Increasing maternal glucose concentrations is insufficient to restore placental glucose transfer in chorionic somatomammotropin RNA interference pregnancies

We previously demonstrated impaired placental nutrient transfer in chorionic somatomammotropin (CSH) RNA interference (RNAi) pregnancies, with glucose transfer being the most impacted. Thus, we hypothesized that despite experimentally elevating maternal glucose, diminished umbilical glucose uptake would persist in CSH RNAi pregnancies, demonstrating the necessity of CSH for adequate placental glucose transfer. Trophectoderm of sheep blastocysts (9 days of gestational age; dGA) were infected with a lentivirus expressing either nontargeting control (CON RNAi; n = 5) or CSH-specific shRNA (CSH RNAi; n = 7) before transfer into recipient sheep. At 126 dGA, pregnancies were fitted with vascular catheters and underwent steady-state metabolic studies (3H2O transplacental diffusion) at 137 ± 0 dGA, before and during a maternal hyperglycemic clamp. Umbilical glucose and oxygen uptakes, as well as insulin and IGF1 concentrations, were impaired (P ≤ 0.01) in CSH RNAi fetuses and were not rescued by elevated maternal glucose. This is partially due to impaired uterine and umbilical blood flow (P ≤ 0.01). However, uteroplacental oxygen utilization was greater (P ≤ 0.05) during the maternal hyperglycemic clamp, consistent with greater placental oxidation of substrates. The relationship between umbilical glucose uptake and the maternal-fetal glucose gradient was analyzed, and while the slope (CON RNAi, Y = 29.54X +74.15; CSH RNAi, Y = 19.05X + 52.40) was not different, the y-intercepts and elevation were (P = 0.003), indicating reduced maximal glucose transport during maternal hyperglycemia. Together, these data suggested that CSH plays a key role in modulating placental metabolism that ultimately promotes maximal placental glucose transfer.NEW & NOTEWORTHY The current study demonstrated a novel, critical autocrine role for chorionic somatomammotropin in augmenting placental glucose transfer and maintaining placental oxidative metabolism. In pregnancies with CSH deficiency, excess glucose in maternal circulation is insufficient to overcome fetal hypoglycemia due to impaired placental glucose transfer and elevated placental metabolic demands. This suggests that perturbations in glucose transfer in CSH RNAi pregnancies are due to compromised metabolic efficiency along with reduced placental mass.

Fetal Hypoglycemia Induced by Placental SLC2A3-RNA Interference Alters Fetal Pancreas Development and Transcriptome at Mid-Gestation

Glucose, the primary energy substrate for fetal oxidative processes and growth, is transferred from maternal to fetal circulation down a concentration gradient by placental facilitative glucose transporters. In sheep, SLC2A1 and SLC2A3 are the primary transporters available in the placental epithelium, with SLC2A3 located on the maternal-facing apical trophoblast membrane and SLC2A1 located on the fetal-facing basolateral trophoblast membrane. We have previously reported that impaired placental SLC2A3 glucose transport resulted in smaller, hypoglycemic fetuses with reduced umbilical artery insulin and glucagon concentrations, in addition to diminished pancreas weights. These findings led us to subject RNA derived from SLC2A3-RNAi (RNA interference) and NTS-RNAi (non-targeting sequence) fetal pancreases to qPCR followed by transcriptomic analysis. We identified a total of 771 differentially expressed genes (DEGs). Upregulated pathways were associated with fat digestion and absorption, particularly fatty acid transport, lipid metabolism, and cholesterol biosynthesis, suggesting a potential switch in energetic substrates due to hypoglycemia. Pathways related to molecular transport and cell signaling in addition to pathways influencing growth and metabolism of the developing pancreas were also impacted. A few genes directly related to gluconeogenesis were also differentially expressed. Our results suggest that fetal hypoglycemia during the first half of gestation impacts fetal pancreas development and function that is not limited to β cell activity.

The Impact of SLC2A8 RNA Interference on Glucose Uptake and the Transcriptome of Human Trophoblast Cells

While glucose is the primary fuel for fetal growth, the placenta utilizes the majority of glucose taken up from the maternal circulation. Of the facilitative glucose transporters in the placenta, SLC2A8 (GLUT8) is thought to primarily function as an intracellular glucose transporter; however, its function in trophoblast cells has not been determined. To gain insight into the function of SLC2A8 in the placenta, lentiviral-mediated RNA interference (RNAi) was performed in the human first-trimester trophoblast cell line ACH-3P. Non-targeting sequence controls (NTS RNAi; n = 4) and SLC2A8 RNAi (n = 4) infected ACH-3P cells were compared. A 79% reduction in SLC2A8 mRNA concentration was associated with an 11% reduction (p ≤ 0.05) in ACH-3P glucose uptake. NTS RNAi and SLC2A8 RNAi ACH-3P mRNA were subjected to RNAseq, identifying 1525 transcripts that were differentially expressed (|log2FC| > 1 and adjusted p-value < 0.05), with 273 transcripts derived from protein-coding genes, and the change in 10 of these mRNAs was validated by real-time qPCR. Additionally, there were 147 differentially expressed long non-coding RNAs. Functional analyses revealed differentially expressed genes involved in various metabolic pathways associated with cellular respiration, oxidative phosphorylation, and ATP synthesis. Collectively, these data indicate that SLC2A8 deficiency may impact placental uptake of glucose, but that its likely primary function in trophoblast cells is to support cellular respiration. Since the placenta oxidizes the majority of the glucose it takes up to support its own metabolic needs, impairment of SLC2A8 function could set the stage for functional placental insufficiency.

Impact of Chorionic Somatomammotropin In Vivo RNA Interference Phenotype on Uteroplacental Expression of the IGF Axis

While fetal growth is dependent on many factors, optimal placental function is a prerequisite for a normal pregnancy outcome. The majority of fetal growth-restricted (FGR) pregnancies result from placental insufficiency (PI). The insulin-like growth factors (IGF1 and IGF2) stimulate fetal growth and placental development and function. Previously, we demonstrated that in vivo RNA interference (RNAi) of the placental hormone, chorionic somatomammotropin (CSH), resulted in two phenotypes. One phenotype exhibits significant placental and fetal growth restriction (PI-FGR), impaired placental nutrient transport, and significant reductions in umbilical insulin and IGF1. The other phenotype does not exhibit statistically significant changes in placental or fetal growth (non-FGR). It was our objective to further characterize these two phenotypes by determining the impact of CSH RNAi on the placental (maternal caruncle and fetal cotyledon) expression of the IGF axis. The trophectoderm of hatched blastocysts (9 days of gestation, dGA) were infected with a lentivirus expressing either a non-targeting sequence (NTS RNAi) control or CSH-specific shRNA (CSH RNAi) prior to embryo transfer into synchronized recipient ewes. At ≈125 dGA, pregnancies were fitted with vascular catheters to undergo steady-state metabolic studies. Nutrient uptakes were determined, and tissues were harvested at necropsy. In both CSH RNAi non-FGR and PI-FGR pregnancies, uterine blood flow was significantly reduced (p ≤ 0.05), while umbilical blood flow (p ≤ 0.01), both uterine and umbilical glucose and oxygen uptakes (p ≤ 0.05), and umbilical concentrations of insulin and IGF1 (p ≤ 0.05) were reduced in CSH RNAi PI-FGR pregnancies. Fetal cotyledon IGF1 mRNA concentration was reduced (p ≤ 0.05) in CSH RNAi PI-FGR pregnancies, whereas neither IGF1 nor IGF2 mRNA concentrations were impacted in the maternal caruncles, and either placental tissue in the non-FGR pregnancies. Fetal cotyledon IGF1R and IGF2R mRNA concentrations were not impacted for either phenotype, yet IGF2R was increased (p ≤ 0.01) in the maternal caruncles of CSH RNAi PI-FGR pregnancies. For the IGF binding proteins (IGFBP1, IGFBP2, IGFBP3), only IGFBP2 mRNA concentrations were impacted, with elevated IGFBP2 mRNA in both the fetal cotyledon (p ≤ 0.01) and maternal caruncle (p = 0.08) of CSH RNAi non-FGR pregnancies. These data support the importance of IGF1 in placental growth and function but may also implicate IGFBP2 in salvaging placental growth in non-FGR pregnancies.

Impact of Placental SLC2A3 Deficiency during the First-Half of Gestation

In the ruminant placenta, glucose uptake and transfer are mediated by facilitative glucose transporters SLC2A1 (GLUT1) and SLC2A3 (GLUT3). SLC2A1 is located on the basolateral trophoblast membrane, whereas SLC2A3 is located solely on the maternal-facing, apical trophoblast membrane. While SLC2A3 is less abundant than SLC2A1, SLC2A3 has a five-fold greater affinity and transport capacity. Based on its location, SLC2A3 likely plays a significant role in the uptake of glucose into the trophoblast. Fetal hypoglycemia is a hallmark of fetal growth restriction (FGR), and as such, any deficiency in SLC2A3 could impact trophoblast glucose uptake and transfer to the fetus, thus potentially setting the stage for FGR. By utilizing in vivo placenta-specific lentiviral-mediated RNA interference (RNAi) in sheep, we were able to significantly diminish (p ≤ 0.05) placental SLC2A3 concentration, and determine the impact at mid-gestation (75 dGA). In response to SLC2A3 RNAi (n = 6), the fetuses were hypoglycemic (p ≤ 0.05), exhibited reduced fetal growth, including reduced fetal pancreas weight (p ≤ 0.05), which was associated with reduced umbilical artery insulin and glucagon concentrations, when compared to the non-targeting sequence (NTS) RNAi controls (n = 6). By contrast, fetal liver weights were not impacted, nor were umbilical artery concentrations of IGF1, possibly resulting from a 70% increase (p ≤ 0.05) in umbilical vein chorionic somatomammotropin (CSH) concentrations. Thus, during the first half of gestation, a deficiency in SLC2A3 results in fetal hypoglycemia, reduced fetal development, and altered metabolic hormone concentrations. These results suggest that SLC2A3 may be the rate-limiting placental glucose transporter during the first-half of gestation in sheep.

Uptake of Phosphate, Calcium, and Vitamin D by the Pregnant Uterus of Sheep in Late Gestation: Regulation by Chorionic Somatomammotropin Hormone

Minerals are required for the establishment and maintenance of pregnancy and regulation of fetal growth in mammals. Lentiviral-mediated RNA interference (RNAi) of chorionic somatomammotropin hormone (CSH) results in both an intrauterine growth restriction (IUGR) and a non-IUGR phenotype in sheep. This study determined the effects of CSH RNAi on the concentration and uptake of calcium, phosphate, and vitamin D, and the expression of candidate mRNAs known to mediate mineral signaling in caruncles (maternal component of placentome) and cotyledons (fetal component of placentome) on gestational day 132. CSH RNAi Non-IUGR pregnancies had a lower umbilical vein−umbilical artery calcium gradient (p < 0.05) and less cotyledonary calcium (p < 0.05) and phosphate (p < 0.05) compared to Control RNAi pregnancies. CSH RNAi IUGR pregnancies had less umbilical calcium uptake (p < 0.05), lower uterine arterial and venous concentrations of 25(OH)D (p < 0.05), and trends for lower umbilical 25(OH)D uptake (p = 0.059) compared to Control RNAi pregnancies. Furthermore, CSH RNAi IUGR pregnancies had decreased umbilical uptake of calcium (p < 0.05), less uterine venous 25(OH)D (vitamin D metabolite; p = 0.055), lower caruncular expression of SLC20A2 (sodium-dependent phosphate transporter; p < 0.05) mRNA, and lower cotyledonary expression of KL (klotho; p < 0.01), FGFR1 (fibroblast growth factor receptor 1; p < 0.05), FGFR2 (p < 0.05), and TRPV6 (transient receptor potential vanilloid member 6; p < 0.05) mRNAs compared to CSH RNAi Non-IUGR pregnancies. This study has provided novel insights into the regulatory role of CSH for calcium, phosphate, and vitamin D utilization in late gestation.

In vivo investigation of ruminant placenta function and physiology-a review

The placenta facilitates the transport of nutrients to the fetus, removal of waste products from the fetus, immune protection of the fetus and functions as an endocrine organ, thereby determining the environment for fetal growth and development. Additionally, the placenta is a highly metabolic organ in itself, utilizing a majority of the oxygen and glucose derived from maternal circulation. Consequently, optimal placental function is required for the offspring to reach its genetic potential in utero. Among ruminants, pregnant sheep have been used extensively for investigating pregnancy physiology, in part due to the ability to place indwelling catheters within both maternal and fetal vessels, allowing for steady-state investigation of blood flow, nutrient uptakes and utilization, and hormone secretion, under non-stressed and non-anesthetized conditions. This methodology has been applied to both normal and compromised pregnancies. As such, our understanding of the in vivo physiology of pregnancy in sheep is unrivalled by any other species. However, until recently, a significant deficit existed in determining the specific function or significance of individual genes expressed by the placenta in ruminants. To that end, we developed and have been using in vivo RNA interference (RNAi) within the sheep placenta to examine the function and relative importance of genes involved in conceptus development (PRR15 and LIN28), placental nutrient transport (SLC2A1 and SLC2A3), and placenta-derived hormones (CSH). A lentiviral vector is used to generate virus that is stably integrated into the infected cell's genome, thereby expressing a short-hairpin RNA (shRNA), that when processed within the cell, combines with the RNA Induced Silencing Complex (RISC) resulting in specific mRNA degradation or translational blockage. To accomplish in vivo RNAi, day 9 hatched and fully expanded blastocysts are infected with the lentivirus for 4 to 5 h, and then surgically transferred to synchronized recipient uteri. Only the trophectoderm cells are infected by the replication deficient virus, leaving the inner cell mass unaltered, and we often obtain ~70% pregnancy rates following transfer of a single blastocyst. In vivo RNAi coupled with steady-state study of blood flow and nutrient uptake, transfer and utilization can now provide new insight into the physiological consequences of modifying the translation of specific genes expressed within the ruminant placenta.

CSH RNA Interference Reduces Global Nutrient Uptake and Umbilical Blood Flow Resulting in Intrauterine Growth Restriction

Deficiency of the placental hormone chorionic somatomammotropin (CSH) can lead to the development of intrauterine growth restriction (IUGR). To gain insight into the physiological consequences of CSH RNA interference (RNAi), the trophectoderm of hatched blastocysts (nine days of gestational age; dGA) was infected with a lentivirus expressing either a scrambled control or CSH-specific shRNA, prior to transfer into synchronized recipient sheep. At 90 dGA, umbilical hemodynamics and fetal measurements were assessed by Doppler ultrasonography. At 120 dGA, pregnancies were fitted with vascular catheters to undergo steady-state metabolic studies with the ³H₂O transplacental diffusion technique at 130 dGA. Nutrient uptake rates were determined and tissues were subsequently harvested at necropsy. CSH RNAi reduced (p ≤ 0.05) both fetal and uterine weights as well as umbilical blood flow (mL/min). This ultimately resulted in reduced (p ≤ 0.01) umbilical IGF1 concentrations, as well as reduced umbilical nutrient uptakes (p ≤ 0.05) in CSH RNAi pregnancies. CSH RNAi also reduced (p ≤ 0.05) uterine nutrient uptakes as well as uteroplacental glucose utilization. These data suggest that CSH is necessary to facilitate adequate blood flow for the uptake of oxygen, oxidative substrates, and hormones essential to support fetal and uterine growth.

Impact of chorionic somatomammotropin RNA interference on uterine blood flow and placental glucose uptake in the absence of intrauterine growth restriction

Chorionic somatomammotropin (CSH) is one of the most abundantly produced placental hormones, yet its exact function remains elusive. Near-term [135 days of gestational age (dGA)], CSH RNA interference (RNAi) results in two distinct phenotypes: 1) pregnancies with intrauterine growth restriction (IUGR), and 2) pregnancies with normal fetal and placental weights. Here, we report the physiological changes in CSH RNAi pregnancies without IUGR. The trophectoderm of hatched blastocysts (9 dGA) were infected with lentiviral-constructs expressing either a scrambled control (Control RNAi) or CSH-specific shRNA (CSH RNAi), prior to transfer into synchronized recipient ewes. At 126 dGA, Control RNAi (n = 6) and CSH RNAi (n = 6) pregnancies were fitted with maternal and fetal catheters. Uterine and umbilical blood flows were measured at 132 dGA and nutrient uptakes were calculated by the Fick's principle. Control RNAi and CSH RNAi pregnancies were compared by analysis of variance, and significance was set at P ≤ 0.05. Absolute (mL/min) and relative (mL/min/kg fetus) uterine blood flows were reduced (P ≤ 0.05) in CSH RNAi pregnancies, but umbilical flows were not impacted. The uterine artery-to-vein glucose gradient (mmol/L) was significantly (P ≤ 0.05) increased. The uteroplacental glucose uptake (μmoL/min/kg placenta) was increased (P ≤ 0.05), whereas umbilical glucose uptake (μmoL/min/kg fetus) was reduced. Our results demonstrate that CSH RNAi has significant physiological ramifications, even in the absence of IUGR, and comparing CSH RNAi pregnancies exhibiting both IUGR and non-IUGR phenotypes may help determine the direct effects of CSH and its potential impact on fetal development.

MicroRNA-Mediated Gene Regulatory Mechanisms in Mammalian Female Reproductive Health

Mammalian reproductive health affects the entire reproductive cycle starting with the ovarian function through implantation and fetal growth. Various environmental and physiological factors contribute to disturbed reproductive health status leading to infertility problems in mammalian species. In the last couple of decades a significant number of studies have been conducted to investigate the transcriptome of reproductive tissues and organs in relation to the various reproductive health issues including endometritis, polycystic ovarian syndrome (PCOS), intrauterine growth restriction (IUGR), preeclampsia, and various age-associated reproductive disorders. Among others, the post-transcriptional regulation of genes by small noncoding miRNAs contributes to the observed transcriptome dysregulation associated with reproductive pathophysiological conditions. MicroRNAs as a class of non-coding RNAs are also known to be involved in various pathophysiological conditions either in cellular cytoplasm or they can be released to the extracellular fluid via membrane-bounded extracellular vesicles and proteins. The present review summarizes the cellular and extracellular miRNAs and their association with the etiology of major reproductive pathologies including PCOS, endometritis, IUGR and age-associated disorders in various mammalian species.

Chorionic somatomammotropin RNA interference alters fetal liver glucose utilization

Chorionic somatomammotropin (CSH) is a placenta-specific hormone associated with fetal growth, and fetal and maternal metabolism in both humans and sheep. We hypothesized that CSH deficiency could impact sheep fetal liver glucose utilization. To generate CSH-deficient pregnancies, day 9 hatched blastocysts were infected with lentiviral particles expressing CSH-specific shRNA (RNAi) or scramble control shRNA (SC) and transferred to synchronized recipients. CSH RNAi generated two distinct phenotypes at 135 days of gestational age (dGA); pregnancies with IUGR (RNAi-IUGR) or with normal fetal weight (RNAi-NW). Fetal body, fetal liver and placental weights were reduced (P < 0.05) only in RNAi-IUGR pregnancies compared to SC. Umbilical artery plasma insulin and insulin-like growth factor 1 (IGF1) concentrations were decreased, whereas insulin receptor beta (INSR) concentration in fetal liver was increased (P < 0.05) in both RNAi phenotypes. The mRNA concentrations of IGF1, IGF2, IGF binding protein 2 (IGFBP2) and IGFBP3 were decreased (P < 0.05) in fetal livers from both RNAi phenotypes. Fetal liver glycogen concentration and glycogen synthase 1 (GYS1) concentration were increased (P < 0.05), whereas fetal liver phosphorylated-GYS (inactive GYS) concentration was reduced (P < 0.05) in both RNAi phenotypes. Lactate dehydrogenase B (LDHB) concentration was increased (P < 0.05) and IGF2 concentration was decreased (P < 0.05) in RNAi-IUGR fetal livers only. Our findings suggest that fetal liver glucose utilization is impacted by CSH RNAi, independent of IUGR, and is likely tied to enhanced fetal liver insulin sensitivity in both RNAi phenotypes. Determining the physiological ramifications of both phenotypes, may help to differentiate direct effect of CSH deficiency or its indirect effect through IUGR.

PSII-34 Placental GLUT3 (SLC2A3) RNA interference: Impact on fetal growth at mid-gestation

Glucose is the predominant energy substrate for fetal oxidative processes and growth, and is taken up by the placenta and transported to the fetus by the facilitative transporters GLUT1 (SLC2A1) and GLUT3 (SLC2A3). SLC2A1 is the most abundant placental transporter, and as such is believed to be the primary glucose transporter in human and sheep placenta. However, SLC2A3 exhibits a six-fold greater glucose transport capacity, and in sheep, SLC2A3 is localized to the apical trophoblast membrane, whereas SLC2A1 is predominantly localized to the basolateral membrane, indicating that both may be required for optimal fetal development. It was our objective to use placenta-specific RNA interference (RNAi) to diminish SLC2A3, and determine the impact at mid-gestation (75 dGA) in sheep. Single hatched blastocysts were harvested and the trophectoderm was infected with lentiviral constructs expressing either a scramble control (SC) or SLC2A3-specific (GLUT3-RNAi) short-hairpin RNA, and then surgically transferred into a synchronized recipient. The resulting pregnancies underwent ultrasound Doppler velocimetry and fetal measurements at 70 dGA, and a terminal surgery at 75 dGA for collection of uterine and umbilical arterial and venous blood, fetal and placental measurements and tissue samples. Due to a lack of fetal sex x treatment interactions, statistical comparisons between SC (n = 6) and GLUT3-RNAi (n = 6) pregnancies were made by Student’s T-test. At 70 dGA, while umbilical artery velocimetry was not impacted, biparietal diameter (P ≤ 0.10), femur length and tibia length (P ≤ 0.05) were reduced in GLUT3-RNAi pregnancies. These results were confirmed at 75 dGA surgery, as GLUT3-RNAi fetuses had reduced fetal weight (P ≤ 0.10), head circumference (P ≤ 0.05), femur length (P ≤ 0.05), and tibia length (P ≤ 0.05). While it has been suggested that GLUT3 is predominantly important in late gestation, these preliminary data indicate that GLUT3 is important for normal fetal development during the first-half of gestation as well. Supported by NIH grant HD094952.

PSII-39 Trophectoderm-specific RNA interference of chorionic somatomammotropin alters glucose metabolism in sheep fetal liver

Chorionic somatomammotropin (CSH) is a placenta-specific hormone and secreted into both fetal and maternal circulation. Reduced maternal CSH is observed with intrauterine growth restriction (IUGR) in both humans and sheep, and it has long been held that CSH modulates maternal and fetal metabolism. We hypothesized that CSH deficiency, created by RNA interference (RNAi), could impact fetal liver glucose metabolism. To generate CSH-deficient pregnancies, day 9 hatched blastocysts were infected with lentiviral particles expressing CSH-specific shRNA (RNAi) or scramble control shRNA (SC) and transferred to synchronized recipients. CSH RNAi generated two distinct phenotypes at 135 dGA; CSH RNAi pregnancies with IUGR (RNAi-IUGR; n = 8) or without IUGR (RNAi; n = 8). Data from both RNAi phenotypes were compared separately with SC using Welch’s t-test. Liver and placental weights were reduced (P &lt; 0.05) in RNAi-IUGR pregnancies, but not in RNAi pregnancies, as compared to SC (n = 8). Umbilical artery plasma insulin and insulin-like growth factor 1 (IGF1) concentrations were decreased (P &lt; 0.05), whereas insulin receptor beta (IRβ) concentration, as determined by Western immunoblot analysis, in fetal liver was increased (P &lt; 0.05) in both RNAi phenotypes. Fetal liver glycogen quantity was also increased (P &lt; 0.05) in both RNAi phenotypes. Glycogen synthase-1 (GYS-1) concentration in fetal liver was increased (P &lt; 0.05) in both RNAi phenotypes, whereas there was no change in GYS-2 concentration. Phosphorylated-GYS (inactive GYS) was reduced (P &lt; 0.05) in fetal livers for both RNAi phenotypes. Lactate dehydrogenase beta (LDHβ) concentration was increased (P &lt; 0.05) and IGF2 concentration was decreased (P &lt; 0.05) in RNAi-IUGR fetal livers only. From these results we conclude that fetal liver glucose metabolism is impacted by CSH RNAi, independent of IUGR, and is likely tied to enhanced insulin sensitivity in both CSH RNAi phenotypes. Differences between the two phenotypes may help differentiate direct and indirect effects of CSH. Supported by NIH R01 HD093701.

152 Impact of chorionic somatomammotropin RNA interference on uterine blood flow and placental glucose uptake in the absence of intrauterine growth restriction

Chorionic somatomammotropin (CSH) is one of the most abundant hormones produced by the sheep placenta, yet the exact function of CSH has been elusive. Previously we reported the use of in vivo RNA interference (RNAi) to assess the impact of CSH deficiency on placental and fetal growth in sheep. Near-term (135 dGA), there are two distinct CSH RNAi phenotypes: 1) pregnancies with intrauterine growth restriction (IUGR), and 2) pregnancies with normal fetal and placental weights. This study describes physiological changes in the latter phenotype. To generate the CSH RNAi pregnancies, the trophectoderm of hatched blastocysts (9 dGA) were infected with lentiviral-constructs expressing either a scrambled control (NTS) or CSH-specific shRNA (CSH RNAi), prior to transfer into synchronized recipient ewes. At 120 dGA, 6 NTS and 6 CSH RNAi pregnancies were fitted with maternal and fetal catheters. Uterine and umbilical blood flows were measured utilizing the 3H2O transplacental diffusion technique at 132 dGA, and nutrient uptakes were calculated by the Fick principle. Resulting data were analyzed by Student’s t-test and significance was set at P ≤ 0.05. CSH RNAi tended (P ≤ 0.10) to reduce placentome weight with no effect on fetal weight. Absolute (ml/min) and relative (ml/min/kg fetus) uterine blood flows were reduced (P ≤ 0.05) in CSH RNAi pregnancies, but umbilical flows were not impacted. The uterine artery-to-vein glucose gradient (mmol/l) was significantly (P ≤ 0.05) increased, whereas the gradients for taurine and glycine were reduced (P ≤ 0.05). Uteroplacental glucose uptake (mmol/min/kg placenta) was increased 27% (P ≤ 0.05), whereas umbilical glucose uptake (mmol/min/kg fetus) was reduced 13%. This cohort demonstrates that even in the absence of IUGR, CSH deficiency has significant physiological ramifications, and the investigation of CSH RNAi pregnancies exhibiting both IUGR and non-IUGR phenotypes may help determine the direct effects of CSH and its potential impact on fetal programming. Supported by NIH R01 HD093701.

HMGA2 is regulated by LIN28 and BRCA1 in human placental cells

The chromatin associated transcription factor HMGA2 is a downstream target of let-7 miRNAs and binds to chromatin to regulate gene expression. Inhibition of let-7 miRNAs by RNA-binding proteins LIN28A and LIN28B is necessary during early embryogenesis to ensure stable expression of HMGA2. In addition to LIN28, HMGA2 is regulated by a BRCA1/ZNF350/CtIP repressor complex. In normal tissues, the BRCA1/ZNF350/CtIP complex binds to the HMGA2 promoter to prevent transcription. However, in many cancers the oncomiR miR-182 targets BRCA1, preventing BRCA1 translation and allowing for increased HMGA2. Little is known about the regulation of HMGA2 during early placental development; therefore, we hypothesized that both LIN28 and BRCA1 can regulate HMGA2 in placental cells. Using siRNA and CRISPR gene editing techniques, we found that knockdowns of both LIN28A and LIN28B increase HMGA2 levels in ACH-3P cells. These cells also demonstrated deficiencies in cell differentiation, seemingly differentiating solely towards the syncytiotrophoblast sublineage, secreting higher amounts of hCG, and displaying upregulated ERVW-1. Additionally, we found that a knockout of both LIN28A and LIN28B caused a significant increase of miR-182 and a decrease in BRCA1 allowing HMGA2 mRNA levels to increase and protein levels to remain the same. Using chromatin immunoprecipitation, we saw binding of the BRCA1 repressor complex to HMGA2. We also saw a decrease in binding to HMGA2's promoter in the LIN28A/B knockout cells. These findings suggest a novel role for BRCA1 during early human placental development.

LIN28-let-7 axis regulates genes in immortalized human trophoblast cells by targeting the ARID3B-complex

Abnormal placental development is one of the main etiological factors for intrauterine growth restriction (IUGR). Here, we show that LIN28A and LIN28B are significantly lower and lethal-7 (let-7) microRNAs (miRNAs) significantly higher in term human IUGR vs. normal placentas. We hypothesize that let-7 miRNAs regulate genes with known importance for human placental development [high-mobility group AT-hook 1 (HMGA1), transcriptional regulator Myc-like (c-myc), vascular endothelial growth factor A (VEGF-A), and Wnt family member 1 (WNT1)] by targeting the AT-rich interacting domain (ARID)-3B complex. ACH-3P cells with LIN28A and LIN28B knockout (DKOs) significantly increased let-7 miRNAs, leading to significantly decreased ARID3A, ARID3B, and lysine demethylase 4C (KDM4C). Similarly, Sw.71 cells overexpressing LIN28A and LIN28B (DKIs) significantly decreased let-7 miRNAs, leading to significantly increased ARID3A, ARID3B, and KDM4C. In ACH-3P cells, ARID3A, ARID3B, and KDM4C make a triprotein complex [triprotein complex comprising ARID3A, ARID3B, and KDM4C (ARID3B-complex)] that binds the promoter regions of HMGA1, c-MYC, VEGF-A, and WNT1. ARID3B knockout in ACH-3P cells disrupted the ARID3B-complex, leading to a significant decrease in HMGA1, c-MYC, VEGF-A, and WNT1. DKOs had a significant reduction, whereas DKIs had a significant increase in HMGA1, c-MYC, VEGF-A, and WNT1, potentially due to regulation by the ARID3B-complex. This is the first study showing regulation of let-7 targets in immortalized human trophoblast cells by the ARID3B-complex.-Ali, A., Anthony, R. V., Bouma, G. J., Winger, Q. A. LIN28-let-7 axis regulates genes in immortalized human trophoblast cells by targeting the ARID3B-complex.

Chorionic somatomammotropin impacts early fetal growth and placental gene expression

Several developmental windows, including placentation, must be negotiated to establish and maintain pregnancy. Impaired placental function can lead to preeclampsia and/or intrauterine growth restriction (IUGR), resulting in increased infant mortality and morbidity. It has been hypothesized that chorionic somatomammotropin (CSH) plays a significant role in fetal development, potentially by modifying maternal and fetal metabolism. Recently, using lentiviral-mediated in vivo RNA interference in sheep, we demonstrated significant reductions in near-term (135 days of gestation; dGA) fetal and placental size, and altered fetal liver gene expression, resulting from CSH deficiency. We sought to examine the impact of CSH deficiency on fetal and placental size earlier in gestation (50 dGA), and to examine placental gene expression at 50 and 135 dGA. At 50 dGA, CSH-deficient pregnancies exhibited a 41% reduction (P ≤ 0.05) in uterine vein concentrations of CSH, and significant (P ≤ 0.05) reductions (≈21%) in both fetal body and liver weights. Placentae harvested at 50 and 135 dGA exhibited reductions in IGF1 and IGF2 mRNA concentrations, along with reductions in SLC2A1 and SLC2A3 mRNA. By contrast, mRNA concentrations for various members of the System A, System L and System y⁺ amino acid transporter families were not significantly impacted. The IUGR observed at the end of the first-third of gestation indicates that the near-term IUGR reported previously, began early in gestation, and may have in part resulted from deficits in the paracrine action of CSH within the placenta. These results provide further compelling evidence for the importance of CSH in the progression and outcome of pregnancy.

Effect of proline rich 15-deficiency on trophoblast viability and survival

Deviations from the normal program of gene expression during early pregnancy can lead to early embryonic loss as well as dysfunctional placentation, which can cause significant morbidity and mortality. Proline rich 15 (PRR15) is a low molecular weight nuclear protein expressed by the trophoblast during early gestation. Lentivirus-mediated knockdown of PRR15 mRNA in ovine trophectoderm led to demise of the embryo by gestational day 15, providing compelling evidence that PRR15 expression is critical during this precarious window of development. Our objective was to determine the effect of PRR15 knockdown on trophoblast gene expression, proliferation, and survival. The first-trimester human trophoblast cell line, ACH-3P, was infected with control lentivirus or a lentivirus expressing a short hairpin (sh)RNA to target PRR15 mRNA for degradation, resulting in a 68% reduction in PRR15 mRNA. Microarray analysis of these cell lines revealed differential expression of genes related to cancer, focal adhesion, and p53 signaling. These changes included significant up-regulation of GDF15, a cytokine increased in pregnancies with preeclampsia. Viability and proliferation decreased in PRR15-deficient cells, which was consistent with down-regulation of cell cycle-related genes CCND1 and CDK6 and an up-regulation of CCNG2 and CDKN1A in the PRR15-deficient cells. TNFSF10, a tumor necrosis factor superfamily member known to induce apoptosis increased significantly in the PRR15-deficient cells. Migration through a basement membrane matrix decreased and an increased population of apoptotic cells was present when treated with shRNA to target PRR15. These results suggest that PRR15 enhances trophoblast viability and survival during early implantation and placentation.

The Potential Impact of Animal Science Research on Global Maternal and Child Nutrition and Health: A Landscape Review

High among the challenges facing mankind as the world population rapidly expands toward 9 billion people by 2050 is the technological development and implementation of sustainable agriculture and food systems to supply abundant and wholesome nutrition. In many low-income societies, women and children are the most vulnerable to food insecurity, and it is unequivocal that quality nutrition during the first 1000 d of life postconception can be transformative in establishing a robust, lifelong developmental trajectory. With the desire to catalyze disruptive advancements in global maternal and child health, this landscape review was commissioned by the Bill & Melinda Gates Foundation to examine the nutritional and managerial practices used within the food-animal agricultural system that may have relevance to the challenges faced by global human health. The landscape was categorized into a framework spanning 1) preconception, 2) gestation and pregnancy, 3) lactation and suckling, and 4) postweaning and toddler phases. Twelve key findings are outlined, wherein research within the discipline of animal sciences stands to inform the global health community and in some cases identifies gaps in knowledge in which further research is merited. Notable among the findings were 1) the quantitative importance of essential fatty acid and amino acid nutrition in reproductive health, 2) the suggested application of the ideal protein concept for improving the amino acid nutrition of mothers and children, 3) the prospect of using dietary phytase to improve the bioavailability of trace minerals in plant and vegetable-based diets, and 4) nutritional interventions to mitigate environmental enteropathy. The desired outcome of this review was to identify potential interventions that may be worthy of consideration. Better appreciation of the close linkage between human health, medicine, and agriculture will identify opportunities that will enable faster and more efficient innovations in global maternal and child health.

Increased fetal myocardial sensitivity to insulin-stimulated glucose metabolism during ovine fetal growth restriction

Unlike other visceral organs, myocardial weight is maintained in relation to fetal body weight in intrauterine growth restriction (IUGR) fetal sheep despite hypoinsulinemia and global nutrient restriction. We designed experiments in fetal sheep with placental insufficiency and restricted growth to determine basal and insulin-stimulated myocardial glucose and oxygen metabolism and test the hypothesis that myocardial insulin sensitivity would be increased in the IUGR heart. IUGR was induced by maternal hyperthermia during gestation. Control (C) and IUGR fetal myocardial metabolism were measured at baseline and under acute hyperinsulinemic/euglycemic clamp conditions at 128-132 days gestation using fluorescent microspheres to determine myocardial blood flow. Fetal body and heart weights were reduced by 33% (P = 0.008) and 30% (P = 0.027), respectively. Heart weight to body weight ratios were not different. Basal left ventricular (LV) myocardial blood flow per gram of LV tissue was maintained in IUGR fetuses compared to controls. Insulin increased LV myocardial blood flow by ∼38% (P < 0.01), but insulin-stimulated LV myocardial blood flow in IUGR fetuses was 73% greater than controls. Similar to previous reports testing acute hypoxia, LV blood flow was inversely related to arterial oxygen concentration (r(2 )= 0.71) in both control and IUGR animals. Basal LV myocardial glucose delivery and uptake rates were not different between IUGR and control fetuses. Insulin increased LV myocardial glucose delivery (by 40%) and uptake (by 78%) (P < 0.01), but to a greater extent in the IUGR fetuses compared to controls. During basal and hyperinsulinemic-euglycemic clamp conditions LV myocardial oxygen delivery, oxygen uptake, and oxygen extraction efficiency were not different between groups. These novel results demonstrate that the fetal heart exposed to nutrient and oxygen deprivation from placental insufficiency appears to maintain myocardial energy supply in the IUGR condition via increased glucose uptake and metabolic response to insulin, which support myocardial function and growth.

Development of ovine chorionic somatomammotropin hormone-deficient pregnancies

Intrauterine growth restriction (IUGR) is a leading cause of neonatal mortality and morbidity. Chorionic somatomammotropin hormone (CSH), a placenta-specific secretory product found at high concentrations in maternal and fetal circulation throughout gestation, is significantly reduced in human and sheep IUGR pregnancies. The objective of this study was to knock down ovine CSH (oCSH) expression in vivo using lentiviral-mediated short-hairpin RNA to test the hypothesis that oCSH deficiency would result in IUGR of near-term fetal lambs. Three different lentiviral oCSH-targeting constructs were used and compared with pregnancies (n = 8) generated with a scrambled control (SC) lentiviral construct. Pregnancies were harvested at 135 days of gestation. The most effective targeting sequence, "target 6" (tg6; n = 8), yielded pregnancies with significant reductions (P ≤ 0.05) in oCSH mRNA (50%) and protein (38%) concentrations, as well as significant reductions (P ≤ 0.05) in placental (52%) and fetal (32%) weights compared with the SC pregnancies. Fetal liver weights were reduced 41% (P ≤ 0.05), yet fetal liver insulin-like growth factor-I (oIGF1) and -II mRNA concentrations were reduced (P ≤ 0.05) 82 and 71%, respectively, and umbilical artery oIGF1 concentrations were reduced 62% (P ≤ 0.05) in tg6 pregnancies. Additionally, fetal liver oIGF-binding protein (oIGFBP) 2 and oIGFBP3 mRNA concentrations were reduced (P ≤ 0.05), whereas fetal liver oIGFBP1 mRNA concentration was not impacted nor was maternal liver oIGF and oIGFBP mRNA concentrations or uterine artery oIGF1 concentrations (P ≥ 0.10). Based on our results, it appears that oCSH deficiency does result in IUGR, by impacting placental development as well as fetal liver development and function.

Temporal Release, Paracrine and Endocrine Actions of Ovine Conceptus-Derived Interferon-Tau During Early Pregnancy

The antiviral activity of interferon (IFN) increases in uterine vein serum (UVS) during early pregnancy in sheep. This antiviral activity in UVS collected on Day 15 of pregnancy is blocked by anti-IFN-tau (anti-IFNT) antibodies. Conceptus-derived IFNT was hypothesized to induce IFN-stimulated gene (ISG) expression in endometrium and extrauterine tissues during pregnancy. To test this hypothesis, blood was collected from ewes on Days 12-16 of the estrous cycle or pregnancy. Serum progesterone was >1.7 ng/ml in pregnant (P) and nonpregnant (NP) ewes until Day 13, then declined to <0.6 ng/ml by Day 15 in NP ewes. A validated IFNT radioimmunoassay detected IFNT in uterine flushings (UFs) on Days 13-16 and in UVS on Days 15-16 of pregnancy. IFNT detection in UF correlated with paracrine induction of ISGs in the endometrium and occurred prior to the inhibition of estrogen receptor 1 and oxytocin receptor expression in uterine epithelia on Day 14 of pregnancy. Induction of ISG mRNAs in corpus luteum (CL) and liver tissue occurred by Day 14 and in peripheral blood mononuclear cells by Day 15 in P ewes. Expression of mRNAs for IFN signal transducers and ISGs were greater in the CL of P than that of NP ewes on Day 14. It is concluded that: 1) paracrine actions of IFNT coincide with detection of IFNT in UF; 2) endocrine action of IFNT ensues through induction of ISGs in peripheral tissues; and 3) IFNT can be detected in UVS, but not until Days 15-16 of pregnancy, which may be limited by the sensitivity of the IFNT radioimmunoassay.

Duration of maternal undernutrition differentially alters fetal growth and hormone concentrations

To investigate the impact of duration of maternal undernutrition in twin sheep pregnancies, ewes were either fed 100% (C) or 50% of their nutrient requirements from 28 to 78 d gestational age (dGA) and readjusted to 100% beginning at 79 dGA (LC) or continuously restricted from 28 to 135 dGA (LL). Weights of the fetus, empty carcass, brain, and liver were greater in the LC than LL fetuses at 135 dGA (P ≤ 0.05). Although umbilical vein (UmV) glucose concentrations did not differ, the UmV:umbilical artery (UmA) glucose gradient was smaller (0.26 ± 0.03 vs 0.38 ± 0.03 and 0.39 ± 0.04 mmol L(-1); P ≤ 0.05) in LL than C and LC fetuses, respectively. Umbilical vein concentrations of IGF-1 were less (46.7 ± 5.62 vs 74.3 ± 6.71 ng/mL; P ≤ 0.05) in LL than LC fetuses. Additionally, LL fetuses tended (P ≤ 0.10) to have lower UmA concentrations of insulin (0.24 ± 0.13 vs 0.70 ± 0.15 ng/mL) and IGF-1 (66.6 ± 7.51 vs 91.4 ± 8.97 ng/mL) than LC fetuses. Although most of the observed differences occurred between LC and LL pregnancies, LC fetuses tended (P ≤ 0.10) to have greater UmV and UmA pCO2 than C fetuses. Furthermore, the UmV:UmA O2 content gradient tended to be greater (5.02 ± 0.43 vs 3.41 ± 0.47; P ≤ 0.10) in C than LL fetuses. UmA placental lactogen also tended to be greater (46.6 ± 4.40 vs 31.1 ± 4.69 ng/mL; P ≤ 0.10) in LL than C fetuses. These data suggest that in twin pregnancies, maternal undernutrition followed by realimentation induces a different fetal outcome compared with continuous nutrient restriction, and both may differ physiologically from control fed pregnancies.

Androgen receptor and histone lysine demethylases in ovine placenta

Sex steroid hormones regulate developmental programming in many tissues, including programming gene expression during prenatal development. While estradiol is known to regulate placentation, little is known about the role of testosterone and androgen signaling in placental development despite the fact that testosterone rises in maternal circulation during pregnancy and in placenta-induced pregnancy disorders. We investigated the role of testosterone in placental gene expression, and focused on androgen receptor (AR). Prenatal androgenization decreased global DNA methylation in gestational day 90 placentomes, and increased placental expression of AR as well as genes involved in epigenetic regulation, angiogenesis, and growth. As AR complexes with histone lysine demethylases (KDMs) to regulate AR target genes in human cancers, we also investigated if the same mechanism is present in the ovine placenta. AR co-immunoprecipitated with KDM1A and KDM4D in sheep placentomes, and AR-KDM1A complexes were recruited to a half-site for androgen response element (ARE) in the promoter region of VEGFA. Androgenized ewes also had increased cotyledonary VEGFA. Finally, in human first trimester placental samples KDM1A and KDM4D immunolocalized to the syncytiotrophoblast, with nuclear KDM1A and KDM4D immunostaining also present in the villous stroma. In conclusion, placental androgen signaling, possibly through AR-KDM complex recruitment to AREs, regulates placental VEGFA expression. AR and KDMs are also present in first trimester human placenta. Androgens appear to be an important regulator of trophoblast differentiation and placental development, and aberrant androgen signaling may contribute to the development of placental disorders.

Embryo mortality in Isg15-/- mice is exacerbated by environmental stress

The interferon-stimulated gene 15 (Isg15) encodes a ubiquitin-like protein that is induced in the endometrium by pregnancy in mice, humans, and ruminants. Because ISG15 is a component of the innate immune system, we hypothesized that development of the embryo, fetus, and postnatal pup may be impaired in mice lacking Isg15 (Isg15(-/-)) and that this development would be further impaired in response to environmental insults such as hypoxia. The number of implantation sites, resorption sites, dead embryos, and the changes in overall gross morphology of the uterus were evaluated in Isg15(-/-) mice on Days 7.5 and 12.5 postcoitum (dpc). Postnatal development also was monitored from birth to 12 wk of age. On 7.5 dpc, the number of implantation sites and serum progesterone concentrations were similar. However, embryo mortality increased (P < 0.05) in Isg15(-/-) dams by 12.5 dpc, resulting in smaller litter sizes (4.26 ± 0.21 embryos; n = 83 litters) compared to Isg15(+/+) females (7.78 ± 0.29 pups; n = 47 litters). Embryo mortality in Isg15(-/-) mice was further exacerbated to 70% when dams were stressed through housing under hypoxic conditions (PB = 445 mmHg; 6.5-12.5 dpc). Transmission electron microscopy revealed lesions in antimesometrial decidua as well as trophoblast cells adjacent to decidual cells on 7.5 dpc. ISG15 was localized to mesometrial decidua on 7.5 dpc. By 12.5 dpc, ISG15 was intensely localized to the labyrinth of the placenta. By 7.5 dpc, uterine natural killer cell migration into the mesometrial pole was diminished by 65% and was less prevalent in Isg15(-/-) compared to Isg15(+/+) deciduum. Postnatal growth rate of offspring that survived to birth from Isg15(-/-) and Isg15(+/+) dams was not different. Embryo mortality occurs in pregnant Isg15(-/-) mice, is exacerbated by environmental insults like maternal hypoxia, and might result from impaired early decidualization, vascular development, and formation of the labyrinth.

Elevated maternal cortisol leads to relative maternal hyperglycemia and increased stillbirth in ovine pregnancy

In normal pregnancy, cortisol increases; however, further pathological increases in cortisol are associated with maternal and fetal morbidities. These experiments were designed to test the hypothesis that increased maternal cortisol would increase maternal glucose concentrations, suppress fetal growth, and impair neonatal glucose homeostasis. Ewes were infused with cortisol (1 mg·kg(-1)·day(-1)) from day 115 of gestation to term; maternal glucose, insulin, ovine placental lactogen, estrone, progesterone, nonesterified free fatty acids (NEFA), β-hydroxybutyrate (BHB), and electrolytes were measured. Infusion of cortisol increased maternal glucose concentration and slowed the glucose disappearance after injection of glucose; maternal infusion of cortisol also increased the incidence of fetal death at or near parturition. The design of the study was altered to terminate the study prior to delivery, and post hoc analysis of the data was performed to test the hypothesis that maternal metabolic factors predict the fetal outcome. In cortisol-infused ewes that had stillborn lambs, plasma insulin was increased relative to control ewes or cortisol-infused ewes with live lambs. Maternal cortisol infusion did not alter maternal food intake or plasma NEFA, BHB, estrone, progesterone or placental lactogen concentrations, and it did not alter fetal body weight, ponderal index, or fetal organ weights. Our study suggests that the adverse effect of elevated maternal cortisol on pregnancy outcome may be related to the effects of cortisol on maternal glucose homeostasis, and that chronic maternal stress or adrenal hypersecretion of cortisol may create fetal pathophysiology paralleling some aspects of maternal gestational diabetes.

Role of LIN28A in mouse and human trophoblast cell differentiation

Proper regulation of trophoblast proliferation, differentiation, and function are critical for placenta development and function. The RNA-binding protein, LIN28A, has been well characterized as a potent regulator of differentiation in embryonic stem cells; however, little is known about the function of LIN28A in the placenta. We assessed LIN28A in vitro using mouse trophoblast stem (mTS) cells and human trophoblast cells (ACH-3P). We observed that LIN28A decreased and let-7 miRNA increased when mTS cells were induced to differentiate into mouse trophoblast giant cells (mTGCs) upon the removal of FGF4, heparin and conditioned medium. Similarly, we observed that LIN28A decreased in ACH-3P cells induced to syncytialize with forskolin treatment. To assess LIN28A in vivo we examined Embryonic Day 11.5 mouse placenta and observed abundant LIN28A in the chorioallantoic interface and labyrinth layer, with little LIN28A staining in spongiotrophoblast or differentiated mTGCs. Additionally, shRNA-mediated LIN28A knockdown in ACH-3P cells resulted in increased spontaneous syncytialization, and increased levels of syncytiotrophoblast markers hCG, LGALS13, and ERVW-1 mRNA. Additionally, targeted degradation of LIN28A mRNA increased responsiveness to forskolin-induced differentiation. In contrast, targeted degradation of Lin28a mRNA in mTS cells did not alter cell phenotype when maintained under proliferative culture conditions. Together, these data establish that LIN28A has a functional role in regulating trophoblast differentiation and function, and that loss of LIN28A in human trophoblast is sufficient to induce differentiation, but does not induce differentiation in the mouse.

Effects of overfeeding naturally-mated adolescent ewes on maternal, fetal, and postnatal lamb growth

The objective of this study was to evaluate the effects of overfeeding naturally-mated adolescent ewes (Ovis aries) on maternal, fetal, and postnatal lamb growth, hormone concentrations, and lamb carcass characteristics. Two experiments were conducted in which singleton-bearing adolescent ewes were fed a diet containing 2.72 Mcal/kg ME at a rate which met NRC gestational age requirements (MN; n = 10 in Exp. 1, n = 7 in Exp. 2) or were fed the same diet ad libitum (15% refusal rate) throughout gestation (HN; n = 7 in Exp. 1, n = 6 in Exp. 2). Ewe BW was greater (P < 0.05) for HN than MN ewes beginning on 75 d and 52 d of gestation for Exp. 1 and 2, respectively. Final BCS was greater (P ≤ 0.05) for HN than MN ewes in both experiments; 3.5 vs. 3.0, respectively, for Exp. 1, and 4.8 vs. 2.9, respectively, for Exp. 2. Fasting maternal blood insulin concentrations were greater (P ≤ 0.05) in HN ewes near term (135 d of gestation), whereas fasting maternal glucose concentrations were greater (P ≤ 0.05) during most of the second half of gestation in HN ewes, for both experiments. Gestation length did not differ (P = 0.69) between treatments in Exp. 1, but in Exp. 2, HN ewes had shorter (P = 0.01) gestation lengths (144 vs. 149 d) and had increased (P = 0.002) dystocia scores. Fetal abdominal circumference was greater (P < 0.05) in lambs from MN than HN ewes at 97 d of gestation in Exp. 1 (20.8 vs. 17.4 cm) but did not differ (P = 0.94) between treatments at 95 d of gestation in Exp. 2 (averaging 20.5 cm). There were no differences (P ≥ 0.15) in lamb BW, abdominal circumference, crown-rump length, and biparietal distance at birth; or in postnatal BW and plasma concentrations of glucose, insulin, and lactate in either experiment. There were no differences (P ≥ 0.18) in HCW, dressing percentage, LM area, fat thickness, or KPH between treatments in Exp. 2. Although there was no difference (P ≥ 0.31) between treatments in concentrations of IGF1 or IGF2 mRNA in liver samples collected at harvest, lambs from MN ewes had greater (P ≤ 0.05) concentrations of IGF1R and INSR mRNA, suggesting long-term effects of maternal diet on postnatal hepatic function. In conclusion, excess nutrition during gestation in naturally-mated adolescent ewes did not affect birth weight or postnatal performance of offspring.

The chemokine receptor CXCR4 and its ligand CXCL12 are activated during implantation and placentation in sheep

BACKGROUND

The progression of implantation and placentation in ruminants is complex and is regulated by interplay between sex steroids and local signaling molecules, many of which have immune function. Chemokines and their receptors are pivotal factors in implantation and vascularization of the placenta. Based on known critical roles for chemokine receptor 4 (CXCR4) during early pregnancy in other species, we hypothesized that CXCR4 and its ligand CXCL12 would increase in the endometrium and conceptus in response to implantation in ewes. The objectives of the current study were to determine if CXCL12 and CXCR4 were upregulated in: endometrium from pregnant compared to non-pregnant ewes and in, conceptuses, cotyledons, caruncles and intercaruncular tissue.

METHODS

Tissues were collected from sheep on Days 12, 13, 14, and 15 of either the estrous cycle or pregnancy and from pregnant ewes on Days 35 and 50. Blood samples from jugular and uterine vein were also collected on all days. Conceptuses were collected from mature ewes on Days 13, 15, 16, 17, 21 and 30 of gestation. Real time PCR was used to determine relative mRNA concentrations for CXCL12 and CXCR4 and Western blot analysis was employed to confirm protein concentration.

RESULTS

Differences described are P < 0.05. In the endometrium, CXCR4 mRNA and protein was greater on Day 15 of pregnancy compared to the estrous cycle. CXCL12 and CXCR4 mRNA in conceptuses was greater on Days 21 and 30 compared to earlier days. CXCL12 mRNA was greater in cotyledons on Day 35 compared to Day 50. On Day 35 of gestation, CXCR4 was greater compared to Day 50 in caruncle and intercaruncular tissue. White blood cells obtained from jugular and uterine vein collection had the greatest mRNA concentration of CXCL12 on Day 35 of pregnancy.

CONCLUSIONS

A comprehensive analysis of CXCL12 and CXCR4 expression in fetal and maternal tissues during early pregnancy is reported with noteworthy differences occurring during implantation and placentation in sheep. We interpreted these data to mean that the CXCL12/CXCR4 pathway is activated during implantation and placentation in sheep and is likely playing a role in the communication between trophoblast cells and the maternal endometrium.

Expression of miRNAs in ovine fetal gonads: potential role in gonadal differentiation

BACKGROUND

Gonadal differentiation in the mammalian fetus involves a complex dose-dependent genetic network. Initiation and progression of fetal ovarian and testicular pathways are accompanied by dynamic expression patterns of thousands of genes. We postulate these expression patterns are regulated by small non-coding RNAs called microRNAs (miRNAs). The aim of this study was to identify the expression of miRNAs in mammalian fetal gonads using sheep as a model.

METHODS

We determined the expression of 128 miRNAs by real time PCR in early-gestational (gestational day (GD) 42) and mid-gestational (GD75) sheep ovaries and testes. Expression data were further examined and validated by bioinformatic analysis.

RESULTS

Expression analysis revealed significant differences between ovaries and testes among 24 miRNAs at GD42, and 43 miRNAs at GD75. Bioinformatic analysis revealed that a number of differentially expressed miRNAs are predicted to target genes known to be important in mammalian gonadal development, including ESR1, CYP19A1, and SOX9. In situ hybridization revealed miR-22 localization within fetal testicular cords. As estrogen signaling is important in human and sheep ovarian development, these data indicate that miR-22 is involved in repressing estrogen signaling within fetal testes.

CONCLUSIONS

Based on our results we postulate that gene expression networks underlying fetal gonadal development are regulated by miRNAs.

eNOS, NO, and the activation of ERK and AKT signaling at mid-gestation and near-term in an ovine model of intrauterine growth restriction

Intrauterine growth restriction (IUGR) is a disease responsible for neonatal morbidity and mortality and perinatal death affecting 8% of all pregnancies. In sheep, IUGR that mimics the human IUGR disease closely can be brought on by environmental hyperthermia. Endothelial nitric oxidase synthase (eNOS) and nitric oxide (NO) are important in the regulation of blood flow in the fetal-placental circulation and are modulated by several factors including hypoxia. eNOS activity is also regulated by the phosphorylation of ERK1/2 and AKT proteins in various tissues. In a hyperthermic (HT) ovine model of IUGR with systemic hypertension and increased blood flow resistance, our objective was to determine the relationship between p-ERK, p-AKT, eNOS, and NO concentrations in the placenta, uterine, and umbilical vessels at mid-gestation and near-term. Eight pregnant ewes were exposed to hyperthermic conditions for either 55 or 80 days to induce IUGR. Sheep necropsies were performed at mid-gestation and near-term for collection of placentomes, umbilical vessels, and the uterine artery. Tissues were assessed for eNOS mRNA and protein, and p-ERK and p-AKT protein. Blood was collected for NO determination at the time of necropsy. Placental insufficiency and IUGR (PI-IUGR) pregnancies demonstrated: 1) reduced placental weight at mid-gestation and reduced placental and fetal weight near-term, 2) no changes in eNOS protein concentration in the uterine artery and umbilical vessels, but an increase in NO in umbilical vein blood at both time points, 3) no significant changes in signal transduction makers (ERK/AKT) in placental tissue at mid-gestation but a significant increase near-term in cotyledon tissues, and 4) an increase in p-AKT in the uterine vessels at term. The near-term findings of increased placental p-ERK and p-AKT proteins and umbilical vein NO concentration suggest one mechanism responsible for the increase in placental eNOS previously described in this PI-IUGR model characterized by fetal systemic hypertension and abnormal umbilical artery Doppler velocimetry.

Assessing gene function in the ruminant placenta

The placenta provides the means for nutrient transfer from the mother to the fetus, waste transfer from the fetus to the mother, protection of the fetus from the maternal immune system, and is an active endocrine organ. While many placental functions have been defined and investigated, assessing the function of specific genes expressed by the placenta has been problematic, since classical ablation-replacement methods are not feasible with the placenta. The pregnant sheep has been a long-standing animal model for assessing in vivo physiology during pregnancy, since surgical placement of indwelling catheters into both maternal and fetal vasculature has allowed the assessment of placental nutrient transfer and utilization, as well as placental hormone secretion, under unanesthetized-unstressed steady state sampling conditions. However, in ruminants the lack of well-characterized trophoblast cell lines and the inefficiency of creating transgenic pregnancies in ruminants have inhibited our ability to assess specific gene function. Recently, sheep and cattle primary trophoblast cell lines have been reported, and may further our ability to investigate trophoblast function and transcriptional regulation of genes expressed by the placenta. Furthermore, viral infection of the trophoectoderm layer of hatched blastocysts, as a means for placenta-specific transgenesis, holds considerable potential to assess gene function in the ruminant placenta. This approach has been used successfully to "knockdown" gene expression in the developing sheep conceptus, and has the potential for gain-of-function experiments as well. While this technology is still being developed, it may provide an efficient approach to assess specific gene function in the ruminant placenta.

Effect of dietary supplemental vitamin A concentration on performance, carcass merit, serum metabolites, and lipogenic enzyme activity in yearling beef steers

A randomized complete block design experiment with 360 single-source black yearling steers (average BW = 316.1 +/- 9.1 kg) fed a 91% concentrate (steam-flaked corn base) diet was conducted to evaluate the effects of supplemental vitamin A (0, 1,103, 2,205, 4,410, or 8,820 IU/kg of dietary DM) on plasma and liver vitamin A and E concentrations, lipogenic enzyme activity, marbling score, and performance of yearling steers. Final BW (586, 580, 590, 585, and 584 kg for 0, 1,103, 2,205, 4,410, and 8,820 IU of supplemental vitamin A/kg of DM, respectively) did not differ (P = 0.39) among treatments. Feed efficiency, ADG, and daily DMI did not differ (P > 0.10) among treatments within each 28-d period or for the overall experiment. From d 57 to slaughter, average DMI (10.33, 10.28, 10.57, 9.75, and 10.22 kg/steer daily for 0, 1,103, 2,205, 4,410, and 8,820 IU of vitamin A/kg of DM, respectively) was less (P < 0.02) by steers receiving 4,410 IU of supplemental vitamin A/kg of dietary DM than for steers in the other treatments. Furthermore, DMI was greater (P = 0.06) for steers receiving 2,205 IU of supplemental vitamin A/kg of dietary DM than for steers receiving 8,820 IU of supplemental vitamin A/kg of DM. Marbling score, HCW, LM area, and 12th-rib fat thickness did not differ (P > 0.10) among treatments. Similarly, the percentage of carcasses grading >or=USDA Choice (62.6, 52.8, 64.0, 58.4, and 58.4% for 0, 1,103, 2,205, 4,410, and 8,820 IU of vitamin A/kg of DM, respectively), Select, or <or=Standard did not differ (P > 0.10) among treatments. Except for d 56 (P = 0.050; r = 0.18 for liver retinol), no correlations (P > 0.10) between marbling score and any plasma or liver tissue retinol or alpha-tocopherol concentrations or vitamin A intake were found, and no differences (P > 0.10) in lipogenic enzyme activity were detected among treatments. Taken together with previous and concurrent research, results of this experiment suggest that vitamin A supplementation at a concentration up to twice the NRC recommendation has little effect on performance, marbling, or lipogenic enzyme activity in adipose tissue samples in yearling feedlot steers, and that 2,205 IU of supplemental vitamin A/kg of DM (20,000 IU/steer daily) or less is adequate to meet the vitamin A requirements of finishing beef cattle.

The involvement of proline-rich 15 in early conceptus development in sheep

The ruminant conceptus undergoes a period of elongation that is required for maternal recognition of pregnancy, prior to attaching to the endometrium. The purpose of these studies was to investigate the role of proline-rich 15 (PRR15) in the sheep conceptus by examining mRNA expression, protein localization, and the effect of PRR15 mRNA degradation. Conceptuses were collected on Days 11, 13, 15, 16, 17, 21, and 30 after mating. Quantitative RT-PCR showed expression of PRR15 mRNA corresponded with the process of trophoblast elongation, with peak expression occurring on Days 15 and 16. A recombinant ovine PRR15 was generated and used to create polyclonal antibodies against PRR15. Immunohistochemistry of a Day 15 conceptus indicated that PRR15 was localized predominantly in the nucleus of the trophectoderm and extraembryonic primitive endoderm. To test whether PRR15 was required during early conceptus development, RNA interference was employed. Blastocysts collected on Day 8 after mating were infected with a lentivirus expressing a short-hairpin RNA (shRNA) that targeted PRR15 mRNA for degradation, an shRNA containing a three-nucleotide mismatch to PRR15 mRNA, or a lentivirus expressing no shRNA. After infection, blastocysts were transferred into recipient ewes and collected back on Day 15 of gestation. Although the majority of the control and mismatched shRNA-treated conceptuses elongated and survived to Day 15, none of the embryos treated with the lentivirus expressing shRNA against PRR15 mRNA elongated, and most died. In conclusion, expression of PRR15 mRNA occurred during a narrow window of conceptus development, and degradation of PRR15 mRNA led to conceptus demise or abnormal development.

Expression of enzymes regulating placental ammonia homeostasis in human fetal growth restricted pregnancies

Functional placental insufficiency results in impaired feto-placental exchange, and subsequently in fetal growth restriction (FGR). We hypothesized that reductions in placental amino acid transporter activities in FGR pregnancies may be accompanied by abnormal expression of placental ammonia-handling enzymes. Term placentas were obtained from growth restricted (N=11) and normal (N=17) human pregnancies, and examined for glutamate dehydrogenase (GDH), glutamine synthetase (GS) and glutaminase (GA) mRNA and protein expression. Northern and Western blots were normalized on human actin mRNA and protein expression. For GA, the presence of mRNA coding the kidney isoform, and the absence of mRNA coding the liver isoform of the enzyme were demonstrated in the human placenta. In FGR pregnancies, placental expression of GDH mRNA was reduced (P<0.05) compared to normal pregnancies (1.576+/-0.144 vs. 2.092+/-0.177, respectively; mean+/-SE), whereas GS and GA mRNA expression was not different between the two types of pregnancy. GDH protein expression were also reduced (P<0.05) in FGR placentas compared to normal placentas (1.055+/-0.079 vs. 1.322+/-0.053, respectively; mean+/-SE). The GS and GA protein expression was not different in FGR pregnancies. Our data indicate that in cases of FGR, glutamate-to-oxoglutarate transformation in the placenta is limited, yet glutamine synthesis from and decomposition to glutamate seems to be preserved. This may reflect down-regulation of GDH in response to decreased fetal liver output and reduced umbilical artery glutamate concentrations in human FGR pregnancies.

Decreased placental X-linked inhibitor of apoptosis protein in an ovine model of intrauterine growth restriction

OBJECTIVE

The objective of the study was to assess placental apoptosis at both midgestation and near term in an ovine model of placental insufficiency (PI) and intrauterine growth restriction (IUGR).

STUDY DESIGN

At 40 days' gestational age (dGA), 2 groups of 4 ewes were exposed to hyperthermic conditions for either 55 days or 80 days to induce IUGR with necropsies at 95 (midgestation) and 130 dGA (term = 140 dGA), respectively. Blood gases were assessed and placental tissues obtained for apoptosis analyses.

RESULTS

PI-IUGR pregnancies showed: (1) a decrease in fetal O(2) saturation and pO(2) (P < .04), (2) an increase in placental villi apoptosis (P < .05) at midgestation and near term, and (3) a decrease of cotyledon X-linked inhibitor of apoptosis protein (XIAP) at both gestational periods (P < .04) with no differences in caruncle XIAP protein.

CONCLUSION

Placental villous apoptosis is increased at midgestation and near term in our ovine model of IUGR, and this increase is associated with a significant decrease in XIAP protein in the cotyledon of IUGR animals.

Effects of early gestation GH administration on placental and fetal development in sheep

Ovine GH (oGH) is synthesized in placental tissue during maximal placental growth and development. Our objectives were to localize oGH mRNA in the placenta, and study the impact of exogenous GH on twin pregnancies during the normal window (35-55 days of gestational age; dGA) of placental expression. In situ hybridization localized oGH mRNA in uterine luminal epithelium but not in tissues of fetal origin. While maternal GH and IGF-I concentrations were increased (P<0.001) approximately tenfold, uterine, uterine fluid, placental, and fetal weights were unaffected by treatment at either 55 or 135 dGA. Fetal length, liver weight, and liver weight per kg of body weight were unaffected by maternal GH treatment. However, in the cotyledon, IGF-binding protein (BP)-1 and IGFBP-4 mRNA concentrations were increased (P<0.05), while IGFBP-2 mRNA was decreased (P<0.05). The concentration of mRNA for IGFBP-3 was unaffected by treatment. Within the caruncle, IGFBP-1 mRNA was decreased (P<0.05), while IGFBP-3 and IGFBP-4 mRNA were increased (P<0.05), and IGFBP-2 mRNA was unchanged due to GH treatment. While our data indicate that elevated maternal GH and IGF-I concentrations during early and mid-gestation do not enhance placental and fetal growth in twin pregnancies, localization of GH mRNA in uterine luminal epithelium could explain GHs transitory expression from 35 to 55 dGA, since by the end of this period the majority of the uterine luminal epithelium has fused with chorionic binucleate cells forming the placental syncytium.