Relationship between fetal weight, placental growth and litter size in mice from mid- to late-gestation

Apoptotic and non-apoptotic roles of caspases in placenta physiology and pathology

Caspases, a family of cysteine proteases, are pivotal regulators of apoptosis, the tightly controlled cell death process crucial for eliminating excessive or unnecessary cells during development, including placental development. Collecting research has unveiled the multifaceted roles of caspases in the placenta, extending beyond apoptosis. Apart from their involvement in placental tissue remodeling via apoptosis, caspases actively participate in essential regulatory processes, such as trophoblast fusion and differentiation, significantly influencing placental growth and functionality. In addition, growing evidence indicates an elevation in caspase activity under pathological conditions like pre-eclampsia (PE) and intrauterine growth restriction (IUGR), leading to excessive cell death as well as inflammation. Drawing from advancements in caspase research and placental development under both normal and abnormal conditions, we examine the significance of caspases in both cell death (apoptosis) and non-cell death-related processes within the placenta. We also discuss potential therapeutics targeting caspase-related pathways for placenta disorders.

Placenta: an old organ with new functions

The transition from oviparity to viviparity and the establishment of feto-maternal communications introduced the placenta as the major anatomical site to provide nutrients, gases, and hormones to the developing fetus. The placenta has endocrine functions, orchestrates maternal adaptations to pregnancy at different periods of pregnancy, and acts as a selective barrier to minimize exposure of developing fetus to xenobiotics, pathogens, and parasites. Despite the fact that this ancient organ is central for establishment of a normal pregnancy in eutherians, the placenta remains one of the least studied organs. The first step of pregnancy, embryo implantation, is finely regulated by the trophoectoderm, the precursor of all trophoblast cells. There is a bidirectional communication between placenta and endometrium leading to decidualization, a critical step for maintenance of pregnancy. There are three-direction interactions between the placenta, maternal immune cells, and the endometrium for adaptation of endometrial immune system to the allogeneic fetus. While 65% of all systemically expressed human proteins have been found in the placenta tissues, it expresses numerous placenta-specific proteins, whose expression are dramatically changed in gestational diseases and could serve as biomarkers for early detection of gestational diseases. Surprisingly, placentation and carcinogenesis exhibit numerous shared features in metabolism and cell behavior, proteins and molecular signatures, signaling pathways, and tissue microenvironment, which proposes the concept of "cancer as ectopic trophoblastic cells". By extensive researches in this novel field, a handful of cancer biomarkers has been discovered. This review paper, which has been inspired in part by our extensive experiences during the past couple of years, highlights new aspects of placental functions with emphasis on its immunomodulatory role in establishment of a successful pregnancy and on a potential link between placentation and carcinogenesis.

Preconception paternal alcohol exposure decreases IVF embryo survival and pregnancy success rates in a mouse model

Increasingly, couples struggling with fertility turn to assisted reproductive techniques, including IVF, to have children. Despite the demonstrated influence of periconception male health and lifestyle choices on offspring development, studies examining IVF success rates and child health outcomes remain exclusively focused on maternal factors. Using a physiologically relevant mouse model, we tested the hypothesis that chronic paternal preconception alcohol intake adversely affects IVF success and negatively impacts IVF offspring fetoplacental growth. Using a voluntary, binge-like mouse model, we exposed sexually mature C57BL/6J males to three preconception treatments (0% (Control), 6% EtOH or 10% EtOH) for 6 weeks, isolated and cryopreserved caudal sperm from treated males, and then used these samples to fertilize oocytes before assessing IVF embryo developmental outcomes. We found that preconception paternal alcohol use reduced IVF embryo survival and pregnancy success rates in a dose-dependent manner, with the pregnancy success rate of the 10% EtOH treatment falling to half those of the Controls. Mechanistically, we found that preconception paternal alcohol exposure disrupts embryonic gene expression, including Fgf4 and Egfr, two critical regulators of trophectoderm stem cell growth and placental patterning, with lasting impacts on the histological organization of the late-term placenta. The changes in placental histoarchitecture were accompanied by altered regulation of pathways controlling mitochondrial function, oxidative phosphorylation and some imprinted genes. Our studies indicate that male alcohol use may significantly impede IVF success rates, increasing the couple's financial burden and emotional stress, and highlights the need to expand prepregnancy messaging to emphasize the reproductive dangers of alcohol use by both parents.

A novel murine model of post-implantation malaria-induced preterm birth

Despite major advances made in malaria treatment and control over recent decades, the development of new models for studying disease pathogenesis remains a vital part of malaria research efforts. The study of malaria infection during pregnancy is particularly reliant on mouse models, as a means of circumventing many challenges and costs associated with pregnancy studies in endemic human populations. Here, we introduce a novel murine model that will further our understanding of how malaria infection affects pregnancy outcome. When C57BL/6J (B6) mice are infected with Plasmodium chabaudi chabaudi AS on either embryonic day (E) 6.5, 8.5, or 10.5, preterm birth occurs in all animals by E16.5, E17.5, or E18.5 respectively, with no evidence of intrauterine growth restriction. Despite having the same outcome, we found that the time to delivery, placental inflammatory and antioxidant transcript upregulation, and the relationships between parasitemia and transcript expression prior to preterm birth differed based on the embryonic day of infection. On the day before preterm delivery, E6.5 infected mice did not experience significant upregulation of the inflammatory or antioxidant gene transcripts examined; however, peripheral and placental parasitemia correlated positively with Il1β, Cox1, Cat, and Hmox1 placental transcript abundance. E8.5 infected mice had elevated transcripts for Ifnγ, Tnf, Il10, Cox1, Cox2, Sod1, Sod2, Cat, and Nrf2, while Sod3 was the only transcript that correlated with parasitemia. Finally, E10.5 infected mice had elevated transcripts for Ifnγ only, with a tendency for Tnf transcripts to correlate with peripheral parasitemia. Tumor necrosis factor deficient (TNF-/-) and TNF receptor 1 deficient (TNFR1-/-) mice infected on E8.5 experienced preterm birth at the same time as B6 controls. Further characterization of this model is necessary to discover the mechanism(s) and/or trigger(s) responsible for malaria-driven preterm birth caused by maternal infection during early pregnancy.

Fetal Brain Elicits Sexually Conflicting Transcriptional Response to the Ablation of Uterine Forkhead Box A2 (Foxa2) in Mice

In this study, we investigated the effects of ablation of uterine Forkhead Box A2 (Foxa2) on gene expression of fetal brain relative to placenta. Using a conditional knockout mouse model for uterine Foxa2, here we show that the lack of uterine Foxa2 elicits a sexually-conflicting transcriptional response in the fetal brain relative to placenta. The ablation of Foxa2 in the uterus altered expression of genes related to growth, nutrient sensing, aging, longevity and angiogenesis among others. In the wildtype mice, these genes were expressed higher in the fetal brain and placenta of males compared to females. However, in mice lacking uterine Foxa2, the same genes showed the opposite pattern i.e., higher expression in the fetal brain and placenta of females compared to males. Based on the known marker genes of mice placenta and fetal brain cells, we further predicted that the genes exhibiting the sexually conflicting expression were associated with vascular endothelial cells. Overall, our study suggests that uterine Foxa2 plays a role in the regulation of the brain-placental axis by influencing the fetoplacental vascular changes during pregnancy.

Considering intrauterine location in a model of fetal growth restriction after maternal titanium dioxide nanoparticle inhalation

Fetal growth restriction (FGR) is a condition with several underlying etiologies including gestational disease (e.g., preeclampsia, gestational diabetes) and xenobiotic exposure (e.g., environmental contaminants, pharmaceuticals, recreational drugs). Rodent models allow study of FGR pathogenesis. However, given the multiparous rodent pregnancy, fetal growth variability within uterine horns may arise. To ascertain whether intrauterine position is a determinant of fetal growth, we redesigned fetal weight analysis to include litter size and maternal weight. Our FGR model is produced by exposing pregnant Sprague Dawley rats to aerosolized titanium dioxide nanoparticles at 9.44 ± 0.26 mg/m3 on gestational day (GD) 4, GD 12 or GD 17 or 9.53 ± 1.01 mg/m3 between GD 4-GD 19. In this study fetal weight data was reorganized by intrauterine location [i.e., right/left uterine horn and ovarian/middle/vaginal position] and normalized by maternal weight and number of feti per uterine horn. A significant difference in fetal weight in the middle location in controls (0.061g ± 0.001 vs. 0.055g ± 0.002), GD 4 (0.033g ± 0.003 vs. 0.049g ± 0.004), and GD 17 (0.047g ± 0.002 vs. 0.038g ± 0.002) exposed animals was identified. Additionally, GD 4 exposure produced significantly smaller feti in the right uterine horn at the ovarian end (0.052g ± 0.003 vs. 0.029g ± 0.003) and middle of the right uterine horn (0.060g ± 0.001 vs. 0.033g ± 0.003). GD 17 exposure produced significantly smaller feti in the left uterine horn middle location (0.055g ± 0.002 vs. 0.033 ± 0.002). Placental weights were unaffected, and placental efficiency was reduced in the right uterine horn middle location after GD 17 exposure (5.74g ± 0.16 vs. 5.09g ± 0.14). These findings identified: 1) differences in fetal weight of controls between the right and left horns in the middle position, and 2) differential effects of single whole-body pulmonary exposure to titanium dioxide nanoparticles on fetal weight by position and window of maternal exposure. In conclusion, these results indicate that consideration for intrauterine position, maternal weight, and number of feti per horn provides a more sensitive assessment of FGR from rodent reproductive and developmental studies.

Controlling litter effects to enhance rigor and reproducibility with rodent models of neurodevelopmental disorders

Research with rodents is crucial for expanding our understanding of genetic and environmental risk factors for neurodevelopmental disorders (NDD). However, there is growing concern about the number of animal studies that are difficult to replicate, potentially undermining the validity of results. These concerns have prompted funding agencies and academic journals to implement more rigorous standards in an effort to increase reproducibility in research. However, these standards fail to address a major source of variability in rodent research brought on by the “litter effect,” the fact that rodents from the same litter are phenotypically more similar to one other than rodents from different litters of the same strain. We show that the litter effect accounts for 30–60% of the variability associated with commonly studied phenotypes, including brain, placenta, and body weight. Moreover, we show how failure to control for litter-to-litter variation can mask a phenotype in Chd8^V986*/+ mice that model haploinsufficiency of CHD8, a high-confidence autism gene. Thus, if not properly controlled, the litter effect has the potential to negatively influence rigor and reproducibility of NDD research. While efforts have been made to educate scientists on the importance of controlling for litter effects in previous publications, our analysis of the recent literature (2015–2020) shows that the vast majority of NDD studies focused on genetic risks, including mutant mouse studies, and environmental risks, such as air pollution and valproic acid exposure, do not correct for litter effects or report information on the number of litters used. We outline best practices to help scientists minimize the impact of litter-to-litter variability and to enhance rigor and reproducibility in future NDD studies using rodent models.

Haldane's rule in the placenta: Sex-biased misregulation of the Kcnq1 imprinting cluster in hybrid mice

Hybrid phenotypes that contribute to postzygotic reproductive isolation often exhibit pronounced asymmetry, both between reciprocal crosses and between the sexes in accordance with Haldane's rule. Inviability in mammalian hybrids is associated with parent-of-origin placental growth abnormalities for which misregulation of imprinted gene (IGs) is the leading candidate mechanism. However, direct evidence for the involvement of IGs in hybrid growth dysplasia is limited. We used transcriptome and reduced representation bisulfite sequencing to conduct the first genome-scale assessment of the contribution of IGs to parent-of-origin placental growth dysplasia in the cross between the house mouse (Mus musculus domesticus) and the Algerian mouse (Mus spretus). IGs with transgressive expression and methylation were concentrated in the Kcnq1 cluster, which contains causal genes for prenatal growth abnormalities in mice and humans. Hypermethylation of the cluster's imprinting control region, and consequent misexpression of the genes Phlda2 and Ascl2, is a strong candidate mechanism for transgressive placental undergrowth. Transgressive placental and gene regulatory phenotypes, including expression and methylation in the Kcnq1 cluster, were more extreme in hybrid males. Although consistent with Haldane's rule, male-biased defects are unexpected in rodent placenta because the X-chromosome is effectively hemizygous in both sexes. In search of an explanation, we found evidence of leaky imprinted (paternal) X-chromosome inactivation in hybrid female placenta, an epigenetic disturbance that may buffer females from the effects of X-linked incompatibilities to which males are fully exposed. Sex differences in chromatin structure on the X and sex-biased maternal effects are nonmutually exclusive alternative explanations for adherence to Haldane's rule in hybrid placenta. The results of this study contribute to understanding the genetic basis of hybrid inviability in mammals, and the role of IGs in speciation.

Biparental contributions of the H2A.B histone variant control embryonic development in mice

Histone variants expand chromatin functions in eukaryote genomes. H2A.B genes are testis-expressed short histone H2A variants that arose in placental mammals. Their biological functions remain largely unknown. To investigate their function, we generated a knockout (KO) model that disrupts all 3 H2A.B genes in mice. We show that H2A.B KO males have globally altered chromatin structure in postmeiotic germ cells. Yet, they do not show impaired spermatogenesis or testis function. Instead, we find that H2A.B plays a crucial role postfertilization. Crosses between H2A.B KO males and females yield embryos with lower viability and reduced size. Using a series of genetic crosses that separate parental and zygotic contributions, we show that the H2A.B status of both the father and mother, but not of the zygote, affects embryonic viability and growth during gestation. We conclude that H2A.B is a novel parental-effect gene, establishing a role for short H2A histone variants in mammalian development. We posit that parental antagonism over embryonic growth drove the origin and ongoing diversification of short histone H2A variants in placental mammals.

Extraembryonic heparin-binding epidermal growth factor-like growth factor deficiency compromises placentation in mice

Heparin-binding epidermal growth factor (EGF)-like growth factor (HBEGF) is expressed in the embryo and uterus at the implantation site, stimulating trophoblast invasive activity essential for placentation. The effect of extraembryonic HBEGF deficiency on placental development was investigated by breeding mice heterozygous for the Hbegf null mutation. On gestation day 13.5, the average placental weights of the wild-type (Hbegf+/+) and heterozygous (Hbegf+/-) mice were approximately 76 and 77 mg, respectively, as opposed to reduced average placental weights of approximately 61 mg in homozygous null (Hbgef-/-) females. In contrast, fetal weights were not significantly affected by genotype. HBEGF immunostaining in placental sections was Hbegf gene dosage-dependent, while expression of other EGF family members was comparable in Hbegf+/+ and Hbegf-/- placentas. Histological analysis revealed no apparent differences in trophoblast giant cells, but the spongiotrophoblast region was reduced compared to labyrinth (P < 0.05) in Hbegf null placentas. While no differences in cell apoptosis were noted, proliferation as assessed by nuclear Ki67 staining was elevated in the labyrinth and decreased in the spongiotrophoblast region of Hbegf-/- placentas. Labyrinth morphology appeared disrupted in Hbegf -/- placentas stained with laminin, a marker for capillary basement membrane, and the capillary density was reduced. Immunohistochemical staining revealed reduced vascular endothelial growth factor (VEGF) levels in both spongiotrophoblast and labyrinth (P < 0.01) regions of Hbegf-/- placentas. In vitro, HBEGF supplementation increases the expression of VEGF in a human trophoblast cell line. These findings suggest that trophoblast HBEGF promotes placental capillary formation by inducing VEGF in the developing placenta of mice.

Blastocyst transfer in mice alters the placental transcriptome and growth

Assisted reproduction technologies (ART) are becoming increasingly common. Therefore, how these procedures influence gene regulation and feto-placental development are important to explore. Here, we assess the effects of blastocyst transfer on mouse placental growth and transcriptome. C57Bl/6 blastocysts were transferred into uteri of B6D2F1 pseudopregnant females and dissected at embryonic day 10.5 for analysis. Compared to non-transferred controls, placentas from transferred conceptuses weighed less even though the embryos were larger on average. This suggested a compensatory increase in placental efficiency. RNA-sequencing of whole male placentas revealed 543 differentially expressed genes (DEGs) after blastocyst transfer: 188 and 355 genes were down-regulated and up-regulated, respectively. DEGs were independently validated in male and female placentas. Bioinformatic analyses revealed that DEGs represented expression in all major placental cell types and included genes that are critical for placenta development and/or function. Furthermore, the direction of transcriptional change in response to blastocyst transfer implied an adaptive response to improve placental function to maintain fetal growth. Our analysis revealed that CpG methylation at regulatory regions of two DEGs was unchanged in female transferred placentas and that DEGs had fewer gene-associated CpG islands (within ~20 kb region) compared to the larger genome. These data suggested that altered methylation at proximal promoter regions might not lead to transcriptional disruption in transferred placentas. Genomic clustering of some DEGs warrants further investigation of long-range, cis-acting epigenetic mechanisms including histone modifications together with DNA methylation. We conclude that embryo transfer, a protocol required for ART, significantly impacts the placental transcriptome and growth.

Melatonin Increases Fetal Weight in Wild-Type Mice but Not in Mouse Models of Fetal Growth Restriction

Fetal growth restriction (FGR) presents with an increased risk of stillbirth and childhood and adulthood morbidity. Melatonin, a neurohormone and antioxidant, has been suggested as having therapeutic benefit in FGR. We tested the hypothesis that melatonin would increase fetal growth in two mouse models of FGR which together represent a spectrum of the placental phenotypes in this complication: namely the endothelial nitric oxide synthase knockout mouse (eNOS^-/-) which presents with abnormal uteroplacental blood flow, and the placental specific Igf2 knockout mouse (P0^+/-) which demonstrates aberrant placental morphology akin to human FGR. Melatonin (5 μg/ml) was administered via drinking water from embryonic day (E)12.5 in C57Bl/6J wild-type (WT), eNOS^-/-, and P0^+/- mice. Melatonin supplementation significantly increased fetal weight in WT, but not eNOS^-/- or P0^+/- mice at E18.5. Melatonin did, however, significantly increase abdominal circumference in P0^+/- mice. Melatonin had no effect on placental weight in any group. Uterine arteries from eNOS^-/- mice demonstrated aberrant function compared with WT but melatonin treatment did not affect uterine artery vascular reactivity in either of these genotypes. Umbilical arteries from melatonin treated P0^+/- mice demonstrated increased relaxation in response to the nitric oxide donor SNP compared with control. The increased fetal weight in WT mice and abdominal circumference in P0^+/-, together with the lack of any effect in eNOS^-/-, suggest that the presence of eNOS is required for the growth promoting effects of melatonin. This study supports further work on the possibility of melatonin as a treatment for FGR.

Adaptations in Maternofetal Calcium Transport in Relation to Placental Size and Fetal Sex in Mice

Appropriate placental transport of calcium is essential for normal fetal skeletal mineralization. In fetal growth restriction (FGR), the failure of a fetus to achieve its growth potential, a number of placental nutrient transport systems show reduced activity but, in the case of calcium, placental transport is increased. In a genetic mouse model of FGR this increase, or adaptation, maintains appropriate fetal calcium content, relative to the size of the fetus, despite a small, dysfunctional placenta. It is unknown whether such an adaptation is also apparent in small, but normally functioning placentas. We tested the hypothesis that calcium transfer would be up-regulated in the lightest vs. heaviest placentas in the same C57Bl/6J wild-type (WT) mouse litter. Since lightest placentas are often from females, we also assessed whether fetal sex influenced placental calcium transfer. Placentas and fetuses were collected at embryonic day (E)16.5 and 18.5; the lightest and heaviest placentas, and female and male fetuses, were identified. Unidirectional maternofetal calcium clearance (^CaK_mf) was assessed following ⁴⁵Ca administration to the dam and subsequent radiolabel counts within the fetuses. Placental expression of calcium pathway components was measured by Western blot. Data (median) are lightest placenta expressed as percentage of the heaviest within a litter and analyzed by Wilcoxon signed-rank test. In WT mice having normally grown fetuses, ^CaK_mf, per gram placenta near term, in the lightest placentas was increased (126%; P < 0.05) in association with reduced fetal calcium accretion earlier in gestation (92%; P < 0.05), that was subsequently normalized near term. Increased placental expression of calbindin-D_9K, an important calcium binding protein, was observed in the lightest placentas near term (122%; P < 0.01). There was no difference in fetal calcium accretion between male and female littermates but a trend toward higher ^CaK_mf in females (P = 0.055). These data suggest a small, normal placenta adapts calcium transfer according to its size, as previously demonstrated in a mouse model of FGR. Fetal sex had limited influence on this adaptive increase. These adaptations are potentially driven by fetal nutrient demand, as evidenced by the normalization of fetal calcium content. Understanding the regulatory mechanisms involved may provide novel avenues for treating placental dysfunction.

Intrauterine Zika virus infection of pregnant immunocompetent mice models transplacental transmission and adverse perinatal outcomes

Zika virus (ZIKV) crosses the placenta and causes congenital disease. Here we develop an animal model utilizing direct ZIKV inoculation into the uterine wall of pregnant, immunocompetent mice to evaluate transplacental transmission. Intrauterine inoculation at embryonic day (E) 10, but not E14, with African, Asian or American strains of ZIKV reduces fetal viability and increases infection of placental and fetal tissues. ZIKV inoculation at E10 causes placental inflammation, placental dysfunction and reduces neonatal brain cortical thickness, which is associated with increased activation of microglia. Viral antigen localizes in trophoblast and endothelial cells in the placenta, and endothelial, microglial and neural progenitor cells in the fetal brain. ZIKV infection of the placenta increases production of IFNβ and expression of IFN-stimulated genes 48 h after infection. This mouse model provides a platform for identifying factors at the maternal-fetal interface that contribute to adverse perinatal outcomes in a host with an intact immune system.

Superovulation at a specific stage of the estrous cycle determines the reproductive performance in mice

Inconsistent reproductive performance has been reported in superovulated mice. Hence, the aim of this study was to analyze the effect and possible mechanism of superovulation timing on mouse reproductive performance. The results showed that mice superovulated at the metestrous (23.08±6.08%) and diestrous stages (33.33±11.45%) presented significantly lower pregnancy rates compared with those superovulated at the estrous stage (66.67±9.20%). After superovulation at the proestrous and estrous stages, mucin 1 (MUC1) and let-7a/let-7b microRNA (miRNA) expression levels were significantly attenuated and enhanced on embryonic day 3.5 (E3.5), respectively, whereas no significant differences in the expression level were found in mice superovulated at the other two stages. A higher number of developing and Graafian follicles was observed in the ovarian sections 48h after the administration of pregnant mare serum gonadotropin (PMSG) at the proestrous and estrous stages. The sections from mice treated at the metestrous and diestrous stages, however, presented more corpora lutea. Therefore, mice superovulated at the proestrous and estrous stages exhibited the best pregnancy rates. Furthermore, the disordered expression of MUC1 and let-7a/let-7b miRNA in mice superovulated at the metestrous and diestrous stages may impair reproduction performance.

Effect of Tocopheryl Acetate on Maternal Cigarette Smoke Exposed Swiss Albino Mice Inbred Fetus

INTRODUCTION

Cigarette smoking is worldwide problem which can be correlated with teratogenicity. Tocopheryl acetate plays as an antioxidant against the oxidative stress evolved by cigarette smoke exposure during pregnancy.

AIM

To study the effect of maternal exposure to cigarette smoke and Tocopheryl acetate on fetuses of mice.

MATERIALS AND METHODS

Pregnant mice randomly assigned to different groups (Group I (control), Group II (Tocopheryl acetate), Group III(soyabean oil used as vehicle for Tocopheryl acetate), Group IV (Cigarette smoke Exposed), Group V (Cigarette smoke exposed plus Tocopheryl acetate) and Group VI(Cigarette smoke exposed plus soyabean oil) were exposed to cigarette smoke 3 times a day for 20 minutes each time and Tocopheryl acetate with dose of 200mg/kg/day in 0.3ml of soyabean oil as vehicle orally through oral gavage from the 5th day of gestation to 15th day.

RESULTS

Cigarette smoke exposed mice showed significant fetal weight loss, resorption, placental anomalies, severe growth retardation, venous congestion, haemorrhage, limbs defects and enphalocele. Negligible abnormalities were seen among the control and Tocopheryl acetate group. Cigarette smoke exposed group with Tocopheryl acetate exhibited weight gain among the fetus as well as no gross abnormalities. The oxidative stress was significantly increased by increasing Malondialdehyde (MDA) 293±81.57 μmol/mg (p<0.0001) and decreasing Superoxide Dismutase (SOD) 1.43 ± 0.23mg/ml, (p<0.0001) Reduced Glutathione (GR) 0.017±0.002mg/ml, (p<0.01) and Catalase (CAT) 0.248±0.005mg/ml, (p<0.0001). Tocopheryl acetate induced group significantly maintained the oxidative stress with all p <0.0001.

CONCLUSION

It can be concluded that Tocopheryl acetate may have an ameliorating effect on the cigarette smoke during pregnancy on fetus.

Evaluation of the foetal time to death in mice after application of direct and indirect euthanasia methods

Directive 2010/63/EU on the protection of animals used for scientific purposes requires that the killing of mammal foetuses during the last third of their gestational period should be accomplished through effective and humane methods. The fact that murine foetuses are resistant to hypoxia-mediated euthanasia renders the current euthanasia methods ineffective or humane for the foetuses when these methods are applied to pregnant female mice. We have assessed the time to death of foetuses after performing either indirect (dam euthanasia) or direct (via intraplacental injection--a new approach to euthanasia) euthanasia methods in order to determine a euthanasia method that is appropriate, ethical and efficient for the killing of mouse foetuses. The respective times to death of foetuses after performing the three most commonly used euthanasia methods (namely cervical dislocation, CO2inhalation and intraperitoneal sodium pentobarbital administration) were recorded. Absence of foetal heartbeat was monitored via ultrasound. We consider that the most effective and humane method of foetal euthanasia was the one able to achieve foetal death within the shortest possible period of time. Among the indirect euthanasia methods assessed, the administration of a sodium pentobarbital overdose to pregnant female mice was found to be the fastest for foetuses, with an average post-treatment foetal death of approximately 29.8 min. As for the direct euthanasia method assessed, foetal time to death after intraplacental injection of sodium pentobarbital was approximately 14 min. Significant differences among the different mouse strains employed were found. Based on the results obtained in our study, we consider that the administration of a sodium pentobarbital overdose by intraplacental injection to be an effective euthanasia method for murine foetuses.

Polytocus focus: Uterine position effect is dependent upon horn size

Understanding the variability caused by uterine position effects in polytocus species, such as rats, may enhance prenatal animal models for the study of drug and environmental agents. The primiparous litters of 42 intact female Sprague-Dawley rats were studied. Uterine position, fetal body weight, and fetal brain (wet) weight were recorded on gestation day (GD) 20 (GD 0=sperm positive). Uterine position effect for brain and body weight varied depending upon horn size. Furthermore, an inverse relationship between horn size (and, to a lesser extent, litter size) and fetal weight applied to both body and brain weight measures. There were no statistical differences in brain and body weights between the left and right uterine horns. The position of the uterine horn (left vs. right) and litter size did not influence the uterine position effect in the rat. Collectively, the present data suggest the presence of a significant uterine position effect. Prenatal differences based on uterine position provide an untapped opportunity to increase our understanding of developmental neurotoxicological and teratological studies that employ a polytocus species as an animal model.

Developmental effects of oral exposure to diethylstilbestrol on mouse placenta

Placental growth and function are of biological significance in that placental tissue promotes prenatal life and the maintenance of pregnancy. Exposure to synthetic estrogens causes embryonic mortality and placental growth restriction in mice. The aim of the present study was to examine the effects of diethylstilbestrol (DES) on placenta in mice. DES at 1, 5, 10 or 15 µg kg(-1) day(-1) , or 17β-estradiol (E2 ) at 50 µg kg(-1) day(-1) , was administered orally to ICR mice on days 4 through to 8 of gestation. Expression of ERα, ERβ, ERRβ or ERRγ mRNA in the junctional or labyrinth zone of the placentas on day 13 was assessed using RT-PCR, as well as the embrynic mortality, embryonic and placental weight, histological changes of labyrinth and ultrastructural changes of the trophoblast giant cells (TGCs). Embryo mortalities in the DES 10 and 15 µg kg(-1) day(-1) groups were markedly increased. No significant changes in embryonic and placental weight were observed in any DES- or E2 -exposed groups. Expression of ERα mRNA in the junctional zone with male embryos in the 5 µg kg(-1) day(-1) group was significantly higher than that in the control, whereas expression was not determined in the 15 µg kg(-1) day(-1) group. Histological observation revealed that the placentas exposed to DES at 10 µg kg(-1) day(-1) lacked the developing labyrinth. Ultrastructural observation of the TGCs showed poor rough-surfaced endoplasmic reticulum in the DES 10 µg kg(-1) day(-1) group. The present data suggest that developmental changes induced by DES may be related to interference with the nutrition and oxygen exchange between mother and embryo or decreased protein synthesis, resulting in a high frequency of embryo mortality.

Sociability and brain development in BALB/cJ and C57BL/6J mice

Sociability--the tendency to seek social interaction--propels the development of social cognition and social skills, but is disrupted in autism spectrum disorders (ASD). BALB/cJ and C57BL/6J inbred mouse strains are useful models of low and high levels of juvenile sociability, respectively, but the neurobiological and developmental factors that account for the strains' contrasting sociability levels are largely unknown. We hypothesized that BALB/cJ mice would show increasing sociability with age but that C57BL/6J mice would show high sociability throughout development. We also hypothesized that littermates would resemble one another in sociability more than non-littermates. Finally, we hypothesized that low sociability would be associated with low corpus callosum size and increased brain size in BALB/cJ mice. Separate cohorts of C57BL/6J and BALB/cJ mice were tested for sociability at 19-, 23-, 31-, 42-, or 70-days-of-age, and brain weights and mid-sagittal corpus callosum area were measured. BALB/cJ sociability increased with age, and a strain by age interaction in sociability between 31 and 42 days of age suggested strong effects of puberty on sociability development. Sociability scores clustered according to litter membership in both strains, and perinatal litter size and sex ratio were identified as factors that contributed to this clustering in C57BL/6J, but not BALB/cJ, litters. There was no association between corpus callosum size and sociability, but smaller brains were associated with lower sociability in BALB/cJ mice. The associations reported here will provide directions for future mechanistic studies of sociability development.

A multigeneration reproductive and developmental safety evaluation of authentic Morinda citrifolia (noni) juice

The impact of Morinda citrifolia (noni) juice on fertility and offspring health in three generations of ICR mice was evaluated. The authenticity of the source of noni juice in this study was determined by chemical analysis of known marker compounds. Mice were supplied with 5% noni juice at gestation (day 0) until weaning (21 days postpartum). This procedure was followed through three generations of offspring. Three generations of control mice were also evaluated. There were no intergroup differences in gestation and fertility indices or malformation rates. However, litter sizes of the noni group in the first (F1),  second (F2), and third (F3) generations were, respectively, 29.3% (P < 0.01), 19.8% (P < 0.01) and 19.6% (P < 0.01) larger than corresponding controls. Despite larger litter sizes, there were no decreases in fetal weight in any generation of the noni group. Further, maternal health and offspring viability in the noni groups were equal to or greater than the controls. The results of this study suggest that authentic noni juice has no adverse effect on fertility and fetal development, consistent with previous two-generation studies of noni fruit from French Polynesia, Indonesia, and Hainan , China. On the contrary, noni juice appears to facilitate pregnancy and fetal development.

Identification of maternally regulated fetal gene networks in the placenta with a novel embryo transfer system in mice

The mechanisms for provisioning maternal resources to offspring in placental mammals involve complex interactions between maternally regulated and fetally regulated gene networks in the placenta, a tissue that is derived from the zygote and therefore of fetal origin. Here we describe a novel use of an embryo transfer system in mice to identify gene networks in the placenta that are regulated by the mother. Mouse embryos from the same strain of inbred mice were transferred into a surrogate mother either of the same strain or from a different strain, allowing maternal and fetal effects on the placenta to be separated. After correction for sex and litter size, maternal strain overrode fetal strain as the key determinant of fetal weight (P < 0.0001). Computational filtering of the placental transcriptome revealed a group of 81 genes whose expression was solely dependent on the maternal strain [P < 0.05, false discovery rate (FDR) < 0.10]. Network analysis of this group of genes yielded highest statistical significance for pathways involved in the regulation of cell growth (such as insulin-like growth factors) as well as those involved in regulating lipid metabolism [such as the low-density lipoprotein receptor-related protein 1 (LRP1), LDL, and HDL], both of which are known to play a role in fetal development. This novel technique may be generally applied to identify regulatory networks involved in maternal-fetal interaction and eventually help identify molecular targets in disorders of fetal growth.

Overexpression of thioredoxin-1 reduces oxidative stress in the placenta of transgenic mice and promotes fetal growth via glucose metabolism

Oxidative stress occurs where there is an imbalance between the production and scavenging of free radicals. Pregnancy per se is a state of oxidative stress due to the increased metabolic activity of placental mitochondria and reduced scavenging ability of antioxidant systems. Overproduction of reactive oxygen species may be associated with impaired fetal growth. However, the physiological influence of antioxidant systems on fetal growth is not well understood. In this study we assessed the effects of antioxidant systems on fetal growth using human thioredoxin (hTRX)-1 overexpressing transgenic (Tg) mice. Tg or C57BL/6 [wild-type (WT)] male mice were mated with WT female mice, and dams were killed to obtain the fetuses and placentas on gestational d 15. Tg fetuses were significantly heavier than WT fetuses, whereas placental weight did not differ significantly between the two groups. Immunohistochemically, hTRX-1 was localized to the nuclei of labyrinthine trophoblasts in Tg mice. In addition, placental expression of 8-hydroxy-2'-deoxyguanosine, which reflects DNA damage caused by oxidative stress, was reduced in Tg mice compared with WT mice. Placental expression of glucose transporter-1 mRNA and protein was significantly higher in Tg mice than WT mice, whereas no significant differences were observed for glucose transporter-3, IGF, and IGF-binding protein mRNA expression. These results suggest that placental and/or systemic antioxidant systems can influence fetal growth. In particular, increased hTRX-1 activity and the resulting modified placental redox state may play an important role in fetal growth by increasing the availability of glucose.

An animal model of cigarette smoke-induced in utero growth retardation

Maternal/fetal genetic constitution and environmental factors are vital to delivery of a healthy baby. In the United States (US), a low birth weight (LBW) baby is born every minute and a half. LBW, defined as weighing less than 5.5 lbs at birth, affects nearly 1 in 12 infants born in the US with resultant costs for the nation of more than 15 billion dollars annually. Infant birth weight is the single most important factor affecting neonatal mortality. Various environmental and genetic risk factors for LBW have been identified. Several risks are preventable, such as cigarette smoking during pregnancy. Over one million babies are exposed prenatally to cigarette smoke accounting for over 20% of the LBW incidence in the US. Cigarette smoke exposure in utero results in a variety of adverse developmental outcomes with intrauterine growth restriction and infant LBW being the most well documented. However, the mechanisms underlying the causes of LBW remain poorly understood. The purpose of this study was: (1) to establish an animal model of cigarette smoke-induced in utero growth retardation and LBW using physiologically relevant inhalation exposure conditions which simulate "active" and "passive" tobacco smoke exposures, and (2) to determine whether particular stages of development are more susceptible than others to the adverse effects of in utero smoke exposure on embryo/fetal growth. Pregnant C57BL/6J mice were exposed to cigarette smoke during three periods of gestation: pre-/peri-implantation (gestational days [gds] 1-5), post-implantation (gds 6-18), and throughout gestation (gds 1-17). Reproductive and fetal outcomes were assessed on gd 18.5. Exposure of dams to mainstream/sidestream cigarette smoke, simulating "active" maternal smoking, resulted in decreases in fetal weight and crown-rump length when exposed throughout gestation (gds 1-17). Similar results were seen when dams were exposed only during the first 5 days of gestation (pre-/peri-implantation period gds 1-5). Exposure of dams from the post-implantation period through gestation (gds 6-18) did not result in reduced fetal weight, although a significant reduction in crown-rump length remained evident. Interestingly, maternal sidestream smoke exposure, simulating exposure to environmental tobacco smoke (ETS), during the pre-/peri-implantation period of development also produced significant decreases in fetal weight and crown-rump length. Collectively, results from the present study confirm an association between prenatal exposure to either "active" or "passive" cigarette smoke and in utero growth retardation. The data also identify a period of susceptibility to in utero cigarette smoke exposure-induced growth retardation and LBW during pre-/peri-implantation embryonic development.