Selection of reference genes for normalisation of real-time RT-PCR in brain-stem death injury in Ovis aries

Identification and validation of stable reference genes for expression profiling of target genes in diverse ovine tissues

Quantitative PCR (qPCR) is a widely-used technique for quantifying the expression of target genes across various tissues, as well as under different pathological and physiological conditions. One of the challenges associated with this method is the need to identify optimal reference genes (RGs) that maintain consistent expression levels under diverse experimental settings, thereby ensuring accurate biological interpretation. In this study, we conducted a thorough analysis of 18 candidate RGs (ACTB, BACH1, B2M, GAPDH, HMBS, HPRT1, PGK1, PPIA, PPIB, RPLP0, RPL19, RPS9, RPS15, RPS28, SDHA, TBP, UXT, and YWHAZ) across 10 ovine tissues (muscle, skin, kidney, liver, intestine, rumen, lung, testis, heart, and spleen) obtained from five individual sheep. We aimed to identify genes with stable expression across these tissues. A literature-based survey helped us shortlist candidate genes representing various functional classes from multiple livestock species. We employed four algorithms: geNorm, NormFinder, BestKeeper, and Delta Ct (ΔCt), to rank these genes based on their stability. A consistent trend in the rankings was observed across these different algorithms. RefFinder was then used for a comprehensive ranking, integrating the outputs from the various methods. ACTB, PPIB, BACH1, and B2M emerged as the most stable RGs, while RPS9, RPS15, and PGK1 displayed variable expression. We validated our findings through qPCR analysis of four target genes (ACTN2, CRYAB, DLK1, and TRIM54) in the skin samples from two different sheep breeds. Based on these results, we recommend ACTB, PPIB, BACH1, and B2M as reliable internal control genes for qPCR experiments involving diverse ovine tissues.

Expression profile analysis of sheep ovary after superovulation and estrus synchronisation treatment

Superovulation is a widely used reproductive technique in livestock production, but the mechanism of sheep's superovulation is not yet clear. Here, a method of superovulation and estrus synchronisation was used to treat female Duolang sheep. After treatment, there were significant differences in serum FSH and LH levels and the number of dominant follicles between the two groups of sheep. We identified a total of 5021 differentially expressed genes (11, 13 and 15 days after treatment) and performed RT‐qPCR analysis to identify several mRNA expression levels. GO and KEGG enrichment analysis revealed that differentially expressed genes were involved in the regulation of signalling pathways of follicular development, cell cycle, material synthesis, energy metabolism, such as COL3A1, RPS8, ACTA2, RPL7 RPS6 and TNFAIP6 may play a key role in regulating the development of follicles. Our results show a comprehensive expression profile after superovulation and estrus synchronisation treatment. We provide the basis for further research on breeding techniques to improve the ovulation rate and birth rate of livestock.

PPARγ activation in late gestation does not promote surfactant maturation in the fetal sheep lung

Respiratory distress syndrome results from inadequate functional pulmonary surfactant and is a significant cause of mortality in preterm infants. Surfactant is essential for regulating alveolar interfacial surface tension, and its synthesis by Type II alveolar epithelial cells is stimulated by leptin produced by pulmonary lipofibroblasts upon activation by peroxisome proliferator-activated receptor γ (PPARγ). As it is unknown whether PPARγ stimulation or direct leptin administration can stimulate surfactant synthesis before birth, we examined the effect of continuous fetal administration of either the PPARγ agonist, rosiglitazone (RGZ; Study 1) or leptin (Study 2) on surfactant protein maturation in the late gestation fetal sheep lung. We measured mRNA expression of genes involved in surfactant maturation and showed that RGZ treatment reduced mRNA expression of LPCAT1 (surfactant phospholipid synthesis) and LAMP3 (marker for lamellar bodies), but did not alter mRNA expression of PPARγ, surfactant proteins (SFTP-A, -B, -C, and -D), PCYT1A (surfactant phospholipid synthesis), ABCA3 (phospholipid transportation), or the PPARγ target genes SPHK-1 and PAI-1. Leptin infusion significantly increased the expression of PPARγ and IGF2 and decreased the expression of SFTP-B. However, mRNA expression of the majority of genes involved in surfactant synthesis was not affected. These results suggest a potential decreased capacity for surfactant phospholipid and protein production in the fetal lung after RGZ and leptin administration, respectively. Therefore, targeting PPARγ may not be a feasible mechanistic approach to promote lung maturation.

Impact of maternal late gestation undernutrition on surfactant maturation, pulmonary blood flow and oxygen delivery measured by magnetic resonance imaging in the sheep fetus

Restriction of fetal substrate supply has an adverse effect on surfactant maturation in the lung and thus affects the transition from in utero placental oxygenation to pulmonary ventilation ex utero. The effects on surfactant maturation are mediated by alteration in mechanisms regulating surfactant protein and phospholipid synthesis. This study aimed to determine the effects of late gestation maternal undernutrition (LGUN) and LGUN plus fetal glucose infusion (LGUN+G) compared to Control on surfactant maturation and lung development, and the relationship with pulmonary blood flow and oxygen delivery ( D O 2 ) measured by magnetic resonance imaging (MRI) with molecules that regulate lung development. LGUN from 115 to 140 days' gestation significantly decreased fetal body weight, which was normalized by glucose infusion. LGUN and LGUN+G resulted in decreased fetal plasma glucose concentration, with no change in fetal arterial P O 2 compared to control. There was no effect of LGUN and LGUN+G on the mRNA expression of surfactant proteins (SFTP) and genes regulating surfactant maturation in the fetal lung. However, blood flow in the main pulmonary artery was significantly increased in LGUN, despite no change in blood flow in the left or right pulmonary artery and D O 2 to the fetal lung. There was a negative relationship between left pulmonary artery flow and D O 2 to the left lung with SFTP-B and GLUT1 mRNA expression, while their relationship with VEGFR2 was positive. These results suggest that increased pulmonary blood flow measured by MRI may have an adverse effect on surfactant maturation during fetal lung development. KEY POINTS: Maternal undernutrition during gestation alters fetal lung development by impacting surfactant maturation. However, the direction of change remains controversial. We examined the effects of maternal late gestation maternal undernutrition (LGUN) on maternal and fetal outcomes, signalling pathways involved in fetal lung development, pulmonary haemodynamics and oxygen delivery in sheep using a combination of molecular and magnetic resonance imaging (MRI) techniques. LGUN decreased fetal plasma glucose concentration without affecting arterial P O 2 . Surfactant maturation was not affected; however, main pulmonary artery blood flow was significantly increased in the LGUN fetuses. This is the first study to explore the relationship between in utero MRI measures of pulmonary haemodynamics and lung development. Across all treatment groups, left pulmonary artery blood flow and oxygen delivery were negatively correlated with surfactant protein B mRNA and protein expression in late gestation.

Maternal periconceptional and first trimester protein restriction in beef heifers: effects on placental parameters and fetal and neonatal calf development

Few studies have investigated the effects of nutrition during the periconception and early gestation periods on fetal and placental development in cattle. In this study, nulliparous yearling heifers (n=360) were individually fed a diet high or low in protein (HPeri and LPeri) beginning 60 days before conception. From 24 to 98 days after conception, half of each treatment group was changed to the alternative high- or low-protein diet (HPost and LPost) yielding four groups in a 2×2 factorial design. A subset of heifers (n=46) was necropsied at 98 days after conception and fetoplacental development assessed. Placentome number and volume decreased in response to LPeri and LPost diets respectively. Absolute lung, pancreas, septum and ventricle weights decreased in LPost versus HPost fetuses, whereas the post-conception diet altered absolute and relative liver and brain weights depending on sex. Similarly, changes in fetal hepatic gene expression of factors regulating growth, glucose output and lipid metabolism were induced by protein restriction in a sex-specific manner. At term, neonatal calf and placental measures were not different. Protein restriction of heifers during the periconception and early gestation periods alters fetoplacental development and hepatic gene expression. These changes may contribute to functional consequences for progeny, but this may not be apparent from gross morphometry at birth.

Messenger RNA expression and localization of xenin in the gastrointestinal tract in sheep

The present study aimed to determine the primary sequence of ovine xenin and clarify the mRNA expression and peptide localization of xenin in the gastrointestinal tract in sheep. The colocalization of xenin and glucose-dependent insulinotropic polypeptide was also compared in the antrum and duodenum. Analysis of the nucleotide sequence of ovine xenin revealed a high degree (97.9%) of sequence homology of the sequence between sheep and cattle, and the amino acids sequence determined for ovine xenin coincided (100%) with that of other mammalian species. Real-time quantitative PCR for ovine xenin did not show regional difference in the mRNA expression ratio of xenin. In contrast to the real-time quantitative PCR results, anti-xenin positive cells were abundantly localized in the abomasal antrum (P < 0.01) and at a lesser amount in the duodenum, but no antixenin positive cells were observed in the other regions. Anti-xenin single-positive cells were in a majority in the abomasal antrum, whereas anti-xenin single-positive cells, and anti-GIP single-positive cells, and double-positive cells were even colocalized in the duodenum. These results suggest that abomasal antrum is a major source of xenin in the ovine gastrointestinal tract.

Impact of in vitro embryo culture and transfer on blood pressure regulation in the adolescent lamb

Nutrition during the periconceptional period influences postnatal cardiovascular health. We determined whether in vitro embryo culture and transfer, which are manipulations of the nutritional environment during the periconceptional period, dysregulate postnatal blood pressure and blood pressure regulatory mechanisms. Embryos were either transferred to an intermediate recipient ewe (ET) or cultured in vitro in the absence (IVC) or presence of human serum (IVCHS) and a methyl donor (IVCHS+M) for 6 days. Basal blood pressure was recorded at 19-20 weeks after birth. Mean arterial pressure (MAP) and heart rate (HR) were measured before and after varying doses of phenylephrine (PE). mRNA expression of signaling molecules involved in blood pressure regulation was measured in the renal artery. Basal MAP did not differ between groups. Baroreflex sensitivity, set point, and upper plateau were also maintained in all groups after PE stimulation. Adrenergic receptors alpha-1A (αAR1A), alpha-1B (αAR1B), and angiotensin II receptor type 1 (AT1R) mRNA expression were not different from controls in the renal artery. These results suggest there is no programmed effect of ET or IVC on basal blood pressure or the baroreflex control mechanisms in adolescence, but future studies are required to determine the impact of ET and IVC on these mechanisms later in the life course when developmental programming effects may be unmasked by age.

Identification of Novel miRNAs Involved in Cardiac Repair Following Infarction in Fetal and Adolescent Sheep Hearts

Aims

Animal models have been used to show that there are critical molecular mechanisms that can be activated to induce myocardial repair at specific times in development. For example, specific miRNAs are critical for regulating the response to myocardial infarction (MI) and improving the response to injury. Manipulating these miRNAs in small animal models provides beneficial effects post-MI; however it is not known if these miRNAs are regulated similarly in large mammals. Studying a large animal where the timing of heart development in relation to birth is similar to humans may provide insights to better understand the capacity to repair a developing mammalian heart and its application to the adult heart.

Methods

We used a sheep model of MI that included permanent ligation of the left anterior descending (LAD) coronary artery. Surgery was performed on fetuses (at 105 days gestation when all cardiomyocytes are mononucleated and proliferative) and adolescent sheep (at 6 months of age when all cardiomyocytes contribute to heart growth by hypertrophy). A microarray was utilized to determine the expression of known miRNAs within the damaged and undamaged tissue regions in fetal and adolescent hearts after MI.

Results

73 miRNAs were up-regulated and 58 miRNAs were down-regulated significantly within the fetal infarct compared to remote cardiac samples. From adolescent hearts 69 non-redundant miRNAs were up-regulated and 63 miRNAs were down-regulated significantly in the infarct area compared to remote samples. Opposite differential expression profiles of 10 miRNAs within tissue regions (Infarct area, Border zone and Remote area of the left ventricle) occurred between the fetuses and adolescent sheep. These included miR-558 and miR-1538, which when suppressed using LNA anti-miRNAs in cell culture, increased cardiomyoblast proliferation.

Conclusion

There were significant differences in miRNA responses in fetal and adolescent sheep hearts following a MI, suggesting that the modulation of novel miRNA expression may have therapeutic potential, by promoting proliferation or repair in a damaged heart.

Differential gene responses 3 days following infarction in the fetal and adolescent sheep heart

There are critical molecular mechanisms that can be activated to induce myocardial repair, and in humans this is most efficient during fetal development. The timing of heart development in relation to birth and the size/electrophysiology of the heart are similar in humans and sheep, providing a model to investigate the repair capacity of the mammalian heart and how this can be applied to adult heart repair. Myocardial infarction was induced by ligation of the left anterior descending coronary artery in fetal (105 days gestation when cardiomyocytes are proliferative) and adolescent sheep (6 mo of age when all cardiomyocytes have switched to an adult phenotype). An ovine gene microarray was used to compare gene expression in sham and infarcted (remote, border and infarct areas) cardiac tissue from fetal and adolescent hearts. The gene response to myocardial infarction was less pronounced in fetal compared with adolescent sheep hearts and there were unique gene responses at each age. There were also region-specific changes in gene expression between each age, in the infarct tissue, tissue bordering the infarct, and tissue remote from the infarction. In total, there were 880 genes that responded to MI uniquely in the adolescent samples compared with 170 genes in the fetal response, as well as 742 overlap genes that showed concordant direction of change responses to infarction at both ages. In response to myocardial infarction, there were specific changes in genes within pathways of mitochondrial oxidation, muscle contraction, and hematopoietic cell lineages, suggesting that the control of energy utilization and immune function are critical for effective heart repair. The more restricted gene response in the fetus may be an important factor in its enhanced capacity for cardiac repair.

Differential Response to Injury in Fetal and Adolescent Sheep Hearts in the Immediate Post-myocardial Infarction Period

Aim: Characterizing the response to myocardial infarction (MI) in the regenerative sheep fetus heart compared to the post-natal non-regenerative adolescent heart may reveal key morphological and molecular differences that equate to the response to MI in humans. We hypothesized that the immediate response to injury in (a) infarct compared with sham, and (b) infarct, border, and remote tissue, in the fetal sheep heart would be fundamentally different to the adolescent, allowing for repair after damage.

Methods: We used a sheep model of MI induced by ligating the left anterior descending coronary artery. Surgery was performed on fetuses (105 days) and adolescent sheep (6 months). Sheep were randomly separated into MI (n = 5) or Sham (n = 5) surgery groups at both ages. We used magnetic resonance imaging (MRI), histological/immunohistochemical staining, and qRT-PCR to assess the morphological and molecular differences between the different age groups in response to infarction.

Results: Magnetic resonance imaging showed no difference in fetuses for key functional parameters; however there was a significant decrease in left ventricular ejection fraction and cardiac output in the adolescent sheep heart at 3 days post-infarction. There was no significant difference in functional parameters between MRI sessions at Day 0 and Day 3 after surgery. Expression of genes involved in glucose transport and fatty acid metabolism, inflammatory cytokines as well as growth factors and cell cycle regulators remained largely unchanged in the infarcted compared to sham ventricular tissue in the fetus, but were significantly dysregulated in the adolescent sheep. Different cardiac tissue region-specific gene expression profiles were observed between the fetal and adolescent sheep.

Conclusion: Fetuses demonstrated a resistance to cardiac damage not observed in the adolescent animals. The manipulation of specific gene expression profiles to a fetal-like state may provide a therapeutic strategy to treat patients following an infarction.

Nebulisation of synthetic lamellar lipids mitigates radiation-induced lung injury in a large animal model

Methods to protect against radiation-induced lung injury (RILI) will facilitate the development of more effective radio-therapeutic protocols for lung cancer and may provide the means to protect the wider population in the event of a deliberate or accidental nuclear or radiological event. We hypothesised that supplementing lipid membranes through nebulization of synthetic lamellar lipids would mitigate RILI. Following pre-treatment with either nebulised lamellar lipids or saline, anaesthetised sheep were prescribed fractionated radiotherapy (30 Gray (Gy) total dose in five 6 Gy fractions at 3–4 days intervals) to a defined unilateral lung volume. Gross pathology in radio-exposed lung 37 days after the first radiation treatment was consistent between treatment groups and consisted of deep red congestion evident on the pleural surface and firmness on palpation. Consistent histopathological features in radio-exposed lung were subpleural, periarteriolar and peribronchial intra-alveolar oedema, alveolar fibrosis, interstitial pneumonia and type II pneumocyte hyperplasia. The synthetic lamellar lipids abrogated radiation-induced alveolar fibrosis and reduced alpha-smooth muscle actin (ASMA) expression in radio-exposed lung compared to saline treated sheep. Administration of synthetic lamellar lipids was also associated with an increased number of cells expressing dendritic cell-lysosomal associated membrane protein throughout the lung.

Intrauterine growth restriction may reduce hepatic drug metabolism in the early neonatal period

The effects of intrauterine growth restriction (IUGR) extend well into postnatal life. IUGR is associated with an increased risk of adverse health outcomes, which often leads to greater medication usage. Many medications require hepatic metabolism for activation or clearance, but hepatic function may be altered in IUGR fetuses. Using a sheep model of IUGR, we determined the impact of IUGR on hepatic drug metabolism and drug transporter expression, both important mediators of fetal drug exposure, in late gestation and in neonatal life. In the late gestation fetus, IUGR decreased the gene expression of uptake drug transporter OATPC and increased P-glycoprotein protein expression in the liver, but there was no change in the activity of the drug metabolising enzymes CYP3A4 or CYP2D6. In contrast, at 3 weeks of age, CYP3A4 activity was reduced in the livers of lambs born with low birth weight (LBW), indicating that LBW results in changes to drug metabolising capacity in neonatal life. Together, these results suggest that IUGR may reduce hepatic drug metabolism in fetal and neonatal life through different mechanisms.

Early restriction of placental growth results in placental structural and gene expression changes in late gestation independent of fetal hypoxemia

Placental restriction and insufficiency are associated with altered patterns of placental growth, morphology, substrate transport capacity, growth factor expression, and glucocorticoid exposure. We have used a pregnant sheep model in which the intrauterine environment has been perturbed by uterine carunclectomy (Cx). This procedure results in early restriction of placental growth and either the development of chronic fetal hypoxemia (PaO_2≤17 mmHg) in late gestation or in compensatory placental growth and the maintenance of fetal normoxemia (PaO₂>17 mmHg). Based on fetal PaO₂, Cx, and Control ewes were assigned to either a normoxemic fetal group (Nx) or a hypoxemic fetal group (Hx) in late gestation, resulting in 4 groups. Cx resulted in a decrease in the volumes of fetal and maternal connective tissues in the placenta and increased placental mRNA expression of IGF2, vascular endothelial growth factor (VEGF), VEGFR‐2,ANGPT2, and TIE2. There were reduced volumes of trophoblast, maternal epithelium, and maternal connective tissues in the placenta and a decrease in placental GLUT1 and 11βHSD2 mRNA expression in the Hx compared to Nx groups. Our data show that early restriction of placental growth has effects on morphological and functional characteristics of the placenta in late gestation, independent of whether the fetus becomes hypoxemic. Similarly, there is a distinct set of placental changes that are only present in fetuses that were hypoxemic in late gestation, independent of whether Cx occurred. Thus, we provide further understanding of the different placental cellular and molecular mechanisms that are present in early placental restriction and in the emergence of later placental insufficiency.

A tissue-based approach to selection of reference genes for quantitative real-time PCR in a sheep osteoporosis model

BACKGROUND

In order to better understand the multifactorial nature of osteoporosis, animal models are utilized and compared to healthy controls. Female sheep are well established as a model for osteoporosis induced by ovariectomy, calcium and vitamin D low diet, application of steroids, or a combination of these treatments. Transcriptional studies can be performed by applying quantitative real time PCR (RT-qPCR). RT-qPCR estimates mRNA-levels of target genes in relation to reference genes. A chosen set of reference genes should not show variation under experimental conditions. Currently, no standard reference genes are accepted for all tissue types and experimental conditions. Studies examining reference genes for sheep are rare and only one study described stable reference in mandibular bone. However, this type of bone differs from trabecular bone where most osteoporotic fractures occur. The present study aimed at identifying a set of reference genes for relative quantification of transcriptional activity of ovine spine bone and ovine in vitro differentiated mesenchymal stromal cells (MSC) for reliable comparability.

METHODS

Twelve candidate reference genes belonging to different functional classes were selected and their expression was measured from cultured ovMSCs (n = 18) and ovine bone samples (n = 16), respectively. RefFinder was used to rank the candidate genes.

RESULTS

We identified B2M, GAPDH, RPL19 and YWHAZ as the best combination of reference genes for normalization of RT-qPCR results for transcriptional analyses of these ovine samples.

CONCLUSION

This study demonstrates the importance of applying a set of reference genes for RT-qPCR analysis in sheep. Based on our data we recommend using four identified reference genes for relative quantification of gene expression studies in ovine bone or for in vitro experiments with osteogenically differentiated ovine MSCs.

Genome-wide analysis of circular RNAs in prenatal and postnatal pituitary glands of sheep

Circular RNAs (circRNAs) are a class of animal non-coding RNAs and play an impor-tant role in animal growth and development. However, the expression and function of circRNAs in the pituitary gland of sheep are unclear. Transcriptome profiling of circRNAs in the pituitary gland of sheep may enable us to understand their biological functions. In the present study, we identified 10,226 circRNAs from RNA-seq data in the pituitary gland of prenatal and postnatal sheep. Reverse transcription PCR and DNA sequencing analysis confirmed the presence of several circRNAs. Real-time RT-PCR analysis showed that sheep circRNAs are resistant to RNase R digestion and are expressed in prenatal and postnatal pituitary glands. GO and KEGG enrichment analysis showed that host genes of differentially expressed circRNAs are involved in the regulation of hormone secretion as well as in several pathways related to these processes. We determined that numerous circRNAs interact with pituitary-specific miRNAs that are involved in the biologic functions of the pituitary gland. Moreover, several circRNAs contain at least one IRES element and open reading frame, indicating their potential to encode proteins. Our study provides comprehensive expression profiles of circRNAs in the pituitary gland, thereby offering a valuable resource for circRNA biology in sheep.

Differential effects of late gestation maternal overnutrition on the regulation of surfactant maturation in fetal and postnatal life

KEY POINTS

Offspring of overweight and obese women are at greater risk for respiratory complications at birth. We determined the effect of late gestation maternal overnutrition (LGON) in sheep on surfactant maturation, glucose transport and fatty acid metabolism in the lung in fetal and postnatal life. There were significant decreases in surfactant components and numerical density of surfactant producing cells in the alveolar epithelium due to LGON in the fetal lung. However, there were no differences in the levels of these surfactant components between control and LGON lambs at 30 days of age. The reduced capacity for surfactant production in fetuses as a result of LGON may affect the transition to air breathing at birth. There was altered glucose transport and fatty acid metabolism in the lung as a result of LGON in postnatal life. However, there is a normalisation of surfactant components that suggests accelerated maturation in the lungs after birth.

ABSTRACT

With the increasing incidence of obesity worldwide, the proportion of women entering pregnancy overweight or obese has increased dramatically. The fetus of an overnourished mother experiences numerous metabolic changes that may modulate lung development and hence successful transition to air breathing at birth. We used a sheep model of maternal late gestation overnutrition (LGON; from 115 days' gestation, term 147 ± 3 days) to determine the effect of exposure to an increased plane of nutrition in late gestation on lung development in the fetus (at 141 days' gestation) and the lamb (30 days after birth). We found a decrease in the numerical density of surfactant protein positive cells, as well as a reduction in mRNA expression of surfactant proteins (SFTP-A, -B and -C), a rate limiting enzyme in surfactant phospholipid synthesis (phosphate cytidylyltransferase 1, choline, α; PCYT1A), and glucose transporters (SLC2A1 and SLC2A4) in the fetal lung. In lambs at 30 days after birth, there were no differences between Control and LGON groups in the surfactant components that were downregulated in the LGON fetuses. However, mRNA expression of SFTP-A, PCYT1A, peroxisome proliferator activated receptor-γ, fatty acid synthase and fatty acid transport protein were increased in LGON lambs compared to controls. These results indicate a reduced capacity for surfactant production in late gestation. While these deficits are normalised by 30 days after birth, the lungs of LGON lambs exhibited altered glucose transport and fatty acid metabolism, which is consistent with an enhanced capacity for surfactant synthesis and restoration of surfactant maturity in these animals.

Maternal chronic hypoxia increases expression of genes regulating lung liquid movement and surfactant maturation in male fetuses in late gestation

KEY POINTS

Chronic fetal hypoxaemia is a common pregnancy complication associated with intrauterine growth restriction that may influence respiratory outcome at birth. We investigated the effect of maternal chronic hypoxia for a month in late gestation on signalling pathways regulating fetal lung maturation and the transition to air-breathing at birth using isobaric hypoxic chambers without alterations to maternal food intake. Maternal chronic hypoxia in late gestation increases fetal lung expression of genes regulating hypoxia signalling, lung liquid reabsorption and surfactant maturation, which may be an adaptive response in preparation for the successful transition to air-breathing at birth. In contrast to other models of chronic fetal hypoxaemia, late gestation onset fetal hypoxaemia promotes molecular regulation of fetal lung maturation. This suggests a differential effect of timing and duration of fetal chronic hypoxaemia on fetal lung maturation, which supports the heterogeneity observed in respiratory outcomes in newborns following exposure to chronic hypoxaemia in utero.

ABSTRACT

Chronic fetal hypoxaemia is a common pregnancy complication that may arise from maternal, placental and/or fetal factors. Respiratory outcome of the infant at birth likely depends on the duration, timing and severity of the hypoxaemic insult. We have isolated the effect of maternal chronic hypoxia (MCH) for a month in late gestation on fetal lung development. Pregnant ewes were exposed to normoxia (21% O2 ) or hypoxia (10% O2 ) from 105 to 138 days of gestation (term ∼145 days). At 138 days, gene expression in fetal lung tissue was determined by quantitative RT-PCR. Cortisol concentrations were determined in fetal plasma and lung tissue. Numerical density of surfactant protein positive cells was determined by immunohistochemistry. MCH reduced maternal PaO2 (106 ± 2.9 vs. 47 ± 2.8 mmHg) and fetal body weight (4.0 ± 0.4 vs. 3.2 ± 0.9 kg). MCH increased fetal lung expression of the anti-oxidant marker CAT and decreased expression of the pro-oxidant marker NOX-4. MCH increased expression of genes regulating hypoxia signalling and feedback (HIF-3α, KDM3A, SLC2A1, EGLN-3). There was no effect of MCH on fetal plasma/lung tissue cortisol concentrations, nor genes regulating glucocorticoid signalling (HSD11B-1, HSD11B-2, NR3C1, NR3C2). MCH increased expression of genes regulating sodium (SCNN1-B, ATP1-A1, ATP1-B1) and water (AQP-4) movement in the fetal lung. MCH promoted surfactant maturation (SFTP-B, SFTP-D, ABCA3) at the molecular level, but did not alter the numerical density of surfactant positive cells in lung tissue. MCH in late gestation promotes molecular maturation of the fetal lung, which may be an adaptive response in preparation for the successful transition to air-breathing at birth.

Two ovine mitochondrial DNAs harboring a fifth 75/76 bp repeat motif without altered gene expression in Northern Spain

The Basque Country is home to the Latxa sheep breed, which is divided in several varieties such as Latxa Black Face (LBKF) and Latxa Blonde Face (LBLF). Mitochondrial DNA control region analysis of 174 male sheep (97 LBKF and 77 LBLF) was performed with the objective of characterizing the maternal lineages of these two varieties that are the basis to produce the cheese with Idiazabal quality label. The percentage of unique haplotypes was 77.32% in LBKF and 67.53% in LBLF. Most of the individuals were classified into B haplogroup (98.85%), while A haplogroup was much less frequent. Two Latxa individuals (one LBKF and one LBLF), both belonging to B haplogroup, displayed an additional 75/76 bp tandem repeat motif. Only 33 other sequences with this repeat motif were found among 11 061 sheep sequences included in the GenBank database. Gene expression was analyzed in peripheral blood leukocytes since the additional 75/76 bp repeat motif falls within ETAS1, a domain with a possible function in regulation of replication and transcription. The mRNA expression from four mitochondrial genes (COI, cyt b, ND1, and ND2) was analyzed in the two individuals of this study with a fifth repeat motif and in four without it. Although lower transcription was observed when the additional 75/76 bp repeat motif was present, no statistically significant differences were observed. Therefore, the variation in the number of the 75/76 repeat motif does not seem to modify the gene expression rate in mitochondrial genes.

Short-term environmental enrichment is sufficient to counter stress-induced anxiety and associated structural and molecular plasticity in basolateral amygdala

Moderate levels of anxiety enable individual animals to cope with stressors through avoidance, and could be an adaptive trait. However, repeated stress exacerbates anxiety to pathologically high levels. Dendritic remodeling in the basolateral amygdala is proposed to mediate potentiation of anxiety after stress. Similarly, modulation of brain-derived neurotrophic factor is thought to be important for the behavioral effects of stress. In the present study, we investigate if relatively short periods of environmental enrichment in adulthood can confer resilience against stress-induced anxiety and concomitant changes in neuronal arborisation and brain derived neurotrophic factor within basolateral amygdala. Two weeks of environmental enrichment countermanded the propensity of increased anxiety following chronic immobilization stress. Environmental enrichment concurrently reduced dendritic branching and spine density of projection neurons of the basolateral amygdala. Moreover, stress increased abundance of BDNF mRNA in the basolateral amygdala in agreement with the dendritic hypertrophy post-stress and role of BDNF in promoting dendritic arborisation. In contrast, environmental enrichment prevented stress-induced rise in the BDNF mRNA abundance. Gain in body weights and adrenal weights remained unaffected by exposure to environmental enrichment. These observations suggest that a short period of environmental enrichment can provide resilience against maladaptive effects of stress on hormonal, neuronal and molecular mediators of anxiogenesis.

Selection of Reference Genes for Gene Expression Studies related to lung injury in a preterm lamb model

Preterm newborns often require invasive support, however even brief periods of supported ventilation applied inappropriately to the lung can cause injury. Real-time quantitative reverse transcriptase-PCR (qPCR) has been extensively employed in studies of ventilation-induced lung injury with the reference gene 18S ribosomal RNA (18S RNA) most commonly employed as the internal control reference gene. Whilst the results of these studies depend on the stability of the reference gene employed, the use of 18S RNA has not been validated. In this study the expression profile of five candidate reference genes (18S RNA, ACTB, GAPDH, TOP1 and RPS29) in two geographical locations, was evaluated by dedicated algorithms, including geNorm, Normfinder, Bestkeeper and ΔCt method and the overall stability of these candidate genes determined (RefFinder). Secondary studies examined the influence of reference gene choice on the relative expression of two well-validated lung injury markers; EGR1 and IL1B. In the setting of the preterm lamb model of lung injury, RPS29 reference gene expression was influenced by tissue location; however we determined that individual ventilation strategies influence reference gene stability. Whilst 18S RNA is the most commonly employed reference gene in preterm lamb lung studies, our results suggest that GAPDH is a more suitable candidate.

Regulation of lung maturation by prolyl hydroxylase domain inhibition in the lung of the normally grown and placentally restricted fetus in late gestation

Intrauterine growth restriction induced by placental restriction (PR) in sheep leads to chronic hypoxemia and reduced surfactant maturation. The underlying molecular mechanism involves altered regulation of hypoxia signaling by increased prolyl hydroxylase domain (PHD) expression. Here, we evaluated the effect of intratracheal administration of the PHD inhibitor dimethyloxalylglycine (DMOG) on functional, molecular, and structural determinants of lung maturation in the control and PR sheep fetus. There was no effect of DMOG on fetal blood pressure or fetal breathing movements. DMOG reduced lung expression of genes regulating hypoxia signaling (HIF-3α, ACE1), antioxidant defense (CAT), lung liquid reabsorption (SCNN1-A, ATP1-A1, AQP-1, AQP-5), and surfactant maturation (SFTP-A, SFTP-B, SFTP-C, PCYT1A, LPCAT, ABCA3, LAMP3) in control fetuses. There were very few effects of DMOG on gene expression in the PR fetal lung (reduced lung expression of angiogenic factor ADM, water channel AQP-5, and increased expression of glucose transporter SLC2A1). DMOG administration in controls reduced total lung lavage phosphatidylcholine to the same degree as in PR fetuses. These changes appear to be regulated at the molecular level as there was no effect of DMOG on the percent tissue, air space, or numerical density of SFTP-B positive cells in the control and PR lung. Hence, DMOG administration mimics the effects of PR in reducing surfactant maturation in the lung of control fetuses. The limited responsiveness of the PR fetal lung suggests a potential biochemical limit or reduced plasticity to respond to changes in regulation of hypoxia signaling following exposure to chronic hypoxemia in utero.

The Complex Relationship of Extracorporeal Membrane Oxygenation and Acute Kidney Injury: Causation or Association?

Extracorporeal membrane oxygenation (ECMO) is a modified cardiopulmonary bypass (CPB) circuit capable of providing prolonged cardiorespiratory support. Recent advancement in ECMO technology has resulted in increased utilisation and clinical application. It can be used as a bridge-to-recovery, bridge-to-bridge, bridge-to-transplant, or bridge-to-decision. ECMO can restitute physiology in critically ill patients, which may minimise the risk of progressive multiorgan dysfunction. Alternatively, iatrogenic complications of ECMO clearly contribute to worse outcomes. These factors affect the risk : benefit ratio of ECMO which ultimately influence commencement/timing of ECMO. The complex interplay of pre-ECMO, ECMO, and post-ECMO pathophysiological processes are responsible for the substantial increased incidence of ECMO-associated acute kidney injury (EAKI). The development of EAKI significantly contributes to morbidity and mortality; however, there is a lack of evidence defining a potential benefit or causative link between ECMO and AKI. This area warrants investigation as further research will delineate the mechanisms involved and subsequent strategies to minimise the risk of EAKI. This review summarizes the current literature of ECMO and AKI, considers the possible benefits and risks of ECMO on renal function, outlines the related pathophysiology, highlights relevant investigative tools, and ultimately suggests an approach for future research into this under investigated area of critical care.

Structural and molecular regulation of lung maturation by intratracheal vascular endothelial growth factor administration in the normally grown and placentally restricted fetus

Inhibition of hypoxia signalling leads to respiratory distress syndrome (RDS), whereas administration of vascular endothelial growth factor (VEGF), the most widely characterized hypoxia responsive factor, protects from RDS. In the lung of the chronically hypoxaemic placentally restricted (PR) fetus, there is altered regulation of hypoxia signalling. This leads to reduced surfactant maturation in late gestation and provides evidence for the increased risk of RDS in growth restricted neonates at birth. We evaluated the effect of recombinant human VEGF administration with respect to bypassing the endogenous regulation of hypoxia signalling in the lung of the normally grown and PR sheep fetus. There was no effect of VEGF administration on fetal blood pressure or fetal breathing movements. We examined the effect on the expression of genes regulating VEGF signalling (FLT1 and KDR), angiogenesis (ANGPT1, AQP1, ADM), alveolarization (MMP2, MMP9, TIMP1, COL1A1, ELN), proliferation (IGF1, IGF2, IGF1R, MKI67, PCNA), inflammation (CCL2, CCL4, IL1B, TNFA, TGFB1, IL10) and surfactant maturation (SFTP-A, SFTP-B, SFTP-C, SFTP-D, PCYT1A, LPCAT, LAMP3, ABCA3). Despite the effects of PR on the expression of genes regulating airway remodelling, inflammatory signalling and surfactant maturation, there were very few effects of VEGF administration on gene expression in the lung of both the normally grown and PR fetus. There were, however, positive effects of VEGF administration on percentage tissue, air space and numerical density of SFTP-B positive alveolar epithelial cells in fetal lung tissue. These results provide evidence for the stimulatory effects of VEGF administration on structural maturation in the lung of both the normally grown and PR fetus.

Novel 24-h ovine model of brain death to study the profile of the endothelin axis during cardiopulmonary injury

BACKGROUND

Upregulation of the endothelin axis has been observed in pulmonary tissue after brain death, contributing to primary graft dysfunction and ischaemia reperfusion injury. The current study aimed to develop a novel, 24-h, clinically relevant, ovine model of brain death to investigate the profile of the endothelin axis during brain death-associated cardiopulmonary injury. We hypothesised that brain death in sheep would also result in demonstrable injury to other transplantable organs.

METHODS

Twelve merino cross ewes were randomised into two groups. Following induction of general anaesthesia and placement of invasive monitoring, brain death was induced in six animals by inflation of an extradural catheter. All animals were supported in an intensive care unit environment for 24 h. Animal management reflected current human donor management, including administration of vasopressors, inotropes and hormone resuscitation therapy. Activation of the endothelin axis and transplantable organ injury were assessed using ELISA, immunohistochemistry and standard biochemical markers.

RESULTS

All animals were successfully supported for 24 h. ELISA suggested early endothelin-1 and big endothelin-1 release, peaking 1 and 6 h after BD, respectively, but there was no difference at 24 h. Immunohistochemistry confirmed the presence of the endothelin axis in pulmonary tissue. Brain dead animals demonstrated tachycardia and hypertension, followed by haemodynamic collapse, typified by a reduction in systemic vascular resistance to 46 ± 1 % of baseline. Mean pulmonary artery pressure rose to 186 ± 20 % of baseline at induction and remained elevated throughout the protocol, reaching 25 ± 2.2 mmHg at 24 h. Right ventricular stroke work increased 25.9 % above baseline by 24 h. Systemic markers of cardiac and hepatocellular injury were significantly elevated, with no evidence of renal dysfunction.

CONCLUSIONS

This novel, clinically relevant, ovine model of brain death demonstrated that increased pulmonary artery pressures are observed after brain death. This may contribute to right ventricular dysfunction and pulmonary injury. The development of this model will allow for further investigation of therapeutic strategies to minimise the deleterious effects of brain death on potentially transplantable organs.

Development of an experimental model of maternal allergic asthma during pregnancy

Maternal asthma during pregnancy adversely affects pregnancy outcomes but identification of the cause/s, and the ability to evaluate interventions, is limited by the lack of an appropriate animal model. We therefore aimed to characterise maternal lung and cardiovascular responses and fetal-placental growth and lung surfactant levels in a sheep model of allergic asthma. Immune and airway functions were studied in singleton-bearing ewes, either sensitised before pregnancy to house dust mite (HDM, allergic, n = 7) or non-allergic (control, n = 5), and subjected to repeated airway challenges with HDM (allergic group) or saline (control group) throughout gestation. Maternal lung, fetal and placental phenotypes were characterised at 140 ± 1 days gestational age (term, ∼147 days). The eosinophil influx into lungs was greater after HDM challenge in allergic ewes than after saline challenge in control ewes before mating and in late gestation. Airway resistance increased throughout pregnancy in allergic but not control ewes, consistent with increased airway smooth muscle in allergic ewes. Maternal allergic asthma decreased relative fetal weight (-12%) and altered placental phenotype to a more mature form. Expression of surfactant protein B mRNA was 48% lower in fetuses from allergic ewes than controls, with a similar trend for surfactant protein D. Thus, allergic asthma in pregnant sheep modifies placental phenotype, and inhibits fetal growth and lung development consistent with observations from human pregnancies. Preconceptional allergen sensitisation and repeated airway challenges in pregnant sheep therefore provides an animal model to identify mechanisms of altered fetal development and adverse pregnancy outcomes caused by maternal asthma in pregnancy.

Evaluation of reference gene suitability for quantitative expression analysis by quantitative polymerase chain reaction in the mandibular condyle of sheep

Reference genes are commonly used as a reliable approach to normalize the results of quantitative polymerase chain reaction (qPCR), and to reduce errors in the relative quantification of gene expression. Suitable reference genes belonging to numerous functional classes have been identified for various types of species and tissue. However, little is currently known regarding the most suitable reference genes for bone, specifically for the sheep mandibular condyle. Sheep are important for the study of human bone diseases, particularly for temporomandibular diseases. The present study aimed to identify a set of reference genes suitable for the normalization of qPCR data from the mandibular condyle of sheep. A total of 12 reference genes belonging to various functional classes were selected, and the expression stability of the reference genes was determined in both the normal and fractured area of the sheep mandibular condyle. RefFinder, which integrates the following currently available computational algorithms: geNorm, NormFinder, BestKeeper, and the comparative ΔCt method, was used to compare and rank the candidate reference genes. The results obtained from the four methods demonstrated a similar trend: RPL19, ACTB, and PGK1 were the most stably expressed reference genes in the sheep mandibular condyle. As determined by RefFinder comprehensive analysis, the results of the present study suggested that RPL19 is the most suitable reference gene for studies associated with the sheep mandibular condyle. In addition, ACTB and PGK1 may be considered suitable alternatives.

Regulation of microRNA during cardiomyocyte maturation in sheep

Background

There is a limited capacity to repair damage in the mammalian heart after birth, which is primarily due to the inability of cardiomyocytes to proliferate after birth. This is in contrast to zebrafish and salamander, in which cardiomyocytes retain the ability to proliferate throughout life and can regenerate their heart after significant damage. Recent studies in zebrafish and rodents implicate microRNA (miRNA) in the regulation of genes responsible for cardiac cell cycle progression and regeneration, in particular, miR-133a, the miR-15 family, miR-199a and miR-590. However, the significance of these miRNA and miRNA in general in the regulation of cardiomyocyte proliferation in large mammals, including humans, where the timing of heart development relative to birth is very different than in rodents, is unclear. To determine the involvement of miRNA in the down-regulation of cardiomyocyte proliferation occurring before birth in large mammals, we investigated miRNA and target gene expression in sheep hearts before and after birth. The experimental approach included targeted transcriptional profiling of miRNA and target mRNA previously identified in rodent studies as well as genome-wide miRNA profiling using microarrays.

Results

The cardiac expression of miR-133a increased and its target gene IGF1R decreased with increasing age, reaching their respective maximum and minimum abundance when the majority of ovine cardiomyocytes were quiescent. The expression of the miR-15 family members was variable with age, however, four of their target genes decreased with age. These latter profiles are inconsistent with the direct involvement of this family of miRNA in cardiomyocyte quiescence in late gestation sheep. The expression patterns of ‘pro-proliferative’ miR-199a and miR-590 were also inconsistent with their involvement in cardiomyocyte quiescence. Consequently, miRNA microarray analysis was undertaken, which identified six discrete clusters of miRNA with characteristic developmental profiles. The functions of predicted target genes for the miRNA in four of the six clusters were enriched for aspects of cell division and regulation of cell proliferation suggesting a potential role of these miRNA in regulating cardiomyocyte proliferation.

Conclusion

The results of this study show that the expression of miR-133a and one of its target genes is consistent with it being involved in the suppression of cardiomyocyte proliferation, which occurs across the last third of gestation in sheep. The expression patterns of the miR-15 family, miR-199a and miR-590 were inconsistent with direct involvement in the regulation cardiomyocyte proliferation in sheep, despite studies in rodents demonstrating that their manipulation can influence the degree of cardiomyocyte proliferation. miRNA microarray analysis suggests a coordinated and potentially more complex role of multiple miRNA in the regulation of cardiomyocyte quiescence and highlights significant differences between species that may reflect their substantial differences in the timing of this developmental process.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1693-z) contains supplementary material, which is available to authorized users.

Increased lung prolyl hydroxylase and decreased glucocorticoid receptor are related to decreased surfactant protein in the growth-restricted sheep fetus

Experimental placental restriction (PR) by carunclectomy in fetal sheep results in intrauterine growth restriction (IUGR), chronic hypoxemia, increased plasma cortisol, and decreased lung surfactant protein (SP) expression. The mechanisms responsible for decreased SP expression are unknown but may involve decreased glucocorticoid (GC) action or changes in hypoxia signaling. Endometrial caruncles were removed from nonpregnant ewes to induce PR. Lungs were collected from control and PR fetuses at 130-135 (n = 19) and 139-145 (n = 28) days of gestation. qRT-PCR and Western blotting were used to quantify lung mRNA and protein expression, respectively, of molecular regulators and downstream targets of the GC and hypoxia-signaling pathways. We confirmed a decrease in SP-A, -B, and -C, but not SP-D, mRNA expression in PR fetuses at both ages. There was a net downregulation of GC signaling with a reduction in GC receptor (GR)-α and -β protein expression and a decrease in the cofactor, GATA-6. GC-responsive genes including transforming growth factor-β1, IL-1β, and β2-adrenergic receptor were not stimulated. Prolyl hydroxylase domain (PHD)2 mRNA and protein and PHD3 mRNA expression increased with a concomitant increase in hypoxia-inducible factor-1α (HIF-1α) and HIF-1β mRNA expression. There was an increase in mRNA expression of several, but not all, hypoxia-responsive genes. Hence, both GC and hypoxia signaling may contribute to reduced SP expression. Although acute hypoxia normally inactivates PHDs, chronic hypoxemia in the PR fetus increased PHD abundance, which normally prevents HIF signaling. This may represent a mechanism by which chronic hypoxemia contributes to the decrease in SP production in the IUGR fetal lung.

The dilution effect and the importance of selecting the right internal control genes for RT-qPCR: a paradigmatic approach in fetal sheep

BACKGROUND

The key to understanding changes in gene expression levels using reverse transcription real-time quantitative polymerase chain reaction (RT-qPCR) relies on the ability to rationalize the technique using internal control genes (ICGs). However, the use of ICGs has become increasingly problematic given that any genes, including housekeeping genes, thought to be stable across different tissue types, ages and treatment protocols, can be regulated at transcriptomic level. Our interest in prenatal glucocorticoid (GC) effects on fetal growth has resulted in our investigation of suitable ICGs relevant in this model. The usefulness of RNA18S, ACTB, HPRT1, RPLP0, PPIA and TUBB as ICGs was analyzed according to effects of early dexamethasone (DEX) treatment, gender, and gestational age by two approaches: (1) the classical approach where raw (i.e., not normalized) RT-qPCR data of tested ICGs were statistically analyzed and the best ICG selected based on absence of any significant effect; (2) used of published algorithms. For the latter the geNorm Visual Basic application was mainly used, but data were also analyzed by Normfinder and Bestkeeper. In order to account for confounding effects on the geNorm analysis due to co-regulation among ICGs tested, network analysis was performed using Ingenuity Pathway Analysis software. The expression of RNA18S, the most abundant transcript, and correlation of ICGs with RNA18S, total RNA, and liver-specific genes were also performed to assess potential dilution effect of raw RT-qPCR data. The effect of the two approaches used to select the best ICG(s) was compared by normalization of NR3C1 (glucocorticoid receptor) mRNA expression, as an example for a target gene.

RESULTS

Raw RT-qPCR data of all the tested ICGs was significantly reduced across gestation. TUBB was the only ICG that was affected by DEX treatment. Using approach (1) all tested ICGs would have been rejected because they would initially appear as not reliable for normalization. However, geNorm analysis (approach 2) of the ICGs indicated that the geometrical mean of PPIA, HPRT1, RNA18S and RPLPO can be considered a reliable approach for normalization of target genes in both control and DEX treated groups. Different subset of ICGs were tested for normalization of NR3C1 expression and, despite the overall pattern of the mean was not extremely different, the statistical analysis uncovered a significant influence of the use of different normalization approaches on the expression of the target gene. We observed a decrease of total RNA through gestation, a lower decrease in raw RT-qPCR data of the two rRNA measured compared to ICGs, and a positive correlation between raw RT-qPCR data of ICGs and total RNA. Based on the same amount of total RNA to performed RT-qPCR analysis, those data indicated that other mRNA might have had a large increase in expression and, as consequence, had artificially diluted the stably expressed genes, such as ICGs. This point was demonstrated by a significant negative correlation of raw RT-qPCR data between ICGs and liver-specific genes.

CONCLUSION

The study confirmed the necessity of assessing multiple ICGs using algorithms in order to obtain a reliable normalization of RT-qPCR data. Our data indicated that the use of the geometrical mean of PPIA, HPRT1, RNA18S and RPLPO can provide a reliable normalization for the proposed study. Furthermore, the dilution effect observed support the unreliability of the classical approach to test ICGs. Finally, the observed change in the composition of RNA species through time reveals the limitation of the use of ICGs to normalize RT-qPCR data, especially if absolute quantification is required.

Low birth weight activates the renin-angiotensin system, but limits cardiac angiogenesis in early postnatal life

Low birth weight (LBW) is associated with increased risk of adult cardiovascular disease and this association may be partly a consequence of early programming of the renin-angiotensin system (RAS). We investigated the effects of LBW on expression of molecules in the RAS and cardiac tissue remodeling. Left ventricular samples were collected from the hearts of 21 days old lambs that were born average birth weight (ABW) and LBW. Cardiac mRNA expression was quantified using real-time RT-PCR and protein expression was quantified using Western blotting. DNA methylation and histone acetylation were assessed by combined bisulfite restriction analysis and chromatin immunoprecipitation, respectively. There were increased plasma renin activity, angiotensin I (ANGI), and ANGII concentrations in LBW compared to ABW lambs at day 20. In LBW lambs, there was increased expression of cardiac ACE2 mRNA, decreased ANGII receptor type 1 (AT1R) protein, and acetylation of histone H3K9 of the AT1R promoter but no changes in AT1R mRNA expression and AT1R promoter DNA methylation. There was no difference in the abundance of proteins involved in autophagy or fibrosis. BIRC5 and VEGF mRNA expression was increased; however, the total length of the capillaries was decreased in the hearts of LBW lambs. Activation of the circulating and local cardiac RAS in neonatal LBW lambs may be expected to increase cardiac fibrosis, autophagy, and capillary length. However, we observed only a decrease in total capillary length, suggesting a dysregulation of the RAS in the heart of LBW lambs and this may have significant implications for heart health in later life.

IGF-2R-Gαq signaling and cardiac hypertrophy in the low-birth-weight lamb

The cardiac insulin-like growth factor 2 receptor (IGF-2R) can induce cardiomyocyte hypertrophy in a heterotrimeric G protein receptor-coupled manner involving αq (Gαq) or αs (Gαs). We have previously shown increased left ventricular weight and cardiac IGF-2 and IGF-2R gene expression in low-birth-weight (LBW) compared with average-birth-weight (ABW) lambs. Here, we have investigated the cardiac expression of IGF-2 gene variants, the degree of histone acetylation, and the abundance of proteins in the IGF-2R downstream signaling pathway in ABW and LBW lambs. Samples from the left ventricle of ABW and LBW lambs were collected at 21 days of age. There was increased phospho-CaMKII protein with decreased HDAC 4 abundance in the LBW compared with ABW lambs. There was increased GATA 4 and decreased phospho-troponin I abundance in LBW compared with ABW lambs, which are markers of pathological cardiac hypertrophy and impaired or reduced contractility, respectively. There was increased histone acetylation of H3K9 at IGF-2R promoter and IGF-2R intron 2 differentially methylated region in the LBW lamb. In conclusion, histone acetylation of IGF-2R may lead to increased IGF-2R mRNA expression and subsequently mediate Gαq signaling early in life via CaMKII, resulting in an increased risk of left ventricular hypertrophy and cardiovascular disease in adult life.

Chronic hypoxemia in late gestation decreases cardiomyocyte number but does not change expression of hypoxia-responsive genes

Background

Placental insufficiency is the leading cause of intrauterine growth restriction in the developed world and results in chronic hypoxemia in the fetus. Oxygen is essential for fetal heart development, but a hypoxemic environment in utero can permanently alter development of cardiomyocytes. The present study aimed to investigate the effect of placental restriction and chronic hypoxemia on total number of cardiomyocytes, cardiomyocyte apoptosis, total length of coronary capillaries, and expression of genes regulated by hypoxia.

Methods and Results

We induced experimental placental restriction from conception, which resulted in fetal growth restriction and chronic hypoxemia. Fetal hearts in the placental restriction group had fewer cardiomyocytes, but interestingly, there was no difference in the percentage of apoptotic cardiomyocytes; the abundance of the transcription factor that mediates hypoxia‐induced apoptosis, p53; or expression of apoptotic genes Bax and Bcl2. Likewise, there was no difference in the abundance of autophagy regulator beclin 1 or expression of autophagic genes BECN1, BNIP3, LAMP1, and MAP1LC3B. Furthermore, fetuses exposed to normoxemia (control) or chronic hypoxemia (placental restriction) had similar mRNA expression of a suite of hypoxia‐inducible factor target genes, which are essential for angiogenesis (VEGF, Flt1, Ang1, Ang2, and Tie2), vasodilation (iNOS and Adm), and glycolysis (GLUT1 and GLUT3). In addition, there was no change in the expression of PKC‐ε, a cardioprotective gene with transcription regulated by hypoxia in a manner independent of hypoxia‐inducible factors. There was an increased capillary length density but no difference in the total length of capillaries in the hearts of the chronically hypoxemic fetuses.

Conclusion

The lack of upregulation of hypoxia target genes in response to chronic hypoxemia in the fetal heart in late gestation may be due to a decrease in the number of cardiomyocytes (decreased oxygen demand) and the maintenance of the total length of capillaries. Consequently, these adaptive responses in the fetal heart may maintain a normal oxygen tension within the cardiomyocyte of the chronically hypoxemic fetus in late gestation.

Early dexamethasone treatment induces placental apoptosis in sheep

Glucocorticoid treatment given in late pregnancy in sheep resulted in altered placental development and function. An imbalance of placental survival and apoptotic factors resulting in an increased rate of apoptosis may be involved. We have now investigated the effects of dexamethasone (DEX) in early pregnancy on binucleate cells (BNCs), placental apoptosis, and fetal sex as a determinant of these responses. Pregnant ewes carrying singleton fetuses (n = 105) were randomized to control (n = 56, 2 mL saline/ewe) or DEX treatment (n = 49, intramuscular injections of 0.14 mg/kg ewe weight per 12 hours over 48 hours) at 40 to 41 days of gestation (dG). Placentomes were collected at 50, 100, 125, and 140 dG. At 100 dG, DEX in females reduced BNC numbers, placental antiapoptotic (proliferating cell nuclear antigen), and increased proapoptotic factors (Bax, p53), associated with a temporarily decrease in fetal growth. At 125 dG, BNC numbers and apoptotic markers were restored to normal. In males, ovine placental lactogen-protein levels after DEX were increased at 50 dG, but at 100 and 140 dG significantly decreased compared to controls. In contrast to females, these changes were independent of altered BNC numbers or apoptotic markers. Early DEX was associated with sex-specific, transient alterations in BNC numbers, which may contribute to changes in placental and fetal development. Furthermore, in females, altered placental apoptosis markers may be involved.

Intrafetal glucose infusion alters glucocorticoid signaling and reduces surfactant protein mRNA expression in the lung of the late-gestation sheep fetus

Increased circulating fetal glucose and insulin concentrations are potential inhibitors of fetal lung maturation and may contribute to the pathogenesis of respiratory distress syndrome (RDS) in infants of diabetic mothers. In this study, we examined the effect of intrafetal glucose infusion on mRNA expression of glucose transporters, insulin-like growth factor signaling, glucocorticoid regulatory genes, and surfactant proteins in the lung of the late-gestation sheep fetus. The numerical density of the cells responsible for producing surfactant was determined using immunohistochemistry. Glucose infusion for 10 days did not affect mRNA expression of glucose transporters or IGFs but did decrease IGF-1R expression. There was reduced mRNA expression of the glucocorticoid-converting enzyme HSD11B-1 and the glucocorticoid receptor, potentially reducing glucocorticoid responsiveness in the fetal lung. Furthermore, surfactant protein (SFTP) mRNA expression was reduced in the lung following glucose infusion, while the number of SFTP-B-positive cells remained unchanged. These findings suggest the presence of a glucocorticoid-mediated mechanism regulating delayed maturation of the surfactant system in the sheep fetus following glucose infusion and provide evidence for the link between abnormal glycemic control during pregnancy and the increased risk of RDS in infants of uncontrolled diabetic mothers.

Exposure to rosiglitazone, a PPAR-γ agonist, in late gestation reduces the abundance of factors regulating cardiac metabolism and cardiomyocyte size in the sheep fetus

It is unknown whether cardiomyocyte hypertrophy and the transition to fatty acid oxidation as the main source of energy after birth is dependent on the maturation of the cardiomyocytes' metabolic system, or on the limitation of substrate availability before birth. This study aimed to investigate whether intrafetal administration of a peroxisome proliferator-activated receptor-γ (PPAR-γ) agonist, rosiglitazone, during late gestation can stimulate the expression of factors regulating cardiac growth and metabolism in preparation for birth, and the consequences of cardiac contractility in the fetal sheep at ∼140 days gestation. The mRNA expression and protein abundance of key factors regulating growth and metabolism were quantified using quantitative RT-PCR and Western blot analysis, respectively. Cardiac contractility was determined by measuring the Ca(2+) sensitivity and maximum Ca(2+)-activated force of skinned cardiomyocyte bundles. Rosiglitazone-treated fetuses had a lower cardiac abundance of insulin-signaling molecules, including insulin receptor-β, insulin receptor substrate-1 (IRS-1), phospho-IRS-1 (Tyr-895), phosphatidylinositol 3-kinase (PI3K) regulatory subunit p85, PI3K catalytic subunit p110α, phospho-3-phosphoinositide-dependent protein kinase 1 (Ser-241), protein kinase B (Akt-1), phospho-Akt (Ser-273), PKCζ, phospho-PKCζ(Thr-410), Akt substrate 160 kDa (AS160), phospho-AS160 (Thr-642), and glucose transporter type-4. Additionally, cardiac abundance of regulators of fatty acid β-oxidation, including adiponectin receptor 1, AMPKα, phospho-AMPKα (Thr-172), phospho-acetyl CoA carboxylase (Ser-79), carnitine palmitoyltransferase-1, and PGC-1α was lower in the rosiglitazone-treated group. Rosiglitazone administration also resulted in a decrease in cardiomyocyte size. Rosiglitazone administration in the late-gestation sheep fetus resulted in a decreased abundance of factors regulating cardiac glucose uptake, fatty acid β-oxidation, and cardiomyocyte size. These findings suggest that activation of PPAR-γ using rosiglitazone does not promote the maturation of cardiomyocytes; rather, it may decrease cardiac metabolism and compromise cardiac health later in life.

Maternal dietary restriction during the periconceptional period in normal-weight or obese ewes results in adrenocortical hypertrophy, an up-regulation of the JAK/STAT and down-regulation of the IGF1R signaling pathways in the adrenal of the postnatal lamb

Maternal dietary restriction during the periconceptional period results in an increase in adrenal growth and in the cortisol stress response in the offspring. The intraadrenal mechanisms that result in the programming of these changes are not clear. Activation of the IGF and the signal transducer and activator of transcription (STAT)/suppressors of cytokine signaling (SOCS) pathways regulate adrenal growth. We have used an embryo transfer model in sheep to investigate the impact of exposure to either dietary restriction in normal or obese mothers or to maternal obesity during the periconceptional period on adrenal growth and function in the offspring. We assessed the adrenal abundance of key signaling molecules in the IGF-I and Janus kinase/STAT/SOCS pathways including IGF-I receptor, IGF-II receptor, Akt, mammalian target of rapamycin, ribosomal protein S6, eukaryotic translation initiation factor 4E-binding protein 1, eukaryotic translation initiation factor 4E, STAT1, STAT3, STAT5, SOCS1, and SOCS3 in female and male postnatal lambs. Maternal dietary restriction in the periconceptional period resulted in the hypertrophy of the adrenocortical cells in the zona fasciculata-reticularis and an up-regulation in STAT1, phospho-STAT1, and phospho-STAT3 (Ser727) abundance and a down-regulation in IGF-I receptor, Akt, and phospho-Akt abundance in the adrenal cortex of the postnatal lamb. These studies highlight that weight loss around the time of conception, independent of the starting maternal body weight, results in the activation of the adrenal Janus kinase/STAT pathway and adrenocortical hypertrophy. Thus, signals of adversity around the time of conception have a long-term impact on the mechanisms that regulate adrenocortical growth.

The fetal sheep lung does not respond to cortisol infusion during the late canalicular phase of development

The prepartum surge in plasma cortisol concentrations in humans and sheep promotes fetal lung and surfactant system maturation in the support of air breathing after birth. This physiological process has been used to enhance lung maturation in the preterm fetus using maternal administration of betamethasone in the clinical setting in fetuses as young as 24 weeks gestation (term = 40 weeks). Here, we have investigated the impact of fetal intravenous cortisol infusion during the canalicular phase of lung development (from 109- to 116-days gestation, term = 150 ± 3 days) on the expression of genes regulating glucocorticoid (GC) activity, lung liquid reabsorption, and surfactant maturation in the very preterm sheep fetus and compared this to their expression near term. Cortisol infusion had no impact on mRNA expression of the corticosteroid receptors (GC receptor and mineralocorticoid receptor) or HSD11B-2, however, there was increased expression of HSD11B-1 in the fetal lung. Despite this, cortisol infusion had no effect on the expression of genes involved in lung sodium (epithelial sodium channel -α, -β, or -γ subunits and sodium–potassium ATPase-β1 subunit) or water (aquaporin 1, 3, and 5) reabsorption when compared to the level of expression during exposure to the normal prepartum cortisol surge. Furthermore, in comparison to late gestation, cortisol infusion does not increase mRNA expression of surfactant proteins (SFTP-A, -B, and -C) or the number of SFTP-B-positive cells present in the alveolar epithelium, the cells that produce pulmonary surfactant. These data suggest that there may be an age before which the lung is unable to respond biochemically to an increase in fetal plasma cortisol concentrations.

Dietary restriction in the periconceptional period in normal-weight or obese ewes results in increased abundance of angiotensin-converting enzyme (ACE) and angiotensin type 1 receptor (AT1R) in the absence of changes in ACE or AT1R methylation in the adrenal of the offspring

Exposure to dietary restriction during the periconceptional period in either normal or obese ewes results in increased adrenal growth and a greater cortisol response to stress in the offspring, but the mechanisms that programme these changes are not fully understood. Activation of the angiotensin type 1 receptor (AT1R) has been demonstrated to stimulate adrenal growth and steroidogenesis. We have used an embryo transfer model in the sheep to investigate the effects of exposure to dietary restriction in normal or obese mothers from before and 1 week after conception on the methylation status, expression, abundance and localisation of key components of the renin–angiotensin system (RAS) in the adrenal of post-natal lambs. Maternal dietary restriction in normal or obese ewes during the periconceptional period resulted in an increase in angiotensin-converting enzyme (ACE) and AT1R abundance in the absence of changes in the methylation status or mRNA expression ofACEandAT1Rin the adrenal of the offspring. Exposure to maternal obesity alone also resulted in an increase in adrenal AT1R abundance. There was no effect of maternal dietary restriction or obesity on ACE2 and AT2R or on ERK, calcium/calmodulin-dependent kinase II abundance, and their phosphorylated forms in the lamb adrenal. Thus, weight loss around the time of conception, in both normal-weight and obese ewes, results in changes within the intra-adrenal RAS consistent with increased AT1R activation. These changes within the intra-adrenal RAS system may contribute to the greater adrenal stress response following exposure to signals of adversity in the periconceptional period.

Aging and sequential resistance exercise bout effects on housekeeping gene messenger RNA expression in human skeletal muscle

The purpose of this study was to investigate how age and 1 week of conventional resistance exercise affects commonly used housekeeping gene (HKG) messenger RNAs (mRNAs) in skeletal muscle. Ten college-aged (18-25 years) and 10 older (60-76 years) men completed 3 lower-body resistance exercise bouts on Monday, Wednesday, and Friday, and muscle samples were obtained before bout 1 (T1), 48 hours after the first (T2) and second bouts (T3), and 24 hours after the third bout (T4). Raw Ct values indicated that β-actin and cyclophilin were more highly expressed in older vs. younger males (p < 0.01) at T1. When normalizing each HKG mRNA to the other 4 HKG mRNAs, CYC increased at T3 and glyceraldehyde-3-phosphate dehydrogenase decreased at T2 (p < 0.05) in younger men. This is one of the few studies to suggest that explicit HKG mRNAs should be used depending upon age group and resistance exercise intervention.

Downregulation of serotonergic gene expression in the Raphe nuclei of the midbrain under chronic social defeat stress in male mice

There is ample experimental evidence supporting the hypothesis that the brain serotonergic system is involved in the control of chronic social defeat stress (CSDS), depression, and anxiety. The study aimed to analyze mRNA levels of the serotonergic genes in the raphe nuclei of midbrain that may be associated with chronic social defeats consistently shown by male mice in special experimental settings. The serotonergic genes were the Tph2, Sert, Maoa, and Htr1a. The Bdnf and Creb genes were also studied. The experimental groups were composed of male mice with experience of defeats in 21 daily encounters and male mice with the same track record of defeats followed by a no-defeat period without agonistic interactions (relative rest for 14 days). It has been shown that mRNA levels of the Tph2, Maoa, Sert, Htr1a, Bdnf, and Creb genes in the raphe nuclei of defeated mice are decreased as compared with the controls. The expression of the serotonergic genes as well as the Creb gene is not restored to the control level after the 2 weeks of relative rest. mRNA levels of Bdnf gene are not recovered to the control levels, although some upregulation was observed in rested losers. CSDS experience inducing the development of mixed anxiety/depression-like state in male mice downregulates the expression of serotonergic genes associated with the synthesis, inactivation, and reception of serotonin. The Bdnf and Creb genes in the midbrain raphe nuclei are also downregulated under CSDS. Period of relative rest is not enough for most serotonergic genes to recover expression to the control levels.

A novel strategy for selection and validation of reference genes in dynamic multidimensional experimental design in yeast

BACKGROUND

Understanding the dynamic mechanism behind the transcriptional organization of genes in response to varying environmental conditions requires time-dependent data. The dynamic transcriptional response obtained by real-time RT-qPCR experiments could only be correctly interpreted if suitable reference genes are used in the analysis. The lack of available studies on the identification of candidate reference genes in dynamic gene expression studies necessitates the identification and the verification of a suitable gene set for the analysis of transient gene expression response.

PRINCIPAL FINDINGS

In this study, a candidate reference gene set for RT-qPCR analysis of dynamic transcriptional changes in Saccharomyces cerevisiae was determined using 31 different publicly available time series transcriptome datasets. Ten of the twelve candidates (TPI1, FBA1, CCW12, CDC19, ADH1, PGK1, GCN4, PDC1, RPS26A and ARF1) we identified were not previously reported as potential reference genes. Our method also identified the commonly used reference genes ACT1 and TDH3. The most stable reference genes from this pool were determined as TPI1, FBA1, CDC19 and ACT1 in response to a perturbation in the amount of available glucose and as FBA1, TDH3, CCW12 and ACT1 in response to a perturbation in the amount of available ammonium. The use of these newly proposed gene sets outperformed the use of common reference genes in the determination of dynamic transcriptional response of the target genes, HAP4 and MEP2, in response to relaxation from glucose and ammonium limitations, respectively.

CONCLUSIONS

A candidate reference gene set to be used in dynamic real-time RT-qPCR expression profiling in yeast was proposed for the first time in the present study. Suitable pools of stable reference genes to be used under different experimental conditions could be selected from this candidate set in order to successfully determine the expression profiles for the genes of interest.

Evaluation of internal reference genes for quantitative expression analysis by real-time PCR in ovine whole blood

The use of reference genes is commonly accepted as the most reliable approach to normalize qRT-PCR and to reduce possible errors in the quantification of gene expression. The most suitable reference genes in sheep have been identified for a restricted range of tissues, but no specific data on whole blood are available. The aim of this study was to identify a set of reference genes for normalizing qRT-PCR from ovine whole blood. We designed 11 PCR assays for commonly employed reference genes belonging to various functional classes and then determined their expression stability in whole blood samples from control and disease-stressed sheep. SDHA and YWHAZ were considered the most suitable internal controls as they were stably expressed regardless of disease status according to both geNorm and NormFinder software; furthermore, geNorm indicated SDHA/HPRT, YWHAZ/GAPDH and SDHA/YWHAZ as the best reference gene combinations in control, disease-stressed and combined sheep groups, respectively. Our study provides a validated panel of optimal control genes which may be useful for the identification of genes differentially expressed by qRT-PCR in a readily accessible tissue, with potential for discovering new physiological and disease markers and as a tool to improve production traits (e.g., by identifying expression Quantitative Trait Loci). An additional outcome of the study is a set of intron-spanning primer sequences suitable for gene expression experiments employing SYBR Green chemistry on other ovine tissues and cells.

DIA1R is an X-linked gene related to Deleted In Autism-1

Background

Autism spectrum disorders (ASDs) are frequently occurring disorders diagnosed by deficits in three core functional areas: social skills, communication, and behaviours and/or interests. Mental retardation frequently accompanies the most severe forms of ASDs, while overall ASDs are more commonly diagnosed in males. Most ASDs have a genetic origin and one gene recently implicated in the etiology of autism is the Deleted-In-Autism-1 (DIA1) gene.

Methodology/Principal Findings

Using a bioinformatics-based approach, we have identified a human gene closely related to DIA1, we term DIA1R (DIA1-Related). While DIA1 is autosomal (chromosome 3, position 3q24), DIA1R localizes to the X chromosome at position Xp11.3 and is known to escape X-inactivation. The gene products are of similar size, with DIA1 encoding 430, and DIA1R 433, residues. At the amino acid level, DIA1 and DIA1R are 62% similar overall (28% identical), and both encode signal peptides for targeting to the secretory pathway. Both genes are ubiquitously expressed, including in fetal and adult brain tissue.

Conclusions/Significance

Examination of published literature revealed point mutations in DIA1R are associated with X-linked mental retardation (XLMR) and DIA1R deletion is associated with syndromes with ASD-like traits and/or XLMR. Together, these results support a model where the DIA1 and DIA1R gene products regulate molecular traffic through the cellular secretory pathway or affect the function of secreted factors, and functional deficits cause disorders with ASD-like symptoms and/or mental retardation.