Endometrial Gene Expression Profiles Research Articles

Effect of duration of estradiol exposure on embryo survival and endometrial gene expression in anestrous embryo recipient mares

Previous studies indicate a positive correlation between the duration of estrus prior to ovulation and likelihood of pregnancy in embryo recipient mares. However, the mechanisms by which the duration of estrus before may affect fertility remains unclear. This study aimed to determine the effect of different durations of estradiol exposure, prior to progesterone administration, on embryo viability in anestrous recipient mares, and endometrial expression of genes thought to influence embryo survival. Three groups of anestrous recipient mares treated with different duration of estradiol were used: long (LE), short (SE) and no treatment (NE). Day 8 embryos were transferred into recipient mares four days after long-acting progesterone administration and recovered 48h later to examine embryo growth and viability. The endometrial gene expression profile of selected genes was also investigated. The likelihood of recovering an embryo 48h after transfer was 46.1% (6/13), 62.5% (5/8) and 85.7% (6/7) for recipient mares from the NE, SE and LE groups, respectively (P = .09). Embryos recovered from the different groups of recipients did not, however, differ in size, morphology or the proportion of nuclei undergoing mitosis (P > .05). Abundance of mRNA for uterocalin (P19) and insulin-like growth factor 1 (IGF1) were increased in the LE compared to the NE group, while fibroblast growth factor 2 (FGF2), progesterone receptor (PGR) and insulin-like growth factor 1 receptor (IGF1R) transcript abundances were increased (P < 0.05) in the NE group compared to both SE and LE groups. In conclusion, a longer exposure of the endometrium to estradiol before progesterone tended to improve embryo survival within 48h of transfer. However, the grade, growth rate, and proportion of mitotic cells in surviving embryos did not differ among groups. If embryos are destined to fail in a suboptimal endometrial environment, they die and disappear quickly. Moreover, a more adequately estradiol-primed uterus, before the progesterone rise, seems to create a uterine environment, in terms of P19, IGF1, FGF2 and PGR gene expression, more conducive to embryo survival and further development.

Endometrial gene expression in response to lipopolysaccharide between estrous cycle phases and uterine horns in cattle

Uterine bacterial community abundances shift throughout the estrous cycle, potentially altering the immunological environment of the uterus and impacting subsequent fertility. The objective of the current study was to evaluate the immunological impact of lipopolysaccharide (LPS), as a model for potentially pathogenic bacteria, throughout the uterine endometrium between the luteal and follicular phase of the estrous cycle. Bovine uterine tracts were harvested in mid-luteal (n = 7) or follicular (n = 7) phase. Explants were collected from the contralateral and ipsilateral horn relative to the dominant follicle or corpus luteum, then subjected to one of three treatments: uncultured control, cultured control, or cultured with LPS (1 µg/mL). Explants underwent RNA extraction and targeted RNA sequencing for expression analyses of 40 immune response related genes. Sequencing reads were mapped to Bos taurus genome in CLC Genomics Workbench. Resulting total read counts were normalized by housekeeping gene GAPDH and analyzed for overall expression profile by Orthogonal Projections to Latent Structures Discriminant Analysis (OPLS-DA) and Variable Importance in Projection (VIP) analyses in Metaboanalyst. Individual gene expression differences were determined by GLIMMIX procedure in SAS with fixed effects of treatment, estrous phase, uterine horn, and their interaction, with random effect of individual uterus. Expression of 29 genes were affected among treatment groups, with seven genes increased in LPS treatment compared to other groups (P &amp;lt; 0.05). Multiple genes were affected by estrous phase and uterine horn, independent of treatment (P &amp;lt; 0.05). The OPLS-DA analyses indicated overall gene expression differences due to clustering by estrous cycle and treatment (P &amp;lt; 0.001), with no effect of uterine horn (P &amp;gt; 0.10). Similar clustering was observed between luteal and follicular phase explants of controls, but distinct separate clustering between phases with LPS treatment (P = 0.001). According to VIP analyses, mucins were identified as contributing the most to differences observed between phase and treatment. In conclusion, estrous cycle phase resulted in differing overall endometrial gene expression profiles of immune response to LPS treatment. Therefore, altered immunological environment of the uterus in response to bacteria at different estrous cycle stages may lead to differences in reproductive success.

The mid-secretory endometrial transcriptomic landscape in endometriosis: a meta-analysis.

STUDY QUESTIONDo women with endometriosis have a different endometrial gene expression profile at the time of embryo implantation than women without endometriosis?SUMMARY ANSWERThe endometrial gene expression profile of women with endometriosis differs from that of women without endometriosis at the mid-secretory phase, although the differences are small.WHAT IS KNOWN ALREADYAbout 50% of women with endometriosis suffer infertility. Several molecular studies have suggested impaired endometrial receptivity in women with endometriosis, while others have detected no dysregulation of endometrial receptivity. Nevertheless, the previous endometrial transcriptome studies comparing women with and without endometriosis have been performed in small sample size with limited statistical power. We set out to systematically search and compile data of endometrial gene expression signatures at the receptive phase in women with endometriosis versus control women. Based on the obtained data, we conducted a meta-analysis of differentially expressed genes in order to raise the power of the analysis for identifying the molecular profiles of receptive phase endometria in endometriosis.STUDY DESIGN, SIZE, DURATIONA systematic literature search was conducted up to February 2022 following PRISMA criteria and included PubMed, Cochrane and Web of Science databases. For the systematic search, the term ‘endometriosis’ was paired with the terms ‘transcriptomics’, ‘transcriptome’, ‘gene expression’, ‘RNA-seq’, ‘sequencing’ and ‘array’, by using the Boolean operator ‘AND’ to connect them. Articles written in English were screened and interrogated for data extraction.PARTICIPANTS/MATERIALS, SETTING, METHODSA meta-analysis was performed on the selected studies to extract the differentially expressed genes described at the mid-secretory phase in women with endometriosis versus women without endometriosis in natural cycles, using the robust rank aggregation method. In total, transcriptome data of 125 women (78 patients and 47 controls) were meta-analysed, with a special focus on endometrial receptivity-specific genes based on commercial endometrial receptivity tests.MAIN RESULTS AND THE ROLE OF CHANCEIn total, 8 studies were eligible for the quantitative meta-analysis, gathering transcriptome data from the mid-secretory phase endometria of 125 women. A total of 7779 differentially expressed transcripts between the study groups were retrieved (3496 up-regulated and 4283 down-regulated) and were meta-analysed. After stringent multiple correction, there was no differential expression of any single molecule in the endometrium of women with endometriosis versus controls, while enrichment analysis detected that the pathways of chemotaxis and locomotion are dysregulated in endometriosis. Further analysis of endometrial receptivity-specific genes highlighted dysregulation of C4BPA, MAOA and PAEP and enrichment of immune and defence pathways in women with endometriosis.LIMITATIONS, REASONS FOR CAUTIONMost of the studies included into the meta-analysis were relatively small and had different study designs, which might have contributed to a bias.WIDER IMPLICATIONS OF THE FINDINGSThe current meta-analysis supports the hypothesis that endometrial receptivity is altered in women with endometriosis, although the changes are small. The molecules and pathways identified could serve as future biomarkers and therapeutical targets in detecting and treating endometriosis-associated infertility.STUDY FUNDING/COMPETING INTEREST(S)The authors declare no competing interests. This work was supported by the Spanish Ministry of Education, Culture and Sport [grant FPU15/01193] and the Margarita Salas program for the Requalification of the Spanish University system [grant UJAR01MS]; Spanish Ministry of Economy, Industry and Competitiveness (MINECO) and European Regional Development Fund (FEDER): grants RYC-2016-21199 and ENDORE SAF2017-87526-R; Programa Operativo FEDER Andalucía (B-CTS-500-UGR18; A-CTS-614-UGR20); the Junta de Andalucía [BIO-302; and PAIDI P20_00158]; the University of Jaén [PAIUJA-EI_CTS02_2017]; the University of Granada, Plan Propio de Investigación 2016, Excellence actions: Units of Excellence; Unit of Excellence on Exercise and Health (UCEES), and by the Junta de Andalucía, Consejería de Conocimiento, Investigación y Universidades and European Regional Development Fund (ERDF), ref. SOMM17/6107/UGR; the Estonian Research Council (grant PRG1076); Horizon 2020 innovation (ERIN, grant no. EU952516) of the European Commission and Enterprise Estonia (grant EU48695).TRIAL REGISTRATION NUMBERThe systematic review was registered at PROSPERO (identifier: CRD42020122054).

SARS-CoV-2 and Implantation Window: Gene Expression Mapping of Human Endometrium and Preimplantation Embryo.

Understanding whether SARS-CoV-2 could infect cells and tissues handled during ART is crucial for risk mitigation, especially during the implantation window when either endometrial biopsies are often practiced for endometrial receptivity assessment or embryo transfer is performed. To address this question, this review analyzed current knowledge of the field and retrospectively examined the gene expression profiles of SARS-CoV-2-associated receptors and proteases in a cohort of ART candidates using our previous Affymetrix microarray data. Human endometrial tissue under natural and controlled ovarian stimulation cycles and preimplantation embryos were analyzed. A focus was particularly drawn on the renin-angiotensin system, which plays a prominent role in the virus infection, and we compared the gene expression levels of receptors and proteases related to SARS-CoV-2 infection in the samples. High prevalence of genes related to the ACE2 pathway during both cycle phases and mainly during the mid-secretory phase for ACE2 were reported. The impact of COS protocols on endometrial gene expression profile of SARS-CoV-2-associated receptors and proteases is minimal, suggesting no additional potential risks during stimulated ART procedure. In blastocysts, ACE2, BSG, CTSL, CTSA and FURIN were detectable in the entire cohort at high expression level. Specimens from female genital tract should be considered as potential targets for SARS-CoV-2, especially during the implantation window.

O-141 Mapping of SARS-CoV-2-associated receptors and proteases mRNA in human endometrium during natural and stimulated cycles

Study questionCovid-19 pandemic has significantly affected the assisted reproductive technology (ART) practice. Understanding whether SARS-CoV-2 could infect endometrial tissues during ART is crucial for risk mitigationSummary answerAnalyses of gene expression profiles of SARS-CoV-2 host entry candidates from microarray data suggest that endometrium should be considered as potential target for SARS-CoV-2 infection.What is known alreadyVery few studies analyzed the gene expression profiles of SARS-CoV-2-associated receptors and proteases, mainly focusing on ACE2 and TMPRSS2 expression, resulting incomplete knowledge in different specimens from female genital tract. However, no studies have analyzed the potential impact of controlled ovarian stimulation (COS) protocols during ART procedure on the endometrial gene expression profiles of SARS-CoV-2-associated receptors and proteasesStudy design, size, durationTo address this question, we retrospectively examined the gene expression profile of SARS-CoV-2-associated receptors and proteases in endometrial biopsies of a cohort of ART candidates using Affymetrix microarray dataParticipants/materials, setting, methodsHuman endometrial tissue under natural (n = 62) and COS cycles (n = 42) were analyzed. A focus was particularly made on the renin-angiotensin system relates genes with a prominent role in the virus infection, and gene expression levels of receptors and proteases closely related to SARS-CoV-2 infectionwas also studied.Main results and the role of chanceUsing our large cohort of endometrial samples, we reported a high prevalence of genes related to the ACE2 pathway, including AGT, AGTR1, ANPEP, CTSA, ENPEP, LNPEP, MME, NLN, THOP1, BSG and CTSL during both phases(early- and mid-secretory phase), and mainly during the mid-secretory phase for ACE2. The highest signal intensities were found for CTSA, LNPEP, MME, NLN, BSG and CTSL. The most representative of dual coexpression of SARS-CoV-2-associated receptor and protease in endometrium was BSG-CSTL and BSG-CTSA. It s also important to note high variation of SARS-CoV-2 receptors inter-patients under natural cycle.Globally, the impact of COS on endometrial gene expression profile of SARS-CoV-2-associated receptors and proteases of non Covid-19 patients is low, suggesting no additional potential risks of SARS-CoV-2 infection during stimulated ART procedure compared with natural cycles.Limitations, reasons for cautionAnalyses of Affymetrix microarray gene expression data were performed in non-COVID-19 patients. Whether the SARS-CoV-2 infection changes the endometrial gene expression profile of SARS-CoV-2-associated receptors and proteases is under investigationWider implications of the findingsSpecimens from female genital tract may be considered as potential targets for SARS-CoV-2.Trial registration numbernot applicable

Analysis of the Endometrial Transcriptome at the Time of Implantation in Women Receiving a Single Post-Ovulatory Dose of Levonorgestrel or Mifepristone.

Levonorgestrel (LNG) is a progesterone receptor agonist used in both regular and emergency hormonal contraception; however, its effects on the endometrium as a contraceptive remain widely unknown and under public debate. To analyze the effects of LNG or mifepristone (MFP), a progesterone receptor antagonist and also known as RU-486, administered at the time of follicle rupture (FR) on endometrial transcriptome during the receptive period of the menstrual cycle. Ten volunteers ovulatory women were studied during two menstrual cycles, a control cycle and a consecutively treated cycle; in this last case, women were randomly allocated to two groups of 5 women each, receiving one dose of LNG (1.5 mg) or MFP (50 mg) the day of the FR by ultrasound. Endometrial biopsies were taken 6 days after drug administration and prepared for microarray analysis. Genomic functional analysis in the LNG-treated group showed as activated the bio-functions embryo implantation and decidualization, while these bio-functions in the T-MFP group were predicted as inhibited. The administration of LNG as a hormonal emergency contraceptive resulted in an endometrial gene expression profile associated with receptivity. These results agree on the concept that LNG does not affect endometrial receptivity and/or embryo implantation when used as an emergency contraceptive.

Levonorgestrel IUD: is there a long-lasting effect on return to fertility?

Intrauterine devices (IUDs) are effective and safe long-acting reversible contraceptive methods for preventing unplanned pregnancies. While extensive studies were conducted to evaluate return to fertility after removal of IUDs, majority of them were focused on multiparous women using copper IUDs. Current trends indicate increased use of levonorgestrel (LNG) IUDs in nulliparous women for very long periods of time, with both nulliparity and long duration of LNG-IUD use being potentially associated with trends towards longer time to conception post removal. Understanding the effects that LNG-IUDs may have on endometrial morphology and gene expression has important implications to further understanding their mechanism of action. Studies examining endometrial gene expression show persistent changes in receptivity markers up to 1 year after removal of an inert IUD, and no similar studies have been performed after removal of LNG-IUDs. Given the current gap in the literature and trends in LNG-IUD use in nulliparous young women, studies are needed that specifically look at the interaction of nulliparity, long-term use of LNG-IUD, and return to normal fertility. Herein, we review the available literature on the mechanism of action of IUDs with a specific focus on the effect on endometrial gene expression profile changes associated with IUDs.

MON-220 Androstendione Affects Endometrial Gene Expression Profile During Window of Implantation in Obese Infertile Women with PCOS

Context: PCOS affects endometrium receptivity that leads to poor reproductive outcomes. Most investigated markers of endometrial abnormalities in this population are related to steroid hormones-induced alterations, derangements in glucose metabolism and inflammation. A distinctive impact of obesity and altered steroid profile on endometrial enviroment in PCOS needs further exploration. Objective: We hypothesized that obese infertile PCOS women with high androstendione level exhibits different endometrial gene expression than obese infertile PCOS women with normal androstendione level when compared to non PCOS controls.Patients and Methods: Endometrium was obtained during the window of implantation by timed biopsy from 15 obese infertile women with PHO phenotype of PCOS as classified by Rotterdam criteria by presence ofPCO morphology (P), clinical or biochemical hyperandrogenic features (H) and oligo-amenorrhoea (O) (age 31.1±4.4 years, body weight 105,4 ±9,8kg) and from 7 infertile normal weight controls without PCOS (group C). Seven women with PCOS had high androstendione level (12,7 ±2,6 nmol/l (group A)) and 8 had normal androstendione ( 7,5 ±1,7 nmol/l (group B)). Total testosterone was increased in 6 out of 7 women in the group A, whereas all women in the group B had normal total testosterone. By RNA sequencing of endometrium we identified 4317 significantly differentially expressed genes (DEGs) comparing group A to C and 5344 differentially expressed genes comparing group B to C. DEGs were retrieved for pathway analysis. Results: Comparing group A to C, we observed the top enriched pathways to be associated with activation of androgen-related genes, including androgen receptor and LEF1 gene. In addition, we observed the enriched pathway associated with GSK3β that has been previously related with increased PCOS susceptibility.When comparing group B to C, the analysis of upstream regulators showed activation of estradiol-dependent pathways and deactivation of progesterone-dependent pathways, whereas activation of androgen associated pathways was not observed. We also detected down-regulation in metabolic part of insulin signalling pathways associated with GLUT4 expression.Conclusions: Endometrial gene expression in obese infertile PCOS women with high androstendione level was associated predominantly with altered androgen related genes, whereas endometrium in a group with PCOS and normal androstendione exhibited mainly activation in estradiol and deactivation of progesterone dependent pathways. Further investigation of the endometrial markers is critical to develop tailored therapies targeting endometrium related reproductive disorders in different PCOS phenotypes.

Gene expression and lymphocyte population at the fetal-maternal interface in sheep pregnancies established by somatic cell nuclear transfer.

The hypothesis of this study was that the leukocyte populations and expression levels of genes related to immune response, growth factors and apoptosis would be altered at the fetal-maternal interface in somatic cell nuclear transfer (SCNT)-generated sheep pregnancies. Placental and endometrial samples from sheep pregnancies established by SCNT and natural breeding (control) were collected at 45 days and at term. Expression of genes related to growth factors, apoptosis and immune response was examined using quantitative reverse transcription polymerase chain reaction. Endometrial leukocyte populations and major histocompatibility class I (MHC-I) protein expression were examined by immunohistochemistry. At term we observed altered expression of genes related to apoptosis, growth factors and immune response in placental and endometrial tissue of SCNT pregnancies. In Day-45 pregnancies there was less-pronounced abnormal expression and only genes related to apoptosis and growth factors were abnormal in the placenta. Endometrial gene expression profiles were similar to age-matched controls. Placental MHC-I protein expression was similar in SCNT and controls at 45 days but increased in the SCNT at term. The altered gene expression at the fetal-maternal interface likely contributes to the placental dysfunction and overgrowth observed in sheep SCNT pregnancies.

Differential gene expression profiling of endometrium during the mid-luteal phase of the estrous cycle between a repeat breeder (RB) and non-RB cows

BackgroundRepeat breeding directly affects reproductive efficiency in cattle due to an increase in services per conception and calving interval. This study aimed to investigate whether changes in endometrial gene expression profile are involved in repeat breeding in cows. Differential gene expression profiles of the endometrium were investigated during the mid-luteal phase of the estrous cycle between repeat breeder (RB) and non-RB cows using microarray analysis.MethodsThe caruncular (CAR) and intercaruncular (ICAR) endometrium of both ipsilateral and contralateral uterine horns to the corpus luteum were collected from RB (inseminated at least three times but not pregnant) and non-RB cows on Day 15 of the estrous cycle (4 cows/group). Global gene expression profiles of these endometrial samples were analyzed with a 15 K custom-made oligo-microarray for cattle. Immunohistochemistry was performed to investigate the cellular localization of proteins of three identified transcripts in the endometrium.ResultsMicroarray analysis revealed that 405 and 397 genes were differentially expressed in the CAR and ICAR of the ipsilateral uterine horn of RB, respectively when compared with non-RB cows. In the contralateral uterine horn, 443 and 257 differentially expressed genes were identified in the CAR and ICAR of RB, respectively when compared with non-RB cows. Gene ontology analysis revealed that genes involved in development and morphogenesis were mainly up-regulated in the CAR of RB cows. In the ICAR of both the ipsilateral and contralateral uterine horns, genes related to the metabolic process were predominantly enriched in the RB cows when compared with non-RB cows. In the analysis of the whole uterus (combining the data above four endometrial compartments), RB cows showed up-regulation of 37 genes including PRSS2, GSTA3 and PIPOX and down-regulation of 39 genes including CHGA, KRT35 and THBS4 when compared with non-RB cows. Immunohistochemistry revealed that CHGA, GSTA3 and PRSS2 proteins were localized in luminal and glandular epithelial cells and stroma of the endometrium.ConclusionThe present study showed that endometrial gene expression profiles are different between RB and non-RB cows. The identified candidate endometrial genes and functions in each endometrial compartment may contribute to bovine reproductive performance.

Endometrial gene expression profile of pregnant sows with extreme phenotypes for reproductive efficiency.

Prolificacy can directly impact porcine profitability, but large genetic variation and low heritability have been found regarding litter size among porcine breeds. To identify key differences in gene expression associated to swine reproductive efficiency, we performed a transcriptome analysis of sows’ endometrium from an Iberian x Meishan F2 population at day 30–32 of gestation, classified according to their estimated breeding value (EBV) as high (H, EBV > 0) and low (L, EBV < 0) prolificacy phenotypes. For each sample, mRNA and small RNA libraries were RNA-sequenced, identifying 141 genes and 10 miRNAs differentially expressed between H and L groups. We selected four miRNAs based on their role in reproduction, and five genes displaying the highest differences and a positive mapping into known reproductive QTLs for RT-qPCR validation on the whole extreme population. Significant differences were validated for genes: PTGS2 (p = 0.03; H/L ratio = 3.50), PTHLH (p = 0.03; H/L ratio = 3.69), MMP8 (p = 0.01; H/L ratio = 4.41) and SCNN1G (p = 0.04; H/L ratio = 3.42). Although selected miRNAs showed similar expression levels between H and L groups, significant correlation was found between the expression level of ssc-miR-133a (p < 0.01) and ssc-miR-92a (p < 0.01) and validated genes. These results provide a better understanding of the genetic architecture of prolificacy-related traits and embryo implantation failure in pigs.

Endometrial receptivity under hormone replacement therapy in oocyte-donation recipient patients: transcriptomic approach

Purpose: Few studies have investigated the endometrial receptivity status of oocyte-donation (OD) recipient patients at the specific hormone replacement therapy (HRT)-cycle timing (5 to 6 days after progesterone administration) where embryos at blastocyst stage were mostly replaced. The aim of our study was to analyse, during the implantation window, (i) the global endometrial gene expression profile, and (ii) the endometrial receptivity exploration by the Win-Test® in OD recipient patients under HRT compared to spontaneous cycle in patients awaiting for IVF.Material and methods: This study included OD recipient patients without (n=7) or with (OD RIF, n=20) repeated implantation failures and 12 normal responder patients in spontaneous cycles used as control. Endometrial biopsies were performed during the peri-implantation phase. Samples were analysed using DNA microarrays and the endometrial gene expression profiles of HRT-treated OD recipient patients and of patients in spontaneous cycles were compared. Then, specific biomarkers of endometrial receptivity were assessed in the two groups of HRT-treated OD patients in comparison to control patientsResults: The global gene expression profile of peri-implantation endometrial samples from HRT-treated OD recipients and from patients in spontaneous cycles was different with significant alterations in the oestrogen receptor signalling [GTF2H2B, POLR2B, POLR2E], VEGF family ligand-receptor interactions [VEGFR1, VEGFB] and integrin signalling [ITGAL, PAK7, ILK]. Using specific biomarkers of human endometrial receptivity, we found that endometrium was non-receptive (29 % and 43 % in OD and RIF OD patients, respectively) or partially receptive (71 and 43 % in OD and RIF OD patients, respectively), at Pg+5/+6, in majority of HRT-treated patients. In OD RIF patients, a delay of the implantation window was observed. However, by targeting personalized embryos transfer by identifying for each patient the HRT-cycle day where endometrium is receptive, with respect of the synchronization of embryo-endometrium dialogue, high pregnancy rate per frozen-thawed embryo replacement (50%) was obtained in OD RIF patients.Conclusion: This study underlines the need to take into account the individual patient’s response to HRT cycles and to move to a patient-tailored care management.

Endometrial gene expression profiling in pregnant Meishan and Yorkshire pigs on day 12 of gestation

BackgroundLitter size in pigs is a major factor affecting the profitability in the pig industry. The peri-implantation window in pigs is characterized by the coordinated interactions between the maternal uterine endometrium and the rapidly elongating conceptuses and represents a period of time during which a large percentage of the developing conceptuses are lost. However, the gene expression and regulatory networks in the endometrium contributing to the establishment of the maternal: placental interface remain poorly understood.ResultsWe characterized the endometrial gene expression profile during the peri-implantation stage of development by comparing two breeds that demonstrate very different reproductive efficiencies. We employed the porcine Affymetrix GeneChip® to assay the transcriptomic profiles of genes expressed in the uterine endometrium obtained from Meishan and Yorkshire gilts (n = 4 for each breed) on day 12 of gestation (M12 and Y12, respectively). Total of 17,076 probesets were identified as "present" in at least two arrays. A mixed model-based statistical analysis predicted a total of 2,656 (q < 0.1) transcripts as differentially expressed between Meishan and Yorkshire pigs. Eighteen differentially expressed transcripts of interest were validated by quantitative real-time PCR. Gene ontology (GO) annotation revealed that the known functions of the differentially expressed genes were involved in a series of important biological processes relevant to early pregnancy establishment in the pig.ConclusionsThe results identified endometrial gene expression profiles of two breeds differing in litter size and identified candidate genes that are related to known physiological pathways related to reproductive prolificacy. These findings provide a deeper understanding of molecular pathways differing between two breeds at the critical peri-implantation stage of pregnancy, which can be utilized to better understand the events contributing to pregnancy establishment in the pig.

Transcriptomic analysis of the porcine endometrium during early pregnancy and the estrous cycle

The goal of this study was to describe the alterations in the transcriptome of the endometrium in pigs during the beginning of implantation (days 15–16 of pregnancy) compared to cyclic pigs during the onset of luteolysis (days 15–16 of the estrous cycle). The global expression of genes in porcine gravid and non-gravid endometria was investigated using the Porcine (V2) Two-color gene expression microarray, 4×44 (Agilent, USA). Analysis of the microarray data showed that, of 589 accurately annotated genes, the expression of 266 genes was up-regulated and expression of 323 was down-regulated in the endometrium harvested during early pregnancy compared with the endometrium during the estrous cycle. In pregnant pigs, genes with the most significantly altered expression were involved in the following biological processes: the metabolic process, cellular process, cell communication, immune system process, developmental process, cell adhesion, antigen processing and presentation, antigen processing and presentation of peptide or polysaccharide antigen via major histocompatibility complex (MHC) class II, immune response, and the polysaccharide metabolic process. In the pregnant endometrium, cell adhesion molecules and steroid hormone biosynthesis pathways were the most significantly enriched biological pathways. Analysis of the interaction network among selected genes showed that androgen receptor (AR) encoding genes interact with genes involved in important processes occurring during early pregnancy. The bioinformatic analysis revealed information about the meaning of differentially expressed genes. The data provided new insight into the dynamic changes of the endometrial gene expression profile during days 15–16 of pregnancy.

Altered endometrial immune gene expression in beef heifers with retarded embryos

The aim of the present study was to compare endometrial gene expression profiles in a group of beef heifers yielding viable or retarded embryos on Day 7 after oestrus as a means of potentially explaining differences in embryo survival rates. Heifers were classified as either: (1) viable, when the embryo collected on Day 7 after oestrus was at the correct developmental stage (i.e. morula/early blastocyst); or (2) retarded, when the embryo was arrested at the 2-16-cell stage. The focus of the present study was on genes that were associated with either the pro- or anti-inflammatory immune response. Endometrial gene expression was determined using quantitative real-time polymerase chain reaction analysis. Expression of the β-defensin (DEFB1), interferon (IFN)-α (IFNA), IFN-γ (IFNG), interleukin (IL)-6 (IL6), IL-10 (IL10), forkhead box P3 (FOXP3) and natural cytotoxicity triggering receptor 1 (NCR1) genes was lower in endometria from viable than retarded heifers. Expression of the nuclear factor of kappa light polypeptide gene enhancer in B cells 1 (NKFB1), transforming growth factor (TGF)-β (TGFB), IFN-γ-inducible protein 16 (IFI16) and IL-21 (IL21) genes was higher in viable than retarded heifers. We propose that small disturbances in the expression of immune genes in the endometrium on Day 7 after oestrus can have detrimental effects on embryo survival.

Gene profiling of inflammatory genes in day 18 endometria from pregnant and non‐pregnant mares

Maternal recognition of pregnancy is a physiological process that primarily describes endometrial responses to a conceptus. Recognition of a conceptus prevents the release of prostaglandin F(2α) , thereby ensuring survival of the corpus luteum and continued progesterone production. Exactly how this occurs in the mare is poorly understood. Because prostaglandin F(2α) is a pro-inflammatory hormone, we hypothesized that differential gene expression in the endometrium at the time of maternal recognition reflects an anti-inflammatory event leading to decreased prostaglandin F(2α) secretion. Mares were inseminated, and endometrial biopsies were recovered from pregnant mares on Day 18 post-ovulation. In subsequent estrous cycles, mares were not inseminated and Day 18 post-ovulation endometrial biopsies were collected (non-pregnant control, matched per individual). Endometrial gene expression profiles were examined by screening an Affymetrix equine GeneChip containing probes specific for genes related to inflammatory processes. Microarray analysis revealed 118 genes that were up-regulated and 93 genes that were down-regulated (P < 0.001) at least 1.5-fold in the endometrium of pregnant versus non-pregnant mares. Quantitative, real-time RT-PCR confirmed the microarray results for three up-regulated genes homologous to TSC22D3, PPAPDC2, and KLF6, and three down-regulated genes homologous to ESR1, MARCKSL1, and EPSTI1 (P < 0.05). It is concluded that the presence of the equine embryo induces differential gene expression in the endometrium of Day 18 pregnant mares, and that these genes are associated with inflammatory processes and pathways involving cellular growth and proliferation. The results from this study provide important new insights into endometrial gene expression in response to early equine pregnancy.

Oviductal, endometrial and embryonic gene expression patterns as molecular clues for pregnancy establishment

In higher animals, the beginning of new life and transfer of genetic material to the next generation occurs in the oviduct when two distinct gametes cells unite resulting in the formation of a zygote. The zygote then undergoes serial developmental processes in the oviduct and enters into the uterus where it faces challenges and scrutiny from the endometrial ecosystem. Thus, embryos that are able to establish an appropriate embryo–maternal dialogue are capable of developing to term whereas the incompetent ones can perish any time during the gestation period. Although several lines of evidences indicated that pregnancy loss is a multi-factorial phenomenon, the biochemical composition of the embryo and maternal environment are the main players to determine pregnancy outcome. Indeed, expression patterns of the genes are the driving forces that induce biochemical composition changes in embryo, oviduct and uterine environment. Thus, examining the molecular signals that are associated with oviductal or endometrial receptivity and embryo implantation is essential for establishing strategies to improve pregnancy success. Therefore, this review focuses on the contribution of oviduct and its transcriptome profile on early stage embryo development and the impact of endometrium and its transcriptome changes on peri and post embryo implantation. In addition, this paper integrates established facts about hormonal and molecular signatures associated with endometrial receptivity. Finally, the blastocyst and pre-conception endometrial gene expression profiles have been discussed in relation to the pregnancy outcome to highlight the potentials of blastocyst and pre-transfer endometrial transcriptome profile approach for selecting appropriate recipient and developmentally competent embryo.

Endometrial expression of selected genes in patients achieving pregnancy spontaneously or after ICSI and patients failing at least two ICSI cycles

The objective of this study was to identify the endometrial gene expression profile in receptive phase, which could represent a useful prognostic tool for selecting IVF patients. Endometrial expression of 47 selected genes biopsied during the window of implantation in natural cycles was compared between patients who achieved a successful pregnancy spontaneously or after subsequent intracytoplasmic sperm injection (ICSI) cycles and patients who did not achieve a pregnancy after at least two failed ICSI cycles. The comparative analysis showed significantly different levels of expression in 19 genes, five implicated in apoptosis (CASP8, FADD, CASP10, APAF1, ANXA4), three in immunity (LIF, SPP1, C4BPA), five in transcriptional activity (MSX1, HOXA10, MSX2, HOXA11, GATA2), two in lipid metabolism (LEPR, APOD) and four in oxidative metabolism (AOX1, ALDH1A3, GPX3, NNMT). The evidence for these genes being differently expressed could represent the starting point of identifying the ideal receptive endometrial gene expression profile, which could be used in the future as a prognostic tool for IVF patients.Gene expression analysis technology has opened new important perspectives on the study of the physiological processes of different tissues and organs. Specifically for the endometrium, it would be really interesting to find out an endometrial gene expression profile of receptive phase, which could be used in future as a useful prognostic tool for selecting IVF patients. To achieve this aim, the objective of the present paper was the comparison of endometrial expression in natural cycles of 47 selected genes between the biopsies of patients who achieved a successful pregnancy, either spontaneously or after subsequent ICSI cycles, and those of patients who did not achieve a pregnancy after at least two failed ICSI cycles. The comparative analysis showed a significant different expression in 19 genes: five implicated in programmed cell death, known as apoptosis (CASP8, FADD, CASP10, APAF1, ANXA4), three in immunity (LIF, SPP1, C4BPA), five in transcriptional activity (MSX1, HOXA10, MSX2, HOXA11, GATA2), two in lipid metabolism (LEPR, APOD) and four in oxidative metabolism (AOX1, ALDH1A3, GPX3, NNMT). The evidence of these genes being differently expressed could represent the starting point of identifying the ideal receptive endometrial gene expression profile which could be used in the future as a prognostic tool for IVF patients.

Effect of single post-ovulatory administration of levonorgestrel on gene expression profile during the receptive period of the human endometrium

The hypothesis that levonorgestrel (LNG) used as an emergency contraceptive interferes with endometrial receptivity remains unproven. We compared the endometrial gene expression profile during the receptive period after administering a single dose of LNG 1.5 mg or placebo on day 1 of the luteal phase. An endometrial biopsy was done on day LH+7 or LH+8 and samples were taken from seven volunteers, each one contributing with one cycle treated with placebo and another with LNG. The expression of 20 383 genes was determined using cDNA microarrays. Real-time RT-PCR was used 1) to confirm the differences found in DNA microarray analysis and 2) to determine the effect of LNG on transcript levels of C3, C4BPα, COX2, MAOA, S100A4, and SERPINB9, known to be upregulated during receptivity, and on cPLA2α, JAK1, JNK1, CTSL1, and GSTP1, known to respond to mifepristone. Additional endometrial biopsies were done during the pre-receptive (LH+3) and receptive (LH+7) period and samples were taken from eight untreated volunteers in order to determine the changes associated with acquisition of receptivity of 14 genes. Mean levels of PAEP, TGM2, CLU, IGF2, and IL6ST mRNAs increased after administering LNG while those of HGD, SAT1, EVA1, LOC90133, ANXA1, SLC25A29, CYB5A, CRIP1, and SLC39A14 decreased. Except for the level of ANXA1 transcript, all changes remained within the range observed in untreated controls, and none of the transcripts responding to mifepristone changed in response to LNG. Post-ovulatory administration of LNG caused minimal changes in gene expression profiling during the receptive period. Neither the magnitude nor the nature or direction of the changes endorses the hypothesis that LNG interferes with endometrial receptivity.

Endometrial gene expression during early pregnancy differs between fertile and subfertile dairy cow strains

A receptive uterine environment is a key component in determining a successful reproductive outcome. We tested the hypothesis that endometrial gene expression patterns differ in fertile and subfertile dairy cow strains. Twelve lactating dairy cattle of strains characterized as having fertile (n = 6) and subfertile (n = 6) phenotypes underwent embryo transfer on day 7 of the reproductive cycle. Caruncular and intercaruncular endometrial tissue was obtained at day 17 of pregnancy, and microarrays used to characterize transcriptional profiles. Statistical analysis of microarray data at day 17 of pregnancy revealed 482 and 1,021 differentially expressed transcripts (P value < 0.05) between fertile and subfertile dairy cow strains in intercaruncular and caruncular tissue, respectively. Functional analysis revealed enrichment for several pathways involved in key reproductive processes, including the immune response to pregnancy, luteolysis, and support of embryo growth and development, and in particular, regulation of histotroph composition. Genes implicated in the process of immune tolerance to the embryo were downregulated in subfertile cows, as were genes involved in preventing luteolysis and genes that promote embryo growth and development. This study provides strong evidence that the endometrial gene expression profile may contribute to the inferior reproductive performance of the subfertile dairy cow strain.