Subconcussive Head Impact Results in a Unique Circulating Exosomal MicroRNA Signature

Abstract

A large segment of the population participates in sports (e.g. football and soccer) and endure hundreds to thousands of low level head impacts over their lifetime. While a continuously growing body of evidence indicates concussive head injury can lead to long term medical problems, little is known about the effects of subconcussive head impact, that is mild head impact that does not result in a clinical indication of concussion. Recently our group has shown that subconcussive head impact results in acute vestibular dysfunction. Additional recent evidence indicates subconcussive head impact results in memory loss for up to 24 hours. Thus, the possibility exists that both high magnitude head impact like concussions as well as repetitive low levels of head impact lead to pathological changes. Recent research has shown that small circulating molecules termed exosomes contain cargo including microRNAs that may be indicative of pathological events and signaling occurring in the tissue from which they were released. Thus, the purpose of this study was to identify a unique circulating exosomal microRNA profile indicative of subconcussive head impact. We used a common soccer heading task as a controlled head impact model to elicit subconcussive head impact in college males (n=6), in which subjects headed a soccer ball 10 times at a set velocity from ~30 meters away. Pre, immediately post, and 24 hours post blood samples were collected. Exosomes were isolated from plasma, and total RNA, including microRNA, was isolated from exosomes. Small RNA Next generation sequencing (NGS) was performed on microRNAs isolated from exosomes in pre and 24 hour post plasma to unbiasedly identify alterations in levels of exosomal microRNAs. A unique microRNA signature in circulating exosomes was identified 24 hours following subconcussive head impact. Specifically, based on abundance and fold change a small unique panel was identified including three microRNAs that were increased four fold or more (miR‐92b‐3p, miR‐423‐5p, and miR‐24‐3p), and four microRNAs that were decreased three fold or more (miR‐7844‐5p, miR144‐5p, miR‐221‐5p, and miR‐22‐3p). To verify NGS results, quantitative real time polymerase chain reaction (qPCR) was performed on microRNAs at all time points. Further, to verify specificity of head impact exosomal microRNAs in the panel were measured via qPCR from a group the received soccer ball impact to the gastrocnemius muscle. Interestingly, several of the identified microRNAs are known to be involved in or associated with neurological dysfunction and disorders. In conclusion, subconcussive head impact leads to a unique circulating exosomal microRNAs signature that could potentially be indicative of head injury following repetitive subconcussive head impacts.Support or Funding InformationSupported by NIH GM087239