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

Molecular Mechanism Involved in Carotenoid Metabolism in Post-Smolt Atlantic Salmon: Astaxanthin Metabolism During Flesh Pigmentation and Its Antioxidant Properties

A better understanding of carotenoid dynamics (transport, absorption, metabolism, and deposition) is essential to develop a better strategy to improve astaxanthin (Ax) retention in muscle of Atlantic salmon. To achieve that, a comparison of post-smolt salmon with (+ Ax) or without (- Ax) dietary Ax supplementation was established based on a transcriptomic approach targeting pyloric, hepatic, and muscular tissues. Results in post-smolts showed that the pyloric caeca transcriptome is more sensitive to dietary Ax supplementation compared to the other tissues. Key genes sensitive to Ax supplementation could be identified, such as cd36 in pylorus, agr2 in liver, or fbp1 in muscle. The most modulated genes in pylorus were related to absorption but also metabolism of Ax. Additionally, genes linked to upstream regulation of the ferroptosis pathway were significantly modulated in liver, evoking the involvement of Ax as an antioxidant in this process. Finally, the muscle seemed to be less impacted by dietary Ax supplementation, except for genes related to actin remodelling and glucose homeostasis. In conclusion, the transcriptome data generated from this study showed that Ax dynamics in Atlantic salmon is characterized by a high metabolism during absorption at pyloric caeca level. In liver, a link with a potential of ferroptosis process appears likely via cellular lipid peroxidation. Our data provide insights into a better understanding of molecular mechanisms involved in dietary Ax supplementation, as well as its beneficial effects in preventing oxidative stress and related inflammation in muscle.

Role of homocysteine metabolism in animal reproduction: A review

Homocysteine (Hcy) is a thiol-containing essential amino acid, important for the growth of cells and tissues. Several hypotheses exist regarding Hcy toxicity in humans; Hcy is involved in protein structural modifications, oxidative stress, and neurotoxicity induction and is therefore associated with several pathological conditions in humans. In veterinary science, knowledge regarding Hcy has increased recently due to several studies; however, many aspects remain undiscovered. Many details remain unknown regarding the effect of Hcy levels on pregnancy and the optimal management of pathological conditions associated with Hcy levels during pregnancy in various species. In this review, we aimed to compile various studies on Hcy metabolism to elucidate its current status in the veterinary field, particularly for ovine, bovine, equine, porcine, canine, and feline species.

Extracellular vesicle mediated intercellular communication at the porcine maternal-fetal interface: A new paradigm for conceptus-endometrial cross-talk

Exosomes and microvesicles are extracellular vesicles released from cells and can contain lipids, miRNAs and proteins that affect cells at distant sites. Recently, microvesicles containing miRNA have been implicated in uterine microenvironment of pigs, a species with unique epitheliochorial (non-invasive) placentation. Here we report a novel role of conceptus-derived exosomes/microvesicles (hereafter referred to as extracellular vesicles; EVs) in embryo-endometrial cross-talk. We also demonstrate the stimulatory effects of EVs (PTr2-Exo) derived from porcine trophectoderm-cells on various biological processes including the proliferation of maternal endothelial cells (PAOEC), potentially promoting angiogenesis. Transmission immuno-electron microscopy confirmed the presence of EVs in tissue biopsies, PTr2-Exo and PAOEC-derived EVs (PAOEC-Exo). RT-PCR detected 14 select miRNAs in CD63 positive EVs in which miR-126-5P, miR-296-5P, miR-16, and miR-17-5P were the most abundant angiogenic miRNAs. Proteomic analysis revealed EV proteins that play a role in angiogenesis. In-vitro experiments, using two representative cell lines of maternal-fetal interface, demonstrated bidirectional EVs shuttling between PTr2 and PAOEC cells. Importantly, these studies support the idea that PTr2-Exo and PAOEC-Exo containing select miRNAs and proteins can be successfully delivered to recipient cells and that they may have a biological role in conceptus-endometrial cross-talk crucial for the pregnancy success.

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.

Proteome Differences in Placenta and Endometrium between Normal and Intrauterine Growth Restricted Pig Fetuses

Uteroplacental tissue plays a key role in substance exchanges between maternal and fetal circulation, and, therefore, in the growth and development of fetuses. In this study, proteomics and western blotting were applied to investigate the changes of proteome in the placenta and endometrium of normal and intrauterine growth restriction (IUGR) porcine fetuses during mid to late pregnancy (D60, 90, and 110 of gestation). Our results showed that proteins participating in cell structure, energy metabolism, stress response, cell turnover, as well as transport and metabolism of nutrients were differentially expressed in placenta and endometrium between normal and IUGR fetuses. Analysis of functions of these proteins suggests reductions in ATP production and nutrients transport, increases in oxidative stress and apoptosis, and impairment of cell metabolism in IUGR fetuses. Collectively, our findings aid in understanding of the mechanisms responsible for uteroplacental dysfunction in IUGR fetus, and are expected to provide new strategies to reduce fetal growth restriction in pigs and other mammals.

Embryonic phenotype, β-carotene and retinoid metabolism upon maternal supplementation of β-carotene in a mouse model of severe vitamin A deficiency

We investigated the effect of β-carotene (bC) supplementation during pregnancy in a mouse model of severe vitamin A deficiency, i.e. Lrat-/-Rbp-/- dams maintained on a vitamin A-deficient diet during gestation. bC, a provitamin A carotenoid, can be enzymatically cleaved to form vitamin A for use by the developing embryo. We found that an acute supplementation (13.5 days post coitum, dpc) of bC to Lrat-/-Rbp-/- dams on a vitamin A-deficient diet activated transcriptional mechanisms in the developing tissues to maximize the utilization of bC provided to the dams. Nevertheless, these regulatory mechanisms are inefficient under this regimen, as the embryonic phenotype was not improved. We further investigated the effect of a repeated supplementation of bC during a crucial developmental period (6.5-9.5 dpc) on the above-mentioned mouse model. This treatment improved the embryonic abnormalities, as 40% of the embryos showed a normal phenotype. In addition, analysis of retinoic acid-responsive genes, such as Cyp26a1 in these embryos suggests that bC cleavage results in the production of retinoic acid which then can be used by the embryo. Taken together, these in vivo studies show that bC can be used as a source of vitamin A for severely vitamin A-deficient mammalian embryos.

Influence of the antiandrogen flutamide on the androgen receptor gene expression in the placenta and umbilical cord during pregnancy in the pig

The aim of this study was to determine the immunolocalization and expression of the androgen receptor (AR) in the pig placenta and umbilical cord during pregnancy following exposure to flutamide, a non-steroidal antiandrogen, at its various stages. Pregnant pigs were injected with flutamide at a daily dose of 50mg/kg body weight at different stages of pregnancy: from day 83-89 (n=2); from day 101-107 (n=2). They were sacrificed and tissues collected one day after the last injection. Control animals, two for each experimental point, were injected only with the vehicle (corn oil). Collected tissue samples were fixed for immunohistochemistry or frozen for protein isolation. AR protein was detected in the nucleus of trophoblast cells forming the structure of ridges and in maternal endothelial cells, which are involved in the placental barrier formation. It was also localized in the nuclei of cells forming umbilical cord components: allantoic duct epithelium, amniotic epithelium, Wharton's jelly and the muscular layer of the umbilical cord vein and arteries. Relative optical density analysis showed increased expression in the material derived from animals treated with flutamide. The presence of AR in the placental barrier and in the umbilical cord components suggests a role of androgen in those temporary organs. Flutamide could impact on the levels of the AR protein in the reproductive tracts during pregnancy in sows.

Hypoglycemia, hyperglucagonemia, and fetoplacental defects in glucagon receptor knockout mice: a role for glucagon action in pregnancy maintenance

Alterations in insulin signaling as well as insulin action predispose to infertility as well as adverse pregnancy outcomes; however, little is known about the role of glucagon signaling in reproduction. The glucagon receptor knockout (Gcgr(-/-)) mouse created by our laboratory was used to define the role of glucagon signaling in maintaining normal reproduction. In this mouse model, lack of glucagon signaling did not alter the hypothalamic-pituitary-ovarian axis. Pregnant Gcgr(-/-) female mice displayed persistent hypoglycemia and hyperglucagonemia. Gcgr(-/-) pregnancies were associated with decreased fetal weight, increased late-gestation fetal demise, and significant abnormalities of placentation. Gcgr(-/-) placentas contained areas of extensive mineralization, fibrinoid necrosis, narrowing of the vascular channels, and a thickened interstitium associated with trophoblast hyperplasia. Absent glucagon signaling did not alter glycogen content in Gcgr(-/-) placentas but significantly downregulated genes that control growth, adrenergic signaling, vascularization, oxidative stress, and G protein-coupled receptors. Our data suggest that, similarly to insulin, glucagon action contributes to normal female reproductive function.

In utero cell transfer between porcine littermates

Trafficking of cells between mother and fetus during the course of normal pregnancy is well documented. Similarly, cells are known to travel between twins that share either a placenta (i.e. monozygotic) or associated chorion (i.e. monochorionic). Transferred cells are thought to be channelled via the vessels of the placenta or vascular connections established via the chorion and the long-term presence of these cells (i.e. microchimerism) can have important consequences for immune system function and reparative capacity of the host. Whether cells can be transferred between twins with separate placentas and separate chorions (i.e. no vascular connections between placentas) has not been investigated nor have the biological consequences of such a transfer. In the present study, we tested the possibility of this type of cell transfer by injecting human cord blood-derived cells into a portion of the littermates of swine and probing for human cells in the blood and tissues of unmanipulated littermates. Human cells were detected in the blood of 78% of unmanipulated littermates. Human cells were also detected in various tissues of the unmanipulated littermates, including kidney (56%), spleen (33%), thymus (11%) and heart (22%). Human cells were maintained in the blood until the piglets were sacrificed (8 months after birth), suggesting the establishment of long-term microchimerism. Our findings show that the transfer of cells between fetuses with separate placentas and separate chorions is significant and thus such twins may be subject to the same consequences of microchimerism as monozygotic or monochorionic counterparts.

Metabolism of retinol during mammalian placental and embryonic development

Retinol (vitamin A) is a fat-soluble nutrient indispensable for a harmonious mammalian gestation. The absence or excess of retinol and its active derivatives [i.e., the retinoic acids (RAs)] can lead to abnormal development of embryonic and extraembryonic (placental) structures. The embryo is unable to synthesize the retinol and is strongly dependent on the maternal delivery of retinol itself or precursors: retinyl esters or carotenoids. Before reaching the embryonic tissue, the retinol or the precursors have to pass through the placental structures. During this placental step, a simple diffusion of retinol can occur between maternal and fetal compartments; but retinol can also be used in situ after its activation into RA(1) or stored as retinyl esters. Using retinol-binding protein knockout model, an alternative way of embryonic retinol supply was described using retinyl esters incorporated into maternal chylomicrons. In the embryo, the principal metabolic event occurring for retinol is its conversion into RAs, the active molecules implicated on the molecular control of embryonic morphogenesis and organogenesis. All these placental and embryonic events of retinol transport and metabolism are highly regulated. Nevertheless, some genetic and/or environmental abnormalities in the transport and/or metabolism of retinol can be related to developmental pathologies during mammalian development.

Ultrastructure of the chorioallantoic placenta and chorionic vesicles of the lesser bush baby (Galago senegalensis)

The ultrastructure of the chorioallantoic placenta of the lesser bush baby (Galago senegalensis) has been studied. The placenta was shown to be of the diffuse, epitheliochorial and adeciduate type. The trophoblasts of the chorionic villi, other than those lining the chorionic vesicles, were characterized by the presence of many lipid droplets. In the later stage of gestation, the fetal capillaries indented the trophoblastic epithelium reducing the distance between fetal and maternal circulations. In addition chorionic vesicles were observed. The trophoblasts lining the chorionic vesicles have outward bulging apical surfaces. There are clefts between these cells and this region is occupied by microvilli of adjacent cells. Several layers of fusiform cells that did not extend up into the cores of the chorionic vesicle villi formed the outer component of the vesicular wall. Granulated cells were observed within the maternal connective tissue and their possible role is discussed.

Maternal reproductive hormone levels after repeated ACTH application to pregnant gilts

Prenatal stress has been seen as a reason for reproductive failures in pig offspring mostly originated or mediated by changed maternal functions. In pregnant gilts, three experiments (EXP I-III) were conducted to characterize the effects of repeated ACTH on maternal cortisol concentrations (EXP I) and on the secretion of maternal reproductive hormones (LH, progesterone, estrone sulfate; EXP II + III). Exogenous ACTH was given six times every alternate day beginning either on day 49 (EXP I + II) or day 28 (EXP III) of pregnancy. As a result of treatment, elevated cortisol levels were observed for more than 6 h (EXP I). Plasma concentrations of LH were at low basal level (0.1-0.2 ng/ml), but showed a pulsatory release pattern both during first and second trimester of pregnancy. The number of LH pulses/6 h (L.S.M. +/- S.E.) of saline treated controls increased with ongoing pregnancy (1.4 +/- 0.1 versus 2.0 +/- 0.2 in EXP III and EXP II, respectively). After ACTH treatment the number of LH pulses did not differ between the two gestational stages (1.3 +/- 0.2 and 1.4 +/- 0.2 in EXP III and EXP II, respectively). However, differences ( P < 0.05) were obtained comparing the LH pulse number of ACTH and saline treated sows during the second trimester of pregnancy. Moreover, areas under the curve (AUC) of each LH pulse and of all LH values over the baseline were significantly reduced by treatment. The levels of progesterone increased (P < 0.05) for 150-170 min after each ACTH application both in EXP II and EXP III. The concentrations of 17alpha-hydroxy-progesterone revealed likewise a significant elevation after each ACTH injection. Throughout EXP III, estrone sulfate concentrations were found to decrease (from 2.8-16.9 ng/ml on day 28 to 0.02-0.04 ng/ml on day 38) but without differences between ACTH-and saline-treated gilts. Further data of EXP II and EXP III, e.g. number of piglets born alive, confirmed the absence of detrimental treatment effects. Thus, repeated ACTH administration with subsequent release of cortisol is able to influence the release pattern of maternal reproductive hormones. However, these findings demonstrate that stress-related effects are dependent on the stage of pregnancy. The detected changes may affect feto-maternal interactions and, as a result, fetal reproductive development.

Effects of folic acid and vitamin B12 supplements on folate and homocysteine metabolism in pigs during early pregnancy

The present experiment aimed to determine the effects of supplements of folic acid (FA) alone or in combination with vitamin B12 on folate and homocysteine metabolism in gestating nulliparous Yorkshire-Landrace (YL) and multiparous Landrace (LD) occidental sows and multiparous Chinese Meishan-Landrace (ML) sows. LD sows were randomly assigned to two treatments: 0 or 15 mg FA/kg diet while YL and ML sows were assigned to three treatments: 0 mg FA/kg diet, 15 mg FA/kg or 15 mg vitamin B12/kg diet. Supplements were given from the oestrus preceding insemination up to slaughter on day 15 of gestation. At slaughter, a uterine flush was collected to determine uterine contents of homocysteine, methionine, tetrahydrofolate (THF), 5-methyl-THF, pyridoxal 5-phosphate (P5P) and vitamin B12. Blood samples were taken at first oestrus, at insemination and on days 5, 10 and 15 of gestation to determine plasma concentrations of homocysteine, methionine, THF, 5-methyl-THF, P5P, vitamin B12 and relative total folate-binding capacity. In occidental sows (YL and LD), the FA supplement tended to decrease uterine flush content of homocysteine (P=0.06) and concentrations of plasma homocysteine (P=0.09). Nulliparous YL sows had lower concentrations of plasma homocysteine, methionine, THF and 5-methyl-THF (P<0.05) than multiparous LD sows. Multiparous ML and LD sows had similar concentrations of plasma THF, 5-methyl-THF, methionine and vitamin B12, but ML sows had lower concentrations of plasma homocysteine (P<0.05). The vitamin B12 supplement increased concentrations of plasma vitamin B12 (P<0.05) both in multiparous ML and nulliparous YL sows, but had no effect on the composition of either uterine flush or plasma. The present results showed also that sows had a low vitamin B12 status (<200 pg/ml) and high circulating homocysteine levels (>15 microm) during the first 15 d of gestation. Furthermore, the vitamin B12 content in uterine secretions represented between 180 and 300 % of the total content in plasma. The low plasma concentrations of homocysteine in multiparous ML sows suggest a more efficient remethylation pathway which may not be dependent upon dietary supply of FA or vitamin B12. In nulliparous YL sows, low concentrations of both homocysteine and methionine suggest that the methionine requirement for protein deposition might have reduced the amount of methionine available for the methylation pathway. The results of the present experiment suggest that the reduction of uterine homocysteine may be an important aspect of the role of FA supplement on the uterine environment in occidental sows. The presence of high levels of vitamin B12 in uterine secretions merits further investigation in relation to embryonic development.