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• The present study is the first to identify and characterize a previously unknown microRNA, miR-7844-5p, that may be involved in cellular signaling cascades following repetitive head impact exposure. • miR-7844-5p directly targets messenger RNAs involved in mitochondrial apoptosis, autophagy regulation, and neurodegenerative disease. • microRNA cargo may be selectively packaged into small, extracellular vesicles following repetitive head impact exposure. Considering the potential cumulative effects of repetitive head impact (HI) exposure, we need sensitive biomarkers to track short- and long-term effects. Circulating small extracellular vesicles (sEVs) (<200 nm) traffic biological molecules throughout the body and may have diagnostic value as biomarkers for disease. The purpose of this study was to identify the microRNA (miRNA) profile in circulating sEVs derived from human plasma following repetitive HI exposure. Healthy adult (aged 18–35 years) soccer players were randomly assigned to one of 3 groups: the HI group performed 10 standing headers, the leg impact group performed 10 soccer ball trapping maneuvers over 10 min, and the control group did not participate in any soccer drills. Plasma was collected before testing and 24 h afterward, and sEVs were isolated and characterized via nanoparticle tracking analysis. Next-generation sequencing was utilized to identify candidate miRNAs isolated from sEVs, and candidate microRNAs were analyzed via quantitative polymerase chain reaction. In silico target prediction was performed using TargetScan (Version 7.0; targetscan.org) and miRWalk (http://mirwalk.umm.uni-heidelberg.de/) programs, and target validation was performed using luciferase reporter vectors with a miR-7844-5p mimic in human embryonic kidney (HEK) 293T/17 cells. Plasma sEV concentration and size were not affected across time and group following repetitive HI exposure. After 24 h, the HI read count from next-generation sequencing showed a 4-fold or greater increase in miR-92b-5p, miR-423-5p, and miR-24-3p and a 3-fold or greater decrease in miR-7844-5p, miR-144-5p, miR-221-5p, and miR-22-3p. Analysis of quantitative polymerase chain reaction revealed that leg impact did not alter the candidate miRNA levels. To our knowledge, miR-7844-5p is a previously unknown miRNA. We identified 8 miR-7844-5p mRNA targets: protein phosphatase 1 regulatory inhibitor subunit 1B (PPP1R1B), LIM and senescent cell antigen-like domains 1 (LIMS1), autophagy-related 12 (ATG12), microtubule-associated protein 1 light chain 3 beta (MAP1LC3B), integrin subunit alpha-1 (ITGA1), mitogen-activated protein kinase 1 (MAPK1), glycogen synthase kinase 3β (GSK3β), and mitogen-activated protein kinase 8 (MAPK8). Collectively, these data indicate repetitive HI exposure alters plasma sEV miRNA content, but not sEV size or number. Furthermore, for the first time we demonstrate that previously unknown miR-7844-5p targets mRNAs known to be involved in mitochondrial apoptosis, autophagy regulation, mood disorders, and neurodegenerative disease. [Display omitted] [ABSTRACT FROM AUTHOR]

Studies have shown compelling evidence that suggests heading soccer ball might lead to brain trauma. Researchers have attempted to experimentally quantify head acceleration induced by soccer ball heading. A series of linear accelerometers as well as angular accelerometer were used to measure head accelerations. This method however is limited to measuring only head acceleration during the impact. However, it is essential to analyse the acceleration of the brain in addition to the acceleration of the head that takes place during a soccer-heading manoeuvre. Since the motion of the brain is almost impossible to be quantified experimentally, this work focuses on performing finite element (FE) analysis of soccer heading to study the motions of both the head and the brain during the impact. FE model of soccer ball was developed and validated against published experimental data as well as a more detailed model. Moreover, FE model of human head that consists of the skull, facial bones, cerebrospinal fluid (CSF) layer and the brain was also developed and validated against experimental data of blunt impact on human cadaver. Both validated models were assembled to perform the soccer heading simulations. Linear and angular accelerations of the skull and the brain generated are comparable to those of experimental data. However, it has underestimated the angular acceleration due to the absence of neck in the model, but with comparable acceleration profile. Linear and angular accelerations of the brain were found to be almost similar to those of the head, which is contradictory to our initial hypothesis. Further study such as ball impact on instrumented dummy skull is required to corroborate the findings. Nonetheless, the FE models were able to replicate the head accelerations sustained during soccer ball heading satisfactorily. The simulation results show that the models can be employed in finding protective materials that can reduce the accelerations, thus minimising the probability of suffering from long-term brain trauma due to soccer ball heading. [ABSTRACT FROM AUTHOR]

Abstract: There has been a long debate among researchers on whether soccer heading is capable of causing brain trauma. A recent study suggests that headings exceeding a threshold level of 855 to 1,550 per year, results in microstructural abnormalities in the brain's white matter. This shows that brain trauma is caused by cumulative effect of repetitive headings. The use of protective headgear is one of the suggested preventive measures to protect the brain especially for younger players. Researchers have tested several commercial headgears and found that they are only effective in head-to-head impact, but ineffective in attenuating impact caused by heading. This is due to the fact that soccer ball is compliant in nature relative to the head. The aim of this study is to investigate materials that can be utilised to minimise the acceleration of the brain caused by soccer heading. A vertical drop ball test was conducted on an instrumented dummy skull. The inner cavity of the skull is filled with ultrasound gel that represents the brain. Six impact-absorbing materials were tested to determine the most effective material that reduces the acceleration of the brain substitute. The speed of the ball before and after impact as well as impact duration were measured using high-speed camera. Coefficient of restitution was calculated to ensure the material is not only capable of reducing the brain acceleration, but also maintains heading performance. It was found that polymer kneepad foam is the most effective material that minimises the acceleration of brain substitute whilst maintaining the speed of the ball after impact. [Copyright &y& Elsevier]