Pregnancy-associated glycoprotein (PAG) family localized in chorionic cells within the epitheliochorial/diffuse placenta of the alpaca (Lama pacos)

Term alpaca placenta glycosylation profile and its correlation with pregnancy maintenance and fetal survival

Alpaca is a South American camelid, particularly present in Peruvian highlands, where oxygen concentration and atmospheric pressure are very low. Due to this fact, gestational physiology has adapted to preserve the conceptus' and mother's health. In this context, several cellular and molecular features play an essential role during and at the end of gestation. Structural carbohydrates act on maternal-fetal communication, recognize exogenous molecules, and contribute to placental barrier selectivity. Therefore, this study aimed to characterize the structural carbohydrate profiles that are present in the term alpaca placenta, kept in their natural habitat of around 4,000 m height. For this propose, 12 term alpaca placentas were collected, and the material was obtained at the time of birth from camelids raised naturally in the Peruvian highlands, in the Cusco region. All placenta samples were processed for histological analysis. A lectin histochemical investigation was performed using 13 biotinylated lectins, allowing us to determine the location of carbohydrates and their intensity on a semi-quantitative scale. Our results demonstrated that during term gestation, the epitheliochorial alpaca placenta shows a high presence of carbohydrates, particularly glucose, α-linked mannose, N-acetylglucosamine β (GlcNAc), galactose (αGal), and N-acetylgalactosamine α (GalNAc), present in the trophoblast, amnion epithelium, and mesenchyme, as well as the presence of sialic acid residues and low affinity for fucose. In fetal blood capillaries, the presence of bi- and tri-antennary complex structures and α-linked mannose was predominated. In conclusion, we characterized the glycosylation profile in the term alpaca placenta. Based on our data, compared to those reported in the bibliography, we suggest that these carbohydrates could participate in the labor of these animals that survive in Peruvian extreme environments.

Evaluation of a cattle rapid test for early pregnancy diagnosis in sheep

The early pregnancy diagnosis allows optimizing production and timely management correction, with a greater reproductive output of livestock. The Idexx Rapid Visual Pregnancy Test® consists of an ELISA for visual reading which does not require the use of readers in the laboratory, with satisfactory pregnancy diagnoses at 28 days of pregnancy in cattle. Therefore, the aim of this study was to evaluate this rapid test and to verify the most appropriate day for the diagnosis of pregnancy in the ovine species. For this purpose, 98 serum samples from pregnant sheep and 36 from non-pregnant were used, with duplicate samples, and diagnosis was confirmed by ultrasound examination, used as the gold standard. The numbers of positive samples obtained at 26, 28, and 30 days of pregnancy were 26, 27, and 45, respectively. The Rapid Visual Pregnancy Test correctly identified 100% of the samples as positive at pregnancy of days 26, 28, and 30. The sensitivity and specificity of the test were also 100%. The Idexx Rapid Visual Pregnancy Test, initially indicated for cattle, is effective for the detection of pregnancy in the ovine species, enabling diagnosis of pregnant sheep from the 26th day of pregnancy.

Identification of pregnancy-associated glycoprotein family (PAG) in the brown bear (Ursus arctos L.)

Pregnancy-associated glycoproteins (PAGs) are abundant embryo-originated products expressed in the pre-placental trophoblast and, later, in the post-implantational chorionic epithelium of some mammalian species. This paper describes the identification and cellular immunolocalization of the chorionic PAG family in the discoidal-type placenta of the brown bear (Ursus arctos L. - Ua), in which the PAGs were named 'UaPAG-Ls'. The study used: 1) Western blot for total placental glycoproteins; and 2) cross-species heterologous double fluorescent immunohistochemistry (IHC) for cellular immune-localization of the PAGs. This is the first study reporting the identification and immunolocalization of the UaPAG-L family in placental cells during early pregnancy in the brown bear. Our Western analysis revealed a dominant mature 72 kDa UaPAG-L isoform was expressed in all Ua placentas during early pregnancy. Various other UaPAG-L isoforms (16-66 kDa) were also identified. Using IHC, the UaPAG-L proteins were localized to trophectodermal cells (TRD), where signal intensity resembled intense TRD proliferation within developing placenta. The data increases our general knowledge of PAG proteins localized in discoidal-type placenta during early pregnancy in the brown bear.

Identification of Placental Aspartic Proteinase in the Eurasian Beaver (Castor fiber L.)

Aspartic proteinases (AP) form a multigenic group widely distributed in various organisms and includes pepsins (pep), cathepsins D and E, pregnancy associated glycoproteins (PAGs) as well as plant, fungal, and retroviral proteinases. This study describes the transcript identification and expression localization of the AP within the discoid placenta of the Castor fiber. We identified 1257 bp of the AP cDNA sequence, encoding 391 amino acids (aa) of the polypeptide precursor composed of 16 aa signal peptide, 46 aa pro-piece, and 329 aa of the mature protein. Within the AP precursor, one site of potential N-glycosylation (NPS^119–121) and two Asp residues (D) specific for the catalytic cleft of AP were identified (VLFDTGSSNLWV^91–102 and GIVDTGTSLLTV^277–288). The highest homology of the identified placental AP nucleotide and aa sequence was to mouse pepsinogen C (75.8% and 70.1%, respectively). Identified AP also shared high homology with other superfamily members: PAGs, cathepsins, and napsins. The AP identified in this study was named as pepsinogen/PAG-Like (pep/PAG-L). Diversified pep/PAG-L protein profiles with a dominant 58 kDa isoform were identified. Immune reactive signals of the pep/PAG-L were localized within the trophectodermal cells of the beaver placenta. This is the first report describing the placental AP (pep/PAG-L) in the C. fiber.

Identification of Novel Placentally Expressed Aspartic Proteinase in Humans

This study presents pioneering data concerning the human pregnancy-associated glycoprotein-Like family, identified in the genome, of the term placental transcriptome and proteome. RNA-seq allowed the identification of 1364 bp hPAG-L/pep cDNA with at least 56.5% homology with other aspartic proteinases (APs). In silico analyses revealed 388 amino acids (aa) of full-length hPAG-L polypeptide precursor, with 15 aa-signal peptide, 47 aa-blocking peptide and 326 aa-mature protein, and two Asp residues (D), specific for a catalytic cleft of the APs (VVFDTGSSNLWV91-102 and AIVDTGTSLLTG274-285). Capillary sequencing identified 9330 bp of the hPAG-L gene (Gen Bank Acc. No. KX533473), composed of nine exons and eight introns. Heterologous Western blotting revealed the presence of one dominant 60 kDa isoform of the hPAG-L amongst cellular placental proteins. Detection with anti-pPAG-P and anti-Rec pPAG2 polyclonals allowed identification of the hPAG-L proteins located within regions of chorionic villi, especially within the syncytiotrophoblast of term singleton placentas. Our novel data extend the present knowledge about the human genome, as well as placental transcriptome and proteome during term pregnancy. Presumably, this may contribute to establishing a new diagnostic tool for examination of some disturbances during human pregnancy, as well as growing interest from both scientific and clinical perspectives.

Placental PAGs: gene origins, expression patterns, and use as markers of pregnancy

Pregnancy-associated glycoproteins (PAGs) are abundantly expressed products of the placenta of species within the Cetartiodactyla order (even-toed ungulates). They are restricted to this order and they are particularly numerous in the Bovidae. The PAGs exhibit a range of temporal and spatial expression patterns by the placental trophoblasts and probably represent a group of related proteins that perform a range of distinct functions in the epitheliochorial and synepitheliochorial placental forms. This review presents an overview of the origins of the PAGs, a summary of PAG expression patterns, and their use as markers of pregnancy status. Speculations about their putative role(s) in pregnancy are also presented.

Expression of pregnancy-associated glycoprotein family in the epitheliochorial placenta of two Camelidae species (C. dromedarius and C. bactrianus)

This study describes placental morphology and immunolocalization of the placental pregnancy associated glycoprotein-like family (PAGs) identified in two selected taxa of Old-World camels of the Camelidae family: Camelus dromedarius (Cd) and Camelus bactrianus (Cb). Placental tissues of Cd from days 140-293 post-coitum (dpc), term (404 dpc); and of Cb from term (440 dpc) were examined. Histological staining (hematoxylin/eosin and propidium iodine) revealed the development of the placental structure, while chorionic folding increased the feto-placental surface during the progress of pregnancy. The camelid placenta during early pregnancy is similar to the diffuse epitheliochorial type, and during later stages of pregnancy resembles the synepitheliochorial (cotyledonary) type. Placental expression of the PAGs was detected (Alexa 488 - green) within camelid trophectoderm cells (TRD - chorionic epithelium as outer layer of embryonic cells) among all placental cells with nuclei stained by propidium iodide (red). The PAGs, identified in both Camelidae taxa, were named CbPAGs and CdPAGs. Placental CbPAG and CdPAG expression is restricted to the TRD cells, which are differentially developed throughout gestation. Cross-reactivity of polyvalent anti-pPAG polyclonals with the CbPAGs and CdPAGs revealed high structural similarities of the PAG-like epitopes in pigs and camels. This is the first study identifying PAG expression in chorionic cells of the camel placenta.