Molecular mechanisms underlying the models of neurodevelopmental disorders in maternal immune activation relevant to the placenta

Maternal immune activation induces autism-like behavior and reduces brain-derived neurotrophic factor levels in the hippocampus and offspring cortex of C57BL/6 mice

Prenatal factors such as viral or bacterial infections occurring mainly during the first trimesters of pregnancy can increase the incidence of autism spectrum disorder (ASD) in children. In an animal model, it is already known that maternal immune activation (MIA) induces autistic-like behavior. However, it is unclear whether this behavior presents itself in young animals. In this preclinical experimental study, we investigated in the offspring of C57BL/6 female mice submitted to MIA with lipopolysaccharide (LPS), typically altered behaviors in ASD, such as social interaction and stereotyped self-grooming movement, as well as the levels of the brain-derived neurotrophic factor (BDNF) and interleukin 17A (IL-17A) in the hippocampus and cortex, at 28 and 60 days. Adult animals aged 60 days, offspring of females submitted to MIA, showed a decrease in the time of social interaction and an increase in the number of self-cleaning movements. In the hippocampus of the offspring of females submitted to MIA, a decrease in BDNF levels was found at 28 days and 60 days of life, and a decrease in IL-17A levels only at 60 days. The levels of BDNF and IL-17A did not change in the cortex of the offspring of mice submitted to MIA at the evaluated times. Young animals aged 28 days still showed typical behavior, without social deficits and stereotyped movements that characterize ASD, which suggests that at this age it is still not possible to observe the repercussions of MIA in this model. In the neurochemical issues of the hippocampal region, impairment of BDNF levels has already been demonstrated, which may be an important factor for the observation of ASD-like behaviors in adult mice at 60 days.

LIF-IGF Axis Contributes to the Proliferation of Neural Progenitor Cells in Developing Rat Cerebrum

In rodent models, leukemia inhibitory factor (LIF) is involved in cerebral development via the placenta, and maternal immune activation is linked to psychiatric disorders in the child. However, whether LIF acts directly on neural progenitor cells (NPCs) remains unclear. This study performed DNA microarray analysis and quantitative RT-PCR on the fetal cerebrum after maternal intraperitoneal or fetal intracerebral ventricular injection of LIF at day 14.5 (E14.5) and determined that the expression of insulin-like growth factors (IGF)-1 and -2 was induced by LIF. Physiological IGF-1 and IGF-2 levels in fetal cerebrospinal fluid (CSF) increased from E15.5 to E17.5, following the physiological surge of LIF levels in CSF at E15.5. Immunostaining showed that IGF-1 was expressed in the cerebrum at E15.5 to E19.5 and IGF-2 at E15.5 to E17.5 and that IGF-1 receptor and insulin receptor were co-expressed in NPCs. Further, LIF treatment enhanced cultured NPC proliferation, which was reduced by picropodophyllin, an IGF-1 receptor inhibitor, even under LIF supplementation. Our findings suggest that IGF expression and release from the NPCs of the fetal cerebrum in fetal CSF is induced by LIF, thus supporting the involvement of the LIF-IGF axis in cerebral cortical development in an autocrine/paracrine manner.

Influences of the Immune System and Microbiome on the Etiology of ASD and GI Symptomology of Autistic Individuals

Autism Spectrum Disorder is a developmental condition associated with impairments in communication and social interactions, and repetitive and restricted behavior or interests. Autistic individuals are more likely to experience gastrointestinal (GI) symptoms than neurotypical individuals. This may be partially due to dysbiosis of the gut microbiome. In this article, we describe the interaction of the microbiome and immune system on autism etiology. We also summarize the links between the microbiome and gastrointestinal and related symptoms among autistic individuals. We report that microbial interventions, including diet, probiotics, antibiotics, and fecal transplants, and immune-modulating therapies such as cytokine blockade during the preconception, pregnancy, and postnatal period may impact the neurodevelopment, behavior, and gastrointestinal health of autistic individuals.

Maternal infection during pregnancy and the risk of attention-deficit/hyperactivity disorder in the offspring: A systematic review and meta-analysis

BACKGROUND

The effects of maternal infection during pregnancy on the risk of attention-deficit/hyperactivity disorder (ADHD) in the offspring are unclear, and no overview is available.

METHODS

We searched the PubMed and EMBASE databases for relevant studies and performed a systematic review and meta-analysis of the literature.

RESULTS

We found that that maternal infection during pregnancy was associated with a small increase in the risk of ADHD (OR 1.25, 95% CI 1.09, 1.44, P < 0.0001; I² = 92.9%, p < 0.0001) in the offspring. In subgroup analyses, the association remained for maternal genitourinary (GU) infection (OR, 1.19, 1.12, 1.27, P < 0.001; I² = 0%; p = 0.517). However, there was no significant association when we pooled data from siblings from other pregnancies (OR = 1.06, 95% CI, 0.99-1.13, P = 0.084; I² = 0%; p = 0.859), implying that the association was due to confounding.

CONCLUSIONS

The statistically significant association between maternal infection during pregnancy and ADHD in the offspring can be partially explained by unmeasured confounding.

LPS vs. Poly I:C Model: Comparison of Long-Term Effects of Bacterial and Viral Maternal Immune Activation (MIA) on the Offspring

A prominent health issue nowadays is the COVID-19 pandemic, which poses acute risks to human health. However, the long-term health consequences are largely unknown and cannot be neglected. An especially vulnerable period for infection is pregnancy, when infections could have long-term health effect on the child. Evidence suggests that maternal immune activation (MIA) induced by either bacteria or viruses presents various effects on the offspring, leading to adverse phenotypes in many organ systems. This review compares the mechanisms of bacterial and viral MIA and the possible long-term outcomes for the offspring by summarizing the outcome in animal LPS and Poly I:C models. Both models are activated immune responses mediated by Toll-like receptors. The outcomes for MIA offspring include neurodevelopment, immune response, circulation, metabolism, and reproduction. Some of these changes continue to exist until later life. Besides different doses and batches of LPS and Poly I:C, the injection day, administration route, and also different animal species influence the outcomes. Here, we specifically aim to support colleagues when choosing their animal models for future studies.

Stage-dependent function of Wnt5a during male external genitalia development

External genitalia development in mice involves multiple developmental processes under the regulation of various signaling pathways. Wnt5a, one of the major Wnt ligands, is a crucial developmental regulator of outgrowing organs such as the limb, the mandible, and the external genitalia. Defects in Wnt5a signaling have been linked to Robinow syndrome, a genetic disorder in which male patients manifest a micropenis and defective urethral tube formation. Whereas Wnt5a is required for cell proliferation during embryonic external genitalia outgrowth, its role for urethral tube formation has yet to be understood. Here, we show that Wnt5a contributes to urethral tube formation as well as external genitalia outgrowth. Wnt5a is expressed in the embryonic external genitalia mesenchyme, and mesenchymal-specific conditional Wnt5a knockout mice resulted in hypospadias-like urethral defects. Early deletion of Wnt5a at E10.5 showed severe defects in both external genitalia outgrowth and urethral tube formation, along with reduced cell proliferation. The severe urethral tube defect persisted during later timing deletion of Wnt5a (E13.5). Further analyses revealed that loss of Wnt5a disrupted cell polarity and led to a reduction of the phosphorylated myosin light chain and the focal adhesion protein, vinculin. Altogether, these results suggest that Wnt5a coordinates cell proliferation and directed cell migration in a stage-dependent manner during male external genitalia development. Furthermore, Wnt5a may regulate cell polarity, focal adhesion formation, and cell contractility, leading to directed cell migration during male-type urethral formation in a manner that has not been reported in other organ fusion events.

Mid-pregnancy maternal immune activation increases Pax6-positive and Tbr2-positive neural progenitor cells and causes integrated stress response in the fetal brain in a mouse model of maternal viral infection

Maternal immune activation (MIA) in midpregnancy is a risk factor for neurodevelopmental disorders. Improper brain development may cause malformations of the brain; maldevelopment induced by MIA may lead to a pathology-related phenotype. In this study, a single intraperitoneal injection of 20 mg/kg polyriboinosinic–polyribocytidylic acid [poly(I:C)] was administered to C57BL/6J mice on embryonic day (E) 12.5 to mimic maternal viral infection. Histopathological analysis of neurogenesis was performed using markers for Pax6, Tbr2, and Tbr1. In these fetuses, significant increases were observed in the proportion of Pax6-positive neural progenitor cells and Pax6/Tbr2 double-positive cells 24 h after poly(I:C) injection. There were no differences in the proportion of Tbr1-positive postmitotic neurons 48 h after poly(I:C) injection. At E18.5, there were more Pax6-positive and Tbr2-positive neural progenitor cells in the poly(I:C)-injected group than in the saline-injected group. Gene ontology enrichment analysis of poly(I:C)-induced differentially expressed genes in the fetal brain at E12.5 demonstrated that these genes were enriched in terms including response to cytokine, response to decreased oxygen levels in the category of biological process. At E13.5, activating transcription factor 4 (Atf4), which is an effector of integrated stress response, was significantly upregulated in the fetal brain. Our results show that poly(I:C)-induced MIA at E12.5 leads to dysregulated neurogenesis and upregulates Atf4 in the fetal brain. These findings provide a new insight in the mechanism of MIA causing improper brain development and subsequent neurodevelopmental disorders.

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MIA increases Pax6-positive and Tbr2-positive neural progenitor cells.

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MIA impaired the process of neurogenesis from as early as the acute stage.

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MIA upregulated Atf4, an effector of integrated stress response, in the fetal brain.

Leukemia Inhibitory Factor Induces Proopiomelanocortin via CRH/CRHR Pathway in Mouse Trophoblast

We previously showed that maternal leukemia inhibitory factor (LIF) induces placental production of adrenocorticotropic hormone (ACTH), which stimulates fetal nucleated red blood cells to further secrete LIF and promote neurogenesis in rodent brains. However, the underlying mechanism of LIF-dependent ACTH induction remains unclear. Recently, we found that LIF induces corticotropin-releasing hormone (CRH) in mouse trophoblast stem cells. This finding supports the results of a previous study that CRH, which is produced by the placenta, induces placental ACTH production. In this study, we examined whether the effects of LIF are mediated by the induction of Pomc via CRH upregulation in mouse trophoblast. In vivo, protein levels of LIF and CRH peak in mouse placenta at 13.5 days post coitum. In mouse placenta, Crh mRNA and protein levels significantly increased 3 h after intraperitoneal injection of LIF (5 μg/kg body weight) into dams at 13.5 days post coitum. We also examined the effect of LIF-induced CRH on the expression of Pomc induced by LIF in mouse trophoblast stem cells in vitro. After LIF supplementation for 3 days, we found that the increased expression of Crh-induced by new supplementation of LIF was earlier than that of Pomc. Furthermore, LIF-induced upregulation of Pomc in mouse trophoblast stem cells was attenuated by inhibition of the CRH/CRHR1 pathway, whereas LIF-induced secretion of ACTH was attenuated by inhibition of the JAK/STAT3 pathway. Therefore, LIF indirectly increases placental Pomc expression through the CRH/CRHR1 pathway, and placental ACTH secretion is induced directly by LIF via the JAK/STAT3 pathway.

Placental neurotrophin levels in gestational diabetes mellitus

OBJECTIVE

Neurotrophins are known to influence the development and maturation of the feto-placental unit and affect fetal growth trajectories. This study reports the levels of nerve growth factor (NGF) and brain-derived growth factor (BDNF) in the placenta of women with gestational diabetes mellitus (GDM).

METHODS

A total number of 60 women with GDM and 70 women without GDM (non-GDM) were included in the study. Placental NGF and BDNF levels were measured using commercially available ELISA kits.

RESULTS

Placental NGF levels were lower (p < .05) in women with GDM compared to non-GDM women. Maternal body mass index (BMI), mode of delivery, and the gender of the baby influenced the placental NGF levels. Placental BDNF levels were similar in GDM and non-GDM women. There was an influence of baby gender on the placental BDNF levels while maternal BMI and mode of delivery did not show any effect. In regression models adjusted for maternal age at delivery, gestational age, maternal BMI, mode of delivery, and baby gender, the placental NGF levels in the GDM group were lower (-0.144 pg/ml [95% CI -0.273, 22120.016] p = .028) as compared to the non-GDM group. However, there was no difference in the BDNF levels between the groups.

CONCLUSION

This study for the first time demonstrates differential effects on neurotrophic factors such as BDNF and NGF in the placenta in pregnancies complicated by GDM. Alterations in the levels of placental neurotrophins in GDM deliveries may affect placental development and fetal brain growth. This has implications for increased risk for neurodevelopmental pathologies in later life.

Decidual cells are the initial target of polyriboinosinic-polyribocytidylic acid in a mouse model of maternal viral infection

Background

Maternal immune activation has been implicated in the pathophysiology of neurodevelopmental disorders such as autism spectrum disorders caused by maternal infection. It has been suggested that the placental origin of inflammatory cytokines leads to neurodevelopmental disorders. However, the identity of the initial immune-activated site in the placenta, in response to maternal viral infection, is not clear.

Methods

By cross-breeding male enhanced green fluorescent protein (EGFP) transgenic mice with wild-type females, the placental tissues of maternal origin can be distinguished from those of paternal origin by EGFP expression. Using this method, at embryonic day (E) 12.5, dams were administered an intraperitoneal polyriboinosinic-polyribocytidylic acid (poly [I:C]) injection. We quantitatively analyzed the levels of phosphorylated interferon (IFN) regulatory factor 3 (pIRF3) in the placenta, and investigated the distribution of pIRF3 positive cells.

Results

We show that maternally derived decidual cells are the initial target of maternal poly (I:C) through the toll-like receptor 3/TIR-domain-containing the adapter-inducing interferon-β signaling pathway. We also show that the expression of interferon-β was upregulated in the placenta after maternal injection with poly (I:C).

Conclusion

These results suggest that maternally derived decidual cells are the initial target of maternal poly (I:C) and that this innate immune response is likely associated with a state of maternal immune activation.

Exposure to Maternal Immune Activation Causes Congenital Unfolded Protein Response Defects and Increases the Susceptibility to Postnatal Inflammatory Stimulation in Offspring

Background

A number of childhood diseases have been identified, such as severe infection or autoinflammatory disease, in which immune overreaction against inflammation is a possible underlying mechanism. Previous reports have demonstrated that fetal cells exposed to maternal immune activation (MIA) induced by polyriboinosinic-polyribocytidylic acid [poly(I:C)] exhibited hypersensitivity to inflammation in vitro. However, the details of this mechanism remain unclear. Therefore, this study aimed to reveal the reaction to inflammation in offspring exposed to MIA in the prenatal period, as well as its molecular mechanism, using a viral infection mouse model.

Materials and Methods

Pregnant mice at 12.5, 14.5, and 16.5 days post coitum were injected intraperitoneally with poly(I:C) 20 mg/kg body weight (BW) or saline. Offspring aged 3-4 weeks received the second injection of 20 mg/kg BW or 4 mg/kg BW poly(I:C) or saline. Serum and tissues were collected at 2, 24, 48, and 72 h after the postnatal injection. The cytokine profile, histopathology of organs, and unfolded protein response (UPR) in offspring were examined.

Results

The serum levels of interleukin (IL)-6, IL-17, and interferon-γ were significantly higher in the MIA group, and acute liver necrosis was detected. Moreover, failure in UPR was observed in the MIA group compared with that in the control group.

Conclusion

Overall, MIA exposure in utero caused failure in UPR as well as immune overreaction to the second attack of inflammation in offspring. Our results suggested that prenatal exposure to MIA might contribute to the congenital inflammatory constitution after birth.

Maternal Immune Activation by Poly I:C as a preclinical Model for Neurodevelopmental Disorders: A focus on Autism and Schizophrenia

Maternal immune activation (MIA) in response to a viral infection during early and mid-gestation has been linked through various epidemiological studies to a higher risk for the child to develop autism or schizophrenia-related symptoms.. This has led to the establishment of the pathogen-free poly I:C-induced MIA animal model for neurodevelopmental disorders, which shows relatively high construct and face validity. Depending on the experimental variables, particularly the timing of poly I:C administration, different behavioural and molecular phenotypes have been described that relate to specific symptoms of neurodevelopmental disorders such as autism spectrum disorder and/or schizophrenia. We here review and summarize epidemiological evidence for the effects of maternal infection and immune activation, as well as major findings in different poly I:C MIA models with a focus on poly I:C exposure timing, behavioural and molecular changes in the offspring, and characteristics of the model that relate it to autism spectrum disorder and schizophrenia.

Environmental influences on placental programming and offspring outcomes following maternal immune activation

Adverse experiences during pregnancy induce placental programming, affecting the fetus and its developmental trajectory. However, the influence of 'positive' maternal experiences on the placenta and fetus remain unclear. In animal models of early life stress, environmental enrichment (EE) has ameliorated and even prevented associated impairments in brain and behavior. Here, using a maternal immune activation (MIA) model in rats, we test whether EE attenuates maternal, placental and/or fetal responses to an inflammatory challenge, thereby offering a mechanism by which fetal programming may be prevented. Moreover, we evaluate life-long EE exposure on offspring development and examine a constellation of genes and epigenetic writers that may protect against MIA challenges. In our model, maternal plasma corticosterone and interleukin-1β were elevated 3 h after MIA, validating the maternal inflammatory response. Evidence for developmental programming was demonstrated by a simultaneous decrease in the placental enzymes Hsd11b2 and Hsd11b2/Hsd11b1, suggesting disturbances in glucocorticoid metabolism. Reductions of Hsd11b2 in response to challenge is thought to result in excess glucocorticoid exposure to the fetus and altered glucocorticoid receptor expression, increasing susceptibility to behavioral impairments later in life. The placental, but not maternal, glucocorticoid implications of MIA were attenuated by EE. There were also sustained changes in epigenetic writers in both placenta and fetal brain as a consequence of environmental experience and sex. Following MIA, both male and female juvenile animals were impaired in social discrimination ability. Life-long EE mitigated these impairments, in addition to the sex specific MIA associated disruptions in central Fkbp5 and Oprm1. These data provide the first evidence that EE protects placental functioning during stressor exposure, underscoring the importance of addressing maternal health and well-being throughout pregnancy. Future work must evaluate critical periods of EE use to determine if postnatal EE experience is necessary, or if prenatal exposure alone is sufficient to confer protection.