern. Ovariectomy reduces the level of ER in adult but increases it significantly in old. While testosterone does not alter the level of ER in either age, estradiol decreases it considerably in old but shows no detectable difference in adult. Our results provide evidence for the expression of a novel form of ER in mouse brain cortex and its regulation by sex steroid hormones in age-specific manner.

Aging of the human endometrium: peri-implantation phase endometrium does not show any age-dependent variation in lectin binding

OBJECTIVE

To evaluate if the peri-implantation endometrium shows age variations in lectin patterns, which suggest possible age variations in embryo-maternal recognition.

STUDY DESIGN

Peri-implantation endometria of younger ( < 30 years of age: n = 13) and older ( > 40 years of age: n = 17) normally menstruating women was studied. Endometrial specimens were routinely fixed in buffered formaline and embedded in paraffin. Sections (5 microns) were studied using seven lectins: DBA (Dolicus biflorus, binding specificity alpha-D-GalNAc), PNA (Arachis hypogea, binding specificity D-Gal (beta 1 --> 3)-D-GalNAc), SBA (Glycine max binding specificity alpha/beta-D-GalNAc > D-Gal), WGA (Triticum vulgare binding specificity (alpha-D-GlcNAc)n and sialic acid), ConA (Canavalia ensiformis binding specificity alpha-D-Man > alpha-D-Glc), LTA (Lotus tetragonolobus binding specificity alpha-L-fucose) and UEA 1 (Ulex europaeus binding specificity alpha-L-fucose).

RESULTS

No significant differences were found in the glycoconjugates sugar residue content and distribution between the endometria of women < 30 years of age and those of women > 40.

CONCLUSIONS

Our results suggest that human endometrium does not age, at least while cyclic hormonal stimulation and menstruation are present.