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 r(2) = 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.

Fig. 1

Expression of 14 differentially expressed genes (ARPC5, BCAT, CASP3, FOSB, GFAP, GADD45B, GRIA3, HSD11B1, HSPA12B, IL6, NTRK2, PRPH, RGS6, and S100B) in the cerebellum following a frontal cortex injury. bar refer to the mean values and error bar indicate the standard deviation of gene expression. Data are represented as fold change in gene expression relative to the controls