Estrogen receptor is expressed in pig embryos during preimplantation development

Nobiletin as a novel agent to enhance porcine in vitro embryo development and quality

In vitro embryo production (IVP) is of great importance to the porcine industry, as well as for basic research and biomedical applications. Despite the large efforts made in laboratories worldwide to address suboptimal culture conditions, porcine IVP remains inefficient. Nobiletin (Nob, 5,6,7,8,3',4' hexamethoxyflavone) supplementation to in vitro culture (IVC) medium, enhances in vitro embryo development in various species. However, its impact on the quality and developmental capacity of in vitro-produced pig embryos is yet to be established. This study evaluated the effects of different concentrations (2.5 and 5 μM) of Nob during the early culture of in vitro-produced pig embryos on embryo developmental competence, mitochondrial activity, lipid content, intracellular Reactive Oxygen Species (ROS) and Glutathione (GSH) content, Total Cell Number (TCN) per blastocyst, and expression of genes related to embryo development, quality and oxidative stress. Embryos cultured in medium without Nob supplementation and in medium supplemented with 0.01 % dimethyl sulfoxide (DMSO-vehicle for Nob) constituted the Control and DMSO groups, respectively. Embryo development rates were evaluated on Days 2, 6 and 7 of IVC. Additionally, a representative group of embryos was selected to assess mitochondrial activity, lipid, ROS and GSH content (on Days 2 and 6 of IVC), TCN assessment and gene expression analyses (on Day 6 of IVC). No significant differences were observed in any of the parameters evaluated on Day 2 of IVC. In contrast, embryos cultured under the presence of Nob 2.5 showed higher developmental rates on Days 6 and 7 of IVC. In addition, Day 6 embryos showed increased mitochondrial activity, with decreased levels of ROS and GSH in the Nob 2.5 group compared to the other groups. Both Nob 2.5 and Nob 5 embryos showed higher TCN compared to the Control and DMSO groups. Furthermore, Nob 2.5 and Nob 5 upregulated the expression of Superoxide dismutase type 1 (SOD1) and Glucose-6-phosphate dehydrogenase (G6PDH) genes, which could help to counteract oxidative stress during IVC. In conclusion, the addition of Nob during the first 48 h of IVC increased porcine embryo development rates and enhanced their quality, including the upregulation of relevant genes that potentially improved the overall efficiency of the IVP system.

Is the corpus uteri a suitable site for embryo transfer in the pig?

Numerous attempts to establish a practicable means of non-surgical embryo transfer in pigs were unsuccessful until instruments were developed to permit deposition of embryos deep inside a uterine horn. Recently, however, successful non-surgical transfer of embryos to the uterine body in non-sedated recipients has been reported. These reports have prompted us to present data from a study that addresses the question of whether the commonly experienced low pregnancy rates following transfers to the corpus uteri results from the inability of endometrial receptors to recognize the presence of embryos or to the prevailing unfavorable local conditions. Blastocysts were transferred to the corpus uteri of recipients in which maintenance of pregnancy was assured by the transfer of additional embryos to the tip of a uterine horn. Embryos from pigmented and unpigmented donors were used to be able to differentiate between fetuses from embryos transferred to different sites. Fewer fetuses developed from embryos transferred to the corpus uteri than from embryos transferred to the uterine horn. This leads to the conclusion that prolonged retention of blastcysts in the uterine body under conditions inappropriate for their stage of development is responsible for an unsatisfactory pregnancy rate.

Reconsidering "low-dose"-Impacts of oral estrogen exposure during preimplantation embryo development

Perturbations of estrogen signaling during developmental stages of high plasticity may lead to adverse effects later in life. Endocrine-disrupting chemicals (EDC) are compounds that interfere with the endocrine system by particularly mimicking the action of endogenous estrogens as functional agonists or antagonists. EDCs compose synthetic and naturally occurring compounds discharged into the environment, which may be taken up via skin contact, inhalation, orally due to contaminated food or water, or via the placenta during in utero development. Although estrogens are efficiently metabolized by the liver, the role of circulating glucuro- and/or sulpho-conjugated estrogen metabolites in the body has not been fully addressed to date. Particularly, the role of intracellular cleavage to free functional estrogens could explain the hitherto unknown mode of action of adverse effects of EDC at very low concentrations currently considered safe. We summarize and discuss findings on estrogenic EDC with a focus on early embryonic development to highlight the need for reconsidering low dose effects of EDC.

Oxidative stress induced by methomyl exposure reduces the quality of early embryo development in mice

Methomyl is a widely used carbamate insecticide and environmental oestrogen that has adverse effects on the reproductive system. However, there have been no reports on the effect of methomyl on early embryos in mammals. In this study, we explored the effect of methomyl exposure on the quality of early embryonic development in mice and the possible mechanisms. During in vitro culture, different concentrations of methomyl (10, 20, 30 and 35 μM) were added to mouse zygote medium. The results showed that methomyl had an adverse effect on early embryonic development. Compared with the control group, the addition of 30 μM methomyl significantly reduced the rate of early embryo blastocyst formation. Methomyl exposure can increase oxidative stress and impair mitochondrial function, which may be the cause of blastocyst formation. In addition, we found that methomyl exposure promoted apoptosis and autophagy in mouse blastocysts. The toxic effect of methomyl on early embryos may be the result of oxidative stress induction. Taken together, our results indicate that methomyl can cause embryonic development defects in mice, thereby reducing the quality of early embryo development.

Effect of Triclosan Exposure on Developmental Competence in Parthenogenetic Porcine Embryo during Preimplantation

Triclosan (TCS) is included in various healthcare products because of its antimicrobial activity; therefore, many humans are exposed to TCS daily. While detrimental effects of TCS exposure have been reported in various species and cell types, the effects of TCS exposure on early embryonic development are largely unknown. The aim of this study was to determine if TCS exerts toxic effects during early embryonic development using porcine parthenogenetic embryos in vitro. Porcine parthenogenetic embryos were cultured in in vitro culture medium with 50 or 100 µM TCS for 6 days. Developmental parameters including cleavage and blastocyst formation rates, developmental kinetics, and the number of blastomeres were assessed. To determine the toxic effects of TCS, apoptosis, oxidative stress, and mitochondrial dysfunction were assessed. TCS exposure resulted in a significant decrease in 2-cell rate and blastocyst formation rate, as well as number of blastomeres, but not in the cleavage rate. TCS also increased the number of apoptotic blastomeres and the production of reactive oxygen species. Finally, TCS treatment resulted in a diffuse distribution of mitochondria and decreased the mitochondrial membrane potential. Our results showed that TCS exposure impaired porcine early embryonic development by inducing DNA damage, oxidative stress, and mitochondrial dysfunction.

Porcine IVF embryo development and estrogen receptors are influenced by the concentration of percoll gradients during sperm selection

This study aimed to evaluate the effect of three different concentrations of discontinuous gradients of percoll (90/45, 80/40, and 70/35) in the outcome of porcine in vitro fertilization (IVF) and its influence on further embryo development and quality. Embryo viability was assessed by the expression of estrogen receptors (E₂ R) and cleaved caspase-3 (CC3). The highest percoll concentration (90/45) resulted in the lowest embryo production (24.9%) in comparison with 80/40 (37.5%) and 70/35 (40.0%), with the production being similar between the two lowest concentrations. The hatching rate for 90/45 (26.2%) was lower than for 80/40 (45.5%), and both were similar to the Group 70/35 (32.9%). The hatched embryos from the concentration 90/45 showed the lowest proportion of E₂ R expression (3.6%), while the Groups 80/40 (22.6%) and 70/35 (39.3%) had a similar proportion of expression. The live embryos that did not hatch until Day 8 of culture presented a higher CC3 proportion for Group 90/45 (18.3%), in comparison with 80/40 (12.7%) and 70/35 (10.7%), with the latter two being similar. In conclusion, adjustments in percoll concentration used for sperm selection before porcine IVF can improve embryo production and competence for pregnancy recognition and establishment.

Development of an in vitro test battery for the screening of the receptor-mediated mechanism and the spindle-poison mode of action of estrogenic compounds

The implementation of the REACH regulation has imposed the urgent need of developing alternative testing methods to screen large number of compounds more quickly and at lower costs. In this study, a battery of tests, suitable for reproductive toxicology testing, was developed with the objective of detecting the mechanism of action of estrogenic and xenoestrogenic compounds. With this aim, two compounds known for their estrogenic activity, diethylstilbestrol and 17β-estradiol, were used to set up four different in vitro tests: 1) bovine oocyte in vitro maturation assay, 2) bovine preimplantation embryo in vitro culture assay and 3) MCF-7 and 4) BALB/3T3 cell lines proliferation and cytotoxicity assay, respectively. The results show that this battery of tests allows to identify and to distinguish between two major mechanisms of action of (xeno)estrogenic compounds: the receptor-mediated mechanism and the spindle-poison effect on microtubules polimerization.

Interaction of the conceptus and endometrium to establish pregnancy in mammals: role of interleukin 1β

Implantation and the establishment of pregnancy in mammals involves an intricate interplay of hormones, cytokines, growth factors, proteins, lipids, ions and the extracellular matrix between the uterine epithelium, stroma, immune cells and the conceptus trophectoderm. The divergent nature of implantation in the mouse, human and pig provides not only an interesting contrast in the establishment of pregnancy and early embryonic development but also intriguing similarities with regard to early endometrial-conceptus signaling. An interesting pro-inflammatory cytokine expressed in a number of mammalian species during the period of implantation is interleukin-1β (IL1B). The presence of IL1B might be involved with immunotolerance at the maternal-placental interface and has been proposed as one of the mediators in placental viviparity. The production of IL1B and other proinflammatory cytokines might play a role in establishing pregnancy through modulation of the nuclear factor kappa-B (NFKB) system in a number of species. A model for the regulation of cellular progesterone receptor expression and NFKB activation for endometrial receptivity and conceptus attachment is continuing to evolve and is discussed in the present review.

Effect of resveratrol on the development of porcine embryos produced in vitro

The effects of resveratrol (a phytoalexin with a wide variety of pharmacological activities) on pig embryos produced by parthenogenesis and/or in vitro fertilization have been investigated. First, parthenogenetic embryos were generated and cultured in PZM-3 medium supplemented with various amounts of resveratrol (0, 0.05, 0.1, 0.5, 1.0 and 25 microM final concentrations). In the presence of 0.5 microM resveratrol a significantly higher percentage of parthenogenetic embryos reached the blastocyst stage by day 7 compared to non-treated control (43.5+/-6.3% vs. 33.0+/-5.4%; P<0.05). The total cell number of blastocysts also increased as a result of incubation with 0.5 microM resveratrol; the difference was statistically significant between treated and non-treated embryos on day 5 of culture (35.8+/-0.9 vs. 32.1+/-1.1; P<0.05). Resveratrol incubation affected the expression levels of apoptosis-related genes in parthenogenetic blastocysts: the level of Bax transcripts was similar but lower expression of Bcl-2 and Caspase-3 was observed in embryos treated with 0.5 microM resveratrol when compared to control blastocysts (P<0.05). The results of the TUNEL assay were similar in blastocysts developing with or without resveratrol supplementation. In addition, when embryos produced by in vitro fertilization were incubated with 0.5 microM resveratrol, the treatment led to higher frequencies of blastocyst formation (8.6% vs. 13.3%) and elevated total cell numbers (37.1+/-2.4 vs. 43.2+/-1.7) by the end of the 7-day culture period (P<0.05). The results indicate that 0.5 microM resveratrol during culture has a positive effect on early embryonic development of porcine embryos.

Temporal expression of factors involved in chromatin remodeling and in gene regulation during early bovine in vitro embryo development

Distinct epigenetic modification events regulate gene expression and chromatin structure during the period between the immature oocyte and the blastocyst. Throughout this developmental period, important methylation fluctuations occur on genomic DNA and histones. Finding single or combinations of factors, which are at work during this period is essential to understand the entire epigenetic process. With this in mind, we assessed the precise temporal expression profile, during preimplantation embryo development, of 15 key regulators involved in RNA, DNA or histone methylation, chromatin modification or silencing and transcription regulation. To achieve this, real-time RT-PCR was used to quantify the mRNA levels of ATF7IP, DMAP1, EHMT1, EHMT2, HELLS, JARID1A, JARID1B, JMJD1A, JMJD2A, LSD1, MeCP2, METTL3, PRMT2, PRMT5 and RCOR2, in the oocyte and throughout in vitro bovine embryo development. Our results demonstrate that all the 15 key regulators were present to different degrees in the developmental stages tested, and they can be divided into three different groups depending on their respective mRNA profile.

Expression analysis of the steroidogenic acute regulatory protein (STAR) gene in developing porcine conceptuses

Steroidogenesis in porcine non-conceptus tissue is regulated by the STAR-dependent transport of cholesterol from the outer to inner mitochondrial membrane. Previous serial analysis of gene expression (SAGE) identified a STAR mRNA transcript in the porcine peri-implantation conceptus during trophectoderm elongation and increased conceptus estrogen synthesis between gestational day 11 and 12. To assess a potential role for STAR in the modulation of conceptus steroidogenesis via cholesterol transport, the conceptus STAR transcript was PCR cloned and temporal expression of mRNA and protein were examined. Northern analysis of day 12 corpora lutea and pig conceptus RNA detected multiple STAR transcripts in both tissues and identified the cloned transcript as the longest variant. The transcript had a 99% similarity to a truncated ovarian STAR transcript. The conceptus STAR transcript was temporally regulated during elongation but trace expression was present in day 6 blastocysts and day 25 conceptuses. Differential regulation of STAR mRNA was concomitant with the presence of the stimulatory transcription factor steroidogenic factor 1, and absence of the inhibitory transcription factor dosage-sensitive sex reversal, adrenal hypoplasia congenita, critical region on the X chromosome, gene-1, transcripts. In contrast to peak STAR mRNA expression at the filamentous stage, Western blot analyses revealed STAR protein levels were highest in tubular conceptuses. These data confirm the presence of STAR mRNA and protein during porcine conceptus elongation and suggest regulation of STAR at two levels, transcriptionally, in part, through differential regulation of transcription factors, and post-transcriptionally, evidenced by the disparity of protein to RNA in filamentous conceptuses.

Differentiation of murine embryonic stem cells induces progesterone receptor gene expression

The role of steroid hormone receptors in very early embryonic development remains unknown. Clearly, expression during organogenesis is important for tissue-specific development. However, progesterone receptor (PR) and estrogen receptors (ERalpha, ERbeta) are expressed during early development through the blastocyst stage in mice and other species, and yet are not essential for embryonic viability. We have utilized the mouse embryonic stem (mES) cell model to investigate the regulated expression of these receptors during differentiation. Surprisingly, one of the earliest changes in gene expression in response to a differentiation signal observed is PR gene induction. It parallels the time course of expression for the patterning genes Hoxb1 and Hoxa5. Unexpectedly, PR gene expression is not regulated in an estrogen-dependent manner by endogenous ERs or by transiently overexpressed ERalpha. Our results suggest a potentially novel mechanism of PR gene regulation within mES cells compared to adult tissues and the possibility of unique targets of PR action during early mES cell differentiation.

Effects of oxygen concentration and antioxidants on the in vitro developmental ability, production of reactive oxygen species (ROS), and DNA fragmentation in porcine embryos

After in vitro maturation and fertilization of porcine oocytes, the fertilized embryos were cultured under 5 or 20% oxygen (O2) for 7 days. In embryos cultured under 5% O2 versus 20% O2, development to the blastocyst stage was higher (36.3% versus 22.5%, P < 0.05); the hydrogen peroxide (H2O2) content as a reactive oxygen species was lower (92 pixels versus 111 pixels, P < 0.05); and fragmentation of DNA in 8- to 16-cell stage embryos (estimated by the comet assay) resulted in a shorter (P < 0.05) DNA tail (36 microm versus 141 microm). Antioxidants such as beta-mercaptoethanol (beta-ME) and Vitamin-E (Vit-E) suppressed oxidative damage in the embryos and improved their developmental ability. For embryos cultured under 20% O2, there were the following differences (P < 0.05) between embryos exposed to 0 microM versus 50 microM beta-ME: 28% versus 57% developed to the blastocyst stage; 125 pixels versus 98 pixels per embryo in H2O2 content; and a DNA tail of 209 microm versus 105 microm. In addition, for embryos cultured under 20% O2, there were also differences (P < 0.05) between those exposed to 0 microM versus 50 microM of Vit-E: 28% versus 40% rate of development to the blastocyst stage; 28.9 cells versus 35.9 cells in the expanded blastocyst; 122 pixels versus 95 pixels per embryo (H2O2 content); and 215 microm versus 97 microm length of the DNA tail. Therefore, a low O2 concentration during in vitro culture of porcine embryos decreased the H2O2 content and, as a consequence, reduced DNA fragmentation, and, thereby, improved developmental ability.

Expression patterns of three estrogen receptor genes during zebrafish (Danio rerio) development: evidence for high expression in neuromasts

The estrogen receptor (ER) genes encode a group of nuclear enhancer proteins, which are important ligand-activated transcription factors, modulating estrogen-target gene transcription. In this study we analyzed expression patterns of three zebrafish ER genes, esr1, esr2a, and esr2b, during development using whole-mount in situ hybridization. High levels of esr2a and esr2b of maternal origin are inherited and segregated to the blastomers. After the mid-blastula transition, the three genes exhibit similar spatio-temporal patterns of expression. In 24 h postfertilization (hpf) embryos, high levels of esr2a and esr2b and low levels of esr1 mRNAs are detected in the epidermis, pectoral fin buds, hatching gland and, to a lesser extent, developing brain. From 24 hpf onward, the expression of the three genes is down-regulated in the epidermis. By 60 hpf, esr2a mRNA is abundant in mature primary neuromasts of the anterior line system and by 3 days postfertilization (dpf), all mature primary neuromasts in both the anterior and posterior lateral line systems express significant levels of esr2a and esr2b transcripts. Histological sections show a high level of esr2a transcripts in both mechanoreceptive hair cells and supporting cells. The transcripts are still detected after neomycin-induced hair cell death, consistent with the presence of esr2a transcripts in supporting cells. From 6 dpf onward, esr2a and esr2b transcripts are robustly co-expressed in primary neuromasts, branchial arches, pectoral fins, and anal papilla, while slight labeling is observed for esr1 transcripts.

Oestradiol, cyclodextrin-encapsulated 17beta-oestradiol and the oestradiol solubilizer 2-hydroxypropyl-beta-cyclodextrin all impair preimplantation mouse embryo development

The aim of this study was to examine the effects of 2-hydroxypropyl-beta-cyclodextrin (HbetaC) used as a solubilizer for oestradiol, 17beta-oestradiol (ethanol soluble) and HbetaC-encapsulated-17beta-oestradiol on mouse embryo development in vitro. HbetaC had no effect on day 3 development. In contrast, blastocyst development and blastocyst cell number were significantly reduced in the presence of 10(-4) mol/l solubilizer equivalent, but not at lower concentrations. The proportion of compacted embryos was significantly reduced with 10(-4) mol/l 17beta-oestradiol. No blastocysts were formed at 10(-4) mol/l concentration of 17beta-oestradiol, although the rate of blastocyst formation did not differ at lower concentrations. Blastocyst cell number was significantly decreased compared with controls at 10(-5) mol/l 17beta-oestradiol. The dose-response using HbetaC-encapsulated-17beta-oestradiol revealed that at 17beta-oestradiol concentrations of 10(-4) and 10(-5) mol/l, blastocyst development was significantly reduced. Blastocyst cell number was significantly reduced compared with controls for all concentrations of HbetaC-encapsulated-17beta-oestradiol. Exposure of embryos to 17beta-oestradiol (10(-4) mol/l) reduced blastocyst development on days 4 and 5 significantly in cultures initiated at the zygote, 2-cell and 8-cell, but not the morulae, stages of development. Trophectoderm, ICM and blastocyst cell numbers as well as percentage ICM development were reduced significantly, regardless of the stage of development. Therefore, 17beta-oestradiol does compromise embryo development.

Expression of Nucleolar-Related Proteins in Porcine Preimplantation Embryos Produced In Vivo and In Vitro1

The expression of nucleolar-related proteins was studied as an indirect marker of the ribosomal RNA (rRNA) gene activation in porcine embryos up to the blastocyst stage produced in vivo and in vitro. A group of the in vivo-developed embryos were cultured with alpha-amanitin to block the de novo embryonic mRNA transcription. Localization of proteins involved in the rRNA transcription (upstream binding factor [UBF], topoisomerase I, RNA polymerase I [RNA Pol I], and the RNA Pol I-associated factor PAF53) and processing (fibrillarin, nucleophosmin, and nucleolin) was assessed by immunocytochemistry and confocal laser-scanning microscopy, and mRNA expression was determined by semiquantitative reverse transcription-polymerase chain reaction (RT-PCR). These findings were correlated with ultrastructural data and autoradiography following 20-min [3H]uridine incubation. Additionally, expression of the pocket proteins pRb and p130, which are involved in cell-cycle regulation, was assessed by semiquantitative RT-PCR up to the blastocyst stage. Toward the end of third cell cycle, the nuclei in non-alpha-amanitin-treated, in vivo-produced embryos displayed different stages of transformation of the nuclear precursor bodies (NPBs) into fibrillogranular nucleoli associated with autoradiographic labeling. However, on culture with alpha-amanitin, NPBs were not transformed into a fibrillogranular nucleolus during this cell cycle, demonstrating that embryonic nucleogenesis requires de novo mRNA transcription. Moreover, immunolocalization of RNA Pol I, but not of UBF, and the mRNA expression of PAF53 and UBF were significantly reduced or absent after culture with alpha-amanitin, indicating that RNA Pol I, PAF53, and presumably, UBF are derived from de novo embryonic transcription. Embryonic genomic activation was delayed in porcine embryos produced in vitro compared to the in vivo-derived counterparts with respect to mRNAs encoding PAF53 and UBF. Moreover, differences existed in the mRNA expression patterns of pRb between in vivo- and in vitro-developed embryos. These findings show, to our knowledge for the first time, a nucleolus-related gene expression in the preimplantation porcine embryo, and they highlight the differences in quality between in vivo and in vitro-produced embryos.

Advances in biotechnology: new tools in future pig production for agriculture and biomedicine

Biotechnology in livestock comprises an arsenal of reproductive biotechniques and molecular genetics. While molecular genetics are poorly developed in swine, reproductive techniques are more advanced and applied under field conditions. This review describes three selected examples of our own research to illustrate the implication of biotechnology in future pig reproduction. Sperm sexing technology is now available and can be used to generate piglets of the desired sex by IVF and ICSI. First studies also indicate satisfactory success rates following intrauterine insemination with sexed spermatozoa. Cloning technique and production of transgenic pigs require information about the regulation and time course of gene expression during in vitro production and pre-implantation development. Information on gene expression is scare in porcine embryos. With the exception of transcripts for the oestrogen receptor gene, no mRNA's from the activated porcine genome have been identified. Recent development of cDNA arrays might help to identify a larger amount of genes in single embryos. Remarkable progress has been made in organ transplantation technology. As the demand for human organs is increasing rapidly, the pig might serve as donor of xenotranplants, provided the transmission of zoonoses from the donor animal to the human recipient is prevented, donor organ anatomy and function are compatible, and immunological rejections (HAR, VAR MAC) can be overcome. The most promising strategy is the synthesis of human complement regulatory proteins in the pig. Transgenic pigs have been generated for hDAF or hCD 46 and their hearts have been transplanted into non human primates for up to 90 days. HCD 59 driven by CMV promotor provides significant protection against HAR at least under in vitro and in vivo conditions. Current studies indicate a temporary use in patients within the next 3-5 years. As the microinjection technology to produce transgenic offspring is time consuming and very expensive, nuclear transfer technology provides a possibility for multiplication without going through the germ line with recombination effects. A functional nuclear transfer system will be crucial for xenotransplantation as it is anticipated that the expression of several transgenes will be required.

Chromosomal location, structure, and temporal expression of the platelet-activating factor receptor (PAFr) gene in porcine endometrium and embryos relative to estrogen receptor alpha gene expression

Although platelet-activating factor receptor (PAFr) gene was well characterized in the human, little was known about it in domestic animals. Porcine PAFr gene was mapped using fluorescence in situ hybridization (FISH). The structure of this gene was investigated using a 5' rapid amplification of cDNA ends (RACE) technique. Temporal expression of PAFr and estrogen receptor alpha genes (ER), and distribution of the PAFr transcripts in porcine endometrial and embryonic tissues on days 0, 10, 12, 14, 16, and 18 were analyzed using DNA competitors and reverse transcription and polymerase chain reaction (RT-PCR). The porcine PAFr gene was mapped to SSC6q26-27. Alternative splicing of primary transcripts of the PAFr gene produced two different transcripts. Transcript 1 was expressed in all tissues and cells, and transcript 2 was detected in all tissues but white blood cells. The temporal expression of the PAFr gene in endometrial (P > 0.05) and embryonic (P < 0.05) tissues of pregnant sows increased from day 10 to 16. The temporal expression of ER genes in endometrial tissues of pregnant sows decreased from day 10 to 18 (P < 0.05). In addition, ER expression was detectable in 20-60% of embryonic tissue samples, which generally decreased. In combination with previously obtained data on PAF and estradiol-17beta (E(2)) concentrations in pregnant uterine luminal fluids (pULF), endometrial and embryonic tissues, the present results indicated that the increasing PAFr transcripts were positively associated with increasing levels of PAF. Both ER transcripts and E(2) found in pULF decreased correspondingly from day 13 to 16. These results indicate that via PAFr, PAF could play a dominant role in peri-implantation development in pigs as compared to E(2).

Effects of bovine serum albumin and estrous cow serum on development and ultrastructure of in vitro-produced porcine embryos

This study evaluated the effects of bovine serum albumin (BSA; 4 mg/ml) and estrous cow serum (ECS; 10%) in North Carolina State University (NCSU) 23 medium on the development of in vitro-matured and in vitro-fertilized porcine oocytes. Early cleavage rate was significantly (P < 0.05) higher in NCSU/ECS (71.3 +/- 14.7%) vs. NCSU/BSA (60.6 +/- 4.7%). Cleavage beyond the four-cell stage was not different between the two culture media (43.5 +/- 9.5% and 41.4 +/- 17.7%, respectively). The proportion of development to blastocysts was--with borderline significance (P = 0.05)--higher in NCSU/BSA (28.0 +/- 4.4%) than in NCSU/ECS (20.4 +/- 7.3%). Blastocysts produced in NCSU/BSA had significantly (P < 0.001) higher cell numbers than those cultured in NCSU/ECS (29.5 +/- 20.1 vs. 16.9 +/- 10.8). The ultrastructure of in vitro-produced blastocysts from both culture systems was compared vs. in vivo-derived blastocysts. The latter showed a clear differentiation between trophectoderm (TE) and inner cell mass (ICM) cells. The TE cells were anchored to other TE cells or ICM cells by long, well-developed junctional complexes. The apical membrane of trophoblast cells was covered with numerous microvilli. Mitochondria were abundant, round to elongated in shape, and showed clear transverse cristae. The ultrastructure of blastocysts cultured in NCSU/BSA mimicked that of in vivo-derived embryos closely. In contrast, blastocysts from the NCSU/ECS culture system displayed an irregular ultrastructure with reduced numbers of organelles and numerous cytoplasmic inclusions, such as lipid-yolk-vacuoles and vacuoles with lipid content. In some sections of these embryos, cellular debris was detected in cytoplasm. The shape of mitochondria was more ovoid and cristae were not visible. In summary, our results demonstrate a beneficial influence of ECS in the culture medium on initial cleavage of in vitro-produced porcine embryos. Clearly negative effects of ECS in the subsequent culture period are associated with marked ultrastructural changes of embryonic cells.

Androgen receptor and follicle-stimulating hormone receptor in the pig ovary during the follicular phase of the estrous cycle

Follicle-stimulating hormone (FSH) is an important regulator of follicular development. Some effects of FSH on ovarian follicles might be enhanced by androgens. The main objectives of the present study were to examine expression of the androgen receptor (AR) and FSH receptor (FSHR) in late developing follicles in pigs. Ovaries were collected from gilts on days 13, 15, 17, and 19 of the estrous cycle (day 0 = first day of estrus, n = 4 gilts/day), a period coincident with the follicular phase. One ovary was processed for immunohistochemistry (IHC) of AR. Samples of surface wall from the largest follicles (4-5 per gilt) were dissected from the other ovary, pooled and processed for determination of AR and FSHR mRNAs using reverse transcription-polymerase chain reaction (RT-PCR). Intense AR immunostaining was present in nuclei of granulosa cells of preantral and antral follicles. AR immunoreactivity was also present in the nuclei of oocytes. Weak staining for AR was observed in cells of the theca interna, ovarian surface epithelium, and in most cells of the ovarian stroma. Relative amounts of immunoreactive AR in granulosa cells of late developing follicles, or small antral follicles (< 2 mm), did not differ between days 13, 15, 17, and 19. However, amounts of AR in granulosa cells of small antral follicles was greater (P < 0.05) than in the largest follicles present in the same ovary. The relative amounts of AR mRNA in tissue from the largest follicles on days 13, 15, 17, and 19 did not differ; however, amounts of FSHR mRNA in the same follicles were not different between days 13, 15, and 17, but decreased (P < 0.05) by day 19. Results indicate that during the follicular phase in gilts, the AR protein is mainly present in granulosa cells. Relative amounts of AR protein in granulosa cells and mRNA in walls of late developing follicles did not significantly change from day 13 to 19; however, amounts of FSHR mRNA decreased in preovulatory follicles by day 19 of the estrous cycle.

Molecular cloning of porcine estrogen receptor-beta complementary DNAs and developmental expression in periimplantation embryos

In the pig, estrogens transiently produced by embryos and progestins of maternal origin target the uterine endometrium, causing alterations in gene expression and secretory activity, both of which are important for the initiation of embryo attachment. The potential direct embryotrophic roles of estrogens and progestins are, however, unknown. Here we report the cloning of porcine embryonic estrogen receptor-beta (ER-beta) mRNA by reverse transcription-polymerase chain reaction (RT-PCR) using specific primer sets designed initially within conserved regions of human and bovine ER-beta mRNAs, and subsequently within regions of identified porcine ER-beta cDNA sequences. The ER-beta mRNA has an open reading frame of 1578 nucleotides and encodes a 526 amino acid polypeptide that displays greater than 90% identity with other mammalian ER-beta proteins. Northern and Western blot analyses using porcine filamentous embryos from Day 12 of pregnancy demonstrated the presence of multiple ER-beta mRNA transcripts of approximately 9.5, 4.9, and 3.5 kilobases, and a similar 64-kDa protein corresponding in size to human ovarian granulosa cell ER-beta, respectively. In Day 12 filamentous embryos, ER-beta expression was immunolocalized to trophoblastic cell nuclei, coincident with that of proliferative cell nuclear antigen (PCNA). The developmental ontogeny of ER-beta mRNA was evaluated in embryos of different morphologies (spherical, tubular, and filamentous) by semiquantitative RT-PCR, along with those for other steroid hormone receptors (ER-alpha and progesterone receptor) and known embryonic genes associated with cell differentiation (cytochrome P450 aromatase type III) and growth (cyclin D1). ER-beta mRNA levels varied with embryo morphology (filamentous maximum at Day 12), coincident with that of cyclin D1. Progesterone receptor mRNA levels were maximal in tubular embryos, similar to that of P450 aromatase, whereas the expression of the ER-alpha gene was barely detectable and appeared constitutive for all developmental stages examined. Estradiol-17 beta treatment of Day 12 filamentous embryos in culture up-regulated ER-beta and P450 aromatase (type III) mRNA levels, respectively, but decreased those of PCNA, and had no effect on cyclin D1 mRNA levels. These studies taken together suggest that embryonic ER-beta likely mediates the autocrine functions of estrogens in the dynamic regulation of embryonic growth and development at periimplantation.