In Silico, In Vitro, and In Vivo Analysis Identifies Endometrial Circadian Clock Genes in Recurrent Implantation Failure

Endometrial Proliferative Phase-Centered View of Transcriptome Dynamics across the Menstrual Cycle

The endometrium, the inner mucosal lining of the uterus, undergoes complex molecular and cellular changes across the menstrual cycle in preparation for embryo implantation. Transcriptome-wide analyses have mainly been utilized to study endometrial receptivity, the prerequisite for successful implantation, with most studies, so far, comparing the endometrial transcriptomes between (i) secretory and proliferative endometrium or (ii) mid-secretory and early secretory endometrium. In the current study, we provide a complete transcriptome description of the endometrium across the entire menstrual cycle and, for the first time, comprehensively characterize the proliferative phase of the endometrium. Our temporal transcriptome analysis includes five time points including the mid-proliferative, late proliferative (peri-ovulatory phase), early secretory, mid-secretory, and late secretory phases. Thus, we unveil exhaustively the transitions between the consecutive proliferative and secretory phases, highlighting their unique gene expression profiles and possible distinct biological functions. The transcriptome analysis reveals many differentially expressed genes (DEGs) across the menstrual cycle, most of which are phase-specific. As an example of coordinated gene activity, the expression profile of histone-encoding genes within the HIST cluster on chromosome 6 shows an increase in cluster activity during the late proliferative and a decline during the mid-secretory phase. Moreover, numerous DEGs are shared among all phases. In conclusion, in the current study, we delineate the endometrial proliferative phase-centered view of transcriptome dynamics across the menstrual cycle. Our data analysis highlights significant transcriptomic and functional changes occurring during the late proliferative phase-an essential transition point from the proliferative phase to the secretory phase. Future studies should explore how the biology of the late proliferative phase endometrium impacts the achievement of mid-secretory endometrial receptivity or contributes to molecular aberrations leading to embryo implantation failure.

Embryo transfers performed during daylight savings time led to reduced live birth rates in older patients

PURPOSE

To study the impact of undergoing an embryo transfer during the week of daylight savings time transition on live birth rates.

METHODS

We performed a retrospective observational cohort study of patients undergoing embryo transfer at an academic infertility practice during the week of spring or fall daylight savings time transition (cases), or the 2 weeks preceding and following the daylight savings transition (controls) between 2015 and 2021. The primary exposure was completion of an embryo transfer during the week of daylight savings time transition. The primary outcome was a comparison of live birth rate per embryo transfer among individuals undergoing an embryo transfer during the week of daylight savings time (DST) transition and those who did not.

RESULTS

A total of 309 embryo transfers occurred during the week of daylight savings transition and 1242 embryo transfers occurred in the control group outside of the daylight savings transition week. The live birth rate after embryo transfer during DST transition weeks was 39.2% (121/309) compared to 40.8% (507/1242) (p = 0.59). When restricting the analysis to individuals (age > 37 years), the live birth rate after embryo transfer during DST transition week was 23.5% (24/102) compared to 34.8% (149/429) (p = 0.03). This difference persisted in the mixed-effects regression model demonstrating that after adjusting for relevant covariates, embryo transfer during DST transition weeks resulted in a 45% decrease in the odds of achieving a live birth.

CONCLUSION

Daylight savings time transition may be associated with less favorable outcomes after embryo transfer among an older infertile patient population. Future work is needed to prospectively examine the influence of circadian rhythm disruption on reproductive outcomes.

Time-restricted feeding ameliorates uterine epithelial estrogen receptor α transcriptional activity at the time of embryo implantation in mice fed a high-fat diet

BACKGROUND

More than 30% of reproductive-age women are obese or overweight. Obesity and exposure to a high-fat diet (HFD) detrimentally affect endometrial development and embryo implantation. We previously reported that time-restricted feeding (TRF) improved ovarian follicular development, but whether and how TRF modulates embryo implantation are poorly understood.

OBJECTIVE

We investigated the effect of TRF on embryo implantation.

METHODS

In TRF group, mice had 10 hours of food free access from 9 pm to 7 am, and fed a normal diet or a HFD. Tail vein injection of Chicago blue dye was used to examine embryo implantation sites at day 5.5 (D5.5) of pregnancy. Serum collected at D0.5 and D4.5 of pregnancy was used to examine the level of estradiol (E2) and progesterone. Uterine estrogen receptor (ER) and progesterone receptor levels and their targeted aquaporins (AQPs) were measured. LC-MS was used to analyze bile acid (BA) composition, and primary hepatocytes were used to test the effects of BA on the expression level of SULT1E1, a key enzyme in estrogen inactivation and elimination.

RESULTS

We found that TRF prevented HFD-induced embryo loss and alleviated the defect in luminal closure on D4.5 of pregnancy. The cyclic changes of E2 level were lost in mice fed ad libitum but not in TRF mice on the HFD. The HFD increased ERα expression and transcriptional activity, which induced AQP3 and AQP5 expression on D4.5 of pregnancy. TRF prevented the negative effect of the HFD on uterine luminal closure. Furthermore, in vitro and in vivo results showed that BA suppressed estrogen degradation by activating liver SULT1E1 expression.

CONCLUSIONS

Our findings demonstrated that TRF prevented HFD-induced defects in luminal closure, thereby improving embryonic implantation, and provide novel insights into the effects of dietary intervention on obesity and associated infertility.

Hsa_circ_0001550 impairs decidualization by regulating the proliferation and apoptosis of endometrial stromal cells

RESEARCH QUESTION

What is the molecular function of hsa_circ_0001550 in decidualization?

DESIGN

Human endometrial stromal cells (HESC) were isolated from the endometrium tissues to build an in-vitro decidualization model. Different concentrations of medroxyprogesterone acetate (MPA) were used to observe whether the expression level of hsa_circ_0001550 was related to progesterone. Biological characteristics and distribution of hsa_circ_0001550 were determined by RNase R, actinomycin D (Act D) assay and cytoplasmic/nuclear fraction assay. Then the overexpression of hsa_circ_0001550 was achieved by adenovirus vector. Cell proliferation was determined by Cell Counting Kit-8 (CCK-8) assays. The cell cycle was assessed by flow cytometry analyses. Cell apoptosis was determined by annexin-V/propidium iodide double staining experiment and western blotting.

RESULTS

The expression of hsa_circ_0001550 was decreased in decidua and decidualized HESC (P < 0.001, P = 0.014). Hsa_circ_0001550 is a covalently closed RNA molecule that was verified by RNase R assay and Act D assay (P = 0.012). Nuclear and cytoplasmic separation experiments confirmed that hsa_circ_0001550 was mainly distributed in the cytoplasm. Overexpression of hsa_circ_0001550 inhibited decidualization of HESC (P < 0.0001). Furthermore, overexpression of hsa_circ_0001550 inhibited proliferation by decreasing the number of S phase cells (P = 0.033). Annexin-V/propidium iodide double staining experiment and western blotting revealed that overexpression of hsa_circ_0001550 promoted HESC apoptosis (P < 0.001, P = 0.0139).

CONCLUSIONS

Hsa_circ_0001550 impairs decidualization of HESC. Progesterone decreases the expression of hsa_circ_0001550. The results may provide new insights into the cause of decidualization.

Immune alterations in recurrent implantation failure

A failure to achieve pregnancy after three or more embryo transfer cycles with high-quality blastocysts is referred to as recurrent implantation failure (RIF). RIF can be due to altered uterine factors or male factors or embryo factors. Disrupted endometrial receptivity, altered expression of genes in several pathways, immunologic disturbances in the peripheral blood and/or the endometrium, and epigenetic alterations are associated with RIF. Amongst the immunologic disturbances, altered Th1/Th2 ratio, altered NK cell and macrophage numbers are observed in women with RIF. However, not all women with RIF have the same kind of immune dysfunction suggesting that RIF is a heterogeneous condition associated with varied immune responses and one size may not fit all. Thus, personalized therapies based on the immune status of the patient are being tested in women with RIF. In general, women with a high Th1/Th2 ratio are offered Tacrolimus, while intravenous IgG is recommended in women with high NK cell numbers/HLA mismatch. Women with hyperactivated immune status in the uterus are offered progesterone support, prednisolone, vitamin E, and intralipid treatment to suppress inflammation and oxidative stress, while endometrial scratching and intrauterine hCG administration are offered to women with hypo-active immune status. There is a need for standardized tests for evaluation of immune status in patients and sufficiently powered randomized controlled trials for personalized therapies to determine which of these will be beneficial in women with RIF. Till then, the ART community should limit the use of such add-on interventions in women with RIF.