Plasma miR-9-3p and miR-136-3p as Potential Novel Diagnostic Biomarkers for Experimental and Human Mild Traumatic Brain Injury

Abstract

Noninvasive, affordable circulating biomarkers for difficult-to-diagnose mild traumatic brain injury (mTBI) are an unmet medical need. Although blood microRNA (miRNA) levels are reportedly altered after traumatic brain injury (TBI), their diagnostic potential for mTBI remains inconclusive. We hypothesized that acutely altered plasma miRNAs could serve as diagnostic biomarkers both in the lateral fluid percussion injury (FPI) model and clinical mTBI. We performed plasma small RNA-sequencing from adult male Sprague–Dawley rats (n = 31) at 2 days post-TBI, followed by polymerase chain reaction (PCR)-based validation of selected candidates. miR-9a-3p, miR-136-3p, and miR-434-3p were identified as the most promising candidates at 2 days after lateral FPI. Digital droplet PCR (ddPCR) revealed 4.2-, 2.8-, and 4.6-fold elevations in miR-9a-3p, miR-136-3p, and miR-434-3p levels (p < 0.01 for all), respectively, distinguishing rats with mTBI from naïve rats with 100% sensitivity and specificity. DdPCR further identified a subpopulation of mTBI patients with plasma miR-9-3p (n = 7/15) and miR-136-3p (n = 5/15) levels higher than one standard deviation above the control mean at <2 days postinjury. In sTBI patients, plasma miR-9-3p levels were 6.5- and 9.2-fold in comparison to the mTBI and control groups, respectively. Thus, plasma miR-9-3p and miR-136-3p were identified as promising biomarker candidates for mTBI requiring further evaluation in a larger patient population.

The miRNome of Depression

“…In this context, miRNAs found in blood and body fluids are currently gaining attention [ 88 ]. Circulating miRNAs appear to be good candidates in biomarker research due to their high level of stability in the blood [ 89 , 90 ] and the presence of brain-specific miRNA transcripts, such as miR-9, that can be detected in body fluids [ 91 ]. Indeed, numerous scientific reports have shown that brain-specific miRNAs can effectively cross the blood–brain barrier and are detectable in blood [ 85 , 86 , 87 , 88 , 89 , 90 , 91 , 92 ], as well as in brain-derived extracellular vesicles circulating in the bloodstream [ 93 ].…”

“…Circulating miRNAs appear to be good candidates in biomarker research due to their high level of stability in the blood [ 89 , 90 ] and the presence of brain-specific miRNA transcripts, such as miR-9, that can be detected in body fluids [ 91 ]. Indeed, numerous scientific reports have shown that brain-specific miRNAs can effectively cross the blood–brain barrier and are detectable in blood [ 85 , 86 , 87 , 88 , 89 , 90 , 91 , 92 ], as well as in brain-derived extracellular vesicles circulating in the bloodstream [ 93 ]. The ability of brain-specific miRNAs to pass through the blood–brain barrier makes them ideal biomarkers of brain processes, including mental illnesses such as depression.…”

Integrated Bioinformatics Analysis of Potential mRNA and miRNA Regulatory Networks in Mice With Ischemic Stroke Treated by Electroacupuncture

“…The miR-425-5p could possibly be useful in controlling the negative effects of ischemic stroke, as Lim reported (55). The mmu-miR-434-3p has been suggested to potentially increase neuronal regeneration under conditions of stress, especially in brain injury (56)(57)(58). The miR-453 was found to be a good outcome associated with neural repair during ischemic stroke recovery (59,60).…”

Identification of Dysregulated Mechanisms and Potential Biomarkers in Ischemic Stroke Onset

“…44 The miR-9-3p is upregulated in the brain tissue of IS patients, 45 and it may be a diagnostic marker for experimental and human mild head injury. 46 MiR-9 upregulation may target the expression of BDNF to promote neurodegeneration of dopaminergic neurons caused by neurotoxins and cell apoptosis. 47 Hypoxia or reoxygenation downregulate miR-374a-3p in endothelial cells, 48 so future work should explore whether this downregulation is associated with IS.…”