Prenatal opioid exposure and maternal HCV infection impair microglia development and function: A patient-specific in vitro model

Opioids are a class of pain-relieving drugs known to cross the placental and blood brain barriers, exposing the fetus in utero. Rates of opioid use disorder amongst pregnant individuals in the United States are on the rise, and intravenous routes of opioid administration are highly associated with hepatitis C (HCV) infection. Newborns with prenatal opioid exposure (POE) are more likely to be small for gestational age and have increased rates of neurodevelopmental delay. Microglia are brain-resident macrophages that originate from yolk-sac precursors that play critical role in neurodevelopment. However, our understanding of the impact of POE on microglia maturation and function remains limited due to the scarcity of adequate models. Here, we leveraged a model of induced microglia-like cells (iMGL) derived from umbilical cord blood mononuclear cells to uncover the mechanisms underlying the impact of POE ± maternal HCV infection on microglia morphology, phenotype, function, and transcriptional profiles. Our study revealed that iMGL are closely related to primary microglia. iMGL derived from pregnancies with POE and maternal HCV infection exhibited an ameboid-like phenotype, characterized by smaller area/perimeter and diminished ramifications. This was accompanied by dysregulated expression of key microglia markers, impaired phagocytic capacity, but increased secretion of inflammatory mediators. Finally, transcriptional analysis of iMGL with and without stimulation by LPS revealed that POE ± maternal HCV infection desensitized iMGL to LPS stimulation. This immune tolerance of iMGL in utero was reflected by altered expression of genes important for neurological and fetal development, phagocytosis, and antimicrobial responses with POE ± maternal HCV infection. Overall, these findings highlight the utility of iMGLs as an accessible patient-specific model to study preconditioning and development of fetal microglia and provide insight into mechanisms underlying adverse neurodevelopmental outcomes in newborns with POE in presence and absence of maternal HCV infection.