Window Of Embryo Implantation Research Articles

Multiomics approaches to uncover endometrial receptivity in embryo implantation: A mini-review

Successful implantation requires concerted interactions during the apposition, adhesion, and invasion of the embryo into a receptive endometrium. However, the embryo implantation rate for assisted reproduction remains low despite the transfer of good quality embryos. Changes in endometrial transcriptomics, proteomics, lipidomics, and even microbiota all play important roles in embryo implantation. Specifically, the expression of steroid hormone-regulated adhesive and anti-adhesive molecules during the embryo implantation window is becoming an area of increasingly intense research. This review a) summarizes the different molecules expressed in the receptive endometrium and b) proposes the use of surface protein markers to predict pregnancy outcomes from assisted reproduction.

Endometrial microbial alterations disrupt endometrial immune homeostasis by overactivation of Eicosapentaenoic acid biosynthesis leading to altered endometrial receptivity

Embryo implantation is a key step in human reproduction, and the endometrium plays a key role in this process. Changes in the receptive state of the endometrium are one of the main reasons for embryo implantation failure. However, the mechanism underlying the altered endometrial receptivity remains unclear. In this study, we recruited 140 women undergoing assisted reproductive technology and divided them into a shifting group and a normal group based on their embryo implantation window results. Endometrial transcriptome data suggested that changes in the remodeling process of decidual spiral arterioles and changes in the immune environment might be important mechanisms of implantation window shift. The functional enrichment analysis results also suggested that the changes in microbiota had an important role in the changes in endometrial status. The endometrial functionally active microbial profiles were obtained based on previously validated metatranscriptomic analysis pipelines. Combining host gene expression information, immune cell abundance information and functionally active microbial abundance and activity information, we found that Treponema succinifaciens, Fusobacterium sp. oral taxon 203 and other potentially harmful species may over-activate Eicosapentaenoic acid (EPA) biosynthesis Thus, the balance of the immune environment of the endometrium is disrupted, resulting in the shift of the implantation window and the failure of embryo implantation.

Preimplantation triclosan exposure alters uterine receptivity through affecting tight junction protein†.

Triclosan is a broad-spectrum antibacterial agent and widely exists in environmental media and organisms. Triclosan exposure has been reported to have adverse effects on reproduction including embryo implantation disorder. During the embryo implantation window, it is vital that the endometrium develops into a receptive state under the influence of ovarian hormones. However, the effect of triclosan on embryo implantation and endometrial receptivity remains unclear. In the current study, we found a decreased embryo implantation rate, serum estrogen, and progesterone levels in mice exposed to triclosan from gestation days 0.5 to 5.5. Through RNA sequencing (RNA-seq), we identified nearly 800 differentially expressed genes, which were enriched in various pathways, including uterus development, inflammatory response, and immune system processes. Among those enriched pathways, the tight junction pathway is essential for the establishment of the receptive state of the endometrium. Then, genes involved in the tight junction pathway, including Cldn7, Cldn10, and Crb3, were validated by quantitative real-time polymerase chain reaction and the results were consistent with those from RNA-seq. Through immunofluorescence staining and western blotting, we confirmed that the tight junction protein levels of CLDN7 and CRB3 were increased. All these findings suggest that preimplantation triclosan exposure reduces the rate of embryo implantation through upregulating the expression of the tight junction genes and affecting the receptivity of the endometrium. Our data could be used to determine the sensitive time frame for triclosan exposure and offer a new strategy to prevent implantation failure.

Immunotoxicity and uterine transcriptome analysis of the effect of zearalenone (ZEA) in sows during the embryo attachment period

Zearalenone is a mycotoxin and a pollutant that is commonly found in crops. Once ingested, ZEA can cause disturbances in the immune system and produce immunotoxicity. However, there is little research on the effect of ZEA exposure on the relationship between immune regulation and embryo implantation in the uteri of sows. Embryo implantation relies upon the fact that the relationship between the maternal and fetal immune systems is balanced. This balance is provided by the joint regulation of immune organs, cytokines, and uterine immunity. In this study, we investigated 20 sows with an initial weight of 100.00 ± 5.00 kg and 200 days in age. The sows were fed with diets containing ZEA at concentrations of 0 mg/kg, 1 mg/kg, 2 mg/kg, and 10 mg/kg, respectively, from 8 to 14 days of gestation. We studied immunotoxicity and the uterine transcriptomics associated with the effect of ZEA in sows during embryo attachment. Following ZEA treatment, serum biochemical analysis and RT-qPCR were used to detect the concentration and mRNA expression levels of immunoglobulin IgA, IgG, and IgM, in the serum and spleen, respectively. The same analysis was carried out for a range of cytokines in the serum and spleen: IL-1, IL-2, IL-6, IL-10, and TNF. Uterine transcriptome analysis revealed 75, 215, and 81 genes that were differentially expressed in the 0 mg/kg vs 1 mg/kg treatment, 0 mg/kg vs 10 mg/kg treatment, and 1 mg/kg vs 10 mg/kg treatment, respectively. GO terms analysis showed that the up-regulated genes related to the immune system were highly expressed. KEGG pathway analysis further revealed the importance of several metabolic pathways, including drug metabolism-cytochrome P450, the cytokine-cytokine receptor interaction pathway, and calcium signaling pathways. The differentially expressed genes were confirmed by quantitative real-time PCR. These findings expand our understanding of the gene expression profiles and signaling pathways associated with the immune response to ZEA exposure in sows during the embryo implantation window. This study provides valuable information for clarifying the molecular mechanism of ZEA's immunotoxicity to early pregnant sows in the future.

Characterization of highly proliferative decidual precursor cells during the window of implantation in human endometrium.

Pregnancy depends on the wholesale transformation of the endometrium, a process driven by differentiation of endometrial stromal cells (EnSC) into specialist decidual cells. Upon embryo implantation, decidual cells impart the tissue plasticity needed to accommodate a rapidly growing conceptus and invading placenta, although the underlying mechanisms are unclear. Here we characterize a discrete population of highly proliferative mesenchymal cells (hPMC) in midluteal human endometrium, coinciding with the window of embryo implantation. Single-cell transcriptomics demonstrated that hPMC express genes involved in chemotaxis and vascular transmigration. Although distinct from resident EnSC, hPMC also express genes encoding pivotal decidual transcription factors and markers, most prominently prolactin. We further show that hPMC are enriched around spiral arterioles, scattered throughout the stroma, and occasionally present in glandular and luminal epithelium. The abundance of hPMC correlated with the in vitro colony-forming unit activity of midluteal endometrium and, conversely, clonogenic cells in culture express a gene signature partially conserved in hPMC. Cross-referencing of single-cell RNA-sequencing data sets indicated that hPMC differentiate into a recently discovered decidual subpopulation in early pregnancy. Finally, we demonstrate that recurrent pregnancy loss is associated with hPMC depletion. Collectively, our findings characterize midluteal hPMC as novel decidual precursors that are likely derived from circulating bone marrow-derived mesenchymal stem/stromal cells and integral to decidual plasticity in pregnancy.

Anti-phospholipid antibody may reduce endometrial receptivity during the window of embryo implantation

Anti-phospholipid antibodies (aPL) have been reported to be associated with repeated implantation failure (RIF), but the mechanism remains controversial. Endometrial receptivity is well known to be crucial for embryo implantation. This study aims to investigate the effect of aPL on endometrial receptivity in RIF women with positive aPL. Sixty-four infertile women with normal menstrual cycles were enrolled. The control group comprised 32 pregnant women with negative aPL who conceived successfully after their first in vitro fertilization-embryo transfer (IVF-ET) cycle, and the RIF group comprised 32 women with positive aPL. Endometrial biopsy samples were collected seven days after the luteinizing hormone surge (LH + 7). The expression of LIF and HOXA10 was evaluated by immunohistochemistry, qRT-PCR and Western blot. Endometrial pinopode development was examined by scanning electron microscopy. The mRNA expression of LIF and HOXA10 in the RIF group was significantly decreased compared with that in the control group during the implantation window. The immunohistochemistry and Western blot results confirmed these findings. Then, ultrastructural analyses of endometrial cells showed fewer pinopode processes, a more atypical morphology and increased atrophy in the RIF group compared with the control group, and these results were statistically significant. aPL positivity may inhibit the expression of LIF and HOXA10 in the endometrium and influence pinopode development. Our findings suggest that positivity for aPL is associated with impaired endometrial receptivity, which results in the development of RIF.

Zearalenone Blocks Autophagy Flow and Induces Cell Apoptosis During Embryo Implantation in Gilts.

Zearalenone (ZEA) has been proved to be toxic, particularly to the reproductive system of gilts. The effect of ZEA on gilts during embryo implantation window period is of particular interests. Here, we observed window stage dysontogenesis of gilts treated with ZEA. In endometrial tissues and cells, autophagosomes increased significantly and mitochondria were damaged with increasing ZEA concentration. Addition of autophagy inhibitor confirmed that ZEA blocks the autophagic flow in the fusion of autophagosomes and lysosomes. In conclusion, ZEA exposure during embryo implantation results in endometrium inflammation by activating autophagy while blocking autophagy flow at the same time, leading to the significant accumulation of autophagosomes. The aforementioned effects of ZEA induce the apoptosis of primary endometrial cells through the caspase3 pathway, which would break the uterus environment balance and finally lead to embryo implantation failure and dysontogenesis in gilts.

Mitochondrial dysfunction induced by high estradiol concentrations in endometrial epithelial cells

Abstract Context A supraphysiological estradiol (E2) concentration after ovarian stimulation is known to result in lower embryo implantation rates in in vitro fertilization (IVF). Endometrial epithelial cells (EECs) apoptosis occurs after the stimulation with high E2 concentrations, and mitochondria play important roles in cell apoptosis. Objective To investigate the mitochondrial function in EECs after the stimulation with high E2 concentrations. Materials and Methods Human EECs were purified and cultured with different E2 concentrations (10-10, 10-9, 10-8, 10-7 M) in vitro, in which 10-7 M is supraphysiologically high. Eight-week-old female mouse endometrium was obtained 5.5 days after the injection of 1.25 IU or 20 IU equine chorionic gonadotropin (eCG), roughly during the embryo implantation window, to examine the in vivo effects of high E2 concentrations on mouse EECs. Results In vivo and in vitro experiments demonstrated decreased mitochondrial DNA contents and ATP formation after EECs were stimulated with supraphysiologically high E2 concentrations than those stimulated with a physiologic E2 concentration. Less prominent immunofluorescence mitochondrial staining, fewer mitochondria number under electron microscopy, lower JC-1 aggregate/monomer ratio, and greater reactive oxygen species (ROS) production were found after EECs were stimulated with supraphysiologically high E2 concentrations. The high E2-induced ROS production was reduced when EECs were pretreated with N-acetyl-cysteine (NAC) in vitro, but remained unchanged after the pretreatment with coenzyme Q10. Conclusion High E2 concentrations increase extra-mitochondrial ROS production in EECs and subsequently result in mitochondrial dysfunction.

Mitochondrial Dysfunction Induced by High Estradiol Concentrations in Endometrial Epithelial Cells

Abstract Context A supraphysiological estradiol (E2) concentration after ovarian stimulation is known to result in lower embryo implantation rates in in vitro fertilization. Endometrial epithelial cell (EEC) apoptosis occurs after the stimulation with high E2 concentrations, and mitochondria play important roles in cell apoptosis. Objective To investigate the mitochondrial function in EECs after the stimulation with high E2 concentrations. Materials and Methods Human EECs were purified and cultured with different E2 concentrations (10-10, 10–9, 10–8, 10–7 M) in vitro, in which 10–7 M is supraphysiologically high. Eight-week-old female mouse endometrium was obtained 5.5 days after the injection of 1.25 IU or 20 IU equine chorionic gonadotropin, roughly during the embryo implantation window, to examine the in vivo effects of high E2 concentrations on mouse EECs. Results In vivo and in vitro experiments demonstrated decreased mitochondrial DNA contents and ATP formation after EECs were stimulated with supraphysiologically high E2 concentrations than those stimulated with a physiologic E2 concentration. Less prominent immunofluorescence mitochondrial staining, fewer mitochondria numbers under electron microscopy, lower 5,5′,6,6′-tetrachloro-1,1′,3,3′-tetraethylbenzimidazolylcarbocyanine iodide aggregate/monomer ratio, and greater reactive oxygen species (ROS) production were found after EECs were stimulated with supraphysiologically high E2 concentrations. The high E2-induced ROS production was reduced when EECs were pretreated with N-acetyl-cysteine in vitro, but remained unchanged after the pretreatment with coenzyme Q10. Conclusion High E2 concentrations increase extramitochondrial ROS production in EECs and subsequently result in mitochondrial dysfunction.

The suppressed autophagy induced by carbon disulfide could be rescued by N-carbamoyl glutamate during the window of embryo implantation in mice

To explore the effects of carbon disulfide (CS2) and N-carbamoyl glutamate (NCG) on autophagy during the window of embryo implantation in mice and whether dietary NCG supplementation can promote embryo implantation in case of CS2 exposure. Pregnant mice that received single intraperitoneal injection of CS2 on Gestational day (GD)4 were fed basal diet with or without NCG supplementation from GD1 to endpoints. The control mice were injected solvents. There were four endpoints (GD5, GD6, GD7 and GD9 endpoints) in each group. The uterus was collected on endpoints to detect autophagy-related markers by using the methods of transmission electron microscopy (TEM), immunohistochemistry (IHC), quantitative real-time polymerase chain reaction (qRT-PCR) and ELISA. The P62 brown punctate staining increased in CS2 exposure group and reduced after dietary NCG supplementation, which was opposite with LC3B, Beclin1 and ATG5 on GD5 endpoint. Simultaneously, P62 protein expression raised 43.33% on GD5 endpoint (p < 0.01) when exposed to CS2 and descended to the control level after NCG supplementation. The rate of decline of LC3B and Beclin1 proteins were 27.04% (p < 0.01) and 23.27% (p < 0.05) on GD5 endpoint, 20.20% (p < 0.05) and 11.30% on GD7 endpoint in CS2 exposure group, respectively, then NCG supplementation caused the LC3B and Beclin1 protein expression to rise in different degrees. Comparatively, the mRNA expression of all autophagy-related gene changed more apparently on three endpoints than the protein expression. The images of TEM showed that nearly no autophagosome could be seen in CS2 exposure group, while dietary NCG supplementation increased the number of autophagosome obviously on GD5 endpoint. The number of implanted embryos which declined due to CS2 exposure returned to normal in NCG supplementation group. Dietary NCG supplementation could rescue the suppressed autophagy induced by CS2 in the window of implantation and increase the number of implanted embryos.

Calpain7 impairs embryo implantation by downregulating \u03b23-integrin expression via degradation of HOXA10

Endometriosis (ENDO) is a common gynecological disease that causes infertility in many women. Previous studies noted that the dysregulation of Homeo box A10 (HOXA10) in the endometrium of women with ENDO was involved in the failure of embryo implantation. However, the mechanism by which HOXA10 expression is reduced in women with ENDO is still poorly understood. Here we found that a member of the calcium (Ca2+)-dependent cysteine protease family calpain7 (CAPN7), negatively correlated with HOXA10, was highly expressed in the endometrium of infertile women with ENDO and was significantly downregulated during the window of embryo implantation in mice. Overexpression of CAPN7 in Ishikawa cells or in the uterus of mice inhibited embryo implantation in vitro and in vivo. In the current study, we identified a sequence rich in proline, glutamic acid, serine, and threonine (PEST sequence) that enhanced the Ca2+-dependent degradation of HOXA10 by CAPN7. Furthermore, the interaction between HOXA10 and CAPN7 repressed the transcriptional activity and protein stability of HOXA10. In contrast, the administration of the calpain inhibitor ALLN reversed the CAPN7-induced HOXA10 degradation. Moreover, truncation of the PEST motif in HOXA10 abolished its CAPN7-dependent proteolysis. These studies reveal a novel pattern of HOXA10 regulation via PEST sequence-mediated calpain proteolysis that was demonstrated to be reversed by a calpain inhibitor. Thus, the inhibition of CAPN7-induced HOXA10 degradation may represent a novel potential therapeutic method to improve impaired embryo implantation in women with ENDO.

Inhibition of Endometrial Tiam1/Rac1 Signals Induced by miR-22 Up-Regulation Leads to the Failure of Embryo Implantation During the Implantation Window in Pregnant Mice.

This study assessed first the impact of endometrial Tiam1/Rac1 signals and microRNA-22 (miR-22) on embryo implantation in mice, and then the expression of the above three genes in the endometrium during the embryo implantation window in the natural menstrual cycle in women with repeated implantation failure (RIF) after in vitro fertilization treatment. Four hundred fifty-two Kun-ming female mice and 200 women (70 infertility patients with RIF, 130 women as controls) were entered into this study. Endometrial Tiam1/Rac1 signals and miR-22 expression were studied in clinical and mouse samples and serum estrogen (E2) and progesterone (P) were analyzed in clinical subjects. A pregnant mouse model based on an endometrial miR-22 and Tiam1 mRNA expression trend of patients with RIF was constructed and then the embryo implantation numbers were analyzed, and an ovariectomized mouse model was used to assess correlations of expression of these three genes with E2 and P. The results showed that during the embryo implantation window in the natural menstrual cycle, endometrial miR-22 was significantly higher whereas Tiam1/Rac1 signals were notably lower in patients with RIF than in controls, and the P:E2 ratio was statistically lower in the RIF group. Tiam1/Rac1 signal down-regulation and miR-22 up-regulation contributed to the inhibition of embryo implantation in mice. We also found a suppressive effect of miR-22 up-regulation on Tiam1/Rac1 signal expression, and reciprocal regulation of E2 and P for these three genes' expression in mice. In conclusion, miR-22 up-regulation and Tiam1/Rac1 signal down-regulation inhibited embryo implantation in mice; this mechanism may be partially due to the suppressive effect of miR-22 on Tiam1 expression, and is regulated to some extent by serum E2 and P. Our findings provide evidence that endometrial Tiam1/Rac1 signal down-regulation along with miR-22 up-regulation during embryo implantation window in the natural menstrual cycle may be one of the reasons for the failure of embryo implantation in patients with RIF.

Cyclic changes of S100A10 expression in human endometrium

To explore the cyclic changes of S100A10 expression in human endometrium. The gene and protein expression of S100A10 in human endometrium was examined by real-time polymerase chain reaction (PCR), immunohistochemical staining and Western blot. S100A10 protein was predominantly expressed in cytoplasm and cytomembrane of luminal and glandular epithelia. The S100A10 protein was continuously expressed from proliferative phase to secretory phase of menstrual cycle. However the expression in the secretory phase was much higher than in the proliferative phase (2.26 ± 0.17, 3.75 ± 0.22, 2.65 ± 0.20 vs 1.17 ± 0.11, 1.32 ± 0.14, both P < 0.05). Specifically, the highest level of S100A10 expression occurred during the mid-secretory phase. Then real-time PCR was used to analyze the mRNA expression of S100A10 in human endometrial samples at various points during the menstrual cycle. And the results confirmed the corresponding changes at the genetic level (0.50 ± 0.05, 1.02 ± 0.10, 0.55 ± 0.05 vs 0.25 ± 0.02, 0.30 ± 0.03, both P < 0.05). The endometrial expression of S100A10 increases during the window of embryo implantation. It suggests that it may increase the endometrial receptivity of uterine epithelial cells for embryos.

Profiles of cytokines secreted by isolated human endometrial cells under the influence of chorionic gonadotropin during the window of embryo implantation

BackgroundSeveral studies have indicated that human pre-implantation embryo-derived chorionic gonadotropin (hCG) may influence the implantation process by its action on human endometrial epithelial and stromal cells. Despite reports indicating that hCG acts on these cells to affect the production of several cytokines and growth factors (e.g., MIF, IGF-I, VEGF, LIF, IL-11, GMCSF, CXL10 and FGF2), our understanding of the integral influence of hCG on paracrine interactions between endometrial stromal and epithelial cells during implantation is very limited.MethodsIn the present study, we examined the profile of 48 cytokines in the conditioned media of primary cell cultures of human implantation stage endometrium. Endometrial epithelial cells (group 1; n = 20), stromal cells (group 2; n = 20), and epithelial plus stromal cells (group 3; n = 20) obtained from mid-secretory stage endometrial samples (n = 60) were grown on collagen and exposed to different doses (0, 1, 10 and 100 IU/ml) of rhCG for 24 h in vitro. Immunochemical and qRT-PCR methods were used to determine cytokine profiles. Enrichment and process networks analyses were implemented using a list of cytokines showing differential secretion in response to hCG.ResultsUnder basal conditions, endometrial epithelial and stromal cells exhibited cell type-specific profiles of secreted cytokines. Administration of hCG (100 IU) resulted in significantly (P < 0.05) different cytokine secretion profiles indicative of macropinocytic transport (HGF, MCSF) in epithelial cells, signal transduction (CCL4, FGF2, IL-1b, IL-6, IL-17, VEGF) in stromal cells, and epithelial-mesenchymal transition (FGF2, HGF, IL-1b, TNF) in mixed cells. Overall, the administration of hCG affected cytokines involved in the immune response, chemotaxis, inflammatory changes, proliferation, cell adhesion and apoptosis.ConclusionsCG can influence the function of the endometrium during blastocyst implantation via its differential action on endometrial epithelial and stromal cells. CG may also affect complex paracrine processes in the different endometrial cell types.

CD82 expression alters with human endometrial cycles and affects the uterine endometrial receptivity in vitro

Embryo implantation is a process that requires both temporal and spatial synchronization of the uterine endometrium and the embryo, and the endometrium becomes receptive to the embryo during the window of implantation. Although the expression patterns of many implantation-related molecules change dynamically during this process, the impact of CD82 on endometrial receptivity has not been elucidated. By immunohistochemical staining, we found that CD82 levels rose from the proliferative phase to the secretory phase in human endometrium. Specifically, the highest level appeared in mid- and late-secretory phases. Consistently, RL95-2 cells, representative of high-receptive endometrial epithelium, expressed higher levels of CD82 than did HEC-1A cells, which are representative of low-receptive endometrial epithelium, as detected by reverse transcription-polymerase chain reaction, Western blot and immunofluorescence. Furthermore, progesterone up-regulated the expression of CD82 in both epithelial cell lines. Down-regulation of CD82 in RL95-2 cells by either CD82 siRNA transfection or treatment with a CD82 antibody significantly decreased the adhesion of human embryonic JAR cells to RL95-2 cell monolayers (P < 0.01) and inhibited the phosphorylation of focal adhesion kinase (FAK). In contrast, up-regulation of CD82 in HEC-1A cells by CD82 cDNA transfection promoted embryonic JAR cell adhesion to HEC-1A monolayers (P < 0.05) and activated the phosphorylation of FAK. In conclusion, the expression of CD82 increases in endometrial tissues during the window of embryo implantation, CD82 expression affects endometrial receptivity of the uterine epithelial cells in vitro, and the FAK signaling pathway may be involved in this phenomenon. The correlation between CD82 and endometrial receptivity suggests that CD82 may serve as a potential marker of endometrial function.

HOXA10 regulates endometrial GABAAπ receptor expression and membrane translocation

Expression of the GABA(A) pi receptor has been described previously in the human endometrium in both luminal epithelium and stroma. Its expression is increased during decidualization in rodents and in the implantation window of human endometrium. Here we localized GABA pi subunit receptor protein in human endometrium and identified regulators of gene expression and activation. GABA(A) pi was localized to the cell surface, and expression increased during the window of embryo implantation in human endometrium. The well-differentiated human endometrial adenocarcinoma cell line Ishikawa was treated with progesterone and transfected with pcDNA-HOXA10, HOXA10 siRNA, or respective controls. GABA(A) pi receptor mRNA expression was evaluated by real-time RT-PCR. Protein expression and localization were evaluated using immunofluorescence. GABA(A) pi receptor mRNA expression was increased significantly after either progesterone treatment or HOXA10 transfection. Coadministration of progesterone along with HOXA10 transfection had no additional effect on the expression of GABA(A) pi receptor mRNA over either agent alone. Blocking HOXA10 expression with siRNA prevented progesterone-induced GABA(A) pi receptor mRNA expression. Additionally, either HOXA10 or progesterone independently caused increased translocation of the GABA receptor from the cytoplasm to the cell membrane. Translocation in response to progesterone was blocked with HOXA10 siRNA. Progesterone-induced GABA(A) pi subunit receptor expression is likely mediated indirectly through progesterone's regulation of HOXA10 expression. Modification of subtype composition and translocation of the GABA receptor ion channel likely modulate endometrial receptivity. Whereas HOXA10 typically enhances the expression of progesterone-responsive genes, here HOXA10 expression leads to production of a less progestin-responsive GABA receptor subtype, likely buffering the effects of luteal phase progesterone on GABA receptor activity.

The expression of specific genes and their predicated micro-RNA (miRNA) in human endometrium during the window of embryo implantation

Using microarray we identified a number of differently expressed genes and microRNAs (miRNAs), non-protein-coding small RNAs that regulate gene expression through mRNA degradation, in human endometrium. This study was designed to validate the expression of 23 of these genes functionally identified as inflammatory mediator, transcription factors, tissue turnover, cell growth etc. and their related miRNAs in the endometrium during the period of embryo implantation.

Uterine receptivity and the two and three dimensions of ultrasound

Uterine receptivity and the two and three dimensions of ultrasound

Assessment of changes in utero-ovarian arterial impedance during the peri-implantation period by Doppler sonography in women undergoing assisted reproduction.

To investigate changes in utero-ovarian blood flow during the peri-implantation period and their significance in successful embryo implantation. A prospective longitudinal study was conducted in 317 women undergoing in-vitro fertilization-embryo transfer (IVF-ET) treatment. All of them had at least one good-quality embryo for transfer on the second or third day after oocyte retrieval. Measurement of endometrial thickness and color flow imaging with pulsed waveform analysis of uterine and ovarian arteries were performed before ET and 5-6 days after ET. There were no significant differences in the age of patients, duration of infertility or number of embryos transferred between women who became pregnant (n = 91) and those who did not (n = 226). There was no difference in mean endometrial thickness between the two groups before ET, while a thicker endometrium was found in women who had conceived compared with those who had not 5-6 days after ET (P = 0.02). Mean uterine arterial resistance index (RI) and pulsatility index (PI) values were significantly lower in the pregnant than in the non-pregnant group before ET (P = 0.04 and P = 0.003, respectively), but no significant differences were found between the two groups 5-6 days after ET. In contrast, the mean ovarian arterial RI and PI values were similar between the two groups before ET, yet the pregnant group showed significantly lower RI and PI values compared with the non-pregnant group 5-6 days after ET (P = 0.002 and P = 0.01, respectively). A significantly higher peak systolic velocity (PSV) of intraovarian vessels was also noted in the pregnant group 5-6 days after ET. Different utero-ovarian blood flow changes during the peri-implantation period occur in conception and non-conception cycles in women following IVF. Doppler assessment of uterine arterial resistance can help to determine a time interval within the menstrual cycle that is of optimal endometrial status for embryo implantation in assisted conception programs. Delay in achieving adequate uterine perfusion during the temporal window of embryo implantation may have an impact on endometrial receptivity.

Messenger ribonucleic acid encoding interferon-inducible guanylate binding protein 1 is induced in human endometrium within the putative window of implantation.

The putative window of embryo implantation in the human opens between days 19--24 of the menstrual cycle. During this period, the endometrium undergoes distinctive structural and functional changes orchestrated by steroid hormones, growth factors, and cytokines to attain a receptive phase in which it acquires the ability to implant the developing embryo. A major challenge in the study of human reproduction is to identify the molecular signals that participate in the establishment of this critical receptive phase in the context of the natural cycle. Toward this goal, we analyzed human endometrial biopsies at various days of the menstrual cycle by employing messenger RNA (mRNA) differential display technique. We isolated several complementary DNAs representing genes that are either up- or down-regulated within the putative window of implantation. We identified one of these genes as that encoding interferon (IFN)-inducible guanylate-binding protein 1 (or GBP1), which possesses GTPase activity. Analysis of endometrial biopsies by Northern blotting and RT-PCR demonstrated that GBP1 mRNA is specifically induced at the midsecretory phase of the menstrual cycle. In situ hybridization analysis revealed that GBP1 mRNA expression is localized in the glandular epithelial cells as well as in the stroma in the immediate vicinity of the glands. We observed that treatment of human endometrial adenocarcinoma cell, Ishikawa, with IFN-gamma or IFN-alpha markedly induced the expression of GBP1 mRNA. IFN-gamma was, however, a more potent inducer of GBP1 than IFN-alpha. Consistent with this finding, the temporal profile of GBP1 expression during the menstrual cycle resembled that of IFN-gamma mRNA more closely than that of IFN-alpha, predicting a regulatory role of IFN-gamma in GBP1 expression in midsecretory human endometrium. Although the precise function of GBP1 in the receptive human uterus remains unclear, its unique expression overlapping the putative window of implantation suggests that it might serve as a useful marker of uterine receptivity in the human.