Placental transport and distribution of uteroferrin in the fetal pig

Metabolic pathways utilized by the porcine conceptus, uterus, and placenta

Conceptus elongation and early placentation involve growth and remodeling that requires proliferation and migration of cells. This demands conceptuses expend energy before establishment of a placenta connection and when they are dependent upon components of histotroph secreted or transported into the uterine lumen from the uterus. Glucose and fructose, as well as many amino acids (including arginine, aspartate, glutamine, glutamate, glycine, methionine, and serine), increase in the uterine lumen during the peri-implantation period. Glucose and fructose enter cells via their transporters, SLC2A, SLC2A3, and SLC2A8, and amino acids enter the cells via specific transporters that are expressed by the conceptus trophectoderm. However, porcine conceptuses develop rapidly through extensive cellular proliferation and migration as they elongate and attach to the uterine wall resulting in increased metabolic demands. Therefore, coordination of multiple metabolic biosynthetic pathways is an essential aspect of conceptus development. Oxidative metabolism primarily occurs through the tricarboxylic acid (TCA) cycle and the electron transport chain, but proliferating and migrating cells, like the trophectoderm of pigs, enhance aerobic glycolysis. The glycolytic intermediates from glucose can then be shunted into the pentose phosphate pathway and one-carbon metabolism for the de novo synthesis of nucleotides. A result of aerobic glycolysis is limited availability of pyruvate for maintaining the TCA cycle, and trophectoderm cells likely replenish TCA cycle metabolites primarily through glutaminolysis to convert glutamine into TCA cycle intermediates. The synthesis of ATP, nucleotides, amino acids, and fatty acids through these biosynthetic pathways is essential to support elongation, migration, hormone synthesis, implantation, and early placental development of conceptuses.

Generation of Trophoblast-Like Cells From Hypomethylated Porcine Adult Dermal Fibroblasts

The first differentiation event in mammalian embryos is the formation of the trophectoderm, which is the progenitor of the outer epithelial components of the placenta, and which supports the fetus during the intrauterine life. However, the epigenetic and paracrine controls at work in trophectoderm differentiation are still to be fully elucidated and the creation of dedicated in vitro models is desirable to increase our understanding. Here we propose a novel approach based on the epigenetic conversion of adult dermal fibroblasts into trophoblast-like cells. The method combines the use of epigenetic erasing with an ad hoc differentiation protocol. Dermal fibroblasts are erased with 5-azacytidine (5-aza-CR) that confers cells a transient high plasticity state. They are then readdressed toward the trophoblast (TR) phenotype, using MEF conditioned medium, supplemented with bone morphogenetic protein 4 (BMP4) and inhibitors of the Activin/Nodal and FGF2 signaling pathways in low O₂ conditions. The method here described allows the generation of TR-like cells from easily accessible material, such as dermal fibroblasts, that are very simply propagated in vitro. Furthermore, the strategy proposed is free of genetic modifications that make cells prone to instability and transformation. The TR model obtained may also find useful application in order to better characterize embryo implantation mechanisms and developmental disorders based on TR defects.

Exaptation of Retroviral Syncytin for Development of Syncytialized Placenta, Its Limited Homology to the SARS-CoV-2 Spike Protein and Arguments against Disturbing Narrative in the Context of COVID-19 Vaccination

Simple Summary

The anti-vaccination movement claims an alleged danger of the COVID-19 vaccine based on the presupposed similarity between syncytin, which plays a role in human placentation and the SARS-CoV-2 spike protein. We argue that because of very low sequence similarity between human syncytin-1 and the SARS-CoV-2 S protein, it is unlikely that any S protein-specific SARS-CoV-2 vaccine would generate an immune response which would affect fertility and pregnancy. However, further evaluation of potential impacts of COVID-19 vaccines on fertility, placentation, pregnancy and general health of mother and newborn is required.

Abstract

Human placenta formation relies on the interaction between fused trophoblast cells of the embryo with uterine endometrium. The fusion between trophoblast cells, first into cytotrophoblast and then into syncytiotrophoblast, is facilitated by the fusogenic protein syncytin. Syncytin derives from an envelope glycoprotein (ENV) of retroviral origin. In exogenous retroviruses, the envelope glycoproteins coded by env genes allow fusion of the viral envelope with the host cell membrane and entry of the virus into a host cell. During mammalian evolution, the env genes have been repeatedly, and independently, captured by various mammalian species to facilitate the formation of the placenta. Such a shift in the function of a gene, or a trait, for a different purpose during evolution is called an exaptation (co-option). We discuss the structure and origin of the placenta, the fusogenic and non-fusogenic functions of syncytin, and the mechanism of cell fusion. We also comment on an alleged danger of the COVID-19 vaccine based on the presupposed similarity between syncytin and the SARS-CoV-2 spike protein.

The Early Stages of Implantation and Placentation in the Pig

Pregnancy in pigs includes the events of conceptus (embryo/fetus and placental membranes) elongation, implantation, and placentation. Placentation in pigs is defined microscopically as epitheliochorial and macroscopically as diffuse. In general, placentation can be defined as the juxtapositioning of the endometrial/uterine microvasculature to the chorioallantoic/placental microvasculature to facilitate the transport of nutrients from the mother to the fetus to support fetal development and growth. Establishment of epitheliochorial placentation in the pig is achieved by: (1) the secretions of uterine glands prior to conceptus attachment to the uterus; (2) the development of extensive folding of the uterine-placental interface to maximize the surface area for movement of nutrients across this surface; (3) increased angiogenesis of the vasculature that delivers both uterine and placental blood and, with it, nutrients to this interface; (4) the minimization of connective tissue that lies between these blood vessels and the uterine and placental epithelia; (5) interdigitation of microvilli between the uterine and placental epithelia; and (6) the secretions of the uterine glands, called histotroph, that accumulate in areolae for transport though the placenta to the fetus. Placentation in pigs is not achieved by invasive growth of the placenta into the uterus. In this chapter, we summarize current knowledge about the major events that occur during the early stages of implantation and placentation in the pig. We will focus on the microanatomy of porcine placentation that builds off the excellent histological work of Amoroso and others and provide a brief review of some of the key physiological, cellular, and molecular events that accompany the development of "implantation" in pigs.

Effects of increasing Fe dosage in newborn pigs on suckling and subsequent nursery performance and hematological and immunological criteria

A total of 336 newborn pigs (DNA 241 × 600, initially 1.75 ± 0.05 kg bodyweight [BW]) from 28 litters were used in a 63-d study evaluating the effects of increasing injectable Fe dose on suckling and subsequent nursery pig performance and blood Fe status. GleptoForte (Ceva Animal Health, LLC, Lenexa, KS) contains gleptoferron which is an Fe macromolecule complex that is commercially used as an injectable Fe source for suckling piglets. On the day of processing (day 3 after birth), all piglets were weighed and 6 barrows and 6 gilts per litter were allotted within sex to 1 of 6 treatments in a completely randomized design. Treatments consisted of a negative control receiving no Fe injection and increasing injectable Fe to achieve either 50, 100, 150, 200 mg, or 200 mg plus a 100 mg injection on day 11 after birth. Pigs were weaned (~21 d of age) and allotted to nursery pens based on BW and corresponding treatment in a completely randomized design. During lactation, increasing injectable Fe up to 100 mg improved (quadratic; P < 0.05) average daily gain (ADG) and day 21 BW with no further improvement thereafter. There was no evidence of differences (P > 0.10) observed between the 200 mg and 200 mg + 100 mg treatments for growth. For the nursery period, increasing Fe dosage increased (linear; P < 0.05) ADG, average daily feed intake, and day 42 BW. There was no evidence of differences (P > 0.10) between the 200 mg and 200 mg + 100 mg treatments for nursery growth. For blood criteria, significant treatment × day interactions (P = 0.001) were observed for hemoglobin (Hb) and hematocrit (Hct). The interactions occurred because pigs that had <150 mg of injectable Fe had decreased values to day 21 and then increased to day 63 while pigs with 150 or 200 mg of injectable Fe had increased values to day 21 then stayed relatively constant to day 63. In summary, piglet performance during lactation was maximized at 100 mg while nursery growth performance and blood Fe status were maximized with a 200 mg Fe injection at processing. Providing an additional 100 mg of Fe on day 11 of age increased Hb, and Hct values at weaning and 14 d into the nursery but did not provide a growth performance benefit in lactation or nursery. These results indicate that providing 200 mg of injectable Fe provided from GleptoForte is sufficient to optimize lactation and subsequent nursery growth performance and blood Fe status.

Steroids Regulate SLC2A1 and SLC2A3 to Deliver Glucose Into Trophectoderm for Metabolism via Glycolysis

The conceptuses (embryo/fetus and placental membranes) of pigs require energy to support elongation and implantation, and amounts of glucose and fructose increase in the uterine lumen during the peri-implantation period. Conceptuses from day 16 of pregnancy were incubated with either 14C-glucose or 14C-fructose and amounts of radiolabeled CO2 released from the conceptuses measured to determine rates of oxidation of glucose and fructose. Glucose and fructose both transport into conceptuses, and glucose is preferentially metabolized in the presence of fructose, whereas fructose is actively metabolized in the absence of glucose and to a lesser extent in the presence of glucose. Endometrial and placental expression of glucose transporters SLC2A1, SLC2A2, SCL2A3, and SLC2A4 were determined. SLC2A1 messenger RNA (mRNA) and protein, and SLC2A4 mRNA were abundant in the uterine luminal epithelium of pregnant compared to cycling gilts, and increased in response to progesterone and conceptus-secreted estrogen. SLC2A2 mRNA was expressed weakly by conceptus trophectoderm on day 15 of pregnancy, whereas SLC2A3 mRNA was abundant in trophectoderm/chorion throughout pregnancy. Therefore, glucose can be transported into the uterine lumen by SLC2A1, and then into conceptuses by SLC2A3. On day 60 of gestation, the cell-specific expression of these transporters was more complex, suggesting that glucose and fructose transporters are precisely regulated in a spatial-temporal pattern along the uterine-placental interface of pigs to maximize hexose sugar transport to the pig conceptus/placenta.

HAI-1 regulates placental folds development by influencing trophoblast cell proliferation and invasion in pigs

Fetal development is critically dependent on the efficiency of the placenta. Porcine trophoblast cell proliferation and invasion have crucial roles in placental fold development, which is one of the essential events determining placental efficiency. The membrane serine proteinase inhibitor hepatocyte growth factor activator inhibitor-1 (HAI-1) can regulate cellular invasion and motility in different types of epithelial cells, including trophoblast cells in mice. This work used quantitative polymerase chain reaction (qPCR) and immunohistochemistry to compare the expression level and location of HAI-1 in the placenta on gestational days 26, 50, and 95 in Yorkshire and Meishan pigs. The role of HAI-1 in porcine trophoblast cell (PTr2) proliferation, invasion, and migration in vitro was investigated by analyzing the effects of HAI-1 gene silencing or overexpression. Polymorphism in the HAI-1gene was detected to determine associations between the genotype and piglet birth weight in 400 healthy pure-bred Yorkshire piglets. qPCR results showed that HAI-1 mRNA levels significantly increased (P < 0.01) between gestational days 26 and 50 and then decreased (P < 0.01) between days 50 and 95 in both Meishan and Yorkshire pigs. Immunohistochemical analysis showed that HAI-1 protein was strongly expressed by the high columnar trophoblast cells located at the top of the placental folds with low proliferative and invasion capacities. However, it was expressed at very low levels in cuboidal trophoblast cells located at the side and base of the placental folds with high proliferative and invasion capacities. In vitro experiments indicated that HAI-1 had the ability to reduce the proliferation, invasion and migration of trophoblast cells. In addition, one single-nucleotide polymorphism (SNP) of HAI-1 showed a significant association (P < 0.05) with piglet birth weight. These results revealed that HAI-1 could be a vital molecule in placental folds development by regulating trophoblast proliferation and invasion in pigs.

Development and Function of Uterine Glands in Domestic Animals

All mammalian uteri contain glands that synthesize or transport and secrete substances into the uterine lumen. Uterine gland development, or adenogenesis, is uniquely a postnatal event in sheep and pigs and involves differentiation of glandular epithelium from luminal epithelium, followed by invagination and coiling morphogenesis throughout the stroma. Intrinsic transcription factors and extrinsic factors from the ovary and pituitary as well as the mammary gland (lactocrine) regulate uterine adenogenesis. Recurrent pregnancy loss is observed in the ovine uterine gland knockout sheep, providing unequivocal evidence that glands and their products are essential for fertility. Uterine gland hyperplasia and hypertrophy during pregnancy are controlled by sequential actions of hormones from the ovary and/or pituitary as well as the placenta. Gland-derived histotroph is transported by placental areolae for fetal growth. Increased knowledge of uterine gland biology is expected to improve pregnancy outcomes, as well as the health and productivity of mothers and their offspring.

Expression of progesterone receptor in the porcine uterus and placenta throughout gestation: correlation with expression of uteroferrin and osteopontin

Progesterone (P4) stimulates production and secretion of histotroph, a mixture of hormones, growth factors, nutrients, and other substances required for growth and development of the conceptus (embryo or fetus and placental membranes). Progesterone acts through the progesterone receptor (PGR); however, there is a gap in our understanding of P4 during pregnancy because PGR have not been localized in the uteri and placentae of pigs beyond day 18. Therefore, we determined endometrial expression of PGR messenger RNA (mRNA) and localized PGR protein in uterine and placental tissues throughout the estrous cycle and through day 85 of pregnancy in pigs. Further, 2 components of histotroph, tartrate-resistant acid phosphatase 5 (ACP5; uteroferrin) and secreted phosphoprotein 1 (SPP1; osteopontin) proteins, were localized in relation to PGR during pregnancy. Endometrial expression of PGR mRNA was highest at day 5 of the estrous cycle, decreased between days 5 and 11 of both the estrous cycle and pregnancy, and then increased between days 11 and 17 of the estrous cycle (P < 0.01), but decreased from days 13 to 40 of pregnancy (P < 0.01). Progesterone receptor protein localized to uterine stroma and myometrium throughout all days of the estrous cycle and pregnancy. PGR were expressed by uterine luminal epithelium (LE) between days 5 and 11 of the estrous cycle and pregnancy, then PGR became undetectable in LE through day 85 of pregnancy. During the estrous cycle, PGR were downregulated in LE between days 11 and 15, but expression returned to LE on day 17. All uterine glandular epithelial (GE) cells expressed PGR from days 5 to 11 of the estrous cycle and pregnancy, but expression decreased in the superficial GE by day 12. Expression of PGR in GE continued to decrease between days 25 and 85 of pregnancy; however, a few glands near the myometrium and in close proximity to areolae maintained expression of PGR protein. Acid phosphatase 5 protein was detected in the GE from days 12 to 85 of gestation and in areolae. Secreted phosphoprotein 1 protein was detected in uterine LE in apposition to interareolar, but not areolar areas of the chorioallantois on all days examined, and in uterine GE between days 35 and 85 of gestation. Interestingly, uterine GE cells adjacent to areolae expressed PGR, but not ACP5 or SPP1, suggesting these are excretory ducts involved in the passage, but not secretion, of histotroph into the areolar lumen and highlighting that P4 does not stimulate histotroph production in epithelial cells that express PGR.

The evolution of the placenta

The very apt definition of a placenta is coined by Mossman, namely apposition or fusion of the fetal membranes to the uterine mucosa for physiological exchange. As such, it is a specialized organ whose purpose is to provide continuing support to the developing young. By this definition, placentas have evolved within every vertebrate class other than birds. They have evolved on multiple occasions, often within quite narrow taxonomic groups. As the placenta and the maternal system associate more intimately, such that the conceptus relies extensively on maternal support, the relationship leads to increased conflict that drives adaptive changes on both sides. The story of vertebrate placentation, therefore, is one of convergent evolution at both the macromolecular and molecular levels. In this short review, we first describe the emergence of placental-like structures in nonmammalian vertebrates and then transition to mammals themselves. We close the review by discussing the mechanisms that might have favored diversity and hence evolution of the morphology and physiology of the placentas of eutherian mammals.

Difference in expression patterns of placental cholesterol transporters, ABCA1 and SR-BI, in Meishan and Yorkshire pigs with different placental efficiency

Cholesterol is a key cell membrane component and precursor of steroid hormones. The maternal cholesterol is an important exogenous cholesterol source for the developing embryos and its transportation is mediated by ABCA1 and SR-BI. Here we reported that during the peri-implantation period in pigs, ABCA1 was expressed by uterine luminal epithelium (LE) and interestingly, its expression was more abundantly in LE on mesometrial side of uterus. However, SR-BI was expressed primarily by LE, glandular epithelial cells (GE) and trophoblast cells (Tr). During the placentation period, the expression levels of ABCA1 and SR-BI proteins at epithelial bilayer and placental areolae were significantly higher in Chinese Meishan pigs compared to Yorkshire pigs. Consisitently, mRNA levels of HMGCR, the rate-limiting enzyme for cholesterol synthesis, were significantly higher in Meishan placentas than in Yorkshire placentas. Our findings revealed the routes of transplacental cholesterol transport mediated by ABCA1 and SR-BI in pigs and indicated that ABCA1 related pathway may participate in anchoring the conceptus to the mesometrial side of uterus. Additionally, an ABCA1 dependent compensatory mechanism related to the placental efficiency in response to the smaller placenta size in Meishan pigs was suggested.

Placentation, maternal-fetal interface, and conceptus loss in swine

Pregnancy is a delicate yet complex physiological process that requires fine-tuning of many factors (hormones, growth factors, cytokines, and receptors) between the mother and the conceptus to ensure the survival of the conceptus(es) to term. Any disturbance in the maternal-conceptus dialog can have detrimental effects on the affected conceptus or even the outcome of pregnancy as a whole. Being a litter-bearing species, such disruptions can lead to a loss of up to 45% of the totally healthy offspring during early (periattachment) and midgestation to late gestation in pigs. Although the exact mechanism is not entirely understood, several factors have been associated with the fetal loss including but not limited to uterine capacity, placental efficiency, genetics, nutrition, and deficits in vascularization at the maternal-fetal interface. Over the years, we investigated how immune cells are recruited to the porcine maternal-fetal interface and whether they contribute to vascularization. We also delineated how cytokines, chemokines, and cytokine destabilizing factors fine-tune inflammation and whether the cytokine shift from early to midpregnancy exists at the porcine maternal-fetal interface. Finally, we evaluated the role of microRNAs in regulating immune cell recruitment and their angiogenic functions during pregnancy. Collectively our research points out that the immune-angiogenesis axis at the porcine maternal interface is significantly involved in promoting new blood vessel development, regulating inflammatory responses and ultimately contributing to pregnancy success. In this review, we summarized current knowledge on spontaneous fetal loss in swine, with special attention to the mechanisms in immune reactivity and interplay at the maternal-fetal interface.

Structure and functions of the placenta in common minke (Balaenoptera acutorostrata), Bryde's (B. brydei) and sei (B. borealis) whales

The structure and functions of placentas were examined in 3 species of rorqual whales, common minke (Balaenoptera acutorostrata), Bryde's (B. brydei) and sei (B. borealis) whales, with the aim of confirming the structural characteristics of the chorion, including the presence of the areolar part, and clarifying steroidogenic activities and fetomaternal interactions in the placentas of these whales. Placentas were collected from the second phase of the Japanese Whale Research Program under Special Permit in the North Pacific (JARPN II). Histological and ultrastructural examinations revealed that these whale placentas were epitheliochorial placentas with the interdigitation of chorionic villi lined by monolayer uninucleate cells (trophoblast cells) and endometrial crypts as well as folded placentation by fold-like chorionic villi. Moreover, well-developed pouch-like areolae were observed in the placentas, and active absorption was suggested in the chorionic epithelial cells of the areolar part (areolar trophoblast cells). Berlin blue staining showed the presence of ferric ions (Fe(3+)) in the uterine glandular epithelial cells and within the stroma of chorionic villi in the areolar part. An immunohistochemical examination revealed tartrate-resistant acid phosphatase (TRAP; known as uteroferrin in uteri) in the cytoplasm of glandular cells and areolar trophoblast cells. This result suggested that, in cetaceans, uteroferrin is used to supply iron to the fetus. Furthermore, immunoreactivity for P450scc and P450arom was detected in trophoblast cells, but not in areolar trophoblast cells, suggesting that trophoblast cells synthesize estrogen in whale placentas. Therefore, we herein immunohistochemically revealed the localization of aromatase and uteroferrin in cetacean placentas during pregnancy for the first time.

Osteopontin: a leading candidate adhesion molecule for implantation in pigs and sheep

Osteopontin (OPN; also known as Secreted Phosphoprotein 1, SPP1) is a secreted extra-cellular matrix (ECM) protein that binds to a variety of cell surface integrins to stimulate cell-cell and cell-ECM adhesion and communication. It is generally accepted that OPN interacts with apically expressed integrin receptors on the uterine luminal epithelium (LE) and conceptus trophectoderm to attach the conceptus to the uterus for implantation. Research conducted with pigs and sheep has significantly advanced understanding of the role(s) of OPN during implantation through exploitation of the prolonged peri-implantation period of pregnancy when elongating conceptuses are free within the uterine lumen requiring extensive paracrine signaling between conceptus and endometrium. This is followed by a protracted and incremental attachment cascade of trophectoderm to uterine LE during implantation, and development of a true epitheliochorial or synepitheliochorial placenta exhibited by pigs and sheep, respectively. In pigs, implanting conceptuses secrete estrogens which induce the synthesis and secretion of OPN in adjacent uterine LE. OPN then binds to αvβ6 integrin receptors on trophectoderm, and the αvβ3 integrin receptors on uterine LE to bridge conceptus attachment to uterine LE for implantation. In sheep, implanting conceptuses secrete interferon tau that prolongs the lifespan of CL. Progesterone released by CL then induces OPN synthesis and secretion from the endometrial GE into the uterine lumen where OPN binds integrins expressed on trophectoderm (αvβ3) and uterine LE (identity of specific integrins unknown) to adhere the conceptus to the uterus for implantation. OPN binding to the αvβ3 integrin receptor on ovine trophectoderm cells induces in vitro focal adhesion assembly, a prerequisite for adhesion and migration of trophectoderm, through activation of: 1) P70S6K via crosstalk between FRAP1/MTOR and MAPK pathways; 2) MTOR, PI3K, MAPK3/MAPK1 (Erk1/2) and MAPK14 (p38) signaling to stimulate trohectoderm cell migration; and 3) focal adhesion assembly and myosin II motor activity to induce migration of trophectoderm cells. Further large in vivo focal adhesions assemble at the uterine-placental interface of both pigs and sheep and identify the involvement of sizable mechanical forces at this interface during discrete periods of trophoblast migration, attachment and placentation in both species.

Expression of heparanase is associated with breed-specific morphological characters of placental folded bilayer between Yorkshire and Meishan pigs

The pig has a noninvasive epitheliochorial placenta, and trophoblast-endometrial epithelial bilayer development could impact on placental function. This work compared the morphological structures, the cell proliferation status as assessed by Ki67 staining, as well as the location and gene and protein expression of heparanase (HPSE) at the maternal-fetal interface between Yorkshire and Meishan pigs on Days 26, 50, and 95 of gestation. Histomorphometry showed that the widths of placental folds, endometrial stroma, and placental stroma in Meishan pigs were smaller than those in Yorkshire pigs during late gestation, while the complexity and the cell proliferation ability of the folded bilayer were greater in Meishan pigs in this period. The location and expression levels of HPSE mRNA and protein at the maternal-fetal interface were similar between the two breeds during early and midgestation. However, during late gestation, the mRNA and protein levels were higher in Meishan placentae. In addition, the HPSE mRNA was expressed by all the trophoblast cells, and the protein was located both at trophoblast and luminal epithelium cells in Meishan pigs during late gestation, while in Yorkshire pigs, the HPSE mRNA and protein were only identified in trophoblast cells located at the bottom and side of folds. The findings suggest that Meishan pigs may rely more upon the increase in the complexity of the folded bilayer within a reduced placenta to expand the exchange surface area and the HPSE may contribute to the development of the folded bilayer in pigs.

Areolae of the placenta in the Antarctic minke whale (Balaenoptera bonaerensis)

In this study, we examined the existence and structure of areolae and the steroidogenesis of areolar trophoblast cells in the Antarctic minke whale placenta morphologically and immunohistochemically. Placentas were collected from the 15th, 16th and 18th Japanese Whale Research Program under Special Permit in the Antarctic (JARPA) and 1st JARPA II organized by the Institute of Cetacean Research in Tokyo, Japan. The opening and cavity of fetal areolae formed by taller columnar trophoblast cells (areolar trophoblast cells) with long microvilli and a bright cytoplasm, as compared with the trophoblast cells of the chorionic villi interdigitating with the endometrial crypts, were recognized in observations of serial sections. The opening of the areolar cavity was hidden by chorionic villi with areolar trophoblast cells. Furthermore, a closed pouch-like structure lined by tall columnar cells similar to areolar trophoblast cells within the stroma of chorionic villi was noticed and continued to the areolar cavity, with the opening seen on serial sections. In a surface investigation of the chorion and endometrium by SEM, maternal (endometrial) areolae irregularly surrounded by endometrial folds were obvious. Moreover, we distinguished areolar trophoblast cells with long microvilli attached with many blebs from trophoblast cells. In our immunohistochemical observations, a steroidogenic enzyme, cytochrome P450 side chain cleavage enzyme (P450scc), was detected with strong immunoreactivity in trophoblast cells. However, areolar trophoblast cells showed weak or no immunoreactivity for P450scc.

Contributions of an animal scientist to understanding the biology of the uterus and pregnancy

I developed a passion for reproductive biology when taking a course in Physiology of Reproduction at Louisiana State University while preparing to apply for Veterinary School at Texas A&M University. My career path changed. I entered graduate school, obtained a Ph.D. and have enjoyed an academic career conducting research in uterine biology and pregnancy in animal science departments at the University of Florida and at Texas A&M University. My contributions to science include: (1) identification of molecules secreted by or transported by uterine epithelia into the uterine lumen that are critical to successful establishment and maintenance of pregnancy, (2) discovery of steroids and proteins required for pregnancy-recognition signalling and their mechanisms of action in pigs and ruminants, (3) patterns of fetal–placental development and placental transport of nutrients, (4) identification of links between nutrients and components of histotroph that affect fetal–placental development, (5) characterising aspects of the endocrinology of pregnancy and (6) contributing to efforts to exploit the therapeutic value of interferon tau, particularly for treatment of autoimmune and inflammatory diseases. Current research focuses on select nutrients in the uterine lumen, specifically amino acids, glucose and fructose, that affect conceptus development, the therapeutic potential for interferon tau, stromal–epithelial cell signalling whereby progesterone and oestrogen act via steroid receptors in uterine stromal cells to stimulate secretion of growth factors (e.g. fibroblast growth factors and hepatocyte growth factor) that regulate uterine epithelial cells and conceptus trophectoderm, and roles of toll-like receptors expressed by uterine epithelia and conceptus trophectoderm in pregnancy.

Evolution of Placental Function in Mammals: The Molecular Basis of Gas and Nutrient Transfer, Hormone Secretion, and Immune Responses

Placenta has a wide range of functions. Some are supported by novel genes that have evolved following gene duplication events while others require acquisition of gene expression by the trophoblast. Although not expressed in the placenta, high-affinity fetal hemoglobins play a key role in placental gas exchange. They evolved following duplications within the beta-globin gene family with convergent evolution occurring in ruminants and primates. In primates there was also an interesting rearrangement of a cassette of genes in relation to an upstream locus control region. Substrate transfer from mother to fetus is maintained by expression of classic sugar and amino acid transporters at the trophoblast microvillous and basal membranes. In contrast, placental peptide hormones have arisen largely by gene duplication, yielding for example chorionic gonadotropins from the luteinizing hormone gene and placental lactogens from the growth hormone and prolactin genes. There has been a remarkable degree of convergent evolution with placental lactogens emerging separately in the ruminant, rodent, and primate lineages and chorionic gonadotropins evolving separately in equids and higher primates. Finally, coevolution in the primate lineage of killer immunoglobulin-like receptors and human leukocyte antigens can be linked to the deep invasion of the uterus by trophoblast that is a characteristic feature of human placentation.

ACP5 (Uteroferrin): phylogeny of an ancient and conserved gene expressed in the endometrium of mammals

Type 5 acid phosphatase (ACP5; also known as tartrate-resistant acid phosphatase or uteroferrin) is a metalloprotein secreted by the endometrial glandular epithelium of pigs, mares, sheep, and water buffalo. In this paper, we describe the phylogenetic distribution of endometrial expression of ACP5 and demonstrate that endometrial expression arose early in evolution (i.e., before divergence of prototherian and therian mammals ~166 million years ago). To determine expression of ACP5 in the pregnant endometrium, RNA was isolated from rhesus, mouse, rat, dog, sheep, cow, horse, armadillo, opossum, and duck-billed platypus. Results from RT-PCR and RNA-Seq experiments confirmed that ACP5 is expressed in all species examined. ACP5 was also demonstrated immunochemically in endometrium of rhesus, marmoset, sheep, cow, goat, and opossum. Alignment of inferred amino acid sequences shows a high conservation of ACP5 throughout speciation, with species-specific differences most extensive in the N-terminal and C-terminal regions of the protein. Analysis by Selecton indicated that most of the sites in ACP5 are undergoing purifying selection, and no sites undergoing positive selection were found. In conclusion, endometrial expression of ACP5 is a common feature in all orders of mammals and has been subjected to purifying selection. Expression of ACP5 in the uterus predates the divergence of therians and prototherians. ACP5 is an evolutionary conserved gene that likely exerts a common function important for pregnancy in mammals using a wide range of reproductive strategies.

Effects of long-term progesterone exposure on porcine uterine gene expression: progesterone alone does not induce secreted phosphoprotein 1 (osteopontin) in glandular epithelium

Pigs experience significant conceptus loss near mid-gestation, correlating with increasing glandular epithelial (GE) development and secretory activity. Secreted phosphoprotein 1 (SPP1, osteopontin) increases in GE between days 30 and 40 of pregnancy and is expressed in the GE of day 90 pseudopregnant pigs, suggesting that progesterone (P4) from corpora lutea is responsible for induction of SPP1 in GE. In this study, pigs were ovariectomized and treated daily with P4to assess effects of 40 days of P4exposure on SPP1, P4receptor (PGR), uteroferrin (ACP5), and fibroblast growth factor 7 (FGF7) expression in porcine endometria.PGRmRNA decreased in pigs injected with P4compared with pigs injected with corn oil (CO), and PGRs were downregulated in the luminal epithelium (LE) and GE.ACP5mRNA increased in pigs injected with P4compared with pigs injected with CO, andACP5was induced in the GE of P4-treated pigs.FGF7mRNA increased in pigs injected with P4compared with pigs injected with CO, andFGF7was induced in the LE and GE of P4-treated pigs.SPP1mRNA was not different between pigs injected with P4compared with pigs injected with CO, and SPP1 was not present in the GE of P4-treated pigs. Therefore, long-term P4, in the absence of ovarian and/or conceptus factors, does not induce SPP1 expression in GE. We hypothesize that a servomechanism involving sequential effects of multiple hormones and cytokines, similar to those for sheep and humans, is required for GE differentiation and function, including the synthesis and secretion of SPP1.

Evolution and function of the uterine serpins (SERPINA14)

Uterine serpins (recently designated as SERPINA14) are hormonally induced proteins secreted in large quantities by the endometrial epithelium during pregnancy. The SERPINA14 proteins belong to the serine proteinase inhibitor (serpin) superfamily, but their apparent lack of inhibitory activity toward serine proteinases suggests that these proteins evolved a different function from the anti-proteinase activity typically found in most members of the serpin superfamily. The gene is present in a limited group of mammals in the Laurasiatheria superorder (ruminants, horses, pigs, dolphins and some carnivores) while being absent in primates, rodents, lagomorphs and marsupials. Thus, the gene is likely to have evolved by gene duplication after divergence of Laurasiatheria and to play an important role in pregnancy. That role may vary between species. In sheep, SERPINA14 probably serves an immunoregulatory role to prevent rejection of the fetal allograft. It is inhibitory to lymphocyte proliferation and natural killer cell function. In the pig, SERPINA14 is involved in iron transport to the fetus by binding to and stabilizing the iron-binding protein uteroferrin. It is possible that SERPINA14 has undergone divergence in function since the original emergence of the gene in a common ancestor of species possessing SERPINA14.

Biology and clinical significance of tartrate-resistant acid phosphatases: new perspectives on an old enzyme

Type 5 tartrate-resistant acid phosphatase (TRAP) has been a clinically relevant biomarker for about 50 years. It has always been a reliable and specific cytochemical marker for hairy cell leukemia and for differentiated cells of monocytic lineage. Only recently has the test for serum TRAP activity been accepted as sensitive and specific enough for clinical use as a marker of osteoclasts and bone resorption. This has come about through steady advances in knowledge about TRAP enzymology, structure, function, and molecular regulation and a consequent appreciation that TRAP isoforms 5a and 5b have very different clinical significance. As a measure of osteoclast number and bone resorption, TRAP 5b has diagnostic and prognostic applications in osteoporosis, cancers with bone metastasis, chronic renal failure, and perhaps other metabolic and pathologic bone diseases. Serum TRAP 5a, on the other hand, has no relationship to bone metabolism but seems instead to be a measure of activated macrophages and chronic inflammation. Exploration of the real clinical usefulness of serum TRAP 5a for diagnosis and disease management in a wide variety of chronic inflammatory diseases is only now beginning. This perspective traces the important basic scientific developments that have led up to the refinement of serum TRAP isoform immunoassays and their validation as biomarkers of disease. Many unanswered questions remain, providing a wealth of opportunity for continued research of this multifaceted enzyme.

The materno-fetal interface in llama (Lama guanicoe glama)

Samples from 9 llamas (28 through 36 weeks of gestation) were collected and fixed in 4% buffered paraformaldehyde (light microscopy) and in 2.5% buffered glutaraldehyde (transmission and scanning electron microscopy). The material was processed in paraplast and slides (5mm) were stained with HE, PAS, Masson-Trichrome, acid phosphatase and Perl's. The uteroferrin was immunolocalized. The results show that llama placenta is chorioallantoic, diffuse, folded and epitheliochorial, and the fetus is covered with an epidermal membrane. The trophoblast cells have variable morphology: cubic, rounded and triangular cells, with cytoplasm containing PAS-positive granules. Binucleated cells with large cytoplasm and rounded nuclei, as well as giant trophoblastic cells with multiple nuclei were also observed. Numerous blood vessels were observed beneath the cells of the uterine epithelium and around the chorionic subdivided branches. Glandular activity was shown by PAS, Perl's, and acid phosphatase positive reactions in the cytoplasm and glandular lumen, and by immunolocalization of the uteroferrin in the glandular epithelium. The uterine glands open in spaces formed by the areoles, which are filled by PAS-positive material. The llama fetus was covered by the epidermal membrane, composed of stratified epithelium, with up to seven layers of mono-, bi- or trinucleated cells. The high level of maternal and fetal vascularization surfaces indicates an intense exchange of substances across both surfaces. The metabolic activity shown in the uterine glands suggests an adaptation of the gestation to the high altitudes of the natural habitat of this species.

Macroscopic and microscopic aspects of collared peccary and white-lipped peccary placenta

This study examines middle and late gestational placentae from 13 Tayassu tajacu (collared peccary) and 3 Tayassu pecari (white-lipped peccary), which are Artiodactyla belonging to the Family Tayassuidae. The chorionic sac of Tayassu species is diffuse and chorioallantoic. These epitheliochorial placentae show no trophoblast invasion into the uterine epithelium and there is interdigitation between fetal and maternal microvilli. Two distinct regions of the fetomaternal interface can be identified: the interareolar and the areolar regions. The uterine epithelium has eosinophilic cytoplasm with dispersed, basophilic and electron-dense granules. Trophoblast cells are irregularly cuboidal on top of the fetal ridges and columnar on troughs, where cells have cytoplasmic vesicles and large basal vacuoles, surrounded by whorls of smooth membranes. Capillaries indent the trophoblast cells forming a placental barrier 3 microm or less thick. The columnar uterine glandular epithelium has a subpopulation of granules staining with Perl's Prussian blue reaction, suggesting iron secretion. In areolar areas, the trophoblast cells show apical microvilli, a basophilic cytoplasm with electron-dense intracellular vacuoles and cisternae. The placenta can therefore be classified as non-deciduate. The ultrastructural aspects of this study reveal features that have not previously been described and extend our knowledge of functions relating to materno-fetal transport in these species.

Expression patterns of purple acid phosphatase genes in Arabidopsis organs and functional analysis of AtPAP23 predominantly transcribed in flower

Purple acid phosphatases (PAPs) are metallo-phosphoesterases. Their expression and function have not been systematically investigated in higher plants. In this work, we compared the transcript levels of 28 Arabidopsis PAP (AtPAP) genes in five Arabidopsis organs. The 28 members, although differed in their expression patterns in vegetative organs, were all transcribed in flower. Furthermore, the transcription of seven members (AtPAPs 6, 11, 14, 19, 23, 24 and 25) occurred predominantly in the flower. To begin dissecting the role of AtPAP genes in flower development, further expression and functional analyses were conducted using AtPAP23. Histochemical staining of transgenic plants expressing AtPAP23 promoter-beta-glucuronidase (GUS) gene construct revealed that AtPAP23 transcription was strong in flower apical meristems, but became restricted to petals and anther filaments in fully developed flower. A GST (glutathione S-transferase) fusion protein of AtPAP23 (GST:AtPAP23) was expressed in bacterial cells, and was found to contain significant amounts of Fe and Mn (whereas the control GST protein contained none). In biochemical tests, GST:AtPAP23 showed typical acid phosphatase activities. The fusion protein was also highly active on phosphoserine, but not phosphotyrosine. Despite its highly specific expression pattern and the demonstrated biochemical function of its protein product, the RNAi (RNA interference), T-DNA knock-out and overexpression lines of AtPAP23 were indistinguishable from wild type plants in the development of flower (or other organs). Interestingly, the Fe and Mn contents were found significantly increased in AtPAP23 overexpression lines, which may offer a new direction for further functional studies of AtPAPs in Arabidopsis.

Porcine purple acid phosphatase: heterologous expression, characterization, and proteolytic analysis

Uteroferrin is an iron-binding glycoprotein, which is abundantly synthesized in porcine uterine glandular endometrium and believed to be involved in maternal/fetal iron transport. In the present study, uteroferrin has been cloned and functionally expressed using baculovirus-infected insect host cells Spodoptera frugiperda. The work also addresses the possible role of proteolytic cleavage to facilitate the release of uteroferrin-bound iron. The enzyme secreted in culture medium exhibits a molecular mass and catalytic properties similar to native porcine uteroferrin. The specific activity was estimated at 233 U/mg using p-nitrophenyl phosphate as substrate. Partial cleavage of the enzyme with trypsin resulted in a 1.7-fold enhancement in specific activity and a two-subunit polypeptide as observed in preparations of most mammalian purple acid phosphatases. Digestion with the aspartic protease pepsin resulted in a 2.5-fold enzyme inactivation correlated with the appearance of low molecular weight polypeptide fragments and the release of enzyme-bound iron.

A structural and immunological study of chorionic gonadotrophin production by equine trophoblast girdle and cup cells

Equine chorionic gonadotropin (eCG) production by the fetally derived endometrial cups appears to be necessary for the establishment and maintenance of normal equine pregnancy. Starting at about the 27th day of pregnancy, an equatorial band of trophectodermal cells on the surface of the spherical conceptus forms the chorionic girdle. This girdle consists initially of flat trophectodermal epithelium which corrugates into folds as the cells proliferate. The folds are then pressed against the uterine epithelium by expansion of the conceptus. The cells on the apices of the folds become binucleate before they start to invade the endometrium at days 35-37. Ultrastructural immunogold labelling shows that they begin to synthesize eCG as early as day 32, before they migrate into and through the maternal epithelium. Clusters of the girdle binucleate cells penetrate deep into the endometrium. The mature cup cell has a cytoplasm full of mitochondria, rough endoplasmic reticulum cisternae, a large Golgi apparatus and a strong immunoreactivity for the glucose transporter 1 isoform on its plasmalemma. Immunocytochemistry also demonstrates that eCG is localized in the Golgi cisternae, and in small dense granules similar to those found in the migrating girdle cell and present both in the Golgi region and at the peripheral plasmalemma. Release of eCG would therefore seem to be by the usual exocytotic mechanism as found for other protein hormones. The small size and absence of any significant accumulation of eCG-containing granules are in marked contrast to the numerous large luteinizing hormone (eLH) containing granules in the equine pituitary gonadotroph, although both hormones, eLH and eCG, show complete identity at the amino acid sequence level. These morphological indicators suggest that the cup cell secretes eCG constitutively (that is, continuously), with no requirement for secretagogues, whereas in the pituitary cell the regulated pathway is utilized capable of massive secretion under appropriate stimulation.

Immunohistochemical localization of retinoid binding proteins at the materno-fetal interface of the porcine epitheliochorial placenta

Retinol and retinoic acid that are potent modulators of gene expression are vital for development and growth of the conceptus. Apart from being transported across the placenta, retinol and retinoic acid may also be active in the placenta per se. Three proteins involved in 1) serum transport of retinol (retinol binding protein [RBP]), 2) cellular transport and metabolism of retinol (cellular RBP [CRBP] I), and 3) retinoic acid (cellular retinoic acid binding protein [CRABP] I), respectively, have been located by immunohistochemistry during gestation in the porcine placenta. This is a diffuse epitheliochorial placenta composed of areolar-gland subunits, where transport of larger molecules takes place, and interareolar regions, where gas-exchange and trophoblast absorption of hemotroph occur. Immunoreactive-RBP (ir-RBP) as well as CRBP I (ir-CRBP) was detected in uterine glands and in areolar trophoblasts, suggesting that RBP-retinol is secreted by the glands and absorbed by the trophoblasts. Both proteins were present also at the interareolar regions, with ir-CRBP in both the uterine epithelium and the apposing trophoblasts, but ir-RBP only in the former. The localization of ir-CRABP was, in contrast, strictly limited to interareolar trophoblasts. Together these findings suggest that 1) the areolar gland subunits are important for transport of retinol and retinol-RBP, and 2) retinoid binding proteins are involved in the development and growth of the porcine placenta.

Separate sites and mechanisms for placental transport of calcium, iron and glucose in the equine placenta

The placenta is the only channel for transport of nutrients to the conceptus and the fetal nutrient demands increase exponentially to term. The 9 kDa calcium binding protein (calbindin, 9CBP) and the iron binding protein uteroferrin (UF) are proving to be reliable markers for epithelia that mediate active transcellular calcium and iron transport and the glucose transporter proteins (GT1 and GT3) for glucose transport by facilitated diffusion. Light and electron microscope immunocytochemistry have been used on perfusion fixed resin embedded material to establish the distribution of 9CBP, UF, GT1 and GT3 in the equine placenta from 100 days of pregnancy to term (336 days). The equine placenta has two main structural components, flat areolae and microcotyledons. From 100 days of pregnancy to term immunoreactive 9CBP is found only in the cytoplasm of the maternal glands and the areolar trophoblast cells with none in the microcotyledons; whereas GT1 is present exclusively in the microcotyledons on the basolateral plasmalemma of both trophoblast and uterine epithelia with GT3 on the apical microvilli. The glands show neither GT1 nor GT3 expression. The areas of both areolae and microcotyledons increase enormously during gestation but there is no indication of increasing amounts of 9CBP, GT1 or GT3 protein per cell. Glucose transport through the placental cell cytoplasm is by diffusion of the free molecule, but calcium ions in transit must be sequestered in some way since the high calcium fluxes needed to support fetal bone growth in later pregnancy would be deleterious to calcium based homeostasis and cellular control systems. Electron microscope immunocytochemistry shows that 9CBP is uniformly distributed in the cytoplasm and nucleoplasm of the areolar trophoblast cells but excluded from all membrane bounded compartments such as mitochondria, Golgi saccules and pinocytotic transport vesicles. Such apical transport vesicles can be identified immunocytochemically by their content of uteroferrin, a component of the secretion from the uterine glands. It is suggested that transcellular calcium transport is therefore based on facilitated diffusion, not the vesicular method followed by the iron in the UF molecules, with 9CBP providing both transfer and sequestration functions for the transient calcium ions. These results show that the equine placenta has transport systems with restricted regional distribution similar to those recently shown for the ruminant placenta.

Zinc, copper, and iron metabolism during porcine fetal development

Zinc, copper, and iron levels in maternal and fetal pig tissues and fluids were measured starting on d 30 of gestation and continuing to term (d 114) at 10-d intervals. Fetal hematocrit increased from a low of 19% on d 30 to 32% by d 50, after which it remained above 30% to term. Amniotic fluid zinc, copper, and iron all reached maximal levels by d 60 of gestation. Maternal serum zinc levels fluctuated little during gestation, but fetal serum zinc concentration was significantly elevated above maternal levels during the second trimester. Fetal serum copper levels were significantly lower than maternal values throughout gestation and this was also the case for ceruloplasmin oxidase activity. Maternal serum iron reached its lowest level by d 80 of gestation when rate of transfer of iron to the developing fetuses was high. Fetal serum iron declined throughout gestation, reaching its lowest level on d 100. In general, fetal liver concentrations of zinc, copper, and iron were higher than the corresponding maternal values throughout gestation. Distinct increases were noted for fetal hepatic zinc and copper concentrations during the second trimester of pregnancy and these were accompanied by increases in cytosolic and metallothionein-bound zinc and copper levels. Maternal hepatic iron declined during the second trimester, reaching its lowest point on d 80, indicative of the shunting of maternal iron reserves to fetal tissues. Fetal kidney metal levels did not demonstrate any distinctive developmental patterns with respect to zinc, copper, or iron concentrations, but a general accumulation of each metal was observed as gestation progressed. The results of this study highlight some of the distinct changes occurring in the metabolism of zinc, copper, and iron in both maternal and fetal tissues and fluids during gestation in the pig.

The effect of uteroferrin and recombinant GM-CSF on hematopoietic parameters in normal female pigs (Sus scrofa)

The present study investigated the effect of uteroferrin and recombinant bovine granulocyte-monocyte/macrophage colony stimulating factor (rbGM-CSF) on hematopoiesis in young female pigs. Uteroferrin (100 micrograms/kg in 0.9% NaCl), rbGM-CSF (10 micrograms/kg in 0.9% NaCl), uteroferrin + rbGM-CSF (as above), or control (0.9% NaCl) were administered as intramuscular injections twice daily (0800 and 2000 hr). Peripheral blood cell number, composition, and progenitor cells were determined over 28 days. Uteroferrin had minimal effects on white blood cell (WBC) number, while rbGM-CSF caused both a rapid (days 2-7; maximum 122 +/- 8% of baseline) and late (days 16-28; maximum 133 +/- 8% of baseline) increase in WBC. Combination treatment with uteroferrin + rbGM-CSF abolished the initial increase in WBC number,but resulted in a prolonged increase in WBC number (days 14-28) relative to control. The rbGM-CSF-induced increase in WBC number resulted from rapid increases (P < 0.05) in monocytes and neutrophils. The addition of uteroferrin + rbGM-CSF enhanced (P < 0.05) the initial increase in the monocyte population and augmented the neutrophilia. In addition, uteroferrin + rbGM-CSF resulted in a dramatic eosinophilia (days 2-28), which was not detected in either the uteroferrin or rbGM-CSF treatments. Although not substantially affected by uteroferrin alone, rbGM-CSF caused an increase (P < 0.05) in thrombocyte numbers from days 1 through 9 (maximum 133 +/- 11% of baseline), an effect augmented by cotreatment with uteroferrin. The ability of these cytokines to modulate blood cell number and composition appeared to result from their effects on hematopoietic progenitor cells. Treatment of pigs with uteroferrin increased (P < 0.05) CFU-GEMM, CFU-GM, and BFU-E progenitor cells in peripheral blood, while rbGM-CSF caused increases (P < 0.05) relative to control in CFU-GM and CFU-GEMM. These effects were additive, as uteroferrin + GM-CSF augmented the increases in CFU-GM, BFU-E, and CFU-GEMM. Collectively, these results indicate that uteroferrin and rbGM-CSF can modulate hematopoiesis in young pigs. These effects were both additive and, in the case of neutrophils and eosinophils, synergistic. Hence, the mechanism(s) by which uteroferrin and rbGM-CSF modulate hematopoiesis appear to be different.

Uteroferrin and recombinant bovine GM-CSF modulate the myelosuppressive effects of 5-fluorouracil in young female pigs (Sus scrofa)

The present study investigated the ability of uteroferrin and recombinant bovine granulocyte monocyte/macrophage-colony stimulating factor (rbGM-CSF) to modulate the myelosuppressive effects of 5-fluorouracil (5-FU) in young female pigs (Sus scrofa). Pigs (N = 3/treatment) were infused with 5-FU (32.5 mg/kg) on days 0 and 1 of the experimental period. Uteroferrin (100 micrograms/kg in 0.9% NaCl), rbGM-CSF (10 micrograms/kg in 0.9% NaCl), uteroferrin + rbGM-CSF (as above) or control (0.9% NaCl) were administered as intramuscular injections twice daily (0800 and 2000 hr). Peripheral blood cell number, composition, and progenitor cells were determined over 28 days. Treatment of pigs with 5-FU resulted in a rapid leukocytopenia and thrombocytopenia (nadirs on days 5 and 7, respectively) and a modest decrease (P < 0.05) in red blood cell (RBC) number (nadir on day 14). Although nor affecting RBC and thrombocytes, treatment of pigs with uteroferrin had an initial protective effect (P < 0.05) on the 5-FU-induced leukocytopenia (63 and 64 vs 48 and 39 +/- 6% of baseline on days 3 and 5, respectively). In contrast, rbGM-CSF enhanced (P < 0.05) the rate of the leukocytopenia and had only minor effects on thrombocyte numbers relative to controls. These effects appeared to be additive, as pigs treated with uteroferrin + rbGM-CSF had a reduced rate of leukocytopenia compared to pigs treated with rbGM-CSF alone. Uteroferrin + rbGM-CSF also attenuated (P < 0.05) the suppression and enhanced (P < 0.05) recovery of RBC and thrombocyte numbers following 5-FU treatment. In control pigs, a modest rebound leukocytosis (122 +/- 6% of baseline) and thrombocytosis (141 +/- 9% of baseline) was evident. Uteroferrin enhanced (P < 0.05) the rebound leukocytosis (135 +/- 6% of baseline), but attenuated (P < 0.05) the thrombocytosis. In contrast, rbGM-CSF enhanced (P < 0.05) the duration of the leukocytosis during the recovery phase, an effect augmented by the combination of uteroferrin + rbGM-CSF. In addition, treatment with uteroferrin + rbGM-CSF resulted in a sustained thrombocytosis (days 12 to 21). As indicated by changes in CFU-GM, BFU-E, and CFU-GEMM progenitor cells in peripheral blood, the effects of uteroferrin and rbGM-CSF appeared to reflect their ability to enhance the proliferation and/or differentiation of both similar and distinct hematopoietic progenitor cells.

Myelosuppression in the pig (Sus scrofa): uteroferrin reduces the myelosuppressive effects of 5-fluorouracil in young pigs

The present study investigated the ability of uteroferrin to modulate the myelosuppressive effects of 5-fluorouracil (5-FU) in young pigs (Sus scrofa). Pigs (28-35 days of age; n = 6 per treatment) were infused with equal amounts of 5-FU on days 0 and 1 of the experimental period (37.5 mg/kg cumulative dose). Uteroferrin (100 micrograms/kg in 0.9% NaCl) or control (equivalent volume of 0.9% NaCl) was administered to pigs as intramuscular injections twice daily (08:00 and 20:00 hr) on days 1 through 21. Peripheral blood cell number, composition and progenitor cells were determined over 28 days. Treatment of pigs with 5-FU resulted in a rapid dose-dependent (P < 0.05) leukocytopenia. Concurrent treatment of pigs with uteroferrin reduced (P < 0.05) the rate of 5-FU-induced leukocytopenia (44 vs 77 +/- 7% decline from baseline on day 3) and enhanced (P < 0.05), the recovery from 5-FU on days 10 and 12 postinfusion. The positive effect of uteroferrin on leukocytes resulted primarily from a protection and/or enhanced recovery of neutrophils and monocytes. In addition, uteroferrin attenuated (P < 0.05) the suppression of red blood cell numbers after 5-FU administration (6.9 vs 6.1 +/- 0.2 x 10(6) cells/microliter on day 3), an affect reflected in increased hematocrit and hemoglobin concentrations. The effects of uteroferrin appeared to result from enhancement of the proliferation and/or differentiation of primitive pluripotent stem cells resistant to 5-FU, as concurrent treatment of pigs with uteroferrin resulted in a protection and/or enhanced recovery (P < 0.05) of CFU-GEMM, CFU-GM and BFU-E progenitor cells in the peripheral blood. These results are the first to demonstrate that uteroferrin can reduce the myelosuppressive effects of 5-FU in the pig and suggest that uteroferrin has hematopoietic growth factor activity in vivo.

Foetal metabolism, placental transfer and origin of gastrin releasing peptide in the sheep

1. Plasma gastrin releasing peptide (GRP) is elevated in the foetal and maternal circulations of pregnant sheep. To determine the mechanisms for this increase the synthesis, secretion rate, metabolism and placental transfer of GRP were measured. 2. Foetal metabolic clearance rate of GRP was significantly increased (P < 0.05) compared to the non-pregnant ewe (19.9 +/- 2.6 (s.e.m.) and 11.8 +/- 2.0 mL/min per kg, respectively). Production rate of GRP in the foetus was four-fold higher than in the non-pregnant ewe reflecting the combination of the increased basal concentration and metabolic clearance rate in the foetus. 3. Infused GRP did not cross the placenta. However, endogenous GRP was higher in the umbilical vein than in the umbilical artery, suggesting a uteroplacental origin for some of the GRP in the foetal circulation. 4. Gastrin releasing peptide mRNA was synthesized in the pregnant endometrium with lower amounts found in the pregnant myometrium. No GRP mRNA was detected in the amnion or chorioallantois. 5. The results show that the previously reported increase in foetal concentration of GRP is from foetal and uteroplacental sources and is not a result of immaturity of clearance mechanisms but rather from an increased production of GRP. With the demonstration that the uteroplacental unit synthesizes and stores GRP, additional studies on the regulation of GRP production from these sources were warranted.

Mammalian bombesin as a hormone in ovine pregnancy: ontogeny, origin, and molecular forms

Mammalian gastrin-releasing peptides (GRP) are present in female reproductive tissues and stimulate uterine contraction and DNA synthesis in the endometrium. We set out to establish whether the GRP were likely to play a role in fetal development by measuring the fetal and maternal plasma concentrations in chronically cannulated fetal sheep from 115 days gestation to term (145 days) and for 18 days after parturition. Placental fluids and fetal urine were also obtained. In a separate series of animals, uterine, placental, and fetal gut and lung tissues were collected. Samples were extracted in acid and assayed by radioimmunoassay, and molecular forms were characterized by high-performance liquid chromatography. GRP were present in the decidua (> 10 pmol/g), as well as placental, uterine, lung, and gastrointestinal tissues (all < 6 pmol/g). Fetal and maternal plasma GRP were elevated compared with nonpregnant ewes, falling sharply after parturition. Placental fluids and urine also contained GRP (80-410 fmol/ml). The main molecular form in all tissues and fluids examined coeluted with porcine GRP-(18-27). GRP immunoreactivity was primarily localized to epithelial cells of the decidua. These data suggest that plasma GRP is probably derived from the decidua and may play a role as a circulating hormone in ovine fetal and uterine development.