Differential endometrial gene expression in pregnant and nonpregnant sows

Genome-wide association study applied to prolificacy in Santa Inês sheep

This study aimed to identify genomic regions associated with prolificacy in Santa Inês sheep raised in tropical conditions. The prolificacy of the dam was defined as single (only one lamb born per ewe per lambing) or multiple (more than one animal born per ewe per lambing). After quality control of phenotypic data, 1584 lambing records of 715 females occurred between the years 2000 and 2018 were used. The animals were genotyped with the OvineSNP50 BeadChip panel (Illumina Inc.). After quality control of genomic data, information of 46,714 SNPs and 388 samples and females was used for the subsequent analyses. The single-step GWAS (ssGWAS) methodology was used to estimate the effects of genetic markers and their association with the prolificacy. A total of 21 windows of 10 adjacent SNPs that explained at least 0.5% of the additive genetic variance for prolificacy were identified. In such regions, genes associated with different reproductive functions in the female were found: CACNA1E, NTRK1, PLCH1, SMAD3, CENPF, TOPBP1, IL33, DRD2, MID1, HCCS, and ARHGAP6. Some candidate regions related to prolificacy harbor genes that were not previously described and genes without known functions. These results can help to identify genes associated with prolificacy and could be used in genomic reproductive studies on prolificacy, as well as in the selection of the most prolific ewes in the population.

Embryo-endometrial interaction associated with the location of the embryo during the mobility phase in mares

Embryo-maternal crosstalk is essential to establish pregnancy, with the equine embryo moving throughout the uterus on days 9-15 (ovulation = day 0) as part of this interaction. We hypothesized that the presence of a mobile embryo induces local changes in the gene expression of the endometrium. On Day 12, the endometrial transcripts were compared among three groups: uterine horn with an embryo (P+, n = 7), without an embryo (P-, n = 7) in pregnant mares, and both uterine horns of nonbred mares (NB, n = 6). We identified 1,101 differentially expressed genes (DEGs) between P+ vs. NB and 1,229 DEGs between P- vs. NB. The genes upregulated in both P+ and P- relative to NB were involved in growth factor pathway and fatty acid activation, while downregulated genes were associated with oxytocin signaling pathway and estrogen receptor signaling. Comparing the transcriptome of P+ to that of P-, we found 59 DEGs, of which 30 genes had a higher expression in P+. These genes are associated with regulating vascular growth factors and the immune system, all known to be essential in early pregnancy. Overall, this study suggests that the mobile embryo influences the endometrial gene expression locally.

Novel insights into conceptus-maternal signaling during pregnancy establishment in pigs

Pregnancy establishment in mammals, including pigs, requires coordinated communication between developing conceptuses (embryos with associated membranes) and the maternal organism. Porcine conceptuses signalize their presence by secreting multiple factors, of which estradiol-17β (E2) is considered the major embryonic signal initiating the maternal recognition of pregnancy. During this time, a limited supply of prostaglandin (PGF2α) to the corpora lutea and an increased secretion of luteoprotective factors (e.g., E2 and prostaglandin E2 [PGE2]) lead to the corpus luteum's maintained function of secreting progesterone, which in turn primes the uterus for implantation. Further, embryo implantation is related to establishing an appropriate proinflammatory environment coordinated by the secretion of proinflammatory mediators including cytokines, growth factors, and lipid mediators of both endometrial and conceptus origin. The novel, dual role of PGF2α has been underlined. Recent studies involving high-throughput technologies and sophisticated experimental models identified a number of novel factors and revealed complex relationships between these factors and those already established. Hence, it seems that early pregnancy should be regarded as a sequence of processes orchestrated by pleiotropic factors that are involved in redundancy and compensatory mechanisms that preserve the essential functions critical for implantation and placenta formation. Therefore, establishing the hierarchy between all molecules present at the embryo-maternal interface is now even more challenging.

Porcine salivary proteome analysis identifies potential early pregnancy-specific protein biomarkers

Early diagnosis of pregnancy is of utmost importance to optimize profit in pig husbandry. Identifying candidate protein biomarkers for early diagnosis of pregnancy in a non-invasive sample such as saliva may produce a colossallead to accomplish the purpose. Therefore, in this study, comparative salivary proteome profile of day 12 of gestation, representing elongation of blastocysts stage and non-pregnant sows was explored by label-free quantitation (LFQ) based mass spectrometry approach to identify early pregnancy biomarkers. A total of 115 proteins were identified as differentially expressed proteins (DEPs) with significant difference between non-pregnant and early pregnancy groups. Among the DEPs, majority of the proteins (82 out of 115 DEPs) were found to be down-regulated in early pregnancy group (fold change >2) compared to non-pregnant control. Functional classification and pathway analysis of the DEPs revealed involvement of most of the proteins in integrin signalling pathways, blood coagulation, carbohydrate metabolism, oxidative stress response and regulation of protein folding. Few DEPs with higher fold change during early pregnancy such as thioredoxin, heat shock 70 kDa protein 1A, alpha 1-S haptoglobin, and glutathione S-transferase pi 1 may have potential as biomarkers for early pregnancy diagnosis in pigs based on their recognized role in different pregnancy related activities. Overall, our results provide a set of salivary proteins which can be used as potential biomarkers for early pregnancy diagnosis after large scale validation.

Insulin-like growth factor system components expressed at the conceptus-maternal interface during the establishment of equine pregnancy

In many species, the insulin-like growth factors (IGF1 and IGF2), their receptors and IGF binding proteins play important roles in preparing the endometrium for implantation, and regulating conceptus growth and development. To determine whether the IGF system may contribute to conceptus-maternal interaction during equine pre-implantation development, we evaluated mRNA expression for IGF system components in conceptuses, and endometrium recovered from pregnant and cycling mares, on days 7, 14, 21 and 28 after ovulation. We also investigated expression of IGF1, IGF2 and their receptors 6 and 11 days after transfer of day 8 embryos to synchronous (day 8) or asynchronous (day 3) recipient mares. Expression of IGF1 and IGF2, IGF1R, IGF2R, INSR and IGFBPs 1, 2, 4 and 5 was evident in endometrium and conceptus membranes during days 7–28. Endometrial IGF2, INSR, IGFBP1 and IGFBP2 expression increased between days 7 and 28 of pregnancy. In conceptus membranes, expression of all IGF system components increased with developmental stage. Immunohistochemistry revealed strong expression of IGF1, IGF2 and IGF1R in both endometrium and conceptus membranes, whereas INSR was highly expressed in endometrium but barely detectable in the conceptus. Finally, a negatively asynchronous uterine environment retarded IGF1, IGF2 and INSR expression in the conceptus, whereas in the endometrium only INSR expression was altered by asynchrony. The presence of IGFs, their receptors and IGFBPs in the endometrium and conceptus during early equine pregnancy, and down-regulation in the conceptus following asynchronous embryo transfer, suggest a role in conceptus-maternal communication during the preparation for implantation.

Revisiting the Transcriptome Landscape of Pig Embryo Implantation Site at Single-Cell Resolution

Litter size is one of the most economically important traits in commercial pig farming. It has been estimated that approximately 30% of porcine embryos are lost during the peri-implantation period. Despite rapid advances over recent years, the molecular mechanism underlying embryo implantation in pigs remains poorly understood. In this study, the conceptus together with a small amount of its surrounding endometrial tissues at the implantation site was collected and subjected to single-cell RNA-seq using the 10x platform. Because embryo and maternal endometrium were genetically different, we successfully dissected embryonic cells from maternal endometrial cells in the data according to single nucleotide polymorphism information captured by single-cell RNA-seq. Undoubtedly, the interaction between trophoblast cells and uterine epithelial cells represents the key mechanism of embryo implantation. Using the CellChat tool, we revealed cell-cell communications between these 2 cell types in terms of secreted signaling, ECM-receptor interaction and cell-cell contact. Additionally, by analyzing the non-pregnant endometrium as control, we were able to identify global gene expression changes associated with embryo implantation in each cell type. Our data provide a valuable resource for deciphering the molecular mechanism of embryo implantation in pigs.

Influence of Genotype on Endometrial Angiogenesis during Early Pregnancy in Piau and Commercial Line Gilts

This study aimed to evaluate the endometrial angiogenesis of pregnant commercial line and Piau gilts during early pregnancy. We used 27 gilts, divided into three groups according to the type of mating: Commercial (n = 9), commercial line females mated with commercial line males; Cross-mated (n = 9), Piau females mated with commercial line males; and Piau (n = 9), Piau females mated with Piau males. Each group was divided into three subgroups based on gestational age at the time of slaughter (7, 15, and 30 days of pregnancy). Immediately after slaughter, endometrial samples were obtained for histological evaluation and for analysis of the relative transcript abundance (RTA) of angiogenesis-related genes (HIF1α, FGF9, ANG1, TEK, VEGFA, ANGPT1, and ANGPT2). The number of endometrial glands was similar among groups but decreased with gestational age (p < 0.05). Piau females showed a higher number of blood vessels (p < 0.05) at 7 and 15 days of pregnancy, but no differences were observed among groups at 30 days, suggesting an influence of the male genotype on the pattern of uterine vascularization. There were no differences among groups for RTA of the FGF9, HIF1α, TEK, VEGFA, ANGPT1, and ANGPT2 genes. The HIF1α-gene RTA was higher at 7 and 15 days of pregnancy; for TEK and ANGPT1, the RTA was higher at 15 days of pregnancy; and the RTA of VEGFA and ANGPT2 genes were higher at 30 days of pregnancy. The ANG1 RTA was similar for pregnancies in the commercial and Piau groups but was higher (p < 0.05) at 15 days in the Cross-mated group, suggesting an interaction between genotypes. Overall, the pattern found for the RTA of angiogenesis-related genes was similar among the groups in this study, although some phenotypic differences could be noted, such as the highest number of blood vessels being found during early pregnancy of Piau gilts. The results of the gene RTA when crossed with phenotypic data led to conclusions that are conflicting with those reported in the literature. However, noteworthy is that angiogenesis is a complex process in which the balance between stimulatory and inhibitory factors may be related to time.

Identification of genes associated with susceptibility to persistent breeding-induced endometritis by RNA-sequencing of uterine cytobrush samples

This study aimed to investigate the susceptibility to persistent breeding-induced endometritis (PBIE). Cytobrush samples were collected from 81 broodmares 1-3 days before artificial insemination (AI). Susceptibility to PBIE was evaluated by the presence of ≥ 2 cm of intrauterine fluid 24 h after AI, besides the fertility was determined by a sonographic pregnancy diagnosis 2 weeks after ovulation. RNA expressions were compared between susceptible non-pregnant (SNP) mares (n=9) and resistant pregnant (RP) mares (n=9) as well as between susceptible pregnant (SP) mares (n=9) and susceptible non-pregnant (SNP) mares. 66 differentially expressed genes (DEGs) were identified between SNP and RP mares and 60 DEGs between SP and SNP mares. In SNP compared to RP mares, transcript levels of genes regulating steroid hormone metabolism and neutrophil chemotaxis were lower, while higher for genes participating in uterine inflammation.Transcripts of genes related to extracellular matrix degradation, tissue adhesions, and fibrosis were lower in SP mares than in SNP mares, while higher for genes related to uterine cell proliferation, differentiation, and angiogenesis in SP mares than SNP mares. In conclusion, increased transcript levels of apolipoprotein E (APOE) and roundabout 2 (ROBO2), cluster domain 44 (CD44), integrin beta 3 (ITGB3), and epidermal growth factor (EGF) are possible biomarkers for susceptibility to PBIE. While higher expression of fibroblast growth factor 9 (FGF9), kinase domain receptor (KDR), and C-X-C motif chemokine ligand (CXCL) 16, collagen type V alpha 2 (COL5A2) and fibronectin (FN1) are suggested indicators of fertility in susceptible mares if they receive proper breeding management.

Comparative Transcriptome Analysis of Milk Somatic Cells During Lactation Between Two Intensively Reared Dairy Sheep Breeds

In dairy sheep industry, milk production dictates the value of a ewe. Milk production is directly related to the morphology and physiology of the mammary gland; both being designated targets of breeding strategies. Although within a flock breeding parameters are mutual, large differences in milk production among individual ewes are usually observed. In this work, we tested two of the most productive dairy sheep breeds reared intensively in Greece, one local the Chios breed and one foreign the Lacaune breed. We used transcriptome sequencing to reveal molecular mechanisms that render the mammary gland highly productive or not. While highly expressed genes (caseins and major whey protein genes) were common among breeds, differences were observed in differentially expressed genes. ENSOARG00000008077, as a member of ribosomal protein 14 family, together with LPCAT2, CCR3, GPSM2, ZNF131, and ASIP were among the genes significantly differentiating mammary gland's productivity in high yielding ewes. Gene ontology terms were mainly linked to the inherent transcriptional activity of the mammary gland (GO:0005524, GO:0030552, GO:0016740, GO:0004842), lipid transfer activity (GO:0005319) and innate immunity (GO:0002376, GO:0075528, GO:0002520). In addition, clusters of genes affecting zinc and iron trafficking into mitochondria were highlighted for high yielding ewes (GO:0071294, GO:0010043). Our analyses provide insights into the molecular pathways involved in lactation between ewes of different performances. Results revealed management issues that should be addressed by breeders in order to move toward increased milk yields through selection of the desired phenotypes. Our results will also contribute toward the selection of the most resilient and productive ewes, thus, will strengthen the existing breeding systems against a spectrum of environmental threats.

Equine early pregnancy endocrine profiles and ipsilateral endometrial immune cell, gene expression and protein localisation response

We investigated the early effects of the equine embryo on maternal serum concentrations of insulin-like growth factor 1 (IGF1), leptin and adiponectin, uterine immune cells and genes and proteins related to embryo development and the maintenance of pregnancy. Ipsilateral endometrial expression was assessed on Days 7 and 13 after ovulation for the following transcripts: oestrogen receptor ERα (ESR1), progesterone receptor (PGR), progestin and adipoQ receptor family member 5 (PAQR5), oxytocin receptor (OXTR), prostaglandin-endoperoxide synthase 2 (PTGS2), raf-1 proto-oncogene serine/threonine kinase (RAF1), p21-activated kinase 6 (PAK6), fibroblast growth factor family member 9 (FGF9), IGF1 and its receptor (IGF1R), mucin 1 (MUC1), osteopontin (OPN), leptin receptor (LEPR) and adiponectin receptors 1 and 2 (ADIPOR1 and ADIPOR2). Ipsilateral endometrial immunological cell infiltration and immunohistochemical protein localisation were evaluated on Days 7, 10 and 13 after ovulation for ERα, PGR, OXTR, PTGS2, IGF1, IGF1R, IGF2 and MUC1. Serum hormone concentrations were not affected by reproductive status. Pregnancy downregulated ESR1 and PGR mRNA levels, upregulated the expression of all other genes and affected the expression of all genes, except PGR, on Day 7 (compared with eight genes affected at Day 13). Proteins were affected by pregnancy or by its interaction with other variables (day of extraction and endometrial compartment). Pregnant mares had a higher lymphocyte count, which decreased towards Day 13. The effect of pregnancy on leucocytes and proteins was more evident in superficial endometrial compartments. The results of this study suggest that the equine embryo exerts prompt paracrine regulation of critical biological processes.

Synergistic action of estradiol and PGE2 on endometrial transcriptome in vivo resembles pregnancy effects better than estradiol alone†

Successful pregnancy establishment in mammals depends on numerous interactions between embryos and the maternal organism. Estradiol-17β (E2) is the primary embryonic signal in the pig, and its importance has been questioned recently. However, E2 is not the only molecule of embryonic origin. In pigs, prostaglandin E2 (PGE2) is abundantly synthesized and secreted by conceptuses and endometrium. The present study aimed to determine the role of PGE2 and its simultaneous action with E2 in changes in porcine endometrial transcriptome during pregnancy establishment. The effects of PGE2 and PGE2 acting with E2 were studied using an in vivo model of intrauterine hormone infusions, and were compared to the effects of E2 alone and conceptuses' presence on day 12 of pregnancy. The endometrial transcriptome was profiled using gene expression microarrays followed by statistical analyses. Downstream analyses were performed using bioinformatics tools. Differential expression of selected genes was verified by quantitative polymerase chain reaction. Microarray analysis revealed 2413 differentially expressed genes (DEGs) in the endometrium treated simultaneously with PGE2 and E2 (P < 0.01). No significant effect of PGE2 administered alone on endometrial transcriptome was detected. Gene ontology annotations enriched for DEGs were related to multiple processes such as: focal adhesion, vascularization, cell migration and proliferation, glucose metabolism, tissue remodeling, and activation of immune response. Simultaneous administration of E2 and PGE2 induced more changes within endometrial transcriptome characteristic to pregnancy than infusion of E2 alone. The present findings suggest that synergistic action of estradiol-17β and PGE2 resembles the effects of pregnancy on endometrial transcriptome better than E2 alone.

Prolonged Effect of Seminal Plasma on Global Gene Expression in Porcine Endometrium

Seminal plasma (SP) deposited in the porcine uterine tract at the time of mating is known to elicit an initial response that is beneficial for pregnancy outcome. However, whether SP has any long-term effect on alterations in endometrial molecular and cellular processes is not known. In this study, using microarray analyses, differential changes in endometrial transcriptome were evaluated after Day 6 of SP-infusion (6DPI) or Day 6 of pregnancy as compared to corresponding day of estrous cycle. Both, pregnancy and SP induced significant changes in the endometrial transcriptome and most of these changes were specific for a particular group. Functional analysis of differentially expressed genes (DEGs) using Ingenuity Pathway Analysis revealed that inhibition in immune response was affected by both pregnancy and SP infusion. Long-term effects of SP included differential expression of genes involved in inhibition of apoptosis, production of reactive oxygen species and steroid biosynthesis, and activation of processes such as proliferation of connective tissue cells and microvascular endothelial cells. Moreover, interleukin-2 and interferon-γ was identified to be responsible for regulating expression of many DEGs identified on 6DPI. The present study provides evidence for the long-term effects of SP on porcine endometrium that can be beneficial for pregnancy success.

Pleiotropic role of prokineticin 1 in the porcine endometrium during pregnancy establishment and embryo implantation †

Acquisition of endometrial receptivity for embryo implantation is one of the crucial processes during pregnancy and is induced mainly by progesterone and enhanced by conceptus signals. Prokineticin 1 (PROK1) is characterized as a secretory protein with diverse functions in various tissues, including the reproductive tract. PROK1, with its receptor PROKR1, are up-regulated in the porcine endometrium during implantation and in women's receptive endometrium and decidua. However, the function of PROK1 in embryo-maternal communication has still not been fully elucidated. Hence, we hypothesize that PROK1 is involved in endometrial receptivity development and implantation in pigs. In this study, using the porcine in vivo model of intrauterine infusions of estradiol-17β (E2) and prostaglandin E2 (PGE2), we revealed that these hormones elevated endometrial expression of PROK1 and PROKR1 mRNA, respectively. Moreover, E2, acting synergistically with PGE2, increased PROKR1 protein expression. We also evidenced that PROK1-PROKR1 signaling induced expression of following genes and/or proteins CCN2, CDH13, FGF2, NFATC2, ANGPT1, ANGPT2, CDH1, MUC4, SPP1, IFNG, IL6, LIF, LIFR, TNF, TGFB3, and FGF9, as well as phosphorylation of PTK2 and secretion of IL6 and IL11 by endometrial explants in vitro. Ingenuity pathway analysis revealed that functions associated with the PROK1-regulated genes/proteins include cell-to-cell contact, cell attachment, migration and viability, differentiation of epithelial tissue, leukocyte migration, inflammatory response, angiogenesis, and vasculogenesis. Summarizing, our study suggests that PROK1 acts pleiotropically as an embryonic signal mediator that regulates endometrial receptivity by increasing the expression of the genes and proteins involved in implantation and pregnancy establishment in pigs.

Identification of Differentially Expressed Gene Transcripts in Porcine Endometrium during Early Stages of Pregnancy

During the early stages of pregnancy, the uterine endometrium undergoes dramatic morphologic and functional changes accompanied with dynamic variation in gene expression. Pregnancy-stage specific differentially expressed gene (DEG)-transcript-probes were investigated and identified by comparing endometrium transcriptome at 9th day (9D), 12th day (12D) and 16th day (16D) of early pregnancy in Polish large-white (PLW) gilts. Endometrium comparisons between 9D-vs-12D, 9D-vs-16D and 12D-vs-16D of early pregnancy identified 6049, 374 and 6034 highly significant DEG-transcript-probes (p < 0.001; >2 FC). GO term enrichment analysis identified commonly shared upregulated endometrial DEG-transcript-probes (p < 0.001; >2 FC), that were regulating the gene functions of anatomic structure development and transport (TG), DNA-binding and methyltransferase activity (ZBTB2), ion-binding and kinase activity (CKM), cell proliferation and apoptosis activity (IL1B). Downregulated DEG-transcript-probes (p < 0.001; >2 FC) were involved in regulating the gene functions of phosphatase activity (PTPN11), TC616413 gene-transcript and Sus-scrofa LOC100525539. Moreover, blastn comparison of microarray-probes sequences against sus-scrofa11 assembly identified commonly shared upregulated endometrial DEG-transcript-probes (E < 0.06; >2 FC), that were regulating the gene functions of reproduction and growth (SELENOP), cytoskeleton organization and kinase activity (CDC42BPA), phosphatase activity (MINPP1), enzyme-binding and cell-population proliferation (VAV3), cancer-susceptibility candidate gene (CASC4), cytoskeletal protein-binding (COBLL1), ion-binding, enzyme regulator activity (ACAP2) Downregulated endometrial DEG-transcript-probes (E < 0.06; >2FC) were involved in regulating the gene functions of signal-transduction (TMEM33), catabolic and metabolic processes (KLHL15). Microarray validation experiment on selected candidate genes showed complementarity to significant endometrial DEG-transcript-probes responsible for the regulation of immune response (IL1B, S100A11), lipid metabolism (FABP3, PPARG), cell-adhesion (ITGAV), angiogenesis (IL1B), intercellular transmission (NMB), cell-adhesion (OPN) and response to stimuli (RBP4) was confirmed by RT-PCR. This study provides a clue that identified pregnancy-stage specific microarray transcript probes could be considered as candidate genes for recognition and establishment of early pregnancy in the pig.

MiRNAs in the Peri-Implantation Period: Contribution to Embryo-Maternal Communication in Pigs

MicroRNAs (miRNAs) constitute a large family of noncoding RNAs, approximately 22 nucleotides long, which function as guide molecules in RNA silencing. Targeting most protein-coding transcripts, miRNAs are involved in nearly all developmental and pathophysiological processes in animals. To date, the regulatory roles of miRNAs in reproduction, such as fertilization, embryo development, implantation, and placenta formation, among others, have been demonstrated in numerous mammalian species, including domestic livestock such as pigs. Over the past years, it appeared that understanding the functions of miRNAs in mammalian reproduction can substantially improve our understanding of the biological challenges of successful reproductive performance. This review describes the current knowledge on miRNAs, specifically in relation to the peri-implantation period when the majority of embryonic mortality occurs in pigs. To present a broader picture of crucial peri-implantation events, we focus on the role of miRNA-processing machinery and miRNA–mRNA infarctions during the maternal recognition of pregnancy, leading to maintenance of the corpus luteum function and further embryo implantation. Furthermore, we summarize the current knowledge on cell-to-cell communication involving extracellular vesicles at the embryo–maternal interface in pigs. Finally, we discuss the potential of circulating miRNAs to serve as indicators of ongoing embryo–maternal crosstalk.

Estradiol-17β-Induced Changes in the Porcine Endometrial Transcriptome In Vivo

Estradiol-17β (E2) is a key hormone regulating reproductive functions in females. In pigs, E2, as the main conceptus signal, initiates processes resulting in prolonged corpus luteum function, embryo development, and implantation. During early pregnancy the endometrium undergoes morphological and physiological transitions that are tightly related to transcriptome changes. Recently, however, the importance of E2 as a primary conceptus signal in the pig has been questionable. Thus, the aim of the present study was to determine the effects of E2 on the porcine endometrial transcriptome in vivo and to compare these effects with transcriptome profiles on day 12 of pregnancy. Microarray analysis revealed differentially expressed genes (DEGs) in response to E2 with overrepresented functional terms related to secretive functions, extracellular vesicles, cell adhesion, proliferation and differentiation, tissue rearrangements, immune response, lipid metabolism, and many others. Numerous common DEGs and processes for the endometrium on day 12 of pregnancy and E2-treated endometrium were identified. In summary, the present study is the first evidence for the effect of E2 on transcriptome profiles in porcine endometrium in vivo in the period corresponding to the maternal recognition of pregnancy. The presented results provide a valuable resource for further targeted studies considering genes and pathways regulated by conceptus-derived estrogens and their role in pregnancy establishment.

Whole-genome sequence analysis reveals candidate genomic footprints and genes associated with reproductive traits in Thoroughbred horse

The primary objective of most horse breeding operations was to maximize reproductive efficiency and minimize the cost of producing live foals. Here, we compared individual horses from the Thoroughbred population (n = 17), known as a horse breed with poor reproductive performance, with other six horse populations (n = 28), to detect genomic signatures of positive selection underlying of reproductive traits. A number of protein-coding genes with significant (p-value <.01) higher F_ST values (616 genes) and a lower value for nucleotide diversity (π) (310 genes) were identified. The results of our study revealed some candidate genes such as IGFBP2, IGFBP5, GDF9, BRINP3 and GRID1 are possibly associated with functions influencing reproductive traits. These genes may have been under selection due to their essential roles in reproduction performance in horses. The candidate selected genes identified in this work should be of great interest for future research into genetic architecture of traits relevant to horse breeding programmes.

Seminal Plasma Modifies the Transcriptional Pattern of the Endometrium and Advances Embryo Development in Pigs

Background: Seminal plasma (SP) promotes sperm survival and fertilizing capacity, and potentially affects embryo development, presumably via specific signaling pathways to the internal female genital tract.

Objectives: This study evaluated how heterologous SP, infused immediately before postcervical artificial insemination (AI) affected embryo development and the transcriptional pattern of the pig endometria containing embryos.

Materials and Methods: Postweaning estrus sows (n = 34) received 40-mL intrauterine infusions of either heterologous pooled SP or Beltsville Thawing Solution (BTS; control) 30 min before AI of semen extended to 10% of homologous SP. Embryos (all sows) and endometrium samples (3 sows/group) were removed during laparotomy 6 days after the infusion of SP or BTS to morphologically evaluate the embryos to determine their developmental stage and to analyze the endometrial transcriptome using microarrays (PORGENE 1.0 ST GeneChip array, Affymetrix) followed by qPCR for further validation.

Results: Embryo viability was equal between the groups (~93%), but embryo development was significantly (P < 0.05) more advanced in the SP-treated group compared to control. A total of 1,604 endometrium transcripts were differentially expressed in the SP group compared to the control group. An enrichment analysis showed an overrepresentation of genes and pathways associated with the immune response, cytokine signaling, cell cycle, cell adhesion, and hormone response, among others.

Conclusions: SP infusions prior to AI positively impacted the preimplantation embryo development and altered the expression of the endometrial genes and pathways potentially involved in embryo development.

Cell type-specific endometrial transcriptome changes during initial recognition of pregnancy in the mare

Previous endometrial gene expression studies during the time of conceptus migration did not provide final conclusions on the mechanisms of maternal recognition of pregnancy (MRP) in the mare. This called for a cell type-specific endometrial gene expression analysis in response to embryo signals to improve the understanding of gene expression regulation in the context of MRP. Laser capture microdissection was used to collect luminal epithelium (LE), glandular epithelium and stroma from endometrial biopsies from Day 12 of pregnancy and Day 12 of the oestrous cycle. RNA sequencing (RNA-Seq) showed greater expression differences between cell types than between pregnant and cyclic states; differences between the pregnant and cyclic states were mainly found in LE. Comparison with a previous RNA-Seq dataset for whole biopsy samples revealed the specific origin of gene expression differences. Furthermore, genes specifically differentially expressed (DE) in one cell type were found that were not detectable as DE in biopsies. Overall, this study revealed spatial information about endometrial gene expression during the phase of initial MRP. The conceptus induced changes in the expression of genes involved in blood vessel development, specific spatial regulation of the immune system, growth factors, regulation of prostaglandin synthesis, transport prostaglandin receptors, specifically prostaglandin F receptor (PTGFR) in the context of prevention of luteolysis.

Spatial organization of endometrial gene expression at the onset of embryo attachment in pigs

BACKGROUND

During the preimplantation phase in the pig, the conceptus trophoblast elongates into a filamentous form and secretes estrogens, interleukin 1 beta 2, interferons, and other signaling molecules before attaching to the uterine epithelium. The processes in the uterine endometrium in response to conceptus signaling are complex. Thus, the objective of this study was to characterize transcriptome changes in porcine endometrium during the time of conceptus attachment considering the specific localization in different endometrial cell types.

RESULTS

Low-input RNA-sequencing was conducted for the main endometrial compartments, luminal epithelium (LE), glandular epithelium (GE), blood vessels (BV), and stroma. Samples were isolated from endometria collected on Day 14 of pregnancy and the estrous cycle (each group n = 4) by laser capture microdissection. The expression of 12,000, 11,903, 11,094, and 11,933 genes was detectable in LE, GE, BV, and stroma, respectively. Differential expression analysis was performed between the pregnant and cyclic group for each cell type as well as for a corresponding dataset for complete endometrium tissue samples. The highest number of differentially expressed genes (DEGs) was found for LE (1410) compared to GE, BV, and stroma (800, 1216, and 384). For the complete tissue, 3262 DEGs were obtained. The DEGs were assigned to Gene Ontology (GO) terms to find overrepresented functional categories and pathways specific for the individual endometrial compartments. GO classification revealed that DEGs in LE were involved in 'biosynthetic processes', 'related to ion transport', and 'apoptotic processes', whereas 'cell migration', 'cell growth', 'signaling', and 'metabolic/biosynthetic processes' categories were enriched for GE. For blood vessels, categories such as 'focal adhesion', 'actin cytoskeleton', 'cell junction', 'cell differentiation and development' were found as overrepresented, while for stromal samples, most DEGs were assigned to 'extracellular matrix', 'gap junction', and 'ER to Golgi vesicles'.

CONCLUSIONS

The localization of differential gene expression to different endometrial cell types provided a significantly improved view on the regulation of biological processes involved in conceptus implantation, such as the control of uterine fluid secretion, trophoblast attachment, growth regulation by Wnt signaling and other signaling pathways, as well as the modulation of the maternal immune system.

Transcriptome analysis of the endometrium from Chinese Erhualian sows that differ in calcium ion concentration and litter size

Embryonic survival rate, an important factor in the fecundity of sows, is affected by endometrium-secreting histotroph. A higher concentration of calcium ion has been observed in the uterus of highly prolific Erhualian sows (EH) compared with those of less prolific (EL) sows. This suggests that EH sows have better establishment and maintenance of pregnancies, thus increasing embryonic survival rate during the peri-implantation period. To understand the mechanisms of how the endometrium-secreting histotroph affects embryonic survival rate during the Erhualian peri-implantation period, the expression patterns of endometrial mRNA in the EH and EL sows on day 12 of gestation were analyzed using RNA sequencing technology. A total of 164 differentially expressed genes (DEGs) were identified (P_adj  < 0.05, |log₂ (FC)| ≥ 1), including 46 upregulated and 118 downregulated genes in EH compared to EL. Gene Ontology enrichment indicated that a subset of DEGs was involved in calcium ion binding and cell adhesion. Solute carrier family 8 member A3 and solute carrier family 24 member 4, identified as upregulated genes (P_adj  < 0.05) in EH, were considered key candidate genes expressed in the endometrium affecting embryonic survival rate during the peri-implantation period. The results improve understanding of the genetic mechanism underlying the variation in litter size of Erhualian pigs during the peri-implantation period.

Comparative serum proteome analysis reveals potential early pregnancy-specific protein biomarkers in pigs

In this study, the comparative serum proteome profile of Day 5, 12 and 16 of gestation, representing three early embryonic events, namely formation, elongation and implantation of blastocysts, and non-pregnant control were explored by a label-free quantitation-based mass spectrometric approach to identify early pregnancy biomarkers in pigs. A total of 131 proteins were identified with respect to different groups, out of which 105 were found to be differentially expressed proteins (DEPs). Among the DEPs, 54 and 66 proteins were found to be up and downregulated respectively in early pregnancy groups (fold change &gt;2) and the maximum number of upregulated proteins was observed in the Day 12 pregnancy stage. Functional classification and pathway analysis of the DEPs revealed involvement of most of the proteins in complement and coagulation cascades, metabolic processes and immune and inflammatory responses. Proteins such as glutathione peroxidise (GPX), pregnancy zone protein (PZP), thrombospondin-1 (THBS1), α-1-antitrypsin (AAT) and mannose-binding lectin C (MBLC) were differentially expressed during early pregnancy and actively involved in different pregnancy-related activities. To the best of our knowledge, this is the first report on comparative serum protein profiling of different early pregnancy stages in pigs and our results provide a set of proteins that can be used as potential biomarkers for early pregnancy diagnosis in pigs.

Rumen-protected B vitamin complex supplementation during the transition period and early lactation alters endometrium mRNA expression on day 14 of gestation in lactating dairy cows

Greater metabolic demands in high-producing dairy cows are believed to be a cause of sub-fertility in these animals. Previously, supplementation with vitamin B complex molecules has shown benefits in improving milk production, health, and reproductive efficiency of dairy cows. The primary aim of this project was to determine the effects of rumen-protected vitamin B complex supplementation of 100 g of Transition VB (Jefo, St. Hyacinthe, QC, Canada) and 4 g of Lactation VB (VB; Jefo), during the transition and early lactation periods, respectively, compared with a control diet containing no supplementation on d 14 endometrial outcomes of pregnancy. In the vitamin B supplemented cows, we expect to see a change in the mark-up of endometrial genes important for embryo survival before implantation. Multiparous Holstein cows were enrolled into the study 3 wk before parturition and were randomly assigned to either the VB or control treatment. Twice-a-week blood samples, weekly milk samples, and daily feed intake were collected. Cows were enrolled onto a double-ovsynch protocol at 33 ± 3 d postpartum and inseminated by timed artificial insemination. Milk production and components, concentrations of BHB, haptoglobin, and progesterone in serum, and ovarian dynamics were also measured, but no treatment effect was observed. The uterus was flushed on d 14 after artificial insemination (around 72 DIM) for conceptus collection, and endometrial samples were collected at the same time. Overall, 42 cows were flushed and 13 embryos were collected. Analysis of mRNA expression of genes related to embryo development, immune system, adhesion, and regulation of vitamin B molecules showed that OXTR, MUC5B, MUC1, IL1B, SPP, TRD, FZD8, and FOLR1 genes were significantly upregulated in the VB group. Vitamin B supplementation had no effect on the size of the embryo and ovulatory follicle or corpus luteum diameter at embryo collection. In conclusion, the benefits of strategic dietary VB supplementation during the transition and early lactation might be directly linked to endometrial functions required for embryo survival during the peri-implantation period.

Transcriptomic analysis of the oviduct of pigs during the peri-conceptional period

The optimal environment in the oviduct is created by adjusting its ultrastructure and secretory capacity to protect gametes and embryos. It was hypothesized that direct contact between the isthmic epithelium and 2- and 4-cell-stage embryos would alter the transcriptomic profile of the isthmus in pigs. Microarray analysis was performed to determine the alterations in gene expression of the isthmus on Days 2-3 of pregnancy in pigs (after natural mating) during embryo presence in the oviduct. Of 43,803 microarray probes, 354 (0.81%) transcripts were altered (P-value ≤ 0.05 and fold-change ≥ 1.2) on the days of pregnancy when assessments were made. Of these 354 transcripts, 118 (33.3%) were up-regulated, and 236 (66.7%) were down-regulated. A total of 57 (48.3%) up-regulated and 73 down-regulated (30.9%) transcripts were classified into gene ontology categories. Of the 354 altered genes, 36 (10.2%) were categorized into the Toll-like or NOD-like receptor signaling pathway, in the immune system subcategory. Selected genes engaged in maternal immune function were down-regulated. The up-regulated genes were involved in epigenetic regulation, the protection of embryos against oxidative stress and xenobiotics and the control of estrogen metabolism. The 2- and 4-cell-stage embryos might, therefore, affect the oviductal transcriptome to optimize the intra-oviductal milieu, which is necessary to support proper development of embryos. The results of this study indicates the pig oviduct has the capacity to alter its transcriptomic profile as a result of early embryo development after natural mating.

Associations between fetal size, sex and both proliferation and apoptosis at the porcine feto-maternal interface

Introduction

Inadequate fetal growth has severe consequences for both neonatal and adult development. It is hypothesised that the feto-maternal interface associated with the lightest and male fetuses will undergo more apoptosis and less proliferation than those supplying the closest to mean litter weight (CTMLW) and female fetuses respectively.

Methods

Placental and endometrial samples associated with the lightest and CTMLW (gestational day (GD) 18 and 30), male and female (GD45, 60 and 90) Large White X Landrace conceptuses or fetuses were obtained. The mRNA expression of candidate genes involved in apoptosis or proliferation (BAX, BCL2, P53 and KI67) was quantified by qPCR. TUNEL staining was performed on placental samples supplying the lightest and CTMLW fetuses (GD45 and 60), of both sex (GD60).

Results

Placentas associated with the lightest fetuses had decreased P53 and KI67 expression compared to the CTMLW fetuses at GD45. At GD60, P53 expression was increased in placentas supplying the lightest compared to CTMLW fetuses. P53 expression was increased in endometrial samples associated with the lightest compared to the CTMLW fetuses at GD45. At GD30 and GD60 respectively, BAX expression was increased and BCL2, P53 and KI67 expression were decreased in endometrial samples associated with females compared to their male littermates. TUNEL staining revealed no association between fetal size or sex, and apoptotic cell number.

Discussion

This study has highlighted dynamic associations between fetal size, sex, and apoptosis and proliferation at the porcine feto-maternal interface. Further studies should be performed to improve the understanding of the mechanisms behind these findings.

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Gestational day influence feto-maternal interface apoptotic mRNA expression.

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Fetal size is associated with feto-maternal interface apoptotic mRNA expression.

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Sexual dimorphism exists in feto-maternal interface apoptotic mRNA expression.

Leukemia inhibitory factor and its receptor: expression and regulation in the porcine endometrium throughout the estrous cycle and pregnancy

Objective

Leukemia inhibitory factor (LIF) binds to a heterodimeric receptor composed of LIF receptor (LIFR) and glycoprotein 130 (GP130) to transmit signals into the cell. LIF plays an important role in reproduction by regulating immune response, decidualization, and implantation in several species. However, the expression of LIF and LIFR in the endometrium throughout the estrous cycle and pregnancy in pigs is not fully understood.

Methods

We analyzed the expression of LIF and LIFR in the endometrium on days 0 (estrus), 3, 6, 9, 12, 15, and 18 of the estrous cycle, and days 12, 15, 30, 60, 90, and 114 of pregnancy, in conceptuses on days 12 and 15, and in chorioallantoic tissues on days 30, 60, 90, and 114 of pregnancy in pigs. We also determined the effects of estrogen and progesterone on the expression of LIF and LIFR in endometrial tissues.

Results

The expression of LIF increased in the endometrium during the late diestrus phase of the estrous cycle and during mid- to late- pregnancy, while the expression of LIFR increased during early pregnancy. The expression of LIF was induced by increasing doses of estrogen, whereas the expression of LIFR was induced by increasing doses of progesterone.

Conclusion

These results indicate that the expression of LIF and its receptor LIFR in the endometrium is regulated in a stage-specific manner during the estrous cycle and pregnancy, suggesting that LIF and its receptor signaling system may play critical roles in regulating endometrial function in pigs.

Cell type-specific analysis of transcriptome changes in the porcine endometrium on Day 12 of pregnancy

BACKGROUND

Along with trophoblast elongation (Days 10 to 12), estradiol is secreted in increasing amounts for recognition of pregnancy. Endometrial secretions driven by ovarian progesterone and conceptus signals are essential for conceptus growth and development. Results of transcriptome analyses of whole endometrial tissue samples in the pig indicated the need for cell type-specific endometrial gene expression analysis for a better understanding of transcriptome changes associated with establishment of pregnancy.

RESULTS

The most distinct transcriptome profile and the majority of differentially expressed genes (DEGs) were identified in luminal epithelium (LE). Many DEGs were found only in the cell type-specific analysis. The functional classification of DEGs identified in specific endometrial cell types revealed various distinct functions and pathways. Genes related to immune activation, estrogen signaling pathway, embryo development, and cell proliferation were upregulated in LE of pregnant gilts. Genes involved in sterol biosynthetic and metabolic processes and extracellular matrix were upregulated in stroma. Genes associated with cell communication such as via exosomes and vesicles were found as differential in LE, glandular epithelium (GE), and stroma (S).

CONCLUSIONS

This study revealed that conceptus signals induce different transcriptomic regulations in the endometrial compartments/cell types related to their specific function during recognition and establishment of pregnancy.

Immunohistochemical determination of Ang-1, Ang-2 and Tie-2 in placentas of sows at 30, 60 and 114 days of gestation and validation through a bioinformatic approach

Angiopoietins (Ang-1, Ang-2) participate in vascular development and placental growth, both bind to Tie-2. This study aimed to determine the localization of angiopoietins in placental development of sows by immunohistochemistry and to validate the gene expression during gestation through a bioinformatic approach. Samples were collected from fifteen maternal-fetal interface from approximately 30 (n = 5), 60 (n = 5) and 114 (n = 5) days of gestation for immunohistochemistry. A bioinformatic approach was performed by re-analysis of public datasets to determine the increase or decrease of genes involved in angiogenesis during pregnancy. There was no significant statistical difference of Ang-1 during gestation, although there was a tendency to increase from mid- to term-gestation (P = 0.7680). A notable decrease of Ang-2 was observed from early- to term-pregnancy (P ≤ 0.05), consistent with the gene expression determined through bioinformatics. Furthermore, there were greater abundances of Tie-2 at both early and at term periods, but lesser abundances at mid-gestation (P ≤ 0.05). The bioinformatics approach indicated that genes related to biological processes such as angiogenesis (i.e., development and morphogenesis of blood vessels) were expressed to a greater extent in early gestation as compared with later in gestation. The Ang-1 gene expression related to cell maturation, response to hypoxia and apoptosis, however, increased as gestation period advanced. In conclusion, angiopoietins may have an important role in the vascular development thus ensuring adequate placental growth in sows. The presence of angiopoietins in the trophoblast suggests a specific role for these pro-angiogenic factors in the tissue formation at the maternal-fetal interface.

Regulation of the porcine corpus luteum during pregnancy

The new corpora lutea (CLs) in pigs are formed from the preovulatory follicles after the luteinizing hormone (LH) surge. However, total autonomy and independence of CLs from LH up to Day 12 of cycle has recently been questioned. Transformation of estrous cycle CL to CL of pregnancy initiated by embryonic signals requires not only the cessation of prostaglandin F2 (PGF_2α) supply to the luteal tissue but also needs the CL to overcome luteolytic acquisition and/or changing its sensitivity to PGF_2α during Days 12-14 of pregnancy. The luteolytic cascade is prevented by inhibition of lymphocyte infiltration and leucocyte recruitment, limitation of cell apoptosis, upregulation of pregnancy-associated genes and an enhanced antiluteolytic role of PGE₂ Our 'two-signal switch hypothesis' highlights the importance of post PGF_2α and PGE₂ receptor signaling pathways activation in CLs during luteolysis and rescue. The 'luteolytic switch' involves increased expression of many regression mediators and activation of the post PTGFR signaling pathway. The 'rescue switch' initiated by embryonic signals - estradiol 17β and PGE₂ - induces post PTGER2/4 pathway, turning the 'luteolytic switch' off and triggering activity of genes responsible for CL maintenance. In mid and late pregnancy, CLs are maintained by LH and the synergistic action of metabolic hormones. This paper provides an outline of recent views on CL regression, rescue and maintenance during pregnancy in pigs that conflict with previous paradigms and highlights new findings regarding the actions of prostaglandins, role of microRNAs (miRNA) and immune system and signaling pathways governing the life cycle of porcine CL.

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

BACKGROUND

Repeat 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.

METHODS

The 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.

RESULTS

Microarray 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.

CONCLUSION

The 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.

Preattachment Embryos of Domestic Animals: Insights into Development and Paracrine Secretions

In mammalian species, endometrial receptivity is driven by maternal factors independently of embryo signals. When pregnancy initiates, paracrine secretions of the preattachment embryo are essential both for maternal recognition and endometrium preparation for implantation and for coordinating development of embryonic and extraembryonic tissues of the conceptus. This review mainly focuses on domestic large animal species. We first illustrate the major steps of preattachment embryo development, including elongation in bovine, ovine, porcine, and equine species. We next highlight conceptus secretions that are involved in the communication between extraembryonic and embryonic tissues, as well as between the conceptus and the endometrium. Finally, we introduce experimental data demonstrating the intimate connection between conceptus secretions and endometrial activity and how adverse events perturbing this interplay may affect the progression of implantation that will subsequently impact pregnancy outcome, postnatal health, and expression of production traits in livestock offspring.

Analyses of Long Non-Coding RNA and mRNA profiling using RNA sequencing during the pre-implantation phases in pig endometrium

Establishment of implantation in pig is accompanied by a coordinated interaction between the maternal uterine endometrium and conceptus development. We investigated the expression profiles of endometrial tissue on Days 9, 12 and 15 of pregnancy and on Day 12 of non-pregnancy in Yorkshire, and performed a comprehensive analysis of long non-coding RNAs (lncRNAs) in endometrial tissue samples by using RNA sequencing. As a result, 2805 novel lncRNAs, 2,376 (301 lncRNA and 2075 mRNA) differentially expressed genes (DEGs) and 2149 novel transcripts were obtained by pairwise comparison. In agreement with previous reports, lncRNAs shared similar characteristics, such as shorter in length, lower in exon number, lower at expression level and less conserved than protein coding transcripts. Bioinformatics analysis showed that DEGs were involved in protein binding, cellular process, immune system process and enriched in focal adhesion, Jak-STAT, FoxO and MAPK signaling pathway. We also found that lncRNAs TCONS_01729386 and TCONS_01325501 may play a vital role in embryo pre-implantation. Furthermore, the expression of FGF7, NMB, COL5A3, S100A8 and PPP1R3D genes were significantly up-regulated at the time of maternal recognition of pregnancy (Day 12 of pregnancy). Our results first identified the characterization and expression profile of lncRNAs in pig endometrium during pre-implantation phases.

Transcriptomic Analysis of the Porcine Endometrium during Embryo Implantation

In pigs, successful embryo implantation is an important guarantee for producing litter size, and early embryonic loss occurring on day 12–30 of gestation critically affects the potential litter size. The implantation process is regulated by the expression of numerous genes, so comprehensive analysis of the endometrium is necessary. In this study, RNA sequencing (RNA-Seq) technology is used to analyze endometrial tissues during early pregnancy. We investigated the changes of gene expression between three stages (day 12, 18, and 25) by multiple comparisons. There were 1557, 8951, and 2345 differentially expressed genes (DEGs) revealed between the different periods of implantation. We selected several genes for validation by the use of quantitative real-time RT-PCR. Bioinformatic analysis of differentially expressed genes in the endometrium revealed a number of biological processes and pathways potentially involved in embryo implantation in the pig, most noticeably cell proliferation, regulation of immune response, interaction of cytokine-cytokine receptors, and cell adhesion. These results showed that specific gene expression patterns reflect the different functions of the endometrium in three stages (maternal recognition, conceptus attachment, and embryo implantation). This study identified comprehensive transcriptomic profile in the porcine endometrium and thus could be a foundation for targeted studies of genes and pathways potentially involved in abnormal endometrial receptivity and embryo loss in early pregnancy.

Transcriptome Analysis Revealed the Embryo-Induced Gene Expression Patterns in the Endometrium from Meishan and Yorkshire Pigs

The expression patterns in Meishan- and Yorkshire-derived endometrium during early (gestational day 15) and mid-gestation (gestational days 26 and 50) were investigated, respectively. Totally, 689 and 1649 annotated genes were identified to be differentially expressed in Meishan and Yorkshire endometrium during the three gestational stages, respectively. Hierarchical clustering analysis identified that, of the annotated differentially expressed genes (DEGs), 73 DEGs were unique to Meishan endometrium, 536 DEGs were unique to Yorkshire endometrium, and 228 DEGs were common in Meishan and Yorkshire endometriums. Subsequently, DEGs in each of the three types of expression patterns were grouped into four distinct categories according to the similarities in their temporal expression patterns. The expression patterns identified from the microarray analysis were validated by quantitative RT-PCR. The functional enrichment analysis revealed that the common DEGs were enriched in pathways of steroid metabolic process and regulation of retinoic acid receptor signaling. These unique DEGs in Meishan endometrium were involved in cell cycle and adherens junction. The DEGs unique to Yorkshire endometrium were associated with regulation of Rho protein signal transduction, maternal placenta development and cell proliferation. This study revealed the different gene expression patterns or pathways related to the endometrium remodeling in Meishan and Yorkshire pigs, respectively. These unique DEGs in either Meishan or Yorkshire endometriums may contribute to the divergence of the endometrium environment in the two pig breeds.

Oviductal Transcriptome Is Modified after Insemination during Spontaneous Ovulation in the Sow

Gene Expression Microarray technology was used to compare oviduct transcriptome between inseminated and non-inseminated pigs during spontaneous oestrus. We used an in vivo model approaching the study from a physiological point of view in which no hormonal treatment (animals were in natural oestrus) and no artificial sperm selection (selection was performed within the female genital) were imposed. It is therefore emphasised that no surgical introduction of spermatozoa and no insemination at a site other than the physiological one were used. This approach revealed 17 genes that were two-fold or more up-regulated in oviducts exposed to spermatozoa and/or developing embryos and 9 genes that were two-fold or more down-regulated. Functional analysis of the genes revealed that the top canonical pathways affected by insemination were related to the inflammatory response and immune system (Network 1) to molecular transport, protein trafficking and developmental disorder (Network 2) and to cell-to-cell signalling and interaction (Network 3). Some of the genes in network 1 had been previously detected in the oviduct of human and animals, where they were over-expressed in the presence of spermatozoa or pre-implantation embryos (C3, IGHG1, ITIH4, TNF and SERPINE1) whereas others were not previously reported (SAA2, ALOX12, CD1D and SPP1). Genes in Network 2 included RAB1B and TOR3A, the latter being described for the first time in the oviduct and clearly expressed in the epithelial cells of the mucosa layer. Network 3 integrated the genes with the highest down-regulation level (CYP51, PTH1R and TMOD3). Data in the present study indicate a change in gene expression during gamete encounter at the site of fertilization after a natural sperm selection within the female genital tract. These changes would indicate a modification of the environment preparing the oviduct for a successful fertilization and for an adequate embryo early development.

Proteomic analysis of porcine endometrial tissue during peri-implantation period reveals altered protein abundance

In mammals, successful pregnancy depends upon the readiness of uterus for implantation, followed by correct communication between the endometrium and the developing conceptus. The objective of this study was to elucidate changes in protein abundance associated with progression of estrous cycle and pregnancy from Day 9 to Day 12. We analyzed porcine endometrial tissue lysates by 2D-DIGE. Abundance of several proteins was altered depending upon the pregnancy status of animals. MALDI-TOF/TOF was used to identify a number of these proteins. Endometrial proteins that increased from Day 9 to Day 12 of cycle included annexin A4, beta-actin, apolipoprotein, ceruloplasmin and afamin. Changes in protein abundances associated with conceptus secreted factors, including haptoglobin, prolyl-4-hydroxylase, aldose-reductase and transthyretin, were also observed. Functional analysis revealed that endometrial proteins with altered abundance on Day 12 irrespective of the reproductive status were related to growth and remodeling, acute phase response and free radical scavenging, whereas transport and small molecule biochemistry were the functions activated in the pregnant endometrium as compared to the cyclic endometrium. These data provide information on dynamic physiological processes associated with uterine endometrial function of the cyclic and pregnant endometrium during period of maternal recognition of pregnancy in pigs and may potentially demonstrate a protein profile associated with successful pregnancy.

BIOLOGICAL SIGNIFICANCE

In pigs, the fertility rates are generally very high but the early embryonic loss that occurs during the second and third weeks of gestation critically affects the potential litter size. Temporal changes that take place in the uterine environment during the period of early pregnancy in pigs and a cross-talk between the uterus and the embryo play an important role in embryonic survival and successful pregnancy. A better understanding of the molecular changes associated with these processes will pave way for understanding of endometrial functions and help towards increasing embryo survival. In this study, we present a 2D-DIGE based analysis of changes in porcine endometrial proteome that are associated with progression of cycle and progression of pregnancy. The network analysis of the results clearly revealed the pathways that are involved in rendering the endometrium receptive to the presence of embryo and also the changes that are result of molecular communication between the endometrium and the conceptuses. This comprehensive identification of proteomic changes in the porcine endometrium could be a foundation for targeted studies of proteins and pathways potentially involved in abnormal endometrial receptivity, placentation and embryo loss.

Comparative analysis between endometrial proteomes of pregnant and non-pregnant ewes during the peri-implantation period

BACKGROUND

Early pregnancy failure has a profound impact on both human reproductive health and animal production. 2/3 pregnancy failures occur during the peri-implantation period; however, the underlying mechanism(s) remains unclear. Well-organized modification of the endometrium to a receptive state is critical to establish pregnancy. Aberrant endometrial modification during implantation is thought to be largely responsible for early pregnancy loss.

RESULT

In this study, using well-managed recipient ewes that received embryo transfer as model, we compared the endometrial proteome between pregnant and non-pregnant ewes during implantation period. After embryo transfer, recipients were assigned as pregnant or non-pregnant ewes according to the presence or absence of an elongated conceptus at Day 17 of pregnancy. By comparing the endometrial proteomic profiles between pregnant and non-pregnant ewes, we identified 94 and 257 differentially expressed proteins (DEPs) in the endometrial caruncular and intercaruncular areas, respectively. Functional analysis showed that the DEPs were mainly associated with immune response, nutrient transport and utilization, as well as proteasome-mediated proteolysis.

CONCLUSION

These analysis imply that dysfunction of these biological processes or pathways of DEP in the endometrium is highly associated with early pregnancy loss. In addition, many proteins that are essential for the establishment of pregnancy showed dysregulation in the endometrium of non-pregnant ewes. These proteins, as potential candidates, may contribute to early pregnancy loss.

Soy isoflavones improves endometrial barrier through tight junction gene expression

Contamination with bacterial endotoxin causes the disruption of the tight junction (TJ) barrier. We investigated the ameliorative effect of dietary flavonoids genistein (Ge) and daidzein (Di) in normal or lipopolysaccharide (LPS)-induced disruption of epithelial barrier function of the endometrium. Using the immortalized porcine glandular endometrial epithelial cells (PEG), transepithelial electrical resistance (TER) and FITC-dextran flux (FD-4) across the monolayer were measured. The mRNA expression of TJ proteins, zona occludens-1 (ZO1), and claudin-1, -3, -4, -7 and -8 was evaluated by real-time RT-PCR for coinciding effect of Ge or Di occurred at the gene transcription level. The results revealed that Ge and Di altered the TER, depending on times and concentrations. Low concentration (10−10 M) of both compounds decreased the TER, whereas higher concentrations (10−8and 10−6 M) increased the TER which was not related to the FD-4 flux. The increased TER by Ge or Di was parallel to the induction ofclaudin-3and-4or-8mRNA expression respectively. With LPS inoculation, all isoflavone treatments inhibited the decreased TER induced by LPS, but only Ge (10−8or 10−6 M) or Di (10−10or 10−6 M) was coincidence with the decreased FD-4 flux. Under this LPS-stimulated condition, some or all examined TJ gene expressions appeared to be promoted by specific concentration of Ge or Di respectively. Our findings suggest that the soy isoflavones treatment could promote and restore the impaired endometrial barrier function caused by LPS contamination.

Comparative transcriptome analysis reveals early pregnancy-specific genes expressed in peripheral blood of pregnant sows

Early and accurate diagnosis of pregnancy is important for effective management of an economical pig farm. Besides the currently available methods used in early diagnosis of sows, circulating nucleic acids in peripheral blood may contain some early pregnancy-specific molecular markers. For the first time, microarray analysis of peripheral blood from pregnant sows versus non-pregnant sows identified 127 up-regulated and 56 down-regulated genes at day 14 post-insemination. Gene Ontology annotation grouped the total differently expressed genes into 3 significantly enriched terms, cell surface receptor linked signal transduction, G-protein coupled receptor protein signaling pathway and regulation of vesicle-mediated transport. Signaling pathway analysis revealed the only one significantly changed pathway was arachidonic acid metabolism. Of the differently expressed genes, nine (including LPAR3, RXFP4, GALP, CBR1, CBR2, GPX6, USP18, LHB and NR5A1) were found to exert function related to early pregnancy processes. This study provides a clue that differentially abundant RNAs in maternal peripheral blood can help to identify the molecular markers of early pregnancy in pigs.

Biochemical and protein profile of alpaca (Vicugna pacos) uterine horn fluid during early pregnancy

South American camelids show high embryo loss rate, during the first 60 days of pregnancy. One of the factors which may be related to this situation is that over 98% of the embryos implant in the left uterine horn (LUH) even though both ovaries contribute similarly to ovulation. There is scarce information about the uterine environment of female camelids at any physiological state that could explain the capability of the LUH to attract the embryo and maintain pregnancy. We describe, for the first time, the biochemical and protein profile of uterine fluid (UF), addressing the right and LUH environment in non-pregnant and pregnant alpacas. Different substrates, electrolytes and metabolites were assayed in both uterine horn fluids. Small changes were observed in glucose and total protein levels, which were more noticeable during pregnancy. In addition, 10 specific proteins were found in the left horn fluid in 5-week-pregnant alpacas, and two protein bands were identified in non-pregnant alpaca right horn fluid. These results would provide basic information for identification of possible markers for pregnancy diagnosis, reproductive diseases and hormone-treated animals evaluation and hence contributing to improve the pregnancy rate.

Cytokines from the pig conceptus: roles in conceptus development in pigs

Establishment of pregnancy in pigs involves maintaining progesterone secretion from the corpora lutea in addition to regulating a sensitive interplay between the maternal immune system and attachment of the rapidly expanding trophoblast for nutrient absorption. The peri-implantation period of rapid trophoblastic elongation followed by attachment to the maternal uterine endometrium is critical for establishing a sufficient placental-uterine interface for subsequent nutrient transport for fetal survival to term, but is also marked by the required conceptus release of factors involved with stimulating uterine secretion of histotroph and modulation of the maternal immune system. Many endometrial genes activated by the conceptus secretory factors stimulate a tightly controlled proinflammatory response within the uterus. A number of the cytokines released by the elongating conceptuses stimulate inducible transcription factors such as nuclear factor kappa B (NFKB) potentially regulating the maternal uterine proinflammatory and immune response. This review will establish the current knowledge for the role of conceptus cytokine production and release in early development and establishment of pregnancy in the pig.