Effects ofIn uteroenvironment and maternal behavior on neuroendocrine and behavioral alterations in a mouse model of prenatal trauma

How is prenatal stress transmitted from the mother to the fetus?

Prenatal stress programmes long-lasting neuroendocrine and behavioural changes in the offspring. Often this programming is maladaptive and sex specific. For example, using a rat model of maternal social stress in late pregnancy, we have demonstrated that adult prenatally stressed male, but not prenatally stressed female offspring display heightened anxiety-like behaviour, whereas both sexes show hyperactive hypothalamo-pituitary-adrenal (HPA) axis responses to stress. Here, we review the current knowledge of the mechanisms underpinning dysregulated HPA axis responses, including evidence supporting a role for reduced neurosteroid-mediated GABAergic inhibitory signalling in the brains of prenatally stressed offspring. How maternal psychosocial stress is signalled from the mother to the fetuses is unclear. Direct transfer of maternal glucocorticoids to the fetuses is often considered to mediate the programming effects of maternal stress on the offspring. However, protective mechanisms including attenuated maternal stress responses and placental 11β-hydroxysteroid dehydrogenase-2 (which inactivates glucocorticoids) should limit materno-fetal glucocorticoid transfer during pregnancy. Moreover, a lack of correlation between maternal stress, circulating maternal glucocorticoid levels and circulating fetal glucocorticoid levels is reported in several studies and across different species. Therefore, here we interrogate the evidence for a role for maternal glucocorticoids in mediating the effects of maternal stress on the offspring and consider the evidence for alternative mechanisms, including an indirect role for glucocorticoids and the contribution of changes in the placenta in signalling the stress status of the mother to the fetus.

Prenatal and postnatal influences on behavioral development in a mouse model of preconceptional stress

Depression during pregnancy is detrimental for the wellbeing of the expectant mother and can exert long-term consequences on the offspring's development and mental health. In this context, both the gestational environment and the postpartum milieu may be negatively affected by the depressive pathology. It is, however, challenging to assess whether the contributions of prenatal and postnatal depression exposure are distinct, interactive, or cumulative, as it is unclear whether antenatal effects are due to direct effects on fetal development or because antenatal symptoms continue postnatally. Preclinical models have sought to answer this question by implementing stressors that induce a depressive-like state in the dams during pregnancy and studying the effects on the offspring. The aim of our present study was to disentangle the contribution of direct stress in utero from possible changes in maternal behavior in a novel model of preconceptional stress based on social isolation rearing (SIR). Using a cross-fostering paradigm in this model, we show that while SIR leads to subtle changes in maternal behavior, the behavioral changes observed in the offspring are driven by a complex interaction between sex, and prenatal and postnatal maternal factors. Indeed, male offspring are more sensitive to the prenatal environment, as demonstrated by behavioral and transcriptional changes driven by their birth mother, while females are likely affected by more complex interactions between the pre and the postpartum milieu, as suggested by the important impact of their surrogate foster mother. Taken together, our findings suggest that male and female offspring have different time-windows and behavioral domains of susceptibility to maternal preconceptional stress, and thus underscore the importance of including both sexes when investigating the mechanisms that mediate the negative consequences of exposure to such stressor.

Prenatal Stress Induces Long-Term Behavioral Sex-Dependent Changes in Rats Offspring: the Role of the HPA Axis and Epigenetics

Preclinical genetic studies have related stress early exposures with changes in gene regulatory mechanisms, including epigenetic alterations, such as modifications of DNA methylation, histone deacetylation, and histones acetylation. This study evaluates the effects of prenatal stress on the behavior, hypothalamus-pituitary-adrenal (HPA)-axis, and epigenetic parameters in stressed dams and their offspring. The rats were subjected to a protocol of chronic unpredictable mild stress on the fourteenth day of pregnancy until the birth of offspring. After birth, maternal care was evaluated for six days. Following weaning, the locomotor and depressive-like behaviors of the dams and their offspring (60 days old) were assessed. The HPA axis parameters were evaluated in serum from dams and offspring, and epigenetic parameters (histone acetyltransferase (HAT), histone deacetylase (HDAC), DNA methyltransferase (DNMT) activities, and the levels of histone H3 acetylated at lysine residue 9 (H3K9ac) and histone 3 acetylated at lysine residue 14 (H3K14ac)) were assessed in dams' and offspring' brains. Prenatal stress did not significantly influence maternal care; however, it induced manic behavior in female offspring. These behavioral alterations in the offspring were accompanied by hyperactivity of the HPA-axis, epigenetic adaptations in the activity of HDAC and DNMT, and acetylation in the histones H3K9 and H3K14. In addition, the prenatal stressed female offspring showed increased levels of ACTH compared to their male counterpart. Our findings reinforce the impact of prenatal stress on behavior, stress response, and epigenetic profile of offspring.

Hypothalamus and Post-Traumatic Stress Disorder: A Review

Humans have lived in a dynamic environment fraught with potential dangers for thousands of years. While fear and stress were crucial for the survival of our ancestors, today, they are mostly considered harmful factors, threatening both our physical and mental health. Trauma is a highly stressful, often life-threatening event or a series of events, such as sexual assault, war, natural disasters, burns, and car accidents. Trauma can cause pathological metaplasticity, leading to long-lasting behavioral changes and impairing an individual's ability to cope with future challenges. If an individual is vulnerable, a tremendously traumatic event may result in post-traumatic stress disorder (PTSD). The hypothalamus is critical in initiating hormonal responses to stressful stimuli via the hypothalamic-pituitary-adrenal (HPA) axis. Linked to the prefrontal cortex and limbic structures, especially the amygdala and hippocampus, the hypothalamus acts as a central hub, integrating physiological aspects of the stress response. Consequently, the hypothalamic functions have been attributed to the pathophysiology of PTSD. However, apart from the well-known role of the HPA axis, the hypothalamus may also play different roles in the development of PTSD through other pathways, including the hypothalamic-pituitary-thyroid (HPT) and hypothalamic-pituitary-gonadal (HPG) axes, as well as by secreting growth hormone, prolactin, dopamine, and oxytocin. This review aims to summarize the current evidence regarding the neuroendocrine functions of the hypothalamus, which are correlated with the development of PTSD. A better understanding of the role of the hypothalamus in PTSD could help develop better treatments for this debilitating condition.

Relationship between anxiety and depressive trajectories of women who conceived through assisted reproductive technology and their children's emotional and behavioral problems: A prospective cohort study

OBJECTIVE

This study aimed to examine the relationship between the anxiety and depressive trajectory of women conceived through assisted reproductive technology (ART) and their children's emotional and behavioral problems.

METHODS

This prospective cohort study including 18,711 women, was conducted between July 2014 and December 2017. Self-rating scales for anxiety and depression were used before treatment, during the first trimester, and two to three years postpartum. A latent class growth analysis identified their maternal anxiety and depressive symptom trajectories. Multiple comparison and linear regression models were performed to assess the relationships between maternal trajectories and their offspring's emotional and behavioral problems.

RESULTS

Three longitudinal heterogeneous trajectories of maternal anxiety and depressive symptoms were identified: resilient, recurrent, and emergent. After adjusting for covariates, children with mothers in the recurrent and emergent trajectory groups had higher Child Behavior Checklist/2-3 scores. Additionally, the participants with a recurrent trajectory had lower education and employment levels and younger maternal age at delivery. They also had a history of ovarian surgery, primipara, secondary infertility, polycystic ovary syndrome, and more embryo transferred cycles, including intracytoplasmic sperm injections. Those with resilient trajectories had higher antral follicle counts and GnRH antagonist protocol. Finally, the participants with emergent trajectories had a lower monthly income, primipara, ectopic pregnancy, and fresh embryo transfers.

CONCLUSIONS

Infertile women's psychological stress was not alleviated by the ART-sociodemographic, infertility-related and treatment-related characteristics determined three mental health trajectories. Children with mothers in recurrent and emergent trajectories showed higher odds of experiencing emotional and behavioral problems.

The brain as a source and a target of prolactin in mammals

Prolactin is a polypeptide hormone associated with an extensive variety of biological functions. Among the roles of prolactin in vertebrates, some were preserved throughout evolution. This is the case of its function in the brain, where prolactin receptors, are expressed in different structures of the central nervous system. In the brain, prolactin actions are principally associated with reproduction and parental behavior, and involves the modulation of adult neurogenesis, neuroprotection, and neuroplasticity, especially during pregnancy, thereby preparing the brain to parenthood. Prolactin is mainly produced by specialized cells in the anterior pituitary gland. However, during vertebrate evolution many other extrapituitary tissues do also produce prolactin, like the immune system, endothelial cells, reproductive structures and in several regions of the brain. This review summarizes the relevance of prolactin for brain function, the sources of prolactin in the central nervous system, as well as its local production and secretion. A highlight on the impact of prolactin in human neurological diseases is also provided.

Cesarean section delivery is a risk factor of autism-related behaviors in mice

Cesarean section (C/S) is one way of delivering babies, and is chosen when mothers or babies are facing problems or life-threatening conditions during pregnancy. Many meta-analyses have suggested an etiological relationship between C/S delivery and autism spectrum disorders (ASDs). However, as a risk factor for ASDs, C/S delivery has not yet been well studied. Because C/S deliveries have been increasing, it is very important to investigate the causal association between C/S and ASDs. Here, using three approaches, we showed experimentally that C/S delivery induced ASD-like traits in offspring mice, and that some of these changes were ameliorated by one-time oxytocin (OXT) treatment. Treatment with OXT receptor antagonists before natural delivery also induced ASD-related behaviors. Moreover, wild-type mice born to OXT-KO dams showed similar changes. Thus, insufficient OXT exposure from dams to offspring during delivery may be a trigger for ASD-related behaviors.

Prenatally traumatized mice reveal hippocampal methylation and expression changes of the stress-related genes Crhr1 and Fkbp5

In our previous study, we found that prenatal trauma exposure leads to an anxiety phenotype in mouse pups, characterized by increased corticosterone levels and increased anxiety-like behavior. In order to understand the mechanisms by which aversive in utero experience leads to these long-lasting behavioral and neuroendocrine changes, we investigated stress reactivity of prenatally traumatized (PT) mice, as well as the expression and methylation levels of several key regulatory genes of the stress axis in the dorsal hippocampus (dHPC) of the PT embryo and adult mice. We detected increased corticotropin-releasing hormone receptor 1 (Crhr1) and decreased FK506 binding protein 5 (Fkbp5) mRNA levels in the left dHPC of adult PT mice. These alterations were accompanied by a decreased methylation status of the Crhr1 promoter and an increased methylation status of the Fkbp5 promoter, respectively. Interestingly, the changes in Fkbp5 and Crhr1 mRNA levels were not detected in the embryonic dHPC of PT mice. Together, our findings provide evidence that prenatal trauma has a long-term impact on stress axis function and anxiety phenotype associated with altered Crhr1 and Fkbp5 transcripts and promoter methylation.

Associations between maternal depressive symptoms and risk for offspring early-life psychopathology: the role of genetic and non-genetic mechanisms

BACKGROUND

Although maternal depressive symptoms are robustly associated with offspring early-life psychopathology symptoms, it is not clear which potential mechanisms are at play. We aimed to estimate the relative importance of genetic transmission and direct environmental exposure in these associations on three occasions in early childhood.

METHODS

Biometric modeling of maternal sisters and their offspring from the Norwegian Mother and Child Cohort Study. The analyzed sample comprised 22 316 mothers and 35 589 offspring. Mothers reported their own depressive symptoms using the Symptom checklist, and offspring's concurrent symptoms of psychopathology using the Child Behavior Checklist at 1.5, 3, and 5 years postpartum.

RESULTS

Associations between maternal symptoms of depression and offspring emotional problems were predominantly explained by passive genetic transmission at 1.5 and 3 years postpartum. At age 5, associations were more due to direct environmental exposure. For offspring behavioral problems, there was no net increase in the importance of direct environmental exposure across occasions.

CONCLUSIONS

Associations between maternal depressive symptoms and offspring psychopathology symptoms remained after accounting for shared genes, consistent with a small, causal effect. For offspring emotional problems, this effect appeared to increase in importance over time. Our findings imply that treatment of maternal depressive symptoms could also benefit the offspring, and that genetic confounding should be considered in future studies of such mother-offspring associations.

Maternal emotions during the pre/postnatal periods and children's sleep behaviors: The mediating role of children's behavior

BACKGROUND

We aimed to investigate the association of mother's perceived levels of depression and happiness across all trimesters of pregnancy and after delivery on their children's sleep problems, as well as examine the possible mediating effect of children's behavioral problems.

METHODS

Participants included 1257 children (54% boys, mean age = 5.74 ± 0.48 years). Pre- and postnatal maternal emotions were self-reported using a 5-point scale for happiness and a 3-point scale for depressive emotions. Children reported sleep and behavioral problems using the Child Behavior Checklist.

RESULTS

Adjusted models showed that children of women reporting depressive emotions during either the postnatal period (β = 3.07, p = 0.01) or both prenatal and postnatal periods (β = 2.91, p = 0.01) were more likely to report sleep disturbances. By contrast, children of women reporting higher levels of happiness in the second (β = -1.91, p = 0.04) and third (β = -2.27, p = 0.001) trimesters were less likely to report sleep problems.

LIMITATIONS

Differences in maternal-report of children's behaviors could reflect memory and recall bias, and maternal emotions were assessed by researcher-designed single item measures. All measures were completed by a single reporter. Other associated factors should be considered in clarifying the complex associations.

CONCLUSIONS

Maternal depressive emotions during pre- and postnatal periods were associated with an increase in children's sleep problems, while increased happiness during pregnancy was associated with a decrease in children's sleep problems. Children's behavioral problems significantly mediated these relationships. To our knowledge, this is the first study to examine the relationship between maternal pre- and postnatal emotions and children's sleep behavior in an Asian sample.

Strain differences in maternal neuroendocrine and behavioral responses to stress and the relation to offspring cocaine responsiveness

Early life stress exposure, including prenatal stress (PNS), influences subsequent risk for many disorders, including substance abuse, and these effects interact with genetic factors to determine risk for disease. We previously demonstrated gene X environmental interactions across the BXD recombinant inbred mouse strain panel and their progenitor strains in PNS modulation of cocaine-induced reward and locomotion. Critical to dissecting genetic interactions with PNS is consideration of the modes of stress transmission to the offspring. Both maternal neuroendocrine responses during stress and subsequent maternal-offspring interactions following stress may serve as transmission modes for PNS-induced changes in cocaine responsiveness. Therefore, we characterized the maternal stress response by measuring restraint stress-induced plasma corticosterone (CORT) during gestation as well as effects of restraint stress on dam-pup contact in the first 10 postnatal days in BXD and progenitor mouse strains. Restraint stress interacted with strain to affect plasma CORT levels and dam-pup contact, indicating heritable variation of the maternal stress response. Furthermore, strain-level variance in maternal stress response correlated to the impact on cocaine response exhibited by adult offspring. These findings implicate multiple modes of maternal stress response in alterations of offspring drug responsiveness and indicate that assessment of maternal endocrine and behavioral responses during early life can be utilized to dissect the complex intersection of maternal factors, the response of the offspring and genetics.

Maternal prenatal depressive symptoms and risk for early-life psychopathology in offspring: genetic analyses in the Norwegian Mother and Child Birth Cohort Study

BACKGROUND

Maternal prenatal depression is a known risk factor for early-life psychopathology among offspring; however, potential risk transmission mechanisms need to be distinguished. We aimed to test the relative importance of passive genetic transmission, direct exposure, and indirect exposure in the association between maternal prenatal depressive symptoms and early-life internalising and externalising psychopathology in offspring.

METHODS

We used structural equation modelling of phenotypic data and genetically informative relationships from the families of participants in the Norwegian Mother and Child Birth Cohort Study (MoBa). The analytic subsample of MoBa used in the current study comprises 22 195 mothers and 35 299 children. We used mothers' self-reported depressive symptoms during pregnancy, as captured by the Symptom Checklist, and their reports of symptoms of psychopathology in their offspring during the first few years of life (measured at 18, 36, and 60 months using the Child Behavior Checklist).

FINDINGS

Maternal prenatal depressive symptoms were found to be associated with early-life psychopathology primarily via intergenerationally shared genetic factors, which explained 41% (95% CI 36-46) of variance in children's internalising problems and 37% (30-44) of variance in children's externalising problems. For internalising problems, phenotypic transmission also contributed significantly, accounting for 14% (95% CI 5-19) of the association, but this contribution was found to be explained by exposure to concurrent maternal depressive symptoms, rather than by direct exposure in utero.

INTERPRETATION

Associations between maternal prenatal depressive symptoms and offspring behavioural outcomes in early childhood are likely to be at least partially explained by shared genes. This genetic confounding should be considered when attempting to quantify risks posed by in-utero exposure to maternal depressive symptoms.

FUNDING

UK Economic and Social Research Council, Norwegian Research Council, Norwegian Ministries of Health and Care Services, and Education & Research, Wellcome Trust, Royal Society, and National Institute for Health Research.

Prenatal influences on temperament development: The role of environmental epigenetics

This review summarizes current knowledge and outlines future directions relevant to questions concerning environmental epigenetics and the processes that contribute to temperament development. Links between prenatal adversity, epigenetic programming, and early manifestations of temperament are important in their own right, also informing our understanding of biological foundations for social-emotional development. In addition, infant temperament attributes represent key etiological factors in the onset of developmental psychopathology, and studies elucidating their prenatal foundations expand our understanding of developmental origins of health and disease. Prenatal adversity can take many forms, and this overview is focused on the environmental effects of stress, toxicants, substance use/psychotropic medication, and nutrition. Dysregulation associated with attention-deficit/hyperactivity-disruptive disorders was noted in the context of maternal substance use and toxicant exposures during gestation, as well as stress. Although these links can be made based on the existing literature, currently few studies directly connect environmental influences, epigenetic programming, and changes in brain development/behavior. The chain of events starting with environmental inputs and resulting in alterations to gene expression, physiology, and behavior of the organism is driven by epigenetics. Epigenetics provides the molecular mechanism of how environmental factors impact development and subsequent health and disease, including early brain and temperament development.

The intrauterine environment affects learning ability of Tokai high avoider rat offspring derived using cryopreservation and embryo transfer-mediated reproduction

Embryo transfer (ET) to recipient female animals is a useful technique in biological and experimental animal studies. While cryopreservation of two-cell stage rat embryos and ET to recipient rats are currently well-defined, it is unknown whether these artificial reproductive techniques and maternal factors affect offspring phenotype, particularly higher brain functions. Therefore, we assessed the effects of cryopreservation, ET, and maternal care on learning behaviour of the offspring, using Tokai high avoider (THA) rats that have a high learning ability phenotype. We found that the high learning ability of THA rat offspring was not replicated following ET to surrogate Wistar rats with a low-avoidance phenotype. Additionally, the characteristic phenotype of offspring obtained through mating of ET-derived rats was similar to that of THA rats. A postnatal cross-fostering investigation with the offspring of Wistar and THA rats showed that maternal behaviour, including postnatal care and lactation traits, did not differ between the dams of low-avoidance Wistar rats and THA rats; therefore, learning behaviour was retained in both Wistar and THA rat offspring. We conclude that the offspring phenotype, although unchanged, has an imperceptible effect on the learning ability of ET-derived THA rats through the intrauterine environment of the recipient.

Cross-fostering: Elucidating the effects of gene×environment interactions on phenotypic development

Cross-fostering of litters from soon after birth until weaning is a valuable tool to study the ways in which gene×environment interactions program the development of neural, physiological and behavioral characteristics of mammalian species. In laboratory mice and rats, the primary focus of this review, cross-fostering of litters between mothers of different strains or treatment groups (intraspecific) or between mothers of different species (interspecific) has been conducted over the past 9 decades. Areas of particular interest have included maternal effects on emotionality, social preferences, responses to stressful stimulation, nutrition and growth, blood pressure regulation, and epigenetic effects on brain development and behavior. Results from these areas of research highlight the critical role of the postnatal maternal environment in programming the development of offspring phenotypic characteristics. In addition, experimental paradigms that have included cross-fostering have permitted investigators to tease apart prenatal versus postnatal effects of various treatments on offspring development and behavior.

Analysis of within Subjects Variability in Mouse Ultrasonic Vocalization: Pups Exhibit Inconsistent, State-Like Patterns of Call Production

Mice produce ultrasonic vocalizations (USV) in multiple communicative contexts, including adult social interaction (e.g., male to female courtship), as well as pup calls when separated from the dam. Assessment of pup USV has been widely applied in models of social and communicative disorders, dozens of which have shown alterations to this conserved behavior. However, features such as call production rate can vary substantially even within experimental groups and it is unclear to what extent aspects of USV represent stable trait-like influences or are vulnerable to an animal's state. To address this question, we have employed a mixed modeling approach to describe consistency in USV features across time, leveraging multiple large cohorts recorded from two strains, and across ages/times. We find that most features of pup USV show consistent patterns within a recording session, but inconsistent patterns across postnatal development. This supports the conclusion that pup USV is most strongly influenced by "state"-like variables. In contrast, adult USV call rate and call duration show higher consistency across sessions and may reflect a stable "trait." However, spectral features of adult song such as the presence of pitch jumps do not show this level of consistency, suggesting that pitch modulation is more susceptible to factors affecting the animal's state at the time of recording. Overall, the utility of this work is three-fold. First, as variability necessarily affects the sensitivity of the assay to detect experimental perturbation, we hope the information provided here will be used to help researchers plan sufficiently powered experiments, as well as prioritize specific ages to study USV behavior and to decide which features to consider most strongly in analysis. Second, via the mouseTube platform, we have provided these hundreds of recordings and associated data to serve as a shared resource for other researchers interested in either benchmark data for these strains or in developing algorithms for studying features of mouse song. Finally, we hope that this work informs both interpretation of USV studies in models of developmental disorder, and helps to further research into understanding the neural processes that contribute to the production and predictability of USV behavior.

Prenatal stressors in rodents: Effects on behavior

The current review focuses on studies in rodents published since 2008 and explores possible reasons for any differences they report in the effects of gestational stress on various types of behavior in the offspring. An abundance of experimental data shows that different maternal stressors in rodents can replicate some of the abnormalities in offspring behavior observed in humans. These include, anxiety, in juvenile and adult rats and mice, assessed in the elevated plus maze and open field tests and depression, detected in the forced swim and sucrose-preference tests. Deficits were reported in social interaction that is suggestive of pathology associated with schizophrenia, and in spatial learning and memory in adult rats in the Morris water maze test, but in most studies only males were tested. There were too few studies on the novel object recognition test at different inter-trial intervals to enable a conclusion about the effect of prenatal stress and whether any deficits are more prevalent in males. Among hippocampal glutamate receptors, NR2B was the only subtype consistently reduced in association with learning deficits. However, like in humans with schizophrenia and depression, prenatal stress lowered hippocampal levels of BDNF, which were closely correlated with decreases in hippocampal long-term potentiation. In mice, down-regulation of BDNF appeared to occur through the action of gene-methylating enzymes that are already increased above controls in prenatally-stressed neonates. In conclusion, the data obtained so far from experiments in rodents lend support to a physiological basis for the neurodevelopmental hypothesis of schizophrenia and depression.