Neutrophils and Monocytes in Pediatric Ischemic Stroke

PROJECT SUMMARY (Description) Ischemic stroke affects around 1 in 1600 to 4000 births, has the highest incidence in neonates and infants (< one year of age), and may cause neurological sequalae, including motor and cognitive deficits. Infection and immune responses are a major risk factor for pediatric stroke, but no immune-directed therapies are available. In fact, supportive measures remain the mainstay of pediatric stroke care, since the lytic treatment carries a high in neonates with fragile cerebrovascular vessels. In this project, we will use a murine model of pediatric stroke, with and without lipopolysaccharides (LPS)-sensitization, to test the pathological roles of neutrophils and monocytes towards the development of immunomodulation therapies. Aim 1: To clarify how immune cells breach the pial/glia limitans barrier in pediatric LPS/stroke. We will use flow cytometry and single-cell RNA-Seq analysis to determine the compositions and transcriptome of immune cells in the meninges after LPS/stroke, and test whether anti-MMP9 treatment prevents the neutrophil influx. Aim 2: To test whether there are two waves of monocytic infiltrates with distinct functions in pediatric stroke. We will use CCR2-CreER mice to track monocytic infiltrates and single-cell RNA-Seq analysis, as well as, block the influx of monocytes at different stage after stroke to address this issue. Aim 3: To determine what constitutes the meninges-incurred pathogenicity of neutrophils after pediatric LPS/stroke. Our RNA-Seq results suggest that neutrophils acquire IL-36gamma, a novel family of the IL-1 family cytokine, in the meninges. We will validate these findings and test the benefits of anti-IL36R treatment. Successful completion of this project will shed insights into the mechanisms of pediatric ischemic stroke and whether neutrophil/monocyte-targeted immunomodulation therapies could provide better clinical management.