Abstract
Circulating microRNAs (miRNAs) have emerged as diagnostic and prognostic biomarkers for traumatic brain injury (TBI). However, a comprehensive characterization of the serum miRNA profile in patients with TBI and the roles of these potential markers in neuronal regulation have rarely been reported. In this study, the levels of 754 serum miRNAs were initially determined in two pooled samples of 15 severe traumatic brain injury (sTBI) patients and 15 healthy controls using a TaqMan Low Density Array. The markedly upregulated miRNAs in sTBI patients were subsequently validated individually by quantitative reverse-transcription PCR (RT-qPCR) in another larger cohort consisting of 81 sTBI patients, 81 mild traumatic brain injury (mTBI) patients and 82 age/sex-matched healthy controls. Seven miRNAs, including miR-103a-3p, miR-219a-5p, miR-302d-3p, miR-422a, miR-518f-3p, miR-520d-3p and miR-627, were significantly upregulated in both sTBI and mTBI patients compared with their expression in controls. Among these miRNAs, miR-219a-5p not only discriminated sTBI and mTBI patients from controls but also discriminated between sTBI and mTBI patients. We further show here that in the neuronal cell injury model, upregulated miR-219a-5p inhibits the expression of CCNA2 and CACUL1 and further regulates akt/Foxo3a and p53/Bcl-2 signaling pathways, causing a notable change in the expression of cleaved caspase-3, thereby inducing neuronal apoptosis. These results indicate that these seven selected miRNAs could serve as novel biomarkers for TBI. In particular, miR-219a-5p is a potentially valuable indicator of the diagnosis, prognosis of TBI and appears to regulate neuronal apoptosis and death.