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

An active peptide from yak inhibits hypoxia-induced lung injury via suppressing VEGF/MAPK/inflammatory signaling

Pulmonary vascular remodeling and inflammation play an important role in the hypoxic-induced lung diseases. Our previous investigations showed that peptide from yak milk residues could alleviate inflammation. In this study, our results suggest that peptide (LV) from yak milk residues peptide had protective effect of lung in the animal models of hypoxic-induced lung injury. LV Gavage could improve pulmonary vascular remodeling in the lung tissues of hypoxic mice. A comprehensive analysis of metabolomics and transcriptomics revealed that 5-KETE, 8,9-EET, and 6-keto-prostaglandin F1a might be potential targets to prevent lung injury in the hypoxic mice. These metabolites can be regulated by MAPK/VEGF and inflammatory pathways. Our data indicated that LV treatment could inhibit apoptosis and inflammation via Nrf2/NF-κB/MAPK/PHD-2 pathway and protected hypoxic-induced lung epithelial cells injury. Taken together, our results suggest that LV provides a novel therapeutic clue for the prevention of hypoxia-induced lung injury and inflammation-related lung diseases.

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.

C/EBP-β contributes to pig endometrial LE receptivity by targeting cell remodeling genes during implantation

In brief

Transforming the endometrial luminal epithelium (LE) into a receptive state is a requisite event for successful embryo implantation. This study suggests the role of a transcription factor in regulating endometrial LE receptivity.

Abstract

The endometrial luminal epithelium (LE) undergoes extensive remodeling during implantation to establish receptivity of the uterus in response to the conceptus signals, such as interleukin 1β (IL1B). But the mechanisms remain to be fully understood. This study investigated the role of CCAAT/enhancer-binding protein β (C/EBP-β) in regulating pig endometrial LE receptivity. Our results showed that C/EBP-β was expressed and activated only in the endometrial LE in an implantation-dependent manner. In addition, C/EBP-β was highly activated at the pre-attachment stage compared to the attachment stage, and its activation was correlated with the expression of IL1B-dependent extracellular signal-regulated kinases1/2-p90 ribosomal S6 kinase signaling axis. Subsequent chromatin immunoprecipitation (ChIP)-sequencing analysis revealed that the binding of C/EBP-β within the promoter was positively associated with the transcription of genes related to cell remodeling. One such gene is matrix metalloproteinase 8 (MMP8), which is responsible for extracellular matrix degradation. The expression of MMP8 was abundant at the pre-attachment stage but dramatically declined at the attachment stage in the endometrial LE. Consistent with C/EBP-β, the expression and activation of MMP8 were limited to the endometrial LE in an implantation-dependent manner. Using ChIP-qPCR and electrophoresis mobility shift assay approaches, we demonstrated that C/EBP-β regulated the expression of the MMP8 gene during implantation. Furthermore, we detected that MMP8 and one of its substrates, type II collagen, showed a mutually exclusive expression pattern in pig endometrial LE during implantation. Our findings indicate that C/EBP-β plays a role in pig endometrial LE receptivity by regulating cell remodeling-related genes, such as MMP8, in response to conceptus signals during implantation.

Zearalenone induces apoptosis and autophagy by regulating endoplasmic reticulum stress signalling in porcine trophectoderm cells

Zearalenone (ZEA), a mycotoxin produced mainly by fungi belonging to Fusarium species in foods and feeds, causes a serious hazard to humans and animals. Numerous studies have revealed that ingesting ZEA can disrupt the reproductive function and impair the reproductive process in animals. This experiment was to investigate the toxicological effect and the mechanism of ZEA exposure on reproduction in pigs during early stages of pregnancy. In the present study, we treated with 0 to 80 μmol/L ZEA for 12 or 24 h in trophoblast ectoderm (pTr) cells. The results showed that ZEA had significantly decreased cell proliferation (P < 0.05), which was accompanied by DNA damage-related cell cycle arrest at G2/M phase, activation of the apoptosis and endoplasmic reticulum (ER) stress, as well as impairment of barrier function (P < 0.05). Western blot analysis and transmission electron microscopy (TEM) showed that exposure to ZEA can activation of autophagy in pTr cells. Importantly, pretreatment with chloroquine (CQ) or 3-methyladenine (3-MA) led to increased apoptosis in pTr cells. Interestingly, pTr cells pretreated with 4-phenylbutyric acid (4-PBA), an inhibitor of ER stress, resulted in reduced cell death in pTr cells, indicating a critical role for ER stress in the activation of autophagy. In conclusion, these results reveal that ZEA-triggered ER stress is critical for the cell fate decision of pTr cells during early porcine embryonic development. Application of small molecules with ability of blocking ER stress might be therapeutic option to reduce the deleterious effect of ZEA in pregnant animals.

Pyridaben leads to inhibition of cell growth and induction of cell death through intracellular mechanisms in early pregnancy

Recently, infertility has become a major global issue. It is crucial to identify environmental factors that lead to infertility. The prevalent use of pesticides in agriculture results in the exposure of livestock and humans to these pesticides. Studies have reported the harmful effects of pesticides on pregnancy. Pyridaben, a pesticide that inhibits mitochondrial complex 1, has been reported to have detrimental effects on neurons, spermatogenesis, hormonal balance, and embryonic development. However, the effect of pyridaben on the female reproductive system has not yet been studied. Therefore, in this study, we evaluated the effects of pyridaben on early pregnancy in porcine reproductive cell lines, which are known to mimic the female reproductive system. Results demonstrated that pyridaben decreased cell growth in porcine endometrial luminal epithelial and porcine trophectoderm cell lines through inhibition of cell signal transduction. Further, pyridaben increased subG1 phase and late apoptosis through the induction of reactive oxygen species production, mitochondrial dysfunction, calcium unbalances, pro-apoptotic signals, and endoplasmic reticulum (ER) stress. Moreover, we found that pyridaben induced autophagy and inhibition of placentation through the regulation of ER-mitochondria axis proteins. Overall, pyridaben was found to be harmful in early pregnancy in pigs and may have similar effects in human pregnancy.

The In Vitro Effect of Prostaglandin E2 and F2α on the Chemerin System in the Porcine Endometrium during Gestation

Chemerin belongs to the group of adipocyte-derived hormones known as adipokines, which are responsible mainly for the control of energy homeostasis. Adipokine exerts its influence through three receptors: Chemokine-like receptor 1 (CMKLR1), G protein-coupled receptor 1 (GPR1), and C-C motif chemokine receptor-like 2 (CCRL2). A growing body of evidence indicates that chemerin participates in the regulation of the female reproductive system. According to the literature, the expression of chemerin and its receptors in reproductive structures depends on the local hormonal milieu. The aim of this study was to investigate the in vitro effect of prostaglandins E2 (PGE2) and F2α (PGF2α) on chemerin and chemerin receptor (chemerin system) mRNAs (qPCR) and proteins (ELISA, Western blotting) in endometrial tissue explants collected from early-pregnant gilts. Both PGE2 and PGF2α significantly influenced the expression of the chemerin gene, hormone secretion, and the expression of chemerin receptor genes and proteins. The influence of both prostaglandins on the expression of the chemerin system varied between different stages of gestation. This is the first study to describe the modulatory effect of PGE2 and PGF2α on the expression of the chemerin system in the porcine uterus during early gestation.

Orexin B affects the transcriptome of incubated in vitro porcine endometrial explants from the early-implantation period

This study determined the effect of orexin B (OXB) on the porcine endometrial transcriptome during the embryo attachment phase. Microarray analyses of gene ontology (GO), biological pathways, networks and differentially expressed genes (DEG) were performed. Orexin B influenced the expression of 887 genes (fold change > 1.2; p < .05): 620 genes were up-regulated, and 267 were down-regulated. The analysis of the relationship between DEG revealed that OXB interacts with genes linked with processes such as cell hormone binding, regulation of hormone levels, lipid transport, steroid metabolic processes, the apoptotic signalling pathway and the acute inflammatory response, which are pivotal for reproductive success. Orexin B played a bivalent role in the early-pregnant uterus by limiting the pregnancy outcome, promoting embryo development, suppressing the immune system and, consequently, preventing embryo rejection. These findings suggest that OXB could be responsible for the proper course of gestation by adapting litter size to the metabolic status of the maternal organism.

Obesity in mares promotes uterine inflammation and alters embryo lipid fingerprints and homeostasis

Maternal body composition can be an important determinant for development of obesity and metabolic syndrome in adult offspring. Obesity-related outcomes in offspring may include epigenetic alterations; however, mechanisms of fetal programming remain to be fully elucidated. This study was conducted to determine the impact of maternal obesity in the absence of a high fat diet on equine endometrium and preimplantation embryos. Embryos were collected from normal and obese mares at 8 and 16 days and a uterine biopsy at 16 days (0 day = ovulation). With the exception of 8 day embryos, each sample was divided into two pieces. One piece was analyzed for gene expression markers related to carbohydrate metabolism, lipid homeostasis, inflammation, endoplasmic reticulum stress, oxidative stress, mitochondrial stress, and components of the insulin-like growth factor (IGF) system. The second piece was analyzed for lipid content using matrix-assisted laser desorption/ionization mass spectrometry. Obese mares had elevated concentrations of insulin, leptin, and total cholesterol, and they tended to have increased triglycerides and decreased insulin sensitivity. Embryos from obese mares had altered transcript abundance in genes for inflammation and lipid homeostasis, as well as endoplasmic reticulum, oxidative and mitochondrial stress and altered lipid fingerprints. Endometrium from obese mares had increased expression of inflammatory cytokines, lipid homeostasis regulation, mitochondrial stress, and the IGF2 system. This study demonstrates that increased adiposity in mares alters the uterine environment, transcript abundance of genes for cellular functions, and lipid profiles of embryos. These alterations could affect prenatal programming, with potential long-term effects in offspring.

Differential transcriptome dynamics during the onset of conceptus elongation and between female and male porcine embryos

Background

Porcine embryos undergo rapid differentiation and expansion between Days 8 and 12 before attaching to the maternal uterine epithelial surface after Day 13. It is known that maternal recognition of pregnancy and successful implantation are driven by mutual interactions between the elongated conceptus and the maternal endometrium. While most of the genes involved in regulation of embryo development are located on autosomal chromosomes, gene expression on sex chromosomes is modulating development through sex-specific transcription. To gain more insights into the dynamic transcriptome of preimplantation embryos at the onset of elongation and into X-linked gene expression, RNA-seq analyses were performed for single female and male porcine embryos collected on Days 8, 10, and 12 of pregnancy.

Results

A high number of genes were differentially expressed across the developmental stages (2174 and 3275 for Days 8 vs 10, and 10 vs 12, respectively). The majority of differentially expressed genes (DEGs) were involved in embryo elongation, development, and embryo-maternal interaction. Interestingly, a number of DEGs was found with respect to embryo sex (137, 37, and 56 on Days 8, 10 and 12, respectively). At Day 8, most of these DEGs were X-linked (96). Strikingly, the number of DEGs encoded on the X chromosome dramatically decreased from Day 10 to Day 12.

Conclusions

The obtained results deepen the understanding about temporary transcriptomic changes in porcine embryos during the phase of conceptus elongation, meanwhile reveal dynamic compensation of X chromosome in the female and distinct transcriptional differences between female and male embryos.

Electronic supplementary material

The online version of this article (10.1186/s12864-019-6044-z) contains supplementary material, which is available to authorized users.

ROS-induced autophagy regulates porcine trophectoderm cell apoptosis, proliferation, and differentiation

Significant embryo loss remains a serious problem in pig production. Reactive oxygen species (ROS) play a critical role in embryonic implantation and placentation. However, the potential mechanism of ROS on porcine trophectoderm (pTr) cell fate during the peri-implantation period has not been investigated. This study aimed to elucidate the effects of ROS on pTr cell phenotypes and the regulatory role in cell attachment and differentiation. Herein, results showed that exogenous H₂O₂ inhibited pTr cell viability, arrested the cell cycle at S and G2/M phases, and increased cell apoptosis and autophagy protein light chain 3B and Beclin-1, whereas these effects were reversed by different concentrations of N-acetyl-l-cysteine (NAC) posttreatment. In addition, NAC abolished H₂O₂-induced autophagic flux, inhibited intracellular and mitochondrial ROS, and restored expression of genes important for mitochondrial DNA and biogenesis, cell attachment, and differentiation. NAC reversed H₂O₂-activated MAPK and Akt/mammalian target of rapamycin pathways in dose-dependent manners. Furthermore, analyses with pharmacological and RNA interference approaches suggested that autophagy regulated cell apoptosis and gene expression of caudal-related homeobox 2 and IL-1β. Collectively, these results provide new insights into the role of the ROS-induced autophagy in pTr cell apoptosis, attachment, and differentiation, indicating a promising target for decreasing porcine conceptus loss during the peri-implantation period.

Trichlorfon inhibits proliferation and promotes apoptosis of porcine trophectoderm and uterine luminal epithelial cells

Trichlorfon is an organophosphate insecticide widely used in agriculture. Additionally, it is applied to pigs for control of endo- and ectoparasites. Previous studies have shown the effects of trichlorfon in pigs during late stages of gestation; however, little is known about its effects during early pregnancy, including implantation and placentation. We investigated whether trichlorfon affects proliferation and apoptosis of porcine trophectoderm (pTr) and uterine luminal epithelial (pLE) cells. Trichlorfon inhibited the proliferation of pTr and pLE cells, as evidenced by cell cycle arrest, and altered the expression of proliferation-related proteins. In addition, trichlorfon induced cell death and apoptotic features, such as loss of mitochondrial membrane potential and DNA fragmentation, in pTr and pLE cells. Moreover, trichlorfon treatment decreased concentrations of Ca²⁺ in the cytoplasm in both cell lines and increased concentrations of Ca²⁺ in mitochondria of pTr cells. Trichlorfon inhibited the activation of phosphoinositide 3-kinase/AKT and mitogen-activated protein kinase signaling pathways in pTr and pLE cells. Therefore, we suggest that trichlorfon-treated pTr and pLE cells exhibited abnormal cell physiology which might lead to early pregnancy failure.

Effects of 17β-estradiol, Interleukin-1β, and Human Chorionic Gonadotropin on Activity and mRNA Expression of Plasminogen Activators in Porcine Endometrial Cells

This study aimed to investigate changes in the activity and mRNA expression of plasminogen activators (PAs) induced by 17β-estradiol (E₂), human chorionic gonadotropin (hCG), and interleukin-1β (IL-1β) in porcine endometrial cells. Endometrial cells were isolated from the epithelium and cultured to 80% confluence. They were then treated for 24 h with E₂ (0.2, 2, 20, and 200 ng/mL), IL-1β (0.1, 1, 10, and 100 ng/mL), and hCG (0.5, 1, 1.5 and 2 IU/mL). mRNA expressions of urokinase-type (uPA) and tissue-type (tPA) PAs were analyzed using reverse transcription PCR, and activities were measured using a PA activity assay. mRNA expressions of uPA and tPA increased with E₂ treatment; however, this was not significant. Similarly, treatment with hCG did not influence the mRNA expressions of PAs. Interestingly, treatment with 0.1 ng/mL IL-1β significantly reduced the mRNA expression of uPA, but did not affect that of tPA. Treatment with 2, 20, and 200 ng/mL E₂ increased PA activity compared with the control group; treatment with 0.1 and 1 ng/mL IL-1β significantly increased PA activity compared with the other IL-1β treatment groups, whereas treatment with 10 and 100 ng/mL IL-1β decreased. Treatment with 2 IU/mL hCG increased PA activity compared with the other treatment groups, although there were no significant differences between the hCG and control groups. In conclusion, the activity and mRNA expression of PAs were differently regulated by the hormone/cytokine and its concentration in porcine endometrial cells. Therefore, understanding PA regulatory mechanisms may help to improve the reproductive potential of domestic animals.

PCV2 infection aggravates ochratoxin A-induced nephrotoxicity via autophagy involving p38 signaling pathway in vivo and in vitro

Ochratoxin A (OTA) is reported to induce nephrotoxicity in animals and humans. Porcine circovirus type 2 (PCV2) could induce porcine dermatitis and nephropathy syndrome. To date, little is known whether virus infection aggravates mycotoxin-induced toxicity. This work aimed to study the effects of PCV2 infection on OTA-induced nephrotoxicity and its mechanism in vivo and vitro. The results in vivo showed that PCV2 infection aggravated OTA-induced poor growth performance, nephrotoxicity, p38 phosphorylation and autophagy as demonstrated by Atg5, LC3 II and p62 protein expressions in kidney of pigs. The results in vitro indicated that PCV2 infection significantly aggravated OTA-induced nephrotoxicity as demonstrated by cell viabilities, annexin V/PI binding and caspase 3 activities, and induced p38 phosphorylation and autophagy in PK15 cells. p38 inhibitor decreased Atg5 and LC3 protein expression induced by PCV2 infection and OTA combined treatment. Adding autophagy inhibitor 3-MA or CQ alleviated the aggravating effects of PCV2 infection on OTA-induced nephrotoxicity. Atg5-specific siRNA eliminated the aggravating effects of PCV2 infection on OTA-induced nephrotoxicity. Taken together, these data indicate that in vivo and in vitro PCV2 infection aggravated OTA-induced nephrotoxicity via p38-mediated autophagy.

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.

Endometrial response to conceptus-derived estrogen and interleukin-1β at the time of implantation in pigs

The establishment of pregnancy is a complex process that requires a well-coordinated interaction between the implanting conceptus and the maternal uterus. In pigs, the conceptus undergoes dramatic morphological and functional changes at the time of implantation and introduces various factors, including estrogens and cytokines, interleukin-1β2 (IL1B2), interferon-γ (IFNG), and IFN-δ (IFND), into the uterine lumen. In response to ovarian steroid hormones and conceptus-derived factors, the uterine endometrium becomes receptive to the implanting conceptus by changing its expression of cell adhesion molecules, secretory activity, and immune response. Conceptus-derived estrogens act as a signal for maternal recognition of pregnancy by changing the direction of prostaglandin (PG) F_2α from the uterine vasculature to the uterine lumen. Estrogens also induce the expression of many endometrial genes, including genes related to growth factors, the synthesis and transport of PGs, and immunity. IL1B2, a pro-inflammatory cytokine, is produced by the elongating conceptus. The direct effect of IL1B2 on endometrial function is not fully understood. IL1B activates the expression of endometrial genes, including the genes involved in IL1B signaling and PG synthesis and transport. In addition, estrogen or IL1B stimulates endometrial expression of IFN signaling molecules, suggesting that estrogen and IL1B act cooperatively in priming the endometrial function of conceptus-produced IFNG and IFND that, in turn, modulate endometrial immune response during early pregnancy. This review addresses information about maternal-conceptus interactions with respect to endometrial gene expression in response to conceptus-derived factors, focusing on the roles of estrogen and IL1B during early pregnancy in pigs.

Cell-specific expression and signal transduction of C-C motif chemokine ligand 2 and atypical chemokine receptors in the porcine endometrium during early pregnancy

Chemokines and atypical chemokine receptors (ACKRs; also known as chemokine decoy receptors) play an important role in reproductive immunology by recruiting leukocytes during early pregnancy. The aim of this study was to determine the expression of C-C motif chemokine ligand 2 (CCL2) and ACKRs in the endometrium during estrous cycle and early pregnancy, and to investigate the functional effects of CCL2 on porcine uterine luminal epithelial (pLE) cells. Our results indicated that CCL2, ACKR1, ACKR3, and ACKR4 were strongly detected in the glandular and luminal epithelium of the endometrium during early pregnancy compared to that in non-pregnant pigs. Recombinant CCL2 improved pLE cell proliferation via activation of the PI3K and MAPK pathways and suppression of endoplasmic reticulum (ER) stress by reducing the expression of ER stress regulatory genes. Collectively, these results provide novel insights into CCL2-mediated signaling mechanisms in the porcine endometrium at the maternal-fetal interface during early pregnancy.

Inactivation of porcine interleukin-1β results in failure of rapid conceptus elongation

Conceptus expansion throughout the uterus of mammalian species with a noninvasive epitheliochorial type of placentation is critical establishing an adequate uterine surface area for nutrient support during gestation. Pig conceptuses undergo a unique rapid morphological transformation to elongate into filamentous threads within 1 h, which provides the uterine surface to support development and maintain functional corpora lutea through the production of estrogen. Conceptus production of a unique interleukin 1β, IL1B2, temporally increases during the period of trophoblast remodeling during elongation. CRISPR/Cas9 gene editing was used to knock out pig conceptus IL1B2 expression and the secretion of IL1B2 during the time of conceptus elongation. Trophoblast elongation occurred on day 14 in wild-type (IL1B2+/+) conceptuses but did not occur in ILB2-null (IL1B2-/-) conceptuses. Although the morphological transition of IL1B2-/- conceptuses was inhibited, expression of a number of conceptus developmental genes was not altered. However, conceptus aromatase expression and estrogen secretion were decreased, indicating that IL1B2 may be involved in the spatiotemporal increase in conceptus estrogen synthesis needed for the establishment of pregnancy in the pig and may serve to regulate the proinflammatory response of endometrium to IL1B2 during conceptus elongation and attachment to the uterine surface.

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.

Development of In Vitro Embryo Production System Using Collagen Matrix Gel Attached with Vascular Endothelial Growth Factor Derived from Interleukin-1 Beta-Treated Porcine Endometrial Tissue

The aim of this study was to establish an embryo culture system using collagen gel attached with vascular endothelial growth factor (VEGF) derived from interleukin-1 beta (IL-1β)-treated endometrial tissues from pigs. Endometria were separated from the porcine uterus at the follicular phase of the estrous cycle and were cultured with IL-1β. The collagen gels coincubated with IL-1β-treated endometria (C, without endometrial tissue; CE, with endometrial tissue; and CEI, IL-1β-treated endometrial tissue) were used for embryo culture. We found that, compared with the comparable figures in the control group, prostaglandin synthase-2 (PTGS-2) mRNA was increased in IL-1β-treated endometrial tissue (p < 0.05). The VEGF protein was not observed in collagen gel coincubated without endometrial tissue (C); however, it was detected in collagen gels coincubated with endometrial tissue (CE and CEI). The embryo cleavage rates and blastocyst formation did not differ among the treatment groups. The proportion of blastocysts did not differ among the groups. However, the number of blastocyst cells was significantly (p < 0.05) higher in the CEI group than in the other groups. These results clarify the effects of the intrauterine environment on preimplantation embryos and may be useful in research on the effects of extracellular matrix- and cytokine-treated endometrial tissue on embryo development.

Interleukins, interferons, and establishment of pregnancy in pigs

Early pregnancy in mammals requires complex and highly orchestrated cellular and molecular interactions between specialized cells within the endometrium and the conceptus. Proinflammatory cytokines are small signaling proteins released by leukocytes that augment innate and adaptive immune responses. They are also released by the mammalian trophectoderm as the conceptus apposes the uterine surface for implantation. On approximately day 12 of development in pigs, the conceptus undergoes a rapid morphological transformation referred to as elongation while simultaneously releasing estrogens and a novel conceptus form of interleukin-1 beta (IL1β). Following elongation, pig conceptuses express interferon gamma (IFNγ) and, in lesser amounts, interferon delta (IFNδ). Significant IFN signaling takes place within the endometrium between day 14 and 18 of pregnancy as the conceptus intimately associates with the uterine epithelium. Based on studies carried out in pigs and other mammals, the combined spacio-temporal activities of conceptus estrogens, IL1β, and IFN set in motion a series of coordinated events that promote establishment of pregnancy. This is achieved through enhancement of conceptus development, uterine receptivity, maternal-fetal hemotropic exchange, and endometrial leukocyte function. These events require activation of specific signaling pathways within the uterine luminal epithelium, glandular epithelium, and stroma. Here, we review proinflammatory cytokine expression by pig conceptuses and the hypothesized actions of these molecules during establishment of pregnancy.