Salivary small non-coding RNAs as biomarkers for concussion management

Watson, Callum Nicholas ORCID: 0000-0003-2511-5501 (2021). Salivary small non-coding RNAs as biomarkers for concussion management. University of Birmingham. Ph.D.

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Abstract

Concussion occurs when a “biomechanical force, transiently disturbs normal brain function causing neurological, cognitive and behavioural signs and symptoms”. However, the diagnosis of concussion is imprecise and challenging.
Currently, there is a great deal of attention on concussion in contact sports due to the immediate and potential long-term effects on the brain. The transient and complex array of symptoms that occur, mean patient compliance is essential, to quantify the neurological deficit that enables an experienced assessor to diagnose accurately. The future in concussion diagnosis therefore lies in the development of a simple, relevant, rapid and objective assessment of the trauma to the brain. The most likely candidates are either brain imaging e.g. MRI, or measurement of a relevant biomarker or group of biomarkers. Rapid diagnosis is particularly needed in contact sports such as rugby and football to enable players to safely return to play. The development of an objective diagnostic test may also help to explain the longer-term impact of head injury, and be applicable to other sports and situations e.g. military or household accidents etc.
In this thesis, I have hypothesised that changes in small non-coding RNAs (sncRNAs) and extracellular vesicles (sEVs) in saliva may be used for the diagnosis of concussion. Changes in either or both of these in saliva could reflect rapid changes in the brain and systemic circulation due to the concussion. Understanding of mechanism through which these changes could occur is beyond the scope of this thesis.
The Study of Concussion in Rugby Union through MicroRNAs (SCRUM) (ISRCTN16974791) has used next Generation Sequencing (NGS) and qPCR validation steps to analyse 390 saliva samples from the top two tiers of professional rugby in England. Samples were collected during training, 3 hours and 48-72 hours post-injury. Controls were taken from groups with musculoskeletal injury, uninjured players, and players in whom concussion had been suspected but ruled out on.
I have identified 12 sncRNAs that undergo up-regulation in saliva of players with concussion (ten in the immediate aftermath, two 48-72 hours post injury). Two sncRNA families had more than one member responding to injury, namely the RNU-6 snRNA and Let-7 miRNA families. Further work is required to confirm whether measurement of these, or a combination of sncRNAs, can be used to diagnose concussion. sEVs were measured in saliva using a new assay, the ExoView, but no clear pattern of change was observed. This is likely to reflect the complexity of sEVs which vary markedly in size and can be generated from multiple cell types.
Studies on miRNAs, were extended to a deceased group of patients who had been diagnosed with Alzheimer’s disease (AD), in view of a possible historical link to concussion. Brain samples were obtained from the South West Dementia Brain Bank (SWDBB, University of Bristol). Two progressive stages of AD and a control group were assessed using qPCR. The Let-7 family miRNAs, hsa-let-7i-5p and hsa-let-7a-5p, were found to be differentially expressed in the brains of AD patients. Further work is required to understand the function of these two mRNAs in the brain.
In conclusion, this study has identified several sncRNAs that may change in saliva in response to concussion and which could form the basis of a future diagnostic test. This work has also provided preliminary evidence of changes in the Let-7 family of miRNAs in AD. Further work is required to understand the significance of changes in sncRNAs in concussion and AD, and a possible link between their role (if any) in these two disorders.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):