Expression of Cyclooxygenase-2 and Granulocyte-Macrophage Colony-Stimulating Factor in the Endometrial Epithelium of the Cow Is Up-Regulated During Early Pregnancy and in Response to Intrauterine Infusions of Interferon-τ1

Actions of FGF2, LIF, and IGF1 on bovine embryo survival and conceptus elongation following slow-rate freezing

Culture environment during in vitro embryo production can affect embryo phenotype and pregnancy outcomes, making culture modifications a logical approach for improving embryo competence. Previously, the addition of the growth factors FGF2, LIF, and IGF1, termed FLI, to the culture medium improved bovine embryo development, and re-expansion following cryopreservation. The objective of this study was to investigate the survival of cryopreserved FLI treated embryos at day 15 of pregnancy and evaluate conceptus transcriptomes. Embryos were produced using in vitro fertilization of abattoir-derived oocytes, cultured to the blastocyst stage in the presence or absence of FLI (+/- FLI), and cryopreserved by slow-rate freezing. Thawed embryos were transferred into non-lactating recipient beef cows and eight days later conceptuses were recovered and analyzed. For a subset of conceptuses whole transcriptome analysis was performed by using the NovaSeq 6000. There was no detectable difference in conceptus recovery or average conceptus length between the two groups. There were 32 differentially expressed transcripts, 23 up-regulated and nine down-regulated in the +FLI group compared to -FLI. Genes were involved in interferon signaling, prostaglandin synthesis, and placental development. This study reveals that embryos cultured with or without FLI and cryopreserved by slow-rate freezing have similar developmental competence up to day 15 of development. Nevertheless, differences in gene expression exhibit an effect of FLI on conceptus signaling during elongation.

Single-cell analysis of prostaglandin E2-induced human decidual cell in vitro differentiation: a minimal ancestral deciduogenic signal†

The decidua is a hallmark of reproduction in many placental mammals. Differentiation of decidual stromal cells is known to be induced by progesterone and the cyclic AMP/protein kinase A (cAMP/PKA) pathway. Several candidates have been identified as the physiological stimulus for adenylyl cyclase activation, but their relative importance remains unclear. To bypass this uncertainty, the standard approach for in vitro experiments uses membrane-permeable cAMP and progestin. We phylogenetically infer that prostaglandin E2 (PGE2) likely was the signal that ancestrally induced decidualization in conjunction with progesterone. This suggests that PGE2 and progestin should be able to activate the core gene regulatory network of decidual cells. To test this prediction, we performed a genome-wide study of gene expression in human endometrial fibroblasts decidualized with PGE2 and progestin. Comparison to a cAMP-based protocol revealed shared activation of core decidual genes and decreased induction of senescence-associated genes. Single-cell transcriptomics of PGE2-mediated decidualization revealed a distinct, early-activated state transitioning to a differentiated decidual state. PGE2-mediated decidualization was found to depend upon progestin-dependent induction of PGE2 receptor 2 (PTGER2) which in turn leads to PKA activation upon PGE2 stimulation. Progesterone-dependent induction of PTGER2 is absent in opossum, an outgroup taxon of placental mammals which is incapable of decidualization. Together, these findings suggest that the origin of decidualization involved the evolution of progesterone-dependent activation of the PGE2/PTGER2/PKA axis, facilitating entry into a PKA-dominant rather than AKT-dominant cellular state. We propose the use of PGE2 for in vitro decidualization as an alternative to 8-Br-cAMP.

Day 7 embryo quality and suboptimal uterine environment influence morphometry of Day 16 conceptus in dairy cows

The objectives of this study were to investigate the effect of Day 7 embryo quality and subclinical endometritis (SCE) in repeat breeder recipient cows on morphometry of Day 16 embryo and to determine the association of %PMN, serum progesterone and Day 16 conceptus length. Holstein dairy cows that failed to conceive at least 3 times, (parity, 3 and 4; body condition score, 3 to 3.5 out of 5) with subclinical endometritis (n = 180; SCE, >6% PMN on endometrial cytology) or without subclinical endometritis (n = 180; No-SCE, ≤ 6% PMN) were selected. Cows in each group received single, frozen-thawed, quality 1 (n = 60), 2 (n = 60) and 3 (n = 60) embryos (compact morula or early blastocyst) on Day 7 post estrus in the uterine horn ipsilateral to the ovary containing a corpus luteum, using standard nonsurgical techniques. Only cows that expressed estrus (Select-Synch protocol) and with acceptable corpus luteum (≥1.5 cm in size) were included. Conceptuses were collected on Day 16 from all recipient cows by standard non-surgical uterine flushing technique, using an 18-g embryo collection catheter with Phosphate Buffered Saline (pH 7.4). Blood samples were collected on Day 16 to determine serum progesterone concentrations. After collection, conceptuses were weighed and measured, and were categorized as tubular (underdeveloped, 10-20 mm) or filamentous (normal, >25 mm). Between cows with SCE and No-SCE, mean (±SEM) width (1.68 ± 0.13 mm vs. 1.84 ± 0.16 mm), length (34.4 ± 9.6 mm vs. 55.8 ± 13.4 mm) and weight (22.3 ± 3.7 vs. 40.6 ± 6.4 mg) of Day 16 conceptuses differed (P < 0.05). The mean width (1.75 ± 0.19 mm vs. 1.81 ± 0.22 mm), length (57.7 ± 11.2 vs. 51.1 ± 13.6 mm) and weight (34.3 ± 6.4 vs. 38.5 ± 8.2 mg) of Day 16 embryo following transfer of Day 7 embryo quality grade 1 and grade 2 embryos were not different (P > 0.1), but both differed from the mean width (1.59 ± 0.11 mm), length (28.9 ± 9.7 mm) and weight (25.3 ± 4.6 mg) of Day 16 embryo from Day 7 embryo quality grade 3 (P < 0.05). Total percentage of embryos recovered differed between SCE and No-SCE groups (P < 0.05; 36.1 vs 48.9%). Total percentage of embryos recovered on Day 16 following transfer of grade 1 (53.3%) and 2 (44.2%) Day 7 embryos were greater (P < 0.05) compared with transfer of grade 3 embryos (29.2%) (P < 0.001). Total percentage of filamentous embryos recovered was lower for SCE cows compared with No-SCE cows (P < 0.01; 15.0 vs. 25.6%). Total percentage of tubular embryos recovered did not differ between SCE and No-SCE cows (P > 0.1; 21.1% vs. 22.8%). Filamentous embryo recovered for grade 3 was lower (P < 0.05) compared with grade 1 in both SCE (8.3 vs. 21.7%) and No-SCE groups (15.0 vs. 33.3%). The mean (±SEM) CL volume (cm³; 11.8 ± 0.29 vs. 15.9 ± 0.31) and progesterone concentrations (ng/mL; 5.17 ± 1.8 vs. 8.2 ± 1.2) on Day 16 differed between SCE and No-SCE groups (P < 0.05) but not among Day 7 embryo grade groups (P > 0.1). The mean (±SEM) CL volume (cm³; 15.6 ± 0.28 vs 12.1 ± 3.9) and serum progesterone concentrations (ng/mL; 8.6 ± 1.4 vs. 4.9 ± 1.9) on Day 16 differed (P < 0.05) between cows yielded filamentous and tubular embryos. When all cows were considered, multiple regression analysis showed that the %PMN (P < 0.0001), progesterone concentrations (P < 0.0001), embryo qulaity (P < 0.05) and %PMN by progesterone interactions (P < 0.0001) influenced the length of Day 16 conceptus. Among cows without subclinical endometritis, only progesterone concentrations (P < 0.0001) and among cows with subclinical endometritis, only %PMN (P < 0.04) influenced the length of Day 16 conceptus. Progesterone concentrations (P < 0.0001) influenced the length of Day 16 conceptus in cows that received embryo quality 1 and 2. Progesterone concentration by %PMN interaction (P < 0.05) also influenced the length of Day 16 conceptus in cows that received embryo quality 2. The %PMN (P = 0.05) influenced the length of Day 16 conceptus in cows that received embryo quality 3. In conclusion, poor quality Day 7 embryo and presence of SCE negatively influenced early embryo development between Days 7 and 16 of gestation probably by dysregulated embryo-maternal interactions due to lower progesterone, prompting loss of the conceptus in sub-optimal uterine environment.

Overexpression of Fgf8 in the epidermis inhibits hair follicle development

The hair follicle is a classical model for studying epithelial-mesenchymal interactions. Given the critical role of fibroblast growth factor 8 (Fgf8) in embryonic development, we generated a mouse model that overexpresses Fgf8 specifically in the epidermis. Interestingly, these mutant mice exhibited stunted, smaller bodies and severe hypotrichosis. Histological analysis showed that the hair follicles in the mutants were arrested at stage 2 of hair development. The density of hair follicles in the mutant mice was also lower compared to that in the control mice. Overexpression of Fgf8 inhibited the proliferation of epidermal cells and simultaneously promoted apoptosis, leading to the arrest of hair follicle development. Further analysis showed that sonic hedgehog (Shh) and bone morphogenetic protein 4 (Bmp4) were downregulated and upregulated, respectively. To summarize, our study demonstrates that FGF signalling plays an important role in the regulation of hair follicle development.

Effects of human recombinant granulocyte-colony stimulating factor treatment during in vitro culture on porcine pre-implantation embryos

Granulocyte-colony stimulating factor (G-CSF), a pleiotropic cytokine, belongs to the hematopoietic growth factor family. Recent studies have reported that G-CSF is a predictive biomarker of oocyte and embryo developmental competence in humans. The aim of our study was to determine whether CSF3 and its receptor (CSF3R) were expressed in porcine maternal reproductive tissues (oviduct and uterus), cumulus cells, and embryos and to investigate the effects of human recombinant G-CSF (hrG-CSF) supplementation during in vitro culture (IVC) on the developmental competence of pre-implantation embryos. To do this, we first performed reverse-transcription polymerase chain reaction (RT-PCR). Second, we performed parthenogenetic activation (PA), in vitro fertilization (IVF), and somatic cell nuclear transfer (SCNT) to evaluate the embryonic developmental potential after hrG-CSF supplementation based on various concentrations (0 ng/mL, 10 ng/mL, 50 ng/mL, and 100 ng/mL) and durations (Un-treated, Days 0–3, Days 4–7, and Days 0–7) of IVC. Finally, we examined transcriptional levels of several marker genes in blastocysts. The results of our study showed that CSF3 transcript was present in all samples we assessed. CSF3-R was also detected, except in cumulus cells and blastocysts from PA. Furthermore, 10 ng/mL and Days 0–7 were the optimal concentration and duration for the viability of in vitro embryonic development, especially for SCNT-derived embryos. The rate of blastocyst formation and the total cell number of blastocysts were significantly enhanced, while the number and index of apoptotic nuclei were significantly decreased in optimal condition groups compared to others. Moreover, the transcriptional levels of anti-apoptotis- (BCL2), proliferation- (PCNA), and pluripotency- (POU5F1) related genes were dramatically upregulated. In conclusion, for the first time, we demonstrated that CSF3 and CSF3R were expressed in porcine reproductive organs, cells, and embryos. Additionally, we determined that hrG-CSF treatment improved porcine embryonic development capacity in vitro.

The BlastGen study: a randomized controlled trial of blastocyst media supplemented with granulocyte-macrophage colony-stimulating factor

RESEARCH QUESTION

Does Embryogen®/BlastGen™ culture medium improve live birth rates compared with standard culture medium for women undergoing IVF and intracytoplasmic sperm injection (ICSI) with poor prognosis.

DESIGN

Randomized clinical trial. A total of 100 couples undergoing IVF/ICSI were randomly allocated to having their inseminated oocytes incubated in either Embryogen®/BlastGen™ sequential culture media or standard Cleavage/Blastocyst sequential culture media for 5 days (ClinicalTrials.gov Identifier: NCT02305420).

RESULTS

No statistically significant difference in live birth rate was found between the control group and the Embryogen®/BlastGen™ group (17 [34%] versus 11 [22%], respectively) (OR 0.55; 95% CI 0.22 to 1.32; P = 0.18). After adjustment for maternal age, body mass index and fertilization procedure, the blastulation rate reduced (40.6 ± 26.5 versus 24.6 ± 26.7; RR 0.70, CI 0.52 to 0.95; P < 0.05), and grade of the embryo transferred (OR 0.35, CI 0.16 to 0.77; P < 0.01) when Embryogen®/BlastGen™ medium was used.

CONCLUSION

A significant reduction in day-5 embryo outcome parameters was found using Embryogen®/BlastGen™ compared with standard medium, and insufficient evidence of a difference in pregnancy outcomes. Taking into consideration the small samples size, study limitations and strict inclusion criteria of this single-centre study, further research is needed to determine the efficacy of Embryogen®/BlastGen™ medium in couples undergoing IVF/ICSI.

Prostaglandin-endoperoxide synthase 2 is not required for preimplantation ovine conceptus development in sheep

Conceptus development and elongation is required for successful pregnancy establishment in ruminants and is coincident with the production of interferon τ (IFNT) and prostaglandins (PGs). In both the conceptus trophectoderm and endometrium, PGs are primarily synthesized through a prostaglandin-endoperoxide synthase 2 (PTGS2) pathway and modify endometrial gene expression and thus histotroph composition in the uterine lumen to promote conceptus growth and survival. Chemical inhibition of PG production by both the endometrium and the conceptus prevented elongation in sheep. However, the contributions of conceptus-derived PGs to preimplantation conceptus development remain unclear. In this study, CRISPR-Cas9 genome editing was used to inactivate PTGS2 in ovine embryos to determine the role of PTGS2-derived PGs in conceptus development and elongation. PTGS2 edited conceptuses produced fewer PGs, but secreted similar amounts of IFNT to their Cas9 control counterparts and elongated normally. Expression of PTGS1 was lower in PTGS2 edited conceptuses, but PPARG expression and IFNT secretion were unaffected. Content of PGs in the uterine lumen was similar as was gene expression in the endometrium of ewes who received either Cas9 control or PTGS2 edited conceptuses. These results support the idea that intrinsic PTGS2-derived PGs are not required for preimplantation embryo or conceptus survival and development in sheep.

Bovine embryo elongation is altered due to maternal fatty acid supplementation

The pre-implantation period is prone to embryonic losses in bovine. Embryo-maternal communication is crucial to support embryo development. Thereby, factors of the uterine fluid (UF) are of specific importance. The maternal diet can affect the UF composition. Since omega 3 fatty acids (omega 3 FA) are considered to be beneficial for reproduction, we investigated if dietary omega 3 FA affected factors in the UF related to embryo elongation. Angus heifers (n = 37) were supplemented with either 450 g of rumen-protected fish oil (omega 3 FA) or sunflower oil (omega 6 FA) for a period of 8 weeks. Following cycle synchronization and artificial insemination, the uteri were flushed post mortem to recover the embryos on day 15 of pregnancy. The UF and tissue samples of endometrium and corpus luteum (CL) were collected. Strikingly, the embryo elongation in the omega 3 group was enhanced compared to the omega 6 group. No differences were observed in uterine prostaglandins, even though the endometrial concentration of their precursor arachidonic acid was reduced in omega 3 compared to omega 6 heifers. The dietary FA neither led to differential expression of target genes in endometrium nor CL nor to a differential abundance of low-density lipoprotein cholesterol, cortisol or amino acids in the UF. Interestingly, the omega 3 group displayed a higher plasma progesterone concentration during luteal growth than the omega 6 group, possibly promoting embryo elongation. Further research should include an ovarian perspective to understand the functional link between dietary omega 3 FA and reproductive outcome.

Mechanisms linking bovine viral diarrhea virus (BVDV) infection with infertility in cattle

Bovine viral diarrhea virus (BVDV) is an important infectious disease agent that causes significant reproductive and economic losses in the cattle industry worldwide. Although BVDV infection is known to cause poor fertility in cattle, a greater part of the underlying mechanisms particularly associated with early reproductive losses are not clearly understood. Previous studies reported viral compromise of reproductive function in infected bulls. In females, BVDV infection is thought to be capable of killing the oocyte, embryo or fetus directly, or to induce lesions that result in fetal abortion or malformation. BVDV infections may also induce immune dysfunction, and predispose cattle to other diseases that cause poor health and fertility. Other reports also suggested BVDV-induced disruption of the reproductive endocrine system, and a disruption of leukocyte and cytokine functions in the reproductive organs. More recent studies have provided evidence of viral-induced suppression of endometrial innate immunity that may predispose to uterine disease. Furthermore, there is new evidence that BVDV may potentially disrupt the maternal recognition of pregnancy or the immune protection of the conceptus. This review brings together the previous reports with the more recent findings, and attempts to explain some of the mechanisms linking this important virus to infertility in cattle.

Regulation of present and future development by maternal regulatory signals acting on the embryo during the morula to blastocyst transition - insights from the cow

The preimplantation embryo has a remarkable ability to execute its developmental program using regulatory information inherent within itself. Nonetheless, the uterine environment is rich in cell signaling molecules termed embryokines that act on the embryo during the morula-to-blastocyst transition, promoting blastocyst formation and programming the embryo for subsequent developmental events. Programming can not only affect developmental processes important for continuance of development in utero but also affect characteristics of the offspring during postnatal life. Given the importance of embryokines for regulation of embryonic development, it is likely that some causes of infertility involve aberrant secretion of embryokines by the uterus. Embryokines found to regulate development of the bovine embryo include insulin-like growth factor 1, colony stimulating factor 2 (CSF2), and dickkopf WNT signaling pathway inhibitor 1. Embryo responses to CSF2 exhibit sexual dimorphism, suggesting that sex-specific programming of postnatal function is caused by maternal signals acting on the embryo during the preimplantation period that regulate male embryos differently than female embryos.

Exacerbated conceptus signaling does not favor establishment of pregnancy in beef cattle

Background

Insufficient production of anti-luteolytic signals by the pre-attachment embryo is considered a major cause of pregnancy failure in cattle. We tested the hypothesis that transfer of multiple blastocysts (n = 5/recipient) and progesterone (P4) supplementation amplify anti-luteolytic signaling and reduce embryonic losses in beef cattle. Cows detected in estrus (D0; n = 104) were assigned randomly to receive 150 mg of injectable long-acting P4 (iP4) or vehicle (non-iP4) on D4 and transcervical transfer of none or five, grade 1, not-frozen, in vitro-produced blastocysts, on D7. Luteal development and time of structural luteolysis were monitored by ultrasonography. Plasma P4 concentrations were determined on D4, D5 and D7, and daily between D14 and D20. Conceptus signaling was monitored by transcript abundance of interferon-stimulated gene 15 (ISG15) in peripheral blood mononuclear cells isolated on D14, D16, D18 and D20. Early embryonic mortality (EEM) was defined as the absence of ISG15 mRNA upregulation over time and/or luteal regression up to D20. Late embryonic mortality (LEM) was defined as the absence of a conceptus with a heartbeat on pregnancy diagnosis at D30 (PD30) after observing upregulation of ISG15 mRNA and extension of luteal lifespan. Pregnant cows presented conceptuses with heartbeat at PD30.

Results

On D5, iP4-treated cows had P4 concentrations 2.07-fold greater than non-iP4 treated (P < 0.001). On D7, P4 concentrations were similar. Pregnant and LEM animals showed a progressive increase in the abundance of ISG15 from D14 to D20. iP4-treated cows detected pregnant at PD30 had 1.53-fold greater abundance of ISG15 mRNA between D14 and D20 than non-iP4 treated cows (P = 0.05). iP4 doubled the frequency of EEM while it did not affect LEM. At PD30, embryonic survival was 37.0% vs. 55.6% for iP4-treated vs. control cows. Majority of pregnant cows (71%) presented only a single viable embryo.

Conclusions

A substantial proportion of cows had EEM (31%) and LEM (20%) even after transferring multiple blastocysts. This argues that mortality was due to poor uterine receptivity that could not be reversed by supplemental P4 or overcome by transferring multiple blastocysts. Further, a given uterine environment was not necessarily adequate to all embryos.

Insights into conceptus elongation and establishment of pregnancy in ruminants

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

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.

Differences in mRNA populations of short and long bovine conceptuses on Day 15 of gestation

The majority of pregnancy loss in cattle occurs between Days 8 and 16 of gestation, coincident with the initiation of conceptus elongation and the onset of maternal recognition of pregnancy. Differences in conceptus length on the same day of gestation may be related to an inherent lack of developmental competency or may simply be a consequence of asynchrony with the maternal environment. The objective of this work was to characterize differential patterns of mRNA expression between short and long bovine conceptuses recovered on Day 15 of gestation. Embryos were produced from super-ovulated Holstein donor cows, and groups of Grade-1 and Grade-3 compact morulas were transferred into recipient heifers at Day 6.5 of their cycle. Conceptuses were recovered at Day 15 of gestation, and measured to assess overall length and area. Total RNA was extracted and analyzed on individual GeneChip Bovine Genome Arrays (Affymetrix, Santa Clara, CA). Gene expression was compared between conceptuses derived from the transfer of Grade-1 versus Grade-3 embryos; no differences were identified in the profiles of Day-15 conceptuses of these different embryo grades. When gene expression was compared between conceptuses classified as either short (mean length of 4.2 ± 0.1 mm [standard error]) or long (24.7 ± 1.9 mm) upon recovery at Day 15 of gestation, a total of 348 genes were differentially expressed. Of these, 221 genes were up-regulated and 127 were down-regulated in long compared to short conceptuses. In summary, differences in gene expression were identified between conceptuses recovered on Day 15 of gestation, based on their length. These data may be used to identify genes and cellular pathways involved in enhanced conceptus elongation that could serve as markers of successful pregnancy. Mol. Reprod. Dev. 83: 424-441, 2016. © 2016 Wiley Periodicals, Inc.

Multiple-embryo transfer for studying very early maternal-embryo interactions in cattle

In the present paper, we highlight the need to study very early maternal-embryo interactions and discuss how these interactions can be addressed. Bovine species normally carry one or, less frequently, two embryos to term; there are very rare cases of triplets or higher-order multiple pregnancies in which all the offspring are born alive. Multiple-embryo transfer (MET) in cattle allows for the detection of endometrial responses in scenarios where single-embryo transfer would not. Although MET is non-physiological, the present study shows that at the very early embryonic stages, a uterus carrying zona-enclosed embryos does not exhibit non-physiological reactions. On the contrary, MET should be considered the sum of multiple individual effects triggered by developing embryos. We provide arguments to support our hypothesis that describe a rationale for current work with MET, and we discuss alternative hypotheses. Using cattle as a model, we describe how technical approaches to analyzing zona-enclosed early embryo-maternal interactions (i.e., transcriptomics, proteomics, and endometrial cell culture) can help identify molecular changes that may be difficult to observe when only a single embryo is present. We conclude that MET can be used for studying very early maternal-embryo interactions in vivo in monotocous species. Free Spanish abstract: A Spanish translation of this abstract is freely available at http://www.reproduction-online.org/content/150/2/R35/suppl/DC1.

Conceptus elongation in ruminants: roles of progesterone, prostaglandin, interferon tau and cortisol

The majority of pregnancy loss in ruminants occurs during the first three weeks after conception, particularly during the period of conceptus elongation that occurs prior to pregnancy recognition and implantation. This review integrates established and new information on the biological role of ovarian progesterone (P4), prostaglandins (PGs), interferon tau (IFNT) and cortisol in endometrial function and conceptus elongation. Progesterone is secreted by the ovarian corpus luteum (CL) and is the unequivocal hormone of pregnancy. Prostaglandins (PGs) and cortisol are produced by both the epithelial cells of the endometrium and the trophectoderm of the elongating conceptus. In contrast, IFNT is produced solely by the conceptus trophectoderm and is the maternal recognition of pregnancy signal that inhibits production of luteolytic pulses of PGF_2α by the endometrium to maintain the CL and thus production of P4. Available results in sheep support the idea that the individual, interactive, and coordinated actions of P4, PGs, IFNT and cortisol regulate conceptus elongation and implantation by controlling expression of genes in the endometrium and/or trophectoderm. An increased knowledge of conceptus-endometrial interactions during early pregnancy in ruminants is necessary to understand and elucidate the causes of infertility and recurrent early pregnancy loss and provide new strategies to improve fertility and thus reproductive efficiency.

Proliferation-stimulating effect of colony stimulating factor 2 on porcine trophectoderm cells is mediated by activation of phosphatidylinositol 3-kinase and extracellular signal-regulated kinase 1/2 mitogen-activated protein kinase

Colony-stimulating factor 2 (CSF2), also known as granulocyte macrophage colony-stimulating factor, facilitates mammalian embryonic development and implantation. However, biological functions and regulatory mechanisms of action of porcine endometrial CSF2 in peri-implantation events have not been elucidated. The aim of present study was to determine changes in cellular activities induced by CSFs and to access CSF2-induced intracellular signaling in porcine primary trophectoderm (pTr) cells. Differences in expression of CSF2 mRNA in endometrium from cyclic and pregnant gilts were evaluated. Endometrial CSF2 mRNA expression increases during the peri-implantation period, Days 10 to 14 of pregnancy, as compared to the estrous cycle. pTr cells obtained in Day 12 of pregnancy were cultured in the presence or absence of CSF2 (20 ng/ml) and LY294002 (20 µM), U0126 (20 µM), rapamycin (20 nM), and SB203580 (20 µM). CSF2 in pTr cell culture medium at 20 ng/ml significantly induced phosphorylation of AKT1, ERK1/2, MTOR, p70RSK and RPS6 protein, but not STAT3 protein. Also, the PI3K specific inhibitor (LY294002) abolished CSF2-induced increases in p-ERK1/2 and p-MTOR proteins, as well as CSF2-induced phosphorylation of AKT1. Changes in proliferation and migration of pTr cells in response to CSF2 were examined in dose- and time-response experiments. CSF2 significantly stimulated pTr cell proliferation and, U0126, rapamycin and LY294002 blocked this CSF2-induced proliferation of pTr cells. Collectively, during the peri-implantation phase of pregnancy in pigs, endometrial CSF2 stimulates proliferation of trophectoderm cells by activation of the PI3K-and ERK1/2 MAPK-dependent MTOR signal transduction cascades.

Effects of seminal plasma and the presence of a conceptus on regulation of lymphocyte-cytokine network in porcine endometrium

Infusion of seminal plasma in the uterus is known to elicit an instant inflammatory response in the porcine uterus, but whether or not it prepares a uterine immunological response to the presence of conceptuses is not well understood. Seminal plasma induced long-term modulatory effects and conceptus-induced immune changes in leukocyte populations were measured by flow cytometry and mRNAs for various cytokines by quantitative reverse-transcriptase PCR in porcine endometrium collected on Days 6 and 13 from cycling and pregnant animals or from animals given seminal plasma infusions. Seminal plasma infusion induced long-term modulatory effects, resulting in significantly more endometrial FoxP3-positive T-regulatory and T-helper cells 6 days after infusion as compared to cycling and pregnant animals. The number of T-cytotoxic and T-null cells did not change between the studied groups. The early molecular effects of seminal plasma were not observed at 13-days post-infusion, although animals on Day 13 of pregnancy did show significantly more T-cells (of any type investigated). Seminal plasma also showed a delayed effect on cytokine expression, specifically exhibiting a significant increase in interleukin 10 (IL10) and a decrease in granulocyte macrophage colony-stimulating factor (GMCSF) gene expression on Day 13 as compared to Day 6 of cycling or pregnant gilts. The results indicate a delayed regulatory effect of seminal plasma on immune responses in the porcine uterus, which are similar to immune changes generated by implanting conceptuses.

Hosting the preimplantation embryo: potentials and limitations of different approaches for analysing embryo - endometrium interactions in cattle

Ongoing detailed investigations into embryo–maternal communication before implantation reveal that during early embryonic development a plethora of events are taking place. During the sexual cycle, remodelling and differentiation processes in the endometrium are controlled by ovarian hormones, mainly progesterone, to provide a suitable environment for establishment of pregnancy. In addition, embryonic signalling molecules initiate further sequences of events; of these molecules, prostaglandins are discussed herein as specifically important. Inadequate receptivity may impede preimplantation development and implantation, leading to embryonic losses. Because there are multiple factors affecting fertility, receptivity is difficult to comprehend. This review addresses different models and methods that are currently used and discusses their respective potentials and limitations in distinguishing key messages out of molecular twitter. Transcriptome, proteome and metabolome analyses generate comprehensive information and provide starting points for hypotheses, which need to be substantiated using further confirmatory methods. Appropriate in vivo and in vitro models are needed to disentangle the effects of participating factors in the embryo–maternal dialogue and to help distinguish associations from causalities. One interesting model is the study of somatic cell nuclear transfer embryos in normal recipient heifers. A multidisciplinary approach is needed to properly assess the importance of the uterine milieu for embryonic development and to use the large number of new findings to solve long-standing issues regarding fertility.

Transcriptional profiling to address molecular determinants of endometrial receptivity--lessons from studies in livestock species

The development of a fertilized oocyte into a differentiated multi-cellular organism is a major challenge with regard to the orchestration of the expression of the mammalian genome. Highly complex networks of genes are temporally and spatially regulated during cellular differentiation to generate specific cell types. Embryonic development is critically influenced by external impacts in the female reproductive tract. A most critical phase of pregnancy in mammals is the pre- and peri-implantation period, during which the uterine environment plays a crucial role in supporting the development of the conceptus. The analytical description of the transcriptome, proteome and metabolome of the embryo-maternal interface is a prerequisite for the understanding of the complex regulatory processes taking place during this time. This review lines out potentials and limitations of different approaches to unravel the determinants of endometrial receptivity in cattle, the pig and the horse. Suitable in vivo and in vitro models, which have been used to elucidate factors participating in the embryo-maternal dialog are discussed. Taken together, transcriptome analyses and specified selective candidate gene driven approaches contribute to the understanding of endometrial function. The endometrium as sensor and driver of fertility may indicate the qualitative and quantitative nature of signaling molecules sent by the early embryo and in turn, accordingly impact on embryonic development.

Transcriptomic analysis of the bovine endometrium: What is required to establish uterine receptivity to implantation in cattle?

In cattle, the majority of pregnancy loss can be attributed to early embryonic loss which occurs prior maternal recognition of pregnancy on Day 16 (Day 0 = ovulation). During this time, carefully orchestrated spatio-temporal alterations in the transcriptomic profile of the endometrium are required to drive conceptus elongation, via secretions from the endometrium (termed histotroph) and establish uterine receptivity to implantation. The two main modulators of these processed are progesterone (P4) and the pregnancy recognition signal interferon tau (IFNT). Altered concentrations of P4 in circulation mediate its effects via the endometrium and have been associated with different rates of conceptus elongation in cattle. Transcriptomic analysis of the endometrium has shown that modulation of circulating P4 alters endometrial expression of genes that can contribute to histotroph composition, which is beneficial (when P4 is supplemented) or detrimental (when P4 is reduced) to the developing conceptus. In addition, down-regulation of the progesterone receptor, required to establish uterine receptivity, is altered in the endometrium of heifers with altered P4 concentrations. IFNT, a type 1 interferon, also significantly impacts on the endometrial transcriptome. It induces the expression of a large number of classical interferon stimulated genes as early as Day 15 of pregnancy. In summary, the successful establishment of pregnancy in cattle requires a sequence of key events to ensure appropriate maternally derived secretions, establish uterine receptivity to implantation as well as an adequate endometrial response to IFNT production.

Porcine granulocyte-macrophage colony-stimulating factor improves the in vitro development of cloned porcine embryos

We examined the effects of porcine granulocyte-macrophage colony-stimulating factor (pGM-CSF) on the in vitro development of porcine embryos produced by somatic cell nuclear transfer (SCNT) for the first time. We evaluated the effects of pGM-CSF on SCNT-derived blastocyst formation and investigated gene expression. A total of 522 cloned embryos in 6 replicates were treated with 10 ng/ml pGM-CSF during in vitro culture (IVC). This treatment significantly (P<0.05) increased blastocyst formation and total cell number in blastocysts compared with the control (12.3% and 41.4 vs. 9.0% and 34.7, respectively). However, there was no effect on cleavage rate. The numbers of cells in the inner cell mass and trophectoderm were significantly higher in the pGM-CSF treatment group (6.0 and 43.0, respectively) compared with the control (4.4 and 31.9, respectively). Treatment with 10 ng/ml pGM-CSF significantly increased POU5F1 and Cdx2 mRNA expression in blastocysts. In addition, Bcl-2, Dnmt1 and proliferating cell nuclear antigen (PCNA) mRNA expression were upregulated in blastocysts in the pGM-CSF supplemented group compared with the control. These results suggest that pGM-CSF improves the quality and developmental viability of porcine SCNT embryos by regulating transcription factor expression.

Early pregnancy induced expression of prostaglandin E2 receptors EP2 and EP4 in the ovine endometrium and regulated by interferon tau through multiple cell signaling pathways

Prostaglandin E2 (PGE(2)) plays pleiotropic roles at fetal-maternal interface during establishment of pregnancy. The objectives of the study were to: (i) determine regulation of PGE2 receptors EP1, EP2, EP3, and EP4 in the endometrium during the estrous cycle and early pregnancy; and (ii) understand endometrial epithelial and stromal cell-specific hormonal regulation of EP2 and EP4 in sheep. Results indicate that: (i) early pregnancy induces expression of EP2 and EP4 but not EP1 and EP3 proteins in the endometrium on days 12-16 compared to that of estrous cycle; (ii) intrauterine infusion of interferon tau (IFNT) increases expression of EP2 and EP4 proteins in endometrium; and (iii) IFNT activates distinct epithelial and stromal cell-specific JAK, EGFR, ERK1/2, AKT, or JNK signaling module to regulate expression of EP2 and EP4 proteins in the ovine endometrium. Our results indicate a role for EP2 and EP4-mediated PGE(2) signaling in endometrial functions and establishment of pregnancy in ruminants.

Effects of porcine granulocyte-macrophage colony-stimulating factor on porcine in vitro-fertilized embryos

This study investigated the effects of porcine granulocyte-macrophage colony-stimulating factor (pGM-CSF) on the developmental potential of porcine in vitro-fertilized (IVF) embryos in chemically and semidefined (with BSA) medium. In experiment 1, zygotes were treated with different concentrations of pGM-CSF (0, 2, 10, 100 ng/mL). The results indicated that 10 ng/mL pGM-CSF significantly (P < 0.05) increased blastocyst development and total cell number (15.1% and 53.5, respectively) compared with the control (6.1%, and 38.8, respectively). Comparing blastocyst formation, early and expanded blastocyst formation was significantly higher in the 10 ng/mL-pGM-CSF group than in the control on Days 6 and 7 of the culture period. However, there was no significant difference in cleavage rate. Experiment 2 demonstrated that pGM-CSF influenced the percentage of blastocyst formation and total cell number when pGM-CSF was added during Days 4 to 7 (14.6% and 53.9, respectively) or Days 0 to 7 (15.2% and 54.0, respectively) compared with the control (7.8% and 43.1, respectively) and compared with Days 0 to 3 (8.7% and 42.5, respectively). Similarly, early blastocyst formation rates were significantly higher at Days 4 to 7 than in the control, and expanded blastocyst formation was significantly higher at Days 4 to 7 or Days 0 to 7. No significant difference in cleavage rates appeared among the groups. In experiment 3, in the presence of BSA, pGM-CSF also increased the percentage of embryos that developed to the blastocyst stage and the total cell number (20.3% and 59.8, respectively) compared with the control (14.9% and 51.4, respectively), whereas there was no significant difference in cleavage rate. Experiment 4 found that the total cell number and the number of cells in the inner cell mass (ICM) were significantly increased compared with the control when zygotes were cultured in either porcine zygotic medium (PZM)-3 or PZM-4 supplemented with 10 ng/mL pGM-CSF. The number of trophectoderm (TE) cells was significantly higher in PZM-3 medium supplemented with pGM-CSF than in the control, and the number tended to increase (P = 0.058) in PZM-4 medium supplemented with pGM-CSF. The ratio of inner cell mass to trophectoderm cells was significantly higher in PZM-4 supplemented with 10 ng/mL pGM-CSF, but not in PZM-3. In experiment 5, it was found that the male pronuclear formation rate, monospermic penetration and sperm/oocyte were 95.4%, 37.2%, and 2.4, respectively. Together, these results suggest that pGM-CSF may have a physiological role in promoting the development of porcine preimplantation embryos and regulating cell viability and that addition of pGM-CSF to IVC medium at Days 4 to 7 or 0 to 7 improves the developmental potential of porcine IVF embryos.

Improving post-transfer survival of bovine embryos produced in vitro: actions of insulin-like growth factor-1, colony stimulating factor-2 and hyaluronan

Technologies for in vitro embryo production have the potential to enhance the efficiency of cattle production systems. However, utilization of in vitro-produced embryos for transfer remains limited throughout much of the world. Despite improvements over the past two decades, problems associated with the production of bovine embryos in vitro still exist which limit the widespread commercial application of this technology. In particular, bovine embryos produced in vitro have a reduced capacity to establish and maintain pregnancy as compared with their in vivo-derived counterparts. Embryo competence for survival following transfer is improved by in vivo culture in the sheep oviduct, thus indicating that standard embryo culture conditions are sub-optimal. Therefore, one strategy to improve post-transfer survival is to modify embryo culture media to more closely mimic the in vivo microenvironment. The maternal environment in which the bovine embryo develops in vivo contains various growth factors, cytokines, hormones, and other regulatory molecules. In addition to affecting bovine embryo development in vitro, recent research indicates that embryo competence for survival following transfer can also be improved when such molecules are added to embryo culture medium. Among the specific molecules that can increase post-transfer embryo survival are insulin-like growth factor-1 (IGF-1), colony stimulating factor-2 (CSF-2) and hyaluronan. This paper will review the effects IGF-1, CSF-2 and hyaluronan on post-culture embryo viability and discuss the potential mechanisms through which each of these molecules improves post-transfer survival.

Modification of endometrial fatty acid concentrations by the pre-implantation conceptus in pasture-fed dairy cows

The current study determined whether the pre-implantation conceptus modified endometrial fatty acid concentrations. Oestrus was synchronized in 14 mature lactating cows and embryos were transferred on day 7. Cows were slaughtered 10 d later, with each uterine horn flushed, the pre-implantation conceptus located, and inter-caruncular endometrial tissue collected from the gravid horn (containing the pre-implantation conceptus) and non-gravid horn. Endometrial fatty acid concentrations in the gravid and non-gravid horn were compared using linear models in restricted maxiumum likelihood. Investigations of the correlations among selected fatty acids and trophoblast weight or uterine fluid interferon-tau (IFN-τ) concentrations were also undertaken. The presence of the pre-implantation conceptus had relatively minor effects on endometrial fatty acid concentrations, but the ω6:ω3 ratio was greater and concentrations of stearic and oleic acid were slightly increased in the gravid horn. In the gravid horn, a negative linear relationship between the concentration of arachidonic acid and conceptus weight and IFN-τ concentration in the uterine luminal fluid were observed. In contrast, there was a positive relationship between concentrations of dihomo-γ-linolenic acid in the non-gravid horn and conceptus weight. In conclusion, the presence of the pre-implantation conceptus appears to modulate endometrial fatty acids, as indicated by the differences in endometrial fatty acid concentrations in the gravid and non-gravid uterine horns. The physiological implication of these local effects of the pre-implantation conceptus, on reproductive success requires further investigation.

Colony-stimulating factor 2 inhibits induction of apoptosis in the bovine preimplantation embryo

PROBLEM

Addition of colony-stimulating factor 2 (CSF2) to culture medium increases post-transfer survival of bovine embryos. Here we provide evidence that one mechanism by which CSF2 affects the embryo is through inhibition of apoptosis.

METHOD OF STUDY

In the first experiment, genes and pathways whose expression were regulated by CSF2 were identified by microarray analysis. Embryos were treated with 10 ng/ml CSF2 or vehicle at Day 5 after insemination; morulae were selected for microarray analysis at Day 6. In a second experiment, antiapoptotic effects of CSF2 were determined. Embryos were treated with CSF2 or vehicle at Day 5. On Day 6 (24 h after treatment), morulae were cultured for 15 h at either 42°C (a temperature that induces apoptosis) or 38.5°C (cow body temperature).

RESULTS

In the first experiment, a total of 214 genes were differentially regulated and 160 of these could be annotated (67 upregulated genes and 93 downregulated genes). Differentially expressed genes could be placed in 13 biological process ontologies in four functional groups (development and differentiation process, cell communication, apoptosis and cell adhesion). Antiapoptotic effects of CSF2 were confirmed in the second experiment because the magnitude of the increase in TUNEL positive cells caused by heat shock was reduced by CSF2.

CONCLUSION

CSF2 blocks apoptosis in bovine embryos through actions associated with regulation of genes controlling apoptosis.

Effects of gamete source and culture conditions on the competence of in vitro-produced embryos for post-transfer survival in cattle

One limitation to the use of in vitro-produced embryos in cattle production systems is the fact that pregnancy rates after transfer to recipients are typically lower than when embryos produced in vivo are transferred. Conceptually, the oocyte and spermatozoon from which the embryo is derived could affect competence for post-transfer survival. There are sire differences in embryonic survival after transfer, but there is little evidence that an embryo's ability to establish pregnancy is determined by sex sorting of spermatozoa by flow cytometry. The role of the source of the oocyte as a determinant of embryonic survival after transfer has not been examined carefully. Conditions for embryo culture after fertilisation can have an impact on the ability of the embryo to establish pregnancy following transfer. Among the specific molecules produced in the reproductive tract of the cow that have been shown to improve competence of in vitro-produced embryos for post-transfer survival are colony-stimulating factor 2, insulin-like growth factor-1 (for recipients exposed to heat stress) and hyaluronan (for less-advanced embryos). There is also a report that embryo competence for post-transfer survival can be improved by inclusion of a carbon-activated air filtration system in the incubator used to culture embryos. Progress in developing culture systems to improve embryonic competence for survival after transfer would be hastened by the development of in vitro assays that accurately predict the potential of an embryo to establish pregnancy after transfer. A group of 52 genes has been identified that are differentially expressed in embryos that developed to term v. embryos that did not establish pregnancy. Perhaps a gene microarray consisting of these genes, alone or in combination with other genes, could be used to screen embryos for competence to establish pregnancy.

Colony-stimulating factor 2 (CSF-2) improves development and posttransfer survival of bovine embryos produced in vitro

In this study, we tested the role of colony-stimulating factor 2 (CSF2) as one of the regulatory molecules that mediate maternal effects on embryonic development during the preimplantation period. Our objective was to verify effects of CSF2 on blastocyst yield, determine posttransfer survival, and evaluate properties of the blastocyst formed after CSF2 treatment. In vitro, CSF2 increased the percentage of oocytes that became morulae and blastocysts. Blastocysts that were treated with CSF2 tended to have a greater number of inner cell mass cells and had a higher ratio of inner cell mass to trophectoderm cells. There was no effect of CSF2 on the incidence of apoptosis. Treatment with CSF2 from d 5 to 7 after insemination increased embryonic survival as indicated by improved pregnancy rate at d 30-35 of gestation. Moreover, treatment with CSF2 from either d 1-7 or 5-7 after insemination reduced pregnancy loss after d 30-35. Results indicate that treatment with CSF2 can affect embryonic development and enhance embryo competence for posttransfer survival. The fact that treatment with CSF2 during such a narrow window of development altered embryonic function much later in pregnancy suggests that CSF2 may exert epigenetic effects on the developing embryo that result in persistent changes in function during the embryonic and fetal periods of development.

Quantitative characterization of prostaglandins in the uterus of early pregnant cattle

Prostaglandins (PGs) are important regulators of reproductive processes including early embryonic development. We analyzed the most relevant PG in bovine uteri at different preimplantation pregnancy stages when compared with non-pregnant controls. Additionally, endometrium and trophoblast tissues were examined regarding specific enzymes and receptors involved in PG generation and function. Simmental heifers were artificially inseminated or received seminal plasma only. At days 12, 15, or 18, post-estrus uteri were flushed for PG determination by liquid chromatography–tandem mass spectrometry. Endometrium and trophoblast tissues were sampled for RNA extraction and quantitative real-time PCR analysis. At all days and points of time examined, the concentration of 6-keto PGF1α (stable metabolite of PGI2) was predominant followed by PGF2α>PGE2>PGD2≈TXB2 (stable metabolite of TXA2). At days 15 and 18, PG increased from overall low levels at day 12, with a much more pronounced increase during pregnancy. The PGF2α/PGE2 ratio was not influenced by status. The highest PG concentration was measured at day 15 with 6-keto PGF1α (6.4 ng/ml) followed by PGF2α (1.1 ng/ml) and PGE2 (0.3 ng/ml). Minor changes in endometrial PG biosynthesis enzymes occurred due to pregnancy. Trophoblasts revealed high transcript abundance of general and specific PG synthases contributing to uterine PG. As PGI2 and PGF2α receptors were abundantly expressed by the trophoblast, abundant amounts of PGI2 and PGF2α in the uterine lumen point towards an essential role of PG for the developing embryo. High amounts of PG other than PGE2 in the preimplantation uterus may be essential rather than detrimental for successful reproduction.

Oxytocin receptor down-regulation is not necessary for reducing oxytocin-induced prostaglandin F(2alpha) accumulation by interferon-tau in a bovine endometrial epithelial cell line

Interferon-tau (IFNtau) is the embryonic signal responsible for pregnancy recognition in ruminants. The primary action of IFNtau is believed to be mediated through inhibition of prostaglandin F(2alpha) (PGF(2alpha)) released from the endometrial epithelial cells in response to oxytocin (OT). Our working hypothesis was that the antiluteolytic effect of IFNtau also involved modulation of PG production downstream of OT receptor (OTR) and/or cyclooxygenase 2 (COX2). There is currently no OT-sensitive endometrial cell line to study the molecular mechanisms underlying our hypotheses. Therefore, we established an immortalized bovine endometrial epithelial cell line (bEEL) exhibiting OT response. These cells were cytokeratin positive, expressed steroid receptors, and exhibited preferential accumulation of PGF(2alpha) over PGE(2). The bEEL cells were highly sensitive to OT, showing time- and concentration-dependent increase in COX2 transcript and protein and PGF(2alpha) accumulation. Interestingly, IFNtau (20 ng/ml) significantly reduced OT-induced PGF(2alpha) accumulation, but surprisingly, the effect was not mediated through down-regulation of either OTR or COX2. Rather, IFNtau up-regulated COX2 in a time- and concentration-dependent manner while decreasing OT-induced PG accumulation. This suggests that COX2 is not a primary target for the antiluteolytic effect of IFNtau. Because IFNtau reduced OT-stimulated PGF(2alpha) accumulation within 3 h, the mechanism likely involves a direct interference at the level of the OT signaling or transcription in addition to the down-regulation of OTR observed in vivo. In summary, bEEL cells offer a unique in vitro model for investigating the cellular and molecular mechanisms underlying OT and IFNtau response in relation with luteolysis and recognition of pregnancy in the bovine.

Effect of meloxicam treatment during early pregnancy in Holstein heifers

We previously reported that administration of flunixin meglumine two times at a critical stage approaching pregnancy recognition associated with maintenance of the corpus luteum (CL) increased early embryo survival and pregnancy rate via an additive antiluteolytic effect with the conceptus [Vet Rec 160 (2007) 404]. In this study, the objective was to determine if a single administration of meloxicam, a non-steroid anti-inflammatory drug with a longer half-life, could be used instead of flunixin meglumine. This would avoid repeated injections in heifers following insemination at a critical stage to increase pregnancy rate due to its inhibitory effect on prostaglandin F(2alpha) synthesis. Eighty-five, 15- to 18-month-old Holstein heifers were synchronized, and following insemination (day 0) heifers were assigned to receive subcutaneous meloxicam injection (0.5 mg/kg; n = 37) on the afternoon of day 15 or were untreated as a control (n = 48). Pregnancy rates were defined as the percentage of heifers inseminated that were diagnosed pregnant by ultrasound between days 31 and 38 after artificial insemination. Effect of the treatment on pregnancy rates was analysed by chi-square test. Meloxicam treatment on day 15 after insemination dramatically decreased pregnancy rates in the heifers (52%; 25 of 48 in the control group vs 24.3%; 9 of 37 in the meloxicam-treated group; p < 0.01). This result indicates that administration of meloxicam at the time associated with pregnancy recognition processes to maintain the CL was harmful to the pregnancy even though the drug is considered to be safe during pregnancy in cattle.