Preconception paternal stress in rats alters dendritic morphology and connectivity in the brain of developing male and female offspring

The effects of early-life and intergenerational stress on the brain

Stress experienced during ontogeny can have profound effects on the adult phenotype. However, stress can also be experienced intergenerationally, where an offspring's phenotype can be moulded by stress experienced by the parents. Although early-life and intergenerational stress can alter anatomy, physiology, and behaviour, nothing is known about how these stress contexts interact to affect the neural phenotype. Here, we examined how early-life and intergenerational stress affect the brain in eastern fence lizards (Sceloporus undulatus). Some lizard populations co-occur with predatory fire ants, and stress from fire ant attacks exerts intergenerational physiological and behavioural changes in lizards. However, it is unclear if intergenerational stress, or the interaction between intergenerational and early-life stress, modulates the brain. To test this, we captured gravid females from fire ant invaded and uninvaded populations, and subjected offspring to three early-life stress treatments: (1) fire ant attack, (2) corticosterone, or (3) a control. Corticosterone and fire ant attack decreased some aspects of the neural phenotype while population of origin and the interaction of early-life stress and population had no effects on the brain. These results suggest that early-life stressors may better predict adult brain variation than intergenerational stress in this species.

Preconception maternal posttraumatic stress and child negative affectivity: Prospectively evaluating the intergenerational impact of trauma

The developmental origins of psychopathology begin before birth and perhaps even prior to conception. Understanding the intergenerational transmission of psychopathological risk is critical to identify sensitive windows for prevention and early intervention. Prior research demonstrates that maternal trauma history, typically assessed retrospectively, has adverse consequences for child socioemotional development. However, very few prospective studies of preconception trauma exist, and the role of preconception symptoms of posttraumatic stress disorder (PTSD) remains unknown. The current study prospectively evaluates whether maternal preconception PTSD symptoms predict early childhood negative affectivity, a key dimension of temperament and predictor of later psychopathology. One hundred and eighteen women were recruited following a birth and prior to conception of the study child and were followed until the study child was 3-5 years old. Higher maternal PTSD symptoms prior to conception predicted greater child negative affectivity, adjusting for concurrent maternal depressive symptoms and sociodemographic covariates. In exploratory analyses, we found that neither maternal prenatal nor postpartum depressive symptoms or perceived stress mediated this association. These findings add to a limited prospective literature, highlighting the importance of assessing the mental health of women prior to conception and providing interventions that can disrupt the intergenerational sequelae of trauma.

Association of adverse childhood experience-related increase in neurite density with sensory over-responsivity in autism spectrum disorder: A neurite orientation dispersion and density imaging study

Sensory over-responsivity (SOR) causes social and daily distress in individuals with autism spectrum disorder (ASD). Compared to typically developed (TD) individuals, ASD individuals are at higher risk of adverse childhood experiences (ACEs), which induce abnormal neuronal development. However, whether or how ACEs are associated with abnormal neural development and SOR in ASD remains to be determined. Forty-five individuals with ASD and 43 TD individuals underwent T1-weighted and neurite orientation dispersion and density imaging; the axonal and dendritic densities were defined as the neurite density index (NDI). Voxel-based analyses were performed to explore the brain regions associated with SOR. The relationships between severity of ACEs and SOR, and NDI in the brain regions were examined. ASD individuals showed a significantly positive association between SOR severity and NDI in the right superior temporal gyrus (STG), which was not found in TD individuals. Severity of ACEs correlated significantly with that of SOR and NDI in the right STG in ASD; ASD individuals having severe SOR showed significantly higher NDI in the right STG than those with mild SOR and TD individuals. In individuals with ASD, NDI in the right STG, but not ACEs, could predict the severity of SOR, which was not shown in TD subjects. Our findings suggest that severe ACEs are involved in excessive neurite density in the right STG in ASD. ACE-associated excessive neurite density in the right STG is critical for SOR in ASD, which may be a therapeutic target in the future.

Paternal stress alters synaptic density and expression of GAP-43, GRIN1, M1 and SYP genes in the hippocampus and cortex of offspring of stress-induced male rats

Adverse experiences during pregnancy have a negative impact on the neuronal structure and behavior of offspring, but the effects of a father's life events on the outcome of progeny are scarce. The present study is intended to investigate whether paternal stress affects the offspring brain structure, especially those regions concerned with learning and formation of memory, namely the hippocampus (HC) and prefrontal cortex (PFC), and also the expression of certain genes linked to learning and memory in the offspring. Induced stress to male rats by five stressors, one per day followed by allowing them to mate with the normal, unstressed female. Synaptophysin immunoreactivity was assessed in the tissue sections of the HC and PFC as well as expression of genes concerned with learning and memory was evaluated by RT-PCR in the progeny of stress-received males. The progeny of stressed rats had reduced antisynaptophysin immunoreactivity in the HC and PFC. The synaptic density in HC was less in the A-S (Offspring of male rats who received stress during adulthood) and PA-S (offspring of male rats who received stress during both adolescence and adulthood) than in P-S (offspring of male rats who received stress during adolescence) and C-C (offspring of control) groups. Similar results were observed even in the PFC. The results of post hoc tests proved that the HC and PFC of the progeny of stress-exposed rats exhibited considerably less synaptic density than control (P<0.05), and the levels of expression of GAP-43, GRIN1, M1, and SYP genes in HC and PFC were down-regulated. This study concludes that paternal adverse experiences can affect the offspring's synaptic plasticity and also the genes, which can regulate learning and formation of memory.

Early-Life Environment Influence on Late-Onset Alzheimer's Disease

With the expand of the population's average age, the incidence of neurodegenerative disorders has dramatically increased over the last decades. Alzheimer disease (AD) which is the most prevalent neurodegenerative disease is mostly sporadic and primarily characterized by cognitive deficits and neuropathological lesions such as amyloid -β (Aβ) plaques and neurofibrillary tangles composed of hyper- and/or abnormally phosphorylated Tau protein. AD is considered a complex disease that arises from the interaction between environmental and genetic factors, modulated by epigenetic mechanisms. Besides the well-described cognitive decline, AD patients also exhibit metabolic impairments. Metabolic and cognitive perturbations are indeed frequently observed in the Developmental Origin of Health and Diseases (DOHaD) field of research which proposes that environmental perturbations during the perinatal period determine the susceptibility to pathological conditions later in life. In this review, we explored the potential influence of early environmental exposure to risk factors (maternal stress, malnutrition, xenobiotics, chemical factors … ) and the involvement of epigenetic mechanisms on the programming of late-onset AD. Animal models indicate that offspring exposed to early-life stress during gestation and/or lactation increase both AD lesions, lead to defects in synaptic plasticity and finally to cognitive impairments. This long-lasting epigenetic programming could be modulated by factors such as nutriceuticals, epigenetic modifiers or psychosocial behaviour, offering thus future therapeutic opportunity to protect from AD development.

Maternal stress prior to conception impairs memory and decreases right dorsal hippocampal volume and basilar spine density in the prefrontal cortex of adult male offspring

Chronic parental stress impacts offspring functioning throughout life. Chronic variable stress prior to conception impairs offspring development in terms of behavior, neuroanatomy, and neurobiology. Previously, our lab demonstrated that even a consistent stressor experienced by the sire or the dam shapes offspring development beginning in early life. Here, we show how consistent maternal stress prior to conception influences the brain and behavior of offspring in adolescence and adulthood. Female Long-Evans rats were exposed to elevated platform stress twice daily for 27 consecutive days immediately prior to mating with non-stressed males. Male and female offspring were assessed in the open field and elevated plus maze in adolescence, and open field, elevated plus maze, Whishaw tray reaching, and Morris water task in adulthood. Offspring were then euthanized, and their brains were stained with Golgi-Cox solution and then examined for dendritic spine density and hippocampal volume. Major findings include deficits in spatial memory, decreased medial prefrontal cortex spine density, and reduced right dorsal hippocampal volume in male offspring only. This work illustrates that the effects of consistent maternal stress prior to conception are lifelong and highly sexually dimorphic.

Impact of paternal presence and parental social-demographic characteristics on birth outcomes

OBJECTIVES

Maternal race, marital status, and social environment impact risk of preterm delivery and size for gestational age. Although some paternal characteristics such as age are associated with pregnancy outcomes, the influence of the paternal presence, race/ethnicity and adverse life events is not well known. The objective of the study was to assess birth outcomes in mothers with a paternal presence compared to those without during the post-partum period. The secondary aim was to determine whether paternal race is associated with birth outcomes.

METHODS

This was a cross-sectional study using parental surveys linked with birth certificate data from 2016 to 2018. Adverse birth composite outcomes (ABCO) including small for gestational age (SGA), prematurity or neonatal intensive care unit admission (NICU) were assessed.

RESULTS

A total of 695 parents were analyzed (239 single mothers and 228 mother-father pairs). Compared to mothers with a father present, mothers without a father present exhibited increased odds of ABCO, prematurity and NICU. Non-Hispanic Black fathers had increased odds of ABCO and NICU compared to Non-Hispanic Whites (NHW). Hispanic fathers had increased odds of NICU compared to NHW.

CONCLUSIONS

Paternal absence in the post-partum period and paternal race were both independently associated with ABCO and NICU. Assessment of paternal presence and paternal race in clinical practice may help identify opportunities for additional support necessary to optimize birth outcomes.

The stressed orbitofrontal cortex

Stressor exposure causes dendritic remodeling on excitatory neurons in multiple regions of the brain, including the orbitofrontal cortex (OFC). Additionally, stressor and exogenous stress hormone exposure impair cognitive functions that are dependent on the OFC. For this Special Issue on the OFC, we summarize current literature regarding how stress-prenatal, postnatal, and even inter-generational-affects OFC neuron structure in rodents. We discuss dendrite structure, dendritic spines, and gene expression. We aim to provide a focused resource for those interested in how stressors impact this heterogeneous brain region. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Mapping the past, present and future research landscape of paternal effects

BACKGROUND

Although in all sexually reproducing organisms an individual has a mother and a father, non-genetic inheritance has been predominantly studied in mothers. Paternal effects have been far less frequently studied, until recently. In the last 5 years, research on environmentally induced paternal effects has grown rapidly in the number of publications and diversity of topics. Here, we provide an overview of this field using synthesis of evidence (systematic map) and influence (bibliometric analyses).

RESULTS

We find that motivations for studies into paternal effects are diverse. For example, from the ecological and evolutionary perspective, paternal effects are of interest as facilitators of response to environmental change and mediators of extended heredity. Medical researchers track how paternal pre-fertilization exposures to factors, such as diet or trauma, influence offspring health. Toxicologists look at the effects of toxins. We compare how these three research guilds design experiments in relation to objects of their studies: fathers, mothers and offspring. We highlight examples of research gaps, which, in turn, lead to future avenues of research.

CONCLUSIONS

The literature on paternal effects is large and disparate. Our study helps in fostering connections between areas of knowledge that develop in parallel, but which could benefit from the lateral transfer of concepts and methods.

Critical period regulation across multiple timescales

Brain plasticity is dynamically regulated across the life span, peaking during windows of early life. Typically assessed in the physiological range of milliseconds (real time), these trajectories are also influenced on the longer timescales of developmental time (nurture) and evolutionary time (nature), which shape neural architectures that support plasticity. Properly sequenced critical periods of circuit refinement build up complex cognitive functions, such as language, from more primary modalities. Here, we consider recent progress in the biological basis of critical periods as a unifying rubric for understanding plasticity across multiple timescales. Notably, the maturation of parvalbumin-positive (PV) inhibitory neurons is pivotal. These fast-spiking cells generate gamma oscillations associated with critical period plasticity, are sensitive to circadian gene manipulation, emerge at different rates across brain regions, acquire perineuronal nets with age, and may be influenced by epigenetic factors over generations. These features provide further novel insight into the impact of early adversity and neurodevelopmental risk factors for mental disorders.

Bound Together: How Psychoanalysis Diminishes Inter-generational DNA Trauma

The concept of intergenerational transmission of trauma plays a fundamental role in psychoanalysis. While it is known that intergenerational trauma can be transmitted through attachment relationships, a new branch of genetics (epigenetics) has emerged to study the interaction between human behavior and changes in DNA expression. Therefore, psychoanalysis, which has proven to reduce the intergenerational transmission of trauma from a behavioral perspective, can play a positive role in regulating DNA changes caused by environmental stress. The present paper focuses on recent research suggesting a direct correlation between psychological trauma and DNA modifications. In particular, DNA changes caused by psychological trauma can be transmitted from generation to generation, validating the psychoanalytic concept of intergenerational transmission of trauma. This evidence not only supports the essential role psychoanalysis has in influencing human behavior, but also suggests that it affects not only the individuals who undergo it but their offspring, as well, via the epigenetic passage of DNA.

The neural mechanisms and consequences of paternal caregiving

In recent decades, human sociocultural changes have increased the numbers of fathers that are involved in direct caregiving in Western societies. This trend has led to a resurgence of interest in understanding the mechanisms and effects of paternal care. Across the animal kingdom, paternal caregiving has been found to be a highly malleable phenomenon, presenting with great variability among and within species. The emergence of paternal behaviour in a male animal has been shown to be accompanied by substantial neural plasticity and to be shaped by previous and current caregiving experiences, maternal and infant stimuli and ecological conditions. Recent research has allowed us to gain a better understanding of the neural basis of mammalian paternal care, the genomic and circuit-level mechanisms underlying paternal behaviour and the ways in which the subcortical structures that support maternal caregiving have evolved into a global network of parental care. In addition, the behavioural, neural and molecular consequences of paternal caregiving for offspring are becoming increasingly apparent. Future cross-species research on the effects of absence of the father and the transmission of paternal influences across generations may allow research on the neuroscience of fatherhood to impact society at large in a number of important ways.

Prenatal programming of stress responsiveness and behaviours: Progress and perspectives

Parental exposure to stress or glucocorticoids either before or during pregnancy can have profound influences on neurodevelopment, neuroendocrine function and behaviours in offspring. Specific outcomes are dependent on the nature, intensity and timing of the exposure, as well as species, sex and age of the subject. Most recently, it has become evident that outcomes are not confined to first-generation offspring and that there may be intergenerational and transgenerational transmission of effects. There has been intense focus on the mechanisms by which such early exposure leads to long-term and potential transgenerational outcomes, and there is strong emerging evidence that epigenetic processes (histone modifications, DNA methylation, and small non-coding RNAs) are involved. New knowledge in this area may allow the development of interventions that can prevent, ameliorate or reverse the long-term negative outcomes associated with exposure to early adversity. This review will focus on the latest research, bridging human and pre-clinical studies, and will highlight some of the limitations, challenges and gaps that exist in the field.

Research Review: Intergenerational transmission of disadvantage: epigenetics and parents' childhoods as the first exposure

BACKGROUND

For decades, economists and sociologists have documented intergenerational transmission of socioeconomic disadvantage, demonstrating that economic, political, and social factors contribute to 'inherited hardship'. Drawing on biological factors, the developmental origins of adult health and disease model posits that fetal exposure to maternal prenatal distress associated with socioeconomic disadvantage compromises offspring's neurodevelopment, affecting short- and long-term physical and mental health, and thereby psychosocial standing and resources. Increasing evidence suggests that mother-to-child influence occurs prenatally, in part via maternal and offspring atypical HPA axis regulation, with negative effects on the maturation of prefrontal and subcortical neural circuits in the offspring. However, even this in utero timeframe may be insufficient to understand biological aspects of the transmission of factors contributing to disadvantage across generations.

METHODS

We review animal studies and emerging human research indicating that parents' childhood experiences may transfer epigenetic marks that could impact the development of their offspring independently of and in interaction with their offspring's perinatal and early childhood direct exposures to stress stemming from socioeconomic disadvantage and adversity.

RESULTS

Animal models point to epigenetic mechanisms by which traits that could contribute to disadvantage may be transmitted across generations. However, epigenetic pathways of parental childhood experiences influencing child outcomes in the next generation are only beginning to be studied in humans. With a focus on translational research, we point to design features and methodological considerations for human cohort studies to be able to test the intergenerational transmission hypothesis, and we illustrate this with existing longitudinal studies.

CONCLUSIONS

Epigenetic intergenerational transmission, if at play in human populations, could have policy implications in terms of reducing the continuation of disadvantage across generations. Further research is needed to address this gap in the understanding of the perpetuation of compromised lives across generations.

Maternal Preconception Stress Alters Prefrontal Cortex Development in Long-Evans Rat Pups without Changing Maternal Care

Stress during development can shift the typical developmental trajectory. Maternal stress prior to conception has recently been shown to exert similar influences on the offspring. The present study questioned if a consistent maternal stressor prior to conception (elevated platform stress) would impact the pre-weaning development of offspring brain and behavior, and if maternal care was vulnerable to this experience. Adult female Long-Evans rats were subjected to elevated platform stress for 27 days prior to mating with non-stressed males. Maternal care was monitored, and pups were assessed in two tests of early behavioral development, negative geotaxis and open field. Pups were perfused at weaning and their brains were extracted and stained with Cresyl Violet, allowing gross measurements of cortical and subcortical structures and estimates of neuron density. Main findings indicate that a change in prefrontal cortical thickness is evident despite no change in maternal care. Female offspring show a decrease in medial-dorsal thalamus size. The current study failed to find an effect of maternal preconception stress on early behavioral development. These results suggest that the PFC, and likely behavior dependent on the PFC, is vulnerable to maternal preconception stress and that a strong sex effect is evident. Further studies should examine how such offspring fare using a lifespan model and investigate potential mechanisms responsible for these effects.

Preconception Paternal Stress in Rats Alters Brain and Behavior in Offspring

Whereas environmental challenges during gestation have been repeatedly shown to alter offspring brain architecture and behavior, exploration examining the consequences of paternal preconception experience on offspring outcome is limited. The goal of this study was to examine the effects of preconception paternal stress (PPS) on cerebral plasticity and behavior in the offspring. Several behavioral assays were performed on offspring between postnatal days 33 (P33) and 101 (P101). Following behavioral testing, the brains were harvested and dendritic morphology (dendritic complexity, length, and spine density) were examined on cortical pyramidal cells in medial prefrontal cortex (mPFC), orbital frontal cortex (OFC), parietal cortex (Par1), and the CA1 area of the hippocampus. As anticipated, behavior was altered on both the activity box assay and elevated plus maze and performance was impaired in the Whishaw tray reaching task. Neuroanatomical measures revealed a heavier brain in stressed animals and dendritic changes in all regions measured, the precise effect varying with the measure and cerebral region. Thus, PPS impacted both behavior and neuronal morphology of offspring. These effects likely have an epigenetic basis given that in a parallel study of littermates of the current animals we found extensive epigenetic changes at P21.

Effects of mothers' and fathers' experience with predation risk on the behavioral development of their offspring in threespined sticklebacks

Stressors experienced by parents can influence the behavioral development of their offspring. Here, we review recent studies in threespined sticklebacks (a species in which males are the sole providers of parental care) showing that when parents are exposed to an ecologically relevant stressor (predation risk), there are consequences for offspring. For example, female sticklebacks exposed to predation risk produce eggs with higher concentrations of cortisol, a stress hormone, and offspring with altered behavior and physiology. Male sticklebacks exposed to predation risk produce offspring that are less active, smaller, and in poorer condition. The precise mechanisms by which maternal and paternal experiences with predators affect offspring phenotypes are under investigation, and could include steroid hormones, olfactory cues and/or parental behavior. As in other species, some of the consequences of parental exposure to predation risk for offspring in sticklebacks might be adaptive, but depend on the stressor, the reliability of the parental and offspring environments and the evolutionary history of the population.