Novel pathways for implantation and establishment and maintenance of pregnancy in mammals

Dietary supplementation of l-arginine and chromium picolinate in sows during gestation affects the muscle fibre characteristics but not the performance of their progeny

BACKGROUND

The present study investigated the effects of dietary supplementation of l-arginine and chromium picolinate (CrP) in sows during gestation on muscle fibre characteristics, performance and carcass characteristics of their progeny. Sixty healthy sows were randomly divided into four groups as a 2 × 2 factorial experiment design: one group received the control diet, another received the control diet + 10 g kg^-1 l-arginine, the third group received the control diet + 400 ppb CrP, and the fourth group received the control diet + 10 g kg^-1 l-arginine and 400 ppb CrP.

RESULTS

The results showed that sows fed the diet supplemented with CrP produced progeny with higher muscle fibre numbers at birth, weaning and slaughter compared to sows fed the control diet. For mean fibre areas, the same result was found at weaning. For progeny of sows fed diets supplemented with l-arginine, only higher muscle fibre numbers at slaughter was observed. Almost no differences were observed regarding average daily gains, average daily feed intake, gain-to-feed ratios, carcass and meat traits.

CONCLUSION

The results of the present study indicate that dietary supplementation of l-arginine and particularly CrP in sows during gestation alters muscle fibre numbers in their offspring, although not their performance or carcass characteristics. © 2017 Society of Chemical Industry.

Pairing ultrasonography with endocrinology to elucidate underlying mechanisms of successful pregnancy in the northern fur seal (Callorhinus ursinus)

Reproductive success is one of the central tenets of conservation management programs, yet the inability to study underlying physiological processes in a minimally-invasive manner and the unpredictable nature of wild animal populations leaves large gaps in our knowledge of factors critical to successful reproduction in wild species. This study integrated ultrasonography of the reproductive tract and analysis of reproductive hormones in 172 northern fur seals (Callorhinus ursinus) to identify intrinsic factors associated with reinitiating embryonic growth at the end of diapause. Within the first 3-4 weeks of active gestation, pregnant fur seals (n = 126) had a larger corpus luteum and fewer antral follicles than non-pregnant fur seals, or those still in diapause (n = 46). This suggests that the conceptus drives changes in ovarian status to convey its presence to the female. Morphological changes in the reproductive tract associated with pregnancy were not reflected in differences in endocrine profiles (estradiol, estrone, progesterone, and relaxin) between pregnant and non-pregnant individuals. Hormone concentrations correlated more strongly with calendar date than with the presence or size of the conceptus, demonstrating that none of these reproductive hormones were reliable markers for early pregnancy diagnosis. Instead, the northern fur seal's long diestrus may serve to reduce the probability of a temporal mismatch between corpus luteum regression and embryo implantation. Indeed, conception rates were high and confirmed rates of pregnancy loss were relatively low (11%). In this study, minimally-invasive ultrasonography was used in wild pinnipeds to detect very early pregnancy (embryonic vesicles >2 mm) in combination with ovarian and endocrine dynamics at the time of embryo implantation, shedding light on mechanisms for maternal recognition of pregnancy. This study is also the first to track whether these same animals carried the embryo to term, by observing fur seals during the birthing season the following year. Data do not support the notion that decreased pregnancy rates or higher pregnancy loss rates are major contributing factors to the northern fur seal's population decline.

Maternal metabolism affects endometrial expression of oxidative stress and FOXL2 genes in cattle

Intensive selection for milk production has led to reduced reproductive efficiency in high-producing dairy cattle. The impact of intensive milk production on oocyte quality as well as early embryo development has been established but few analyses have addressed this question at the initiation of implantation, a critical milestone ensuring a successful pregnancy and normal post-natal development. Our study aimed to determine if contrasted maternal metabolism affects the previously described sensory properties of the endometrium to the conceptus in cattle. Following embryo transfer at Day 7 post-oestrus, endometrial caruncular (CAR) and intercaruncular (ICAR) areas were collected at Day 19 from primiparous postpartum Holstein-Friesian cows that were dried-off immediately after parturition (i.e., never milked; DRY) or milked twice daily (LACT). Gene quantification indicated no significant impact of lactation on endometrial expression of transcripts previously reported as conceptus-regulated (PLET1, PTGS2, SOCS6) and interferon-tau stimulated (RSAD2, SOCS1, SOCS3, STAT1) factors or known as female hormone-regulated genes (FOXL2, SCARA5, PTGS2). Compared with LACT cows, DRY cows exhibited mRNA levels with increased expression for FOXL2 transcription factor and decreased expression for oxidative stress-related genes (CAT, SOD1, SOD2). In vivo and in vitro experiments highlighted that neither interferon-tau nor FOXL2 were involved in transcriptional regulation of CAT, SOD1 and SOD2. In addition, our data showed that variations in maternal metabolism had a higher impact on gene expression in ICAR areas. Collectively, our findings prompt the need to fully understand the extent to which modifications in endometrial physiology drive the trajectory of conceptus development from implantation onwards when maternal metabolism is altered.

Functional roles of agmatinase during the peri-implantation period of pregnancy in sheep

This study investigated the effect of agmatine (Agm) in proliferation of ovine trophecdoderm cells (oTr1) as well as the importance of the arginine decarboxylase (ADC) and agmatinase (AGMAT) alternative pathway for synthesis of polyamines in ovine conceptuses during the peri-implantation period of pregnancy. Morpholino antisense oligonucleotides (MAOs) were used to inhibit translation of mRNAs for ODC1 alone, AGMAT alone, and their combination. Rambouillet ewes (N = 50) were assigned randomly to the following treatments on Day 8 of pregnancy: MAO control (n = 10); MAO-ODC1 (n = 8); MAO-ADC (n = 6); MAO-ODC1:MAO-ADC (n = 9); or MAO-ODC1:MAO-AGMAT (n = 9). Ewes were ovario-hysterectomized on Day 16 of pregnancy to obtain uterine flushings, uterine endometrium, and conceptus tissues. Inhibition of translation of both ODC1 and AGMAT resulted in 22% of ewes having morphologically and functionally normal (elongated and healthy) conceptuses designated MAO-ODC1:MAO-AGMAT (A). But, 78% of the MAO-ODC1:MAO-AGMAT ewes had morphologically and functionally abnormal (not elongated and fragmented) conceptuses designated MAO-ODC1:MAO-AGMAT (B). The pregnancy rate was less (22%; P < 0.05) for MAO-ODC1:MAO-AGMAT ewes than for MAO-control (80%), MAO-ODC1 (75%), MAO-ADC (84%), and MAO-ODC1:MAO-ADC (44%) ewes. Moreover, inhibition of translational of both ODC1 and AGMAT mRNAs increased expression of ADC, SLC22A1, SLC22A2, and SLC22A3 mRNAs, as well as abundances of agmatine, putrescine, spermindine, and spermine in conceptus tissue. However, MAO-ODC1:AGMAT(B) ewes had greater abundances of agmatine, putrescine, and spermidine and reduced amounts of spermine in uterine flushes. Thus, in vivo knockdown of translation of ODC1 and AGMAT mRNAs increased expression of genes for the synthesis and transport of polyamines in ovine conceptuses during the peri-implantation period of pregnancy.

Differential expression and functional roles of chemokine (C-C motif) ligand 23 and its receptor chemokine (C-C motif) receptor type 1 in the uterine endometrium during early pregnancy in pigs

Many chemokines expressed by cells of the uterine endometrium of mammals are involved in cell-cell interactions. However, little is known about expression and functional roles of chemokine (C-C motif) ligand 23 (CCL23) in the uterine endometrium. Results of this study demonstrated that CCL23 and its receptor, chemokine (C-C motif) receptor type 1 (CCR1), are up-regulated in porcine endometria during pregnancy. CCL23 and CCR1 mRNAs were strongly expressed in endometrial glandular (GE) and luminal (LE) epithelial cells. Treatment of porcine uterine luminal epithelial (pLE) cells with recombinant CCL23 increased the abundances of PCNA and cyclin D1, and enhanced proliferation and cell cycle progression in pLE cells. CCL23 also stimulated phosphorylation of cell signaling molecules including AKT and MAPKs in pLE cells. Furthermore, ER stress-related molecules were reduced by CCL23. These results suggest that CCL23-CCR1 signaling is important for endometrial development and establishment of pregnancy in pigs.

TGFβ superfamily signaling and uterine decidualization

Decidualization is an intricate biological process where extensive morphological, functional, and genetic changes take place in endometrial stromal cells to support the development of an implanting blastocyst. Deficiencies in decidualization are associated with pregnancy complications and reproductive diseases. Decidualization is coordinately regulated by steroid hormones, growth factors, and molecular and epigenetic mechanisms. Transforming growth factor β (TGFβ) superfamily signaling regulates multifaceted reproductive processes. However, the role of TGFβ signaling in uterine decidualization is poorly understood. Recent studies using the Cre-LoxP strategy have shed new light on the critical role of TGFβ signaling machinery in uterine decidualization. Herein, we focus on reviewing exciting findings from studies using both mouse genetics and in vitro cultured human endometrial stromal cells. We also delve into emerging mechanisms that underlie decidualization, such as non-coding RNAs and epigenetic modifications. We envision that future studies aimed at defining the interrelationship among TGFβ signaling circuitries and their potential interactions with epigenetic modifications/non-coding RNAs during uterine decidualization will open new avenues to treat pregnancy complications associated with decidualization deficiencies.

MicroRNA Signaling in Embryo Development

Expression of microRNAs (miRNAs) is essential for embryonic development and serves important roles in gametogenesis. miRNAs are secreted into the extracellular environment by the embryo during the preimplantation stage of development. Several cell types secrete miRNAs into biological fluids in the extracellular environment. These fluid-derived miRNAs have been shown to circulate the body. Stable transport is dependent on proper packaging of the miRNAs into extracellular vesicles (EVs), including exosomes. These vesicles, which also contain RNA, DNA and proteins, are on the forefront of research on cell-to-cell communication. Interestingly, EVs have been identified in many reproductive fluids, such as uterine fluid, where their miRNA content is proposed to serve as a mechanism of crosstalk between the mother and conceptus. Here, we review the role of miRNAs in molecular signaling and discuss their transport during early embryo development and implantation.

The developmental transcriptome landscape of receptive endometrium during embryo implantation in dairy goats

Under natural conditions, some embryos cannot implant successfully because of the dysfunction of receptive endometrium (RE). Thus, it is imperative for us to study the molecular mechanisms involved in the formation of the RE from pre-receptive endometrium (PE). In this study, the endometrium from gestational day 5 (D5, PE) and gestational day 15 (D15, RE) dairy goats were selected to systematically analyze the transcriptome using strand-specific Ribo-Zero RNA-Seq, >120 million high-quality paired-end reads were generated and 47,616 transcripts were identified in the endometrium of dairy goats. A total of 810 mRNAs were differentially expressed genes (DEGs) between the RE and PE meeting the criteria of P-values<0.05. Bioinformatics analysis of the DEGs revealed that a number of biological processes and pathways were potentially involved in the establishment of the RE, notably energy metabolism and amino acid metabolism. Furthermore, we speculated that CXCL14, IGFBP3, and LGALS15 potentially participated in the development of endometrium. What's more, putative SNPs, InDels and AS events were identified and analyzed in the endometrium. In a word, this resulting view of the transcriptome greatly enhances the comprehensive transcript catalog and uncovers the global trends in gene expression during the formation of receptive endometrium in dairy goats.

The MMP-9/TIMP-1 System is Involved in Fluoride-Induced Reproductive Dysfunctions in Female Mice

A total of 84 healthy female mice were kept with various concentrations of sodium fluoride (F) (0, 50, 100, 150 mg F^-/L in drinking water for 90 days) and were then mated with healthy male mice for 1 week to study the effect of excessive fluoride on female reproductive function, particularly in embryo implantation. The rate of pregnancy, litter size, and the birth weight of female mice were evaluated. Ultrastructural changes of uteri tissues were observed by transmission electron microscopy (TEM). The mRNA expression levels of MMP-9 and TIMP-1 were determined by quantitative real-time PCR. The protein expression levels of MMP-9 and TIMP-1 were analyzed by western blotting. Results showed a significant decrease of litter size in mice exposed to fluoride. TEM images of uteri tissue of mice that underwent a 150 mg/L F^- treatment for 90 days showed a vague nucleus, reduced microvilli, increased lysosomes, a dilated endoplasmic reticulum, and a vacuolization mitochondrion when compared with the control group. Following the damage of the structure, the expression levels of MMP-9 and TIMP-1 in uteri tissues were significantly unregulated in the F 150 group. These results show that MMP-9/TIMP-1 system disturbance and changes of histological structure in uteri tissue are involved in fluoride-induced reproductive dysfunctions.

Brain-derived neurotrophic factor improves proliferation of endometrial epithelial cells by inhibition of endoplasmic reticulum stress during early pregnancy

Brain-derived neurotrophic factor (BDNF) is a member of the neurotrophin family binds to two transmembrane receptors; neurotrophic receptor tyrosine kinase 2 (NTRK2) with high affinity and p75 with low affinity. Although BDNF-NTRK2 signaling in the central nervous system is known, signaling in the female reproductive system is unknown. Therefore, we determined effects of BDNF on porcine endometrial luminal epithelial (pLE) cells isolated from Day 12 of pregnancy, as well as expression of BDNF and NTRK2 in endometria of cyclic and pregnant pigs. BDNF-NTRK2 genes were expressed in uterine glandular (GE) and luminal (LE) epithelia during early pregnancy. In addition, their expression in uterine GE and LE decreased with increasing parity of sows. Recombinant BDNF increased proliferation in pLE cells in a dose-dependent, as well as expression of PCNA and Cyclin D1 in nuclei of pLE cells. BDNF also activated phosphorylation of AKT, P70S6K, S6, ERK1/2, JNK, P38 proteins in pLE cells. In addition, cell death resulting from tunicamycin-induced ER stress was prevented when pLE cells were treated with the combination of tunicamycin and BDNF which also decreased cells in the Sub-G₁ phase of the cell cycle. Furthermore, tunicamycin-induced unfolded protein response genes were mostly down-regulated to the basal levels as compared to non-treated pLE cells. Our finding suggests that BDNF acts via NTRK2 to induce development of pLE cells for maintenance of implantation and pregnancy by activating cell signaling via the PI3K and MAPK pathways and by inhibiting ER stress.

Sexual Dimorphism of miRNAs Secreted by Bovine In vitro-produced Embryos

Sexual dimorphism of bovine blastocysts has previously been observed through differences in development, cell death, metabolism, telomere length, DNA methylation, and transcriptomics. However, dimorphism in the secretion of miRNAs to culture media has not yet been evaluated. The objectives of this study were to determine if sex-specific blastocyst miRNA secretion occurs and to further investigate the role these miRNAs may have in the interaction between a blastocyst and the maternal environment. In vitro embryo culture was performed and media from male and female blastocysts was collected into sex-specific pools. Profiling of 68 miRNAs revealed a total of eight miRNAs that were differentially expressed between female and male-conditioned media. Validation by qPCR confirmed higher expression of miR-22 (P < 0.05), miR-122 (P < 0.05), and miR-320a (P < 0.05) in female media for three additional biological replicates. To examine the potential roles of secreted miRNAs to the media in communication with the maternal environment, miR-22, miR-122, and miR-320a were each supplemented to four replicates of primary bovine endometrial epithelial cell culture. Uptake of miR-122 (P < 0.05) and miR-320a (P < 0.05) was detected, and a trend of uptake was detected for miR-22 (P > 0.05). Further, expression of the progesterone receptor transcript, a predicted target of all three miRNAs, was found to be upregulated in the cells following supplementation of miR-122 (P < 0.05) and miR-320a (P < 0.05), and a trend upregulation of the transcript was observed following miR-22 (P > 0.05) supplementation. This work demonstrates that male and female conceptuses are able to differentially secrete miRNAs at the blastocyst stage and that these miRNAs have the ability to induce a transcriptomic response when applied to maternal cells. This knowledge builds on the known dimorphic differences in conceptuses at the blastocyst stage and demonstrates a role for blastocyst-secreted miRNAs in cell-cell communication.

The effect of lysophosphatidic acid together with interferon tau on the global transcriptomic profile in bovine endometrial cells

In cows, lysophosphatidic acid (LPA), which acts in an auto/paracrine manner, serves as a luteotropic factor during early pregnancy by stimulating progesterone and prostaglandin E₂ secretion, thus protecting the bovine corpus luteum and early embryo development. Our hypothesis was that LPA exerted some local effects on the bovine endometrium prior to early embryo-maternal interactions and that interferon tau (IFNτ), the pregnancy recognition signal, modulated this action. In the present study, we applied an in vitro model involving whole-transcriptomic profiling to examine the effects of LPA on gene expression in bovine endometrial cells. Microarray analyses revealed 36, 269 and 284 differentially expressed transcripts in bovine endometrial cells in the control vs. LPA, control vs. LPA + IFNτ and LPA vs. LPA + IFNτ groups, respectively. The expression of matrix metalloproteinase 13 (MMP13) and radical S-adenosyl methionine domain containing 2 (RSAD2) was increased in the LPA-treated endometrial cells. Among the transcripts differentially regulated by LPA together with IFNτ, many of the genes were classical- or novel-type I IFN-stimulated genes (ISGs). The results indicated that 10 of the 16 analyzed genes showed a positive correlation with their corresponding microarray data upon real-time PCR validation, indicating a considerable consistency between both techniques. In summary, these transcriptional profiling studies identified a number of genes that were regulated by LPA alone and LPA together with IFNτ in endometrial cells from the bovine uterus. Available studies support the idea that LPA, which acts in an auto/paracrine manner on the endometrium, alters the expression of genes that are probably important for uterine receptivity, maternal immune tolerance to the embryo and conceptus growth and development during early pregnancy. Moreover, the differentially expressed genes (DEGs) that increased in the LPA + IFNτ-treated endometrial cells are largely in response to IFNτ actions and are possibly associated with crucial biological processes during the peri-implantation period of pregnancy.

Role of progesterone in embryo development in cattle

Progesterone (P4) from the corpus luteum is critical for the establishment and maintenance of pregnancy and plays a major role in regulating endometrial secretions essential for stimulating and mediating changes in conceptus growth and differentiation throughout early pregnancy in ruminants. Numerous studies have demonstrated an association between elevated systemic P4 and acceleration in conceptus elongation. A combination of in vivo and in vitro experiments found that the effects of P4 on conceptus elongation are indirect and mediated through P4-induced effects in the endometrium. Despite effects on elongation, data on the effects of post-insemination supplementation with P4 on pregnancy rates are conflicting. This review highlights the effects of P4 on conceptus development and examines strategies that have been undertaken to manipulate P4 concentrations to increase fertility.

Insights into conceptus elongation and establishment of pregnancy in ruminants

This review integrates established and new information on the factors and pathways regulating conceptus–endometrial interactions, conceptus elongation and establishment of pregnancy in sheep and cattle. Establishment of pregnancy in domestic ruminants begins at the conceptus stage (embryo or fetus and associated extra-embryonic membranes) and includes pregnancy recognition signalling, implantation and the onset of placentation. Survival and growth of the preimplantation blastocyst and elongating conceptus require embryotrophic factors (amino acids, carbohydrates, proteins, lipids and other substances) provided by the uterus. The coordinated and interactive actions of ovarian progesterone and conceptus-derived factors (interferon-τ and prostaglandins) regulate expression of elongation- and implantation-related genes in the endometrial epithelia that alter the uterine luminal milieu and affect trophectoderm proliferation, migration, attachment, differentiation and function. A comparison of sheep and cattle finds both conserved and non-conserved embryotrophic factors in the uterus; however, the overall biological pathways governing conceptus elongation and establishment of pregnancy are likely conserved. Given that most pregnancy losses in ruminants occur during the first month of pregnancy, increased knowledge is necessary to understand why and provide a basis for new strategies to improve pregnancy outcome and reproductive efficiency.

Low-level arginine supplementation (0.1%) of wheat-based diets in pregnancy increases the total and live-born litter sizes in gilts

The present study was conducted to test the effects of l-arginine supplementation of wheat-based diets on the pregnancy outcome of gilts. Pregnant gilts (Yorkshire × Landrace, n = 113) were assigned randomly into two groups representing dietary supplementation with 0.1% l-arginine as l-arginine-HCl or 0.17% l-alanine (isonitrogenous control) between Days 30 and 110 of pregnancy. Blood samples were obtained from the ear vein on Days 30, 70 and 90 of pregnancy. Compared with the control, arginine supplementation increased the total number of piglets born by 1.10 per litter and the number of live-born piglets by 1.10 per litter (P < 0.05). Plasma concentration of spermine was higher in gilts fed arginine diets than in those fed control diets at Day 90 of pregnancy (P < 0.05). Dietary arginine supplementation increased plasma concentration of IGF-I of gilts at Day 90 of pregnancy (P < 0.01) and plasma concentrations of arginine, proline and ornithine at Days 70 and 90 of pregnancy (P < 0.05). These results indicated that low-level supplementation (0.1%) of l-arginine–HCl of wheat-based diets beneficially enhances the reproductive performance of gilts and is feasible for use in commercial production.

Uterine and placental expression of HPGD in cows during pregnancy and release of fetal membranes

15-Hydroxyprostaglandin dehydrogenase (HPGD) plays a key role in prostaglandins (PGs) catabolism. Its expression and activity appear to be regulated by progesterone (P4). We investigated the HPGD mRNA-expression and protein localization in placentomes and interplacental uterine sites throughout gestation (Study I), and after fetal membranes retention (RFM) compared with normally delivered fetal membranes (DFM) (Study II). Furthermore, we analyzed the influence of aglepristone (AP), dexamethasone (GC) or cloprostenol (CP), on HPGD expression in bovine placentomes (Study III). Tissues from late gestation (D272) and at normal term (NT) served as controls. HPGD was highest in all sites at the beginning of pregnancy and at (NT). Following induced parturition HPGD was lower after (AP) and (GC) compared with (NT), and was similar in RFM and DFM. Placentomes stained primarily in fetal compartments; interplacentomal signals were observed in endometrial glandular and luminal epithelium. Results indicate that HPGD may play a role during establishment and termination of gestation.

Gestation-related gene expression and protein localization in endometrial tissue of Suffolk and Cheviot ewes at gestation Day 19, after transfer of Suffolk or Cheviot embryos

The objective of this study was to investigate the gene expression of progesterone and estrogen receptor α (PR, ERα), insulin-like growth factor (IGF) 1, IGF-2, their receptor (IGFR1), IGF-binding proteins (BP) 1 to 6, insulin receptor, adiponectin receptors (AdipoR1/2), cyclooxygenase 2 (PTGS2), mucin 1 and to localize PR, ERα, IGF-1, IGFR1, PTGS2, and proliferating cellular nuclear antigen (PCNA) in the endometrium of pregnant (Day 19) Suffolk and Cheviot ewes carrying Suffolk and Cheviot embryos transferred within and reciprocally between breeds. Gene expression was determined by real-time quantitative polymerase chain reaction (RT-qPCR), and antigen determination was measured by immunohistochemistry in the luminal epithelium (LE), superficial and deep glands (SG, DG, respectively) and superficial and deep stroma. Gene expression of PR, IGF-1, IGFBP2, and IGFBP5 was higher in Suffolk than that in Cheviot ewes (P < 0.05). Greater abundance of IGF-2 and IGBP3 expression was found in Cheviot ewes carrying Cheviot embryos than Cheviot ewes carrying Suffolk embryos (P < 0.05). No staining for PR and ERα was observed in the LE, very scarce staining in SG and DG, whereas positive staining was observed in both superficial and deep stroma. No differences were found for PR staining, but Cheviot ewes had higher ERα staining intensity than Suffolk ewes (P < 0.05). Positive staining for IGF-1 was observed in all cell types except DG, and staining of IGFR1 was observed in all cell types. No differences among groups in staining were found for IGF-1 or IGFR1 in any cell type. Positive staining of PTGS2 was observed in LE and SG in all groups. An interaction between ewe and embryo breed affected PTGS2 staining (P < 0.05), whereby Cheviot ewes carrying Suffolk embryos had a lower PTGS2 staining than Suffolk ewes carrying Suffolk embryos. Positive staining of PCNA was found in LE and SG. Suffolk ewes carrying Suffolk embryos showed lower PCNA immunostaining than Cheviot ewes carrying Suffolk embryos (P < 0.05), whereas no differences were observed in ewes carrying Cheviot embryos. This study showed that gestation-related protein expression in the endometrium of Suffolk and Cheviot ewes is affected by both ewe and embryo breed at Day 19 of pregnancy.

Naringenin-induced migration of embrynoic trophectoderm cells is mediated via PI3K/AKT and ERK1/2 MAPK signaling cascades

For successful pregnancy, a well-coordinated network of growth factors, nutrients and hormones is required for fetal-maternal interactions. Naringenin, as a weak phytoestrogen, improves diabetes, inflammation, neuronal diseases, cardiovascular diseases and cancers. However, the role of naringenin in migration mechanism(s) of peri-implantation conceptuses is unknown. Therefore, in the present study, we determined the effects of naringenin on migration of porcine trophectoderm (pTr) cells, which is a known in vitro model for research on trophectoderm cell biology and placental-fetal developmental biology, in order to assess intracellular signal transduction pathways activated by naringenin. Migration of pTr cells increased in a dose-dependent manner in response to naringenin. Also, naringenin activated the phosphorylation of AKT and ERK1/2 proteins in a dose-dependent manner and those proteins were abundant mainly in the cytoplasm of naringenin-treated pTr cells. Within 30 min after treatment with 20 μM naringenin, the abundance of phosphorylated EKR1/2, P70S6K, P90RSK and S6K proteins increased, and then returned to basal levels by 120 min whereas the abundance of AKT increased gradually to 120 min post-treatment. However, the phosphorylation of AKT, P70S6K, P90RSK and S6K was reduced in naringenin-induced pTr cells pre-treated with a PI3K inhibitor (LY294002). Also, a MEK1/2 inhibitor (U0126) significantly decreased naringenin-induced phosphorylation of ERK1/2, P70S6K and S6K proteins in pTr cells. Moreover, the naringenin-stimulated migration of pTr cells was suppressed by LY294002 and U0126. Collectively, results of the present study suggest that naringenin supports migration of pTr cells through PI3K/AKT and ERK1/2 MAPK signaling pathways crucial for orchestrating conceptus-uterine interactions.

Expression of genes involved in progesterone receptor paracrine signaling and their effect on litter size in pigs

Background

Embryonic mortality during the period of implantation strongly affects litter size in pigs. Progesterone receptor (PGR) paracrine signaling has been recognized to play a significant role in embryonic implantation. IHH, NR2F2, BMP2, FKBP4 and HAND2 were proved to involve in PGR paracrine signaling. The objective of this study was to evaluate the expression of IHH, NR2F2, BMP2, FKBP4 and HAND2 in endometrium of pregnant sows and to further investigate these genes’ effect on litter size in pigs. Real-time PCR, western blot and immunostaining were used to study target genes/proteins expression in endometrium in pigs. RFLP-PCR was used to detect single nucleotide polymorphisms (SNPs) of target genes.

Results

The results showed that the mRNA and protein expression levels of IHH, NR2F2 and BMP2 were up-regulated during implantation period (P < 0.05 or P < 0.01). All target proteins were mainly observed in luminal epithelium and glandular epithelium. Interestingly, the staining of NR2F2 and HAND2 was also strong in stroma. SNPs detection revealed that there was a -204C > A mutation in promoter region of NR2F2 gene. Three genotypes were found in Large White, Landrace and Duroc sows. A total of 1847 litter records from 625 sows genotyped at NR2F2 gene were used to analyze the total number born (TNB) and number born alive (NBA). The study of the effect on litter size suggested that sows with genotype CC tend to have higher litter size.

Conclusions

These results showed the expression patterns of genes/proteins involved in PGR paracrine signaling over implantation time. And the candidate gene for litter size was identified from genes involved in this signaling. This study could be a resource for further studies to identify the roles of these genes for embryonic implantation in pigs.

Electronic supplementary material

The online version of this article (doi:10.1186/s40104-016-0090-z) contains supplementary material, which is available to authorized users.

Expression of genes associated with luteolysis in peripheral blood mononuclear cells during early pregnancy in cattle

The conceptus-derived signals that initiate maternal recognition of pregnancy act primarily on the endometrium to inhibit the development of luteolysis, thus modifying the expression of genes in the corpus luteum. The involvement of peripheral blood mononuclear cells (PBMCs) in the formation of this anti-luteolytic mechanism during early pregnancy is uncertain. In this study, PBMCs from non-pregnant and early-pregnant cows were sampled to explore the expression of genes associated with luteolysis, including AKR1B1 (aldo-keto reductase family 1, member B1; a bovine prostaglandin F synthase), PTGFR (PGF2α receptor), OXT (oxytocin), PTGES (PGE synthase), PTGER1 (PGE2 receptor 1), and PGR (progesterone receptor). OXT and PTGFR transcript abundance was low in PBMCs at Day 18 in pregnant individuals. PGR and PTGER1 mRNA abundance was significantly higher at Day 30 in pregnant individuals. AKR1B1 and PTGES transcript abundance was significantly higher at Day 18 in PBMCs from non-pregnant individuals, yet AKR1B1 and PTGES protein abundance was elevated at Day 30 in pregnant individuals-although AKR1B1 dimer may be significantly higher at Day 18 in non-pregnant PBMCs. In conclusion, changes in bovine PBMC gene expression are associated with luteolysis during early pregnancy, which implicate the influence of circulating blood components in controlling luteolysis. Mol. Reprod. Dev. 83: 509-515, 2016. © 2016 Wiley Periodicals, Inc.

Endoglin (CD105) coordinates the process of endometrial receptivity for embryo implantation

Endoglin is a TGF-β receptor that is expressed in uterine endothelial and stromal cells in addition to trophoblast expression. However, the functional importance of endoglin in the embryo implantation process is not clear. We observed endoglin expression in the endometrium throughout the stages of its receptivity; however, its expression was enhanced during the receptive stage. Endoglin expression was predominant in epithelial cells of the lumen and glands, but showed a milder expression in stromal cells. Endoglin expression was initially observed in the primary decidual zone and later extended to the secondary decidua zone. Knockdown of endoglin via siRNA reduced the implantation sites along with the blastocyst numbers. Mouse blastocyst with endoglin-silenced endometrial epithelial cells (human and mouse origin) showed poor trophoblast outgrowth, which suggests an essential role for endoglin during endometrial receptivity. In conclusion, our findings reveal the association of endoglin with endometrial receptivity, which is important for embryo attachment.

Lysophosphatidic Acid (LPA) Receptor 3-Mediated LPA Signal Transduction Pathways: A Possible Relationship with Early Development of Peri-Implantation Porcine Conceptus

Lysophosphatidic acid (LPA) is a phospholipid with a variety of fatty acyl groups that mediates diverse biological effects on various types of cells through specific G protein-coupled receptors. LPA appears to play a significant role in many reproductive processes, including luteolysis, implantation, and placentation. Our previous study in pigs demonstrated that LPA and the LPA receptor system are present at the maternal-conceptus interface and that LPA increases uterine endometrial expression of prostaglandin-endoperoxide synthase 2 (PTGS2) through LPA receptor 3 (LPAR3). However, the role of LPA in conceptuses during early pregnancy has not been determined. Therefore, this study examined the effects of LPA in cell proliferation, migration, and activation of the intracellular signaling pathway in porcine conceptuses by using an established porcine trophectoderm (pTr) cell line isolated from Day 12 conceptuses. All examined LPA species with various fatty acid lengths increased proliferation and migration of pTr cells as the dosage increased. Immunoblot analyses found that LPA activated intracellular signaling molecules, extracellular signal-regulated kinase 1/2 (ERK1/2), ribosomal protein S6 kinase 90 kDa (P90RSK), ribosomal protein S6 (RPS6), and P38 in pTr cells. Furthermore, LPA increased expression of PTGS2 and urokinase-type plasminogen activator (PLAU), and the LPA-induced increases in PTGS2 and PLAU expression were inhibited by LPAR3 siRNA. Collectively, these results showed that LPA promotes proliferation, migration, and differentiation of pTr cells by activating the ERK1/2-P90RSK-RPS6 and P38 pathways, indicating that the LPA-LPAR3 system may be involved in the development of trophoblast during early pregnancy in pigs.

Expression of aquaporin 1 and 5 and their regulation by ovarian hormones, arachidonic acid, forskolin and cAMP during implantation in pigs

Aquaporin proteins (AQPs) are a family of channels expressed in numerous mammalian tissues, where they play a fundamental role in regulating water transport across cell membranes. Based on reports that AQPs are present in the reproductive system and participate in reproductive processes, our aim was to investigate the effect of progesterone (P(4)), estradiol (E(2)), oxytocin (OT), arachidonic acid (AA), forskolin (FSK) and cyclic adenosine monophosphate (cAMP) on AQP1 and AQP5 expression at mRNA and protein levels in porcine uterine explants from Days 14-16 of gestation in order to determine if they play a role in implantation period in pigs. Quantitative real time PCR and Western-blot analysis revealed that the uterine explants treated with FSK and cAMP produce delayed, but long-term effects on AQP1 abundance (24 h) while AQP5 had a rapid and sustained response to FSK and cAMP in protein content (3 and 24 h). AA increases gene and protein content of AQP1 after longer exposition whereas AQP5 increases after 3 h only at the protein level. Both AQPs potentially remains under control of steroid hormones. OT has been shown to increase AQP1, and decrease AQP5 mRNA, without visible changes in protein content. P(4), E(2), AA, FSK and cAMP caused the appearance of AQP5 expression in the basolateral plasma membrane of the epithelial cells. The staining represents most likely AQP5 functioning mechanism for both absorption and reabsorption across the glandular epithelium.

Extracellular Vesicles Originate from the Conceptus and Uterus During Early Pregnancy in Sheep

Cells release diverse types of membrane-bound vesicles of endosomal and plasma membrane origin, termed exosomes and microvesicles, respectively. Extracellular vesicles (EVs) represent an important mode of intercellular communication by transferring select RNAs, proteins, and lipids between cells. The present studies tested the hypothesis that the elongating ovine conceptus and uterus produces EVs that mediate conceptus-maternal interactions during early pregnancy. In Study 1, EVs were purified from uterine luminal fluid of Day 14 cyclic sheep. The EVs were fluorescently labeled with PKH67 dye and infused into the uterine lumen of pregnant sheep for 6 days using an osmotic pump. On Day 14, labeled EVs were observed in the conceptus trophectoderm and uterine epithelia, but not in the uterine stroma or myometrium. In Study 2, Day 14 conceptuses were cultured ex vivo for 24 h and found to release EVs into the culture medium. Proteomics analysis of the Day 14 conceptus-derived EVs identified 231 proteins that were enriched for extracellular space and several protein classes, including proteases, protease inhibitors, chaperones and chaperonins. RNA sequencing of Day 14 conceptus-derived EVs detected expression of 512 mRNAs. The top-expressed genes were overrepresented in ribosomal functions and components. Isolated EVs from conceptuses were fluorescently labeled with PKH67 and infused into the uterine lumen of cyclic sheep for 6 days using an osmotic pump. On Day 14, labeled EVs were observed in the uterine epithelia, but not in the uterine stroma or myometrium. Labeled EVs were not observed in the ovary or in other maternal tissues. These studies support the ideas that EVs emanate from both the conceptus trophectoderm and uterine epithelia, and are involved in intercellular communication between those cells during the establishment of pregnancy in sheep.

Stimulatory effects of interleukin-1 beta on development of porcine uterine epithelial cell are mediated by activation of the ERK1/2 MAPK cell signaling cascade

Successful establishment of pregnancy depends on timely changes in the conceptus (embryo and associated extra-embryonic membranes) and uterine endometrium orchestrated by molecules from both the conceptus and uterus. Interleukin-1 beta (IL-1β) is an important mediator of that communication regulating development of the peri-implantation conceptus and opening the window of implantation during early pregnancy. However, little is known about IL-1β-mediated intracellular signaling cascades and functional effects in uterine luminal epithelium (LE) during the peri-implantation period of pregnancy in pigs. Therefore, this study determined, using an immortalized porcine LE (pLE) cell line from day 12 pregnant gilts: 1) the intracellular signaling cascade responsible for activities of IL-1β in pLE cells, and 2) the changes in cellular activities induced by IL-1β. IL-1β stimulated phosphorylation of ERK1/2 proteins in pLE cells in a dose-dependent manner. Ten ng/ml IL-1β increased levels of phosphorylated (p)-ERK1/2 proteins in pLE cells within 15 min post-treatment, and this IL-1β-induced phosphorylated status was inhibited by increasing doses of U0126 (ERK1/2 inhibitor). In addition IL-1β increased p-P70S6K, p-P90S6K, p-S6, and p-P38 proteins in a time-dependent manner, but IL-1β-induced activation of P70S6K and S6 proteins was significantly decreased in the presence of pharmacological inhibitors for ERK1/2 (U0126), MTOR (rapamycin), and P38 (SB203580). Moreover, IL-1β treatment potently increased the abundance of p-ERK1/2 proteins in the nucleus and cytoplasm. Similarly cytoplasmic p-S6 proteins were localized abundantly in the pLE cells treated with IL-1β. Furthermore, IL-1β increased proliferation of pLE cells by approximately 200%, and pretreatment of pLE cells with U0126 significantly inhibited this stimulatory effect. Collectively, results of this study indicate that IL-1β plays an important role in development of uterine LE by stimulating cell proliferation, and that these effects are coordinately regulated by activation of the ERK1/2 and P38 MAPK cell signaling cascades.

Analysis of Stage-Specific Gene Expression Profiles in the Uterine Endometrium during Pregnancy in Pigs

The uterine endometrium plays a critical role in regulating the estrous cycle and the establishment and maintenance of pregnancy in mammalian species. Many studies have investigated the expression and function of genes in the uterine endometrium, but the global expression pattern of genes and relationships among genes differentially expressed in the uterine endometrium during gestation in pigs remain unclear. Thus, this study investigated global gene expression profiles using microarray in pigs. Diverse transcriptome analyses including clustering, network, and differentially expressed gene (DEG) analyses were performed to detect endometrial gene expression changes during the different gestation stages. In total, 6,991 genes were found to be differentially expressed by comparing genes expressed on day (D) 12 of pregnancy with those on D15, D30, D60, D90 and D114 of pregnancy, and clustering analysis of detected DEGs distinguished 8 clusters. Furthermore, several pregnancy-related hub genes such as ALPPL2, RANBP17, NF1B, SPP1, and CST6 were discovered through network analysis. Finally, detected hub genes were technically validated by quantitative RT-PCR. These results suggest the complex network characteristics involved in uterine endometrial gene expression during pregnancy and indicate that diverse patterns of stage-specific gene expression and network connections may play a critical role in endometrial remodeling and in placental and fetal development to establish and maintenance of pregnancy in pigs.

Temporal Release, Paracrine and Endocrine Actions of Ovine Conceptus-Derived Interferon-Tau During Early Pregnancy

The antiviral activity of interferon (IFN) increases in uterine vein serum (UVS) during early pregnancy in sheep. This antiviral activity in UVS collected on Day 15 of pregnancy is blocked by anti-IFN-tau (anti-IFNT) antibodies. Conceptus-derived IFNT was hypothesized to induce IFN-stimulated gene (ISG) expression in endometrium and extrauterine tissues during pregnancy. To test this hypothesis, blood was collected from ewes on Days 12-16 of the estrous cycle or pregnancy. Serum progesterone was >1.7 ng/ml in pregnant (P) and nonpregnant (NP) ewes until Day 13, then declined to <0.6 ng/ml by Day 15 in NP ewes. A validated IFNT radioimmunoassay detected IFNT in uterine flushings (UFs) on Days 13-16 and in UVS on Days 15-16 of pregnancy. IFNT detection in UF correlated with paracrine induction of ISGs in the endometrium and occurred prior to the inhibition of estrogen receptor 1 and oxytocin receptor expression in uterine epithelia on Day 14 of pregnancy. Induction of ISG mRNAs in corpus luteum (CL) and liver tissue occurred by Day 14 and in peripheral blood mononuclear cells by Day 15 in P ewes. Expression of mRNAs for IFN signal transducers and ISGs were greater in the CL of P than that of NP ewes on Day 14. It is concluded that: 1) paracrine actions of IFNT coincide with detection of IFNT in UF; 2) endocrine action of IFNT ensues through induction of ISGs in peripheral tissues; and 3) IFNT can be detected in UVS, but not until Days 15-16 of pregnancy, which may be limited by the sensitivity of the IFNT radioimmunoassay.

Expression of estrus modifies the gene expression profile in reproductive tissues on Day 19 of gestation in beef cows

The aim of this study was to test the effect of expression of estrus at artificial insemination (AI) on endometrium, conceptus, and CL gene expression of beef cows. Thirty-six multiparous nonlactating Nelore cows were enrolled on an estradiol- and progesterone (P4)-based timed AI protocol (AI = Day 0) and then slaughtered for the endometrium, CL, and conceptus collection on Day 19. The animals were retrospectively grouped on the basis of cows that (1) showed signs of estrus near AI (n = 19; estrus) and (2) did not show any signs of estrus (n = 17; nonestrus). Body condition score, blood sampling, and ultrasound examination were performed on Days 0, 7, and 18 of the experiment followed by messenger RNA extraction and quantitative reverse transcription polymerase chain reaction analysis of 58 target genes. Data were checked for normality and analyzed by ANOVA for repeated measures using proc GLM, MIXED, and UNIVARIATE of SAS. Only pregnant cows were included in the analyses (n = 12; nonestrus, n = 11). Estrous expression had no correlation with parameters such as body condition score, preovulatory follicle and CL diameter, P4 concentration in plasma on Days 7 and 18 after AI, and interferon-tau concentration in the uterine flushing (P > 0.15); however, a significant increase was observed in conceptus size from cows that expressed estrus (P = 0.02; 38.3 ± 2.8 vs. 28.2 ± 2.9 mm). The majority of transcripts affected by estrous expression in the endometrium belong to the immune system and adhesion molecule family (MX1, MX2, MYL12A, MMP19, CXCL10, IGLL1, and SLPI; P ≤ 0.05), as well as those related with prostaglandin synthesis (OTR and COX-2; P ≤ 0.05). Genes related to apoptosis, P4 synthesis, and prostaglandin receptor were downregulated (CYP11A, BAX, and FPr; P < 0.05) in the CL tissue of cows that expressed estrus. In addition, four genes were identified as differentially expressed in the 19-day-old conceptus from cows that expressed estrus (ISG15, PLAU, BMP15, and EEF1A1; P < 0.05). There was also a significant effect of Day 7 concentration of P4 mainly affecting the immune system, adhesion molecules, and wnt signaling pathway of the endometrium (IGLL1, MX2, SLPI, TRD, APC, WNT2, GLYCAM1, and MYL12A; P < 0.05). A significant interaction between estrous expression and P4 concentration on Day 7 was more pronounced in immune system genes (MX1, MX2, TRD, SLPI, and IGLL1; P < 0.05). This study reported that estrous expression at the time of AI favorably altered the gene expression profile in reproductive tissues during the preimplantation phase toward a more receptive state to the elongating conceptus. These effects seem to be more evident in the endometrium during the time of dynamic remodeling for embryo implantation.

Deletion of Lysophosphatidic Acid Receptor 3 (Lpar3) Disrupts Fine Local Balance of Progesterone and Estrogen Signaling in Mouse Uterus During Implantation

Lpar3 encodes LPA3, the third G protein-coupled receptor for lysophosphatidic acid (LPA). Lpar3(-/-) female mice had delayed embryo implantation. Their serum progesterone and estrogen levels were comparable with control on Gestation Day 3.5 (D3.5) at 1100 h. There was reduced cell proliferation in D3.5 and D4.5 Lpar3(-/-) stroma. Progesterone receptor (PGR) disappeared from D4.5 Lpar3(+/+) uterine luminal epithelium (LE) but remained highly expressed in D4.5 Lpar3(-/-) LE. Pgr and PGR- target genes but not estrogen receptor alpha (ERalpha [Esr1]) or ESR target genes, were upregulated in D4.5 Lpar3(-/-) LE. It was hypothesized that suppression of PGR activity in LE could restore on-time uterine receptivity in Lpar3(-/-) mice. A low dose of RU486 (5 μg/mouse) given on D3.5 at 900 h rescued delayed implantation in all pregnant Lpar3(-/-) females and significantly increased number of implantation sites compared to vehicle-treated pregnant Lpar3(-/-) females detected on D4.5. E2 (25 ng/mouse) had a similar effect as 5 μg RU486 on embryo implantation in Lpar3(-/-) females. However, when the ovaries were removed on late D2.5 to create an experimentally induced delayed implantation model, 25 ng E2 activated implantation in Lpar3(+/+) but not Lpar3(-/-) females detected on D4.5. These results demonstrate that deletion of Lpar3 leads to an increased ratio of progesterone signaling/estrogen signaling that can be optimized by low doses of RU486 or E2 to restore on-time implantation in Lpar3(-/-) females.

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.

Maternal N-Carbamylglutamate Supplementation during Early Pregnancy Enhances Embryonic Survival and Development through Modulation of the Endometrial Proteome in Gilts

BACKGROUND

Early pregnancy loss is a major concern in humans and animals. N-carbamylglutamate (NCG) has been found to enhance embryonic survival during early pregnancy in rats. However, little is known about the key factors in the endometrium involved in the improvement of embryonic implantation and development induced by maternal NCG supplementation.

OBJECTIVES

Our objectives were to investigate whether NCG supplementation during early gestation enhanced embryonic survival and development in gilts and to uncover the related factors using the approach of endometrium proteome analysis with isobaric tags for relative and absolute quantification (iTRAQ).

METHODS

Uteruses and embryos/fetuses were obtained on days 14 and 28 of gestation from gilts fed a basal diet that was or was not supplemented with 0.05% NCG. The iTRAQ-based quantitative proteomics approach was performed to explore the endometrium proteome altered by NCG supplementation.

RESULTS

Maternal NCG supplementation significantly increased the number of total fetuses and live fetuses on day 28 of gestation by 1.32 and 1.29, respectively (P < 0.05), with a significant decrease in embryonic mortality (P < 0.05). iTRAQ results indicated that a total of 59 proteins showed at least 2-fold differences (P < 0.05), including 52 proteins that were present at higher abundance and 7 proteins present at lower abundance in NCG-supplemented gilts. The differentially expressed proteins primarily are involved in cell adhesion, energy metabolism, lipid metabolism, protein metabolism, antioxidative stress, and immune response. On day 14 of gestation, several proteins closely related to embryonic implantation and development, such as integrin-αv, integrin-β3, talin, and endothelial nitric oxide synthase, were upregulated (3.7-, 4.1-, 2.4-, and 5.4-fold increases, respectively) by NCG supplementation.

CONCLUSION

To our knowledge, our results provide the first evidence that altered abundance of the endometrial proteome induced by NCG supplementation is highly associated with the improvement of embryonic survival and development in gilts.

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.

Select nutrients and their effects on conceptus development in mammals

The dialogue between the mammalian conceptus (embryo/fetus and associated membranes) involves signaling for pregnancy recognition and maintenance of pregnancy during the critical peri-implantation period of pregnancy when the stage is set for implantation and placentation that precedes fetal development. Uterine epithelial cells secrete and/or transport a wide range of molecules, including nutrients, collectively referred to as histotroph that are transported into the fetal-placental vascular system to support growth and development of the conceptus. The availability of uterine-derived histotroph has long-term consequences for the health and well-being of the fetus and the prevention of adult onset of metabolic diseases. Histotroph includes numerous amino acids, but arginine plays a particularly important role as a source of nitric oxide and polyamines required for fetal-placental development in rodents, swine and humans through mechanisms that remain to be fully elucidated. Mechanisms whereby arginine regulates expression of genes via the mechanistic target of rapamycin cell signaling pathways critical to conceptus development, implantation and placentation are discussed in detail in this review.

Dimethylated H3K27 Is a Repressive Epigenetic Histone Mark in the Protist Entamoeba histolytica and Is Significantly Enriched in Genes Silenced via the RNAi Pathway

RNA interference (RNAi) is a fundamental biological process that plays a crucial role in regulation of gene expression in many organisms. Transcriptional gene silencing (TGS) is one of the important nuclear roles of RNAi. Our previous data show that Entamoeba histolytica has a robust RNAi pathway that links to TGS via Argonaute 2-2 (Ago2-2) associated 27-nucleotide small RNAs with 5'-polyphosphate termini. Here, we report the first repressive histone mark to be identified in E. histolytica, dimethylation of H3K27 (H3K27Me2), and demonstrate that it is enriched at genes that are silenced by RNAi-mediated TGS. An RNAi-silencing trigger can induce H3K27Me2 deposits at both episomal and chromosomal loci, mediating gene silencing. Our data support two phases of RNAi-mediated TGS: an active silencing phase where the RNAi trigger is present and both H3K27Me2 and Ago2-2 concurrently enrich at chromosomal loci; and an established silencing phase in which the RNAi trigger is removed, but gene silencing with H3K27Me2 enrichment persist independently of Ago2-2 deposition. Importantly, some genes display resistance to chromosomal silencing despite induction of functional small RNAs. In those situations, the RNAi-triggering plasmid that is maintained episomally gets partially silenced and has H3K27Me2 enrichment, but the chromosomal copy displays no repressive histone enrichment. Our data are consistent with a model in which H3K27Me2 is a repressive histone modification, which is strongly associated with transcriptional repression. This is the first example of an epigenetic histone modification that functions to mediate RNAi-mediated TGS in the deep-branching eukaryote E. histolytica.

Biological Roles of Hydroxysteroid (11-Beta) Dehydrogenase 1 (HSD11B1), HSD11B2, and Glucocorticoid Receptor (NR3C1) in Sheep Conceptus Elongation

In sheep, the elongating conceptus synthesizes and secretes interferon tau (IFNT) as well as prostaglandins (PGs) and cortisol. The enzymes, hydroxysteroid (11-beta) dehydrogenase 1 (HSD11B1) and HSD11B2 interconvert cortisone and cortisol. In sheep, HSD11B1 is expressed and active in the conceptus trophectoderm as well as in the endometrial luminal epithelia; in contrast, HSD11B2 expression is most abundant in conceptus trophectoderm. Cortisol is a biologically active glucocorticoid and ligand for the glucocorticoid receptor (NR3C1 or GR) and mineralocorticoid receptor (NR3C2 or MR). Expression of MR is not detectable in either the ovine endometrium or conceptus during early pregnancy. In tissues that do not express MR, HSD11B2 protects cells from the growth-inhibiting and/or proapoptotic effects of cortisol, particularly during embryonic development. In study one, an in utero loss-of-function analysis of HSD11B1 and HSD11B2 was conducted in the conceptus trophectoderm using morpholino antisense oligonucleotides (MAOs) that inhibit mRNA translation. Elongating, filamentous conceptuses were recovered on Day 14 from ewes infused with control morpholino or HSD11B2 MAO. In contrast, HSD11B1 MAO resulted in severely growth-retarded conceptuses or conceptus fragments with apoptotic trophectoderm. In study two, clustered regularly interspaced short palindromic repeat (CRISPR)/Cas9 genome editing was used to determine the role of GR in conceptus elongation and development. Elongating, filamentous-type conceptuses (12-14 cm in length) were recovered from ewes gestating control embryos (n = 7/7) and gestating GR-edited embryos (n = 6/7). These results support the idea that the effects of HSD11B1-derived cortisol on conceptus elongation are indirectly mediated by the endometrium and are not directly mediated through GR in the trophectoderm.

Mitogen activated protein kinase pathway-dependent effects of platelet-derived growth factor on migration of trophectoderm cells

Successful development of the conceptus and implantation requires an intimate trophic connection between maternal uterus and conceptus mediated by local regulators including growth factors. Platelet-derived growth factor (PDGF) acts as a chemotactic factor for a variety of cell types. Current studies have determined that PDGF participates in rapid growth and development of cleavage stage embryos, but PDGF-induced effects on the growth and development of peri-implantation conceptus remains unknown. In the present study, PDGF induced phosphorylation of ERK1/2, AKT and RPS6 proteins in porcine trophectoderm (pTr) cells in a dose- and time-dependent manner. Addition of U0126 (an inhibitor of ERK1/2) or LY294002 (a PI3K inhibitor) blocked PDGF-induced effects on phosphorylation of signaling proteins. Combinations of PDGF and U0126 decreased PDGF-induced p-ERK1/2 and p-AKT1, but combinations of PDGF and LY294002 blocked only PDGF-induced AKT phosphorylation. Furthermore, PDGF significantly induced pTr cell migration and these stimulatory effects were blocked by U0126 and LY294002. Immunoreactive p-ERK1/2 and p-RPS6 proteins were abundant in pTr cells treated with PDGF, but U0126 reduced PDGF-induced p-ERK1/2 and p-RPS6 levels to basal amounts. Present study suggests that PDGF secreted into the maternal-conceptus microenvironment stimulates pTr cell migration through signal transduction cascades mediated by the ERK1/2 MAPK and AKT1 pathways.

Supplementation with rumen-protected L-arginine-HCl increased fertility in sheep with synchronized estrus

The aim of the present study was to evaluate the effects of L-arginine-HCl supplementation on ovulation rate, fertility, prolificacy, and serum VEGF concentrations in ewes with synchronized oestrus. Thirty Suffolk ewes with a mean body weight of 45 ± 3 kg and a mean body condition score (BCS) of 2.4 ± 0.28 were synchronized for estrus presentation with a progestin-containing sponge (20 mg Chronogest® CR) for 9 days plus PGF2-α (Lutalyse; Pfizer, USA) on day 7 after the insertion of the sponge. The ewes were divided into two groups; i.e., a control group (n = 15) that was fed on the native pasture (basal diet) and an L-arginine-HCl group (n = 15) that received 7.8 g of rumen-protected L-arginine-HCl from day 5 of the sponge insertion until day 25 after mating plus the basal diet. The L-arginine-HCl was administered daily via an esophageal probe between days 5 and 9 of the synchronization protocol and every third day subsequently. Blood samples were drawn from the jugular vein every 6 days throughout the entire experimental period. The results revealed that the L-arginine-HCl supplementation increased fertility during the synchronized estrus (P = 0.05). However, no effects were observed on the final BCS (P = 0.78), estrus presentation (P = 0.33), multiple ovulations (P = 0.24), prolificacy (P = 0.63), or serum VEGF concentration. In conclusion, L-arginine-HCl supplementation during the period used in this study increased fertility in sheep with synchronized estrus possibly due to improved embryo-fetal survival during early pregnancy.