Human endometrial stromal cells inhibit the pro-angiogenic stimulus of hCG in vitro

During embryo implantation, endometrial angiogenesis is regulated by signals originating from the endometrium itself and the developing embryo. It has been suggested that hCG may play a pro-angiogenic role; therefore, we sought to understand its regulatory role in blood vessel formation in human endometrium using in vivo and in vitro models. In the in vivo model, we screened 16 angiogenesis-related transcripts in the endometrium upon intrauterine administration of hCG. Oocyte donors were recruited and during their controlled ovarian stimulation cycle received a single dose of hCG or vehicle on the day of oocyte pick up during a cycle of ovarian stimulation. One hour before obtaining an endometrial sample, women received an intrauterine administration of vehicle or hCG (500, 1500 and 5000 IU). Transcript and protein analysis showed that MMP3 and VEGFA increased, whereas TIMP1 decreased. The in vitro analysis studied the angiogenic potential of conditioned medium (CM) from primary cultures of human endometrial stromal cells (ESC) stimulated with hCG. Using a 2D and 3D in vitro angiogenesis assays, our results indicate that CM from ESC almost completely inhibits the capillary-like structure formation in endothelial cells, overriding the pro-angiogenic effect of hCG; and this inhibition due to secreted factors present in CM specifically reduced the migration potential of endothelial cells. In conclusion, the endometrial stromal milieu seems to modulate the direct pro-angiogenic effects of hCG on endothelial cells during embryo implantation.

Androgens Profile in Blood Serum and Follicular Fluid of Women With Poor Ovarian Response During Controlled Ovarian Stimulation Reveals Differences Amongst POSEIDON Stratification Groups: A Pilot Study

Patients with poor ovarian response (POR) to exogenous gonadotropins stimulation for assisted reproductive technology (ART) have decreased circulating androgens during spontaneous cycles. The Patient-Oriented Strategies Encompassing Individualized Oocyte Number (POSEIDON) is a 4-tier stratification of women with POR to controlled ovarian stimulation (COH) based on age and biomarkers of ovarian reserve has been proposed to maximize the clinical management of this group for ART. The aim of the present study was to characterize the levels of androgens during COH in follicular fluid (FF) and serum in POSEIDON subgroups and compared them with women of normal ovarian response. Sixty nine consecutive patients undergoing ART were included and testosterone, androstenedione, dehydroepiandrosterone sulfate (DHEA-S), estradiol, sex hormone-binding globulin (SHBG), and insulin-like growth factor 1 (IGF-1) were measured in serum and FF collected at the time of oocyte pick-up. The number of retrieved oocytes was registered for each patient for their allocation to the respective POSEIDON subgroup. The control group comprised 19 women and the POSEIDON group 1 (age < 35, normal ovarian reserve biomarkers) n = 14, group 2 (age ≥ 35, normal ovarian reserve biomarkers) n = 8, group 3 (age < 35, poor ovarian reserve biomarkers) n = 6 and group 4 (age ≥ 35, poor ovarian reserve biomarkers) n = 22. Serum levels of total testosterone, androstenedione and DHEA-S were not different in group 1 vs. control but significantly decreased in group 3 vs. control. DHEA-S in FF was also significantly decreased in group 3 vs. control. In addition, serum testosterone was decreased in groups 2 and 4 vs. control; and serum androstenedione and estradiol were reduced in group 4 vs. control. No differences were observed for estradiol, SHBG and IGF-1 in FF. Finally, a high correlation between serum and FF DHEA-S was observed when data from samples of all groups were pooled. Group 1 did not show hypoandrogenemia however group 3 had low levels of all measured androgens in serum and DHEA-S in FF. Such differences might help to better characterize and/or improve the clinical management of women with POR according to their respective POSEIDON stratification.

hCG activates Epac-Erk1/2 signaling regulating Progesterone Receptor expression and function in human endometrial stromal cells

STUDY QUESTION

How does hCG signal in human endometrial stromal cells (ESCs) and what is its role in regulating ESC function?

SUMMARY ANSWER

hCG signaling in ESCs activates the extracellular signal-regulated protein kinases 1 and 2 (Erk1/2) pathway through exchange protein activated by cyclic AMP (cAMP) (Epac) and transiently increases progesterone receptor (PR) transcript and protein expression and its transcriptional function.

WHAT IS KNOWN ALREADY

hCG is one of the earliest embryo-derived secreted signals in the endometrium, which abundantly expresses LH/hCG receptors. hCG signals through cAMP/protein kinase A (PKA) in gonadal cells, but in endometrial epithelial cells, hCG induces Erk1/2 activation independent of the cAMP/PKA pathway. Few data exist concerning the signal transduction pathways triggered by hCG in ESCs and their role in regulation of ESC function.

STUDY DESIGN, SIZE, DURATION

This is an in vitro study comprising patients undergoing benign gynecological surgery (n = 46).

PARTICIPANTS/MATERIALS, SETTING, METHODS

Endometrial samples were collected from normal cycling women during the mid-secretory phase for ESCs isolation. The study conducted in an academic research laboratory within a tertiary-care hospital. The activation of the Erk1/2 signal transduction pathway elicited by hCG was evaluated in ESC. Signaling pathway inhibitors were used to examine the roles of PKA, PI3K, PKC, adenylyl cyclase and Epac on the hCG-stimulated up-regulation of phospho-Erk1/2 (pErk1/2). Erk1/2 phosphorylation was determined by immunoblot. siRNA targeting Epac was used to investigate the molecular mechanisms. To assess the role of Erk1/2 signaling induced by hCG on ESC function, gene expression regulation was examined by immunofluorescence and real-time quantitative PCR. The role of PR on the regulation of transcript levels was studied using progesterone and the PR antagonist RU486. All experiments were conducted using at least three different cell culture preparations in triplicate.

MAIN RESULTS AND THE ROLE OF CHANCE

Addition of hCG to ESCs in vitro induced the phosphorylation of Erk1/2 through cAMP accumulation. Such induction could not be blocked by inhibitors for PKA, PKC and PI3K. Epac inhibition and knockdown with siRNA prevented pErk1/2 induction by hCG. ESCs stimulated with hCG for up to 72 h showed a significant increase in PR mRNA and immunofluorescent label at 48 h only; an effect that was abrogated with the mitogen-activated protein kinase kinase inhibitor UO126. In addition, the hCG-activated Erk1/2 pathway significantly decreased the mRNA levels for secreted frizzled-related protein 4 (SFRP4) at 24 h, whereas it increased those for homeobox A10 (HOXA10) at 48 h (P = 0.041 and P = 0.022 versus control, respectively). Prolactin mRNA levels were not significantly modified. HOXA10 mRNA up-regulation by hCG was not enhanced by co-stimulation with progesterone; however, it was completely abolished in the presence of RU486 (P = 0.036 hCG versus hCG + RU486).

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

This is an in vitro study utilizing stromal cell cultures from human endometrial tissues. Furthermore, results obtained should also be confirmed in vivo in the context of the whole human endometrial tissue and hormonal milieu. The in vitro experiments using hCG have been conducted without other hormones/factors that may also modulate the ESCs response to hCG.

WIDER IMPLICATIONS OF THE FINDINGS

We have determined that hCG induces the PR through the Erk1/2 pathway in ESCs which may render them more sensitive to progesterone, increasing our understanding about the effects of hCG at the embryo-maternal interface. The activation of such a pathway in the context of the hormonal milieu during the window of implantation might contribute to a successful dialog between the embryo and the uterus, leading to appropriate endometrial function. Defective hCG signaling in the endometrial stromal tissue may lead to an incomplete uterine response, compromising embryo implantation and early pregnancy.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the National Fund for Scientific and Technological Development, Government of Chile (FONDECYT) grants 11100443 and 1140614 (A.T.-P.). The authors have no conflicts of interest to declare.

Effect of single post-ovulatory administration of mifepristone (RU486) on transcript profile during the receptive period in human endometrium

Progesterone regulates uterine function during the luteal phase and is essential for the acquisition of endometrial receptivity. The objective of the present study was to identify endometrial transcripts whose expression is altered during the window of implantation after the administration of 200 mg of the antiprogestin mifepristone, 48 h after the LH peak (LH+2, LH+0=LH peak), and to determine the relationship of these transcripts with those regulated during the acquisition of receptivity. Endometrial samples were obtained in LH+7 from seven women of proven fertility, each one contributing with one cycle treated with placebo and another with mifepristone. Additionally, endometrial samples were obtained in LH+2 and LH+7 during a single untreated spontaneous cycle from seven normal fertile women as a reference. DNA microarrays were used to identify transcripts significantly regulated (defined as ≥2.0-fold change with false discovery rate below 1% usingt-test) with the administration of mifepristone vs placebo, or during the transition from pre-receptive to receptive (LH+2 vs LH+7). Approximately 2000 transcripts were significantly regulated in both comparisons (mifepristone vs placebo and LH+2 vs LH+7), but only 777 of them were coincident and displayed opposite regulation except for 25. The mRNA level for eight selected genes regulated by mifepristone was confirmed by real-time RT-PCR. We conclude that not all changes in endometrial transcript levels occurring in the transition from LH+2 to LH+7 seem to be regulated by the progesterone receptor and ∼37% of the genes whose transcript levels changed by effect of mifepristone could be associated with the acquisition of receptivity.

Endometrial gene expression reveals compromised progesterone signaling in women refractory to embryo implantation

BACKGROUND

Endometrial function is essential for embryo implantation. The aim of this study was to analyze gene expression profiles from individual endometrial samples obtained from women with repeated implantation failure after IVF in oocyte donation programs.

METHODS

Seventeen volunteers were recruited: women who had previously participated as recipients in oocyte donation cycles and repeatedly exhibited implantation failure (Group A, study group, n = 5) or had at least one successful cycle (Group B, control group, n = 6) and spontaneously fertile women (Group C, normal fertility group, n = 6). An endometrial cycle was induced with exogenous estradiol (E2) and progesterone (P) and an endometrial sample was collected on the seventh day of P treatment.

RESULTS

Transcriptome analysis showed 82 genes with consistent differential gene expression when comparing A vs. B and A vs. C. One hundred transcripts differentially expressed in group A vs. B have been shown to be regulated by P, suggesting compromised P signaling in the endometrium. The P receptor (PR) mutation PROGINS was not detected in women from group A. Semi-quantitation of immunoreactive PRA/B, PRB and Sp1 (a transcription factor related to P signaling) in paraffin-embedded endometrial sections, did not show statistically significant differences amongst groups. However immunostaining glycodelin was significantly decreased in endometrial samples from group A.

CONCLUSIONS

We conclude that some cases of repeated implantation failure could be associated with an aberrant gene expression profile. Compromised P signaling might be the underlying mechanism for such endometrial gene expression deregulation in women with repeated implantation failure.

Human chorionic gonadotropin (hCG) modulation of TIMP1 secretion by human endometrial stromal cells facilitates extravillous trophoblast invasion in vitro

STUDY QUESTION

Are secreted extracellular matrix (ECM) remodelling elements, relevant to embryo implantation and placentation, modified by hCG in endometrial stromal cells (ESCs)?

SUMMARY ANSWER

hCG decreases tissue inhibitor of metalloproteinase 1 (TIMP-1) secretion in ESCs, thereby facilitating extravillous trophoblast invasion in vitro.

WHAT IS KNOWN ALREADY

Successful embryo implantation and placentation depend on the appropriate invasion of the trophoblast into the maternal endometrial stroma. hCG is one of the earliest embryo-derived secreted signals in the endometrium which abundantly expresses hCG receptors. However, there is little data concerning the effects of hCG on endometrial ECM remodelling with respect to embryo implantation.

PARTICIPANTS/MATERIALS, SETTING, METHODS

This study was conducted in an academic research laboratory within a tertiary-care hospital. Samples were collected from 36 women undergoing benign gynaecological surgery during the mid-secretory phase. ESCs were isolated and stimulated with hCG (10 UI/ml) or vehicle. Conditioned media (CM) were analysed to determine changes in the secreted profile of nine matrix metalloproteinases (MMPs) and three tissue-specific inhibitors of MMPs (TIMPs) using an ELISA array. Data were confirmed by gelatine zymography, western blot and ELISA. The HTR8/SVneo cell line served as a model for trophoblast cells. The invasive potential of trophoblast cells was assessed using Transwell invasion assays under CM or co-culture conditions with ECS and the role of regulated molecules was examined by using immunoprecipitation in CM prior to the assessment of invasive potential.

MAIN RESULTS AND THE ROLE OF CHANCE

MMP-2 levels increased 30%, whereas TIMP-1 levels decreased 20% in CM from ESCs stimulated with hCG (P < 0.05). Gelatine zymography confirmed an increase in MMP-2 activity (P < 0.05). ELISA and western blotting also confirmed the reduction in TIMP-1 upon hCG treatment (P < 0.05). Invasion assays revealed a ∼50% increase in invading HTR8/SVneo cells in chambers with hCG-stimulated ESCs compared with the control (P < 0.05). Immunodepletion of TIMP-1 from control ESC-CM partially resembled the effect of CM from hCG-stimulated ESCs in the trophoblast invasion assays.

LIMITATIONS, REASONS FOR CAUTION

The assays were performed in vitro and ESCs were not decidualized, therefore they reflected the very early stages of embryo implantation or the advanced stages when decidualization fails.

WIDER IMPLICATIONS OF THE FINDINGS

Our data suggest that hCG induces endometrial stromal extracellular remodelling by modulating secreted MMP-2 and TIMP-1. This regulation may be physiologically relevant because it increases the invasive potential of trophoblast-derived cells. At present, few data exist concerning the implications of hCG and endometrial ECM remodelling in embryo implantation. Hence, our results should be confirmed by further in vivo studies.

STUDY FUNDING/COMPETING INTEREST(S)

This work was funded by FONDECYT 11100443, PBCT-PSD51 (IDIMI) and FONDAP 15010006. None of the authors have any conflicts of interest to declare.