Uterine biology in pigs and sheep

Effect of gestational age and fetal sex on metabolism of creatine by uteri, placentae, and fetuses of pigs†

The creatine (Cr) biosynthesis pathway buffers adenosine triphosphate in metabolically active tissues. We investigated whether sex of fetus and day of gestation influence Cr in endometrial and conceptus tissues from gilts on days 60 and 90 (n = 6 gilts/day) of gestation. Uterine and conceptus tissues associated with one male and one female fetus from each gilt were analyzed for creatine, messenger RNAs (mRNAs), and proteins for Cr biosynthesis. Total Cr decreased in amniotic fluid but increased in allantoic fluid between days 60 and 90 of gestation for male (P < 0.05) but not for female fetuses (P > 0.05). Endometrial expression of creatine kinase, muscle (CKM), creatine kinase mitochondrial type 1 (CKMT1), and solute carrier family 6, member 8 (SLC6A8) mRNAs increased (P < 0.05) between days 60 and 90 only for female fetuses. On day 60, expression of creatine kinase, brain (CKB) and CKMT1 mRNAs was greater (P < 0.05) for placentae of female than male fetuses. Livers of male fetuses had greater expression of arginine:glycine amidinotransferase (AGAT) and CKB than for females on day 60, while kidneys of female fetuses had greater expression of guanidinoacetate-N-methyltransferase (GAMT) than male fetuses on day 90 (P < 0.05). Localization of GAMT, CKB, CKMT1, and SLC6A8 proteins to uterine and chorionic epithelium was not influenced by gestational age or fetal sex. Arginine-glycine amidinotransferase localized to fetal kidneys and appeared greater on day 90 than on day 60 in both sexes. Thus, expression of the creatine-creatine kinase-phosphocreatine system at the uterine-conceptus interface is affected by gestational age and fetal sex to influence energy homeostasis in pigs.

Utero-placental adaptations in response to intrauterine growth restriction in swine

Intrauterine growth restriction (IUGR) is a common condition in swine associated with high piglet mortality and morbidity that develops in early gestation. This review article explores differences in uterine and placental tissues associated with IUGR fetuses compared to their normally-grown littermates at different stages of gestation. Specifically, we will review the available knowledge to date describing differences in 1) structure, 2) cellular apoptosis and proliferation, 3) adhesion, and 4) angiogenesis in endometrial and placental tissues associated with IUGR fetuses across gestation. Improved understanding of the mechanisms regulating IUGR is essential for the development of strategies to minimize the impact of IUGR in swine operations, thus improving reproductive efficiency and animal welfare.

Mechanisms of Homoarginine: Looking Beyond Clinical Outcomes

PURPOSE

Homoarginine (hArg) is an arginine metabolite that has been known for years, but its physiological role in the body remains poorly understood. For instance, it is well known that high hArg concentrations in the blood are protective against several disease states, yet the mechanisms behind these health benefits are unclear. This review compiles what is known about hArg, namely its synthetic pathways, its role in different diseases and conditions, and its proposed mechanisms of action in humans and experimental animals.

FINDINGS

Previous work has identified multiple pathways that control hArg synthesis and degradation in the body. Furthermore, endogenous hArg can modulate the cardiovascular system, with decreased hArg being associated with cardiovascular complications and increased mortality. Studies also suggest that hArg could serve as a diagnostic biomarker for a variety of immune, pancreatic, renal, and hepatic dysfunctions. Finally, in women, hArg concentrations rapidly increase throughout pregnancy and there are suggestions that alterations in hArg could indicate pregnancy complications like pre-eclampsia.

SUMMARY

Homoarginine is an under-appreciated amino acid with potential wide-ranging roles in systemic health, pregnancy, and pathophysiology. Although recent research has focused on its health or disease associations, there is a need for more investigations into understanding the mechanistic pathways by which hArg may operate. This could be aided using metabolomics, which provides a comprehensive approach to correlating multiple metabolites and metabolic pathways with physiological effects. Increasing our knowledge of hArg's roles in the body could pave the way for its routine use as both a diagnostic and therapeutic molecule.

Molybdenum interferes with MMPs/TIMPs expression to reduce the receptivity of porcine endometrial epithelial cells

To investigate the effect of trace element molybdenum (Mo) on the receptivity of porcine endometrial epithelial cells (PEECs) and evaluate Mo toxicity and its potential molecular mechanisms, Mo-treated PEECs models were established by incubating the cells with various concentrations of medium containing Mo (0, 0.005, 0.020, 0.200, and 5 mmol/L MoNa2O4·2H2O). The results showed that Mo disrupted the morphology and ultrastructure of PEECs, triggered blurred cell edges, cell swelling, cell cycle arrest, and increased apoptosis. At the molecular level, Mo treatment activated the TGF-β1/SMAD2 and PI3K/AKT1 pathways, causing a significant increase in matrix metalloproteinase (MMP)-9 and MMP-2 protein expression. Accompanied by markedly increased tissue inhibitors matrix metalloproteinase (TIMP)-2 and decreased TIMP-1, the balance of MMP2/TIMP-2 and MMP-9/TIMP-1 were disrupted. Ultimately, the receptivity of PEECs was destroyed by excessive Mo, which is revealed by the significant decrease of receptive marker molecules, including leukemia inhibitory factor (LIF), integrins β3 (ITGβ3), heparin-binding epidermal growth factor (HB-EGF), and vascular endothelial growth factor (VEGF). To sum up, the current study demonstrated the potential toxicity of Mo to PEECs, indicating reproductive toxicity at high Mo concentrations and suggesting that the content of Mo should be evaluated as a potential risk factor.

Dietary supplementation with N-acetyl-L-cysteine ameliorates hyperactivated ERK signaling in the endometrium that is linked to poor pregnancy outcomes following ovarian stimulation in pigs

BACKGROUND

Exogenous gonadotropin-controlled ovarian stimulation is the critical step in animal reproductive management, such as pig, sheep, bovine and other species. It helps synchronize ovulation or stimulate multiple ovulations. However, a number of evidence indicated an unexpected decrease in pregnancy outcomes following ovarian stimulation. This study aimed to explore the underlying mechanism of the pregnancy defect and develop a practical rescue strategy.

RESULTS

Compared with those in the control group, gilts that underwent ovarian stimulation showed a decrease in pregnancy rate, farrowing rate, and total number of piglets born. Stimulated gilts also showed an increase in estradiol (E2) levels. The supraphysiological E2 level was correlated with the decrease in the number of piglets born. Furthermore, we found that high levels of E2 impair uterine receptivity, as shown by the overproliferation of endometrial epithelial cells. In vitro mechanistic studies demonstrated that high levels of E2 hyperactivate FGF-FGFR-ERK signaling cascade in the uterine endometrium, and in turn induces overproliferation of endometrial epithelial cells. Of note, N-acetyl-L-cysteine (NAC) supplementation effectively inhibits ERK hyperphosphorylation and ameliorates endometrial epithelial overproliferation. Importantly, in vivo experiments indicated that dietary NAC supplementation, compared with ovarian stimulation group, improves the uterine receptivity in gilts, and significantly increases the pregnancy rate and total number of piglets born.

CONCLUSIONS

Ovarian stimulation-induced supraphysiological levels of E2 impairs uterine receptivity by hyperactivating FGF-FGFR-ERK signaling cascade, thereby reducing pregnancy rate and litter size. Supplementing NAC to a conventional diet for gilts ameliorates hyperactivated ERK signaling and improves uterine receptivity, thus rescuing adverse pregnancy outcomes following ovarian stimulation.

Metabolic pathways for glucose and fructose: I synthesis and metabolism of fructose by ovine conceptuses†

Fructose, the most abundant hexose sugar in fetal fluids and the blood of sheep and other ungulates and cetaceans, is synthesized from glucose via the polyol pathway in trophectoderm and chorion. However, the cell-specific and temporal expression of enzymes for the synthesis and metabolism of fructose in sheep conceptuses (embryo and placental membranes) and placentomes has not been characterized. This study characterized key enzymes involved in fructose synthesis and metabolism by ovine conceptuses throughout pregnancy. Day 17 conceptuses expressed mRNAs for the polyol pathway (SORD and AKR1B1) and glucose and fructose metabolism (HK1, HK2, G6PD, OGT, and FBP), but not those required for gluconeogenesis (G6Pase or PCK). Ovine placentomes also expressed mRNAs for SORD, AKR1B1, HK1, and OGT. Fructose can be metabolized via the ketohexokinase (KHK) pathway, and isoforms, KHK-A and KHK-C, were expressed in ovine conceptuses from Day 16 of pregnancy and placentomes during pregnancy in a cell-specific manner. The KHK-A protein was more abundant in the trophectoderm and cotyledons of placentomes, while KHK-C protein was more abundant in the endoderm of Day 16 conceptuses and the chorionic epithelium in placentomes. Expression of KHK mRNAs in placentomes was greatest at Day 30 of pregnancy (P < 0.05), but not different among days later in gestation. These results provide novel insights into the synthesis and metabolism of fructose via the uninhibited KHK pathway in ovine conceptuses to generate ATP via the tricarboxylic cycle, as well as substrates for the pentose cycle, hexosamine biosynthesis pathway, and one-carbon metabolism required for conceptus development throughout pregnancy.

Early Embryonic Development in Agriculturally Important Species

The fertilization of oocytes ovulated by pigs, sheep, cows, and horses is not considered a limiting factor in successful establishment of pregnancy. Pig, sheep, and cow embryos undergo cleavage to the blastocyst stage, hatch from the zona pellucida, and undergo central-type implantation. Hatched blastocysts of pigs, sheep, and cows transition from tubular to long filamentous forms to establish surface area for exchange of nutrients and gases with the uterus. The equine blastocyst, surrounded by external membranes, does not elongate but migrates throughout the uterine lumen before attaching to the uterine luminal epithelium (LE) to begin implantation. Pregnancy recognition signaling in pigs requires the trophectoderm to express interleukin 1 beta, estrogens, prostaglandin E2, and interferon gamma. Sheep and cow conceptus trophectoderm expresses interferon tau that induces interferon regulatory factor 2 that inhibits transcription of estrogen and oxytocin receptors by uterine epithelia. This prevents oxytocin-induced luteolytic pulses of prostaglandin F2-alpha from regressing the corpora lutea, as well as ensuring the secretion of progesterone required for maintenance of pregnancy. The pregnancy recognition signal produced by equine blastocysts is not known. Implantation in these species requires interactions between extracellular matrix (ECM) proteins and integrins as the conceptus undergoes apposition and firm attachment to the uterine LE. This review provides details with respect to early embryonic development and the transition from spherical to filamentous conceptuses in pigs, sheep, and cows, as well as pre-implantation development of equine blastocysts and implantation of the conceptuses.

Biosensor capability of the endometrium is mediated in part, by altered miRNA cargo from conceptus-derived extracellular vesicles

We tested the hypothesis that the biosensor capability of the endometrium is mediated in part, by the effect of different cargo contained in the extracellular vesicles secreted by the conceptus during the peri-implantation period of pregnancy. We transferred Bos taurus taurus embryos of different origin, in vivo (high developmental potential (IV)), in vitro (intermediate developmental potential (IVF)), or cloned (low developmental potential (NT)), into Bos taurus indicus recipients. Extracellular vesicles (EVs) recovered from Day 16 conceptus-conditioned medium were characterized and their microRNA (miRNA) cargo sequenced alongside RNA sequencing of their respective endometria. There were substantial differences in the endometrial response to in vivo versus in vitro and in vivo versus cloned conceptuses (1153 and 334DEGs respectively) with limited differences between in vitro Vs cloned conceptuses (36 DEGs). The miRNA cargo contained in conceptus-derived EVs was similar between all three groups (426 miRNA in common). Only 8 miRNAs were different between in vivo and cloned conceptuses, while only 6 miRNAs were different between in vivo and in vitro-derived conceptuses. Treatment of endometrial epithelial cells with mimic or inhibitors for miR-128 and miR-1298 changed the proteomic content of target cells (96 and 85, respectively) of which mRNAs are altered in the endometrium in vivo (PLXDC2, COPG1, HSPA12A, MCM5, TBL1XR1, and TTF). In conclusion, we have determined that the biosensor capability of the endometrium is mediated in part, by its response to different EVs miRNA cargo produced by the conceptus during the peri-implantation period of pregnancy.

Mechanisms of female reproductive toxicity in pigs induced by exposure to environmental pollutants

Environmental pollutants, including endocrine disruptors, heavy metals, nanomaterials, and pesticides, have been detected in various ecosystems and are of growing global concern. The potential for toxicity to non-target organisms has consistently been raised and is being studied using various animal models. In this review, we focus on pesticides frequently detected in the environment and investigate their potential exposure to livestock. Owing to the reproductive similarities between humans and pigs, various in vitro porcine models, such as porcine oocytes, trophectoderm cells, and luminal epithelial cells, are used to verify reproductive toxicity. These cell lines are being used to study the toxic mechanisms induced by various environmental toxicants, including organophosphate insecticides, pyrethroid insecticides, dinitroaniline herbicides, and diphenyl ether herbicides, which persist in the environment and threaten livestock health. Collectively, these results indicate that these pesticides can induce female reproductive toxicity in pigs and suggest the possibility of adverse effects on other livestock species. These results also indicate possible reproductive toxicity in humans, which requires further investigation.

Expression of circulating oar-miR-485-5p and oar-miR-493-5p during the estrous cycle and early pregnancy in ovine plasma

In the current study, we aimed to assess the expression levels of two circulating microRNAs (miRNA) (oar-miR-485-5p and oar-miR-493-5p) in the ovine plasma during the peri-implantation. After mating, we collected the plasma samples from a total of 8 ewes on day 22 of pregnancy (P22; n = 4) and day 22 of the estrous cycle (C22; n=4). We used mature miRNA sequences for oar-miR-485-5p and oar-miR-493-5p out of one hundred fifty, which were retrieved from our microarray results of previous study. We showed that the miRNA expression of oar-miR-485-5p and oar-miR-493-5p were upregulated in P22 (P<0.05) when compared to C22. Those two miRNAs targeted 311 target genes in the peri-implantation period of pregnancy. Furthermore, we revealed 151 GO/pathway terms in biological process (BP) and 25 GO/pathway terms in molecular function (MF), while we demonstrated 13 GO/pathway terms in cellular component (CC). We revealed three hub genes as interleukin 2 (IL2), interleukin 18 (IL18), and C-X-C Motif Chemokine Ligand 10 (CXCL10). In conclusion, both miR-485-5p and oar-miR-493-5p have the potential to be a biomarker to understand peri-implantation of the ovine pregnancy in the aspect of pregnancy-reflected changes in maternal plasma.

Progesterone Activates the Histone Lactylation-Hif1α-glycolysis Feedback Loop to Promote Decidualization

Decidualization is a progesterone-dependent cellular differentiation process that is essential for establishing pregnancy. Robust activation of glycolysis and lactate synthesis during decidualization is remarkable, but their developmental functions remain largely unknown. Herein, we identify that endometrial lactate production plays a critical role in establishing local histone lactylation, a newly identified histone modification, and is important for ensuring normal decidualization. Enhanced endometrial glycolysis is the hallmark metabolic change and is tightly coupled with H4K12la during decidualization. Inhibition of histone lactylation impaired decidualization, in either physiological conception or in vivo and in vitro induced decidualization models. Mechanistic study based on CUT&Tag and ATAC-seq revealed that a transcriptional factor hypoxia-inducible factor 1 α (Hif1α) is the critical regulatory target of H4K12la, and in turn forms an H4K12la-Hif1α-glycolysis feedback loop to drive decidualization. Moreover, we demonstrate that the loop is directly activated by progesterone during decidualization. Our study not only advances the current knowledge of the role of lactate in regulating uterine function, but also establishes a novel functional link among the major endocrine factors, endometrial metabolic change, and epigenetic modification during endometrial remodeling. These findings present valuable clues to develop clinical intervention strategies to improve pregnancy outcomes following both natural conception and assisted reproduction.

Chemerin affects the expression of angiogenesis-related factors in the porcine endometrium during early pregnancy and the oestrous cycle: an in vitro study

CONTEXT

The appropriate course of angiogenesis in the endometrium is crucial for pregnancy establishment and maintenance. Very little is known about the factors linking vessel formation and immune system functioning.

AIMS

We hypothesised that chemerin, an adipokine known for its involvement in the regulation of energy balance and immunological functions, may act as a potent regulator of endometrial angiogenesis during early pregnancy in pigs.

METHODS

Porcine endometrial tissue explants were obtained from pregnant pigs on days 10-11, 12-13, 15-16 and 27-28, and on days 10-12 of the oestrous cycle. The explants were in vitro cultured for 24h in the presence of chemerin (100, 200ng/mL) or in medium alone (control). We evaluated the in vitro effect of chemerin on the secretion of vascular endothelial growth factors A-D (VEGF-A-D), placental growth factor (PlGF), basic fibroblast growth factor (bFGF) and angiopoietin 1 and 2 (ANG-1, ANG-2) with the ELISA method. The protein abundance of angiogenesis-related factor receptors, VEGF receptors 1-3 (VEGFR1-3), FGF receptors 1 and 2 (FGFR1-2) and ANG receptor (TIE2) was evaluated with the Western blot (WB) method. We also analysed the influence of chemerin on the phosphorylation of AMPK using WB.

KEY RESULTS

We found that in the studied endometrial samples, chemerin up-regulated the secretion of VEGF-A, VEGF-B and PlGF, and protein expression of VEGFR3. The adipokine caused a decrease in VEGF-C, VEGF-D and ANG-1 release. Chemerin effect on bFGF and ANG-2 secretion, and protein content of VEGFR1, VEGFR2, FGFR1, FGFR2 and TIE2 were dependent on the stage of pregnancy. Chemerin was found to down-regulate AMPK phosphorylation.

CONCLUSIONS

The obtained in vitro results suggest that chemerin could be an important factor in the early pregnant uterus by its influence on angiogenic factors' secretion and signalling.

IMPLICATIONS

The obtained results on the role of chemerin in the process of endometrial angiogenesis may, in the long term perspective, contribute to the elaboration of more effective methods of modifying reproductive processes and maintaining energy homeostasis in farm animals.

Butyrate Improves Porcine Endometrial Epithelial Cell Receptivity via Enhancing Acetylation of Histone H3K9

SCOPE

Uterine receptivity is a major restriction of embryo implantation and survival, and the endometrial luminal epithelium serves as the transient gateway for uterine receptivity and embryo implantation. Butyrate is reported to promote the success of embryo implantation, but the effects and mechanism of butyrate on uterine receptivity are still unknown.

METHODS AND RESULTS

Porcine endometrial epithelial cells (PEECs) are used as a model, and the cellular receptivity changes, metabolism, and gene expression profiles influenced by butyrate are analyzed. The study finds that butyrate improves receptive changes in PEECs, including inhibiting proliferation, exhibiting more pinocytosis on the cell surface, and increasing adhesiveness to porcine trophoblast cells. In addition, butyrate increases prostaglandin synthesis and markedly impacts purine metabolism, pyrimidine metabolism, and the FoxO signaling pathway. siRNA to inhibit the expression of FoxO1 and chromatin immunoprecipitation-sequencing (ChIP-seq) of H3K9ac are used to demonstrate that the H3K9ac/FoxO1/PCNA pathway can contribute to the effects of cell proliferation inhibition and uterine receptivity improvement induced by butyrate.

CONCLUSION

The findings reveal that butyrate improves endometrial epithelial cell receptivity by enhancing the acetylation of histone H3K9, which shows nutritional regulation and therapeutic potential for poor uterine receptivity and difficulty in embryo implantation.

Creatine metabolism at the uterine-placental interface throughout gestation in sheep†

The placenta requires high levels of adenosine triphosphate to maintain a metabolically active state throughout gestation. The creatine-creatine kinase-phosphocreatine system is known to buffer adenosine triphosphate levels; however, the role(s) creatine-creatine kinase-phosphocreatine system plays in uterine and placental metabolism throughout gestation is poorly understood. In this study, Suffolk ewes were ovariohysterectomized on Days 30, 50, 70, 90, 110 and 125 of gestation (n = 3-5 ewes/per day, except n = 2 on Day 50) and uterine and placental tissues subjected to analyses to measure metabolites, mRNAs, and proteins related to the creatine-creatine kinase-phosphocreatine system. Day of gestation affected concentrations and total amounts of guanidinoacetate and creatine in maternal plasma, amniotic fluid and allantoic fluid (P < 0.05). Expression of mRNAs for arginine:glycine amidinotransferase, guanidinoacetate methyltransferase, creatine kinase B, and solute carrier 16A12 in endometria and for arginine:glycine amidinotransferase and creatine kinase B in placentomes changed significantly across days of gestation (P < 0.05). The arginine:glycine amidinotransferase protein was more abundant in uterine luminal epithelium on Days 90 and 125 compared to Days 30 and 50 (P < 0.01). The chorionic epithelium of placentomes expressed guanidinoacetate methyltransferase and solute carrier 6A13 throughout gestation. Creatine transporter (solute carrier 6A8) was expressed by the uterine luminal epithelium and trophectoderm of placentomes throughout gestation. Creatine kinase (creatine kinase B and CKMT1) proteins were localized primarily to the uterine luminal epithelium and to the placental chorionic epithelium of placentomes throughout gestation. Collectively, these results demonstrate cell-specific and temporal regulation of components of the creatine-creatine kinase-phosphocreatine system that likely influence energy homeostasis for fetal-placental development.

Dietary supplementation with L-citrulline improves placental angiogenesis and embryonic survival in gilts

This study was conducted with gilts as an animal model to test the hypothesis that dietary supplementation with L-citrulline (Cit) improves placental angiogenesis and embryonic survival. Between Days 14 and 25 of gestation, each gilt was fed a corn- and soybean-meal-based diet (2 kg/day) supplemented with 0.4% Cit or an isonitrogenous amount of L-alanine (Control). On Day 25 of gestation, gilts were hysterectomized to obtain conceptuses. Amniotic and allantoic fluids and placentae were analyzed for NOx [stable oxidation products of nitric oxide (NO)], polyamines, and amino acids (AAs). Placentae were also analyzed for syntheses of NO and polyamines; concentrations of AAs and related metabolites; and the expression of angiogenic factors and aquaporins (AQPs). Compared to the control group, Cit supplementation increased (P < 0.01) the number of viable fetuses by 2.0 per litter, the number and diameter of placental blood vessels (21% and 24%, respectively), placental weight (15%), and total allantoic and amniotic fluid volumes (20% and 47%, respectively). Cit supplementation also increased (P < 0.01) enzymatic activities of GTP-cyclohydrolase-1 (32%) and ornithine decarboxylase (27%) in placentae; syntheses of NO (29%) and polyamines (26%); concentrations of NOx (19%), tetrahydrobiopterin (28%), polyamines (22%), cAMP (26%), and cGMP (24%) in placentae; total amounts of NOx (22-40%), polyamines (23-40%), AAs (16-255%), glucose (22-44%), and fructose (22-43%) in allantoic and amniotic fluids. Furthermore, Cit supplementation increased (P < 0.05) placental mRNA levels for angiogenic factors (eNOS [84%], GTP-CH1 [55%], PGF [61%], VEGFA120 [26%], and VEGFR2 [137%], as well as AQPs - AQP1 [105%], AQP3 [53%], AQP5 [77%], AQP8 [57%], and AQP9 [31%]). Collectively, dietary Cit supplementation enhanced placental NO and polyamine syntheses as well as angiogenesis to improve conceptus development and survival.

Impaired luteal progesterone synthesis observed in gilts with PMSG/hCG-induced estrus affects the expression of steroid, prostaglandin, and cytokine receptors in the endometrium and myometrium during the peri-implantation period

The present study aimed to examine the effect of impaired progesterone (P4) synthesis, observed in gilts with gonadotropin-induced estrus, on the uterine expression of receptors important for pregnancy establishment. Twenty prepubertal gilts received 750 IU PMSG and 500 IU hCG 72 h later, while 18 prepubertal gilts in the control group were observed daily for estrus behavior. Gilts were inseminated in their first estrus and slaughtered on days 10, 12, and 15 of pregnancy to collect endometrial and myometrial tissues for mRNA analysis using real-time PCR. As we previously described, gilts with PMSG/hCG-induced estrus showed decreased luteal P4 synthesis on days 10 and 12 of pregnancy. PMSG/hCG treatment did not affect P4 receptor mRNA expression in either uterine tissue. In the endometrium, a greater mRNA transcript abundance of estrogen receptors (ESR1 and ESR2), androgen receptor (AR), prostaglandin (PG) E2 receptors (PTGER2 and PTGER4), PGF2α receptor (PTGFR), interleukin 6 receptor (IL6R), and tumor necrosis factor α receptors (TNFRSF1A and TNFRSF1B) was detected in gilts with natural than with PMSG/hCG-induced estrus (P<0.05). In the myometrium, the mRNA expression of AR, PTGER2, and PTGFR was lower, while PGI2 receptor (PTGIR) transcript abundance was elevated in the gilts treated with PMSG/hCG as compared with the control animals (P<0.05). In summary, a decreased luteal P4 level during the peri-implantation period in gonadotropin-stimulated pigs affects endometrial and myometrial receptor expression, with the endometrium being more sensitive to impaired P4 synthesis. Whether the observed changes alter uterine receptivity to local and systemic factors remains to be elucidated.

Dietary adenosine supplementation improves placental angiogenesis in IUGR piglets by up-regulating adenosine A2a receptor

Abnormal placental angiogenesis is associated with the occurrence of intrauterine growth restriction (IUGR) in piglets, and effective treatment strategies against this occurrence remain to be explored. Adenosine has been reported to play an important role in angiogenesis, but its role in placental angiogenesis is still unknown. Here, we investigated the effect of dietary adenosine supplementation on IUGR occurrence in piglets by analyzing the role of adenosine in placental angiogenesis for Normal and IUGR piglets. Specifically, 88 sows were allotted to 2 treatments (n = 44) and fed a basal diet supplemented with 0% or 0.1% of adenosine from day 65 of gestation until farrowing, followed by collecting the placental samples of Normal and IUGR piglets, and recording their characteristics. The results showed that adenosine supplementation increased the mean birth weight of piglets (P < 0.05) and placental efficiency (P < 0.05), while decreasing the IUGR piglet rate (P < 0.05). Expectedly, the placenta for IUGR neonates showed a down-regulated vascular density (P < 0.05) and angiogenesis as evidenced by the expression level of vascular cell adhesion molecule-1 (VCAM1) (P < 0.05). Notably, dietary adenosine supplementation promoted angiogenesis (P < 0.05) both in the Normal and IUGR placenta. More importantly, the expression level of adenosine A2a receptor (ADORA2A) was lower (P < 0.05) in the IUGR placenta than in Normal placenta, whereas adenosine treatment could significantly increase ADORA2A expression, and also had an interaction effect between factors IUGR and Ado. Collectively, placentae for IUGR piglets showed impaired angiogenesis and down-regulated expression level of ADORA2A, while dietary adenosine supplementation could activate ADORA2A expression, improve the placental angiogenesis, and ultimately decrease the occurrence of IUGR in piglets.

Fetal and placental development in early gestation of hyper-prolific sows

Modern hyper-prolific sows produce large litters with a high within-litter variation in birth weight and an increased number of low-birth-weight piglets per litter with higher mortality rates and lower growth rates compared to heavier littermates. This study aimed to describe fetal development in hyper-prolific sows, to characterize differences between large and small fetuses, and to determine when within-litter variation in fetal weight can be detected. Forty-seven multiparous sows were blood-sampled and slaughtered at day 28, 33, 45, 50, and 56 of gestation. Number of fetuses were counted, fetal body and organ weights were measured, and the intrauterine positioning was recorded. Length, width, and area of each placenta was measured and the fetus weight/placental weight ratio was calculated. The umbilical cords of the smallest, medium and the largest fetus of each litter were sampled for histological analysis. In total measurements were obtained for 1161 fetuses. The results revealed no difference in fetal survival between the gestational days (P > 0.05). Intrauterine positioning near the cervix significantly reduced fetal weight at day 56 (P < 0.05). Total litter weight and average fetal weight increased with gestational age and individual fetal weight was negatively affected by litter size from day 33 and onwards (P < 0.05). The coefficient of variation for within-litter variation in fetal weight was higher at day 28 compared to the other gestational days (P < 0.05). Relative brain- and heart weights decreased from day 28-56 (P < 0.001). Small fetuses had relatively heavier brains and hearts at day 45, 50 and 56 (P < 0.001). Size of placenta, fetus weight/placental weight ratio and length of umbilical cord increased with gestational age (P < 0.001). There was a positive correlation between size of placenta and weight of individual fetus (P < 0.001), the weight of the fetus was positively correlated with umbilical cord length (P < 0.001) and the umbilical cross-sectional area was correlated to fetal weight at day 56 (P < 0.01). Individual fetal weight was positively correlated to the fetus weight/placental weight ratio (P < 0.001). In conclusion, fetal growth was affected by litter size, placental weight, and -area, and umbilical cord length. Lightweight fetuses were characterized by having placentas with lower weight and area and shorter umbilical cords. Lastly, within-litter variation in fetal weight was detectable at day 28, and the coefficient of variance remained stable from day 33-56.

Integrins and ligands, are correlated at pig placental interface during pregnancy?

In the present work, we emphasize the studies about integrins and their receptors in pig placental interface at different times of gestation. Uterine placental interface (n=24) of 17-, 30-, 60- and 70-days gestation (dg) and non-pregnant uterus (n=4) of crossbred sows were used. The presence of αvβ3 and α5β1 integrins, and their ligands fibronectin (FN), and osteopontin (OPN) were detected by immunohistochemistry, and the immunolabelled area percentage (IAP) and the optical density (OD) were determined. The integrins and its ligands analyzed have presented peaks of expression in early and mid-gestation, both in IAP and the OD area decreasing at 70 dg. These temporal changes showed us that the molecules studied in this work participate in embryo/feto-maternal attachment, variably. Besides, we found a significant correlation both in the intensity and in the extension of immunostaining for trophoblastic FN and endometrial αvβ3, and trophoblastic OPN and endometrial α5β1, throughout the entire pig pregnancy. At late gestation, take place a notable placental remodelation with subsequent removal or renewal of folds at the uterine-placental interface that results in the loss of focal adhesions. The decrease of the expression of some integrins and their ligands in late gestation, particularly at 70 dg, would demonstrate that there would be other adhesion molecules and other ligands that could be participating in the establishment of the maternal-fetal interface.

Integrated analysis of transcriptome and metabolome revealed biological basis of sows from estrus to lactation

Characterization of molecular mechanisms underlying pregnancy development of sows is important for the genetic improvement of pig breeding traits, and also provides resources for biomedical research on human pregnancy diseases. However, the transcriptome and metabolome across multiple developmental stages of sow pregnancy were still lacking. In this study, we obtained 84 distinct RNA sequencing and 42 metabolome datasets of pig blood across six development stages from estrus to lactation. We confirmed the initial sequence and exonic structural features, stage-specific molecules, expression or accumulation pattern of molecules, the regulatory mechanism of transcriptome and metabolome, and important pregnancy-related metabolites both in pigs and humans. In conclusion, we proposed the key differences among the stages of sows from estrus to lactation in RNAs and metabolites and put forward key markers. These data results were expected to provide essential resources for pig breeding and biomedical research on human pregnancy disease.

Dietary supplementation with 0.4% L-arginine between days 14 and 30 of gestation enhances NO and polyamine syntheses and water transport in porcine placentae

BACKGROUND

Most embryonic loss in pigs occurs before d 30 of gestation. Dietary supplementation with L-arginine (Arg) during early gestation can enhance the survival and development of conceptuses (embryo/fetus and its extra-embryonic membranes) in gilts. However, the underlying mechanisms remain largely unknown.

METHODS

Between d 14 and 30 of gestation, each gilt was fed daily 2 kg of a corn- and soybean-meal based diet (12% crude protein) supplemented with either 0.4% Arg (as Arg-HCl) or an isonitrogenous amount of L-alanine (Control). There were 10 gilts per treatment group. On d 30 of gestation, gilts were fed either Arg-HCl or L-alanine 30 min before they were hysterectomized, followed by the collection of placentae, embryos, fetal membranes, and fetal fluids. Amniotic and allantoic fluids were analyzed for nitrite and nitrate [NOx; stable oxidation products of nitric oxide (NO)], polyamines, and amino acids. Placentae were analyzed for syntheses of NO and polyamines, water and amino acid transport, concentrations of amino acid-related metabolites, and the expression of angiogenic factors and aquaporins (AQPs).

RESULTS

Compared to the control group, Arg supplementation increased (P < 0.05) the number of viable fetuses by 1.9 per litter, the number and diameter of placental blood vessels (+ 25.9% and + 17.0% respectively), embryonic survival (+ 18.5%), total placental weight (+ 36.5%), the total weight of viable fetuses (+ 33.5%), fetal crown-to-rump length (+ 4.7%), and total allantoic and amniotic fluid volumes (+ 44.6% and + 75.5% respectively). Compared to control gilts, Arg supplementation increased (P < 0.05) placental activities of GTP cyclohydrolase-1 (+ 33.1%) and ornithine decarboxylase (+ 29.3%); placental syntheses of NO (+ 26.2%) and polyamines (+ 28.9%); placental concentrations of NOx (+ 22.5%), tetrahydrobiopterin (+ 21.1%), polyamines (+ 20.4%), cAMP (+ 27.7%), and cGMP (+ 24.7%); total amounts of NOx (+ 61.7% to + 96.8%), polyamines (+ 60.7% to + 88.7%), amino acids (+ 39% to + 118%), glucose (+ 60.5% to + 62.6%), and fructose (+ 41.4% to + 57.0%) in fetal fluids; and the placental transport of water (+ 33.9%), Arg (+ 78.4%), glutamine (+ 89.9%), and glycine (+ 89.6%). Furthermore, Arg supplementation increased (P < 0.05) placental mRNA levels for angiogenic factors [VEGFA120 (+ 117%), VEGFR1 (+ 445%), VEGFR2 (+ 373%), PGF (+ 197%), and GCH1 (+ 126%)] and AQPs [AQP1 (+ 280%), AQP3 (+ 137%), AQP5 (+ 172%), AQP8 (+ 165%), and AQP9 (+ 127%)].

CONCLUSION

Supplementing 0.4% Arg to a conventional diet for gilts between d 14 and d 30 of gestation enhanced placental NO and polyamine syntheses, angiogenesis, and water and amino acid transport to improve conceptus development and survival.

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.

Prostacyclin Synthesis and Prostacyclin Receptor Expression in the Porcine Myometrium: Prostacyclin Potential to Regulate Fatty Acid Transporters, Cytokines and Contractility-Related Factors

Simple Summary

Prostacyclin (prostaglandin I2; PGI2) is an important modulator of vascular functions and is involved in various reproductive processes. PGI2 was also described as a modulator of uterine contractility in several species, including the pig. However, its synthesis and role in the myometrium of the porcine uterus are still not fully described. The objective of this study was to evaluate profiles of PGI2 synthesis and PGI2 receptor expression in the myometrium of gilts throughout the estrous cycle and during early pregnancy and to investigate the in vitro effect of PGI2 on the mRNA expression of factors engaged in smooth muscle contraction, nutrient transport, prostaglandin synthesis and action, and inflammatory response. The obtained results showed that the synthesis of PGI2 changes in the myometrium of pigs during both the estrous cycle and early pregnancy, resulting in much greater concentrations of PGI2 in cyclic than in pregnant gilts. Moreover, PGI2 stimulated the expression of fatty acid transporters and contractility-related calponin 1 and caldesmon 1, whereas it decreased cytokine expression. This study indicates that PGI2 may participate in the regulation of myometrial functions modulating the availability of factors involved in smooth muscle activity and inflammatory reaction in the uterus of pigs.

Abstract

Although prostacyclin (PGI2) has been well described as a regulator of smooth muscle activity, limited data are available concerning its role in the myometrium of pigs. The present research aimed to examine profiles of PGI2 synthase (PTGIS) and PGI2 receptor (PTGIR) expression and 6-keto PGF1α (a PGI2 metabolite) concentrations in the myometrium of gilts throughout the estrous cycle and during early pregnancy using qPCR, Western blot, and/or ELISA methods. Furthermore, myometrial explants were exposed to iloprost (a stable PGI2 analog) to investigate the effect of PGI2 on the mRNA expression of factors engaged in smooth muscle contraction, nutrient transport, prostaglandin synthesis and action, and inflammatory response. PTGIS mRNA expression was greater in cyclic than in pregnant gilts on days 11–12 after estrus and was accompanied by greater concentrations of 6-keto PGF1α detected in cyclic than in pregnant animals on days 11–20. Iloprost stimulated fatty acid transporters and contractility-related calponin 1 and caldesmon 1 mRNA expression and decreased interleukin 1β and tumor necrosis factor transcript abundance. The obtained results indicate a physiologically relevant role of PGI2 during the estrous cycle in the porcine myometrium with its importance for regulating the expression of contractility-, nutrient transport- and inflammatory response-related factors.

Circulating miRNAs in maternal plasma as potential biomarkers of early pregnancy in sheep

MicroRNA (miRNA) plays an important role in the control of gene expression and is implied in many biological functions, including embryo implantation and development. The aim was to assess plasma miRNA profiles during the peri-implantation and ascertain potential candidate miRNA markers for early pregnancy diagnosis in ovine plasma. The plasma samples were obtained from a total of 24 ewes on days 12 (pre-implantation; P12, n = 4), 16 (implantation; P16, n = 4) and 22 (post-implantation; P22, n = 4) after mating, and on their corresponding days of 12 (Pre-C; C12, n = 4), 16 (Imp-C; C16, n = 4) and 22 (Post-C; C22, n = 4) of the estrous cycle. The miRNA profiles in plasma were assessed by microarray technology. We detected the presence of 60 ovine-specific miRNAs in plasma samples. Of these miRNAs, 22 demonstrated a differential expression pattern, especially between the estrous cycle and early pregnancy, and targeted 521 genes. Two miRNAs (oar-miR-218a and oar-miR-1185-3p) were confirmed using RT-qPCR in the ovine plasma samples. Protein-protein interaction (PPI) network of target genes established six functional modules, of which modules 1 and 3 were enriched in the common GO terms, such as inflammatory response, defense response, and regulation of immune response. In contrast, module 2 was enriched in the developmental process involved in reproduction, embryo development, embryonic morphogenesis, and regulation of the developmental process. The results indicate that miRNAs profiles of plasma seemed to be modulated during the peri-implantation stage of pregnancy in ewes. Circulating miRNAs could be promising candidates for diagnosis in early ovine pregnancy.

Integrated Analysis of mRNAs and Long Non-Coding RNAs Expression of Oviduct That Provides Novel Insights into the Prolificacy Mechanism of Goat (Capra hircus)

Artificial directional selection has replaced natural selection and resulted in trait differences across breeds in domestic animal breeding. However, the molecular mechanism by which the oviduct regulates litter size remains largely elusive in goats during the follicular phase. Accumulating data have linked lncRNAs to reproductive activities; however, little is known about the modulation mechanism in the oviduct. Herein, RNA-seq was used to measure mRNA and lncRNA expression levels in low- and high-fecundity goats. We observed distinctive differences in mRNA and lncRNA in terms of different kidding numbers and detected the differential expression of 1640 mRNA transcripts and 271 lncRNA transcripts. Enrichment analysis of differentially expressed mRNAs (DEGs) suggested that multiple pathways, such as the AMPK, PI3K–Akt, calcium signaling pathway, oocyte meiosis, ABC transporter, and ECM–receptor interaction pathways, directly or indirectly affected goat reproduction. Additionally, coexpression of differentially expressed lncRNAs (DEL)-genes analysis showed that XLOC_021615, XLOC_119780, and XLOC_076450 were trans-acting as the DEGs ATAD2, DEPDC5, and TRPM6, respectively, and could regulate embryo development. Moreover, XLOC_020079, XLOC_107361, XLOC_169844, XLOC_252348 were the trans-regulated elements of the DEGs ARHGEF2 and RAPGEF6, and the target DEGs CPEB3 of XLOC_089239, XLOC_090063, XLOC_107409, XLOC_153574, XLOC_211271, XLOC_251687 were associated with prolificacy. Collectively, our study has offered a thorough dissection of the oviduct lncRNA and mRNA landscapes in goats. These results could serve as potential targets of the oviduct affecting fertility in goats.

Within- and between-Breed Selection Signatures in the Original and Improved Valachian Sheep

This study explored the genomic diversity and selection signatures in two Slovakian national breeds, the Original Valachian and the Improved Valachian sheep. As they are an important animal genetic resource within the country, but with decreasing population size, our aim is to identify potentially valuable genomic regions. A total of 97 sheep (18 male and 79 female) from the Original Valachian, and 69 sheep (25 male and 44 female) from the Improved Valachian populations were genotyped using the GeneSeek GGP Ovine 50 K chip. The inbreeding levels were assessed with runs of homozygosity (ROH). The selection signatures within breeds were identified based on the top 1% of most homozygous regions within the breed, the so-called ROH islands. The selection signatures between breeds were assessed based on variance in linkage disequilibrium. Overall, we have identified selection signatures with quantitative trait loci (QTL) and genes pointing towards all three production purposes of the Valachian sheep, milk, meat, and wool, including their quality characteristics. Another group with apparent large importance was the various traits related to health and resistance to parasites, which is well in line with the sturdy nature of this breed.

Bovine Animal Model for Studying the Maternal Microbiome, in utero Microbial Colonization and Their Role in Offspring Development and Fetal Programming

Recent developments call for further research on the timing and mechanisms involved in the initial colonization of the fetal/infant gut by the maternal microbiome and its role in Developmental Origins of Health and Disease (DOHaD). Although progress has been made using primarily preterm infants, ethical and legal constraints hinder research progress in embryo/fetal-related research and understanding the developmental and mechanistic roles of the maternal microbiome in fetal microbial imprinting and its long-term role in early-life microbiome development. Rodent models have proven very good for studying the role of the maternal microbiome in fetal programming. However, some inherent limitations in these animal models make it challenging to study perinatal microbial colonization from a biomedical standpoint. In this review, we discuss the potential use of bovine animals as a biomedical model to study the maternal microbiome, in utero microbial colonization of the fetal gut, and their impact on offspring development and DOHaD.

Effects of dietary supplementation with N-carbamylglutamate on maternal endometrium and fetal development during early pregnancy in Inner Mongolia white cashmere goats

This study investigated the effects of dietary supplementation with N-carbamylglutamate (NCG) on maternal endometrium and fetal development during early pregnancy of Inner Mongolia white cashmere goats. Forty-eight pregnant Inner Mongolia white cashmere goats (average age 3 years old, average lactation parity 2, and average body weight 43.81 ± 2.66 kg) were randomly allocated to three groups: a basal diet (control group, n = 16), a basal diet plus 0.30-g NCG/d (NCG1 group, n = 16), and a basal diet plus 0.40-g NCG/d (NCG2 group, n = 16). All of the does were housed in individual pens and the NCG treatment was conducted from Days 0 to 90 of pregnancy. At Days 17 and 90 of pregnancy, six representative pregnant does in each group were slaughtered. The current study results demonstrated that maternal NCG administration during early pregnancy effectively increased the arginine family of amino acids and the glucogenic amino acids concentrations and promoted the mRNA expression of osteopontin (OPN), αv and β3 integrins, and endometrial development of Inner Mongolia white cashmere goats. The supplementation improved the fetal brown adipose tissue (BAT) stores and the mRNA expression of UCP-1 and BMP7, thereby helping to the fetal early development.

Integrated multiple transcriptomes in oviductal tissue across the porcine estrous cycle reveal functional roles in oocyte maturation and transport

Understanding the changes in the swine female reproductive system is important for solving issues related to reproductive failure and litter size. Elucidating the regulatory mechanisms of the natural estrous cycle in the oviduct under non-fertilisation conditions can improve our understanding of its role in the reproductive system. Herein, whole transcriptome RNA sequencing of oviduct tissue samples was performed. The differentially expressed genes (DEGs) were identified for each time point relative to day 0 and classified into three clusters based on their expression patterns. Clusters 1 and 2 included genes involved in the physiological changes through the estrous cycle. Cluster 1 genes were mainly involved in PI3K-Akt signaling and steroid hormone biosynthesis pathways. Cluster 2 genes were involved in extracellular matrix-receptor interactions and protein digestion pathways. In Cluster 3, the DEGs were downregulated in the luteal phase; they were strongly associated with cell cycle, calcium signaling, and oocyte meiosis. The gene expression in the oviduct during the estrous cycle influenced oocyte transport and fertilization. Our findings provide a basis for successfully breeding pigs and elucidating the mechanisms underlying the changes in the pig oviduct during the estrous cycle.

Porcine uterine luminal fluid-derived extracellular vesicles improve conceptus-endometrial interaction during implantation

Successful implantation of porcine conceptus requires synergistic interaction with various signal molecules in the maternal uterus. Extracellular vesicles (EVs) in uterine luminal fluid (ULF) of mice play important roles in conceptus development. However, studies have not explored the roles of extracellular vesicles (EV) in ULF of pigs. The aim of this study was to identify characteristics, origin, and roles of ULF-derived EVs on day 9 of the estrous cycle and on day 9,12 and 15 of pregnancy in pigs. Western blot, BCA assay and HE staining analysis showed increase in EVs concentration in ULF began from day 12 of pregnancy. Immunofluorescence staining and transmission electron microscopy analysis showed that EVs were mainly derived from endometrial epithelial cells. Fluorescent labeling, CCK-8 and transwell migration assays showed that these EVs were delivered to the trophoblast or parthenogenetic activation embryos to regulate proliferation and migration of trophoblast cells. A total of 305 miRNAs were identified using small RNA sequencing analysis. Functional enrichment analysis showed that miRNAs in these EVs potentially play vital regulatory functions in EV transportation or conceptus implantation. QRT-PCR analysis was used to further verify the RNA-seq data. The findings of this study provide information on the functions of porcine ULF-derived EVs and provide a reference dataset for future translational studies on porcine ULF-derived EVs.

Plane of nutrition and FSH-induced superovulation affect the expression of steroid hormone receptors and growth factors in caruncular tissue of non-pregnant sheep

Implantation is a critical step in the establishment of pregnancy and an important part of embryo-maternal contact. Uterine receptivity can be affected by changes in body condition and the maternal endocrine milieu, including those caused by the use of exogenous gonadotropins in controlled ovarian hyperstimulation to induce the development of multiple follicles. This study demonstrates the effects of FSH-mediated ovarian hyperstimulation on the caruncles of ewes under various feeding regimes. Sheep were classified into 3 categories: control fed (CF), overfed (OF), or underfed (UF). In each group, animals were superovulated with FSH or injected with a saline solution (non-treated control). Uterine caruncles were collected at the early (d 5) and mid-luteal phase (d 10) of the estrous cycle. The transcript levels of steroid hormone receptors (ESR1, ESR2, PGR) and growth factors (IGF1, IGF2, VEGFA) were investigated and their expression localized by immunohistochemical staining. As for the main findings, day of the estrous cycle affected expression of ESR1, IGF1 and IGF2, but not of ESR2, PGR and VEGFA; both feeding and superovulation had modulatory effects, with feeding (UF/OF) stimulating expression of all genes studied, and superovulation altering expression of some genes, eg IGF1, PGR and ESR1 and ESR2, in CF animals. Similarly, feeding (UF/OF) altered responsiveness to superovulation for PGR on d 5 and ESR1/ESR2 on d 5 and/or 10. Our data emphasize possible effects of dietary and/or hormonal stimuli on uterine physiology, which may affect pregnancy outcomes by disrupting uterine functionality.

l-Argine regulates the proliferation, apoptosis and endocrine activity by alleviating oxidative stress in sheep endometrial epithelial cells

l-arginine (L-Arg) is a semiessential amino acid that plays crucial roles in the reproductive performance of animals. This research aimed to investigate the effect of supplementing L-Arg on endometrial epithelial cells (EECs) of Hu sheep. In vivo, female Hu sheep were randomly divided into three groups: control group (n = 5), nutrient-restricted group (n = 5), and L-Arg supplemented nutrient-restricted group (n = 5). Then, the effect of L-Arg on ovine endometrial growth and antioxidant capacity was assessed. We found that L-Arg supplementation promoted the growth of endometrial ductal gland invaginations (DGI), and alleviated oxidative stress in nutrient-restricted sheep. In order to investigate its mechanism, a H₂O₂-induced EECs oxidative stress model was established, and roles of L-Arg in EECs oxidation resistance, proliferation, apoptosis and endocrine activity were studied in vitro. Our results showed that L-Arg markedly decreased the release of reactive oxygen species (ROS) and malonaldehyde (MDA), and enhanced the expression and activity of certain antioxidant enzymes in EECs challenged by the H₂O₂ (p < 0.05). Supplementation of L-Arg significantly reduced the effect of 200 μM H₂O₂ on the viability of EECs (p < 0.05). In addition, EECs treated with L-Arg significantly alleviated the G0/G1-phase cell cycle arrest, apoptosis, and the inhibition of endometrial growth factors expression caused by H₂O₂ (p < 0.05). Overall, the results demonstrate that L-Arg performs crucial roles in maintaining the proliferation of ovine EECs, endocrine activity and inhibiting apoptosis through reducing oxidative stress. This study offers a theoretical basis for using L-Arg to improve sheep the uterine function.

A Role for Fructose Metabolism in Development of Sheep and Pig Conceptuses

The period of conceptus (embryo and extraembryonic membrane) development between fertilization and implantation in mammalian species is critical as it sets the stage for placental and fetal development. The trophectoderm and endoderm of pre-implantation ovine and porcine conceptuses undergo elongation, which requires rapid proliferation, migration, and morphological modification of the trophectoderm cells. These complex events occur in a hypoxic intrauterine environment and are supported through the transport of secretions from maternal endometrial glands to the conceptus required for the biochemical processes of cell proliferation, migration, and differentiation. The conceptus utilizes glucose provided by the mother to initiate metabolic pathways that provide energy and substrates for other metabolic pathways. Fructose, however, is in much greater abundance than glucose in amniotic and allantoic fluids, and fetal blood during pregnancy. Despite this, the role(s) of fructose is largely unknown even though a switch to fructosedriven metabolism in subterranean rodents and some cancers are key to their adaptation to hypoxic environments.

Dietary supplementation with L-arginine between days 14 and 25 of gestation enhances NO and polyamine syntheses and the expression of angiogenic proteins in porcine placentae

Dietary supplementation with 0.4 or 0.8% L-arginine (Arg) to gilts between days 14 and 25 of gestation enhances embryonic survival and vascular development in placentae; however, the underlying mechanisms are largely unknown. This study tested the hypothesis that Arg supplementation stimulated placental expression of mRNAs and proteins that enhance angiogenesis, including endothelial nitric oxide synthase (eNOS), vascular endothelial growth factor (VEGF), placental growth factor (PGF), GTP cyclohydrolase-I (GTP-CH1), ornithine decarboxylase (ODC1), and vascular endothelial growth factor receptors 1 and 2 (VEGFR1 and VEGFR2). Beginning on the day of breeding, gilts were fed daily 2 kg of a corn-soybean meal-based diet supplemented with 0.0 (control), 0.4, or 0.8% Arg. On day 25 of gestation, gilts were hysterectomized to obtain uteri and conceptuses for histochemical and biochemical analyses. eNOS and VEGFR1 proteins were localized to endothelial cells of maternal uterine blood vessels and to the uterine luminal epithelium, respectively. Compared with the control, dietary supplementation with 0.4 or 0.8% Arg increased (P < 0.05) the amounts of nitrite plus nitrate (NOx; oxidation products of NO) and polyamines in allantoic and amniotic fluids, concentrations of NOx, tetrahydrobiopterin (BH4, an essential cofactor for all NOS isoforms) and polyamines in placentae, as well as placental protein abundances of GTP-CH1 (the key enzyme for BH4 production) and ODC1 (the key enzyme for polyamine synthesis). Placental  mRNA levels for GTP-CH1, eNOS, PGF, VEGF, and VEGFR2 increased in response to both 0.4% and 0.8% Arg supplementation. Collectively, these results indicate that dietary Arg supplementation to gilts between days 14 and 25 of pregnancy promotes placental angiogenesis by increasing the expression of mRNAs and proteins for angiogenic factors as well as NO and polyamine syntheses.

Maternal supply of cysteamine alleviates oxidative stress and enhances angiogenesis in porcine placenta

BACKGROUND

Oxidative stress in placenta is associated with the occurrence of adverse pregnancy outcomes in sow, but there are few satisfactory treatment strategies for these conditions. This study investigated the potential of cysteamine (CS) as an antioxidant protectant for regulating the reproductive performance, redox status, and placental angiogenesis of sows.

METHODS

The placental oxidative stress status and vascular density of piglets with different birth weights: < 1.0 kg (low birth weight, LBW) and 1.4-1.6 kg (normal birth weight, NBW) were evaluated, followed by allotting 84 sows to four treatments (n = 21) and feeding them with a basal diet supplemented with 0, 100, 300, or 500 mg/kg of CS from d 85 of gestation to d 21 of lactation, respectively. Placenta, serum, and colostrum samples of sows or piglets were collected, and the characteristics of sows and piglets were recorded. Furthermore, the in vivo results were validated using porcine vascular endothelial cells (PVECs).

RESULTS

Compared with the NBW placentae, the LBW placentae showed increased oxidative damage and were vulnerable to angiogenesis impairment. Particularly, H2O2-induced oxidative stress prompted intracellular reactive oxygen species generation and inhibited the tube formation and migration of PVECs as well as the expression of vascular endothelial growth factor-A (VEGF-A) in vitro. However, dietary CS supplementation can alleviate oxidative stress and improve the reproductive performance of sows. Specifically, compared with the control group, dietary 100 mg/kg CS could (1) decrease the stillbirth and invalid rates, and increase both the piglet birth weight in the low yield sows and the placental efficiency; (2) increase glutathione and reduce malondialdehyde in both the serum and the colostrum of sows; (3) increase the levels of total antioxidant capacity and glutathione in LBW placentae; (4) increase the vascular density, the mRNA level of VEGF-A, and the immune-staining intensity of platelet endothelial cell adhesion molecule-1 in the LBW placentae. Furthermore, the in vitro experiment indicated that CS pre-treatment could significantly reverse the NADPH oxidase 2-ROS-mediated inactivation of signal transducer and activator of transcription-3 (Stat3) signaling pathway induced by H2O2 inhibition of the proliferation, tube formation, and migration of PVECs. Meanwhile, inhibition of Stat3 significantly decreased the cell viability, tube formation and the VEGF-A protein level in CS pretreated with H2O2-cultured PVECs.

CONCLUSIONS

The results indicated that oxidative stress and impaired angiogenesis might contribute to the occurrence of LBW piglets during pregnancy, but CS supplementation at 100 mg/kg during late gestation and lactation of sows could alleviate oxidative stress and enhance angiogenesis in placenta, thereby increasing birth weight in low yield sows and reducing stillbirth rate. The in vitro data showed that the underlying mechanism for the positive effects of CS might be related to the activation of Stat3 in PVECs.

Altrenogest during early pregnancy modulates uterine glandular epithelium and endometrial growth factor expression at the time implantation in pigs

This study evaluated the effects of supplying altrenogest from day 6-12 of pregnancy on the endometrial glandular epithelium, corpora lutea (CL) morphology, and endometrial and CL gene expression. A total of 12 crossbred females (Landrace × Large White) were used. The females were assigned to 4 treatments according to a random design with a 2 × 2 factorial arrangement, with two categories (sow or gilt) and two treatments (non-treated and treated with altrenogest). On day 6 of pregnancy, animals were allocated to one of the following groups: non-treated (NT, n = 6; 3 sows and 3 gilts), and (T, n = 6; 3 sows and 3 gilts) treated daily with 20 mg of altrenogest, from day 6-12 of pregnancy. All animals were euthanized on day 13 of pregnancy. All CLs were individually weighed, and their volume were determined. The endometrial glandular density (GD), mean glandular area (MGA), and vascular density (VD) were determined by histomorphometric and immunohistochemical analyses. Endometrium samples were collected and analyzed by qRT-PCR to evaluate the abundance of transcripts for VEGF and IGF-I. Females in the T group had higher MGA (P < 0.05) compared to the NT group. There was no effect of treatment on GD or VD for both experimental groups. Sows in the T group had augmented expression of IGF-I (P < 0.05). Progestagen had no detrimental effect on CL morphology. In conclusion, altrenogest improves the uterine environment during the peri-implantation period in pigs without compromising corpora lutea development.

Insights Into Extracellular Vesicle/Exosome and miRNA Mediated Bi-Directional Communication During Porcine Pregnancy

Spontaneous fetal loss is one of the most important challenges that commercial pig industry is still facing in North America. Research over the decade provided significant insights into some of the associated mechanisms including uterine capacity, placental efficiency, deficits in vasculature, and immune-inflammatory alterations at the maternal-fetal interface. Pigs have unique epitheliochorial placentation where maternal and fetal layers lay in opposition without any invasion. This has provided researchers opportunities to accurately tease out some of the mechanisms associated with maternal-fetal interface adaptations to the constantly evolving needs of a developing conceptus. Another unique feature of porcine pregnancy is the conceptus derived recruitment of immune cells during the window of conceptus attachment. These immune cells in turn participate in pregnancy associated vascular changes and contribute toward tolerance to the semi-allogeneic fetus. However, the precise mechanism of how maternal-fetal cells communicate during the critical times in gestation is not fully understood. Recently, it has been established that bi-directional communication between fetal trophoblasts and maternal cells/tissues is mediated by extracellular vesicles (EVs) including exosomes. These EVs are detected in a variety of tissues and body fluids and their role has been described in modulating several physiological and pathological processes including vascularization, immune-modulation, and homeostasis. Recent literature also suggests that these EVs (exosomes) carry cargo (nucleic acids, protein, and lipids) as unique signatures associated with some of the pregnancy associated pathologies. In this review, we provide overview of important mechanisms in porcine pregnancy success and failure and summarize current knowledge about the unique cargo containing biomolecules in EVs. We also discuss how EVs (including exosomes) transfer their contents into other cells and regulate important biological pathways critical for pregnancy success.

Novel mineral regulatory pathways in ovine pregnancy: II. Calcium-binding proteins, calcium transporters, and vitamin D signaling

Mineralization of the fetal mammalian skeleton requires a hypercalcemic gradient across the placenta from mother to fetus. However, the mechanisms responsible for maintaining the placental transport of calcium remain poorly understood. This study aimed to identify calcium and vitamin D regulatory pathway components in ovine endometria and placentae across gestation. Suffolk ewes were bred with fertile rams upon detection of estrus (Day 0). On Days 9, 12, 17, 30, 70, 90, 110, and 125 of pregnancy (n=3-14/Day), ewes were euthanized and hysterectomized. Calcium abundance was influenced by gestational day in uterine flushings and allantoic fluid (P<0.05). The expression of S100G, S100A9, S100A12, ATP2B3, ATP2B4, TRPV5, TRPV6, CYP11A1, CYP2R1, CYP24, and VDR mRNAs known to be involved in calcium binding, calcium transport, and vitamin D metabolism were quantified by qPCR. Mediators of calcium and vitamin D signaling were expressed by Day 17 conceptus tissue, and endometria and placentae across gestation. Gestational day influenced the expression of S100G, S100A9, S100A12, TRPV6, VDR, and CYP24 mRNAs in endometria and placentae (P<0.05). Gestational day influenced endometrial expression of ATP2B3, and placental expression of TRPV5, ATP2B4, and CYP11A1 (P<0.05). VDR protein localized to the endoderm and trophectoderm (Day 17 conceptus) and was expressed in endometria and placentae throughout gestation. The observed spatiotemporal profile suggests a potential role of calcium and vitamin D in the establishment of pregnancy and regulation of fetal and placental growth, providing a platform for further mechanistic investigation.

Pre-implantation exogenous progesterone and pregnancy in sheep: I. polyamines, nutrient transport, and progestamedins

Background

Administration of exogenous progesterone (P4) to ewes during the pre-implantation period advances conceptus development and implantation. This study determined effects of exogenous P4 on transport of select nutrients and pathways that enhance conceptus development. Pregnant ewes (n = 38) were treated with either 25 mg P4 in 1 mL corn oil (P4, n = 18) or 1 mL corn oil alone (CO, n = 20) from day 1.5 through day 8 of pregnancy and hysterectomized on either day 9 or day 12 of pregnancy. Endometrial expression of genes encoding enzymes for synthesis of polyamines, transporters of glucose, arginine, and glycine, as well as progestamedins was determined by RT-qPCR.

Results

On day 12 of pregnancy, conceptuses from P4-treated ewes had elongated while those from CO-treated ewes were spherical. The mRNA expression of AZIN2, an arginine decarboxylase, was lower in endometria of P4-treated than CO-treated ewes on day 9 of pregnancy. Expression of FGF10, a progestamedin, was greater in endometria of CO and P4-treated ewes on day 12 of gestation in addition to P4-treated ewes necropsied on day 9 of gestation. Treatment with P4 down-regulated endometrial expression of amino acid transporter SLC1A4 on day 12 of pregnancy.

Conclusions

Results indicated that administration of exogenous P4 during the pre-implantation period advanced the expression of FGF10, which may accelerate proliferation of trophectoderm cells, but also was correlated with decreased expression of glycine and serine transporters and polyamine synthesis enzyme AZIN2. Further research with increased sample sizes may determine how differential expression affects endometrial functions and potentially embryonic loss.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40104-021-00554-6.

Novel mineral regulatory pathways in ovine pregnancy: I. phosphate, klotho signaling, and sodium-dependent phosphate transporters

Appropriate mineralization of the fetal skeleton requires an excess of phosphate in the fetus compared to the mother. However, mechanisms for placental phosphate transport are poorly understood. This study aimed to identify phosphate regulatory pathways in ovine endometria and placentae throughout gestation. Suffolk ewes were bred with fertile rams upon visual detection of estrus (Day 0). On Days 9, 12, 17, 30, 70, 90, 110, and 125 of pregnancy (n = 3-14/Day), ewes were euthanized and hysterectomized. Phosphate abundance varied across gestational days in uterine flushings, allantoic fluid, and homogenized endometria and placentae (P < 0.05). The expression of mRNAs for sodium-dependent phosphate transporters (SLC20A1 and SLC20A2) and klotho signaling mediators (FGF7, FGF21, FGF23, FGFR1-4, KL, KLB, ADAM10, and ADAM17) were quantified by qPCR. Day 17 conceptus tissue expressed SLC20A1, SLC20A2, KLB, FGF7, FGF21, FGF23, FGFR1, and FGFR2 mRNAs. Both sodium-dependent phosphate transporters and klotho signaling mediators were expressed in endometria and placentae throughout gestation. Gestational day influenced the expression of SLC20A1, ADAM10, ADAM17, FGF21, FGFR1, and FGFR3 mRNAs in both endometria and placentae (P < 0.05). Gestational day influenced endometrial expression of FGF7 (P < 0.001), and placental expression of FGF23 (P < 0.05). Immunohistochemistry confirmed that both FGF23 and KL proteins were expressed in endometria and placentae throughout gestation. The observed spatiotemporal profile of KL-FGF signaling suggests a potential role in the establishment of pregnancy and regulation of fetal growth. This study provides a platform for further mechanistic investigation into the role for KL-FGF signaling in the regulation of phosphate transport at the ovine maternal-conceptus interface.

Breed differences in placental development during late gestation between Chinese Meishan and White crossbred gilts in response to intrauterine crowding

The objective of this study was to evaluate placental development during late gestation (day 100) between Chinese Meishan (CM; n = 7) and White crossbred (WC; n = 5) gilts following intrauterine crowding induced by unilaterally hysterectomy-ovariectomy. Gross placental morphology and areolae density as well as histological morphology (i.e., folded bilayer and placental stroma) were analyzed using computer-assisted morphometry for placentas of the smallest and largest fetuses within each litter. There was a breed by fetal size interaction (P <  0.01) for areolae density in which placentas for large CM fetuses had greater areolae density compared to small CM fetuses, but the density of areolae was greater for CM fetuses compared to WC fetuses, irrespective of fetal size. The width of the folded bilayer was greater (P <  0.01) in placentas for WC gilts compared to CM gilts, irrespective of fetal size. Placentas for small fetuses had greater (P <  0.01) folded bilayer width compared to large fetuses, irrespective of breed. The placental stromal width was greater (P < 0.01) in placentas for large fetuses compared to small, irrespective of breed. The difference between stromal width in placentas between divergent-sized littermates, however, was greater (P =  0.05) in WC gilts compared to CM gilts, indicating there was a limited response to intrauterine crowding in CM gilts. These results indicate there is an altered placental development during late gestation in CM compared to WC gilts, thus, there are likely different mechanisms for responding to intrauterine crowding between breeds.

Amino Acids in the Nutrition and Production of Sheep and Goats

In sheep and goats, amino acid nutrition is essential for the maintenance of health and productivity. In this review, we analysed literature, mostly from the past two decades, focusing on assessment of amino acid requirements, especially on the balance of amino acid profiles between ruminal microbial protein and animal production protein (foetal growth, body weight gain, milk and wool). Our aim was to identify amino acids that might limit genetic potential for production. We propose that much attention should be paid to amino acid nutrition of individuals with greater abilities to produce meat, milk or wool, or to nourish large litters. Moreover, research is warranted to identify interactions among amino acids, particularly these amino acids that can send positive and negative signals at the same time.

Role of Dietary Amino Acids and Nutrient Sensing System in Pregnancy Associated Disorders

Defective implantation is related to pregnancy-associated disorders such as spontaneous miscarriage, intrauterine fetal growth restriction and others. Several factors proclaimed to be involved such as physiological, nutritional, environmental and managemental that leads to cause oxidative stress. Overloading of free radicals promotes oxidative stress, and the internal body system could not combat its ability to encounter the damaging effects and subsequently leading to pregnancy-related disorders. During pregnancy, essential amino acids display important role for optimum fetal growth and other necessary functions for continuing fruitful pregnancy. In this context, dietary amino acids have received much attention regarding the nutritional concerns during pregnancy. Arginine, glutamine, tryptophan and taurine play a crucial role in fetal growth, development and survival while ornithine and proline are important players for the regulation of gene expression, protein synthesis and angiogenesis. Moreover, amino acids also stimulate the mammalian target of rapamycin (mTOR) signaling pathway which plays a central role in the synthesis of proteins in placenta, uterus and fetus. This review article explores the significances of dietary amino acids in pregnancy development, regulation of nutrient-sensing pathways such as mTOR, peroxisome proliferator-activated receptors (PPARs), insulin/insulin-like growth factor signaling pathway (IIS) and 5' adenosine monophosphate-activated protein kinase (AMPK) which exhibit important role in reproduction and its related problems. In addition, the antioxidant function of dietary amino acids against oxidative stress triggering pregnancy disorders and their possible outcomes will also be enlightened. Dietary supplementation of amino acids during pregnancy could help mitigate reproductive disorders and thereby improving fertility in animals as well as humans.

Rise of the rabbit model for implantation research. A commemoration of the scientific work of Bent G. Boving (1920-2019)

Bent G. Boving, a remarkable pioneer of research on mechanistic aspects of embryo implantation and specifically of using the rabbit model for this purpose, passed away peacefully on 15 November 2019, not long before he would have been able to celebrate his 100th birthday on 23 February 2020. His work has been very stimulating for other researchers, in part possibly because it elicited controversial discussions. This article attempts to give an overview of his scientific contributions, which still harbor some treasures, including potentially stimulating ideas for future research on implantation.

Peroxisome proliferator-activated receptor β/δ and γ agonists differentially affect prostaglandin E2 and cytokine synthesis and nutrient transporter expression in porcine trophoblast cells during implantation

Peroxisome proliferator-activated receptors (PPARs) belong to the nuclear receptor family of ligand-dependent transcription factors. PPARs have been shown to be important regulators of female reproductive functions, including conceptus development and placenta formation. This study examines the effect of PPARβ/δ and PPARγ agonists and antagonists on (1) the synthesis of prostaglandin (PG) E2, interleukin (IL) 6, interferon (IFN) γ, and tumor necrosis factor (TNF) α and (2) the mRNA expression of genes encoding nutrient transporters and/or binding proteins in Day 15 conceptus trophoblast cells. The study also examines whether PPAR agonist-modulated IL6, IFNγ, and TNFα secretion is mediated via mitogen-activated protein kinase (MAPK) pathways. Trophoblast cells were exposed to L-165,041 (a PPARβ/δ agonist) or rosiglitazone (a PPARγ agonist) in the presence or absence of GSK3787 (a PPARβ/δ antagonist) or GW9662 (a PPARγ antagonist) or in the presence or absence of U0126 (a MAPK inhibitor). Rosiglitazone stimulated PGE synthase and IFNG mRNA expression in trophoblast cells and enhanced PGE2 concentrations in the incubation medium. Moreover, cells treated with rosiglitazone exhibited increased abundance of the solute carrier organic anion transporter family member 2A1 (SLCO2A1, a PG transporter) and of fatty acid binding protein (FABP) 5 transcripts. All these effects were abolished by the addition of GW9662, which indicates that the action of rosiglitazone is PPARγ-dependent in the studied cells. L-165,041 inhibited TNFα synthesis and decreased the mRNA expression of FABP3 and IL6 in trophoblast cells. However, this effect was not abolished by the addition of GSK3787 into the incubation medium, suggesting that L-165,041 action is independent of PPARβ/δ. The inhibitory effect of L-165,041 on TNFα concentration and the stimulatory effect of rosiglitazone on IFNγ accumulation in the medium were not observed in the presence of the MAPK inhibitor, suggesting that the action of both agonists may be mediated by MAPKs. In conclusion, PPARβ/δ and PPARγ agonists are differentially involved in the trophoblast expression of genes related to conceptus development and implantation in pigs. Furthermore, L-165,041 and rosiglitazone may have PPAR-dependent and -independent effects in conceptus trophoblast cells.

Supplemental progesterone during early pregnancy exerts divergent responses on embryonic characteristics in sows and gilts

Progesterone (P4) plays a key role in pregnancy establishment and maintenance; during early pregnancy, P4 stimulates the production and release of uterine secretions necessary for conceptus growth prior to implantation; therefore, exogenous P4 supplementation may improve embryo development. This study evaluated the effects of supplementation during early pregnancy with long-acting injectable progesterone or altrenogest on embryonic characteristics of sows and gilts. Thus, a total of 32 sows and 16 gilts were used. On day 6 of pregnancy sows and gilts were allocated to one of the following groups: non-supplemented; supplemented with 20 mg of altrenogest, orally, from days 6 to 12 of pregnancy; supplemented with 2.15 mg/kg of long-acting injectable progesterone on day 6 of pregnancy. Animals were killed on day 28 of pregnancy, and ovulation rate, embryo survival, embryo weight, crown-to-rump length, uterine glandular epithelium and endometrial vascularization were assessed. Treatments had no effect on pregnancy rate, embryo survival or endometrial vascular density (P > 0.05). Non-supplemented gilts presented larger and heavier embryos compared to gilts from supplemented groups (P < 0.05). Sows in the altrenogest group presented larger and heavier embryos compared to non-supplemented sows and sows supplemented with long-acting injectable progesterone. In conclusion, supplementation of sows and gilts with progestagen from day 6 of pregnancy can be used as a means to improve embryo survival without deleterious effects.

Protein expression profiles in Meishan and Duroc sows during mid-gestation reveal differences affecting uterine capacity, endometrial receptivity, and the maternal-fetal Interface

BACKGROUND

Embryonic mortality is a major concern in the commercial swine industry and primarily occurs early in gestation, but also during mid-gestation (~ days 50-70). Previous reports demonstrated that the embryonic loss rate was significant lower in Meishan than in commercial breeds (including Duroc). Most studies have focused on embryonic mortality in early gestation, but little is known about embryonic loss during mid-gestation.

RESULTS

In this study, protein expression patterns in endometrial tissue from Meishan and Duroc sows were examined during mid-gestation. A total of 2170 proteins were identified in both breeds. After statistical analysis, 70 and 114 differentially expressed proteins (DEPs) were identified in Meishan and Duroc sows, respectively. Between Meishan and Duroc sows, 114 DEPs were detected at day 49, and 98 DEPs were detected at day 72. Functional enrichment analysis revealed differences in protein expression patterns in the two breeds. Around half of DEPs were more highly expressed in Duroc at day 49 (DUD49), relative to DUD72 and Meishan at day 49 (MSD49). Many DEPs appear to be involved in metabolic process such as arginine metabolism. Our results suggest that the differences in expression affect uterine capacity, endometrial matrix remodeling, and maternal-embryo cross-talk, and may be major factors influencing the differences in embryonic loss between Meishan and Duroc sows during mid-gestation.

CONCLUSIONS

Our data showed differential protein expression pattern in endometrium between Meishan and Duroc sows and provides insight into the development process of endometrium. These findings could help us further uncover the molecular mechanism involved in prolificacy.

Mechanotransduction drives morphogenesis to develop folding during placental development in pigs

INTRODUCTION

Our aim was to evaluate whether mechanical forces applied to the placenta of pigs correlate with morphological changes that coordinate the development of placental folds.

METHODS

We examined changes in the length of placental folds, expression of mechanotransduction-implicated molecules in placental tissues, changes in the size of subepithelial blood vessels within the endometrium, and effects of in vivo supplementation with arginine on fold development.

RESULTS

We observed that: 1) the length of folds increased 2) osteopontin, talin and focal adhesion kinase co-localized into aggregates at the maternal placental (uterine)-fetal placental interface; 3) filamin, actin related protein 2, and F-actin were enriched in the tops of maternal placental folds extending into fetal placental tissue; 4) maternal stromal fibroblasts acquired alpha smooth muscle actin; 5) endometrial blood vessels increased in size; and 6) supplementation with arginine increased fold length.

CONCLUSION

Results indicate that lengthening of folds associates with polymerization of actin that coincides with FA assembly, endometrial fibroblasts differentiate into myofibroblasts, and dilation of subepithelial blood vessels correlates with development of folds that is enhanced by arginine. We propose that dilation of subepithelial endometrial blood vessels delivers increased blood flow that pushes upward on the interface between the uterine luminal epithelium (LE) and the placental chorionic epithelium (CE), protrusive forces from growing uterine blood vessels trigger focal adhesion assembly and actin polymerization between the LE and CE, and endometrial fibroblasts differentiate into contractile myofibroblasts that pull connective tissue downward and inward to sculpt folds at the maternal placental-fetal placental interface.