Fetal brain vulnerability to SARS-CoV-2 infection

Perinatal Hypoxia and Immune System Activation in Schizophrenia Pathogenesis: Critical Considerations During COVID-19 Pandemic

Schizophrenia, a severe psychiatric, neurodevelopmental disorder affecting about 0.29-1 % of the global population, is characterized by hallucinations, delusions, cognitive impairments, disorganized thoughts and speech, leading to significant social withdrawal and emotional blunting. During the 1980s, considerations about diseases that result from complex interactions of genetic background and environmental factors started to appear. One of the critical times of vulnerability is the perinatal period. Concerning schizophrenia, obstetric complications that are associated with hypoxia of the fetus or neonate were identified as a risk. Also, maternal infections during pregnancy were linked to schizophrenia by epidemiological, serologic and genetic studies. Research efforts then led to the development of experimental models testing the impact of perinatal hypoxia or maternal immune activation on neurodevelopmental disorders. These perinatal factors are usually studied separately, but given that the models are now validated, it is feasible to investigate both factors together. Inclusion of additional factors, such as metabolic disturbances or chronic stress, may need to be considered also. Understanding the interplay of perinatal factors in schizophrenia's etiology is crucial for developing targeted prevention and therapeutic strategies.

KANET evaluation in patients with SARS-CoV-2

OBJECTIVES

To determine a possible correlation between SARS-CoV-2 infection during pregnancy and altered fetal behavior.

METHODS

Kurjak's antenatal neurodevelopmental test (KANET) was applied from 28 to 40 weeks in 38 gestations (group A) diagnosed with COVID-19 infection during the first week and 43 non-COVID pregnant women (group B).

RESULTS

No statistically significant differences considering maternal age (33±3.9 years for group A vs. 31±4.1 years for group B) and gestational age (33±1.6 weeks for group A compared to 33±2.1 weeks for group B) were observed. KANET scores were not different between the two groups.

CONCLUSIONS

Fetal behavior differences are not altered in women diagnosed with SARS-CoV-2 infection during the third trimester of pregnancy.

Prenatal SARS-CoV-2 infection results in neurodevelopmental and behavioral outcomes in mice

Prenatal exposure to viral pathogens has been known to cause the development of neuropsychiatric disorders in adulthood. Furthermore, COVID-19 has been associated with a variety of neurological manifestations, raising the question of whether in utero SARS-CoV-2 exposure can affect neurodevelopment, resulting in long-lasting behavioral and cognitive deficits. Using a human ACE2-knock-in mouse model, we have previously shown that prenatal exposure to SARS-CoV-2 at later stages of development leads to fetal brain infection and gliosis in the hippocampus and cortex. In this study, we aimed to determine whether infection of the fetal brain results in long-term neuroanatomical alterations of the cortex and hippocampus or in any cognitive deficits in adulthood. Here, we show that infected mice developed slower and weighed less in adulthood. We also found altered hippocampal and amygdala volume and aberrant newborn neuron morphology in the hippocampus of adult mice infected in utero. Furthermore, we observed sex-dependent alterations in anxiety-like behavior and locomotion, as well as hippocampal-dependent spatial memory. Taken together, our study reveals long-lasting neurological and cognitive changes as a result of prenatal SARS-CoV-2 infection, identifying a window for early intervention and highlighting the importance of immunization and antiviral intervention in pregnant women.

CCN1-Mediated Signaling in Placental Villous Tissues after SARS-CoV-2 Infection in Term Pregnant Women: Implications for Dysregulated Angiogenesis

The global spread of SARS-CoV-2 has increased infections among pregnant women. This study aimed to explore placental pathology alterations and angiogenic factor levels in term pregnant women after SARS-CoV-2 infection in a retrospective single-center study. Additionally, we investigated the role and underlying mechanism of the vascular inflammation-promoting, cysteine-rich protein 61 (CYR61/CCN1) in this context. All analyses were performed in term pregnant women infected with or without SARS-CoV-2. The sFlt-1, PlGF, and sEng serum levels were quantified using ELISA. Placental protein expressions were examined by immunoblot and immunostaining. Additionally, the effect of CCN1 protein on SGHPL-5 trophoblast cells was examined. We found that SARS-CoV-2 activated the inflammatory response in pregnant women, leading to pronounced vascular alterations in placental villous tissues. Elevated serum anti-angiogenic factors (sFlt-1, sEng) upon SARS-CoV-2 infection may directly contribute to these pathological changes. Upregulated CCN1 and pNF-κB in placental villous tissues of infected patients are identified as crucial factors in placental alterations. As a conclusion, CCN1 was significantly elevated in the placentas of term pregnant women infected with SARS-CoV-2. By activating a cascade of inflammatory responses, CCN1 induced the production of the anti-angiogenic factors sFlt-1 and sEng, which may lead to abnormal placental vascular architecture.

Role of microglia in brain development after viral infection

Microglia are immune cells in the brain that originate from the yolk sac and enter the developing brain before birth. They play critical roles in brain development by supporting neural precursor proliferation, synaptic pruning, and circuit formation. However, microglia are also vulnerable to environmental factors, such as infection and stress that may alter their phenotype and function. Viral infection activates microglia to produce inflammatory cytokines and anti-viral responses that protect the brain from damage. However, excessive or prolonged microglial activation impairs brain development and leads to long-term consequences such as autism spectrum disorder and schizophrenia spectrum disorder. Moreover, certain viruses may attack microglia and deploy them as "Trojan horses" to infiltrate the brain. In this brief review, we describe the function of microglia during brain development and examine their roles after infection through microglia-neural crosstalk. We also identify limitations for current studies and highlight future investigated questions.

Reactive Gliosis in Neonatal Disorders: Friend or Foe for Neuroregeneration?

A developing nervous system is particularly vulnerable to the influence of pathophysiological clues and injuries in the perinatal period. Astrocytes are among the first cells that react to insults against the nervous tissue, the presence of pathogens, misbalance of local tissue homeostasis, and a lack of oxygen and trophic support. Under this background, it remains uncertain if induced astrocyte activation, recognized as astrogliosis, is a friend or foe for progressing neonatal neurodevelopment. Likewise, the state of astrocyte reactivity is considered one of the key factors discriminating between either the initiation of endogenous reparative mechanisms compensating for aberrations in the structures and functions of nervous tissue or the triggering of neurodegeneration. The responses of activated cells are modulated by neighboring neural cells, which exhibit broad immunomodulatory and pro-regenerative properties by secreting a plethora of active compounds (including interleukins and chemokines, neurotrophins, reactive oxygen species, nitric oxide synthase and complement components), which are engaged in cell crosstalk in a paracrine manner. As the developing nervous system is extremely sensitive to the influence of signaling molecules, even subtle changes in the composition or concentration of the cellular secretome can have significant effects on the developing neonatal brain. Thus, modulating the activity of other types of cells and their interactions with overreactive astrocytes might be a promising strategy for controlling neonatal astrogliosis.