miR-146b Protects the Perinatal Brain against Microglia-Induced Hypomyelination.

OBJECTIVES: In the premature newborn, perinatal inflammation mediated by microglia contributes significantly to neurodevelopmental injuries including white matter injury (WMI). Brain inflammation alters development through neuroinflammatory processes mediated by activation of homeostatic microglia toward a pro-inflammatory and neurotoxic phenotype. Investigating immune regulators of microglial activation is crucial to find effective strategies to prevent and treat WMI. METHODS: Ex vivo microglial cultures and a mouse model of WMI induced by perinatal inflammation (interleukin-1-beta [IL-1ß] and postnatal days 1-5) were used to uncover and elucidate the role of microRNA-146b-5p in microglial activation and WMI. RESULTS: A specific reduction in vivo in microglia of Dicer, a protein required for microRNAs maturation, reduces pro-inflammatory activation of microglia and prevents hypomyelination in our model of WMI. Microglial miRNome analysis in the WMI model identified miRNA-146b-5p as a candidate modulator of microglial activation. Ex vivo microglial cell culture treated with the pro-inflammatory stimulus lipopolysaccharide (LPS) led to overexpression of immunomodulatory miRNA-146b-5p but its drastic reduction in the microglial extracellular vesicles (EVs). To increase miRNA-146b-5p expression, we used a 3DNA nanocarrier to deliver synthetic miRNA-146b-5p specifically to microglia. Enhancing microglial miRNA-146b-5p overexpression significantly decreased LPS-induced activation, downregulated IRAK1, and restored miRNA-146b-5p levels in EVs. In our WMI model, 3DNA miRNA-146b-5p treatment significantly prevented microglial activation, hypomyelination, and cognitive defect induced by perinatal inflammation. INTERPRETATIONS: These findings support that miRNA-146b-5p is a major regulator of microglia phenotype and could be targeted to reduce the incidence and the severity of perinatal brain injuries and their long-term consequences. ANN NEUROL 2022;91:48-65.

Cytomegalovirus (CMV) Shedding in French Day-Care Centers: A Nationwide Study of Epidemiology, Risk Factors, Centers' Practices, and Parents' Awareness of CMV.

BACKGROUND: Congenital cytomegalovirus (CMV) remains an important healthcare burden, resulting from primary or secondary infection in pregnant women. Exposure to young children's saliva is a major risk factor, as prevalence of CMV shedding can reach 34%. METHODS: This cross-sectional, multicenter, nationwide study was conducted in randomly selected day care centers (DCCs), and complemented with a survey among parents and DCCs. All children aged >3 months were eligible. The study measured the CMV shedding prevalence in children's saliva and described CMV genotypes epidemiology. The risk factors for CMV shedding and high viral load were evaluated using multivariable models. RESULTS: A total of 93 DCCs participated. Among the 1770 enrolled children with evaluable samples, the CMV shedding prevalence was 40% (713/1770, 95% confidence interval, 34.6-46.1), independently associated with children aged between 12 and 18 months, history of CMV infection in ≥1 parents, a mid-level income. Prevalence increased with DCC staff workload and attending children number. Viral load was ≥5 log-copies CMV/mL in 48% (342/713). Risk factors for higher viral load included children aged between 12 and 18 months, and still being breastfed. The most frequent genotype combinations were gB1-gN4c-gH2 (6.9%), gB1-gN2-gH2 (6.3%), gB4a-gN3a-gH1 (6.3%), and gB1-gN3b-gH2 (5,7%). CMV awareness was low in parents: their serological status was unknown by 72% of mothers and 82% of fathers. Only 41% knew something about CMV. CONCLUSIONS: CMV shedding was independently associated with risk factors related to the children, family and DCC. Some of these risk factors may influence prevention strategies, including through an improved information provided to parents. CLINICAL TRIALS REGISTRATION: NCT01704222.

Decreased microglial Wnt/ß-catenin signalling drives microglial pro-inflammatory activation in the developing brain.

Microglia of the developing brain have unique functional properties but how their activation states are regulated is poorly understood. Inflammatory activation of microglia in the still-developing brain of preterm-born infants is associated with permanent neurological sequelae in 9 million infants every year. Investigating the regulators of microglial activation in the developing brain across models of neuroinflammation-mediated injury (mouse, zebrafish) and primary human and mouse microglia we found using analysis of genes and proteins that a reduction in Wnt/ß-catenin signalling is necessary and sufficient to drive a microglial phenotype causing hypomyelination. We validated in a cohort of preterm-born infants that genomic variation in the Wnt pathway is associated with the levels of connectivity found in their brains. Using a Wnt agonist delivered by a blood-brain barrier penetrant microglia-specific targeting nanocarrier we prevented in our animal model the pro-inflammatory microglial activation, white matter injury and behavioural deficits. Collectively, these data validate that the Wnt pathway regulates microglial activation, is critical in the evolution of an important form of human brain injury and is a viable therapeutic target.

Short- and long-term respiratory outcomes in neonates with ventilator-associated pneumonia.

BACKGROUND AND OBJECTIVE: Ventilator-associated pneumonia (VAP) is a common nosocomial infection in critical care settings and might have important long-term consequences in neonates. Our aim is to clarify the short- and long-term respiratory outcomes of neonates affected by VAP. METHODS: Prospective, population-based, cohort study with 12 months follow-up based on clinical examinations and diary-based respiratory morbidity score, conducted in an academic tertiary referral neonatal unit with dedicated follow-up program. RESULTS: A total of 199 inborn neonates consecutively ventilated for at least 48 hours were eligible for the study. One hundred fifty-one were finally enrolled and classified as "exposed" or "unexposed" to VAP, if they fulfilled (or not) VAP criteria once during their stay. Bronchopulmonary dysplasia (BPD) incidence was significantly higher in exposed (75%) than in unexposed babies (26.8%; relative risk [RR]: 2.8 [1.9-4.0]; Adj RR: 3.5 [1.002-12.7]; P = .049; number needed to harm = 2.07), although the composite BPD/mortality did not differ. Exposed patients showed longer intensive care unit stay (87 [43-116] vs 14 [8-52] days; St.ß = 0.24; P < .0001) and duration of ventilation (15 [10-25] vs 5 [4-8] days; St.ß = 0.29; P < .0001) than unexposed neonates. Exposed patients also showed less ventilator-free days (11 [5-17.7] vs 22 [14-24] days; St.ß = -0.15; P = .05) compared to unexposed. Respiratory infections, use of drugs, rehospitalization for respiratory reasons, home oxygen therapy, their composite outcome, and diary-based clinical respiratory morbidity score were similar between the cohorts. CONCLUSION: Neonatal VAP seems associated to higher incidence of BPD, longer ventilation, and intensive care stay but it does not affect long-term respiratory morbidity.