Table 1. Principal findings on animal and human studies on TBI-related miRNAs.

	Methods and Techniques		Main Findings		Model/ Patient Groups	Matrix	Experimental Setup
Animal Studies
[89]	microarray with 509 mature miRNA sequences from 3 species (rat, mouse, human)		13 upregulated, 14 downregulated (6h post TBI); 4 upregulated, 23 downregulated (24h post TBI); 16 upregulated, 11 downregulated (48h post TBI); 19upregulated, 5 downregulated (72h post TBI); miR-21 always upregulated		Adult Wistar rats	Cerebral cortex	6, 24, 48 and 72 hours post TBI
[88]	next generation sequencing platform		8 upregulated, 13 downregulated (1 day after CCI); 3 upregulated, 7 downregulated (7 days after CCI)		Sprague Dawley male rats subjected to CCI	Hippocampus	1 and 7 days post TBI
[87]	qRT-PCR		serum let-7i, miR-122, miR-340-5p upregulated both in LII and SII; serum miR-874 downregulated both in LII and SII; miR-200b upregulated in SII. Let-7i elevated also in cerebrospinal fluid		Male Spargue-Dawley rats	Blood and cerebrospinal fluid	SII and LII
[126]	qRT-PCR		miR-142-5p, miR-19b, miR-1928, miR-223-3p, miR-322-3p, miR-324, miR-421-3p, miR-463-5p and miR-674-3p, upregulated in both matrixes		Male albino Sprague Dawley rat	serum and amygdala	14 days PTSD
[92]	qRT-PCR		mir-21 upregulated (3 days after CCI)		Male Sprague-Dawley rats	ipsi- and contralateral hippocampal tissue	3h, 24h, 3 days, 15 days after CCI
[90]	microarray with 444 mature miRNA sequences		11 upregulated (3h after CCI); 8 upregulated (24h post CCI); 16 upregulated (3h and 24h post CCI)		Male Sprague-Dawley rats	hippocampus	3 hr and 24 hr after CCI
[132]	microarray		miR-142-3p, mir-144, mir-340-5p, mir-674-5p, miR-153, mir-186, mir-190, mir-132-5p, mir-138-1-3p upregulated (all time points); let-7b downregulated (all time points)		Adult Sprague-Dawley rats	ipsilateral hippocampus	1h, 1 day, 3 days, 5 days and 7 days post injury
Clinical Studies
[91]	microarray with 875 mature human miRNA sequences		27 upregulated in severe TBI vs HV; miR-765 upregulated in sTBI vs HV; miR-16, miR-92a downregulated in sTBI vs HV; mir-16 and mir-92a upregulated in patients with mTBI vs HV		Non-trauma HV, Orthopedic injury patients, Orthopedic and mTBI injury subjects, sTBI patients	plasma	24 h after TBI
[133]	qRT-PCR		miR-93, miR-191, and miR-499 upregulated in TBI vs controls (persistently elevated)		76 cases and 38 controls	serum	24 h and daily for up to 21 days after TBI
[7]	microarray with 754 mature human miRNA sequences		miR-184, miR-502, miR-505, miR-301b altered (mTBI+EC, day 1; miR-203, miR-654-3p, miR-655 altered (mTBI+EC, day 15); mir-425-5p altered (mTBI only); mir-21, mir-335 upregulated (sTBI+EC)		HV (30), EC injury patients (30), EC + mild TBI patients (30), EC + severe TBI patients (30)	serum	T0-1h, T4-12h, T48-72h and 2 weeks after TBI
[134]	microarray with 1500 human small noncoding RNAs		mir-671-5p downregulated		9 mTBI and 9 control cases	blood mononuclear cells
[135]	custom miRNA PCR array		mir142-3p and mir423-3p downregulated over time		3 groups of TBI patients classified on the basis of GCS and WPTAS	plasma	arrival, day 5 and day 30
	Methods and Techniques	Main Findings		Model/ Patient Groups		Matrix	Experimental Setup
Clinical Studies
[95]	384-well TaqMan Low Density Human MicroRNA Array Cards	miR-151-5p, miR-195, miR-20a, miR328, miR-362- 3p, miR30d, miR-451, miR-486, miR-505, miR-92a upregulated (mild to moderate TBI and severe TBI)		sTBI (serum, 8; CSF, 8); mild to moderate TBI (serum, 8); orthopedic injury patients (serum, 7); normal controls (serum, 8; CSF, 6)		CSF and serum	2 days after injury
[137]	96.96 Dynamic Array IFC (Proximity Extension Assay); nCounter Human v3 miRNA Expression Assay Kits	21 miRNAs differentially expressed; miR-27b-3p, let- 7i-5p, miR-142-3p, miR-107, miR-135b-5p confirmed in validation cohort. Let-7i-5p confirmed as the best biomarker of mTBI		6 concussed and 6 non-concussed athletes; 22 concussed athletes (discovery cohort); 10 matched non-concussed athletes (validation cohort)		saliva	48–72 h after a concussion
[136]	qRT-PCR	miR425-5p was significantly down-regulated in Group A compared with Group B and HV		15 concussed athletes divided into 2 groups: Group A (n=9, assessed within a week post-concussion); Group B (n=6, assessed over 2 weeks); 8 HV		serum
[138]	36 bp single end reads on an Illumina NextSeq 500	miR-10b-5p, miR-30b-5p, upregulated in both serum and saliva; miR-3678-3p, miR-455-5p, miR-5694, miR-6809-3p, and miR-92a-3p, downregulated in both serum and saliva		MMA fighters		saliva and serum	1 week or 1 hour prefight, immediately post-fight, 2–3 days, 1 week, 3+ weeks
[139]	NEXTflex Small RNA‐Seq Kit v3 (Illumina HiSeq 2500)	miR182‐5p, miR‐221‐3p, mir‐26b‐5p, miR‐320c, dpwnregulated; miR‐29c‐3p, miR‐30e‐5p, upregulated		pediatric patients sampled within 14 days of initial injury; CSF samples collected from 8 children with sTBI and 2 controls; 61 saliva samples from mTBI cohort and 19 from control cohort		salivar and CSF	day 1, day 4‐7, and day 8‐ 17 after injury
[140]	NEXTflex Small RNA Sequencing Kit version 3, Illumina HiSeq 2500	14 differentially expressed miRNAs; miR-320c-1, miR-133a-5p, miR-769-5p, let-7a-3p, and miR-1307-3p identified patients with prolonged symptoms		children, 22 acute concussion symptoms group; 30 prolonged concussion symptoms		saliva
[141]	Affymetrix GCS300 with FlashTag Biotin HSR	miR-451 only detected in cerebrospinal microparticles from TBI patients; miR-9 more prevalent in cerebrospinal microparticles from controls		26 sampling over a period of 2 years		cerebrospinal microparticles
[142]	GeneChip miRNA 3,0 Array with 5818 human premature and mature miRNAs	miR-141, miR-572, miR-181a, miR-27b, miR-483-5p, miR-30b, miR-1289, miR-431, miR-193b, miR-499-3p upregulated; miR-1297, miR-33b, miR-933, miR-449b downregulated		comatose patients (26); controls (21)		CSF
[137]	Human miRNA microarrays from Agilent Technologies in plasma samples; Agilent miRNA microarray system; Gene Cluster (version 3.0) and Java Treeview software programs to visualize the miRNAs	65 miRNAs upregulated and 29 miRNAs downregulated in mild TBI; 33 miRNAs upregulated and 27 miRNAs downregulated in moderate TBI; 16 miRNAs upregulated and 6 miRNAs downregulated in severe TBI; 13 miRNAs altered in all TBI groups (hsa-miR-1281, hsa-miR-1304-3p, hsa-miR-1825, hsa-miR-2861, hsa-miR-3195, hsa-miR-328-5p, hsa-miR-3665, hsa-miR-4665-3p, hsa-miR-4669, hsa-miR-4725-5p, hsa-miR-6867-5p, hsa-miR-762 and hsa-miR-940)		90 patients with mild, moderate and severe TBI (15 in the microarray group, 75 in the validation group); 30 Healthy Volunteers (5 in the microarray group, 25 in the validation group)		plasma	The sampling times in the mild, moderate, and severe TBI groups were 7.54±2.81, 6.08±0.79, and 6.16±1.19, respectively.

Abbreviations: CCI, controlled cortical impact injury; SII, short interval injury group; LII, long interval injury group; PTSD, post-traumatic stress disorder; HV, healthy volunteers; mTBI, mild TBI; sTBI, severe TBI patients; EC, extra-cranial; GCS, Glasgow Coma Scale; WPTAS, Westmead post-traumatic Amnesia scale; CSF, cerebrospinal fluid.