Effect of aging on populations of estrogen receptor-containing cells in the rat uterus

Uterine Aging and Reproduction: Dealing with a Puzzle Biologic Topic

Uterine aging is the process of the senescence of uterine tissue, observed in all middle-aged mammals. Since the aging-related changes in the uterus are associated with infertility and poor pregnancy outcomes, with a lack of studies discussing uterine aging, authors reviewed uterine aging and its consequences on reproduction. MEDLINE, Scopus, and PubMed searches during the years 1990-2023 were performed using a combination of keywords and terms on such topics. According to the author's evaluation, articles were identified, selected, and included in this narrative review. The aging process has an unfavorable impact on the uterus of mammals. There are different and selected molecular pathways related to uterine aging in humans and animals. Uterine aging impairs the function of the uterine myometrium, neurofibers of the human uterus, and human endometrium. These biological pathways modulate oxidative stress, anti-inflammatory response, inflammation, mitochondrial function, DNA damage repair, etc. All these dysregulations have a role in poorer reproductive performance and pregnancy outcomes in older mammals. The most recent data suggest that uterine aging is accompanied by genetic, epigenetic, metabolic, and immunological changes. Uterine aging has a negative impact on the reproductive performance in mammalian species, but it could be potentially modulated by pharmacological agents, such as quercetin and dasatinib.

Effects of post-ovariectomy time frame and age on the antidepressant-like actions of estradiol and prolame in female rats

Estrogen replacement therapy (ERT) is an effective treatment for symptoms associated with climacteric and depression some women experience during perimenopause and menopause. The antidepressant-like effects of ERT may depend on the type of estrogen, age, and time when restitution is initiated after hormonal decline. Prolame is a synthetic steroid with estrogenic and antidepressant-like effects that may produce fewer adverse effects. We hypothesize that such actions of prolame on females depend on age and the duration of hormone deprivation period. We assessed the antidepressant-like effects of 17β-estradiol (E₂) and prolame in young and middle-aged rats across different post-ovariectomy (Ovx) time frames. Independent groups of young adults and middle-aged female rats were tested in the forced swimming test (FST) at 3, 8, 16, and 24 weeks post-Ovx. Prolame and E₂ were administered in a sub-chronic schedule consisting of three injections before the FST. Likewise, the utero-trophic effects of these hormones were analyzed. We found that E₂ and prolame reduced immobility in young rats 3 and 8 weeks after Ovx; in contrast, only prolame produced this effect in middle-aged rats three weeks post-Ovx. E₂ and prolame increased the animals' utero-somatic index at all post-Ovx times, but the action of E₂ and prolame produced a greater response in young adult rats. Our findings showed that the antidepressant-like effects of E₂ and prolame depend on the post-Ovx time frame, age, and estrogen type. Interestingly, our results indicate that, in contrast to E₂, prolame maintained its antidepressant effect in middle-aged rats.

Altered hormonal responsiveness of proliferation and apoptosis during myometrial maturation and the development of uterine leiomyomas in the rat

Uterine leiomyomas are responsive to the ovarian steroids, estrogen and progesterone; however, a mechanistic understanding of the role of these hormones in the development of this common gynecologic lesion remains to be elucidated. We have used the Eker rat uterine leiomyoma model to investigate how ovarian hormones regulate or promote the growth of these tumors. Proliferative and apoptotic rates were quantitated in normal uterine tissues and leiomyomas in response to endogenous ovarian steroids. In 2- to 4-mo-old animals, cell proliferation in the normal uterus corresponded with high serum levels of steroid hormones during the estrous cycle, and apoptosis occurred in the rat uterus in all cell types following sharp, cyclical declines in serum hormone levels. It is interesting that the responsiveness of uterine mesenchymal cells changed between 4 and 6 mo of age, with significant decreases in both proliferative and apoptotic rates observed in myometrial and stromal cells of cycling animals. Leiomyomas displayed much higher levels of proliferation than did age-matched myometrium; however, their apoptotic index was significantly decreased in comparison with normal myometrium. This disregulation between proliferative and apoptotic responses, which were tightly regulated during ovarian cycling in the normal myometrium, may contribute to the disruption of tissue homeostasis and underlie neoplastic growth of these tumors.

The best donor

Oocyte donation has become a common treatment modality for a large spectrum of infertility conditions. The purpose of this study was to assess the success rate of a shared egg donation programme, and to define the profile of a successful 'donor-recipient' couple in view of the limitations imposed by the shared programme. The results of all consecutive cycles of egg donation from 1st January 1995 to 31st December 1996 were analysed. A total of 383 donor cycles were matched with 946 recipient cycles; clinical pregnancy rates were 23. 5 and 16.7% respectively. With the exception of endometriosis, which significantly reduced the pregnancy rate in both groups, similar pregnancy rates were obtained in both groups for all the other infertility aetiologies of the donors. The donor's age had no impact on pregnancy rate of the recipient, but pregnancy rate was significantly decreased in donors >35 years. Recipients >50 years had significantly reduced pregnancy rates and those >45 years a significantly increased abortion rate. Recipients with severe male factor infertility, who had intracytoplasmic sperm injection treatment, showed pregnancy rates equivalent to those recipients who had regular in-vitro fertilization. We conclude that in a shared egg donation programme, the recipients' pregnancy rate and outcome are dependent only on the donors' infertility aetiologies and on recipients' ages.

Correlation between nuclear bodies and estrogen receptors in endometrial epithelial cells of old rats

Nuclear bodies (NB) are prominent round structures in interchromatin regions of interphase nuclei, regarded as markers of stimulated rRNA synthesis. Their frequency was found to be estrogen-dependent and correlated with estrogen receptor (ER) content in endometrial epithelial cells of prepubertal and cyclic rats. The present study was designed to simultaneously examine the frequency of simple and complex NB and the status of ER in endometrial epithelia of old rats in relation to age and vaginal cytology. The vaginal cycles of old Wistar rats (n degree = 24) at 24, 28, 32, and 36 months of age, which were longitudinally monitored for at least 180 days by daily vaginal smears, were extremely irregular with a predominance of either persistent estrus or persistent diestrus over many days, weeks and even months. In all age groups ER-immunoexpression was very high (+3 = > 75%) in persistent-estrus rats and coincided with particularly frequent NB (2-3 simple NB out of 4-5 total NB per nuclear profile) in the tall epithelial cells with ultrastructural signs of intense protein synthesis. In persistent-diestrus rats isolated simple and complex NB (1 per nuclear profile) and an almost absent ER expression were distinctive of the nuclei in low, ultrastructurally "inactive" endometrial luminal and glandular epithelial cells. Thus, ER immunoexpression and NB frequency are also estrogen-dependent in old rats. Our findings show, for the first time, that ER immunoexpression in endometrial epithelial cells is down-regulated only in old rats in persistent diestrus, whereas in persistent-estrus rats intense ER expression harmonizes with high NB frequency, irrespective of animal age.

Parameters that influence the results of in vitro fertilization/embryo transfer: a study of an egg donation model

A retrospective analysis was carried out after ovulation induction in donors, and treatment outcome in donors and recipients, relating to variables such as: age, protocol of ovarian stimulation, transfer of fresh or cryopreserved embryos, number of embryos transferred including quality and etiology of donor and recipient infertility. The recipients underwent 214 cycles of embryo transfer from 82 different donors. Forty-five (21%) pregnancies were recorded. The age of the recipients significantly affected the conception rate (pregnancy rate of 30% in those aged < 30 years, compared to 9.7% in those aged > 44 years) and the donors were contributed more to pregnancies were also younger. The pregnancy rate was significantly higher when fresh embryos were transferred to recipients (28%, compared to 15% when cryopreserved embryos were transferred). In addition, the number of embryos transferred affected the pregnancy rate if > or = 3 embryos were transferred and, if they were of good quality, the success was significantly higher. Ultimately, when the ovarian stimulation protocol was clomiphene citrate and human menopausal gonadotropin or gonadotropin-releasing hormone agonist/follicle-stimulating hormone/human menopausal gonadotropin, and the etiology of infertility was polycystic ovarian disease in the donors, the success rate was significantly increased in the recipients.

Endometrial preparation: lessons from oocyte donation

OBJECTIVE

To gain insight into the physiology of human endometrial development after artificial preparation with estrogen (E) and P, before oocyte donation.

DESIGN

Review and analysis of relevant studies published in the last decade, identified through the literature and Medline searches.

RESULTS

Oocyte donation represents a unique in vivo experimental model in the human that permits the study of endometrial development under controlled variable conditions. Early studies have shown that adequate endometrial preparation can be achieved by sequential E and P only. The successful implementation of the simplified approach to oocyte donation demonstrated that satisfactory endometrial receptivity is not dependent on incremental administration of E and P and similarly can be achieved by fixed dosages of these steroids. Moreover, numerous clinical oocyte donation studies have shown that both physiologic and supraphysiologic levels of E and P have resulted in good endometrial development and pregnancy rates, underlining the relative insensitivity of the endometrium to extreme hormonal conditions. In addition, it has been clarified that the endometrium is tolerant of some manipulations during the follicular phase. Contrary to morphological studies that demonstrated preservation of endometrial preparation after luteal E depletion, preliminary evidence suggests that the functional capacity of the endometrium could be affected adversely.

CONCLUSION

In contrast to early oocyte donation studies, which indicated a correlation between morphologic integrity and functional capacity of the endometrium, some evidence presented in this review demonstrates that adequate endometrial morphology does not always imply normal endometrial receptivity.

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.

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

OBJECTIVE

To evaluate if human endometrium presents morphological variations suggestive of an age-related decline in endometrial receptivity.

STUDY DESIGN

Peri-implantation endometrium 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 formalin and embedded in paraffin. Sections (5 mu m) were stained with hematoxylin-eosin, periodic acid-Schiff (PAS) and Trichrome conforming to Masson according to conventional histologic examination. Several consecutive sections were used for the following immunohistochemical study: vascular localization (CD34), cellular proliferation index (PCNA), progesterone and estrogen receptors.

RESULTS

Using both the traditional morphological evaluation and monoclonal antibodies, no significant differences were found 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.

Sterility in neonatally androgenized female rats and the decidual cell reaction

In female rats, administration of androgen during early postnatal life results in anovulatory sterility characterized by polyfollicular ovaries and persistent vaginal cornification in adulthood. In these androgen-sterilized rats, the acyclic male pattern of gonadotropin secretion results from permanent damage to hypothalamic centers normally responsive to steroid feedback. The capacity of the endometrium to differentiate into deciduoma in response to endometrial stimulation is markedly reduced in the uterus of the androgenized rats receiving an appropriate regimen of progesterone and estrogen injections. The hypothesis is presented that the lowered uterine responsiveness in the androgenized rats is largely ascribable to the effect of androgen given neonatally rather than to the influence of continued exposure to ovarian estrogen. This review deals with the nature of the uterine response to ovarian hormones and the deciduogenic stimulus in androgenized rats in order to verify the mechanism involved in androgen action on the neonatal uterus.

In vitro fertilization and oocyte donation in women 45 years of age and older

OBJECTIVE

To assess the reproductive potential in women > or = 45 years of age.

DESIGN

Retrospective analysis.

SETTING

In vitro fertilization-embryo transfer unit, standard IVF and oocyte donation programs.

PATIENTS

One hundred twenty-seven patients > or = 45 years old who applied for treatment of infertility.

INTERVENTION

Thirty-one patients underwent 52 treatment cycles in standard IVF. Ninety-six patients underwent 220 oocyte donation cycles.

RESULTS

Of the 52 standard IVF cycles, oocytes were retrieved successfully in only 32. Of these, fertilization and ET were performed in 21 cycles. None of these treatment cycles resulted in a clinical pregnancy. Of the 220 oocyte donation cycles, fertilization and ET were accomplished in 189 cycles. These resulted in 33 (17.5% per transfer) clinical pregnancies.

CONCLUSIONS

These results suggest that oocyte donation may extend the reproductive potential in women > or = 45 years old when little hope is offered by standard IVF.

Endometrial receptivity in the light of modern assisted reproductive technologies

OBJECTIVE

To review the different aspects of endometrial receptivity as it is reflected in the various modalities of modern assisted reproductive technologies.

DESIGN

The importance of endometrial receptivity and the factors that affect it such as the type of treatment, age, and ovarian function are discussed in this review. Novel approaches to determine receptivity such as Doppler ultrasonography and molecular biology are considered; assisted hatching is also discussed.

CONCLUSIONS

Endometrial receptivity cannot, as yet, be directly assessed. Circumstantial evidence suggests that receptivity declines with age, is adversely affected by controlled ovarian hyperstimulation, and is possibly affected by ovarian function. Future studies will have to focus on molecular cell biology and physiology of the endometrium.

Endometrial receptivity: the age-related decline in pregnancy rates and the effect of ovarian function

OBJECTIVE

To assess the effect of age and ovarian function on endometrial receptivity.

DESIGN

Retrospective comparison between standard IVF and ovum donation in younger and older patients (< 40 and > or = 40 years of age, respectively).

PATIENTS

In standard IVF, there were 325 transfer cycles in older patients and 1,103 transfer cycles in younger ones. In ovum donation, there were 236 transfer cycles in older patients and 222 cycles in younger women. Ovum recipients were then redivided into two groups, according to ovarian function: ovarian failure group (219 cycles) and eugonadal group (239 cycles) in patients with retained ovarian function as manifested by regular menstrual cycles and normal gonadotropins.

RESULTS

In standard IVF, clinical pregnancy rates (PRs) were significantly lower in older patients (12.9% versus 23.8%, respectively). In ovum donation, clinical PRs were also significantly lower in older patients (21.2% versus 29.3%, respectively). A significantly higher clinical PR (31.1%) was noted in patients with ovarian failure, compared with both eugonadal patients undergoing ovum donation (19.7%) and standard IVF patients (21.3%).

CONCLUSIONS

The decrease in endometrial receptivity with age is responsible for the higher rate of implantation failure in older women. Patients with nonfunctioning ovaries do better than eugonadal patients in ovum donation programs.

Characteristics of uterine aging

Uterine aging is in part responsible for a decline in fecundity which begins in middle age in most mammals. Characteristics of uteri from a variety of animals in middle age and old age are reviewed and the factors which may be responsible for this decline discussed. These include age-related changes in the hypothalamus, pituitary, and ovaries; loss of number or function of steroid hormone receptors; morphological changes in the uterine epithelium; the accumulation of collagen fibrils in the uterine stroma; and loss or impairment of the decidual response. The ultrastructural morphology of uterine epithelial, stromal, and decidual tissue from 4 month old and 18 month old Fischer 344 rats is presented and compared.

Female reproductive aging--ovarian and uterine factors

OBJECTIVES

To review published data on ovarian and uterine aging in the human female.

DATA IDENTIFICATION

Literature review.

STUDY SELECTION

Studies examining the effect of age on oocyte quality and uterine receptivity.

RESULTS

There is clear evidence in women having in vitro fertilization (IVF) and in normal oocyte donors that oocyte quality declines with age. Three studies of oocyte donation, one study of IVF, and multiple studies in subhuman mammalian species have all shown reduced implantation with aging, and endometrial biopsies in women over age 35 having IVF have shown a high incidence of delayed or absent secretory maturation. In one study of oocyte donation, the reduced rate of pregnancy in women over age 40 was corrected by doubling the dose of progesterone (P) administered to prepare the endometrium for implantation.

CONCLUSIONS

Conflicting opinions regarding the effect of aging on uterine receptivity in recipients of donated oocytes appear to have been because of use of high doses of P replacement. When doses more closely approximating physiological levels have been used, a decline of implantation with increasing age has been clearly demonstrated. Oocyte donation, through the use of oocytes from young normal women and an increased level of P replacement to aging recipients, corrects both of these defects.

Aging of endometrium and oocytes: observations on conception and abortion rates in an egg donation model

OBJECTIVE

To assess the comparative contribution of endometrial and oocytic aging to the decline in fertility with age.

DESIGN

Retrospective analysis of conception and abortion rates in an egg donation program, with respect to donor and recipient ages.

PATIENTS

All oocyte recipients had ovarian failure. Donors were women undergoing in vitro fertilization who contributed up to a third of retrieved oocytes.

INTERVENTIONS

None.

RESULTS

Thirty pregnancies (28 intrauterine) were recorded in 169 reception cycles originating from 91 donation cycles. Women who conceived were younger than those who did not (median age 31 versus 37; P less than 0.046), with no difference in age of donors. There was a significant difference in spontaneous abortion rate by age of donor rather than by age of recipient. Donors to successful pregnancies were younger than donors to aborted pregnancies (median age 27.5 versus 33; P less than 0.0211), but the 11 women with aborted pregnancies did not differ in age from the 17 women with successful pregnancies.

CONCLUSIONS

In women, endometrial function as expressed by conception rate in the recipients declines with age, whereas it is oocyte age that primarily influences risk of abortion.

Homoeostatic imbalance during cellular ageing: altered responsiveness

The inability of normal cells to maintain themselves for ever is a reflection of homoeostatic imbalance and a progressive failure of maintenance. Ageing cells respond less to growth stimulants whereas they show increased sensitivity to toxic agents including antibiotics, phorbol esters, radiation and other physical stresses. No major quantitative and qualitative defects in the receptor systems have been detected that could explain the reasons for altered responsiveness during ageing. Random metabolic defects in the processes involved in maintaining homoeostasis may be critical for causing homoeostatic imbalance, cellular ageing and death.

Differential effects of aging on estrogen receptor dynamics in hypothalamus, pituitary and uterus of the C57BL/6J mouse

Estrogen receptor (ER) dynamics and content were measured in the hypothalamus (HYPO), pituitary (PIT) and uterus (UT) of aging mice because of their potential importance to age-related changes in sensitivity to estrogen. Young (3-6 months), and old (22-24 months) C57BL/6J mice were injected with a dose of E2 (0.05 micrograms/10 g body wt) sufficient to achieve maximal levels of nuclear ER (ERn) in all tissues, and the rise and fall of ERn and the depletion and replenishment of cytosolic ER (ERc) were measured 0, 1, 2, 4, 8, 12 and 24 h later. Integrated areas under the ERn profiles in old HYPO, PIT and UT were reduced 34, 28 and 19%, respectively. These reductions were due to (1) lower levels of ERn throughout the profiles, (2) delays in attainment of peak ERn in UT and PIT, and (3) accelerated loss of peak ERn in HYPO. ERc levels were also reduced in old mice, and replenishment of ERc was delayed in old HYPO and PIT, but not in UT. Reductions in total ER (ERn + ERc) were sufficient to account for all reductions and altered dynamics of ERn, except for the delayed attainment of peak ERn in UT. These results indicate that levels and dynamics of nuclear ER are altered during aging, and that most of these changes are secondary to alterations in ER content and turnover rather than a reduced ability of ER to bind to nuclear sites.