Maternal and fetal genomes interplay through phosphoinositol 3-kinase(PI3K)-p110α signaling to modify placental resource allocation

Trophoblast-specific Deptor knockdown enhances trophoblast nutrient transport and fetal growth in mice

AIM

Silencing of DEP-domain containing mTOR-interacting protein (DEPTOR), an endogenous inhibitor of the mammalian target of rapamycin (mTOR) pathway, increases mTOR signaling and System A/L amino acid transport activity in cultured primary human trophoblast cells. However, there is no evidence supporting the regulatory role of DEPTOR signaling in placental function in vivo. We hypothesized that trophoblast-specific Deptor knockdown (KD) in mice increases trophoblast mTOR signaling, amino acid transport, and enhances fetal growth.

METHODS

We generated trophoblast-specific DeptorKD transgenic mice, and at embryonic day 18.5, placentas were analyzed to confirm knockdown efficiency, specificity, and mTOR signaling pathway levels. Trophoblast plasma membrane (TPM) System A/L amino acid transport expression and activity were also determined. We also examined the relationship between birthweight and DEPTOR protein levels in human placentas collected at term from appropriate for gestational age (AGA) and large for gestational age (LGA) pregnancies.

RESULTS

Reducing trophoblast Deptor RNA levels increased placental mTOR signaling, System A/L transporter expression/activity, and fetal growth in mice. Similarly, human LGA placentas displayed decreased DEPTOR protein levels, inversely correlated to birthweight and BMI.

CONCLUSIONS

This is the first report showing that trophoblast-specific DeptorKD is sufficient to activate mTOR signaling, a master regulator of placental function, which increases the TPM System A and L amino acid transporter expression and activity. We also propose that Deptor expression is mechanistically linked to placental mTOR signaling and fetal growth. Furthermore, modulation of DEPTOR signaling may represent a promising approach to improve outcomes in pregnancies characterized by abnormal fetal growth.

Integrating Transcriptomics, Proteomics, and Metabolomics to Investigate the Mechanism of Fetal Placental Overgrowth in Somatic Cell Nuclear Transfer Cattle

A major factor limiting the development of somatic cell nuclear transfer (SCNT) technology is the low success rate of pregnancy, mainly due to placental abnormalities disrupting the maternal-fetal balance during pregnancy. Although there has been some progress in research on the abnormal enlargement of cloned bovine placenta, there are still few reports on the direct regulatory mechanisms of enlarged cloned bovine placenta tissue. In this study, we conducted sequencing and analysis of transcriptomics, proteomics, and metabolomics of placental tissues from SCNT cattle (n = 3) and control (CON) cattle (n = 3). The omics analysis results indicate abnormalities in biological functions such as protein digestion and absorption, glycolysis/gluconeogenesis, the regulation of lipid breakdown, as well as glycerolipid metabolism, and arginine and proline metabolism in the placenta of SCNT cattle. Integrating these analyses highlights critical metabolic pathways affecting SCNT cattle placenta, including choline metabolism and unsaturated fatty acid biosynthesis. These findings suggest that aberrant expressions of genes, proteins, and metabolites in SCNT placentas affect key pathways in protein digestion, growth hormone function, and energy metabolism. Our results suggest that abnormal protein synthesis, growth hormone function, and energy metabolism in SCNT bovine placental tissues contribute to placental hypertrophy. These findings offer valuable insights for further investigation into the mechanisms underlying SCNT bovine placental abnormalities.

A genetically small fetus impairs placental adaptations near term

The placenta is a gatekeeper between the mother and fetus, adapting its structure and functions to support optimal fetal growth. Studies exploring adaptations of placentae that support the development of genetically small fetuses are lacking. Here, using a mouse model of impaired fetal growth, achieved by deleting insulin-like growth factor 2 (Igf2) in the epiblast, we assessed placental nutrient transfer and umbilical artery (UA) blood flow during late gestation. At embryonic day (E) 15.5, we observed a decline in the trans-placental flux of glucose and system A amino acids (by using 3H-MeG and 14C-MeAIB), proportionate to the diminished fetal size, whereas UA blood flow was normal. However, at E18.5, the trans-placental flux of both tracers was disproportionately decreased and accompanied by blunted UA blood flow. Feto-placental growth and nutrient transfer were more impaired in female conceptuses. Thus, reducing the fetal genetic demand for growth impairs the adaptations in placental blood flow and nutrient transport that normally support the fast fetal growth during late gestation. These findings have important implications for our understanding of the pathophysiology of pregnancies afflicted by fetal growth restriction.

Sex and fetal genome influence gene expression in pig endometrium at the end of gestation

BACKGROUND

A fine balance of feto-maternal resource allocation is required to support pregnancy, which depends on interactions between maternal and fetal genetic potential, maternal nutrition and environment, endometrial and placental functions. In particular, some imprinted genes have a role in regulating maternal-fetal nutrient exchange, but few have been documented in the endometrium. The aim of this study is to describe the expression of 42 genes, with parental expression, in the endometrium comparing two extreme breeds: Large White (LW); Meishan (MS) with contrasting neonatal mortality and maturity at two days of gestation (D90-D110). We investigated their potential contribution to fetal maturation exploring genes-fetal phenotypes relationships. Last, we hypothesized that the fetal genome and sex influence their endometrial expression. For this purpose, pure and reciprocally crossbred fetuses were produced using LW and MS breeds. Thus, in the same uterus, endometrial samples were associated with its purebred or crossbred fetuses.

RESULTS

Among the 22 differentially expressed genes (DEGs), 14 DEGs were differentially regulated between the two days of gestation. More gestational changes were described in LW (11 DEGs) than in MS (2 DEGs). Nine DEGs were differentially regulated between the two extreme breeds, highlighting differences in the regulation of endometrial angiogenesis, nutrient transport and energy metabolism. We identified DEGs that showed high correlations with indicators of fetal maturation, such as ponderal index at D90 and fetal blood fructose level and placental weight at D110. We pointed out for the first time the influence of fetal sex and genome on endometrial expression at D90, highlighting AMPD3, CITED1 and H19 genes. We demonstrated that fetal sex affects the expression of five imprinted genes in LW endometrium. Fetal genome influenced the expression of four genes in LW endometrium but not in MS endometrium. Interestingly, both fetal sex and fetal genome interact to influence endometrial gene expression.

CONCLUSIONS

These data provide evidence for some sexual dimorphism in the pregnant endometrium and for the contribution of the fetal genome to feto-maternal interactions at the end of gestation. They suggest that the paternal genome may contribute significantly to piglet survival, especially in crossbreeding production systems.

The role of placental aging in adverse pregnancy outcomes: A mitochondrial perspective

Premature placental aging is associated with placental insufficiency, which reduces the functional capacity of the placenta, leading to adverse pregnancy outcomes. Placental mitochondria are vital organelles that provide energy and play essential roles in placental development and functional maintenance. In response to oxidative stress, damage, and senescence, an adaptive response is induced to selectively remove mitochondria through the mitochondrial equivalent of autophagy. However, adaptation can be disrupted when mitochondrial abnormalities or dysfunctions persist. This review focuses on the adaptation and transformation of mitochondria during pregnancy. These changes modify placental function throughout pregnancy and can cause complications. We discuss the relationship between placental aging and adverse pregnancy outcomes from the perspective of mitochondria and potential approaches to improve abnormal pregnancy outcomes.

Maternal and Intrauterine Influences on Feto-Placental Growth Are Accompanied by Sexually Dimorphic Changes in Placental Mitochondrial Respiration, and Metabolic Signalling Pathways

Adverse maternal environments such as small size, malnutrition, and metabolic conditions are known to influence fetal growth outcomes. Similarly, fetal growth and metabolic alterations may alter the intrauterine environment and affect all fetuses in multiple gestation/litter-bearing species. The placenta is the site of convergence between signals derived from the mother and the developing fetus/es. Its functions are fuelled by energy generated by mitochondrial oxidative phosphorylation (OXPHOS). The aim of this study was to delineate the role of an altered maternal and/or fetal/intrauterine environment in feto-placental growth and placental mitochondrial energetic capacity. To address this, in mice, we used disruptions of the gene encoding phosphoinositol 3-kinase (PI3K) p110α, a growth and metabolic regulator to perturb the maternal and/or fetal/intrauterine environment and study the impact on wildtype conceptuses. We found that feto-placental growth was modified by a perturbed maternal and intrauterine environment, and effects were most evident for wildtype males compared to females. However, placental mitochondrial complex I+II OXPHOS and total electron transport system (ETS) capacity were similarly reduced for both fetal sexes, yet reserve capacity was additionally decreased in males in response to the maternal and intrauterine perturbations. These were also sex-dependent differences in the placental abundance of mitochondrial-related proteins (e.g., citrate synthase and ETS complexes), and activity of growth/metabolic signalling pathways (AKT and MAPK) with maternal and intrauterine alterations. Our findings thus identify that the mother and the intrauterine environment provided by littermates modulate feto-placental growth, placental bioenergetics, and metabolic signalling in a manner dependent on fetal sex. This may have relevance for understanding the pathways leading to reduced fetal growth, particularly in the context of suboptimal maternal environments and multiple gestation/litter-bearing species.

Placental adaptations supporting fetal growth during normal and adverse gestational environments

NEW FINDINGS

What is the topic of this review? How the placenta, which transports nutrients and oxygen to the fetus, may alter its support of fetal growth developmentally and with adverse gestational conditions. What advances does it highlight? Placental formation and function alter with the needs of the fetus for substrates for growth during normal gestation and when there is enhanced competition for substrates in species with multiple gestations or adverse gestational environments, and this is mediated by imprinted genes, signalling pathways, mitochondria and fetal sexomes.

ABSTRACT

The placenta is vital for mammalian development and a key determinant of life-long health. It is the interface between the mother and fetus and is responsible for transporting the nutrients and oxygen a fetus needs to develop and grow. Alterations in placental formation and function, therefore, have consequences for fetal growth and birthweight, which in turn determine perinatal survival and risk of non-communicable diseases for the offspring in later postnatal life. However, the placenta is not a static organ. As this review summarizes, research from multiple species has demonstrated that placental formation and function alter developmentally to the needs of the fetus for substrates for growth during normal gestation, as well as when there is greater competition for substrates in polytocous species and monotocous species with multiple gestations. The placenta also adapts in response to the gestational environment, integrating information about the ability of the mother to provide nutrients and oxygen with the needs of the fetus in that prevailing environment. In particular, placental structure (e.g. vascularity, surface area, blood flow, diffusion distance) and transport capacity (e.g. nutrient transporter levels and activity) respond to suboptimal gestational environments, namely malnutrition, obesity, hypoxia and maternal ageing. Mechanisms mediating developmentally and environmentally induced homeostatic responses of the placenta that help support normal fetal growth include imprinted genes, signalling pathways, subcellular constituents and fetal sexomes. Identification of these placental strategies may inform the development of therapies for complicated human pregnancies and advance understanding of the pathways underlying poor fetal outcomes and their consequences for health and disease risk.

Characterization of placental endocrine function and fetal brain development in a mouse model of small for gestational age

Conditions such as small for gestational age (SGA), which is defined as birthweight less than 10th percentile for gestational age can predispose to neurodevelopmental abnormalities compared to babies with normal birthweight. Fetal growth and birthweight depend on placental function, as this organ transports substrates to the developing fetus and it acts as a source of endocrine factors, including steroids and prolactins that are required for fetal development and pregnancy maintenance. To advance our knowledge on the aetiology of fetal growth disorders, the vast majority of the research has been focused on studying the transport function of the placenta, leaving practically unexplored the contribution of placental hormones in the regulation of fetal growth. Here, using mice and natural variability in fetal growth within the litter, we compared fetuses that fell on or below the 10th percentile (classified as SGA) with those that had adequate weight for their gestational age (AGA). In particular, we compared placental endocrine metabolism and hormone production, as well as fetal brain weight and expression of developmental, growth and metabolic genes between SGA and AGA fetuses. We found that compared to AGA fetuses, SGA fetuses had lower placental efficiency and reduced capacity for placental production of hormones (e.g. steroidogenic gene Cyp17a1, prolactin Prl3a1, and pregnancy-specific glycoproteins Psg21). Brain weight was reduced in SGA fetuses, although this was proportional to the reduction in overall fetal size. The expression of glucose transporter 3 (Slc2a3) was reduced despite the abundance of AKT, FOXO and ERK proteins were similar. Developmental (Sv2b and Gabrg1) and microglia genes (Ier3), as well as the pregnancy-specific glycoprotein receptor (Cd9) were lower in the brain of SGA versus AGA fetuses. In this mouse model of SGA, our results therefore demonstrate that placental endocrine dysfunction is associated with changes in fetal growth and fetal brain development.

The leptin receptor gene affects piglet behavior and growth

Piglets with low birth weight present low vitality after farrowing, often leading to impaired weight gain during lactation. A recessive missense variant (C > T) for increased appetite and fatness in the porcine leptin receptor gene (rs709596309) causes a negative maternal effect on the weight of piglets at weaning. However, it is not known whether this variant already exerts an effect on the birth weight and vitality of newborn piglets and on their growing capacity during lactation. An experiment was conducted using 668 purebred Duroc piglets (131 CC, 311 CT, and 226 TT) from 74 multiparous sows (9 CC, 43 CT, and 22 TT) and 14 boars (1 CC, 10 CT, and 3 TT). All piglets were individually weighed at birth and tested for vitality, which was assessed on a scale from 1 (low vitality) to 3 (high vitality) based on behavioral observations, including the status of the piglet immediately before the test. Only non-adopted piglets were considered for piglet performance at weaning. Inferences on the effect of the genotype on birth and weaning traits were done on a Bayesian setting based on 2-trait bivariate models including the effects of the piglet and the litter, as well as the genotype of the sow and the piglet, the sex of the piglet, and the parity number. Vitality and the status of the piglet before the test were analyzed using a liability threshold (probit) model. As compared to other genotypes, TT newborn piglets were 28 g heavier, were more vital (the probability of being scored as highly vital was 6.5% higher) and were more often found suckling before the test (the probability of being suckling at test was 6.5% higher). As a result, they grew more during lactation (153 g) and were heavier at weaning (169 g) than littermates of the two other genotypes, thus partly compensating for the limited maternal capacity of TT sows. Our findings provide evidence that appetite-influencing genes, such as the leptin receptor gene, have developmental implications from very early life stages.

Regulators involved in trophoblast syncytialization in the placenta of intrauterine growth restriction

Placental dysfunction refers to the insufficiency of placental perfusion and chronic hypoxia during early pregnancy, which impairs placental function and causes inadequate supply of oxygen and nutrients to the fetus, affecting fetal development and health. Fetal intrauterine growth restriction, one of the most common outcomes of pregnancy-induced hypertensions, can be caused by placental dysfunction, resulting from deficient trophoblast syncytialization, inadequate trophoblast invasion and impaired vascular remodeling. During placental development, cytotrophoblasts fuse to form a multinucleated syncytia barrier, which supplies oxygen and nutrients to meet the metabolic demands for fetal growth. A reduction in the cell fusion index and the number of nuclei in the syncytiotrophoblast are found in the placentas of pregnancies complicated by IUGR, suggesting that the occurrence of IUGR may be related to inadequate trophoblast syncytialization. During the multiple processes of trophoblasts syncytialization, specific proteins and several signaling pathways are involved in coordinating these events and regulating placental function. In addition, epigenetic modifications, cell metabolism, senescence, and autophagy are also involved. Study findings have indicated several abnormally expressed syncytialization-related proteins and signaling pathways in the placentas of pregnancies complicated by IUGR, suggesting that these elements may play a crucial role in the occurrence of IUGR. In this review, we discuss the regulators of trophoblast syncytialization and their abnormal expression in the placentas of pregnancies complicated by IUGR.

Human placental development and function

The placenta is a transient fetal organ that plays a critical role in the health and wellbeing of both the fetus and its mother. Functionally, the placenta sustains the growth of the fetus as it facilitates delivery of oxygen and nutrients and removal of waste products. Not surprisingly, defective early placental development is the primary cause of common disorders of pregnancy, including recurrent miscarriage, fetal growth restriction, pre-eclampsia and stillbirth. Adverse pregnancy conditions will also affect the life-long health of the fetus via developmental programming[1]. Despite its critical importance in reproductive success and life-long health, our understanding of placental development is not extensive, largely due to ethical limitations to studying early or chronological placental development, lack of long-term in vitro models, or comparative animal models. In this review, we examine current knowledge of early human placental development, discuss the critical role of the maternal endometrium and of the fetal-maternal dialogue in pregnancy success, and we explore the latest models of trophoblast and endometrial stem cells. In addition, we discuss the role of oxygen in placental formation and function, how nutrient delivery is mediated during the periods of histotrophic nutrition (uptake of uterine secretions) and haemotrophic nutrition (exchange between the maternal and fetal circulations), and how placental endocrine function facilitates fetal growth and development.

Sex-Selective Increase of IGF-2 Expression in the Hypoxic Guinea Pig Placenta of Growth-Restricted Fetuses

Chronic hypoxia can cause fetal growth restriction (FGR) through placental dysfunction. Insulin-like growth factors (IGFs), such as IGF-2, play a major role in preservation of placental growth and function. We investigated the effects of chronic hypoxia and sex on protein expression of the IGF-2 pathway in placentas selected from asymmetric-FGR fetuses. Time-mated pregnant guinea pigs were assigned to normoxia (NMX, 21% O2) or hypoxia (HPX, 10.5% O2) during the last 14 days of pregnancy. Placentas were selected from male and female symmetrically grown NMX fetuses (fetal wt between 25th ile-75th ile) and HPX fetuses of asymmetric-FGR (fetal wt < 25th ile and brain:liver wt > 50th ile). Effects of HPX and sex on placenta protein expression of the IGF-2 signaling proteins (IGF-2, PI3K, AKT-P, total AKT, PCNA, a cell proliferation marker) were evaluated by immunoblotting. Effects of HPX and sex on morphometric parameters were analyzed using two-way ANOVA (p < 0.05). HPX reduced (p < 0.005) fetal wt by ~ 35% compared to NMX in both sexes. Expression of IGF-2 was lower (p = 0.029) in NMX female placentas compared to males. Despite lower NMX levels, HPX increased (p < 0.05) expression of IGF-2, AKT-P, relative AKT-P, and PCNA in female placentas only and had no effect on protein expression in male placentas. The female guinea pig placenta exhibits a greater sensitivity than males to HPX in upregulating expression of the IGF-2 axis. In addition, the sex difference in baseline IGF-2 expression suggests a greater capacity for females to increase IGF-2 in response to HPX as a placental adaptation in FGR.

Maternal and Fetal PI3K-p110α Deficiency Induces Sex-Specific Changes in Conceptus Growth and Placental Mitochondrial Bioenergetic Reserve in Mice

Fetal growth is reliant on placental formation and function, which, in turn, requires the energy produced by the mitochondria. Prior work has shown that both mother and fetus operate via the phosphoinositol 3-kinase (PI3K)-p110α signalling pathway to modify placental development, function, and fetal growth outcomes. This study in mice used genetic inactivation of PI3K-p110α (α/+) in mothers and fetuses and high resolution respirometry to investigate the influence of maternal and fetal PI3K-p110α deficiency on fetal and placental growth, in relation to placental mitochondrial bioenergetics, for each fetal sex. The effect of PI3K-p110α deficiency on maternal body composition was also determined to understand more about the maternal-driven changes in feto-placental development. These data show that male fetuses were more sensitive than females to fetal PI3K-p110α deficiency, as they had greater reductions in fetal and placental weight, when compared to their WT littermates. Placental weight was also altered in males only of α/+ dams. In addition, α/+ male, but not female, fetuses showed an increase in mitochondrial reserve capacity, when compared to their WT littermates in α/+ dams. Finally, α/+ dams exhibited reduced adipose depot masses, compared to wild-type dams. These findings, thus, demonstrate that maternal nutrient reserves and ability to apportion nutrients to the fetus are reduced in α/+ dams. Moreover, maternal and fetal PI3K-p110α deficiency impacts conceptus growth and placental mitochondrial bioenergetic function, in a manner dependent on fetal sex.

MAP3K4 promotes fetal and placental growth by controlling the receptor tyrosine kinases IGF1R/IR and Akt signaling pathway†

Disruption of fetal growth results in severe consequences to human health, including increased fetal and neonatal morbidity and mortality, as well as potential lifelong health problems. Molecular mechanisms promoting fetal growth represent potential therapeutic strategies to treat and/or prevent fetal growth restriction (FGR). Here, we identify a previously unknown role for the mitogen-activated protein kinase kinase kinase 4 (MAP3K4) in promoting fetal and placental growth. We demonstrate that inactivation of MAP3K4 kinase activity causes FGR due in part to placental insufficiency. Significantly, MAP3K4 kinase–inactive mice display highly penetrant lethality prior to weaning and persistent growth reduction of surviving adults. Additionally, we elucidate molecular mechanisms by which MAP3K4 promotes growth through control of the insulin-like growth factor 1 receptor (IGF1R), insulin receptor (IR), and Akt signaling pathway. Specifically, MAP3K4 kinase inactivation in trophoblast stem (TS) cells results in reduced IGF1R and IR expression and decreased Akt activation. We observe these changes in TS cells also occur in differentiated trophoblasts created through in vitro differentiation of cultured TS cells and in vivo in placental tissues formed by TS cells. Furthermore, we show that MAP3K4 controls this pathway by promoting Igf1r transcript expression in TS cells through activation of CREB-binding protein (CBP). In the MAP3K4 kinase–inactive TS cells, Igf1r transcripts are repressed because of reduced CBP activity and increased histone deacetylase 6 expression and activity. Together, these data demonstrate a critical role for MAP3K4 in promoting fetal and placental growth by controlling the activity of the IGF1R/IR and Akt signaling pathway.

Ablation of PI3K-p110alpha Impairs Maternal Metabolic Adaptations to Pregnancy

Pregnancy requires adaptations in maternal metabolism to support fetal growth. The phosphoinositol-3-kinase (PI3K) signalling pathway controls multiple biological processes and defects in this pathway are linked to metabolic disorders including insulin resistance and glucose intolerance in non-pregnant animals. However, relatively little is known about the contribution of PI3K signalling to the maternal metabolic adaptations during pregnancy. Using mice with partial inactivation of the PI3K isoform, p110α (due to a heterozygous dominant negative mutation; Pik3ca-D933A), the effects of impaired PI3K-p110α signalling on glucose and insulin handling were examined in the pregnant and non-pregnant states and related to the morphological, molecular, and mitochondrial changes in key metabolic organs. The results show that non-pregnant mice lacking PI3K-p110α are glucose intolerant but exhibit compensatory increases in pancreatic glucose-stimulated insulin release and adipose tissue mitochondrial respiratory capacity and fatty acid oxidation. However, in pregnancy, mutant mice failed to show the normal increment in glucose intolerance and pancreatic β-cell mass observed in wild-type pregnant dams and exhibited further enhanced adipose tissue mitochondrial respiratory capacity. These maladaptations in pregnant mutant mice were associated with fetal growth restriction. Hence, PI3K-p110α is a key regulator of metabolic adaptations that support fetal growth during normal pregnancy.

Maternal gut microbiota Bifidobacterium promotes placental morphogenesis, nutrient transport and fetal growth in mice

The gut microbiota plays a central role in regulating host metabolism. While substantial progress has been made in discerning how the microbiota influences host functions post birth and beyond, little is known about how key members of the maternal gut microbiota can influence feto-placental growth. Notably, in pregnant women, Bifidobacterium represents a key beneficial microbiota genus, with levels observed to increase across pregnancy. Here, using germ-free and specific-pathogen-free mice, we demonstrate that the bacterium Bifidobacterium breve UCC2003 modulates maternal body adaptations, placental structure and nutrient transporter capacity, with implications for fetal metabolism and growth. Maternal and placental metabolome were affected by maternal gut microbiota (i.e. acetate, formate and carnitine). Histological analysis of the placenta confirmed that Bifidobacterium modifies placental structure via changes in Igf2P0, Dlk1, Mapk1 and Mapk14 expression. Additionally, B. breve UCC2003, acting through Slc2a1 and Fatp1-4 transporters, was shown to restore fetal glycaemia and fetal growth in association with changes in the fetal hepatic transcriptome. Our work emphasizes the importance of the maternal gut microbiota on feto-placental development and sets a foundation for future research towards the use of probiotics during pregnancy.

Loss of imprinting of the Igf2-H19 ICR1 enhances placental endocrine capacity via sex-specific alterations in signalling pathways in the mouse

Imprinting control region (ICR1) controls the expression of the Igf2 and H19 genes in a parent-of-origin specific manner. Appropriate expression of the Igf2-H19 locus is fundamental for normal fetal development, yet the importance of ICR1 in the placental production of hormones that promote maternal nutrient allocation to the fetus is unknown. To address this, we used a novel mouse model to selectively delete ICR1 in the endocrine junctional zone (Jz) of the mouse placenta (Jz-ΔICR1). The Jz-ΔICR1 mice exhibit increased Igf2 and decreased H19 expression specifically in the Jz. This was accompanied by an expansion of Jz endocrine cell types due to enhanced rates of proliferation and increased expression of pregnancy-specific glycoprotein 23 in the placenta of both fetal sexes. However, changes in the endocrine phenotype of the placenta were related to sexually-dimorphic alterations to the abundance of Igf2 receptors and downstream signalling pathways (Pi3k-Akt and Mapk). There was no effect of Jz-ΔICR1 on the expression of targets of the H19-embedded miR-675 or on fetal weight. Our results demonstrate that ICR1 controls placental endocrine capacity via sex-dependent changes in signalling.

Placental adaptations in a nonhuman primate model of gestational protein restriction

We previously demonstrated decreased placental perfusion, reduced amniotic fluid protein content, and increased pregnancy loss in a nonhuman primate model of gestational protein restriction. Here, our objective was to link these detrimental findings with a functional placental assessment. As blood flow is critical to maternal-fetal exchange, we hypothesized that a protein-restricted diet would impair placental taurine uptake. Pregnant rhesus macaques were maintained on either control chow (CON, n = 5), a 33% protein-restricted diet (PR33, n = 5), or a 50% PR diet (PR50, n = 5) prior to and throughout pregnancy. Animals were delivered on gestational day 135 (G135; term is G168). Taurine activity was determined in fresh placental villous explants. Taurine transporter (TauT) protein expression, placental growth factor (PLGF), and insulin-like growth factor (IGF)-1 and IGF-2 protein concentrations were measured, and histological assessment was performed. Fetal body weights and placental weights were comparable between all three groups at G135. Placental taurine uptake was decreased in PR33- and PR50-fed animals compared to CON, yet TauT expression was unchanged across groups. PLGF was significantly increased in PR50 vs. CON, with no change in IGF-1 or IGF-2 expression in placental homogenate from PR-fed animals. Accelerated villous maturation was observed in all PR50 cases, three of five PR33, and was absent in CON. We demonstrate conserved fetal growth, despite a decrease in placental taurine uptake. Increased expression of PLGF and expansion of the syncytiotrophoblast surface area in the severely protein-restricted animals suggest a compensatory mechanism by the placenta to maintain fetal growth.

Human Placental Transcriptome Reveals Critical Alterations in Inflammation and Energy Metabolism with Fetal Sex Differences in Spontaneous Preterm Birth

A well-functioning placenta is crucial for normal gestation and regulates the nutrient, gas, and waste exchanges between the maternal and fetal circulations and is an important endocrine organ producing hormones that regulate both the maternal and fetal physiologies during pregnancy. Placental insufficiency is implicated in spontaneous preterm birth (SPTB). We proposed that deficits in the capacity of the placenta to maintain bioenergetic and metabolic stability during pregnancy may ultimately result in SPTB. To explore our hypothesis, we performed a RNA-seq study in male and female placentas from women with SPTB (<36 weeks gestation) compared to normal pregnancies (≥38 weeks gestation) to assess the alterations in the gene expression profiles. We focused exclusively on Black women (cases and controls), who are at the highest risk of SPTB. Six hundred and seventy differentially expressed genes were identified in male SPTB placentas. Among them, 313 and 357 transcripts were increased and decreased, respectively. In contrast, only 61 differentially expressed genes were identified in female SPTB placenta. The ingenuity pathway analysis showed alterations in the genes and canonical pathways critical for regulating inflammation, oxidative stress, detoxification, mitochondrial function, energy metabolism, and the extracellular matrix. Many upstream regulators and master regulators important for nutrient-sensing and metabolism were also altered in SPTB placentas, including the PI3K complex, TGFB1/SMADs, SMARCA4, TP63, CDKN2A, BRCA1, and NFAT. The transcriptome was integrated with published human placental metabolome to assess the interactions of altered genes and metabolites. Collectively, significant and biologically relevant alterations in the transcriptome were identified in SPTB placentas with fetal sex disparities. Altered energy metabolism, mitochondrial function, inflammation, and detoxification may underly the mechanisms of placental dysfunction in SPTB.

Growth impairment, increased placental glucose uptake and altered transplacental transport in VIP deficient pregnancies: Maternal vs. placental contributions

Glucose uptake by the placenta and its transfer to the fetus is a finely regulated process required for placental and fetal development. Deficient placentation is associated with pregnancy complications such as fetal growth restriction (FGR). The vasoactive intestinal peptide (VIP) has embryotrophic effects in mice and regulates human cytotrophoblast metabolism and function. Here we compared glucose uptake and transplacental transport in vivo by VIP-deficient placentas from normal or VIP-deficient maternal background. The role of endogenous VIP in placental glucose and amino acid uptake was also investigated. Wild type C57BL/6 (WT) or VIP^+/- (VIP HT) females were mated with WT, VIP knock-out (VIP KO) or VIP HT males. Glucose uptake and transplacental transport were evaluated by the injection of the fluorescent d-glucose analogue 2-NBDG in pregnant mice at gestational day (gd) 17.5. Glucose and amino acid uptake in vitro by placental explants were measured with 2-NBDG or ¹⁴C-MeAIB respectively. In normal VIP maternal background, fetal weight was reduced in association with placental VIP deficiency, whereas placental weight was unaltered. Paradoxically, VIP^+/- placentas presented higher glucose uptake and higher gene expression of GLUT1 and mTOR than VIP^+/+ placentas. However, in a maternal VIP-deficient environment placental uptake and transplacental transport of glucose increased while fetal weights were unaffected, regardless of feto-placental genotype. Results point to VIP-deficient pregnancy in a normal background as a suitable FGR model with increased placental glucose uptake and transplacental transport. The apparently compensatory actions are unable to sustain normal fetal growth and could result in complications later in life.

Placental hypoxia: What have we learnt from small animal models?

Intrauterine hypoxia is a feature of pregnancy complications, both at high altitude and sea level. To understand the placental response to reduced oxygen availability, small animal models of maternal inhalation hypoxia (MIH) or reduced uterine perfusion pressure (RUPP) may be utilised. The aim of this review was to compare the findings of those studies to identify the role of oxygen availability in adapting placental structural and functional phenotypes in relation to fetal outcome. It also sought to explore the evidence for the involvement of particular genes and protein signalling pathways in the placenta in mediating hypoxia driven alterations. The data available demonstrate that both MIH and RUPP can induce placental hypoxia, which affects placental structure and vascularity, as well as glucose, amino acid, calcium and possibly lipid transport capacity. In addition, changes have been observed in HIF, VEGF, insulin/IGF2, AMPK, mTOR, PI3K and PPARγ signalling, which may be key in linking together observed phenotypes under conditions of placental hypoxia. Many different manipulations have been examined, with varied outcomes depending on the intensity, timing and duration of the insult. Some manipulations have detrimental effects on placental phenotype, viability and fetal growth, whereas in others, the placenta appears to adapt to uphold fetal growth despite the challenge of low oxygen. Together these data suggest a complex response of the placenta to reduced oxygen availability, which links to changes in fetal outcomes. However, further work is required to explore the role of fetal sex, altered maternal physiology and placental molecular mechanisms to fully understand placental responses to hypoxia and their relevance for pregnancy outcome.

Innovative approach to identify multigenomic and environmental interactions associated with birth defects in family-based hybrid designs

Genes, including those with transgenerational effects, work in concert with behavioral, environmental, and social factors via complex biological networks to determine human health. Understanding complex relationships between causal factors underlying human health is an essential step towards deciphering biological mechanisms. We propose a new analytical framework to investigate the interactions between maternal and offspring genetic variants or their surrogate single nucleotide polymorphisms (SNPs) and environmental factors using family-based hybrid study design. The proposed approach can analyze diverse genetic and environmental factors and accommodate samples from a variety of family units, including case/control-parental triads, and case/control-parental dyads, while minimizing potential bias introduced by population admixture. Comprehensive simulations demonstrated that our innovative approach outperformed the log-linear approach, the best available method for case-control family data. The proposed approach had greater statistical power and was capable to unbiasedly estimate the maternal and child genetic effects and the effects of environmental factors, while controlling the Type I error rate against population stratification. Using our newly developed approach, we analyzed the associations between maternal and fetal SNPs and obstructive and conotruncal heart defects, with adjustment for demographic and lifestyle factors and dietary supplements. Fourteen and 11 fetal SNPs were associated with obstructive and conotruncal heart defects, respectively. Twenty-seven and 17 maternal SNPs were associated with obstructive and conotruncal heart defects, respectively. In addition, maternal body mass index was a significant risk factor for obstructive defects. The proposed approach is a powerful tool for interrogating the etiological mechanism underlying complex traits.

Evaluation of key miRNAs during early pregnancy in Kazakh horse using RNA sequencing

Background

miRNA has an important role in cell differentiation, biological development, and physiology. Milk production is an important quantitative trait in livestock and miRNA plays a role in the amount of milk produced.

Methods

The role of regulatory miRNAs involved in equine milk production is not fully understood. We constructed two miRNA libraries for Kazakh horse milk production from higher-producing (H group) and lower-producing (L group) individuals, and used RNA-Seq technology to identify the differentially expressed miRNAs between the two milk phenotypes of Kazakh horses.

Results

A total of 341 known and 333 novel miRNAs were detected from the H and L groups, respectively. Eighty-three differentially expressed miRNAs were identified between the H and L group s, of which 32 were known miRNAs (27 were up-regulated, five were down-regulated) and 51 were novel miRNAs (nine were up-regulated, 42 were down-regulated). A total of 2,415 genes were identified. The Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses showed that these genes were annotated to mammary gland development, mammary gland morphogenesis, tissue development and PI3K-Akt signaling pathways, insulin signaling pathway and TGF-beta signaling pathway, among others. Five miRNAs (miR-199a-3p, miR143, miR145, miR221, miR486-5p) were identified as affecting horse milk production and these five miRNAs were validated using qRT-PCR.

Conclusions

We described a methodology for the transcriptome-wide profiling of miRNAs in milk, which may help the design of new intervention strategies to improve the milk yield of Kazakh horses.

Reproductive health research in Australia and New Zealand: highlights from the Annual Meeting of the Society for Reproductive Biology, 2019

The 2019 meeting of the Society for Reproductive Biology (SRB) provided a platform for the dissemination of new knowledge and innovations to improve reproductive health in humans, enhance animal breeding efficiency and understand the effect of the environment on reproductive processes. The effects of environment and lifestyle on fertility and animal behaviour are emerging as the most important modern issues facing reproductive health. Here, we summarise key highlights from recent work on endocrine-disrupting chemicals and diet- and lifestyle-induced metabolic changes and how these factors affect reproduction. This is particularly important to discuss in the context of potential effects on the reproductive potential that may be imparted to future generations of humans and animals. In addition to key summaries of new work in the male and female reproductive tract and on the health of the placenta, for the first time the SRB meeting included a workshop on endometriosis. This was an important opportunity for researchers, healthcare professionals and patient advocates to unite and provide critical updates on efforts to reduce the effect of this chronic disease and to improve the welfare of the women it affects. These new findings and directions are captured in this review.

Placental mitochondrial function in response to gestational exposures

Poor environmental conditions, including malnutrition, hypoxia and obesity in the mother increase the risk of pregnancy complications, such as pre-eclampsia and gestational diabetes mellitus, which impacts the lifelong health of the mother and her offspring. The placenta plays an important role in determining pregnancy outcome by acting as an exchange interface and endocrine hub to support fetal growth. Mitochondria are energy powerhouses of cells that fuel placental physiology throughout pregnancy, including placental development, substrate exchange and hormone secretion. They are responsive to environmental cues and changes in mitochondrial function may serve to mediate or mitigate the impacts of poor gestational environments on placental physiology and hence, the risks of pregnancy complications. Thus, a more integrated understanding about the role of placental mitochondria in orchestrating changes in relation to environmental conditions and pregnancy outcome is paramount. This review summarises the functions of mitochondria in the placenta and findings from humans and experimental animals that demonstrate how mitochondrial structure and function are altered in different gestational environments (namely complicated pregnancies and adverse environmental conditions). Together the available data suggest that mitochondria in the placenta play a major role in determining placental physiology, fetal growth and pregnancy outcome.

Intrauterine Inflammation Alters the Transcriptome and Metabolome in Placenta

Placental insufficiency is implicated in spontaneous preterm birth (SPTB) associated with intrauterine inflammation. We hypothesized that intrauterine inflammation leads to deficits in the capacity of the placenta to maintain bioenergetic and metabolic stability during pregnancy ultimately resulting in SPTB. Using a mouse model of intrauterine inflammation that leads to preterm delivery, we performed RNA-seq and metabolomics studies to assess how intrauterine inflammation alters gene expression and/or modulates metabolite production and abundance in the placenta. 1871 differentially expressed genes were identified in LPS-exposed placenta. Among them, 1,149 and 722 transcripts were increased and decreased, respectively. Ingenuity pathway analysis showed alterations in genes and canonical pathways critical for regulating oxidative stress, mitochondrial function, metabolisms of glucose and lipids, and vascular reactivity in LPS-exposed placenta. Many upstream regulators and master regulators important for nutrient-sensing and mitochondrial function were also altered in inflammation exposed placentae, including STAT1, HIF1α, mTOR, AMPK, and PPARα. Comprehensive quantification of metabolites demonstrated significant alterations in the glucose utilization, metabolisms of branched-chain amino acids, lipids, purine and pyrimidine, as well as carbon flow in TCA cycle in LPS-exposed placenta compared to control placenta. The transcriptome and metabolome were also integrated to assess the interactions of altered genes and metabolites. Collectively, significant and biologically relevant alterations in the placenta transcriptome and metabolome were identified in placentae exposed to intrauterine inflammation. Altered mitochondrial function and energy metabolism may underline the mechanisms of inflammation-induced placental dysfunction.

Advances in imaging feto-placental vasculature: new tools to elucidate the early life origins of health and disease

Optimal placental function is critical for fetal development, and therefore a crucial consideration for understanding the developmental origins of health and disease (DOHaD). The structure of the fetal side of the placental vasculature is an important determinant of fetal growth and cardiovascular development. There are several imaging modalities for assessing feto-placental structure including stereology, electron microscopy, confocal microscopy, micro-computed tomography, light-sheet microscopy, ultrasonography and magnetic resonance imaging. In this review, we present current methodologies for imaging feto-placental vasculature morphology ex vivo and in vivo in human and experimental models, their advantages and limitations and how these provide insight into placental function and fetal outcomes. These imaging approaches add important perspective to our understanding of placental biology and have potential to be new tools to elucidate a deeper understanding of DOHaD.

Maternal L-proline supplementation enhances fetal survival, placental development, and nutrient transport in mice†

L-Proline (proline) in amniotic fluid was markedly increased during pregnancy in both pigs and sheep. However, in vivo data to support a beneficial effect of proline on fetal survival are not available. In this study, pregnant C57BL/6J mice were fed a purified diet supplemented with or without 0.50% proline from embryonic day 0.5 (E0.5) to E12.5 or term. Results indicated that dietary supplementation with proline to gestating mice enhanced fetal survival, reproductive performance, the concentrations of proline, arginine, aspartic acid, and tryptophan in plasma and amniotic fluid, while decreasing the concentrations of ammonia and urea in plasma and amniotic fluid. Placental mRNA levels for amino acid transporters, including Slc36a4, Slc38a2, Slc38a4, Slc6a14, and Na+/K+ ATPase subunit-1α (Atp1a1), fatty acid transporter Slc27a4, and glucose transporters Slc2a1 and Slc2a3, were augmented in proline-supplemented mice, compared with the control group. Histological analysis showed that proline supplementation enhanced labyrinth zone in the placenta of mice at E12.5, mRNA levels for Vegf, Vegfr, Nos2, and Nos3, compared with the controls. Western blot analysis showed that proline supplementation increased protein abundances of phosphorylated (p)-mTORC1, p-ribosomal protein S6 kinase (p70S6K), and p-eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP1), as well as the protein level of GCN2 (a negative regulator of mTORC1 signaling). Collectively, our results indicate a novel functional role of proline in improving placental development and fetal survival by enhancing placental nutrient transport, angiogenesis, and protein synthesis.

Double-label immunohistochemistry to assess labyrinth structure of the mouse placenta with stereology

In mice, the labyrinth zone of the placenta exchanges nutrients and gases between mother and fetus. This placental zone is complex in structure and defects in its morphogenesis can compromise substrate exchange and thus, fetal growth and viability. Numerous mouse models involving genetic and environmental manipulation show abnormalities in labyrinth zone size. However, further structural analysis, normally undertaken using ultrathin resin sections, can pose practical constraints. Here, we validate the use of stereology on paraffin-embedded sections double-labelled for lectin and cytokeratin as a cheap, fast and robust alternative for analysing the structure of the mouse placental labyrinth.

Exploring the causes and consequences of maternal metabolic maladaptations during pregnancy: Lessons from animal models

Pregnancy is a remarkable physiological state, during which the metabolic system of the mother adapts to ensure that nutrients are made available for transfer to the fetus for growth and development. Adaptations of maternal metabolism during pregnancy are influenced by the metabolic and nutritional status of the mother and the production of endocrine factors by the placenta that exert metabolic effects. Insufficient or inappropriate adaptations in maternal metabolism during pregnancy may lead to pregnancy complications with important short- and long-term effects for both the health of the child and mother. This is very evident in gestational diabetes, which is marked by greater glucose intolerance and insulin resistance above that expected of a normal pregnancy. Gestational diabetes is associated with increased fetal weight and/or increased adiposity, higher instrumented delivery rates and greater risks for both mother and child of developing type 2 diabetes in the long-term. However, despite the negative health impacts of such metabolic imbalances during pregnancy, the precise mechanisms responsible for orchestrating these changes remain largely unknown. The present review describes the dynamic pregnancy-specific changes that occur in the metabolic system of the mother during pregnancy. It also discusses findings using surgical, pharmacological, genetic and dietary methods in experimental animals that highlight the role of pathways in maternal tissues that lead to metabolic dysfunction, with a particular focus on gestational diabetes. Finally, it summarises the work largely employing gene targeting and hormone administration in rodents that have illuminated the involvement of placental endocrine function in driving maternal metabolic adaptations. While current animal models may not fully replicate what is observed in humans, these have been instrumental in showing that there is a dynamic interplay between changes in maternal metabolic physiology and the placental production of endocrine factors that govern the availability of nutrients to the growing fetus. However, more work is required to specifically identify the placenta-driven changes in maternal metabolic physiology that ensure the appropriate level of insulin production and action during pregnancy. In doing so, these studies may pave the way to understanding the development of pregnancy complications like gestational diabetes, as well as further our understanding of type-2 diabetes and the control of metabolic physiology more broadly.

Advanced maternal age compromises fetal growth and induces sex-specific changes in placental phenotype in rats

Advanced maternal age is associated with an increased risk of pregnancy complications. It programmes sex-specific cardiovascular dysfunction in rat offspring, however the intrauterine mechanisms involved remain unknown. This study in the rat assessed the impact of advanced maternal age on placental phenotype in relation to the growth of female and male fetuses. We show that relative to young (3-4 months) dams, advanced maternal age (9.5-10 months) compromises growth of both female and male fetuses but affects the placental phenotype sex-specifically. In placentas from aged versus young dams, the size of the placental transport and endocrine zones were increased and expression of Igf2 (+41%) and placental lactogen (Prl3b1: +59%) genes were upregulated in female, but not male fetuses. Placental abundance of IGF2 protein also decreased in the placenta of males only (-95%). Moreover, in placentas from aged versus young dams, glucocorticoid metabolism (11β-hsd2: +63% and 11β-hsd1: -33%) was higher in females, but lower in males (11β-hsd2: -50% and 11β-hsd1: unaltered). There was however, no change in the placental abundance of 11β-HSD2 protein in aged versus young dams regardless of fetal sex. Levels of oxidative stress in the placenta were increased in female and male fetuses (+57% and +90%, respectively) and apoptosis increased specifically in the placenta of males from aged rat dams (+700%). Thus, advanced maternal age alters placental phenotype in a sex-specific fashion. These sexually-divergent changes may play a role in determining health outcomes of female and male offspring of aged mothers.

Placental morphometry in relation to daughters' percent mammographic breast density at midlife

Intrauterine and early-life exposures, including intrauterine smoke exposures and infant growth are associated with mammographic breast density (MBD), a strong breast cancer risk factor. We investigated whether placental morphometry, which is affected by intrauterine smoke exposure and also influences infant growth, predicts %MBD at ages 37-47. In 247 daughters in the Child Health and Development Studies, we found that larger placental surface area and placental thickness were associated with lower %MBD (-0.32 per cm², 95% CI -0.6, -0.05; -37.8 per 0.5 cm, 95% CI= -73.3, -2.3 respectively) independent of mothers' smoking, age, weight, parity and daughters' birthweight and age at mammogram. We also observed a positive interaction between placental surface area and thickness (p < 0.05) such that the highest breast dense area was observed for offspring with the thickest and largest placentas. Factors that impact placental morphometry, in addition to in utero smoke exposure, may influence adult breast architecture and breast cancer risk.

Placentation and antitumor immunity regulated by a scaffolding protein in NK cells

Natural killer cells use the Gab3 adaptor protein to limit trophoblast invasion during pregnancy and to reject tumor cells. See the related Research Article by Sliz et al.

Inhibition of Phosphoinositide-3-Kinase Signaling Promotes the Stem Cell State of Trophoblast

Trophoblast stem cells (TSCs) are a heterogeneous cell population despite the presence of fibroblast growth factor (FGF) and transforming growth factor β (TGFB) as key growth factors in standard culture conditions. To understand what other signaling cascades control the stem cell state of mouse TSCs, we performed a kinase inhibitor screen and identified several novel pathways that cause TSC differentiation. Surprisingly, inhibition of phosphoinositide-3-kinase (PI3K) signaling increased the mRNA and protein expression of stem cell markers instead, and resulted in a tighter epithelial colony morphology and fewer differentiated cells. PI3K inhibition could not substitute for FGF or TGFB and did not affect phosphorylation of extracellular signal-regulated kinase, and thus acts independently of these pathways. Upon removal of PI3K inhibition, TSC transcription factor levels reverted to normal TSC levels, indicating that murine TSCs can reversibly switch between these two states. In summary, PI3K inhibition reduces the heterogeneity and seemingly heightens the stem cell state of TSCs as indicated by the simultaneous upregulation of multiple key marker genes and cell morphology. Stem Cells 2019;37:1307-1318.

High-resolution contrast-enhanced microCT reveals the true three-dimensional morphology of the murine placenta

Genetic engineering of the mouse genome identified many genes that are essential for embryogenesis. Remarkably, the prevalence of concomitant placental defects in embryonic lethal mutants is highly underestimated and indicates the importance of detailed placental analysis when phenotyping new individual gene knockouts. Here we introduce high-resolution contrast-enhanced microfocus computed tomography (CE-CT) as a nondestructive, high-throughput technique to evaluate the 3D placental morphology. Using a contrast agent, zirconium-substituted Keggin polyoxometalate (Zr-POM), the soft tissue of the placenta (i.e., different layers and cell types and its vasculature) was imaged with a resolution of 3.5 µm voxel size. This approach allowed us to visualize and study early and late stages of placental development. Moreover, CE-CT provides a method to precisely quantify placental parameters (i.e., volumes, volume fraction, ratio of different placental layers, and volumes of specific cell populations) that are crucial for statistical comparison studies. The CE-CT assessment of the 3D morphology of the placentas was validated (i) by comparison with standard histological studies; (ii) by evaluating placentas from 2 different mouse strains, 129S6 and C57BL/6J mice; and (iii) by confirming the placental phenotype of mice lacking phosphoinositol 3-kinase (PI3K)-p110α. Finally, the Zr-POM-based CE-CT allowed for inspection of the vasculature structure in the entire placenta, as well as detecting placental defects in pathologies characterized by embryonic resorption and placental fusion. Taken together, Zr-POM-based CE-CT offers a quantitative 3D methodology to investigate placental development or pathologies.

Hyperandrogenism and insulin resistance-induced fetal loss: evidence for placental mitochondrial abnormalities and elevated reactive oxygen species production in pregnant rats that mimic the clinical features of polycystic ovary syndrome

KEY POINTS

Women with polycystic ovary syndrome (PCOS) commonly suffer from miscarriage, but the underlying mechanisms remain unknown. Herein, pregnant rats chronically treated with 5α-dihydrotestosterone (DHT) and insulin exhibited hyperandrogenism and insulin resistance, as well as increased fetal loss, and these features are strikingly similar to those observed in pregnant PCOS patients. Fetal loss in our DHT+insulin-treated pregnant rats was associated with mitochondrial dysfunction, disturbed superoxide dismutase 1 and Keap1/Nrf2 antioxidant responses, over-production of reactive oxygen species (ROS) and impaired formation of the placenta. Chronic treatment of pregnant rats with DHT or insulin alone indicated that DHT triggered many of the molecular pathways leading to placental abnormalities and fetal loss, whereas insulin often exerted distinct effects on placental gene expression compared to co-treatment with DHT and insulin. Treatment of DHT+insulin-treated pregnant rats with the antioxidant N-acetylcysteine improved fetal survival but was deleterious in normal pregnant rats. Our results provide insight into the fetal loss associated with hyperandrogenism and insulin resistance in women and suggest that physiological levels of ROS are required for normal placental formation and fetal survival during pregnancy.

ABSTRACT

Women with polycystic ovary syndrome (PCOS) commonly suffer from miscarriage, but the underlying mechanism of PCOS-induced fetal loss during pregnancy remains obscure and specific therapies are lacking. We used pregnant rats treated with 5α-dihydrotestosterone (DHT) and insulin to investigate the impact of hyperandrogenism and insulin resistance on fetal survival and to determine the molecular link between PCOS conditions and placental dysfunction during pregnancy. Our study shows that pregnant rats chronically treated with a combination of DHT and insulin exhibited endocrine aberrations such as hyperandrogenism and insulin resistance that are strikingly similar to those in pregnant PCOS patients. Of pathophysiological significance, DHT+insulin-treated pregnant rats had greater fetal loss and subsequently decreased litter sizes compared to normal pregnant rats. This negative effect was accompanied by impaired trophoblast differentiation, increased glycogen accumulation, and decreased angiogenesis in the placenta. Mechanistically, we report that over-production of reactive oxygen species (ROS) in the placenta, mitochondrial dysfunction, and disturbed superoxide dismutase 1 (SOD1) and Keap1/Nrf2 antioxidant responses constitute important contributors to fetal loss in DHT+insulin-treated pregnant rats. Many of the molecular pathways leading to placental abnormalities and fetal loss in DHT+insulin treatment were also seen in pregnant rats treated with DHT alone, whereas pregnant rats treated with insulin alone often exerted distinct effects on placental gene expression compared to insulin treatment in combination with DHT. We also found that treatment with the antioxidant N-acetylcysteine (NAC) improved fetal survival in DHT+insulin-treated pregnant rats, an effect related to changes in Keap1/Nrf2 and nuclear factor-κB signalling. However, NAC administration resulted in fetal loss in normal pregnant rats, most likely due to PCOS-like endocrine abnormality induced by the treatment. Our results suggest that the deleterious effects of hyperandrogenism and insulin resistance on fetal survival are related to a constellation of mitochondria-ROS-SOD1/Nrf2 changes in the placenta. Our findings also suggest that physiological levels of ROS are required for normal placental formation and fetal survival during pregnancy.

Fetal and trophoblast PI3K p110α have distinct roles in regulating resource supply to the growing fetus in mice

Studies suggest that placental nutrient supply adapts according to fetal demands. However, signaling events underlying placental adaptations remain unknown. Here we demonstrate that phosphoinositide 3-kinase p110α in the fetus and the trophoblast interplay to regulate placental nutrient supply and fetal growth. Complete loss of fetal p110α caused embryonic death, whilst heterozygous loss resulted in fetal growth restriction and impaired placental formation and nutrient transport. Loss of trophoblast p110α resulted in viable fetuses, abnormal placental development and a failure of the placenta to transport sufficient nutrients to match fetal demands for growth. Using RNA-seq we identified genes downstream of p110α in the trophoblast that are important in adapting placental phenotype. Using CRISPR/Cas9 we showed loss of p110α differentially affects gene expression in trophoblast and embryonic stem cells. Our findings reveal important, but distinct roles for p110α in the different compartments of the conceptus, which control fetal resource acquisition and growth.

Time-restricted feeding reduces high-fat diet associated placental inflammation and limits adverse effects on fetal organ development

Maternal nutrition has become a major public health concern over recent years and is a known predictor of adverse long-term metabolic derangement in offspring. Time-restricted feeding (TRF), wherein food consumption is restricted to the metabolically active phase of the day, is a dietary approach that improves metabolic parameters when consuming a high-fat diet (HFD). Here, we tested whether TRF could reduce maternal HFD associated inflammation and thereby mitigate defects in fetal organ developmental. Female rats were kept on following three dietary regimens; Ad libitum normal chow diet (NCD-AL), Ad libitum HFD (HFD-AL) and Time-restricted fed HFD (HFD-TRF) from 5 months prior to mating and continued throughout pregnancy. Rat dams were sacrificed at embryonic day 18.5 (ED18.5) and placental tissues from these rats were processed for the analysis of cellular apoptosis, inflammatory cytokines (TNFα and IL-6), oxidative stress, endoplasmic reticulum (ER) stress and autophagy. Furthermore, fetal hepatic triglyceride (TG) content and fetal lung maturation were assessed at ED18.5. Biochemical analysis revealed that HFD-TRF rat had significantly lower serum TG levels and body weight compared to HFD-AL rats. Additionally, TRF significantly blocked HFD-induced placental apoptosis and inflammation via minimizing cellular stress, and restoring autophagic flux. In addition, fetal hepatosteatosis and delayed fetal lung maturation induced by HFD was significantly ameliorated in HFD-TRF compared to HFD-AL. Collectively, our results suggest that reducing placental inflammation via TRF could prevent adverse fetal metabolic outcomes in pregnancies complicated by maternal obesity.

In utero and postnatal programing of dehydroepiandrosterone sulfate (DHEAS) in young adult women

Fetal adrenal-derived OH-DHEAS is the primary precursor for maternal estriol, an abundant, human, placental estrogen. We measured maternal pregnancy estriol as a marker of fetal adrenal function + placenta capacity to synthesize estriol. We hypothesized that maternal estriol is directly correlated with the adrenal hormone, DHEAS, in young adult women. We tested this hypothesis in a subset of women in the Child Health and Development Studies (351 of 470 eligible). 176 of these had serum samples collected at ages 27-30 for DHEAS assays, archived maternal pregnancy serum for estriol assays, and childhood growth data. In regression analyses, both maternal estriol and accelerated growth in middle childhood were independently, directly associated with DHEAS (+19% for quartile 4 versus quartile 1 of estriol, 95%CI=+ 2%, +36% and +12% for quartile 4 versus quartile 1 for middle childhood growth, 95%CI= +3%, +21%). Adrenal function may be programmed in utero and middle childhood with long-term consequences.

Regulating needs: Exploring the role of insulin-like growth factor-2 signalling in materno-fetal resource allocation

During pregnancy, the fetus requires nutrients supplied by the mother to grow and develop. However, the mother also requires sufficient resources to support the pregnancy, as well as, to maintain her health. Failure to regulate resource allocation between the mother and fetus can lead to pregnancy complications with immediate and life-long consequences for maternal and offspring health. This review explores the role of insulin-like growth factor (IGF)-2 in regulating materno-fetal resource allocation, particularly via its regulation of placental development and function.

Assessment of Placental Transport Function in Studies of Disease Programming

Environmental conditions during pregnancy affect fetal growth and development and program the offspring for poor future health. These effects may be mediated by the placenta, which develops to transfer nutrients from the mother to the fetus for growth. The ability to measure the unidirectional maternofetal transfer of non-metabolizable radio-analogues of glucose and amino acid by the placenta in vivo has thus been invaluable to our understanding of the regulation of fetal growth, particularly in small animal models. Herein, I describe the method by which in vivo placental transfer function can be quantified in the mouse, an animal model widely used in studies of in utero disease programming.

Placental Dysfunction Underlies Increased Risk of Fetal Growth Restriction and Stillbirth in Advanced Maternal Age Women

Pregnancies in women of advanced maternal age (AMA) are susceptible to fetal growth restriction (FGR) and stillbirth. We hypothesised that maternal ageing is associated with utero-placental dysfunction, predisposing to adverse fetal outcomes. Women of AMA (≥35 years) and young controls (20-30 years) with uncomplicated pregnancies were studied. Placentas from AMA women exhibited increased syncytial nuclear aggregates and decreased proliferation, and had increased amino acid transporter activity. Chorionic plate and myometrial artery relaxation was increased compared to controls. AMA was associated with lower maternal serum PAPP-A and sFlt and a higher PlGF:sFlt ratio. AMA mice (38-41 weeks) at E17.5 had fewer pups, more late fetal deaths, reduced fetal weight, increased placental weight and reduced fetal:placental weight ratio compared to 8-12 week controls. Maternofetal clearance of 14C-MeAIB and 3H-taurine was reduced and uterine arteries showed increased relaxation. These studies identify reduced placental efficiency and altered placental function with AMA in women, with evidence of placental adaptations in normal pregnancies. The AMA mouse model complements the human studies, demonstrating high rates of adverse fetal outcomes and commonalities in placental phenotype. These findings highlight placental dysfunction as a potential mechanism for susceptibility to FGR and stillbirth with AMA.

Placental phenotype and the insulin-like growth factors: resource allocation to fetal growth

The placenta is the main determinant of fetal growth and development in utero. It supplies all the nutrients and oxygen required for fetal growth and secretes hormones that facilitate maternal allocation of nutrients to the fetus. Furthermore, the placenta responds to nutritional and metabolic signals in the mother by altering its structural and functional phenotype, which can lead to changes in maternal resource allocation to the fetus. The molecular mechanisms by which the placenta senses and responds to environmental cues are poorly understood. This review discusses the role of the insulin-like growth factors (IGFs) in controlling placental resource allocation to fetal growth, particularly in response to adverse gestational environments. In particular, it assesses the impact of the IGFs and their signalling machinery on placental morphogenesis, substrate transport and hormone secretion, primarily in the laboratory species, although it draws on data from human and other species where relevant. It also considers the role of the IGFs as environmental signals in linking resource availability to fetal growth through changes in the morphological and functional phenotype of the placenta. As altered fetal growth is associated with increased perinatal morbidity and mortality and a greater risk of developing adult-onset diseases in later life, understanding the role of IGFs during pregnancy in regulating placental resource allocation to fetal growth is important for identifying the mechanisms underlying the developmental programming of offspring phenotype by suboptimal intrauterine growth.

Evaluation of circulating miRNAs during late pregnancy in the mare

MicroRNAs (miRNAs) are small, non-coding RNAs which are produced throughout the body. Individual tissues tend to have a specific expression profile and excrete many of these miRNAs into circulation. These circulating miRNAs may be diagnostically valuable biomarkers for assessing the presence of disease while minimizing invasive testing. In women, numerous circulating miRNAs have been identified which change significantly during pregnancy-related complications (e.g. chorioamnionitis, eclampsia, recurrent pregnancy loss); however, no prior work has been done in this area in the horse. To identify pregnancy-specific miRNAs, we collected serial whole blood samples in pregnant mares at 8, 9, 10 m of gestation and post-partum, as well as from non-pregnant (diestrous) mares. In total, we evaluated a panel of 178 miRNAs using qPCR, eventually identifying five miRNAs of interest. One miRNA (miR-374b) was differentially regulated through late gestation and four miRNAs (miR-454, miR-133b, miR-486-5p and miR-204b) were differentially regulated between the pregnant and non-pregnant samples. We were able to identify putative targets for the differentially regulated miRNAs using two separate target prediction programs, miRDB and Ingenuity Pathway Analysis. The targets for the miRNAs differentially regulated during pregnancy were predicted to be involved in signaling pathways such as the STAT3 pathway and PI3/AKT signaling pathway, as well as more endocrine-based pathways, including the GnRH, prolactin and insulin signaling pathways. In summary, this study provides novel information about the changes occurring in circulating miRNAs during normal pregnancy, as well as attempting to predict the biological effects induced by these miRNAs.

Competition for Materno-Fetal Resource Partitioning in a Rabbit Model of Undernourished Pregnancy

The major goal of animal production is to obtain abundant and healthy meat for consumers. Maternal food restriction (MFR) is often applied in farms to reduce production costs. However, the suitability of MFR in livestock animals is questionable, as this management may compromise maternal fitness due to a severe negative energetic balance and can induce Intrauterine Growth Restriction (IUGR) and prenatal programming in the offspring. Here, we sought to determine, using pregnant rabbits, the consequences of MFR on maternal endocrine and metabolic status and conceptus development. Pregnant dams were distributed into three groups: CONTROL (ad libitum feeding throughout the entire pregnancy; mean pregnancy length being around 31 days), UNDERFED (50% MFR during the entire pregnancy) and EARLY-UNDERFED (50% MFR only during the preimplantation period, Days 0–7). Maternal leptin concentrations and glycemic and lipid profiles were determined throughout pregnancy, whilst conceptus development was assessed ex-vivo at Day 28. Placental parameters were determined by macroscopic and histological evaluations and apoptotic assessments (TUNEL and Caspase-3). The main results of the study showed that, despite MFR altered maternal plasma lipid concentration (P<0.05), there were no effects on maternal bodyweight, plasma leptin concentration or glycemic profile. Fetal crown-rump lengths were reduced in both undernourished groups (P<0.001), but a significant reduction in fetal weight was only observed in the UNDERFED group (P<0.001). Growth in both undernourished groups was asymmetrical, with reduced liver weight (P<0.001) and significantly increased brain: fetal weight-ratio (P<0.001) and brain: liver weight-ratio (P<0.001) when compared to the CONTROL group. A significant reduction in placental weight was only observed in the UNDERFED group (P<0.001), despite both undernourished groups showing higher apoptotic rates at decidua and labyrinth zone (P<0.05) than the CONTROL group. Thus, these groups evidenced signs of placental degeneration, necrosis and stromal collapse. In summary, MFR may encourage the mother to make strategic decisions to safeguard her metabolic status and fitness at the expense of growth reduction in the litter, resulting in enhanced apoptotic and pathological processes at placental level and IUGR.

Review: Sexual dimorphism in the formation, function and adaptation of the placenta

Exposure of the embryo or fetus to perturbations in utero can result in intrauterine growth restriction, a primary risk factor for the development of adult disease. However, despite similar exposures, males and females often have altered disease susceptibility or progression from different stages of life. Fetal growth is largely mediated by the placenta, which, like the fetus is genetically XX or XY. The placenta and its associated trophoblast lineages originate from the trophectoderm (TE) of the early embryo. Rodent models (rat, mouse, spiny mouse), have been used extensively to examine placenta development and these have demonstrated the growth trajectory of the placenta in females is generally slower compared to males, and also shows altered adaptive responses to stressful environments. These placental adaptations are likely to depend on the type of stressor, duration, severity and the window of exposure during development. Here we describe the divergent developmental pathways between the male and female placenta contributing to altered differentiation of the TE derived trophoblast subtypes, placental growth, and formation of the placental architecture. Our focus is primarily genetic or environmental perturbations in rodent models which show altered placental responsiveness between sexes. We suggest that perturbations during early placental development may have greater impact on viability and growth of the female fetus whilst those occurring later in gestation may preferentially affect the male fetus. This may be of great relevance to human pregnancies which result from assisted reproductive technologies or complications such as pre-eclampsia and diabetes.