Poster #11 - Laura Davis

Proteomic Characterization of Porcine Brain Parenchyma in Acute and Sustained Models of Hydrocephalus

Davis, LM1; Haddad, S1; Curtin, K1; Fazelinia, H2,3; Roof, J2; Brown, EM2; Spruce, LA2; Kilbaugh, T1; Hwang, M1,4. Affiliations: 1 Radiology Department, Children's Hospital of Philadelphia, Philadelphia, Pennsylvania 2 Proteomics Core Facility, Children's Hospital of Philadelphia, Philadelphia, PA 19104 3 Department of Biomedical and Health Informatics, Children's Hospital of Philadelphia, Philadelphia, PA 19102 4 University of Pennsylvania, Philadelphia, Pennsylvania

Purpose: Hydrocephalus - the accumulation of cerebrospinal fluid (CSF) in the brain - leads to elevated intracranial pressure (ICP) and parenchymal injury. Non-invasive assessment (US, MRI) has limited sensitivity for this injury. We aimed to characterize parenchymal injury with proteomics to identify theranostic targets. Materials and Methods: Using a porcine model of hydrocephalus, intracranial pressure was elevated to between 20 mmHg and 60 mmHg for up to 2-24 hours. Ischemia was defined by lactate to pyruvate ratio. Mass-spectroscopic proteomic analysis of the parenchyma was performed. Pigs were grouped by ICP level (20, 50-60 mmHg) and duration of raised ICP (acute: < 4 hours, sustained: 8, 12, and 24 hours). Proteomic data were processed in R (log2 transformation, normalization, and Limma t-test to identify differentially abundant proteins (DAPs)) with over-representation analysis (ORA) and gene set enrichment analysis (GSEA). Results: A total of 19 brain tissue samples were included, with 7038 genes identified. Pathways of immune function were over-represented in ICP 20 mmHg group on ORA, including neutrophil degranulation, immunoglobulin-related immune response, tumor necrosis factor production, and NF-κB signal transduction in this group; in the sustained ICP group, GSEA showed enrichment of immune system process and leukocyte mediated immunity. Changes in metabolic pathways were seen in the ICP 20 mmHg group, with enrichment of cellular components including the mitochondrial ribosome, and the ICP 50-60mmHg group, where ORA showed enrichment of pathways including respiratory electron transport, and GSEA showed positive enrichment of oxidative phosphorylation and the respiratory electron transport chain. At sustained ICP levels, there was enrichment of coagulation-related pathways including thrombomodulin and fibrinogen, of pathways related to tissue injury, including wound healing, and alterations in enzymatic function, including peptidase regulator activity. Conclusions: Proteomic analysis of the hydrocephalic pig brain showed enrichment of immune pathways at lower ICP, enrichment in metabolic pathways with increasing intracranial pressure, and alterations in hemostasis, wound healing and enzyme activation and regulation with prolonged ICP elevation.