P–563 Assessing ovarian age: Could we use leukocyte telomere length as a surrogate marker of cumulus cells telomere content?

Study question

Is leukocyte telomere length (LTL) correlated with cumulus cells telomere length (CCTL) in an age-heterogeneous women population?

Summary answer

LTL showed a positive correlation with CCTL in the studied population. Hence, its potential value as indicator of ovarian age would deserve further evaluation.

What is known already

Progressive telomere shortening has been related to ovarian aging and genomic instability during early development. A positive correlation between short telomere length of the first polar body and aneuploidy rate has been reported. CCTL has shown to be a biomarker of oocyte and embryo quality, but its assessment is impractical. LTL has been proposed as a surrogate of TL of follicular cells, but telomere lengthening through folliculogenesis could be controlled by different mechanisms. Thus, we aimed to determine if LTL in an age-heterogeneous population is correlated with CCTL and therefore considered an accurate surrogate for telomere length in the ovary.

Study design, size, duration

In this prospective non-interventional cohort study, 35 egg donors and 17 women undergoing Preimplantation Genetic Testing for Aneuploidy (PGT-A) treatment were included during sixteen months. Following controlled ovarian stimulation determined by treating physicians, oocyte retrieval was performed 36 hours after final maturation induction. Cumulus cells (CC) for telomere length (TL) measurement were obtained after the pick-up and oocyte stripping. A blood sample was collected through peripheral venous access for LTL measurement.

Participants/materials, setting, methods

Genomic DNA of CC and leukocytes from the 52 subjects was isolated. Average delta cycle threshold (ΔCt) was determined using a SYBR green quantitative real-time PCR protocol for relative TL. For normalization of measurements, a Taqman assay for the multicopy gene Alu was performed. ΔCtL and ΔCtCC were compared by a paired t-test analysis and the fold change was calculated. Additionally, the association between them and patient age was analyzed by a Pearson correlation test.

Main results and the role of chance

Mean participant’s age was 29.94 ± 7.55 years and mean values for ΔCtL and ΔCtCC were 7.99 ± 0.53 and 7.46 ± 0.75, respectively. A positive significant correlation was found between age and ΔCt (ΔCtL: R2=0.71, p-value=5.18e–09; ΔCtCC: R2=0.47, p-value=0.00049). Since ΔCt values are inversely proportional to the amount of nucleic acids amplified and, therefore, to the telomere length, this correlation means that TL in both cell types decreases as women age. Additionally, ΔCtL was significantly higher than ΔCtCC (ΔCt fold change: 0.93, p-value=9e–07), meaning that CC showed significantly longer telomeres than leukocytes, thus supporting our previous published results in young egg donors. When analyzing the ΔCtL and ΔCtCC in these age-heterogeneous sample, a positive moderate and significant correlation was observed (R2=0.42, p-value=0.002). Thus, LTL could be suggested as a potential indicator of CCTL and therefore as a candidate for a biological marker of ovarian aging.

Limitations, reasons for caution

The sample size of this study was moderate and perhaps increasing the number of subjects might give additional strength to our findings. In addition, although relative telomere length allowed for adequate comparison between subjects, this method did not allow for absolute TL measurement.

Wider implications of the findings: While reproductive implications of LTL measurement need to be further studied, our results support the potential usefulness of LTL measurement as an indicator of CCTL and ovarian aging when analyzing an age-heterogeneous population. Further, our findings suggest that CC could possess different mechanisms to cope against telomere length shortening.

Trial registration number

Not applicable

Varying levels of serum estradiol do not alter the timing of the early endometrial secretory transformation

STUDY QUESTION

Do supraphysiologic estradiol (E2) levels in the ranges attained during normal and high response superovulation cycles modify the onset of endometrial secretory transformation?

SUMMARY ANSWER

Highly supraphysiologic levels of E2 do not alter the ability of physiologic levels of progesterone (P4) to induce secretory transformation.

WHAT IS KNOWN ALREADY

Previous studies have demonstrated that premature P4 elevations during IVF cycles are associated with a decrement in clinical pregnancy rates after fresh embryo transfer due to shifts in the window of implantation (WOI). However, alterations in the onset of secretory transformation may not apply uniformly to all patients. High responders with supraphysiologic E2 levels accompanied by similar subtle increases in P4 have not been shown to have decreased sustained implantation rates. This prospective investigation in which whole-genome transcriptomic and methylomic analysis of the endometrium is performed for individual patients under a range of E2 concentrations brings clarity to a long-debated issue.

STUDY DESIGN, SIZE, DURATION

A randomized, prospective and paired trial was conducted in which 10 participants were enrolled and randomized to the order in which they completed three distinct uterine stimulation cycles, each at a specific E2 concentration: physiologic (∼180 pg/ml), moderately supraphysiologic (600-800 pg/ml) or supraphysiologic (2000 pg/ml). Target E2 ranges were selected to mimic those seen in natural, controlled ovarian stimulation and IVF cycles. E2 valerate was administered in order to maintain stable E2 levels for 12 days followed by intramuscular P4 in oil 10 mg/day for two doses, after which an endometrial biopsy was performed. A total of 30 endometrial biopsies were included in a whole-genome transcriptomic and methylomic analysis.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Healthy volunteers without a history of infertility were included in this study at a single large infertility center. DNA was isolated from the endometrial biopsy specimens and bisulfite sequencing was performed to construct a methylation array. Differential methylation analysis was conducted based on differences in M-values of individuals across treatment groups for each probe as well as carrying out t-tests. RNA was isolated for RNA-Seq analysis and gene expression values were compared using DESeq2. All analyses were performed in a pairwise fashion to compare among the three stimulation cycles within individuals and secondarily to compare all participants in each of the cycles.

MAIN RESULTS AND THE ROLE OF CHANCE

The mean peak E2 and P4 levels were 275 pg/ml and 4.17 ng/ml in the physiologic group, 910 pg/ml and 2.69 ng/ml in the moderate group was, and 2043 pg/ml and 2.64 ng/ml in the supraphysiologic group, respectively. Principal component analysis of 834 913 CpG sites was performed on M-values of individuals within the low, moderate and supraphysiologic conditions in a paired approach. There were no differences in genome-wide methylation within participants across E2 groups. A paired analysis revealed that gene expression profiles did not differ within the same individual at each of the three E2 levels. No significant alterations in gene expression as related to endometrial physiology were identified between the low, moderate and supraphysiologic groups in an inter-participant analysis.

LIMITATIONS, REASONS FOR CAUTION

Although each participant completed a physiologic cycle in which E2 levels were maintained in a range that would simulate a natural cycle, our findings are limited by lack of an unmedicated control to assess if there was a potential effect from E2V. Additionally, our results were obtained in fertile individuals, who may have a different endometrial response compared to an infertile population. Despite the whole genomic endometrial assessment and rigorous, paired study design, the sample size was limited.

WIDER IMPLICATIONS OF THE FINDINGS

Given that the endometrial response to P4 is unaffected by E2 levels in the supraphysiologic range, diminutions in implantation seen in stimulated cycles may result from embryonic-endometrial dyssynchrony following early P4 elevations or slowly blastulating embryos, which occur independently of the magnitude of the E2 rise.

STUDY FUNDING/COMPETING INTEREST(S)

This study was funded by the Foundation for Embryonic Competence, Basking Ridge, NJ, USA. Dr E.S. reports consultancy work for The Foundation for Embryonic Competence, Basking Ridge, NJ, USA. The other authors declare no conflict of interests related to this topic.

TRIAL REGISTRATION NUMBER

NCT02458404.

Free vitamin D does not vary through the follicular phase of the menstrual cycle

The importance of vitamin D (25OHD) in general health and reproductive success has been a focus in the setting of the 25OHD deficiency epidemic. However, there are challenges to understanding 25OHD's effects. The free and bioavailable levels are affected by 25OHD binding protein (DBP) and it is not known how estradiol fluctuations during the menstrual cycle affect these binding parameters. This may impact the most appropriate time to measure 25OHD when determining deficiency. This study characterizes 25OHD throughout the follicular phase of the menstrual cycle. Patients undergoing natural cycle IVF were included. Serum was drawn throughout the follicular phase of the menstrual cycle; 25OHD, DBP, albumin, and estrogen levels were determined for each time point allowing for mathematical calculation of free and bioavailable 25OHD. Early, mid, and late follicular phases were designated by estrogen tertiles among patients. Mean Levels of 25OHD (total, free, bioavailable) and DBP for each tertile were compared with Kruskil-Wallis test for non-parametric groups. Linear regression with GEE was employed due to repeated measures within participants. A total of 33 patients were included with 202 total serum measurements. There was no difference in mean levels of 25OHD (p = 0.77), free 25OHD (p = 0.91), and bioavailable 25OHD (p = 0.76) when measured throughout the follicular phase of the menstrual cycle. Vitamin D metabolism does not fluctuate as estradiol changes in the follicular phase of the menstrual cycle. This data indicates that assessment of 25OHD, in particular when assessed for associations with reproductive outcomes, can be measured reliably at any point during the follicular phase of the menstrual cycle.

Endometrial microbiome at the time of embryo transfer: next-generation sequencing of the 16S ribosomal subunit

PURPOSE

Characterization of the human microbiome has become more precise with the application of powerful molecular tools utilizing the unique 16S ribosomal subunit's hypervariable regions to greatly increase sensitivity. The microbiome of the lower genital tract can prognosticate obstetrical outcome while the upper reproductive tract remains poorly characterized. Here, the endometrial microbiome at the time of single embryo transfer (SET) is characterized by reproductive outcome.

METHODS

Consecutive patients undergoing euploid, SET was included in the analysis. After embryo transfer, performed as per routine, the most distal 5-mm portion of the transfer catheter was sterilely placed in a DNA free PCR tube. Next-generation sequencing of the bacteria specific 16S ribosome gene was performed, allowing genus and species calls for microorganisms.

RESULTS

Taxonomy assignments were made on 35 samples from 33 patients and 2 Escherichia coli controls. Of the 33 patients, 18 had ongoing pregnancies and 15 did not. There were a total of 278 different genus calls present across patient samples. The microbiome at time of transfer for those patients with ongoing pregnancy vs. those without ongoing pregnancy was characterized by top genera by sum fraction. Lactobacillus was the top species call for both outcomes.

CONCLUSIONS

The data presented here show the microbiome at the time of embryo transfer can successfully be characterized without altering standard clinical practice. This novel approach, both in specimen collection and analysis, is the first step toward the goal of determining physiologic from pathophysiologic microbiota. Further studies will help delineate if differences in the microbiome at the time of embryo transfer have a reliable impact on pregnancy outcome.