Detection of hypoxia markers in the cerebellum after a traumatic frontal cortex injury: a human postmortem gene expression analysis

Abstract

Purpose: The response to traumatic brain injury (TBI) is complex and induces various biological pathways in all brain regions that contribute to bad outcomes. The cerebellar hypoxia after a frontal cortex injury may potentiate the pathophysiological impacts of TBI. Therefore, a gene expression analysis was conducted to determine the influence of hypoxia on TBIs. Material and methods: Total RNA, including microRNAs, was isolated from the cerebellum of individuals who had died from severe frontal cortex injuries or due to natural causes of death (reference group). Results: From a total of 19,596 genes, an average of 59.56 % messenger RNAs (mRNAs) appeared expressed with 42 of them showing significant >2-fold differences of upregulated (n = 18) and downregulated (n = 24) genes. The validity of 14 candidate genes (with low p values and high fold differences or based on cited literature) was confirmed using qRT-PCR (Spearman correlation r2 = 0.93). Only four genes appeared to be either upregulated (FOSB and IL6) or downregulated (HSD11B1 and HSPA12B). From a total of 667 microRNAs, altogether, 248 microRNAs appeared expressed with 13 of them showing significant differences in the mean gene expression. The combination of two mRNAs (HSPA12B/FOSB or IL6/HSD11B1) or two microRNAs (either miR-138/miR-744 or miR-195/miR-324-5p) completely discriminated both groups, a finding unaltered by potential confounders such as age at biosampling, survival time, and the postmortem interval. Conclusions: Cerebellar hypoxia markers are important to understand the pathophysiology of TBIs and could be used for therapeutic strategies or forensic purposes, e.g., to assess the severity of a brain injury.