Female aging and superovulation induction for IVF

Single-cell RNA-seq analysis and cell-cluster deconvolution of the human preovulatory follicular fluid cells provide insights into the pathophysiology of ovarian hyporesponse

Reduction in responsiveness to gonadotropins or hyporesponsiveness may lead to the failure of in vitro fertilization (IVF), due to a low number of retrieved oocytes. The ovarian sensitivity index (OSI) is used to reflect the ovarian responsiveness to gonadotropin stimulation before IVF. Although introduced to clinical practice already years ago, its usefulness to predict clinical outcomes requires further research. Nevertheless, pathophysiological mechanisms of ovarian hyporesponse, along with advanced maternal age and in younger women, have not been fully elucidated. Follicles consist of multiple cell types responsible for a repertoire of biological processes including responding to pituitary gonadotropins necessary for follicle growth and oocyte maturation as well as ovulation. Encouraging evidence suggests that hyporesponse could be influenced by many contributing factors, therefore, investigating the variability of ovarian follicular cell types and their gene expression in hyporesponders is highly informative for increasing their prognosis for IVF live birth. Due to advancements in single-cell analysis technologies, the role of somatic cell populations in the development of infertility of ovarian etiology can be clarified. Here, somatic cells were collected from the fluid of preovulatory ovarian follicles of patients undergoing IVF, and RNA-seq was performed to study the associations between OSI and gene expression. We identified 12 molecular pathways differentially regulated between hypo- and normoresponder patient groups (FDR<0.05) from which extracellular matrix organization, post-translational protein phosphorylation, and regulation of Insulin-like Growth Factor (IGF) transport and uptake by IGF Binding Proteins were regulated age-independently. We then generated single-cell RNA-seq data from matching follicles revealing 14 distinct cell clusters. Using cell cluster-specific deconvolution from the bulk RNA-seq data of 18 IVF patients we integrated the datasets as a novel approach and discovered that the abundance of three cell clusters significantly varied between hypo- and normoresponder groups suggesting their role in contributing to the deviations from normal ovarian response to gonadotropin stimulation. Our work uncovers new information regarding the differences in the follicular gene expression between hypo- and normoresponders. In addition, the current study fills the gap in understanding the inter-patient variability of cell types in human preovulatory follicles, as revealed by single-cell analysis of follicular fluid cells.

Multi-marker assessment of ovarian reserve predicts oocyte yield after ovulation induction

BACKGROUND

Many hormone and ultrasound measurements have been assessed as possible markers of ovarian reserve and to identify potential poor responders to ovulation induction. The objective of this study is to determine whether multiple biomarkers measured in blood samples collected immediately before commencement of ovulation induction for IVF can predict the outcome of ovarian stimulation.

METHODS

We conducted a prospective observational study, including 356 unselected women undergoing ovulation induction/IVF at two centers. Anti-Müllerian hormone (AMH), inhibin B and FSH were measured before commencement of ovulation induction. The main outcome measures were the number of oocytes retrieved and pregnancy outcome.

RESULTS

Univariate analyses showed that age, FSH, inhibin B and AMH were significant predictors for poor oocyte yield. AMH presented the highest receiver operating characteristic area under the curve (ROC(AUC)) of 0.827 indicating a good discriminating potential for predicting poor ovarian response, followed by FSH with an ROC(AUC) of 0.721. In the multivariate analysis, the variables age, FSH and AMH remained significant and the resulting model provided a high ROC(AUC) of 0.819. Women with an ovarian reserve test of <0.3 have more than a 75% chance of having their treatment cycle canceled, but a value over 0.73 indicates a 38% chance of pregnancy. Number of oocytes and oocyte yield per unit FSH administered were correlated with log model for no pregnancy (r = -0.217, P < 0.001 and r = -0.367, P < 0.001, respectively) but had limited predictive value.

CONCLUSIONS

A derived estimate of ovarian reserve demonstrated superior ability for predicting oocyte yield after ovulation induction when compared with any single endocrine marker (AMH, inhibin B, FSH).

Effects of age on follicle and hormone dynamics during the oestrous cycle in mares

The effects of age (young: 5–6 years; intermediate: 10–14 years; old: ≥18 years) on follicle and hormone dynamics during an interovulatory interval (IOI; n = 46) and on preovulatory oocytes and concentrations of follicular fluid factors (n = 44) were studied in mares. Old mares were not approaching senescence, as indicated by regular lengths of the IOI (19–27 days) during the period May–October. The IOI was 1 day longer (P < 0.05) in the old group than in the two younger groups and was associated with a slower (P < 0.05) growth rate of the ovulatory follicle. The old group had diminished follicle activity, as indicated by significantly smaller and fewer follicles. Concentrations of FSH did not differ among age groups, except that the maximum concentration was greater (P < 0.05) in the old group. Concentrations of LH were greater (age × day interaction; P < 0.03) in the young group throughout the ovulatory LH surge and may have played a role in a shorter (P < 0.05) interval from maximum diameter of the preovulatory follicle to ovulation. Maximum circulating concentrations of oestradiol during the preovulatory surge were greatest (P < 0.05) in the young group. No effects of age were detected on oocyte morphology. Concentrations of ovarian steroids in preovulatory follicular fluid were not affected by the age of the mares, but concentrations of free insulin-like growth factor-1 were greater (P < 0.05) in the old group. The results indicate the importance of considering the potential confounding effects of age in experimental protocols and for considering age in the development of theriogenology programmes.

Superovulatory response in a bovine model of reproductive aging

Two experiments were done to test the hypotheses that aging in cattle is associated with a reduced number of follicles recruited into an ovarian follicular wave, and a reduction in the ovarian response to gonadotropin treatment. Older cows (13-16 years of age) and their daughters (3-6 years of age) were treated with FSH for ovarian superstimulation four times over two consecutive years (31 and 33 superstimulations in old and young cows, respectively, experiments and years combined). In Experiment 1, ovulation was induced using LH. In Experiment 2, cumulus-oocyte complexes were collected by ultrasonographic-guided follicle aspirations before expected ovulations. The ovarian follicular and ovulatory responses were monitored daily by ultrasonography. Fewer 2-5mm follicles (P<0.01) were detected at the expected time of follicular wave emergence in older cows than in their daughters. After superstimulation, older cows had fewer follicles >or=6mm (P<0.01), and tended (P=0.1) to have fewer ovulations than their daughters (32+/-4 versus 40+/-3, respectively). There was a positive correlation in the response of individual cows to successive superstimulatory treatments (r>0.8; P<0.0001) and the number of detected ovulations from one year to the next (r=0.6; P=0.04). In conclusion, aging was associated with fewer 2-5mm follicles at follicular wave emergence and a lesser follicular and ovulatory response after superstimulatory treatment. The follicular and ovulatory response after superstimulation was repeatable within individuals, regardless of age.

Bovine model of reproductive aging: Response to ovarian synchronization and superstimulation

The responsiveness of the hypothalamo-pituitary axis to steroid treatments for ovarian synchronization and the ovarian superstimulatory response to exogenous FSH was compared in 13-14 year old cows and their 1-4 year old young daughters. We tested the hypotheses that aging in cattle is associated with: (1) decreased follicular wave synchrony after estradiol and progesterone treatment; (2) delayed LH surge and ovulation in response to exogenous preovulatory estradiol treatment; (3) reduced superstimulatory response to exogenous FSH. Higher plasma FSH concentrations (P<0.01), and a tendency (P=0.07) for fewer 4-5 mm follicles at wave emergence were observed in old cows (n=10) than in young cows (n=9). The suppressive effect of estradiol/progesterone treatment on FSH was similar between old and young cows. Although the preovulatory LH surge in response to estradiol treatment was delayed in old than young cows (P=0.01), detected ovulation times were not different. No difference in ovarian superstimulatory response was detected between age groups, but old cows (n=8) tended (P=0.10) to have fewer large follicles (>or=9 mm) 12 h after last FSH treatment than in young cows (n=7). We concluded that pituitary and ovarian responsiveness to estradiol/progesterone synchronization treatment was similar between old and young cows, but aging was associated with a delayed preovulatory LH surge subsequent to estradiol treatment. Old cows tended to have fewer large follicles after superstimulatory treatment than young cows.

Bovine model for the study of reproductive aging in women: follicular, luteal, and endocrine characteristics

At present, there is no well-characterized animal model to study the effects of aging on fertility in women. The objectives of the study were to characterize age-related changes in ovarian and endocrine functions in old cows and to investigate the validity of a bovine model for the study of human reproductive aging. We tested the hypotheses that aging in cattle is associated with 1) elevated concentrations of gonadotropins and reduced concentrations of steroid hormones in systemic circulation and 2) increased recruitment of ovarian follicles during wave emergence. Daily ultrasonography was performed in 13- to 14-yr-old cows (n = 10) and their 1- to 4-yr-old daughters (n = 9) for one interovulatory interval to study ovarian function. Plasma samples were obtained every 12 h for determination of FSH, LH, progesterone, and estradiol concentrations. Circulating FSH concentrations were higher (P = 0.009) during follicular waves in old cows than in their daughters, but the number of 4- to 5-mm follicles recruited into a wave was lower (P = 0.04) in old cows. Plasma LH concentrations did not differ between groups (P = 0.4), but the ovulatory follicle in two-wave cycles was smaller in old cows (P = 0.04). Plasma estradiol concentrations were higher (P = 0.01) in old cows, and luteal phase progesterone tended to be lower (P = 0.1). We conclude that these changes are consistent with those reported for women approaching menopause transition. Therefore, our results validate the use of the bovine model to study reproductive aging in women.

The practical implications of a raised serum FSH and age on the risk of IVF treatment cancellation due to a poor ovarian response

PURPOSE

Chronological age, or biological age as indicated by elevated FSH levels, are related to ovarian reserve. This study addresses the likelihood of cancellation of IVF treatment due to a poor ovarian response utilising both basal serum FSH and woman's age.

METHODS

A prospective cohort of 536 infertile but ovulating women were studied in their first cycle of IVF treatment. Standardised methods of pituitary desensitisation and ovarian stimulation prior to IVF treatment were employed. Treatment cycles cancelled due to a poor ovarian response to gonadotrophins were studied. A series of logistic regression models were used to explore the probabilities of cancellation in relation to age and FSH.

RESULTS

Both age and basal serum FSH levels were independently associated with the risk of treatment cancellation. A low risk of treatment cancellation was observed in women under the age of 35 irrespective of serum FSH, however in older women the risk of treatment cancellation was most likely in women with a high FSH.

CONCLUSIONS

In combination both age and FSH may serve as a valuable indicator of poor ovarian response leading to treatment cancellation. However, among older women FSH has particular importance, while less so in younger women with regular menstrual cycles.