Augusto Frederico Schmidt

Purpose: To investigate the mechanisms by which plasma extracellular vesicles (EVs) from preterm infants with bronchopulmonary dysplasia (BPD) elicit inflammation and abnormal angiogenesis in neonatal mouse retinas. Methods: EVs from the plasma of 7-day-old preterm infants, born between 23^0/7 and 29^6/7 weeks of gestation, with BPD or without BPD (nBPD) at 36 weeks postmenstrual ages, were adoptively transferred into postnatal day 3 (P3) mice via intravenous retro-orbital sinus injection. Inflammation and pathological neovascularization in neonatal mouse retinas were examined by immunohistochemistry of retinal flat mounts for Allograft Inflammatory Factor 1 (AIF1), CD206, or Glial Fibrillary Acidic Protein (GFAP) and isolectin-B4 (IB4) staining on P17. Retinal inflammation-related transcripts were assessed by qRT-PCR. Proteomic profiles of BPD and nBPD EVs were examined by Liquid Chromatograph Mass Spectrometer/Mass Spectrometer (LC-MS/MS) and Gene Set Enrichment Analysis (GSEA). Results: Adoptively transferred EVs from BPD and nBPD infants crossed the blood–retinal barrier (BRB) in recipient mouse pups. BPD-EVs increased retinal activated microglia, Müller cells, and twisted proliferative neovascularization compared to nBPD-EVs. BPD-EVs also elevated retinal transcripts regulating inflammation and angiogenesis, including NOD-, LRR- and pyrin domain-containing protein 3 (Nlrp3), Apoptosis-associated speck-like protein containing a caspase recruitment domain (Asc), Caspase 3 (Casp3), Caspase 8 (Casp8), Gasdermin D (Gsdmd), Il1β, Il6, Aif1, and Vascular endothelial growth factor (Vegf). Proteomics analysis revealed that BPD-EVs had significantly elevated levels of inflammation and angiogenesis-related proteins compared to nBPD-EVs. Conclusions: BPD-EVs promote inflammation and abnormal neovascularization by upregulating genes related to apoptosis and inflammation in neonatal mouse retinas. EV protein profiles suggest that elevated levels of proteins such as Defensin alpha 1B (DEFA1B), Insulin-like growth factor binding protein 2 (IGFBP2), CD5 antigen-like (CD5L), von Willebrand factor (vWF), and Tenascin C (TNC) in BPD-EVs may contribute to the observed inflammation and angiogenesis.

There is a fundamental knowledge gap regarding the effects of neonatal hyperoxia exposure on the systemic vasculature and its repercussions on the cardiopulmonary system. Neonatal hyperoxia exposure induces a pro-inflammatory profile. However, the role of inflammation in the developing vascular tree and cardiopulmonary system is poorly understood. Caspase-1 mediates activation of inflammatory cytokines (IL-1β and IL-18) and gasdermin D (GSDMD), causing pyroptosis and inflammation. We hypothesized that caspase-1 is a critical contributor in neonatal hyperoxia-induced systemic vascular and cardiopulmonary inflammation and that caspase-1 inhibition attenuates hyperoxia-induced vascular stiffness, cardiopulmonary inflammation, and bronchopulmonary dysplasia (BPD) phenotype in a neonatal rat model. Newborn rats randomized to room air (RA) or hyperoxia (85% O2) from postnatal day (P) 1 to 14 received caspase-1 inhibitor, VX-765, or placebo. Hyperoxia-exposed pups had increased cardiovascular inflammation and fibrosis, aortic stiffness, pulmonary vascular rarefaction and remodeling, alveolar simplification, and right ventricular hypertrophy. Administration of a caspase-1 inhibitor decreased IL-1β and GSDMD gene and protein expression in the aorta and left ventricle. This was accompanied by reduced aortic stiffness and cardiac fibrosis, improved alveolar structure, pulmonary vascular density and vascular remodeling, and attenuation of right ventricular hypertrophy. Together, our findings suggest that inhibition of the caspase-1 pathway leads to decreased cardiopulmonary inflammation and remodeling. In conclusion, targeting caspase-1 signaling may be a therapeutic strategy to prevent the consequences of vascular and cardiopulmonary inflammation associated with preterm birth and oxygen therapy.

Extremely premature infants are at significant risk for developing bronchopulmonary dysplasia (BPD) and neurodevelopmental impairment (NDI). Although BPD is a predictor of poor neurodevelopmental outcomes, it is currently unknown how BPD contributes to brain injury and long-term NDI in pre-term infants. Extracellular vesicles (EVs) are small, membrane-bound structures released from cells into the surrounding environment. EVs are involved in inter-organ communication in diverse pathological processes. Inflammasomes are large, multiprotein complexes that are part of the innate immune system and are responsible for triggering inflammatory responses and cell death. Apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) is pivotal in inflammasome assembly and activating inflammatory caspase-1. Activated caspase-1 cleaves gasdermin D (GSDMD) to release a 30 kD N-terminal domain that can form membrane pores, leading to lytic cell death, also known as pyroptosis. Activated caspase-1 can also cleave pro-IL-1β and pro-IL-18 to their active forms, which can be rapidly released through the GSDMD pores to induce inflammation. Recent evidence has emerged that activation of inflammasomes is associated with neonatal lung and brain injury, and inhibition of inflammasomes reduces hyperoxia-induced neonatal lung and brain injury. Additionally, multiple studies have demonstrated that hyperoxia stimulates the release of lung-derived EVs that contain inflammasome cargos. Adoptive transfer of these EVs into the circulation of normal neonatal mice and rats induces brain inflammatory injury. This review focuses on EV–inflammasomes’ roles in mediating lung-to-brain crosstalk via EV-dependent and EV-independent mechanisms critical in BPD, brain injury, and NDI pathogenesis. EV–inflammasomes will be discussed as potential therapeutic targets for neonatal lung and brain injury.

Extremely premature infants are at significant risk for developing bronchopulmonary dysplasia (BPD) and neurodevelopmental impairment (NDI). Although BPD is a predictor of poor neurodevelopmental outcomes, it is currently unknown how BPD contributes to brain injury and long-term NDI in preterm infants. Extracellular vesicles (EVs) are small, membrane-bound structures released from cells into the surrounding environment. EVs are involved in inter-organ communication in diverse pathological processes. Inflammasomes are large, multiprotein complexes that are part of the innate immune system and are responsible for triggering inflammatory responses and cell death. Apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) is pivotal in inflammasome assembly and activating inflammatory caspase-1. Activated caspase-1 cleaves gasdermin D (GSDMD) to release a 30 kD N-terminal domain that can form membrane pores, leading to lytic cell death, also known as proptosis. Activated caspase-1 can also cleave pro-IL-1and pro-IL-18 to their active forms, which can be rapidly released through the GSDMD pores to induce inflammation. Recent evidence has emerged that activation of inflammasomes is associated with neonatal lung and brain injury, and inhibition of inflammasomes reduces hyperoxia-induced neonatal lung and brain injury. Additionally, multiple studies have demonstrated that hyperoxia stimulates the release of lung-derived EVs that contain inflammasome cargos. Adoptive transfer of these EVs into the circulation of normal neonatal mice and rats induces brain inflammatory injury. This review focuses on EV-inflammasomes’ roles in mediating lung-to-brain crosstalk via EV-dependent and EV-independent mechanisms critical in BPD, brain injury, and NDI pathogenesis. EV-inflammasomes will be discussed as potential therapeutic targets for neonatal lung and brain injury.

Background: Preterm birth is often associated with chorioamnionitis and leads to increased risk of neurodevelopmental disorders, such as autism. Preterm birth can lead to cerebellar underdevelopment, but the mechanisms of disrupted cerebellar development in preterm infants are not well understood. The cerebellum is consistently affected in people with autism spectrum disorders, showing reduction of Purkinje cells, decreased cerebellar grey matter, and altered connectivity.Methods: Preterm rhesus macaque fetuses were exposed to intra-amniotic LPS (1 mg,E. coliO55:B5) at 127 days (80%) gestation and delivered by c-section 5 days after injections. Maternal and fetal plasma were sampled for cytokine measurements. Chorio-decidua was analyzed for immune cell populations by flow cytometry. Fetal cerebellum was sampled for histology and molecular analysis by single-nuclei RNA-sequencing (snRNA-seq) on a 10× chromium platform. snRNA-seq data were analyzed for differences in cell populations, cell-type specific gene expression, and inferred cellular communications.Results: We leveraged snRNA-seq of the cerebellum in a clinically relevant rhesus macaque model of chorioamnionitis and preterm birth, to show that chorioamnionitis leads to Purkinje cell loss and disrupted maturation of granule cells and oligodendrocytes in the fetal cerebellum at late gestation. Purkinje cell loss is accompanied by decreased sonic hedgehog signaling from Purkinje cells to granule cells, which show an accelerated maturation, and to oligodendrocytes, which show accelerated maturation from pre-oligodendrocytes into myelinating oligodendrocytes.Conclusion: These findings suggest a role of chorioamnionitis on disrupted cerebellar maturation associated with preterm birth and on the pathogenesis of neurodevelopmental disorders among preterm infants.

Vertical transmission of SARS-CoV-2 from mother to fetus is widely accepted. Whereas most infected neonates present with mild symptoms or are asymptomatic, respiratory distress syndrome (RDS) and abnormal lung images are significantly more frequent in COVID-19 positive neonates than in non-infected newborns. Fatality is rare and discordant meta-analyses of case reports and series relating perinatal maternal COVID-19 status to neonatal disease severity complicate their extrapolation as prognostic indicators. A larger database of detailed case reports from more extreme cases will be required to establish therapeutic guidelines and allow informed decision making. Here we report an unusual case of a 28 weeks' gestation infant with perinatally acquired SARS-CoV-2, who developed severe protracted respiratory failure. Despite intensive care from birth with first line anti-viral and anti-inflammatory therapy, respiratory failure persisted, and death ensued at 5 months. Lung histopathology showed severe diffuse bronchopneumonia, and heart and lung immunohistochemistry confirmed macrophage infiltration, platelet activation and neutrophil extracellular trap formation consistent with late multisystem inflammation. To our knowledge, this is the first report of SARS CoV-2 pulmonary hyperinflammation in a preterm newborn with fatal outcome.

Accurate estimate of fetal maturity could provide individualized guidance for delivery of complicated pregnancies. However, current methods are invasive, have low accuracy, and are limited to fetal lung maturation. To identify diagnostic gestational biomarkers, we performed transcriptomic profiling of lung and brain, as well as cell-free RNA from amniotic fluid of preterm and term rhesus macaque fetuses. These data identify potentially new and prior-associated gestational age differences in distinct lung and neuronal cell populations when compared with existing single-cell and bulk RNA-Seq data. Comparative analyses found hundreds of genes coincidently induced in lung and amniotic fluid, along with dozens in brain and amniotic fluid. These data enable creation of computational models that accurately predict lung compliance from amniotic fluid and lung transcriptome of preterm fetuses treated with antenatal corticosteroids. Importantly, antenatal steroids induced off-target gene expression changes in the brain, impinging upon synaptic transmission and neuronal and glial maturation, as this could have long-term consequences on brain development. Cell-free RNA in amniotic fluid may provide a substrate of global fetal maturation markers for personalized management of at-risk pregnancies.

Preterm birth is often associated with chorioamnionitis and increased risk of neurodevelopmental disorders. Preterm birth also leads to cerebellar underdevelopment but the mechanisms of disrupted cerebellar development in preterm infants are little understood. Here, we leveraged single-nuclei RNA-sequencing of the cerebellum in a rhesus macaque model of chorioamnionitis and preterm birth, to show that chorioamnionitis leads to Purkinje cell loss and disrupted maturation of granule cells and oligodendrocytes in the fetal cerebellum at late gestation. Purkinje cell loss is accompanied by decreased sonic hedgehog signaling from Purkinje cells to granule cells, which show an accelerated maturation. Chorioamnionitis also accelerated pre-oligodendrocyte maturation into myelinating oligodendrocytes, confirmed by increased expression of myelin basic protein in the cerebellum of chorioamnionitis-exposed fetuses. These findings are consistent with reported histopathological findings in individuals with autism and suggest a novel mechanism through which perinatal inflammation contributes to neurodevelopmental disorders.

Background: Mechanical ventilation of preterm newborns causes lung injury and is associated with poor neurodevelopmental outcomes. However, the mechanistic links between ventilation-induced lung injury (VILI) and brain injury is not well defined. Since circulating extracellular vesicles (EVs) are known to link distant organs by transferring their cargos, we hypothesized that EVs mediate inflammatory brain injury associated with VILI. Methods: Neonatal rats were mechanically ventilated with low (10 mL/kg) or high (25 mL/kg) tidal volume for 1 h on post-natal day 7 followed by recovery for 2 weeks. Exosomes were isolated from the plasma of these rats and adoptively transferred into normal newborn rats. We assessed the effect of mechanical ventilation or exosome transfer on brain inflammation and activation of the pyroptosis pathway by western blot and histology. Results: Injurious mechanical ventilation induced similar markers of inflammation and pyroptosis, such as increased IL-1β and activated caspase-1/gasdermin D (GSDMD) in both lung and brain, in addition to inducing microglial activation and cell death in the brain. Isolated EVs were enriched for the exosomal markers CD9 and CD81, suggesting enrichment for exosomes. EVs isolated from neonatal rats with VILI had increased caspase-1 but not GSDMD. Adoptive transfer of these EVs led to neuroinflammation with microglial activation and activation of caspase-1 and GSDMD in the brain similar to that observed in neonatal rats that were mechanically ventilated. Conclusions: These findings suggest that circulating EVs can contribute to the brain injury and poor neurodevelopmental outcomes in preterm infants with VILI through activation of GSDMD.

Summary: Accurate estimate of fetal maturity could provide individualized guidance for delivery of complicated pregnancies. However, current methods are invasive, have low accuracy, and are limited to fetal lung maturation. To identify diagnostic gestational biomarkers, we performed transcriptomic profiling of lung and brain, as well as cell-free RNA from amniotic fluid of preterm and term rhesus macaque fetuses. These data predict new and prior associated gestational age differences in distinct lung and neuronal cell populations when compared to existing single-cell and bulk RNA-Seq data. Comparative analyses found over 200 genes coincidently induced in lung and amniotic fluid, and dozens in brain and amniotic fluid. This data enabled creation of computational models that accurately predicted lung compliance from amniotic fluid and lung transcriptome of preterm fetuses treated with antenatal corticosteroids. Cell-free RNA in amniotic fluid may provide a substrate of global fetal maturation markers for personalized management of at-risk pregnancies.