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.