Leveraging Choroid Plexus M-CSF Signaling to Prevent Inflammatory-Driven Hydrocephalus - PROJECT SUMMARY Pediatric hydrocephalus is a life-threatening condition denoted by excessive cerebrospinal fluid (CSF) accumulation in the brain's ventricles. The most common causes of pediatric hydrocephalus are a previous infection or intraventricular hemorrhage from prematurity, which have been proposed to be driven by neuroinflammation. Recent in vivo experiments in adult mice have established that inflammation contributes to the development of hydrocephalus, and preliminary data that I have generated demonstrate that inflammation in utero also causes hydrocephalus. Human pathological studies and rodent models have highlighted that intraventricular macrophages are necessary to clear infection and blood but also may cause off-target damage. The most abundant macrophages in the ventricle are the epiplexus cells on the apical side of the choroid plexus (ChP), the essential brain barrier that synthesizes and regulates CSF composition. However, the core function of these macrophages remains elusive. Following innate immune activation, a diverse population of macrophages accumulates at the ChP, likely with distinct roles to upregulate or downregulate inflammation and prepare for tissue repair. Recent data from the Lehtinen lab has highlighted that the ChP epithelial cells express an essential macrophage survival factor, macrophage colony-stimulating factor (M-CSF), during homeostasis and is upregulated during inflammation. Additionally, differential expression of the M-CSF receptor, CSF-1R, is detected in macrophage populations at the ChP following innate immune activation. Despite the critical importance of brain resident macrophages for proper brain development and the deep understanding of microglia, the core functions of macrophage populations in the ventricle during homeostasis and neuroinflammation are still poorly understood. Is the ChP a source of M-CSF to maintain epiplexus macrophage survival required for core ChP function? Does the ChP M-CSF signaling regulate specific macrophage populations following in utero neuroinflammation? I will address these questions with innovative approaches to manipulate gene expression at the ChP in vivo and characterize macrophages at the ChP with single-cell RNA sequencing, histology, and advanced imaging techniques. I will uncover how the ChP regulates macrophages through M-CSF signaling during homeostatic and inflammatory conditions. Ultimately, I will test whether these populations can be therapeutically targeted with M-CSF gene therapy at the ChP to prevent inflammation-induced hydrocephalus. The training plan developed around this research proposal takes full advantage of the expertise in the Lehtinen lab and the unprecedented resources at Boston Children's Hospital to fulfill my goal of studying the core CSF and ChP biology. Ultimately this fellowship will enable me to establish the foundation for my future research program as a tenure-track professor in neurological infectious disease and neuroinflammation.
