Head Impact Exposure in Youth and Collegiate American Football

The relationship between head impact and subsequent brain injury for American football players is not well defined, especially for youth. The objective of this study is to quantify and assess Head Impact Exposure (HIE) metrics among youth and collegiate football players. This multiseason study enrolled 639 unique athletes (354 collegiate; 285 youth, ages 9–14), recording 476,209 head impacts (367,337 collegiate; 108,872 youth) over 971 sessions (480 collegiate; 491 youth). Youth players experienced 43 and 65% fewer impacts per competition and practice, respectively, and lower impact magnitudes compared to collegiate players (95th percentile peak linear acceleration (PLA, g) competition: 45.6 vs 61.9; 95th percentile PLA practice: 42.6 vs 58.8; 95th percentile peak rotational acceleration (PRA, rad∙s–2) competition: 2262 vs 4422; 95th percentile PRA practice: 2081 vs 4052; 95th percentile HITsp competition: 25.4 vs 32.8; 95th percentile HITsp practice: 23.9 vs 30.2). Impacts during competition were more frequent and of greater magnitude than during practice at both levels. Quantified comparisons of head impact frequency and magnitude between youth and collegiate athletes reveal HIE differences as a function of age, and expanded insight better informs the development of age-appropriate guidelines for helmet design, prevention measures, standardized testing, brain injury diagnosis, and recovery management

Early Detection and Intervention Strategies for Acute Cartilage Injury after Intact Joint Impact: In-vitro Porcine Knee Model

Traumatic injury to cartilage has been shown to lead to Post-traumatic Osteoarthritis (PTOA). The acute phase of PTOA is characterized with increased expression of aggrecanases and inflammatory cytokines in the injured cartilage. Aberrant regulation of microRNAs (miRNAs) in the cartilage has been associated with the pathogenesis of PTOA. The objective of this dissertation work was to elucidate potential early detection and intervention strategies for acute knee injury based on the miRNA and genetic changes of knee joint tissues. An ex-vivo intact joint impact injury model was created to examine the miRNA and inflammatory and degenerative gene expression in cartilage and meniscus during the acute phase of injury. Using this model, four potential early intervention treatments for PTOA were compared, and their effects on the early inflammatory and catabolic events after acute cartilage injury were determined at 8 hours after intact joint impact. The time- and concentration-dependent nature of cellular and extracellular miRNAs in chondrocytes, synoviocytes, and meniscus cells as influenced by inflammatory cytokines and the ratio of extracellular miRNA were analyzed as potential indicator of early OA progression. In a proof of concept study, the ratios of synovial fluid miRNAs after acute cartilage injury were examined using the ex-vivo intact joint impact model as potential indicator of acute cartilage injury. A recommendation for further study is enclosed.</p

Early Intervention Strategies For Acute Cartilage Injury Ex-vivo Porcine Knee Model

Objectives: Traumatic injury to cartilage has been shown to lead to Post-Traumatic Osteoarthritis (PTOA). The acute phase of PTOA is characterized with increased expression of aggrecanases and inflammatory cytokines in the injured cartilage. Early intervention therapies aim to be administered during the acute phase for the prevention of PTOA development. Our objective was to determine the effect of Interleukin Receptor Antagonist Protein (IRAP), Hyaluronan (HA), and Mesenchymal Stem Cell (MSC) treatment as early intervention strategies by examining the changes in microRNA (miRNA) and mRNA expression in cartilage at 8 hours after impact injury. Methods: Custom impact device was used to create replicable injury ex-vivo to intact porcine knee joint. Injury was caused by dropping a 10kg weight one time from 1m directly above the knee in extension. One hour after impact 20µg/mL IRAP, 15mg/mL HA (MW 1.9 MDa), or 5x106 P4 MSCs in 1mL saline was intra-articularly injected. Control legs (no injury) and injury legs (injury, no treatment) received saline injection. At 8 hours post-injury, cartilage samples were harvested for genetic expression analysis. Genetic expression of miR-140 (regulates ADAMTS-5) miR-125b (regulates ADAMTS-4), ADAMTS-4, ADAMTS-5, MMP-3, IL-1β, and TNF-α were analyzed by RT-PCR. Groups were compared by one-way analysis of variance followed by Tukey's post-hoc test. A P-value <0.05 was considered significant (N=3 pigs/group). Results: After IRAP treatment, expressions of ADAMTS-4, ADAMTS-5, IL-1β, and TNF-α in cartilage were significantly down-regulated from injury group (all P<0.001) (Figure 1A). Expressions of miR-140 and miR-125b were significantly up-regulated after IRAP treatment as compared to control and injury (both P<0.05 to control, P<0.001 to injury) (Figure 1B). MiR-27b expression was significantly up-regulated after treatment as compared to control (P<0.001). After HA treatment, expressions of ADAMTS-4, ADAMTS-5, MMP-3, and TNF-α were significantly up-regulated from control (all P<0.05) (Figure 1C). Expression of IL-1β after HA treatment tended for up-regulation (P=0.15). Expressions of miR-125b, miR-140, and miR-27b were significantly up-regulated after HA treatment as compared to control and injury groups (all P<0.05) (Figure 1D). After MSC treatment, relative expressions of ADAMTS-4, ADAMTS-5, and IL-1β were significantly up-regulated (all P<0.01) as compared to controls (Figure 1E). Expression of TNF-α after treatment tended for up-regulation (P=0.14). No significant differences were found in miRNA expressions after MSC treatment (Figure 1F). Conclusion: The results show that IRAP, HA, and MSC treatment administered during acute phase of cartilage injury each have a distinct effect on catabolic and inflammatory regulation. HA and MSC treatment did not have significant effect on the inflammatory and catabolic response of injured cartilage within the first 8 hours of injury. However, the beneficial effects of HA may take place beyond the acute time frame as suggested by increased miR-125b and miR-140 expressions after treatment. IRAP treatment increased expressions of miR-140, -125b, and -27b in cartilage, indicating increased inhibition of their respective enzymes, as shown by reduced aggrecanase and inflammatory genetic expressions. Clinically, these findings support the potential of IRAP and HA treatment as early intervention strategies for the prevention of cartilage degeneration after impact injury

NOVEL MEASURING SYSTEM OF ATP-INDUCED TRANSMEMBRANE POTENTIAL CHANGE OF NUCLEUS PULPOSUS CELLS

Low back pain is a serious concern in industrialized societies that affects millions of people around the world [1]. It can be attributed to several spine disorders; intervertebral disc (IVD) degeneration being one of the most common causes [2]. IVDs are the largest avascular tissue in the body and are composed of two differentiated anatomical structures: the nucleus pulposus (NP) and the annulus fibrosus (AF). The ability to withstand compressive loads due to weight and bending is provided by the swelling of the NP structure, while the ability to resist tensile forces during bending and twisting is provided by the AF fibers [3]. The biomechanical functions of NP and AF rely on their extracellular matrix (ECM) structure and composition. Previous studies have demonstrated that static and dynamic compressive loading alters ATP production, which may have an effect on ECM synthesis [2]. In addition, dynamic loading has shown an increase in ATP release from NP cells, which may contribute to endplate calcification and therefore to IVD degeneration [2, 4]. When tissue is damaged, ATP, which is found in millimolar concentrations in all cells, leaks or is released into the extracellular milieu [5, 6]. Extracellular ATP is a powerful signaling molecule that can regulate cell metabolism, survival, and growth [7]. However, IVD cell response to ATP has not been investigated. The receptors involved in transducing responses to ATP are found in many tissues throughout the body and are responsible for different kinds of intercellular communication. ATP receptor subtypes are ligand-gated ion channels (P2X) and G-protein coupled receptors (P2Y). P2X receptors show calcium permeability while P2Y receptors mediate calcium release from intracellular stores in response to ATP [6]. Direct ATP application to the cell has been reported to cause a change in membrane conductance in a variety of tissues [8]. The voltage sensitive dye di-8-ANEPPS allows for a noninvasive method of measuring fluorescence changes of the cell membrane, which are proportional to variations of the transmembrane potential [8]. Therefore, the objectives of this study were (1) to develop a novel transmembrane potential measuring system using di-8-ANEPPS dye and (2) to investigate the response of NP cells to ATP by measuring the change in transmembrane potential.</jats:p

Effects of Anti-Inflammatory Agents on Expression of Early Responsive Inflammatory and Catabolic Genes in Ex Vivo Porcine Model of Acute Knee Cartilage Injury

Objective Early intervention therapies targeting inflammation and cell death during the acute phase of cartilage injury have the potential to prevent posttraumatic osteoarthritis. The objective of this study was to investigate the effects of interleukin receptor antagonist protein (IRAP), hyaluronan (HA), dexamethasone (DEX), and mesenchymal stem cell (MSC) treatment on the expression of established genetic markers for matrix degradation, apoptosis, and inflammation in articular cartilage during the acute phase of injury. Design A custom impact device was used to create replicable injury ex vivo to intact porcine knee joint. One hour after impact, IRAP, HA, DEX, or MSCs was intra-articularly injected. At 8 hours postinjury, cartilage and meniscus samples were harvested for genetic expression analysis. Expression of miR-27b, miR-140, miR-125b, miR-16, miR-34a, miR-146a, miR-22, ADAMTS-4, ADAMTS-5, MMP-3, IL-1β, and TNF-α was analyzed by real-time polymerase chain reaction. Results At 8 hours postinjury, expression of ADAMTS-4, ADAMTS-5, MMP-3, IL-1β, and TNF-α in cartilage was significantly decreased in IRAP- and DEX-treated joints as compared to nontreated injured joints, whereas only IRAP upregulated expression of miR-140, miR-125b, miR-27b, miR-146a, and miR-22 in cartilage. HA and MSC treatments had no significant effects on catabolic and inflammatory gene expression in cartilage. However, HA treatment significantly upregulated expression of all miRNAs except miR-16. In addition, the treatments tested also exhibited significant influences on meniscus. Conclusions This study provides a valuable starting point for further research into potential targets for and efficacy of various early intervention strategies that may delay or prevent the progression of posttraumatic osteoarthritis after acute cartilage injury