Transcriptional Pathology Evolves Over Time in Rat Hippocampus Following Lateral Fluid Percussion Traumatic Brain Injury

Abstract

Traumatic brain injury (TBI) causes acute and lasting impacts on the brain, driving pathology along anatomical, cellular, and behavioral dimensions. Rodent models offer the opportunity to study TBI in a controlled setting, and enable analysis of the temporal progression that occurs from injury to recovery. We applied transcriptomic and epigenomic analysis, characterize gene expression and in ipsilateral hippocampus at 1 and 14 days following moderate lateral fluid percussion (LFP) injury. This approach enabled us to identify differential gene expression (DEG) modules with distinct expression trajectories across the two time points. The major DEG modules represented genes that were up- or downregulated acutely, but largely recovered by 14 days. As expected, DEG modules with acute upregulation were associated with cell death and astrocytosis. Interestingly, acutely downregulated DEGs related to neurotransmission mostly recovered by two weeks. Upregulated DEG modules related to inflammation were not necessarily elevated acutely, but were strongly upregulated after two weeks. We identified a smaller DEG module with delayed downregulation at 14 days including genes related to cholesterol metabolism and amyloid beta clearance. Finally, differential expression was paralleled by changes in H3K4me3 at the promoters of differentially expressed genes at one day following TBI. Following TBI, changes in cell viability, function and ultimately behavior are dynamic processes. Our results show how transcriptomics in the preclinical setting has the potential to identify biomarkers for injury severity and/or recovery, to identify potential therapeutic targets, and, in the future, to evaluate efficacy of an intervention beyond measures of cell death or spatial learning.