Pregnancy-associated bovine and ovine glycoproteins exhibit spatially and temporally distinct expression patterns during pregnancy

Comparison of five radioimmunoassay systems for PAG measurement: ability to detect early pregnancy in cows

This study was conducted to describe the minimum detection limit, reproducibility, accuracy, specificity and parallelism of different pregnancy-associated glycoprotein radioimmunoassay (PAG-RIA) systems: RIA-497, RIA-706, RIA-780, RIA-809 and RIA-Pool. Their ability to distinguish between non-pregnant and pregnant females at day 30 after artificial insemination (AI) was investigated. The antisera were raised in rabbits against different PAG preparations. All RIA systems proved to be sensitive, repeatable and accurate for measuring PAG concentrations. The dilutions of plasma samples taken at an early stage of pregnancy were found to be parallel to the standard curves. No cross-reaction was observed with different carbohydrates, either with Pregnant Mare Serum Gonadotropin (PMSG) or human Chorionic Gonadotropin (hCG). The concentrations of PAG in pregnant females at day 30 after AI were shown to be higher with the use of antisera R#706, R#780, R#809 and Pool when compared with antiserum R#497. All the RIA systems gave 100% sensitivity and negative predictive values. On the other hand, the use of antisera R#780 and R#809 resulted in lower specificity and positive predictive values. The present study clearly shows that the ability of PAG-RIA systems to diagnose pregnancy specifically at day 30 after AI can be improved by using a combination of antisera raised against different forms of PAG.

Produção de progesterona in vitro pelas células do corpo lúteo bovino ao longo da gestação

O presente trabalho foi desenvolvido para testar a hipótese de que células luteínicas bovinas em cultivo, provenientes dos três terços de gestação, comportam-se da mesma maneira que células in vivo em relação à produção de P4. Foram coletadas amostras de corpos lúteos (CL) de 90 (n=3), 150 (n=3) e 210 (n=3) dias de gestação obtidos em abatedouro. Sob condições assépticas, as células foram mecanicamente dispersas e cultivadas em placas de 96 poços. Após 24 horas de cultivo foram feitas a lavagem dos poços e a adição do precursor pregnenolona. Os tratamentos foram realizados em octuplicata para cada tempo de tratamento (24, 48 e 96 horas) com três repetições de cada período gestacional. As amostras de meio de cultura e as células foram coletadas 24, 48 e 96 horas após adição do precursor e acondicionadas em freezer a -20ºC até o processamento. A progesterona foi dosada através de radioimunoensaio e o conteúdo protéico pelo método de Lowry. Os resultados foram analisados estatisticamente e considerados diferentes quando p<0.05. Foi observada maior produção de P4 aos 90 dias de gestação (35,277±0,075), posterior decréscimo aos 150 dias (28,820±0,231) e novo aumento aos 210 dias (32,777±0,099). A produção de P4 em células cultivadas por 24 horas foi maior (p<0,05) em células oriundas do grupo de 90 dias (2,912±0,047) quando comparado a 150 (2,669±0,137) e 210 dias (2,741±0,088). As 48 e 96 horas de cultivo, células luteínicas bovinas de 90 dias produziram mais P4 que células de 210 dias (2,934±0,029 e 2,976±0,121 respectivamente x 2,760±0,059 e 2,695±0,149, respectivamente; p<0,05), que por sua vez produziram mais do que células de 150 dias (2,334±0,084 para 48 horas e 2,205±0,136 para 96 horas). Aos 150 dias de gestação a produção de progesterona apresentou diminuição gradativa ao longo das 96 horas de cultivo. Essas diferenças podem ser explicadas pela expressão gênica diferencial de enzimas ou também de fatores presentes na cascata esteroidogênica de acordo com a idade gestacional. Este modelo de cultura celular luteínica poderá ser utilizado em estudos funcionais uma vez que o padrão de secreção de P4 mimetizou o que ocorre in vivo.

Influence of progesterone concentrations on secretory functions of trophoblast and pituitary during the first trimester of pregnancy in dairy cattle

The essential role played by progesterone in the maintenance of pregnancy is unequivocal; however, the effects of progesterone on the secretory patterns of placental and pituitary molecules during the gestation period are not well defined. The objective of this study was to describe pregnancy-associated glycoprotein (PAG) concentrations (measured by RIA-497 and RIA-Pool) in pregnant females with progesterone concentrations lower (low-P4 group, n=20) or higher (high-P4 group, n=17) than the mean of 8.74 ng/mL on Day 21 (AI=Day 0). Luteinizing hormone (LH) and prolactin concentrations were also measured in both groups. Throughout the study period, blood samples were collected on Days 0, 21, 45, 60, and 80 from 37 females that were confirmed to be pregnant. PAG concentrations measured by both RIA-497 and RIA-Pool tended to be higher in high-P4 group than in low-P4 group from Day 30 until Day 80. On Day 80, plasma PAG concentrations that were measured using RIA-497 were observed to be higher (P<0.05) in the high-P4 group than in the low-P4 group (10.2+/-8.7 ng/mL versus 6.9+/-3.8 ng/mL). Concentrations of LH on Day 60 and prolactin on Day 80 were observed to be significantly lower (P<0.05) in the high-P4 group. There was a tendency for the concentrations of LH (Days 45 and 80) and prolactin (Days 30, 45, and 60) to be lower in cows in the high-P4 group than in the low-P4 group. Our results suggest the existence of a relationship among the concentration levels of progesterone, PAG, LH, and prolactin during early pregnancy.

Measurement of Ovine Pregnancy-Associated Glycoprotein (PAG) During Early Pregnancy in Lacaune Sheep

This study describes ovine pregnancy-associated glycoprotein (ovPAG) concentrations in 20 Lacaune sheep during early pregnancy. Measurements were performed by using semi-purified ovPAG as standard, tracer and immunogens for antibody production in rabbits. Antisera R780 (against ovPAG(57+59kDa)) and R805 (against ovPAG5(58+61kDa)) were used respectively in RIA-780 and RIA-805. Blood samples were collected at days 0, 18, 20, 22 and 25 after artificial insemination. From day 18 after breeding onward, the mean ovPAG concentration was significantly higher (p < 0.001) in plasma samples from pregnant ewes (n = 17) than in non-pregnant ones (n = 3). The specific activity of the tracer was 11 760 Ci/mmol in RIA-780 and 14 900 Ci/mmol in RIA-805. The minimal detection limits for RIA-780 and RIA-805 were 0.2 ng/ml and 0.3 ng/ml, respectively. The intra-assay CV of samples with low (1.0 ng/ml), medium (2.5 ng/ml) and high (4.0 ng/ml) PAG concentrations were 3%, 6% and 9% for RIA-780 and 8%, 9% and 5% for RIA-805. The inter-assay CV in the same samples were 13%, 12% and 7% for RIA-780 and 13%, 11% and 5% for RIA-805. The recovery was higher than 95% in both assays. No cross-reaction was observed with members of aspartic proteinase family as well as with other tested proteins. In both RIA-780 and RIA-805, inhibition of the binding of the tracer by antisera was parallel between standard curve and serial dilutions of pregnant ewe samples. In conclusion, the two homologous RIA systems are suitable for early quantification of ovPAG concentrations in ewe plasma samples from day 18 after breeding.

Global gene expression analysis and regulation of the principal genes expressed in bovine placenta in relation to the transcription factor AP-2 family

BACKGROUND

Cell-cell communication is an important factor in feto-maternal units during placentogenesis. The placenta produces pivotal hormones and cytokines for communication between cotyledonary villi and the maternal caruncle. Gene expression in bovine placenta throughout pregnancy was comprehensively screened by a cDNA microarray, and we searched for a common transcription factor in a gene cluster that showed increasing expression throughout gestation in cotyledonary villi and caruncle.

METHODS

Placentomal tissues (villi and caruncle) were collected from Day 25 to Day 250 of gestation for microarray analysis. Global gene expression profiles were analyzed using the k-means clustering method. A consensus sequence cis-element that may control up-regulated genes in a characteristic cluster was examined in silico. The quantitative expression and localization of a specific transcription factor were investigated in each tissue using quantitative real-time RT-PCR and in situ hybridization.

RESULTS

The microarray expression profiles were classified into ten clusters. The genes with most markedly increased expression became concentrated in cluster 2 as gestation proceeded. Cluster 2 included placental lactogen (CSH1), pregnancy-associated glycoprotein-1 (PAG1), and sulfotransferase family 1E estrogen-preferring member 1 (SULT1E1), which were mainly detected in giant trophoblast binucleate cells (BNC). Consensus sequence analysis identified transcription factor AP-2 binding sites in some genes in this cluster. Quantitative real-time RT-PCR analysis confirmed that high level expression of transcription factor AP-2 alpha (TFAP2A) was common to cluster 2 genes during gestation. In contrast, the expression level of another AP-2 family gene, transcription factor AP-2 beta (TFAP2B), was extremely low over the same period. Another gene of the family, transcription factor AP-2 gamma (TFAP2C), was expressed at medium level compared with TFAP2A and TFAP2B. In situ hybridization showed that TFAP2A, TFAP2B and TFAP2C mRNAs were localized in trophoblast cells but were expressed by different cells. TFAP2A was expressed in cotyledonary epithelial cells including BNC, TFAP2B was specifically expressed in BNC, and TFAP2C in mononucleate cells.

CONCLUSION

We detected gestational-stage-specific gene expression profiles in bovine placentomes using a combination of microarray and in silico analysis. In silico analysis indicated that the AP-2 family may be a consensus regulator for the gene cluster that characteristically appears in bovine placenta as gestation progresses. In particular, TFAP2A and TFAP2B may be involved in regulating binucleate cell-specific genes such as CSH1, some PAG or SULT1E1. These results suggest that the AP-2 family is a specific transcription factor for clusters of crucial placental genes. This is the first evidence that TFAP2A may regulate the differentiation and specific functions of BNC in bovine placenta.

Plasma concentrations of pregnancy-associated glycoprotein-1 (PAG-1) in high producing dairy cows suffering early fetal loss during the warm season

The present study was designed to establish whether plasma pregnancy-associated glycoprotein-1 (PAG-1) measurements during the early fetal period can be associated with early fetal loss. Blood samples were obtained and ultrasound controls performed on days 35, 42, 49, 56, and 63 of gestation or until pregnancy loss from 98 lactating dairy cows. Radioimmunoassay systems were used to determine PAG-1 and progesterone concentrations. Of the 98 pregnancies investigated 18 (18.4%) suffered early fetal loss: 15 (18.5%) in cows carrying singletons, and 3 (16.7%) in twin pregnancies. In cows suffering pregnancy loss, all living embryos registered on day 35 seemed normal in size and development in all weekly ultrasound controls before fetal expulsion. Using analysis of variance, plasma PAG-1 and progesterone values were not different between no loss and fetal loss groups for every gestation period. Based on the odds ratio, and considering only PAG-1 values obtained on day 35 of gestation, the risk of fetal loss was 10 and 6.8 times more likely in cows with low (<2.5 ng/ml) and high (>4 ng/ml) PAG-1 values, respectively, than in cows with medium PAG-1 values, used as reference. Of the 10 inseminating bulls included in the study, one was related to increased fetal loss by odds ratio of 21.7, whereas one bull was attributed fetal loss rate reduced by odds ratio of 12.5 (1/0.08) These findings can have a clear clinical application: PAG-1 measurements from one single sample taken on day 35 of gestation provided more useful information than a series of values obtained from day 35 to 63 of gestation, and can be indicators of subsequent fetal loss.

Gene expression profiles of novel caprine placental prolactin-related proteins similar to bovine placental prolactin-related proteins

Background

This study reports the identification of a full-length cDNA sequence for two novel caprine prolactin-related proteins (cPRP1 and cPRP6), and their localization and quantitative expression in the placenta. Caprine PRPs are compared with known bovine PRPs. We examined their evolution and role in the ruminant placenta.

Results

Full-length cPRP1 and cPRP6 cDNA were cloned with a 717- and 720- nucleotide open-reading frame corresponding to proteins of 238 and 239 amino acids. The cPRP1 predicted amino acid sequence shares a 72% homology with bovine PRP1 (bPRP1). The cPRP6 predicted amino acid sequence shares a 74% homology with bovine PRP6 (bPRP6). The two cPRPs as well as bPRPs were detected only in the placentome by RT-PCR. Analysis by in situ hybridization revealed the presence of both cPRPs mRNA in the trophoblast binucleate cells. These mRNA were quantified by real-time RT-PCR analysis of the placentome at 30, 50, 90 and 140 days of pregnancy. Both new cPRP genes were able to translate a mature protein in a mammalian cell-expression system. Western blotting established the molecular sizes of 33 kDa for cPRP1 with FLAG-tag and 45 kDa for cPRP6 with FLAG-tag. The sequence properties and localized expression of cPRP1 and cPRP6 were similar to those of bovine. However, their expression profiles differed from those in bovine placenta. Although this study demonstrated possible roles of PRPs in caprine placenta, PRPs may regulate binucleate-cell functions like those in bovine, but their crucial roles are still unclear.

Conclusion

We have identified the novel PRPs in caprine placenta. Localization and quantitative expression of caprine PRPs were compared with bovine PRPs. The data indicate that PRP genes in caprine placenta have coordination functions for gestation, as they do in bovine. This is the first study of PRPs function in caprine placenta.

Gene expression and maintenance of pregnancy in bovine: roles of trophoblastic binucleate cell-specific molecules

Cell to cell interaction plays a pivotal role in the regulation of placentogenesis and exchange of stage-specific developmental signals between the fetal and maternal units. Specifically, these interactions are paramount for programmed fetal growth, maternal adaptation to pregnancy and coordination of parturition. However, little is known about the precise regulation of placentation and maintenance of gestation in cattle. Therefore, the aim of the present study was to decipher the complex networks of cell communication to gain an insight into the multifaceted developmental process and understand the profound consequences of flawed communication. In the ruminant, the binucleate cell plays a central role in forming the structures and secretions at the fetomaternal interface that are crucial in establishing and maintaining pregnancy. Herein, we summarise differences in the abundance of specific RNA transcripts in the bovine cotyledon and caruncle using global gene expression profiling and further investigate the relationship of mRNA abundance for selected pregnancy-specific genes of interest (identified from microarray studies) that are localised exclusively to the binucleate cell, such as placental lactogen, prolactin-related proteins and pregnancy-associated glycoproteins. The results suggest that a well-orchestrated transcriptional command from binucleate cells is pivotal to the establishment and progression of pregnancy in cattle.

Milk production correlates negatively with plasma levels of pregnancy-associated glycoprotein (PAG) during the early fetal period in high producing dairy cows with live fetuses

This study was designed to establish possible factors affecting plasma pregnancy-associated glycoprotein (PAG) concentrations during early pregnancy in high producing dairy cows with live fetuses. Blood samples were obtained on days 35, 42, 49, 56 and 63 of gestation from 80 lactating cows in two herds carrying live fetuses. Radioimmunoassay systems were used to determine PAG (RIA-497 and RIA-706) and progesterone concentrations. We evaluated the effects on PAG concentrations of herd, lactation number, sire of fetus, day of gestation, fetus number, plasma progesterone and milk production at each time point established, along with possible paired interactions. Mean milk production per cow approached 41kg during the study period. PAG concentrations were not affected by herd, lactation number or plasma progesterone concentration. Significant positive effects on PAG concentrations were shown by the gestation day, and the interaction between day of gestation and twin pregnancy. Significant differences between bulls and a significant negative correlation between milk production and PAG values on day 63 of pregnancy were also detected. Proportions of blood samples showing undetectable PAG levels and false negative diagnoses throughout the study period were significantly higher (P<0.001) using the RIA-497 system (2.5% and 5.3%, respectively) compared to RIA-706 (0% and 0.8%, respectively). Our findings suggest that PAG concentrations during the early fetal period are related to the day of gestation, milk production, number of fetuses and sire of fetus in high producing dairy cows. Under our working conditions, the RIA-706 method was better at detecting plasma PAG molecules than the RIA-497 system.

The glycosylation of pregnancy-associated glycoproteins and prolactin-related protein-I in bovine binucleate trophoblast giant cells changes before parturition

Binucleate trophoblast giant cells (BNC) in the bovine placenta produce glycoproteins, which are delivered into the mother after fusion of BNC with uterine epithelial cells. During most time of pregnancy, BNC produce pregnancy-associated glycoproteins (PAGs) and prolactin-related protein-I (PRP-I) with asparagine-linked lactosamine-type glycans terminating withN-acetyl-galactosamine. We show by lectin histochemistry that terminalN-acetyl-galactosamine (detected byDolichos biflorusagglutinin, DBA) in placentomal BNC is greatly reduced prior to parturition, while lactosamine-typeN-glycans (detected byPhaseolus vulgarisleucoagglutinin, PHA-L) remain unaltered. The change in DBA-staining showed no statistically significant differences between placentomes of cows with and without retention of fetal membranes. Western blots revealed that, at parturition the apparent molecular mass of PAGs and PRP-I is 1–2 kDa lower than in late pregnancy. These changes are due to alterations of asparagine-linked glycans, since the molecular weight of the peptide backbones after enzymatical release of asparagine-linked glycans is identical at late pregnancy and parturition. Lectin western blots showed a reduction of terminalN-acetyl-galactosamine on PAGs at parturition. A lectin sandwich-ELISAwas used to differentiate DBA- and PHA-L-binding PAGs in sera of pregnant and non-pregnant cows. The values for DBA-binding PAGs at parturition were not significantly different from non-pregnancy, while the values for PHA-L-binding PAGs were significantly higher at parturition. The peripartal changes of PAG- and PRP-I-glycosylation could alter functional properties of these proteins and might therefore be considered for functional studies. The differentiation of PAG glycoforms in maternal serum could be valuable for a further optimization of PAG-based pregnancy diagnosis in cattle.

Increased vascular endothelial growth factor and pregnancy-associated glycoproteins, but not insulin-like growth factor-I, in maternal blood of cows gestating twin fetuses1,2

Differences in placental mass and vascularity exist between cows gestating single vs. multiple fetuses. Therefore, the association between fetal number and placental development or function was assessed by comparing concentrations of vascular endothelial growth factor (VEGF), pregnancy-associated glycoproteins (PAG), IGF-I, and progesterone in the maternal blood of cattle selected for twin births and gestating 1 (n = 23) vs. 2 (n = 17) fetuses. Samples of jugular venous blood were collected serially at a mean of 57, 121, 192, and 234 d (range within groups was 20 d) after AI. Plasma concentrations of VEGF, IGF-I, and progesterone were measured by double-antibody RIA, and of PAG by an indirect sandwich ELISA. Concentrations of VEGF and progesterone were greater (P < 0.05) in dams with twin vs. single fetuses. Maternal VEGF concentrations did not differ among collection times, but progesterone concentrations increased (P < 0.01) between d 192 and 234. Conversely, PAG concentrations were low at d 57 and 121 and did not differ between dams carrying singles or twins. However, the subsequent increase (P < 0.01) in PAG was greater in dams with twins, resulting in greater (P < 0.01) PAG concentrations for dams with twins at d 192 and 234 (type of birth x time; P < 0.01). Maternal IGF-I concentrations were unaffected by fetal number. Because corpora lutea persisted for the duration of the evaluation period, maternal progesterone concentrations were likely related to the number of corpora lutea rather than the number of fetuses. It is postulated that the greater PAG and VEGF concentrations in the blood of dams gestating twins are the result of a larger uteroplacental mass, including increased numbers of binucleate cells and increased angiogenesis and vasculogenesis associated with a twin pregnancy. Although PAG and VEGF were elevated in dams gestating twins, variability within and among birth groups limits the use of PAG or VEGF measurements for the diagnosis of twins.

Somatic cell nuclear transfer alters peri-implantation trophoblast differentiation in bovine embryos

Abnormal placental development limits success in ruminant pregnancies derived from somatic cell nuclear transfer (SCNT), due to reduction in placentome number and consequently, maternal/fetal exchange. In the primary stages of an epithelial–chorial association, the maternal/fetal interface is characterized by progressive endometrial invasion by specialized trophoblast binucleate/giant cells (TGC). We hypothesized that dysfunctional placentation in SCNT pregnancies results from aberration in expression of genes known to be necessary for trophoblast proliferation (Mash2), differentiation (Hand1), and function (IFN-τ and PAG-9). We, therefore, compared the expression of these factors in trophoblast from bovine embryos derived from artificial insemination (AI),in vitrofertilization (IVF), and SCNT prior to (day 17) and following (day 40 of gestation) implantation, as well as TGC densities and function. In preimplantation embryos, Mash2 mRNA was more abundant in SCNT embryos compared to AI, while Hand1 was highest in AI and IVF relative to SCNT embryos. IFN-τ mRNA abundance did not differ among groups. PAG-9 mRNA was undetectable in SCNT embryos, present in IVF embryos and highest in AI embryos. In postimplantation pregnancies, SCNT fetal cotyledons displayed higher Mash2 and Hand1 than AI and IVF tissues. Allelic expression of Mash2 was not different among the groups, which suggests that elevated mRNA expression was not due to altered imprinting status of Mash2. The day 40 SCNT cotyledons had the fewest number of TGC compared to IVF and AI controls. Thus, expression of genes critical to normal placental development is altered in SCNT bovine embryos, and this is expected to cause abnormal trophoblast differentiation and contribute to pregnancy loss.

Trophoblast cells of ruminant placentas—A minireview

The ruminant placenta is classified as cotyledonary and synepitheliochorial on the basis of its gross anatomical features and histological characteristics, respectively. The richly vascularized embryonic chorioallantois is lined on its external surface by cells of the trophectodermal epithelium. These cells which assume specialized functions are referred to as trophoblast cells. Two morphologically and functionally distinct cell types have been recognized in the trophectoderm of the placenta of ruminant animals. These are the mononucleate trophoblast cells and the binucleate trophoblast cells. The occurrence, morphological characteristics, and specialized functions of these trophoblast cells, in relation to conceptus nutrition and survival in utero are discussed in this review.

Pregnancy-associated glycoprotein family (PAG)--as chorionic signaling ligands for gonadotropin receptors of cyclic animals

The chorionic pregnancy-associated glycoprotein (PAG) family was identified in pigs, cattle and other eutherian mammals. The objective of this study was to examine whether secretory chorionic proteins (including PAGs), produced in vitro by explants of porcine and bovine placental membranes, may interact with other proteins, i.e. gonadal and extragonadal binding sites. Trophoblast (TRF) and trophectoderm (TRD) explants of pigs (n=38; 14-61 dpc-day post coitum) or cotyledons (CT) of cows (n=5; 40-110 dpc) were long-term cultured. Released chorionic proteins were ultra-fractionated from media (>10 kDa) or precipitated [20-75% of (NH(4))(2)SO(4)]. The PAGs were monitored by Western/PAGE (30-73 kDa). Secretory TRF/TRD/CT (+PAG) proteins (0.78-25 microg/ligand) were examined by radioreceptor assay (RRA) with iodinated hCG ((125)I-hCG) for binding-effectiveness by gonadotropin receptors of cyclic pigs and cows (cRc). Gonadal and extragonadal cRc isolated from luteal-phase corpora lutea and uteri (cCLRc, cMYORc and cENDRc) were tested with positive control ligands: porcine LH and hCG (0.39-50 ng/ml). Control proteins produced in vitro by endometrial (END) explants of cyclic (cEND), pseudopregnant (PsEND) and pregnant (pEND) gilts were utilised as negative ligands (0.78-25 microg/ligand). Positive control ligands competed with (125)I-hCG for binding by cCLRc, cMYORc and cENDRc (18-61%/B(0) for hCG and 27-57%/B(0) for LH). Negative ligands (cEND, PsEND and pEND) did not show cRc bindings. This is the first RRA report indicating that in vitro produced porcine TRF/TRD proteins (+PAG) competed (P< or =0.05) with (125)I-hCG for binding by cCLRc, cMYORc and cENDRc in a concentration- and pregnancy stage-dependent manner. The highest competition with (125)I-hCG (up to P< or =0.001) was found for ultra-fractionated TRF/TRD proteins (>10 kDa) during early pregnancy (<22 dpc). The greatest competition (P< or =0.05) of precipitated porcine TRD proteins (>30 dpc) was detected for fractions obtained by saturation with use of 20% of (NH(4))(2)SO(4). Bovine CT proteins revealed lower competition of (125)I-hCG for bovine cCLRc (during 45 dpc only) that was more efficient with CT (up to 71%) than with non-labelled hCG (82%). The PAG proteins may play a role as potential "signal molecules", because they were able to interact with gonadotropin receptors of luteal-phase animals. It seems that the pPAG proteins may be luteoprotective chorionic-origin signals during implantation and placentation, according to binding-effectiveness of the chorionic ligands that was comparable to LH/hCG ligands with gonadal and extragonadal receptors of cyclic animals.

Radiocompetition of secretory pregnancy-associated glycoproteins as chorionic ligands with luteal and uterine gonadotrophin receptors of pregnant pigs

Porcine pregnancy-associated glycoprotein (pPAG) family is very promiscuous and its role(s) remains unknown. The objective of this study was to identify whether secretory placental proteins (including pPAGs), produced in vitro by porcine chorionic explants, may interact with other proteins/targets, i.e. luteal and uterine binding sites of pregnant pigs. Trophoblast (TRF) and trophectoderm (TRD) were harvested during peri-implantation and placentation periods (14-61 dpc-day post coitum). In vitro-produced TRF/TRD proteins were isolated from media by ultrafractionation (>10 kDa MWCO) or precipitation with 20-75% saturation of (NH(4))(2)SO(4) and pPAG proteins were monitored by Western blotting. Secretory TRF/TRD ligands (including PAGs) were serially diluted (0.78-25 microg/ligand) and examined by radioreceptor assay (RRA). Luteal and uterine membrane receptors of pregnant pigs (pRc) were isolated from corpora lutea (pCLRc), myometrium (pMYORc) and endometrium (pENDRc). The three pRc types were harvested during three periods of pregnancy: 14 dpc (14 Rc), 21-26 dpc (21-26 Rc) and 31 dpc (31 Rc). The RRA competitions of individual TRF or TRD ligands were performed with (125)I-hCG as tracer and different pRc types. The RRA results of TRF/TRD were compared to hCG/pLH ligands--as positive controls (0.39-50 ng/ml), and endometrial (END) proteins (0.78-25 microg/ml) produced in vitro by END explants of cyclic, pseudopregnant and pregnant gilts (cEND, PsEND and pEND, respectively)--as negative control ligands. Results indicated that secretory TRF/TRD proteins (+pPAGs) were able to compete with (125)I-hCG for binding with other proteins/targets, i.e. luteal and uterine receptors of pregnant pigs (pCLRc, pMYORc and pENDRc) in a concentration- and pregnancy stage-dependent manner. This study indicated that porcine secretory 14-15 dpc TRF (pPAG; 30-73 kDa) ligands, effectively displaced (125)I-hCG tracer from pCL14Rc (up to P< or =0.01), corresponding to displacement by hCG and porcine LH. During the early stage of pregnancy, some competition tendency (P< or =0.01) was also detected for TRF ligands (14-15 dpc) with pEND14Rc. As pregnancy advanced, significant (125)I-hCG competition (at least P< or =0.05) with secretory semi-purified TRD ligands (30-42 dpc) was determined for all types of examined receptors pCL31Rc, pMYO31Rc and pEND31Rc, mainly with TRD fractions precipitated by 20% saturation of (NH(4))(2)SO(4). It seems that chorionic pPAG family can be involved in luteoprotective mechanism during implantation and placentation, according to the binding-interaction with luteal and uterine gonadotropin receptors of pregnant pigs.

Assessment of plasma profile of pregnancy-associated glycoprotein (PAG) in sheep with a heterologous (anti-caPAG55+59) RIA and its potential for diagnosing pregnancy

The purpose of the present investigation was to generate pregnancy associated glycoprotein (PAG)-profiles throughout pregnancy in a heterogenous sample of sheep using a radioimmunoassay with a heterologous antibody (anti-caPAG(55+59), #708) and utilize them for the purpose of pregnancy detection. From 2 weeks after the introduction of males into the breeding herd until 4 weeks after parturition, weekly blood samples were collected from 66 pregnant and 25 non-pregnant ewes of various breeds. Between 3 and 5 weeks after conception, plasma PAG levels increased, remained almost stable until week 17, then continued to increase, culminating in a drastic surge during the last 2 weeks of pregnancy. By 4 weeks of gestation, the plasma PAG level exceeded the level typical for non-pregnant ewes by five standard deviations, permitting a reliable pregnancy diagnosis. Plasma PAG levels were higher in twin-bearing ewes than in ewes carrying a single lamb, differences getting more evident as pregnancy proceeded. Neither breed and parity of the mother nor sex and weight of lambs borne exerted a significant effect. The heterologous assay system utilizing a caprine antibody proved to deliver results that are more consistent and less depending on various variables than those used in other studies. It may be concluded that, at the present state of development, the assay provides a reliable means of diagnosing pregnancy in sheep from the 4th week after they have been bred onward.

Ultrasound fetal measurements and pregnancy associated glycoprotein secretion in early pregnancy in cattle recipients carrying somatic clones

Somatic cloning in the bovine species leads to high levels of fetal losses which occur throughout pregnancy. These losses are most often associated with fetal overgrowth, a syndrome known as large offspring syndrome (LOS), and excessive maternal plasma pregnancy serum protein 60 (PSP60), a protein similar to a pregnancy-associated glycoprotein of 67 kDa (PAG I67) produced by the bovine placenta. Predicting the outcome of pregnancies initiated from cloned embryos has become an important issue both to prevent potential harm to the mother because of excessive fetal size at birth and also to get a better understanding of the relationships between growth, differentiation and placental functions in developing cloned fetuses. Here, we report on a systematic analysis of fetal and placental development in the first trimester of pregnancy performed by ultrasonographic imaging and by measurement of the maternal concentrations of pregnancy associated glycoproteins (PAGS), using four different radioimmunoassays (RIA) (two homologous RIA systems with PSP60 and PAG I67; two heterologous RIA systems with PAG I67 as standard and tracer, and antisera anti-caprine PAGs). We showed that crown-rump length (CRL) in clones appeared smaller than controls at 35, 50 and 62 days (P<0.05). At 62 days of pregnancy, CRL in cloned fetuses that died before 90 days was smaller compared to the other cloned fetuses (P<0.05) whereas the width of the fetal sack and the biparietal diameter (BPD) was larger in fetuses that developed LOS in late gestation (P<0.05). Maternal PAGs concentrations were statistically different between controls and all clone recipients as early as Day 34, suggesting early abnormal placental glycoprotein synthesis for clone pregnancies regardless of pregnancy outcome. This work provides a practical, non-invasive tool to follow up clone pregnancies and suggests that primary growth retardation and abnormal placental function precedes excessive fetal and placental growth at later stages of pregnancy.

Expression profile and protein levels of placental products as indirect measures of placental function in in vitro-derived bovine pregnancies

Bovine conceptus development and its association with placental proteins present in maternal, foetal and neonatal plasma and foetal (amniotic and allantoic) fluids were investigated inin vivo- andin vitro-produced (IVP) concepti and newborn calves. Females were superovulated to obtain control embryos, whereas IVP embryos were derived from establishedin vitroprocedures. Pregnant animals were slaughtered on days 90 or 180 of gestation or allowed to develop to term for the assessment of physical traits. Foetal, maternal and neonatal blood and foetal fluids were collected for the determination of bovine placental lactogen (bPL) and bovine pregnancy-specific protein B (bPSPB) concentrations. Placental transcripts for bPL and bPSPB, determined by quantitative RT-PCR, were elevated in IVP placentomes. No major physical differences were observed between groups on day 90, but concentrations of bPL and bPSPB were higher in foetal plasma and allantoic fluid of IVP concepti in day 180 pregnancies, which were correlated with larger uterine and conceptus traits. Maternal concentrations of bPL in IVP pregnancies were lower than controls during the last 8 weeks of gestation, to become similar as parturition approached. Newborn IVP calves and foetal membranes were larger and displayed higher concentrations of plasma bPL than controls (10 and 60 min after birth). Our results indicated that differential patterns of secretion of bPL and bPSPB into the maternal and foetal systems occurred at distinct stages of gestation, and these were associated with altered conceptus development afterin vitroembryo manipulations, indirectly demonstrating deviations in placental function in IVP pregnancies.

Temporospatial expression of placental lactogen and prolactin-related protein-1 genes in the bovine placenta and uterus during pregnancy

The anatomical location of binucleate cells (BNC) influences protein expression but not steroid synthesis in ruminants. In order to determine if BNC in disparate locations differentially express bovine placental lactogen (bPL) and prolactin-related protein-1 (bPRP-1), we quantitated bPL and bPRP-1 transcripts in placentomal (cotyledonary, caruncular) and interplacentomal (intercotyledonary, intercaruncular) tissues throughout pregnancy in the bovine using real-time reverse transcription PCR (RT-PCR) and in situ hybridization. Levels of both bPL and bPRP-1 transcripts at peri-implantation were significantly higher (P < 0.01) in the fetal membrane than in caruncular and intercaruncular tissues. Thereafter, mRNA for these related proteins demonstrated different spatial as well as temporal patterns of expression. Levels of bPRP-1 transcripts peaked at day 60 of pregnancy. Between day 60 and 100, bPRP-1 transcripts fell by approximately sevenfold (P < 0.01) in cotyledonary and intercotyledonary tissues, and fourfold in caruncular (P < 0.01) tissue. Levels of bPRP-1 transcripts remained low in the cotyledonary, intercotyledonary, and caruncular tissues until peripartum. In contrast, bPL expression in placentomes increased with progression of gestation (P < 0.01), but decreased in interplacentomal tissue around peripartum. To conclude, disparate patterns of bPRP-1 and bPL genes are transcribed in the placentomal and interplacentomal tissues during gestation in the bovine, suggesting that these prolactin-like hormones serve distinct functions and are regulated differently in the uteroplacental unit in this species.

Molecular evidence for a critical period in mural trophoblast development in bovine blastocysts

Embryonic and extra-embryonic lineages are separated at the blastocyst stage in the mouse at the onset of implantation but well ahead of implantation in most mammals. To provide information on the development of the trophoblast lineage in late-implanting bovine embryos, we combined the use of molecular markers defining embryonic and extra-embryonic lineages in the mouse with a transcriptomic approach dedicated to the early steps of the elongation process, a characteristic feature of blastocyst development in ruminants. In this study, we present molecular evidence for differences between the cow and the mouse in the programming of trophoblast differentiation. This different programming encompasses: (i) the expression of epiblast specifying genes (Oct-4, Nanog) in bovine trophoblast cells at the onset of elongation, (ii) the transcription of proliferation markers in early elongating blastocysts, (iii) the early detection of trophoblast-specific transcripts related to extra-embryonic tissue's differentiation (Hand1, Ets2, IFN-tau) and (iv) the identification of a new transcript (c12) which displays a reciprocal pattern to that of Oct-4 and Nanog genes in the embryonic cells and for which no equivalent has thus far been found in the mouse. Altogether, these results tended to show that early elongation is a critical transition in bovine trophoblast development.

Chorionic mRNA expression and N-glycodiversity of pregnancy-associated glycoprotein family (PAG) of the European bison (Bison bonasus)

Placental PAG mRNA expression and N-glycodiversity of multiple PAG proteins secreted in vitro by trophectoderm (chorion epithelium) of wild pecoran Bovidae taxons was not examined previously. The study on European bison (Eb) aimed: (1) to determine placental PAG mRNA expression by in situ hybridisation; (2) to identify a profile of pecoran PAG protein family secreted in vitro by cotyledonary (CT) explants; (3) to examine N-glycodiversity of the PAG proteins in this wild taxon. In addition, we compared (4) a profile and N-glycodiversity of the PAG protein family secreted in vitro by CT and interCT-trophectoderm (intCT-TRD) explants of domestic ruminants. Cotyledonary sections of the Eb were used for in situ hybridisation (ISH) with (35)S-labelled probes produced with porcine PAG cDNA as templates. Various CT and intCT-TRD explants were long-term cultured in vitro. Chorionic proteins were isolated from media, ultra-filtrated (>10 kDa MWCO) and analysed by PAGE-Western blotting with various polyclonal anti-PAG sera. Protein samples with or without enzymatic deglycosylation were examined after different times of explant cultures. Released chorionic proteins were deglycosylated by N-glycanase F (PNGase F+) and compared to glycosylated forms (PNGase F-). This is the first paper demonstrating the PAG-like mRNA transcript expression (by ISH) and N-glycodiversity of immuno-reactive PAG-like proteins (produced in vitro by chorionic explants) of European bison. Various PAG proteins of Eb (EbPAG) were secreted by CT explants during long-term in vitro studies. Major approximately 78, approximately 67 and approximately 65 kDa EbPAG-like proteins were reduced by enzymatic deglycosylation (at least by 10 kDa). Considerably smaller amounts of approximately 45 kDa EbPAG-like proteins were also observed. In addition, we have found that various PAG proteins (30-73 kDa) were secreted by bovine CT explants, during long-term in vitro cultures. Corresponding amounts of PAG proteins, similar in M(r), were also secreted by intCT-TRD explants, whose tissues were not utilised for PAG protein extraction during other scientists' previous studies. It seems that the M(r)-heterogeneity and N-glycodiversity of the PAG protein family can play very important role during feto-placental interactions in Bovidae species.

Cathepsins in the ovine uterus: regulation by pregnancy, progesterone, and interferon tau

Cathepsins (CTS) are peptidases that have biological roles in degrading extracellular matrix, catabolism of intracellular proteins, and processing of prohormones. Expression of CTSB, CTSD, CTSH, CTSK, CTSL, CTSS, and CTSZ genes was detected in the endometria of cyclic and early pregnant ewes with distinct temporal and spatial expression patterns. In the d 18 and 20 conceptus, expression of CTSB, CTSD, CTSL, and CTSZ mRNA was detected in the trophectoderm. Of particular note, CTSL mRNA was the most abundant CTS mRNA in the ovine endometrium and detected only in the luminal epithelium and superficial glandular epithelium of cyclic and pregnant ewes. CTSL mRNA increased 8-fold between d 10 and 18 in endometria of pregnant ewes, whereas it declined between d 14 and 16 in cyclic ewes. CTSL protein was also detected in conceptus trophectoderm, and pro-CTSL was detected in uterine flushings from ewes between d 12 and 16 of pregnancy. In ovariectomized and catheterized ewes, CTSL mRNA in the endometrium was increased by progesterone and intrauterine injections of ovine interferon (IFN)tau. Other endometrial CTS genes were also regulated by progesterone alone (CTSB, CTSK, CTSS, and CTSZ) or progesterone and IFNtau (CTSH, CTSK, CTSS, and CTSZ). These results indicate that CTS of endometrial and conceptus origin may regulate endometrial remodeling and conceptus implantation, endometrial CTS genes are regulated by ovarian and placental hormones, and CTSL is a novel IFNtau-stimulated gene expressed only in luminal epithelium and superficial glandular epithelium of the endometrium.

Light and electron microscope immunocytochemical studies of the distribution of pregnancy associated glycoproteins (PAGs) throughout pregnancy in the cow: possible functional implications

Pregnancy associated glycoproteins (PAGs) comprise a large group of placental antigens of the aspartic proteinase family. Phylogenetic analysis indicated that the PAGs form two distinct groups, one of ancient origin and one produced by a more recent series of gene duplications. This paper summarises the molecular biological and biochemical studies which have been used to purify and raise antibodies against specific PAGs and groups of related PAGs and their use in light and electron microscope immunocytochemistry to demonstrate that the ancient PAG group has a similar distribution at the placental fetomaternal interface (microvillar junction, MVJ) in cows and pigs. This localization suggests either a possible role in binding the surfaces together and/or in establishment of an immunological barrier. The more recently evolved PAG group, absent in the pig, exhibited no significant localization to the MVJ but was restricted to the trophoblast binucleate cell (BNC) granules in the cow. Furthermore, these PAGs bind to newly formed maternal uterine connective tissue to which they are delivered by BNC migration and fusion with uterine epithelial cells. At this location in the developing maternal villi of the placentomes, they are ideally positioned to manipulate the maternal immune system to facilitate a successful pregnancy.

The establishment of an ELISA for the detection of pregnancy-associated glycoproteins (PAGs) in the serum of pregnant cows and heifers

The pregnancy-associated glycoproteins (PAGs) are a large gene family expressed in trophoblast cells of ruminant ungulates. The detection of PAGs (more specifically, PAG-1) in maternal serum has served as the basis for pregnancy detection in cattle. Unfortunately, PAG-1 and/or antigenically-related PAGs exhibit a long half-life in maternal serum (>8 d) and can be detected 80-100 d post-partum, thereby producing false positives in animals bred within 60-d of calving. The goal of the present studies was to develop a monoclonal-based assay that targeted early-pregnancy PAGs whose persistence in maternal serum post-partum might be relatively short-lived. Three anti-PAG monoclonal antibodies that recognized distinct subsets of PAGs were selected and used as trapping reagents in a 'sandwich' type of enzyme-linked immunosorbant assay (ELISA). A polyclonal antiserum with broad specificity was used for detecting bound PAGs. A total of 42 cows and heifers were bled daily on day 15, days 22 to 28, and then weekly throughout pregnancy and for 10 weeks (approximately 70 d) into the post-partum period. The ELISA was able to detect PAG in maternal serum of all animals unambiguously by day 28 post-insemination (PAG concentration: 8.75 +/- 3.04 ng/mL). In maternal serum, PAG concentrations peaked during the week of parturition at 588.9 +/- 249.9 ng/mL, and after calving, PAG was completely cleared (half-life: 4.3 d) by eight-week post-partum in 38 of 40 of the animals tested and was at very low concentrations in the remaining two (1.4 and 4.9 ng/mL, respectively). In summary, a monoclonal-based assay has been established that is sensitive enough to detect PAG in maternal serum by the forth week of pregnancy, but does not suffer from carry-over of antigen from a previous pregnancy.

Pregnancy associated glycoprotein-1, -6, -7, and -17 are major products of bovine binucleate trophoblast giant cells at midpregnancy

Pregnancy associated glycoproteins (PAGs) are extensively glycosylated secretory proteins of ruminant trophoblast cells. In cattle placenta several PAG cDNAs are expressed, but the variety of correspondent proteins and their degree of glycosylation are not well characterized. Thus, we purified PAGs by using a protocol which included a lectin (Vicia villosa agglutinin) affinity chromatography. Due to their specific glycosylation pattern, PAGs derived from binucleate trophoblast giant cells were highly enriched by this protocol. PAGs were purified from cotyledons of 2 day 100 placentas and from a single placenta at day 155 and 180. In all samples three major bands (75; 66; 56 kDa) were detected by one-dimensional SDS-PAGE. Mass-spectrometric analysis identified the 75 kDa band as a mixture of PAG-7 and PAG-6, the 66 kDa band as PAG-1 and the 56 kDa band as PAG-17. N-terminal sequencing of the day 100 sample confirmed the mass spectrometric identifications. Enzymatic release of N-glycans with peptide-N-glycanase-F from PAGs reduced the molecular weight to approximately 37 kDa which corresponds to the theoretical molecular mass of PAGs. Limited peptide-N-glycanase-F treatment revealed that all four N-glycosylation sites are quantitatively occupied in PAG-1. Compared to PAG-1 the number of potential N-glycosylation sites is lower in PAG-17 (three sites) and higher in PAG-6 and -7 (five and six sites, respectively). This suggests that the number of attached N-glycans is the main determinant of molecular mass of bovine PAGs. The degree of glycosylation may be a major factor regulating the plasma half life of PAGs.

Relationship between follicle size at insemination and pregnancy success

Administration of gonadotropin-releasing hormone (GnRH) induces a surge of luteinizing hormone and ovulation in a variety of species, including human beings. Our objectives were to determine the effect of follicle size at the time of ovulation on corpus luteum function and establishment and maintenance of pregnancy in cows in which ovulation was either spontaneous or induced with GnRH. GnRH-induced ovulation of follicles < or approximately = 11 mm in diameter resulted in decreased pregnancy rates and increased late embryonic mortality. This decrease in fertility was associated with lower circulating concentrations of estradiol on the day of insemination, a decreased rate of increase in progesterone after insemination, and, ultimately, decreased circulating concentrations of progesterone. In contrast, ovulatory follicle size had no apparent effect on fertility when ovulation occurred spontaneously. Follicles undergoing spontaneous ovulation do so at a wide range of sizes when they are physiologically mature. Therefore, administration of GnRH to induce ovulation likely initiates a preovulatory gonadotropin surge before some dominant follicles attain physiological maturity. GnRH-induced ovulation of follicles that are physiologically immature has a negative impact on pregnancy rates and late embryonic/fetal survival. These observations in cattle may have implications for assisted reproductive procedures in human beings.

Gene Expression Profiles of Bovine Trophoblastic Cell Line (BT-1) Analyzed by a Custom cDNA Microarray

Gene expression of bovine trophoblast cell line (BT-1) was analyzed with a custom utero-placenta complementary DNA microarray. Expression comparison with in vivo tissues of trophoblast derivation was performed to investigate characteristics of the expression in BT-1. BT-1 is a cell line established without feeder cells using trophoblast cells that are separated from bovine blastocysts. The bovine in vivo tissues of the trophoblast derivation were collected on day 17 through 56 of gestation. Of 1,773 genes, 933 exhibited an expression difference exceeding two-fold between BT-1 and in vivo tissues. These genes were analyzed by the k-means clustering method and were distributed into six clusters. Some genes, such as placental lactogen, interferon-tau and pregnancy-associated glycoproteins, all known as trophoblast-specific genes, were detected in BT-1 as well as in vivo tissues throughout the experiment period. These trophoblast-specific genes and octamer-binding transcription factor-4, known as a marker for undifferentiation of cells in mice, were detected by RT-PCR in both BT-1 and in vivo trophoblast tissues. The overall gene expression profile in BT-1 suggests that this cell line contains trophoblast-specific characteristics and is similar to trophoblast cells around the implantation period.

Binucleate trophoblast giant cells in the water buffalo (Bubalus bubalis) placenta

The binucleate trophoblast giant cells (BNC) of the water buffalo, Bubalus bubalis, placenta were studied, with emphasis on the synthesis of BNC-specific proteins. Placentomal tissues of 27 water buffalos (2-10 months of pregnancy) were processed for light and electron microscopy. The frequency of BNCs was 20% of the trophoblastic cells in 2-3-month placentas and increased to 27% in the later stages. Ultrastructurally, binucleate cells displayed a prominent granular endoplasmic reticulum and Golgi apparatus, typical of cells involved with protein synthesis and exportation. The buffalo BNCs contained periodic acid-Schiff (PAS)-positive granules and reacted with antisera against bovine placental lactogen, prolactin-related protein-I, and pregnancy-associated glycoproteins. Lectin histochemistry with Dolichos biflorus agglutinin, Vicia villosa agglutinin, and Phaseolus vulgaris leucoagglutinin showed specific staining of BNCs. Different stages of BNC migration and fusion with uterine epithelial cells were observed. Trinucleate feto-maternal hybrid cells were the typical outcome of cell fusions. These cells underwent degeneration, with typical morphological features of apoptosis. The results revealed a strong homology between water buffalo and cattle BNCs concerning cell morphology, protein expression, glycosylation pattern, and characteristics of cell migration and fusion.

cDNA microarray analysis of bovine embryo gene expression profiles during the pre-implantation period

Background

After fertilization, embryo development involves differentiation, as well as development of the fetal body and extra-embryonic tissues until the moment of implantation. During this period various cellular and molecular changes take place with a genetic origin, e.g. the elongation of embryonic tissues, cell-cell contact between the mother and the embryo and placentation. To identify genetic profiles and search for new candidate molecules involved during this period, embryonic gene expression was analyzed with a custom designed utero-placental complementary DNA (cDNA) microarray.

Methods

Bovine embryos on days 7, 14 and 21, extra-embryonic membranes on day 28 and fetuses on days 28 were collected to represent early embryo, elongating embryo, pre-implantation embryo, post-implantation extra-embryonic membrane and fetus, respectively. Gene expression at these different time points was analyzed using our cDNA microarray. Two clustering algorithms such as k-means and hierarchical clustering methods identified the expression patterns of differentially expressed genes across pre-implantation period. Novel candidate genes were confirmed by real-time RT-PCR.

Results

In total, 1,773 individual genes were analyzed by complete k-means clustering. Comparison of day 7 and day 14 revealed most genes increased during this period, and a small number of genes exhibiting altered expression decreased as gestation progressed. Clustering analysis demonstrated that trophoblast-cell-specific molecules such as placental lactogens (PLs), prolactin-related proteins (PRPs), interferon-tau, and adhesion molecules apparently all play pivotal roles in the preparation needed for implantation, since their expression was remarkably enhanced during the pre-implantation period. The hierarchical clustering analysis and RT-PCR data revealed new functional roles for certain known genes (dickkopf-1, NPM, etc) as well as novel candidate genes (AW464053, AW465434, AW462349, AW485575) related to already established trophoblast-specific genes such as PLs and PRPs.

Conclusions

A large number of genes in extra-embryonic membrane increased up to implantation and these profiles provide information fundamental to an understanding of extra-embryonic membrane differentiation and development. Genes in significant expression suggest novel molecules in trophoblast differentiation.

Generation and purification of recombinant bovine pregnancy associated glycoprotein

Bovine pregnancy-associated glycoprotein-1 (bPAG-1) is predicted to play an essential role during pregnancy and is labelled as a potential biochemical marker of pregnancy in ungulates. We have compared the generation of the glycosylated form of recombinant bPAG-1 (rbPAG-1) by human embryonic kidney 293 (HEK 293) and Chinese hamster ovary (CHO) cells in attached cultures and evaluated the adaptation of the rbPAG-1 transfected cell line to suspension culture. The PAG cDNA was cloned from placental RNA obtained from a slaughtered cow on day 55 of pregnancy. The PAG-pRcRSV expression vector was transfected into HEK 293 and CHO cells. Western blot analysis showed that clonal HEK 293 cells expressed rbPAG-1 better than CHO cells in attached cultures. Transfected HEK 293 cells were adapted to suspension culture in spinner flasks and the rbPAG-1 purified to homogeneity using ion-exchange, pepstatin-sepharose affinity chromatographies and preparative SDS-PAGE. The expression of rbPAG-1 was immunocharacterised using a polyclonal antibody. Our findings indicated that 293 cells are suitable for production of glycosylated form of rbPAG-1 and that the availability of the recombinant glycoprotein will aid in further studies to elucidate the function and structure of the protein.

Effects of an experimental Trypanosoma congolense infection on the reproductive performance of West African Dwarf goats

Thirty-six West African Dwarf (WAD) goats were used to assess the effects of an experimental Trypanosoma congolense infection on their reproductive system. Estrous cycles were synchronised and when confirmed pregnant (n = 31), the does were randomly allocated into control and trypanosome-infected groups. After infection, the animals were carefully observed till parturition. Trypanosome infection caused an increase of rectal temperature, a significant drop in PCV (infected: 23.3 +/- 0.3%; control: 28.5 +/- 0.4%; P < 0.0001) and abortions in 27.8% of the infected does. Kids born from infected does had a lower birth weight than kids born from control goats (0.9 +/- 0.1 kg versus 1.6 +/- 0.1 kg; P < 0.0001). Eight out of 13 kids (61.5%) that were born alive from infected does died during their first week of life. Plasma pregnancy-associated glycoprotein (PAG) and progesterone concentrations were lower in the infected animals than in the controls. In general, PAG concentration in does which aborted dropped before abortion. Our results revealed that artificial T. congolense infection affected reproductive performance of WAD goats with abortions, premature births and perinatal losses being observed. Neither transplacental transmission of T. congolense nor histopathological lesions of the placenta could be demonstrated.

Quantitative analysis throughout pregnancy of placentomal and interplacentomal expression of pregnancy-associated glycoproteins-1 and -9 in the cow

The multigenic pregnancy-associated glycoproteins (PAG) exhibit spatially and temporally distinct pattern across gestation in the bovine. The majority of the bovine bPAG are localized to the binucleate cells (BNC) while some are expressed throughout the trophectoderm. Bovine (b)PAG-1 and -9 are both localized to the BNC but are differentially transcribed. In addition, the anatomical location of BNC does influence protein expression in the ungulates. Therefore, the objective of the present study was to compare and contrast bPAG-1 and -9 transcriptions in the placentomal (cotyledonary, caruncular) and interplacentomal (intercotyledonary, intercaruncular) tissues throughout pregnancy in the bovine using real-time reverse transcription PCR (RT-PCR) and by in-situ hybridization. The levels of bPAG-9 transcription in the fetal membrane at peri-implantation were significantly (P<0.01) higher than bPAG-1. The expression of bPAG-9 in the placentomal and interplacentomal tissues were significantly (P<0.01) higher than bPAG-1 during the first trimester of gestation. The transcription of bPAG-1 in the placentomal and interplacentomal tissues were significantly (P<0.01) higher than bPAG-9 from mid-gestation to peripartum. The expression of bPAG-1 and -9 throughout gestation were significantly (P<0.01) affected by the anatomical location of BNC. In situ analysis paralleled the expression patterns of bPAG-1 and -9 across gestation. These findings indicate that bPAG-9 expression in the placentomal and interplacentomal tissues predominates in the first trimester of gestation while bPAG-1 transcription was primarily higher in the last two trimesters of gestation. The cellular location had significant effect on bPAG-1 and -9 transcription.

Expression of trophoblast cell-specific pregnancy-related genes in somatic cell-cloned bovine pregnancies

We compared the expression of bovine prolactin-related protein-1 (bPRP-1), placental lactogen (bPL), and pregnancy-associated glycoproteins-1 (bPAG-1) and -9 (bPAG-9) genes in artificially inseminated (AI) and nuclear transferred (NT) cows during the first trimester of gestation using real-time reverse transcription-polymerase chain reaction and in situ hybridization. Placentomal (cotyledonary, caruncular) and interplacentomal (intercotyledonary, intercaruncular) tissues of AI and NT cows carrying either motile (M) or immotile (IM) fetuses were examined. Transcripts for bPL and bPAG-9 were lower (P < 0.01) in the fetal membranes of NT (n = 4) cows at Day 30 of gestation, compared with AI (n = 4) cows. There was no difference in the mean (+/- SEM) levels of expressions of bPRP-1, bPL, and PAG-1 in the placentomal and interplacentomal tissues of AI (n = 5) and NT (M, n = 4) cows at Day 60 of gestation. The mRNAs for bPRP-1, bPL, bPAG-1, and bPAG-9 genes were higher (P < 0.01) in the caruncular tissue of AI cows, compared with NT (IM, n = 4) cows at Day 60 of gestation. Expression of bPRP-1, bPL, bPAG-1, and bPAG-9 in the placentomal and interplacentomal tissues of the NT (n = 3) group varied considerably more, compared with the AI (n = 4) group at Day 100 of gestation. These findings suggest defective binucleate cell-specific gene transcriptional commands in NT cows.

Characterization of gene expression profiles in early bovine pregnancy using a custom cDNA microarray

Gene expression analysis comparing nonpregnant with pregnant bovine uteri, including placenta, was performed with a custom cDNA microarray containing 1,933 independent genes. These genes were classified into six categories according to biological function, as follows: cell and tissue structural dynamics (108 genes), intercellular communication (221), intracellular metabolism (265), cell cycle and apoptosis (26), regulation of gene expression (113), expressed sequence tag (EST) and function unknown (617), and uncomplemented genes (583 clones). This array possessed bovine placental/endometrial specificity, as it included many pregnancy-specific molecules, such as pregnancy-associated glycoprotein-1 (PAGs), placental lactogen (PLs), and prolactin-related protein-1 (PRPs). A total of 77 genes were induced and 12 repressed in the placenta/endometrium. Our results point to a fundamental role for bovine placental-specific genes such as PAGs, PLs, and PRPs, in implantation and placentogenesis, and document that cDNA microarray analysis from bovine placenta/endometrium is possible and is a specific tool for monitoring genome-wide gene expression during the establishment and maintenance of pregnancy.

Implantation and placental development in somatic cell clone recipient cows

Successful somatic cloned animal production has been reported in various domesticated species, including cattle; however, it is associated with a high rate of pregnancy failure. The low cloning yield could possibly arise from either an abnormal and/or poorly developed placenta. In comparison to control cows, fewer placentomes were found in somatic cell nuclear recipient (NT) cows at day 60 of gestation, suggesting a retardation of fetal/placental growth in these animals. NT cows not only had fewer numbers of chorionic villi but also had poorly developed caruncles. Macroscopic examination revealed atypical development of the placentome in terms of shape and size. Histological disruption of chorionic villi and caruncular septum was found in NT cows. Of particular interest was that the expression of genes, as well as proteins in the placentome, was disparate between NT and artificially inseminated cows, especially placental lactogen (PL) and pregnancy-associated glycoprotein (PAG). In contrast, prolactin-related protein-1 (PRP-1) signals were comparable across cows, including NT cows carrying immotile fetuses. The expression of extracellular matrix degrading molecule, heparanase (HPA), in NT cows was divergent from that of control cows. Microarray data suggest that gene expression was disorientated in early stages of implantation in NT cows, but this was eliminated with progression of gestation. These findings strongly support a delay in trophoblast development during early stages of placentation in NT cows, and suggest that placental specific proteins, including PLs, PAGs, and HPA, are key indicators for the aberration of gestation and placental function in cows.

Double radial immunodiffusion as a tool to identify pregnancy-associated glycoproteins in ruminant and nonruminant placentae

Pregnancy-associated glycoproteins (PAGs) are antigens synthesized in the superficial layers of the ruminant trophoblast. Initially, they were identified either as proteins released into the maternal bloodstream (where they have applications in pregnancy diagnosis) (PAG1) or as molecules binding to the LH receptor (PAG2). In this study, double radial immunodiffusion was used to test the ability of antisera raised against different PAG molecules (bovine, ovine and caprine) to react with placental extracts from nonruminants (rabbit, cat, mouse, pig, and wild pig) and ruminants (cow, ewe, and goat). Placental extracts from all nonruminants tested except rabbit reacted with anti bovine PAG2 (anti-boPAG2). Extracts of ruminant placentas reacted with different antisera, confirming the expression of various PAG molecules. According to the time at which the placentas were collected (early or middle pregnancy), the reaction differed as regards the thickness, position, and number of precipitation lines, suggesting that PAG expression varies as pregnancy progresses. Bos indicus and Bos taurus placental extracts exhibited different reactions with anti-boPAG2: a single precipitation line in the former case and two lines in the latter. This suggests differential expression of boPAG2 related glycoproteins in these two subspecies.

Pregnancy-associated glycoprotein concentrations during pregnancy and the postpartum period in Azawak Zebu cattle

Specific RIA systems were developed and used to measure pregnancy-associated glycoprotein (PAG) concentrations during gestation and the postpartum period in Azawak Zebu cows. Twelve females were palpated per rectum and diagnosed as pregnant. Blood samples were taken at 5-10-day intervals from approximately Week 8 of gestation until Week 10 postpartum (pp). One Zebu cow (Z15) initially diagnosed as pregnant showed PAG concentrations lower than the assay sensitivity (<0.20 ng/ml) and did not calve. Another cow (ZSand) showed abnormally high PAG concentrations during gestation and was excluded from the general PAG profile. The 10 other Zebu cows exhibited a very similar PAG profile. In these animals, concentrations increased progressively from Week 8 to 35 of gestation (from 6.0+/-4.2 to 196.0+/-34.8 ng/ml), remaining relatively constant until Week 39 (210.8+/-74.8 ng/ml), when they increased sharply to reach their highest level (1095.6+/-607.2 ng/ml) at around parturition. After delivery, PAG concentrations declined significantly (P<0.05) until Week 2 postpartum (348.4+/-85.6 ng/ml) and slowly until Week 10 postpartum. Our results revealed that the PAG pattern in Zebu cattle was similar to those of taurine breeds during the first two trimesters of pregnancy, but differed in the peripartum period.

In bovine binucleate trophoblast giant cells, pregnancy-associated glycoproteins and placental prolactin-related protein-I are conjugated to asparagine-linked N-acetylgalactosaminyl glycans

Bovine binucleate trophoblast giant cells (BNCs) produce large amounts of PAS-positive cytoplasmic granules. After fusion of BNCs with uterine epithelial cells, the contents of these granules are released into the maternal stroma which underlies the uterine epithelium. Histochemically, the granules can be labeled with N-acetylgalactosamine-specific lectins ( Dolichos biflorus, Vicia villosa, and Wisteria floribunda agglutinins) and with Phaseolus vulgaris leucoagglutinin. In this study, we used lectin western blot analysis of proteins from fetal cotyledons to characterize the lectin binding glycoproteins. Lectin western blots showed several bands. A main band of approximately 65 kDa was identified as pregnancy-associated glycoproteins (PAGs) and a double band at 34-35 kDa as prolactin-related protein-I (PRP-I) by their crossreactivity with specific antisera. Enzymatic cleavage of N-linked glycans with peptide- N-glycanase F abolished the lectin binding to PRP and PAGs in western blots, revealing that the lectins bound to asparagine-linked glycans. The high specificity of the lectins was used for the enrichment of PRP-I and PAGs from placental cotyledons with Vicia villosa lectin affinity chromatography. The occurrence of the relatively uncommon asparagine-linked N-acetylgalactosaminyl glycans on secretory proteins of the BNCs suggests a functional role of this specific glycosylation pattern.

Aspartic proteinase members secreted by the ruminant placenta: specificity of three radioimmunoassay systems for the measurement of pregnancy-associated glycoproteins

Pregnancy-associated glycoproteins (PAGs) isolated from the placenta of various ruminant species are enzymatically inactive members of the aspartic proteinase family. The measurement of these proteins in the maternal blood can be a good indicator of the presence of a live embryo. As certain aspartic proteinases are present in biological fluids in physiological and pathological conditions at various concentrations, it was necessary to determine the specificity of three radioimmunoassay (RIA) systems currently used for the detection of PAG molecules. Commercially available members of the aspartic proteinase family like pepsinogen, pepsin, chymosin, rennet, cathepsin D and renin were tested in a wide concentration range (10 ng/ml - 1 mg/ml). Pepsinogen cross-reacted in RIA 1, RIA 2 and RIA 3 over 1 mg/ml, 50 microg/ml and 500 microg/ml concentrations, respectively. In the presence of pepsin, cross-reaction was observed in RIA 1, RIA 2 and RIA 3 over 1 mg/ml, 500 microg/ml and 1 mg/ml concentrations, respectively. Chymosin and rennet could cross-react in RIA 2 and RIA 3, while renin and cathepsin D did not decrease the binding of the tracer to antisera more, than that of the minimal detection limit. As the plasma/serum concentrations of the examined aspartic proteinases reported in the literature were outside the concentration range where cross-reaction was observed, it can be concluded that these RIA systems were specific for the detection of PAGs in biological fluids.

The placental expression of the porcine pregnancy-associated glycoprotein (pPAG) gene family examined in situ and in vitro

The objective of the study was to define the expression of the porcine pregnancy-associated glycoprotein (pPAG) gene family, including pPAG1, pPAG2, pPAG3, pPAG4 and pPAG6 that belong to the aspartic proteinase family. Porcine pPAG2, PAG4 and pPAG6 are members of a subfamily (pPAG2-like), which all have highly conserved sequences to pepsins, within two catalytic domains, suggesting enzymatic activity of these molecules. In contrast, pPAG1 and pPAG3 have catalytic sites with critical amino acid substitutions that likely render these molecules enzymatically inactive. The expression of pPAG mRNA was examined by using in situ hybridisation (ISH) in placental tissues or cultured cells and by ribonuclease protection assay (RPA). The pPAG protein family, secreted in vitro during long-term cultures, was examined using Western blotting. The trophoblastic pPAG mRNA expression starts around implantation and is continued in chorionic epithelium (trophectoderm) throughout pregnancy. ISH performed on porcine placental sections with pPAG antisense cDNA probes revealed an expression of pPAG transcripts, locally restricted only to trophectoderm. The pPAG2-like mRNA expression occurred in different trophectoderm cells. Some trophoblast cells were bigger than others and were involved in local rearrangements of maternal epithelium layer, especially in developing placental folds. A high similarity of dominating pPAG2-like transcript expression was confirmed by RPA analysis. Cultures of trophoblast cells revealed their differentiation to multinucleated forms that were not observed in situ. This confirms a strong inhibitory effect of the maternal microenvironment of uterine lumen on mononuclear trophoblast within porcine placental units that was not present during the development of multinucleated trophoblast cells in vitro. Long-term cultures of chorionic explants revealed a very efficient system of pPAG protein production in vitro. Western blotting of secretory pPAG proteins indicated similar immunologic epitope(s) of these molecules and pregnancy-stage dependent profile of chorionic secretion. Thus, some of the subpopulation(s) of porcine trophoblast cells expressing pPAG2-like transcripts and their secretory products can play an important role(s) in the mechanism(s) of the confrontation between trophoblast/trophectoderm cells and maternal endometrial epithelium during implantation, placenta formation and successful pregnancy maintenance in the pig.

Comparison of the ability of three radioimmunoassay to detect pregnancy-associated glycoproteins in bovine plasma

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Pregnancy-associated glycoproteins (PAGs) constitute a large family of glycoproteins that are synthesized in the superficial layer of the ruminant placenta according to a spatial and temporal expression pattern. When PAGs are released in the maternal blood they can be used for pregnancy diagnosis, pregnancy follow-up and for the monitoring of the trophoblastic function. Three different radioimmunoassay systems (RIA 1, RIA 2 and RIA 3) using antisera produced against PAG I67 (RIA 1), PAG55+62 (RIA 2) and PAG55+59 (RIA 3) were used in this investigation in order to measure the PAG concentration in plasma samples withdrawn from pregnant cows and heifers during different periods following artificial insemination (AI). These systems were able to detect PAG molecules in the maternal blood as early as 21 days after AI in different concentrations (RIA 1: 0.43 +/- 0.24 ng/ml, mean +/- SD; RIA 2: 0.48 +/- 0.24 ng/ml; RIA 3: 0.64 +/- 0.37 ng/ml). On days 32 and 42 RIA 2 (4.30 +/- 1.32 ng/ml and 5.56 +/- 1.95 ng/ml) and RIA 3 (4.17 +/- 1.15 ng/ml and 5.60 +/- 1.89 ng/ml) presented significantly (p < 0.0001) higher PAG concentrations than those of RIA 1 (2.43 +/- 0.81 ng/ml and 4.01 +/- 1.48 ng/ml), respectively. After day 21, significant correlations (p < 0.0001; r >/= 0.929) were determined between the three systems. Additionally the three individual PAG profiles presented in this study showed that PAG molecules secreted in the maternal blood between 21 and 50 days after AI were better recognized by the RIA 2 and RIA 3 systems. This study clearly indicated that the ability of a RIA test to recognize PAG molecules in the maternal blood can be improved by carefully selecting the antiserum.

Gene for porcine pregnancy-associated glycoprotein 2 (poPAG2): its structural organization and analysis of its promoter

The pregnancy-associated glycoproteins (PAG) are abundant secretory products of the placental trophectoderm of ungulate species. They are structurally related to pepsin, having the capability to bind peptides. However, many cannot function as enzymes due to amino acid substitutions in and around the catalytic site. Here, we demonstrate that pigs, like cattle and sheep, but unlike equids, have multiple PAG genes. One of the transcribed porcine PAG (poPAG) genes, the one for poPAG2, was cloned. It had a nine-exon organization similar to that of other mammalian aspartic proteinase genes with an atypical TATA sequence. A total of 1.2 kbp upstream from exon 1 was sequenced. This region shared identity (> 65%) with the promoter regions of the bovine (bo) PAG1, boPAG2 and equine (eq) PAG genes, but not with other aspartyl proteinase genes, including that of pepsinogen A. Nor were there clear similarities to the promoters of other genes with trophoblast-specific expression. Of the different poPAG2 promoter constructs tested in transfection experiments in two human (JAr and JEG3) and one rat (Rcho) choriocarcinoma cell lines, only the shortest (-149 bp) was required to provide full expression of a luciferase reporter. Although this short promoter was not active in Cos-1 and L-929 cells, it was active in CHO cells, a transformed non-trophoblast hamster ovarian cell line. Co-transfection of Ets2 elevated the activity of this short promoter approximately six-fold in JAr cells, but, disruption of the two putative Ets sites did not alter the ability of Ets2 to transactivate the promoter. In the non-trophoblast cell lines, Ets2 failed to elicit any response. Ets2 responsiveness may be a common feature of most or all trophoblast-expressed genes, although in the case of poPAG2, the effect may be indirect.

An aspartic proteinase expressed in the yolk sac and neonatal stomach of the mouse

A murine aspartic proteinase, described herein, is intermediate in amino acid sequence identity between the placentally produced pregnancy-associated glycoproteins (PAGs) and gastric pepsins. While PAGs are secreted products of placental trophoblast tissue of ungulates and most are not believed to function proteolytically, pepsins are digestive enzymes. The cDNA for this aspartic proteinase was amplified by reverse transcription-polymerase chain reaction from RNA extracted from murine placentas and neonatal stomachs. The open reading frame encoded a 387-amino acid polypeptide with a 15-residue signal sequence. The enzyme most resembled pepsinogen F (a protein identified in the stomachs of neonatal rabbits and rats) and PAG-like proteins cloned from equine and feline placentae. In the stomach, both its mRNA and protein were expressed in gastric chief cells of preweaned neonates. Within the placenta, its mRNA was present in both the parietal and visceral yolk sacs. However, the protein was most prevalent in the visceral yolk sac, with little detectable in the parietal yolk sac. The recombinant protein was expressed in Escherichia coli. This protein was capable of self-activation and exhibited proteolytic activity toward casein. The presence of this enzyme in two organs involved in the selective transcellular transport of proteins suggests that it has specialized digestive functions.

Caprine pregnancy-associated glycoproteins (PAG): their cloning, expression, and evolutionary relationship to other PAG

Pregnancy-associated glycoproteins (PAG) are structurally related to aspartic proteinases and belong to an extensive, rapidly evolving family of recently duplicated genes expressed in the placentas of artiodactyl species. The aim of the present study was to clone PAG from the goat, study their temporal and cell-specific expression, and determine their phylogenetic relationship to PAG from other species. RT-PCR was used to generate PAG cDNA from pooled placental RNA obtained between days 45 and 115 of pregnancy. A total of 11 cDNA, which differed by > 5% from each other, were selected for complete bidirectional sequencing from 60 clones analyzed. A group of nine (caPAG1, caPAG3-7(var), caPAG9-11), which displayed > 80% sequence identity with each other, were expressed after day 45 of pregnancy and were localized to trophoblast binucleate cells. These PAG demonstrated an unusually high ratio of nonsynonymous (amino acid changing) to synonymous nucleotide differences. CaPAG2, by contrast, was detectable only in early pregnancy (days 18 and 19) and expressed throughout trophectoderm. It was of more ancient origin than the PAG1 group, but more recent than caPAG8. The latter was expressed at all stages examined (days 18 to 115). The data confirm that many PAG genes, with different patterns of temporal and spatial expression, are transcribed in the placenta of the goat. The data also suggest that the recently duplicated PAG genes are being selected for rapid diversification of function.