C-section and systemic inflammation synergize to disrupt the neonatal gut microbiota and brain development in a model of prematurity

Infants born very preterm (below 28 weeks of gestation) are at high risk of developing neurodevelopmental disorders, such as intellectual deficiency, autism spectrum disorders, and attention deficit. Preterm birth often occurs in the context of perinatal systemic inflammation due to chorioamnionitis and postnatal sepsis (Dammann, O. and Leviton, A., Intermittent or sustained systemic inflammation and the preterm brain. Pediatr Res, 2014. 75(3): p. 376-80). In addition, C-section is often performed for very preterm neonates to avoid hypoxia during a vaginal delivery (Luca, A.,et al., Birth trauma in preterm spontaneous vaginal and cesarean section deliveries: A 10-years retrospective study. PloS one,2022, 17(10), e0275726.) We have developed and characterized a mouse model based on intraperitoneal injections of IL-1b; between postnatal days one and five to reproduce perinatal systemic inflammation (Favrais, G.,et al., Systemic inflammation disrupts the developmental program of white matter. Ann Neurol,2011. 70(4): p. 550-65). This model replicates several neuropathological, brain imaging, and behavioral deficits observed in preterm infants. We hypothesized that C-sections could synergize with systemic inflammation to induce more severe brain abnormalities. We observed that C-sections significantly exacerbated the deleterious effects of IL-1b; on reduced gut microbial diversity, increased levels of circulating peptidoglycans, abnormal microglia/macrophage reactivity, impaired myelination, and reduced functional connectivity in the brain relative to vaginal delivery plus intraperitoneal saline. These data demonstrate the deleterious synergistic effects of C-section and neonatal systemic inflammation on brain maldevelopment and malfunction, two conditions frequently observed in very preterm infants, who are at high risk of developing neurodevelopmental disorders. ### Competing Interest Statement The authors have declared no competing interest.