Defining Biological Phenotypes of Mild Traumatic Brain Injury Using Saliva MicroRNA Profiles

Abstract

Concussion is a heterogeneous injury that relies predominantly on subjective symptom reports for patient assessment and treatment. Developing an objective, biological test could aid phenotypic categorization of concussion patients, leading to advances in personalized treatment. This prospective multi-center study employed saliva micro-ribonucleic acid (miRNA) levels to stratify 251 individuals with concussion into biological subgroups. Using miRNA biological clusters, our objective was to assess for differences in medical/demographic characteristics, symptoms, and functional measures of balance and cognition. The miRNAs that best defined each cluster were used to identify physiological pathways that characterized each cluster. The 251 participants (mean age: 18 ± 7 years; 57% male) were optimally grouped into 10 clusters based on 22 miRNA levels. The clusters differed in age (χ 2 = 19.1, p = 0.024), days post-injury at the time of saliva collection (χ 2 = 22.6; p = 0.007), and number of prior concussions (χ 2 = 17.6, p = 0.040). The clusters also differed in symptom reports for fatigue (χ 2 = 17.7; p = 0.039), confusion (χ 2 = 22.3; p = 0.008), difficulty remembering (χ 2 = 22.0; p = 0.009), and trouble falling asleep (χ 2 = 17.2; p = 0.046), but not objective balance or cognitive performance ( p > 0.05). The miRNAs that defined concussion clusters regulate 16 physiological pathways, including adrenergic signaling, estrogen signaling, fatty acid metabolism, GABAergic signaling, synaptic vesicle cycling, and transforming growth factor (TGF)-β signaling. These results show that saliva miRNA levels may stratify individuals with concussion based on underlying biological perturbations that are relevant to both symptomology and pharmacological targets. If validated in a larger cohort, miRNA assessment could aid individualized, biology-driven concussion treatment.

Non-invasive fluid biomarkers in the diagnosis of mild traumatic brain injury (mTBI): a systematic review

“…Only one study assessed multiple biomarkers 10. The most commonly studied biomarker was salivary microRNA which was examined in 11 studies 11–21. Cortisol was assessed in four studies 10 22–24.…”

“…(A) Representation of enrollment and fluid sampling in mTBI subjects for studies assessing RNA-based salivary biomarkers. Hicks et al 16 19 have same trial design. Gu et al 14 were not represented in the figure due to unspecified time frame from mTBI to enrollment in study.…”

Epigenetic Alterations in Sports-Related Injuries

“…In the cellular response to secondary damage, neurons use miRNA signalling to regulate synaptogenesis and neuroplasticity. As a result, miRNA profiles during the subacute period may also telegraph the trajectory of brain recovery [ 258 ]. There are many pathways targeted by miRNAs in the pathophysiology of TBI, including: adrenergic signalling, AMP kinase activity, oestrogen signalling, fatty acid metabolism, GABAergic signalling, synaptic vesicle cycling, and TGF-β signalling [ 258 ].…”

“…As a result, miRNA profiles during the subacute period may also telegraph the trajectory of brain recovery [ 258 ]. There are many pathways targeted by miRNAs in the pathophysiology of TBI, including: adrenergic signalling, AMP kinase activity, oestrogen signalling, fatty acid metabolism, GABAergic signalling, synaptic vesicle cycling, and TGF-β signalling [ 258 ]. While studies demonstrating DNA methylation and histone changes in response to sports-related brain injuries have mostly used animal models, studies on miRNAs have recently begun to be performed in human athletes.…”

Confounding Factors Impacting microRNA Expression in Human Saliva: Methodological and Biological Considerations

“…Expression studies of miRNAs from human saliva have been increasing over the past decade, across a number of clinical disciplines. Notably, high powered cohort studies identify predictive miRNAs for of autism spectrum disorder [ 4 , 16 , 17 ], traumatic brain injury [ 18 , 19 , 20 , 21 ] endometriosis [ 22 ], and a variety of cancers [ 23 , 24 , 25 ]. Other recent studies include the prediction of alcohol use disorder [ 26 , 27 ], Parkinson’s Disease [ 28 , 29 ], and malignant pleural effusion [ 30 ].…”