Prostaglandins and reproduction in female farm animals

Lysophosphatidic acid enhances PGE2 to PGF2α ratio and nitric oxide level in nonpregnant buffalo uterus

Lysophosphatidic acid (LPA) is a small ubiquitous lipid exerting diverse biological functions. Its role in reproduction in different species has created great interest in recent times. In the present study, we aimed to elucidate LPA signaling in nonpregnant buffalo uterus by in vitro studies. Standard techniques like real-time PCR (for mRNA expression of LPARs and COX-2 and iNOS), Western blot (for PPARγ protein expression), sandwich ELISA (for PGE2 and PGF2α assay) and histopathology (for assessment of endometrial architecture in culture) were used in this study. The buffalo uterine tissues were collected from the local slaughterhouse and were selected for the study on the basis of the presence of corpus luteum on the ovary (n = 5). The LPAR3 receptor was the highest expressed receptor as compared to LPAR1 and LPAR6 in non-pregnant uterine tissues after 6 h incubation in Dulbecco's Modified Eagle Medium (DMEM). 50 μM LPA increased the mRNA expressions of COX-2 and iNOS enzymes which were attenuated by the treatment of LPAR1/3 antagonist Ki16425. PPARγ antagonist GW9662 prevented the LPA-induced increase in iNOS mRNA expression but did not alter the COX-2 expression. LPA also enhanced the PGE₂ to PGF_2α ratio in uterine tissue homogenates which was inhibited by all the receptor antagonists as well as by the inhibitors of COX-2 and iNOS. LPA also increased the total nitrite level in tissue homogenates in LPAR1/3- and iNOS-dependent manner. Additionally, we demonstrate PPARγ mRNA and protein expressions in nonpregnant buffalo endometrium. In conclusion, the results of the present study suggest that LPA acts as a luteotropic factor during the estrus cycle in nonpregnant buffalo uterus by enhancing PGE2 to PGF2α ratio and NO level through multiple receptors.

Reproduction in domestic ruminants during the past 50 yr: discovery to application

The study of reproductive physiology in domestic ruminants has progressed from the whole animal to the molecular level in an amazingly short period of time. The volume of information on this subject is enormous; therefore, we have focused on domestic ruminants, with an emphasis on cattle. To date, artificial insemination (AI) is perhaps the most powerful technique that reproductive physiologists and geneticists have provided the livestock industry for genetic improvement. Early efforts to establish AI as a tool were initiated in Russia around 1899 and since that time major advances in methods of semen collection, evaluation of male fertility, cryopreservation of sperm, sex-sorted semen, and estrous cycle control have occurred. The preceding advances not only led to the widespread use of AI, but also contributed to our fundamental understanding of ovulation control, timing of insemination, gamete biology, and cryopreservation. In regards to anestrus, our understanding of the concept of neuroendocrine control of the pituitary gland and the role of steroid feedback led to the Gonadostat Theory, which proposes that onset of puberty is due to a decrease in the negative feedback of gonadal steroids over time. Subsequent studies in prepuberal and postpartum sheep and cattle established that a short luteal phase frequently precedes the first normal length cycle that is accompanied by estrous expression. This observation led to the common practice of treating prepuberal heifers and anestrous postpartum cows with a short-term progestin treatment (e.g., Controlled Internal Drug Release) to induce normal estrous cycles. In domestic ruminants, fertilization rate is high (85% to 95%); however, significant embryonic mortality before or around the time of maternal recognition of pregnancy (MRP) reduces the pregnancy rate to a single breeding. Significant effort has been directed at determining the time of MRP, the signal for MRP, as well as elucidating the physiological, cellular, and molecular dialogue between the conceptus and uterine environment. Advancements have now led us to the ability to edit the genome to alleviate disease and possibly improve production traits. In summary, major advancements in our understanding of reproductive biology have stemmed from efforts to establish the AI and embryo transfer technique and reduce the negative impact of anestrus and embryonic mortality in domestic ruminants.

Synthesis of Alfaprostol and PGF2α through 1,4-Addition of an Alkyne to an Enal Intermediate as the Key Step

The veterinary drug Alfaprostol and prostaglandin PGF_2α have been synthesized in just nine steps. The strategy involved the conjugate addition of an alkyne to a bicyclic enal, available in three steps by a proline-catalyzed aldol reaction of succinaldehyde. In the case of Alfaprostol, this resulted in the shortest synthesis reported to date. For PGF_2α, this approach improved our previous route by making the 1,4-addition and ozonolysis more operationally simple.

The influence of arachidonic acid metabolites on PPAR and RXR expression in bovine uterine cells

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors belonging to the superfamily of nuclear receptors. Three isoforms have been described: alpha (PPARα), delta (PPARδ), and gamma (PPARγ). PPARs heterodimerize with retinoid X receptors (RXRs: RXRα, RXRβ and RXRγ). PPAR activity can be modulated by several ligands, including arachidonic acid (AA) metabolites. The aims of the study were to determine the effect of AA metabolites (prostaglandin [PG]E₂, PGF_2α, leukotriene [LT]B₄, and LTC₄) on mRNA (real-time PCR) and protein expression (Western blotting) of PPARα, PPARδ, and PPARγ, and on mRNA expression of RXRα, RXRβ, and RXRγ, in bovine epithelial, stromal, and myometrial primary uterine cells and in bovine stromal cells with silenced PPAR genes (N = 10). All PPAR and RXR isoforms were expressed. Prostaglandins affected expression of PPARs only in stromal cells, whereas LTs modulated PPARγ mRNA expression in epithelial and myometrial primary cells. Blockade of signal transduction through PPARs prevented interactions between AA metabolites and PPARs and changed RXR expression comparing with primary stromal cells. In primary stromal uterine cells, mRNA expression of RXRs was higher than that of PPARs. In uterine stromal cells in which intracellular signaling through PPARs was blocked, RXRs seem to take over the role of PPARs and are pivotal for cell functions. This study revealed the reaction of PPARs and RXRs to agonists which naturally occur in the bovine uterus.

Prostaglandins in teleost ovulation: A review of the roles with a view to comparison with prostaglandins in mammalian ovulation

Prostaglandins are well known to be central regulators of vertebrate ovulation. Studies addressing the role of prostaglandins in mammalian ovulation have established that they are involved in the processes of oocyte maturation and cumulus oocyte complex expansion. In contrast, despite the first indication of the role of prostaglandins in teleost ovulation appearing 40 years ago, the mechanistic background of their role has long been unknown. However, studies conducted on medaka over the past decade have provided valuable information. Emerging evidence indicates an indispensable role of prostaglandin E₂ and its receptor subtype Ptger4b in the process of follicle rupture. In this review, we summarize studies addressing the role of prostaglandins in teleost ovulation and describe recent advances. To help understand differences from and similarities to ovulation in mammalian species, the findings on the roles of prostaglandins in mammalian ovulation are discussed in parallel.

Additional small dose of prostaglandin F2α at timed artificial insemination failed to improve pregnancy risk of lactating dairy cows

Two experiments were performed to test the hypothesis that administering PGF_2α concurrent with timed artificial insemination (AI) in lactating dairy cows would enhance pregnancy per AI (P/AI). In experiment 1, lactating Holstein cows (n = 289) in one herd were enrolled after a non-pregnancy diagnosis (30-36 d after AI) to synchronize subsequent ovulation before AI. Cows were assigned randomly to receive (im) 10 mg of PGF_2α concurrent with timed AI (Day 0; treatment) or no injection (control). Blood samples were collected on Days -3, 0, and 13 to determine serum concentrations of progesterone. Ovaries were scanned via transrectal ultrasonography to determine follicle diameters (Day -3), subsequent ovulation risk (Day 13), and total volume of luteal tissue (Day 13). Diagnosis of pregnancy occurred on Days 32 and 80 after AI. Ovulation risk post-AI exceeded 90% and did not differ between treatments. In addition, PGF_2α treatment only numerically increased progesterone (5.7 ± 0.3 vs. 6.2 ± 0.3 ng/mL) or luteal tissue volume (8.9 ± 0.4 vs. 9.8 ± 0.5 ng/mL) on Day 13 by 8.8% (P = .206) or 10.1% (P = .134) in control and treated cows, respectively. Pregnancy per AI at Days 32 (P = .50) and 80 (P = .33) did not differ between treatments. Cows with progesterone >0.5 ng/mL at timed AI had reduced (P < .001) ovulation risk but risk was unaffected by treatment. In experiment 2, lactating dairy cows (n = 1828) in two commercial dairy herds were enrolled at time of insemination (Day 0), and assigned randomly to treatment or control as described in experiment 1. Initial (Days 32-35) and confirmed (Days 63-68) pregnancy diagnosis revealed no differences in P/AI or pregnancy loss. Pregnancy diagnosis on Days 32-35 produced percentage increases in P/AI for primiparous compared with multiparous cows (20.8%; P = .002), for first-service compared with repeat-service cows (26%; P = .001), and cows in one herd compared with the second herd (36%; P < .001). Pregnancy loss was greater (P = .001) for cows inseminated at first (10.0%) vs. later services (5.3%) but was unaffected by treatment. Cows treated with PGF_2α in one herd produced more twins than control cows (11.7 vs. 3.2%), whereas no treatment difference was detected in the second herd (5.6 vs. 5.6%), respectively. We conclude that im treatment of lactating dairy cows with 10 mg of PGF_2α concurrent with timed AI did not improve P/AI or embryo survival, but increased twinning in one herd.

Expression of progesterone receptor protein in the ovine uterus during the estrous cycle: Effects of nutrition, arginine and FSH

To evaluate expression of progesterone receptor (PGR) AB in follicle stimulating hormone (FSH)-treated or non-treated sheep administered with arginine (Arg) or saline (Sal) fed a control (C), excess (O) or restricted (U) diet, uterine tissues were collected at the early, mid and/or late luteal phases. In exp. 1, ewes from each diet were randomly assigned to one of two treatments, Arg or Sal administration three times daily from day 0 of the first estrous cycle until uterine tissue collection. In exp. 2, ewes were injected twice daily with FSH on days 13-15 of the first estrous cycle. Uterine tissues were immunostained to detect PGR followed by image analysis. PGR were detected in luminal epithelium (LE), endometrial glands (EG), endometrial stroma (ES), myometrium (Myo), and endometrial and myometrial blood vessels. The percentage of PR-positive cells and/or intensity of staining were affected by phase of the estrous cycle, plane of nutrition, and/or FSH but not by Arg. In exp. 1, percentage of PGR-positive cells in LE and EG but not in ES and Myo was greater at the early and mid than late luteal phase, was not affected by plane of nutrition, and was similar in LE and EG. Intensity of staining was affected by phase of the estrous cycle and plane of nutrition in LE, EG and Myo, and was the greatest in LE, less in EG, and least in ES and Myo. In exp. 2, percentage of PGR-positive cells in LE, EG, ES and Myo was affected by phase of the estrous cycle, but not by plane of nutrition; was greater at the early than mid luteal phase; and was greatest in LE and EG, less in luminal (superficial) ES and Myo and least in deep ES. Intensity of staining was affected by phase of the estrous cycle and plane of nutrition in all compartments but ES, and was the greatest in LE and luminal EG, less in deep EG, and least in ES and Myo. Comparison of data for FSH (superovulated) and Sal-treated (non-superovulated) ewes demonstrated that FSH affected PR expression in all evaluated uterine compartments depending on plane of nutrition and phase of the estrous cycle. Thus, PGR are differentially distributed in uterine compartments, and PGR expression is affected by nutritional plane and FSH, but not Arg depending on phase of the estrous cycle. Such changes in dynamics of PGR expression indicate that diet plays a regulatory role and that FSH-treatment may alter uterine functions.

Corpus luteum Regression Induced by Prostaglandin F2α in Microminipigs During the Normal Estrous Cycle

Induction of corpus luteum regression and subsequent estrus using prostaglandin F2α (PGF2α) in microminipigs was investigated. Microminipigs with normal estrous cycle were treated with PGF2α as 0.75 mg (0.75 PG group, n=3) or 1.5 mg (1.5 PG group, n=4) dinoprost injected into the vulva at 24-h intervals at 10 days after the onset of estrus (D0), D1 and D2. Three microminipigs were not treated (control group). The estrous interval in the 1.5 PG group was significantly shortened compared to the control and 0.75 PG groups. Plasma progesterone levels started to decline and reached the base line in the 1.5 PG group significantly faster than in the control group. In conclusion, we demonstrate that multiple PGF2α treatments can induce corpus luteum regression and estrous synchronization in female microminipigs.

Effects of preimplantation factor on interleukin-6 and prostaglandin F2α and E2 in the bovine endometrium

Preimplantation factor (PIF) is a pregnancy specific peptide with immune modulatory properties exerted on the human endometrium. Viable bovine embryos secrete PIF, but its effect on the bovine endometrial immune response is unknown, both in native and inflammatory stimulated endometrial tissue. An ex vivo bovine endometrial tissue culture model was used with lipopolysaccharide (LPS) as an inflammatory stimulant. The effect of synthetic PIF (sPIF) was assessed, in three separate experiments, on the secretion or mRNA expression of essential prostaglandins and cytokines. Radioimmunoassays were used to assess prostaglandin secretion and ELISA for IL-6 secretion from endometrial explants. mRNA expression of IL6 and IL8 was analysed from endometrial explants with real-time PCR. Synthetic PIF reduced native IL-6 secretion from explants when pre-treated for 24 h. There was no effect of sPIF on IL-6 secretion from LPS challenged explants; however, sPIF increased IL6 mRNA expression when challenged with 500 ng/mL LPS. There was no effect of sPIF on prostaglandin secretion or mRNA expression of IL8. Therefore, sPIF is able to modulate the native IL-6 production pathway in the bovine endometrium, yet demonstrates no effect on prostaglandin secretion or IL8 expression. Unlike in human studies, effects of sPIF were minimal, thus sPIF is not an effective modulator of the immune targets investigated in the bovine endometrium.

Functional characterization of the promoter of carbonyl reductase 1 gene in porcine endometrial cells

Prostaglandins (PGs) play a critical role in porcine reproduction, of which prostaglandin E2 (PGE2) and prostaglandin F2α (PGF2α) exert antiluteolytic and luteolysis actions, respectively. As a rate-limiting enzyme, carbonyl reductase 1 (CBR1) catalyzes the conversion of PGE2 to PGF2α. A high ratio of PGE2:PGF2α is beneficial to the establishment and maintenance of porcine pregnancy. PG is essential for the establishment of pregnancy which resembles the proinflammatory response and nuclear factor κB (NF-κB) is involved in the process. Bioinformatic analysis has shown that NF-κB is a possible factor bound to two cis-regulatory elements in CBR1 promoter. In this study, we cloned the 2997 bp (-2875/+122) of the promoter, and constructed six 5'-deleted dual-luciferase reporter recombinant vectors. In endometrial cells, the region of P2 (-1640/+7) exhibited the greatest transcriptional activity at driving luciferase expression, but not significantly different from that of P1 (-2089/+7). The activity of P1, P2, and P3 (-1019/+7) was highly significantly higher than that of others (P<0.01), suggesting that two positive regulatory elements were likely present in the regions of -1640/-1019 and -1019/-647. The results also showed that the -1640/-647 region was indispensable for the promoter. The results of chromatin immunoprecipitation (ChIP) demonstrated that the NF-κB subunit p65 binds to one site around -1545/-1531. Using four reference genes, we found that the over-expression of p65 enhanced the expression of CBR1 (P<0.05) in porcine endometrial epithelial cells, while knockdown of the p65 did not down-regulate the CBR1 expression. These results indicated that NF-κB (p65) could bind to the special element of CBR1 gene promoter in porcine endometrial epithelial cells in vitro. The binding site of NF-κB was a positive regulator for the CBR1 gene promoter, but was not necessary for the basic expression.

Colostrum yield and litter performance in multiparous sows subjected to farrowing induction

The consumption of colostrum at a low level can compromise the survival and growth of piglets. Therefore, this study aimed to evaluate the effect of farrowing induction on colostrum yield, IgG concentration and the survival and performance of piglets until the weaning. Sows of parity 3 to 7 were assigned into two groups: Control (n = 48), sows with spontaneous farrowing; and induction (n = 48), sows induced to farrow on day 114 of gestation with a PGF₂ analogue. Colostrum and blood samples were collected from the sows, at farrowing and 24 hr later. Blood samples from the piglets were collected at 24 hr after birth. The performance of the piglets was evaluated in a subsample of 28 litters from each group. All piglets were weighed at 7, 14 and 20 days of age. The farrowing length, the number of piglets born alive, stillborn piglets, weight at birth, litter weight at birth and colostrum yield were not significantly affected (p > .05) by farrowing induction. There was no difference between the groups (p > .05) in the percentage of sows with obstetric interventions. Serum IgG concentration, in both sows and piglets, and colostrum IgG concentration were similar between the groups (p > .05). Furthermore, survival rate, piglet weight and litter weight at 7, 14 and 20 days of age were also similar between the groups (p > .05). Therefore, it can be concluded that the farrowing induction performed on day 114 of gestation does not affect the colostrum yield, the IgG concentration in colostrum and serum of piglets, and the litter performance until the weaning.

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

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

Peri-ovulatory endocrine regulation of the prostanoid pathways in the bovine uterus at early dioestrus

We hypothesised that different endocrine profiles associated with pre-ovulatory follicle (POF) size would impact on uterine prostanoid pathways and thereby modulate the histotroph composition. Beef cows (n = 15 per group) were hormonally manipulated to have small (SF-SCL group) or large (LF-LCL group) pre-ovulatory follicles (POF) and corpora lutea (CL). Seven days after induction of ovulation, animals were slaughtered and uterine tissues and flushings were collected for quantification of prostanoids. The POF and CL size and the circulating progesterone concentrations at Day 7 were greater (P < 0.05) in the LF-LCL cows than in the SF-SCL group, as expected. The abundance of 5 out of 19 genes involved in prostanoid regulation was different between groups. Transcript abundance of prostaglandin F2α, E2 and I2 synthases was upregulated (P < 0.05) and phospholipase A2 was downregulated (P < 0.05) in endometrium of the LF-LCL group. No difference (P > 0.1) in prostanoid concentrations in the endometrium or in uterine flushings was detected between groups. However, prostaglandin F2α and E2 concentrations in the uterine flushings were positively correlated with the abundance of transcripts for prostaglandin endoperoxide synthase 2 (0.779 and 0.865, respectively; P < 0.002). We conclude that endometrial gene expression related to prostanoid synthesis is modulated by the peri-ovulatory endocrine profile associated with POF size, but at early dioestrus differences in transcript abundance were not reflected in changes in prostanoid concentrations in the uterine tissue and fluid.

Prostaglandin synthesis by the porcine corpus luteum: effect of tumor necrosis factor-α

The porcine corpus luteum (CL) displays delayed sensitivity to PGF-2α (luteolytic sensitivity, [LS]) until days 12 to 13 of cycle. The control of LS is unknown, but it is temporally associated with macrophage (which secrete tumor necrosis factor-α; TNF-α) infiltration into the CL. Other studies showed that TNF-α induces LS in vitro and that prostaglandins (PGs) may be involved in this mechanism. In experiment 1, PGF-2α and PGE secretion by luteal cells (LCs) was measured on days 4 to 14 of the estrous cycle, and the expression of PTGFS/AKR1B1 and PTGES/mPGES-1, determined by Western blot, before (day 7) vs after (day 13) the onset of LS. Results showed that the PGF-2α:PGE ratio increased significantly (P < 0.05) from day 4 to 13-14, and PTGFS/AKR1B1 and PTGES/mPGES-1 were significantly increased (P < 0.05) on day 13 (vs day 7). In experiment 2, LCs were collected from porcine CL at early (∼days 4-6) or mid (∼days 7-12) stages of the estrous cycle and cultured with 0, 0.1, 1, or 10 ng/mL TNF-α. Results showed that TNF-α significantly increased (P < 0.05) messenger RNA (mRNA) expression of cyclooxygenase (COX)-2 and mPGES-1 but not AKR1B1. TNF-α had no significant effects on AKR1B1 or mPGES protein abundance. TNF-α significantly increased (P < 0.05) PGE-2 but had no effect on PGF-2α secretion or on the PGF-2α:PGE2 ratio. In conclusion, although TNF-α increased COX2 and mPGES-1 mRNA, and PGE-2 secretion in vitro, it did not increase the PGF-2α:PGE2 ratio. Studies are currently directed toward exploring other pathways (eg, FP receptor signaling) by which TNF-α induces LS in the porcine CL.

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

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

A syntenic locus on buffalo chromosome 20: novel genomic hotspot for miRNAs involved in follicular-luteal transition

The developmental reorganization of ovarian follicular granulosa cells (GC) during follicular maturation, ovulation, and luteinization require a well-controlled regulation of dynamic gene expression profiles. Recently, microRNAs (miRNAs) were found to be key players of ovarian follicular dynamics. The current study aimed to understand the miRNA regulatory role in follicular-luteal transition by characterizing the miRNA profile through miRNA-seq at different follicular (small, medium, and large) and luteal (early, mid, and late) stages in Indian water buffaloes, mono-ovulatory animals like humans. A total of 517 miRNAs were identified in follicular granulosa cells (GC) and corpus luteum (CL) together. Among them, 2 unique and 40 novel miRNAs were in GC; 15 unique and 45 novel miRNAs were in CL. Among the remaining 415 annotated common miRNAs between GC and CL, 43 have showed significant (p < 0.05) differential expression between GC and CL. Particularly, 39 and 4 miRNAs showed higher expression in CL and GC, respectively, with respect to each other. Genome mapping analysis revealed that 71.7% of differential miRNAs having higher expression in CL compared to GC, and 93% of the unique miRNAs in CL were mapped to a short chromosomal region of 0.7 Mb (67.4 to 68.1 Mb) on chromosome 21 of cows which is syntenic to the buffalo chromosome 20. Clustering of all these miRNAs at this locus suggests it as a chromosomal hotspot for miRNAs involved in follicular-luteal transition, especially for CL physiological functions.

Alterations in eicosanoid composition during embryonic development in the chorioallantoic membrane of the American alligator (Alligator mississippiensis) and domestic chicken (Gallus gallus)

Eicosanoids are signaling lipids known to regulate several physiological processes in the mammalian placenta, including the initiation of parturition. Though all amniotes construct similar extraembryonic membranes during development, the composition and function of eicosanoids in extraembryonic membranes of oviparous reptiles is largely unknown. The majority of effort placed in eicosanoid investigations is typically targeted toward defining the role of specific compounds in disease etiology; however, comprehensive characterization of several pathways in eicosanoid synthesis during development is also needed to better understand the complex role of these lipids in comparative species. To this end, we have examined the chorioallantoic membrane (CAM) of the American alligator (Alligator mississippiensis) and domestic chicken (Gallus gallus) during development. Previously, our lab has demonstrated that the CAM of several oviparous species shared conserved steroidogenic activity, a feature originally attributed to mammalian amniotes. To further explore this, we have developed a liquid chromatography/tandem mass spectrometry method that is used here to quantify multiple eicosanoids in the CAM of two oviparous species at different stages of development. We identified 18 eicosanoids in the alligator CAM; the cyclooxygenase (COX) pathway showed the largest increase from early development to later development in the alligator CAM. Similarly, the chicken CAM had an increase in COX products and COX activity, which supports the LC-MS/MS analyses. Jointly, our findings indicate that the CAM tissue of an oviparous species is capable of eicosanoid synthesis, which expands our knowledge of placental evolution and introduces the possibility of future comparative models of placental function.

Optimizing dietary lipid use to improve essential fatty acid status and reproductive performance of the modern lactating sow: a review

Dietary lipid supplementation benefits the prolific and high-producing modern lactating sow. A comprehensive review of recent studies showed that lipid supplementation increases average daily energy intake, which is partitioned for lactation as indicated by greater milk fat output and improved litter growth rate. Recent compelling findings showed that addition of particular lipids during lactation improved the subsequent reproductive outcome of sows. Such benefits were related to the level of dietary essential fatty acids (EFA, linoleic acid, C18:2n-6; and α-linolenic acid, C18:3n-3) during lactation. Lactation diets without supplemental EFA resulted in a pronounced negative balance (intake minus milk output) of linoleic (−25.49 g/d) and α-linolenic acid (−2.75 g/d); which compromised sow fertility (farrowing rate < 75 % and culling rates > 25 % of weaned sows). This phenomenon seems to be increasingly important with advancing sow age because of a progressive reduction of body EFA pool over successive lactations. The net effect of supplemental EFA during lactation was to create a positive EFA balance, which improved the subsequent reproduction of sows. Adequate linoleic acid intake improved the proportion of sows that farrowed in the subsequent cycle (Farrowing rate (%) = [(−1.5 × 10⁻³ × linoleic acid intake (g/d)²) + (0.53 × linoleic acid intake (g/d)) + (45.2)]; quadratic P = 0.002, R² = 0.997, RMSE = 0.031). In addition, increasing linoleic acid intake increased the number of pigs born in the subsequent cycle (total pigs born (n) = [(9.4 × 10⁻⁵ × linoleic acid intake (g/d)²) + (0.04 × linoleic acid intake (g/d)) + (10.94)]; quadratic P = 0.002, R² = 0.997, RMSE = 0.031). Supplemental α-linolenic acid resulted in a rapid return to estrus (sows bred: sows weaned = 94.2 %; wean-to-estrus interval = 4.0 d) and achieved a high retention of pregnancy (sows pregnant: sows bred = 98 %). Collectively, we conclude that a minimum dietary intake of 10 g/d of α-linolenic acid, simultaneous with a minimum of 125 g/d of linoleic acid should be provided to ≥ 95 % of the sows; thereby, achieving a maximum sow reproductive efficiency through multiple mechanisms that include rapid return to estrus, high maintenance of pregnancy and large subsequent litter size in mature sows, that appear to be susceptible to EFA deficiency.

Novel concepts on the role of prostaglandins on luteal maintenance and maternal recognition and establishment of pregnancy in ruminants

In ruminants, the corpus luteum (CL) of early pregnancy is resistant to luteolysis. Prostaglandin (PG)E2 is considered a luteoprotective mediator. Early studies indicate that during maternal recognition of pregnancy (MRP) in ruminants, a factor(s) from the conceptus or gravid uterus reaches the ovary locally through the utero-ovarian plexus (UOP) and protects the CL from luteolysis. The local nature of the embryonic antiluteolytic or luteoprotective effect precludes any direct effect of a protein transported or acting between the gravid uterus and CL in ruminants. During MRP, interferon tau (IFNT) secreted by the trophoblast of the conceptus inhibits endometrial pulsatile release of PGF2α and increases endometrial PGE2. Our recent studies indicate that (1) luteal PG biosynthesis is selectively directed toward PGF2α at the time of luteolysis and toward PGE2 at the time of establishment of pregnancy (ESP); (2) the ability of the CL of early pregnancy to resist luteolysis is likely due to increased intraluteal biosynthesis and signaling of PGE2; and (3) endometrial PGE2 is transported from the uterus to the CL through the UOP vascular route during ESP in sheep. Intrauterine co-administration of IFNT and prostaglandin E2 synthase 1 (PGES-1) inhibitor reestablishes endometrial PGF2α pulses and regresses the CL. In contrast, intrauterine co-administration of IFNT and PGES-1 inhibitor along with intraovarian administration of PGE2 rescues the CL. Together, the accumulating information provides compelling evidence that PGE2 produced by the CL in response to endometrial PGE2 induced by pregnancy may counteract the luteolytic effect of PGF2α as an additional luteoprotective mechanism during MRP or ESP in ruminants. Targeting PGE2 biosynthesis and signaling selectively in the endometrium or CL may provide luteoprotective therapy to improve reproductive efficiency in ruminants.

Essential fatty acid supplementation during lactation is required to maximize the subsequent reproductive performance of the modern sow

This study was conducted to investigate the effects of supplemental essential fatty acids (EFA) on sow reproductive efficiency and to estimate the concentrations of EFA required by the lactating sow for maximum subsequent reproduction. Data were collected on 480 sows (PIC Camborough) balanced by parity, with 241 and 239 sows representing Parity 1, and 3-5 (P3+), respectively. Sows were assigned randomly, within parity, to a 3 × 3 factorial arrangement plus a control diet without added lipids. Factors included linoleic (2.1%, 2.7%, and 3.3%) and α-linolenic acid (0.15%, 0.30%, and 0.45%), obtained by adding 4% of different mixtures of canola, corn and flaxseed oils to diets. Diets were corn-soybean meal based with 12% wheat middlings. The benefits of supplemental EFA were more evident for the subsequent reproduction of mature P3+ sows. For these sows, supplemental α-linolenic acid improved the proportion of sows that farrowed relative to sows weaned (linear P=0.080; 82.8, 80.5, and 92.8% for sows fed 0.15%, 0.30%, and 0.45% α-linolenic acid, respectively). In addition, supplemental linoleic acid, fed to Parity 1 and P3+ sows, tended to increase subsequent litter size (linear P=0.074; 13.2, 13.8 and 14.0 total pigs born for 2.1%, 2.7% and 3.3% linoleic acid, respectively). These results demonstrate that a minimum dietary intake of both α-linolenic and linoleic acid is required for the modern lactating sow to achieve a maximum reproductive outcome through multiple mechanisms that include rapid return to estrus, increased maintenance of pregnancy and improved subsequent litter size.

BVDV alters uterine prostaglandin production during pregnancy recognition in cows

Embryonic mortality in cows is at least in part caused by failure of pregnancy recognition (PR). Evidence has shown that bovine viral diarrhoea virus (BVDV) infection can disrupt pregnancy. Prostaglandins (PG) play important roles in many reproductive processes, such as implantation. The aim of this study was to investigate the effect of BVDV infection on uterine PG production and PR using an in vitro PR model. Bovine uterine endometrial cells isolated from ten BVDV-free cows were cultured and treated with 0 or 100ng/mL interferon-τ (IFNT) in the absence or presence of non-cytopathic BVDV (ncpBVDV). PGF2α and PGE2 concentrations in the spent medium were measured using radioimmunoassays, and in the treated cells expression of the genes associated with PG production and signalling was quantified using qPCR. The results showed that the IFNT challenge significantly stimulated PTGS1 and PTGER3 mRNA expression and PGE2 production; however, these stimulatory effects were neutralised in the presence of ncpBVDV infection. ncpBVDV infection significantly increased PTGS1 and mPGES1 mRNA expression and decreased AKR1B1 expression, leading to increased PGE2 and decreased PGF2α concentrations and an increased PGE2:PGF2α ratio. The other tested genes, including PGR, ESR1, OXTR, PTGS2, PTGER2 and PTGFR, were not significantly altered by IFNT, ncpBVDV or their combination. Our study suggests that BVDV infection may impair PR by (1) inhibiting the effect of IFNT on uterine PG production and (2) inducing an endocrine switch of PG production from PGF2α to PGE2 to decrease uterine immunity, thereby predisposing the animals to uterine disease.

Prostaglandin F2α promotes angiogenesis and embryo-maternal interactions during implantation

Implantation in humans and other mammals is a critical period during which high embryonic mortality rates occur. Prostaglandins (PGs) are key mediators regulating interactions between the reproductive tract and the conceptus (embryo with extraembryonic membranes). Although the significance of PGF2α as a regulator of corpus luteum regression is well established, the role of its high amounts in the uterine lumen in most mammals, regardless of placentation type, during the implantation period remains unresolved. We hypothesized that PGF2α acting as an embryonic signal mediator contributes to pregnancy establishment. Using a porcine model, we demonstrated that the conceptus and its signal (estradiol-17β) elevated endometrial expression of PGF2α receptor (PTGFR) in vivo and in vitro PTGFR protein was expressed mainly in luminal epithelial (LE) and glandular epithelial cells and blood vessels in the endometrium. PGF2α stimulated the MAPK1/3 pathway in endometrial LE cells that coincided with elevated gene expression and secretion of endometrial vascular endothelial growth factor A (VEGFA) protein. PGF2α-PTGFR and adenylyl cyclase signaling were involved in this process. PGF2α-induced VEGFA acting through its receptors stimulated proliferation of endometrial endothelial cells. Moreover, PGF2α elevated gene expression of biglycan, matrix metalloproteinase 9, transforming growth factor β3, and interleukin 1α in the endometrium. In summary, our study indicates that PGF2α participates in pregnancy establishment by promoting angiogenesis and expression of genes involved in tissue remodeling and conceptus-maternal interactions in porcine endometrium during early pregnancy.

Leukotriene production profiles and actions in the bovine endometrium during the oestrous cycle

We have previously shown the influence of leukotrienes (LTs) on reproductive functions in vivo: LTB4 is luteotrophic and supports corpus luteum function inducing PGE2 and progesterone (P4) secretion, whereas LTC4 is luteolytic and stimulates PGF2α secretion in cattle. The aim of this study was to examine expression and production profiles of LTs and their actions in the endometrium. LT receptors (LTB4R for LTB4 and CysLTR2 for LTC4), 5-lipoxygenase (LO), 12-LO synthase (LTCS) and LTA4 hydrolase (LTAH) mRNA and protein expression, as well as LT production were measured in bovine endometrial tissue during the luteal phases of the oestrous cycle. The action of LTs on uterine function was studied by measuring the level of PGs after stimulating uterine slices with LTs on Days 8–10 of the cycle. Expression of 5-LO and LTB4R mRNA and protein were highest on Days 2–4 of the cycle, while CysLTR2 and LTCS were highest on Days 16–18 (P < 0.05). LTB4 concentration was highest on Days 2–4 of the cycle, whereas the greatest LTC4 level was on Days 16–18 (P < 0.05). Both LTB4 and C4 increased the content of PGE2 and F2α in endometrial slices at a dose of 10–7 M (P < 0.05). In summary, mRNA expression and activation of receptors for LTB4 and production occur in the first part of the cycle, whereas LTC4 and its receptors predominate at the end of the cycle. The 12-LO and 5-LO pathways are complementary routes of LT production in the bovine uterus.

Non-Invasive Pregnancy Diagnosis in Big Cats using the PGFM (13,14-dihydro-15-keto-PGF2α) Assay

Non-invasive monitoring of hormones using feces has become a vital tool for reproductive management and reliable pregnancy diagnosis in big cats. Previous studies described the PGF_2α metabolite (PGFM) as an indicator of pregnancy in various feline species. The present study aimed to standardize pregnancy detection in big cats like the tiger (Panthera tigris), jaguar (Panthera onca) and lion (Panthera leo) using fecal samples. High-performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometry (LCMS) were performed to identify PGFM in feces. An EIA developed against 9α,11α-dihydroxy-15-oxo-prost-5-en-1-oic acid-BSA was used to assay PGFM in fecal samples of the Bengal tiger, Asiatic lion and jaguar. The PGFM levels increased after 9 weeks of pregnancy and remained elevated until parturition. All animals showed elevated levels of PGFM in the last trimester of pregnancy, thus making PGFM a reliable tool for pregnancy diagnosis during this period that can be useful in captive breeding programs in these species.

Early pregnancy modulates survival and apoptosis pathways in the corpus luteum in sheep

The corpus luteum (CL) is a transient endocrine gland. Functional and structural demise of the CL allows a new estrous cycle. On the other hand, survival of CL and its secretion of progesterone are required for the establishment of pregnancy. Survival or apoptosis of the luteal cells is precisely controlled by interactions between survival and apoptosis pathways. Regulation of these cell signaling components during natural luteolysis and establishment of pregnancy is largely unknown in ruminants. The objective of the present study was to determine the regulation of survival and apoptosis signaling protein machinery in the CL on days 12, 14, and 16 of the estrous cycle and pregnancy in sheep. Results indicate that: i) expressions of p-ERK1/2, p-AKT, β-catenin, NFκB -p65, -p50, -p52, p-Src, p-β -arrestin, p-GSK3β, X-linked inhibitor of apoptosis protein (XIAP), and p-CREB proteins are suppressed during natural luteolysis; in contrast, their expressions are sustained or increased during establishment of pregnancy; ii) expressions of cleaved caspase-3, apoptosis inducing factor (AIF), c-Fos, c-Jun, and EGR-1 proteins are increased during natural luteolysis; in contrast, their expressions are decreased during establishment of pregnancy; and iii) expressions of Bcl-2, Bcl-XL, Bad, and Bax proteins are not modulated during natural luteolysis while expressions of Bcl2 and Bcl-XL proteins are increased during establishment of pregnancy in sheep. These proteomic changes are evident in both large and small luteal cells. These results together indicate that regression of the CL during natural luteolysis or survival of the CL during establishment of pregnancy is precisely controlled by distinct programmed suppression or activation of intraluteal cell survival and apoptosis pathways in sheep/ruminants.

Production of prostaglandins in placentae and corpus luteum in pregnant hinds of red deer (Cervus elaphus)

Prostaglandins (PGs) are synthesized from arachidonic acid by prostaglandin synthase 2 (PTGS2) and specific terminal PG synthases such as PGES and PGFS. The role of PGs in the reproductive processes of domestic ruminants is well recognized, whereas in cervidae, it is almost unknown, although it is noteworthy because some species of this family are valued in meat production and trophies. The aim of this study was to determine an effective marker of pregnancy and investigate the production and secretion of PGs in placenta and CL tissue in pregnancy. In the preliminary experiment, the levels of progesterone and 17-β estradiol (RIA; N = 14 divided into seven pregnant and seven nonpregnant hinds) were measured in the peripheral blood. In the main experiment, a comparison of messenger RNA (real-time polymerase chain reaction) and protein expression (Western blotting) of PTGS2, PGES, and PGFS, the level of prostaglandin E2 (PGE2) and PGF2α in the placentae and CL in pregnant hinds (aged 3-4 years, ca. 100 days of pregnancy, N = 6). In pregnant hinds, the level of progesterone in the blood was higher than that in nonpregnant hinds (P < 0.05), whereas the level of E2 was similar in all animals (P > 0.05). The highest messenger RNA expression of PTGS2, PGES, and PGFS was observed in the placentae than in the CL (P < 0.05). The protein expression of PTGS2 and PGES was elevated in the placentae compared with the CL (P < 0.05). The PGE2 output was the highest in cotyledonary tissue (P < 0.05). Pregnancy development in hinds around 100 days is regulated by arachidonic acid metabolites, especially PGE2 produced by the placentae, which production increases in pregnancy. Further studies are required to unravel the mechanisms involved in the regulation of PG and biosynthetic enzymes in uteroplacental and ovarian tissues during pregnancy in red deer females.

Relationships among nitric oxide metabolites and pulses of a PGF2α metabolite during and after luteolysis in mares

Hourly circulating concentrations of a PGF2α metabolite (PGFM), progesterone (P4), and LH were obtained from a reported project, and concentrations of nitric oxide (NO) metabolites (NOMs; nitrates and nitrites) were determined in eight mares. Unlike the reported project, hormone concentrations were normalized to the peak of the first PGFM pulse of luteolysis (early luteolysis), second PGFM pulse (late luteolysis), and a pulse after luteolysis. The duration of luteolysis was 23.1 ± 1.0 hours, and the peak of the first and second PGFM pulses occurred 6.5 ± 0.9 and 14.8 ± 0.8 hours after the beginning of luteolysis. Concentration of P4 decreased progressively within and between the PGFM pulses Changes were not detected in LH concentration in association with the PGFM pulses. Concentration of NOMs was greater (P < 0.05) at the peak of the PGFM pulse during early luteolysis (88.8 ± 15.0 μg/mL) than during late luteolysis (58.8 ± 9.0 μg/mL). Concentration of NOMs began to decrease (P < 0.05) 4 hours before the peak of the PGFM pulse of early luteolysis. Concentration began to increase (P < 0.05) an hour after the peak of the PGFM pulse of late luteolysis. An NOM decrease and increase was not detected during the PGFM pulse after luteolysis. On a temporal basis, results indicated that NO either is not required for luteolysis in mares or has a role in or responds only during late luteolysis. A caveat is that the relative contribution of the CL versus other body tissues to circulating concentrations of NOMs in mares has not been determined.

Impact of dietary lipids on sow milk composition and balance of essential fatty acids during lactation in prolific sows

Two studies were designed to determine the effects of supplementing diets with lipid sources of EFA (linoleic and α-linolenic acid) on sow milk composition to estimate the balance of EFA for sows nursing large litters. In Exp. 1, 30 sows, equally balanced by parity (1 and 3 to 5) and nursing 12 pigs, were fed diets supplemented with 6% animal-vegetable blend (A-V), 6% choice white grease (CWG), or a control diet without added lipid. Diets were corn-soybean meal based with 8% corn distiller dried grains with solubles and 6% wheat middlings and contained 3.25 g standardized ileal digestible Lys/Mcal ME. Sows fed lipid-supplemented diets secreted greater amounts of fat (P = 0.082; 499 and 559 g/d for control and lipid-added diets, respectively) than sows fed the control diet. The balance of EFA was computed as apparent ileal digestible intake of EFA minus the outflow of EFA in milk. For sows fed the control diet, the amount of linoleic acid secreted in milk was greater than the amount consumed, throughout lactation. This resulted in a pronounced negative balance of linoleic acid (-22.4, -38.0, and -14.1 g/d for d 3, 10, and 17 of lactation, respectively). In Exp. 2, 50 sows, equally balanced by parity and nursing 12 pigs, were randomly assigned to a 2 × 2 factorial arrangement of diets plus a control diet without added lipids. Factors included linoleic acid (2.1% and 3.3%) and α-linolenic acid (0.15% and 0.45%). The different concentrations of EFA were obtained by adding 4% of different mixtures of canola, corn, and flaxseed oils to diets. The n-6 to n-3 fatty acid ratios in the diets ranged from 5 to 22. Increasing supplemental EFA increased (P < 0.001) milk concentrations of linoleic (16.7% and 20.8%, for 2.1% and 3.3% linoleic acid, respectively) and α-linolenic acid (P < 0.001; 1.1 and 1.9% for 0.15 and 0.45% α-linolenic acid, respectively). Increasing supplemental EFA increased the estimated balance of α-linolenic acid (P < 0.001; -0.2 and 5.3 g/d for 0.15% and 0.45% α-linolenic acid, respectively), but not linoleic acid (P = 0.14; -3.4 and 10.0 g/d for 2.1% and 3.3% linoleic acid, respectively). In conclusion, lipid supplementation to sow lactation diets improved milk fat secretion. The fatty acid composition of milk fat reflected the dietary supplementation of EFA. The net effect of supplemental EFA was to create a positive balance during lactation, which may prove to be beneficial for the development of nursing piglets and the subsequent reproduction of sows.

Candidate genes underlying heritable differences in reproductive seasonality between wild and domestic rabbits

Reproductive seasonality is a trait that often differs between domestic animals and their wild ancestors, with domestic animals showing prolonged or even continuous breeding seasons. However, the genetic basis underlying this trait is still poorly understood for most species, and because environmental factors and resource availability are known to play an important role in determining breeding seasons, it is also not clear in most cases to what extent this phenotypic shift is determined by the more lenient captive conditions or by genetic factors. Here, using animals resulting from an initial cross between wild and domestic rabbits followed by two consecutive backcrosses (BC1 and BC2) to wild rabbits, we evaluated the yearly distribution of births for the different generations. Similar to domestic rabbits, F1 animals could be bred all year round but BC1 and BC2 animals showed a progressive and significant reduction in the span of the breeding season, providing experimental evidence that reduced seasonal breeding in domestic rabbits has a clear genetic component and is not a simple by-product of rearing conditions. We then took advantage of a recently published genome-wide scan of selection in the domesticated lineage and searched for candidate genes potentially associated with this phenotypic shift. Candidate genes located within regions targeted by selection include well-known examples of genes controlling clock functions (CRY1 and NR3C1) and reproduction (PRLR).

Altered secretion of selected arachidonic acid metabolites during subclinical endometritis relative to estrous cycle stage and grade of fibrosis in mares

Mares that fail to become pregnant after repeated breeding, without showing typical signs of clinical endometritis, should be suspected of subclinical endometritis (SE). Contact with infectious agents results in altered synthesis and secretion of inflammatory mediators, including cytokines and arachidonic acid metabolites, and disturbs endometrial functional balance. To address the hypothesis that SE affects the immune endocrine status of the equine endometrium, spontaneous secretion of prostaglandin E(2) (PGE(2)), prostaglandin F(2α) (PGF(2α)), 6-keto-PGF(1α )(a metabolite of prostacyclin I(2)), leukotriene B(4) (LTB(4)), and leukotriene C(4) (LTC(4)) was examined. In addition, secretion of these factors was examined relative to the grade of inflammation, fibrosis, and estrous cycle stage. Eighty-two warmblood mares, of known breeding history, were enrolled in this study. On the basis of histopathologic assessment, mares were classified as suffering from first-grade SE, second-grade SE, or being healthy. The grade of fibrosis and the infiltration of endometrial tissue with polymorphonuclear leukocytes were examined by routine hematoxylin-eosin staining. In mares suffering from SE, the secretion profiles of PGE(2), 6-keto-PGF(1α), LTB(4), and LTC(4) were changed compared to mares that did not suffer from endometritis. The secretion of PGE(2) and 6-keto-PGF1α was increased, whereas that of LTB(4) and LTC(4) was decreased. Secretion of 6-keto-PGF(1α) was increased in first- and second-grade SE (P < 0.01). The concentration of PGI(2) metabolite was increased only in inflamed endometrium, independently of the inflammation grade, but was not affected by fibrosis. Prostaglandin E(2) secretion was increased in second-grade SE (P < 0.05). The secretion of LTB(4) decreased in both first- and second-grade SE (P < 0.05), whereas secretion of LTC(4) was decreased only in second-grade SE (P < 0.05). Fibrosis did not change the secretion profile of PGE(2), PGF(2α), and 6-keto-PGF(1α) during the course of SE. However, the secretion profile of LTB(4) was affected during the course of fibrosis. Evident divergences between PGE(2) and PGF(2α) profiles and in PGE2:PGF(2α) ratios in the control versus SE mares observed during the course of diestrus contribute to shortened or prolonged interestrous intervals observed clinically in SE mares.