Altered expression of myelin-associated inhibitors and their receptors after traumatic brain injury in the mouse.

Abstract

When central nervous system axons are injured, regeneration is partly inhibited by myelin-associated inhibitors (MAIs). Following traumatic brain injury (TBI) in the rat, pharmacological neutralisation of the MAIs Nogo-A and myelin-associated glycoprotein (MAG) resulted in improved functional outcome. In contrast, genetic or pharmacological neutralization of the MAI receptors Nogo-66 receptor 1 (NgR1) or paired-immunoglobulin like receptor-B (PirB) showed an unaltered or impaired outcome following TBI in mice. The aim of the present study was thus to evaluate the MAI expression levels following TBI in mice. Quantitative reverse transcriptase PCR (qRT-PCR) was used to measure total RNA isolated from brains of young adult male C57BL/6 mice at one, three or seven days following controlled cortical impact TBI or sham injury. Hippocampal and neocortical tissue ipsi- and contralateral to the injury was analyzed for Nogo-A, oligodendrocyte-myelin glycoprotein (OMgp), MAG, and the MAI receptors PirB and NgR1, including its co-receptor Lingo1. Compared to sham-injured controls, PirB neocortical expression was significantly upregulated at one day and NgR1 expression downregulated at seven days post-TBI. In the hippocampus, transcriptional upregulation was observed in Nogo-A (one day post-injury), MAG and PirB at seven days post-injury. In contrast, the hippocampal transcripts of NgR1 and Lingo1 were decreased at seven days post-injury. The expression of OMgp was unaltered at all time points post-injury. These results suggest that early dynamic changes in MAI gene expression occur following TBI in the mouse, particularly in the hippocampus, which may play an inhibitory role for post-injury regeneration and plasticity.