(157t) How Is Hydrocephalus Treatment Dependent on Astrocyte Phenotype Expression?

Current understanding of the cellular response contributing to the failure of hydrocephalus cerebral spinal fluid (CSF) shunts has been limited, to date, with the evaluation of cells and tissue around the implant. Yet there is a critical knowledge gap in gene expression profiles in this tissue. When paired with cellular analysis, gene expression can lead to an understanding of the activity of the cells obstructing catheters at the time of shunt failure. This study represents the first robust investigation of the changes in gene expression levels specific to astrocyte immune response following CSF shunt implantation. From our NIH R01-funded work, we know that the tissue occluding shunts is over 80% inflammatory cells, with a more exaggerated astrocytic response when the analyzed tissue/shunt comes from a patient whose shunt was removed for obstruction. To understand how to mitigate the cell immune response to shunts, and therefore reduce mechanisms leading to shunt failure, we will perform gene expression profiling over collected CSF shunts from patients to observe whether the cells on the shunt surface are expressing two significantly different reactive astrocytes phenotype; A1 or A2. An invaluable marker to distinguish between different activation states of reactive astrocytes, is the A1 complement component C3 gene. C3 is specifically one of the most characteristic and highly upregulated genes in A1 and is not expressed by resting or A2 reactive astrocytes. To identify whether there are C3-expressing A1 astrocytes in tissues from CSF shunt regions, astrocytes that are C3-positive by fluorescence in situ hybridization (FISH) are analyzed. Then, quantitative PCR (qPCR) analysis is used to confirm upregulation of C3 in the tissue samples. We will correlate these data to ELISA characterized CSF collected from the same patients for pro-inflammatory cytokines. Therefore, we begin to shed light on astrocyte phenotype expression on shunt surfaces and root causes for implant failure. In the brain, TNFα, IL-1α and C1q combined propel resting astrocytes into a full-fledged A1 state. This study will drive investigation into whether astrocytes occluding shunts could be prevented by simply blocking secretion or action of these three cytokines to keep astrocytes out of the A1 state. FDA-approved drugs targeting TNFα and Il-1α already exist and are in use for other medical conditions.