Traumatic brain injury (TBI) is the most common injury in childhood, and it is the leading cause of disability. Early childhood is an area of specific interest because it is a period of rather significant vulnerability to longer-standing problems. Better health and behavior-related outcomes generally improve when diagnosis occurs early enough to inform evidence-based interventions adequately. However, there continues to be relatively weak identification of concussions in early childhood, and misdiagnoses often lead children to receive the incorrect intervention if they receive intervention at all. Clinicians need to identify symptoms of a concussion immediately following injury. To this end, the present study examines the literature to determine domains, and any narrow abilities impacted following a concussion. Assessments items were generated based on a review of published norm references tests and task demands analyses (n = 18). Testing items were cross-referenced using developmental literature to ensure they were appropriate for assessment for children age 3 years. Via the Delphi survey method, a heterogeneous panel of experts (Round 1 n = 17; Round 2 n = 13), including physicians, psychologists, school nurses, speech and language pathologists, and athletic trainers, offered their opinion regarding what areas are impacted following a concussion. The panel provided clarification on the operational definitions and agreed that the testing items, indeed, were developmentally appropriate. The group also decided that a paraprofessional could administer the items with minimal training, which is an essential consideration because children in early childhood are often cared for by professionals untrained in assessment, working in daycare or preschool settings. The present study concludes that, indeed, an evaluation of concussions symptoms that are like traditional sideline assessments is possible. However, the results of this assessment are only preliminary, and there was no evidence for validity based on response processes or relations to other variables; likewise, reliability data are unavailable at this time. Recommendations for future research are included, and ideas to move toward standardization are presented. Recommendations for the training of paraprofessionals in these assessment procedures, too, are outlined. / School Psychology

The focus of this dissertation was the biomechanics of blast-induced traumatic brain injury (bTBI). This study had three specific aims. One of the specific aims was to investigate the thoracic mechanism of bTBI by characterizing the cerebral blood pressure change during local blast exposure to head or chest in a rat model. This model utilized a shock tube to simulate the blast wave. The results showed that there is a blood pressure rise with high amplitude and short duration during both Head-Only and Chest-Only exposure conditions. It was shown that cerebral blood pressure rise was significantly higher in Chest-Only exposure, and resulted in astrocyte reactivation, and infiltration of blood-borne macrophages into the brain. It was concluded that due to chest exposure to a blast wave, high amplitude pressure waves that transfer from thoracic large vessels to cerebrovasculature can lead to blood-brain barrier disruption or perivascular injury and consequently trigger secondary neuronal damage. The second and third aims were related to the viscoelasticity and heterogeneity of brain tissue respectively for blast rate loading conditions. For the second specific aim, a novel test method was developed to apply shear deformation to samples of brain tissue with strain rates in the range of 300 to 1000 s-1. The results of shear tests on cylindrical samples of bovine brain showed that the instantaneous shear modulus (about 6 kPa) increased about 3 times compared to the values reported in the literature. For the third specific aim, local viscoelastic behavior of rat brain was characterized using a micro-indentation setup with the spatial resolution of 350 mm. The results of micro-indentation tests showed that the heterogeneity of brain tissue was more pronounced in long-term shear moduli. Moreover, the inner anatomical regions were generally more compliant than the outer regions and the gray matter generally exhibited a stiffer response than the white matter. The results of this study can enhance the prediction of brain injury in finite element models of TBI in general and models of bTBI in particular. These results contribute to development of more biofidelic models that can determine the extent and severity of injury in blast loadings. Such predictions are essential for designing better injury mitigation devices for soldiers and also for improving neurosurgical procedures among other applications. / Mechanical Engineering / Accompanied by one .pdf file.

Recent clinical and preclinical reports have identified traumatic brain injury (TBI) as an important risk factor affecting the development of substance use disorders (SUDs). Notably, these studies show that factors like age at the time of injury and TBI severity may increase the risk of substance abuse behavior post-TBI. Furthermore, radiological assessments in clinical TBI populations have observed neuropathology in select brain regions that form key neurocircuits that mediate drug reward and drug-seeking behavior. Therefore, the effects of TBI on the function of these brain structures may influence the risk of substance abuse behavior following brain injury. In order to test the effect of experimental TBI on substance abuse behavior, we utilized two premiere preclinical models: 1) the controlled cortical impact (CCI) model of experimental TBI and 2) a biased, three-phase, cocaine conditioned place preference (CPP) assay. Furthermore, we characterized the effect of experimental TBI on / Pathology

Several efforts have been made in the past half century to characterize the behavior of brain tissue under different modes of loading and deformation rates; however each developed model has been associated with limitations. This dissertation aims at addressing the non-linear and rate dependent behavior of brain tissue specially in high strain rates (above 100 s-1) that represents the loading conditions occurring in blast induced neurotrauma (BINT) and development of a universal constitutive model for brain tissue that describes the tissue mechanical behavior from medium to high loading rates.. In order to evaluate the nature of nonlinearity of brain tissue, bovine brain samples (n=30) were tested under shear stress-relaxation loading with medium strain rate of 10 s-1 at strain levels ranging from 2% to 40% and the isochronous stress strain curves at 0,1 s and 10 s after the peak force formed. This approach enabled verification of the applicability of the quasilinear viscoelastic (QLV) theory to brain tissue and derivation of its elastic function based on the physics of the material rather than relying solely on curve fitting. The results confirmed that the QLV theory is an acceptable approximation for engineering shear strain levels below 40% that is beyond the level of axonal injury and the shape of the instantaneous elastic response was determined to be a 5th order odd polynomial with instantaneous linear shear modulus of 3.48±0.18 kPa. To investigate the rate dependent behavior of brain tissue at high strain rates, a novel experimental setup was developed and bovine brain samples (n=25) were tested at strain rates of 90, 120, 500, 600 and 800 s-1 and the resulting deformation and shear force were recorded. The stress-strain relationships showed significant rate dependency at high rates and was characterized using a QLV model with a 739 s-1 decay rate and validated with finite element analysis. The results showed the brain instantaneous elastic response can be modeled with a 3rd order odd polynomial and the instantaneous linear shear modulus was 19.2±1.1 kPa. A universal constitutive model was developed by combining the models developed for medium and high rate deformations and based on the QLV theory, in which the relaxation function has 5 time constants for 5 orders of magnitude in time (from 1 ms to 10 s) and therefore, is capable of predicting the brain tissue behavior in a wide range of deformation rates. Although the universal model presented in this study was developed based on only shear tests and the material parameters could not be found uniquely, by comparing the results of this study with previously available data in the literature under tension unique material parameters were determined for a 5 parameter generalized Rivlin elastic function (C10=3.208±0.602 kPa, C01=4.191±1.074 kPa, C11=79.898±18.974 kPa, C20=-37.093±7.273 kPa, C02=-37.712±5.678 kPa). The universal constitutive model for brain tissue presented in this dissertation is capable of characterizing the brain tissue behavior under large deformation in a wide range of strain rates and can be used in computational modeling of Traumatic Brain Injury (TBI) to predict injuries that result from falls and sports to automotive accidents and BINT. / Mechanical Engineering

Traumatic brain injury (TBI) is a prominent healthcare concern in the U.S. as millions of TBI-related emergency department visits occur annually. Recent reports estimate more than 5 million Americans currently suffer from life-long disabilities and psychiatric complications associated with TBI. While the risk of TBI has conventionally been considered to be male dominated, analyses of sex-comparable sports indicate that rates of concussions are higher and recovery time is longer following brain injury in females. Following anxiety and depression, substance use disorder (SUD) is the third most common de-novo neuropsychiatric condition diagnosed in both male and female TBI patients. Importantly, during adolescence the primary neuronal networks that regulate reward behaviors and perception of drug-induced euphoria are not fully developed, corroborating epidemiological studies identifying TBI sustained during adolescence as a risk factor for problematic drug use. Yet, to date, little is known about how TBI-induced molecular changes affect brain structures essential for the perception of reward and processing drug-induced euphoria. The following experiments were designed to test the hypothesis that adolescent TBI-induced neuroinflammation in areas such as prefrontal cortex (PFC) and nucleus accumbens (NAc) results in remodeling of neuronal reward networks and affect how the rewarding effects of cocaine shift as a consequence of TBI. Notably, the extent of sex differences in SUD susceptibility in TBI has not be investigated. Therefore, we also investigated whether the immune response stimulated by early-life TBI alters maturation of reward neurocircuits, leading to increased SUD vulnerability in a sex-dependent manner. Following the induction of TBI using the controlled cortical impact (CCI) model of brain injury, we utilized a biased, three-phased cocaine conditioned place preference (CPP) assay to assess the behavioral response to the rewarding effects of cocaine following adolescent injury in male and female C57BL6 mice. Furthermore, we characterized the effect of CCI-TBI on the stimulation of neuroinflammation within the PFC and NAc, comprising the reward pathway. Specifically, our studies revealed a sex-specific increase in 1) sensitivity to the rewarding efficacy of a subthreshold doses of cocaine interpreted from significantly higher cocaine CPP shifts, 2) the activation and phagocytosis of microglia observed by the positive expression of neuronal synaptic proteins in microglia sorted using flow cytometry, 3) increase in permeability of the blood-brain barrier indicated by discontinuous and depleted expression of tight junction proteins that line microvasculature isolated from reward nuclei, 4) decreased neuronal complexity, arborization, and spine density quantified from Golgi-cox stained NAc neurons, 5) changes in expression of genes related to the dopamine system analyzed by qRT-PCR in only male mice injured during adolescence. Additionally, our results imply that high levels of female hormones can promote neuroprotection against increased sensitivity to the rewarding properties of cocaine following injury, associated with decreased neuroinflammatory profiles after TBI in adolescent females. The studies herein aimed to elucidate underlying neuropathological outcomes following TBI in the reward circuitry that could be contributing to increased risk of addiction-like behavior observed clinically. Our findings suggest that TBI during adolescence may enhance the abuse liability of cocaine in adulthood and vulnerability to the rewarding effects of cocaine could be higher as a result of brain injury. Key pathological findings in the NAc such as activated microglial phagocytosis, BBB changes, reduced neuronal complexity, and changes in dopamine gene expression in areas of the reward pathways support the notion that neuroinflammation may contribute to how the rewarding efficacy of cocaine are affected post-TBI during adolescence. The ultimate goal of this research is to 1) advance TBI and SUD literature with the potential to increase awareness and help health care providers inform TBI patients about the increased risk for SUDs, and 2) to translate identified correlated mechanisms into novel targeted therapies that would provide a launching point for the treatment of patients with TBI-related SUD. / Biomedical Sciences

The purpose of this study was to uncover the unique and devastating consequences of untreated head injuries in a population that self-monitors their return to play after an injury. The secondary purpose was to identify the general perceptions of head injuries in the action sports culture and the themes that are common challenges for action sport athletes during their TBI rehabilitation in order to examine the coping skills that were used during their attempt to return to their sport. Seven athletes were interviewed. The sports represented were snowboarding, BMX racing, BMX freestyle, and motocross. The interviews assessed the following concepts: injury experience, symptoms, recovery, perception of the sport, return to sport, personality factors, and perception of head injuries. The interviews were transcribed and coded by the researcher in order to identify common themes and perceptions. The results indicated that the high frequency of injuries in action sports contributes partially to the perception of head injuries. It is a part of the culture to ignore injuries and push through pain. While the athletes have found success with this method in the past, it takes personal experience to convince them that head injuries should not be treated in the same manner. Since many of the athletes were unaware of their exact medical diagnosis, the severity of their injuries were established by how much their symptoms affected their day-to-day life. Physical symptoms were the most commonly reported, but psychological symptoms had a greater affect on the participants' day-to-day life. Generally, the participants who returned to play had higher levels of self-efficacy and self-awareness than the athletes who were not able to return. However, it is unclear from the study if the athletes had high self-efficacy because they were able to return, or if they were able to return because of their pre-injury characteristics. There was also a general consensus among the participants that more support and awareness about brain injuries were needed in their sport. / Kinesiology

Traumatic brain injury, hereon referred to as TBI, can be simply defined as a disruption to normal brain function as a result of an outside force to the head. TBI contributes to one third of all injury related deaths in the United States, and treatment strategies for TBI are supportive. Although primary and secondary mechanisms of injury have been clearly identified, the heterogeneous and intertwined pathophysiology of TBI is not fully understood. Primary injury results from the impact itself and causes immediate damage. However, secondary mechanisms of injury in TBI, such as oxidative stress and inflammation, are points at which intervention may reduce neuropathology. Trials taking advantage of the antioxidant and anti-inflammatory properties of several agents have had little clinical success, while the use of targeted therapeutics in TBI is relatively unexplored. Evidence suggests that reactive oxygen species (ROS) propagate blood-brain barrier (BBB) hyperpermeability and exacerbate inflammation following TBI. In the studies presented herein, we tested the hypothesis that targeted detoxification of ROS may improve the pathological outcomes using the controlled cortical impact mouse model of TBI. Following TBI, endothelial activation results in a time dependent increase in vascular expression of ICAM-1, an endothelial activation and cell adhesion molecule, as was observed by immunohistochemistry and immunofluorescence staining of isolated cortical microvessels. We conjugated catalase, an antioxidant enzyme, to anti-ICAM-1 antibodies and administered the conjugate intravenously to 8-week-old C57BL/6J mice at 30 minutes after moderate controlled cortical impact TBI. Results indicate that catalase targeted to ICAM-1 reduces markers of oxidative stress including levels of hydrogen peroxide and 3-nitrotyrosine detected in the cortex ipsilateral to the area of injury. Anti-ICAM-1/catalase also preserved BBB permeability based on two assays of barrier permeability to the plasma protein fibrinogen and small fluorescent tracer sodium fluorescein. Following TBI, mice receiving the conjugate exhibited attenuated neuropathological indices for astrocyte and microglia activation as well as cortical neuronal loss compared to controls. For each of these endpoints, anti-ICAM-1/catalase was found to be more effective than anti-ICAM-1 antibodies or catalase administered alone. An extensive study of microglia by two-photon microscopy of ex vivo brain segments from CX3CR1-GFP mice revealed that anti-ICAM-1/catalase prevented the transition of microglia to an activated phenotype after TBI. Finally, anti-ICAM-1/catalase offered functional improvement in Rotarod and elevated zero maze performance compared to controls at acute and chronic time points, respectively. Collectively, these findings demonstrate the use of a targeted antioxidant enzyme to interfere with oxidative stress mechanisms acutely in TBI. The results demonstrate histological and functional benefit of anti-ICAM-1/catalase administration and provide a proof-of-concept approach to improve acute TBI management that may also be applicable to other neuroinflammatory conditions. / Biomedical Sciences

Traumatic brain injury (TBI) is a major cause of disability worldwide. No effective treatment is currently available to restore function to the injured brain. After injury, massive neuronal death occurs which can result in long-lasting cognitive dysfunction. Following immediate mechanical damage, a series of secondary effects of injury occur including evolving neuronal damage, inflammation, astrocyte reactivation, blood brain barrier disruption and other physiological effects. Additionally, neural stem cell (NSC) proliferation has been observed following TBI, suggestive of an endogenous attempt to repair the brain. Stimulating proliferation of NSCs is a promising strategy to facilitate recovery following TBI, but the mechanisms underlying NSC proliferation remain unknown. In this work, we have addressed the following specific aims. In the first aim, we determined the role of Shh signaling in NSC proliferation after TBI. Using a fluid percussion model of TBI and conditional transgenic animal models, we investigated the role astrocytes play in NSC proliferation. Using a Sonic hedgehog (Shh) pathway inhibitor, we found that NSC proliferation after TBI relies on Shh signaling. In the second aim, we determined the role of astrocyte activation in NSC proliferation after TBI. Using transgenic tools, we determined that astrocytes are a major cellular source of Shh and that astrocyte-specific deletion of Shh inhibited NSC proliferation. This indicates that NSC proliferation relies on Shh signaling and that astrocytes represent the key cellular source. In the final aim, we sought to define the functional requirement of Nestin in NSC proliferation. Recent studies in our lab found that Nestin, an intermediate filament protein predominantly expressed by NSCs, played a role in Shh signaling in the setting of medulloblastoma cells. Here, we found that knockdown of Nestin impaired Shh signal transduction and Shh-driven proliferation in NSCs. Further, we generated a new mouse model allowing conditional deletion of Nestin in NSCs to determine whether Nestin played a similar role a non-neoplastic setting. Conditional deletion of Nestin in NSCs abolished the proliferation of hippocampal NSCs after TBI. These findings reveal the critical role of Nestin in Shh signaling and proliferation in NSCs following TBI. Our studies elucidate the cellular and molecular basis for NSC proliferation after TBI, which pave the road for development of therapeutic approaches to treat TBI by augmenting endogenous NSC regeneration. / Cancer Biology & Genetics

Mild blast-induced traumatic brain injury (bTBI) is a modality of injury that has been of major concern considering a large number of military personnel exposed to the blast wave from explosives. bTBI results from the propagation of high-pressure static blast forces and their subsequent energy transmission within brain tissue. Current literature presents a neuro-centric approach to the role of mitochondria dynamics dysfunction in bTBI; however, changes in astrocyte-specific mitochondrial dynamics have not been characterized. As a result of fission and fusion, the mitochondrial structure is constantly altering shape to respond to physiological stimuli or stress insults by adapting structure and function, which are intimately connected. Dysregulation of the protein regulator of mitochondrial fission, DRP1, and upregulation in the phosphorylation of DRP1 at the serine 616 site is reported to play a crucial role in astrocytic mitochondrial dysfunction, favoring fission over fusion post-TBI. Astrocytic mitochondria are starting to be recognized to play an essential role in overall brain metabolism, synaptic transmission, and neuron protection. Mitochondria are vulnerable to injury insults leading to the worsening of mitochondrial fission and increased mitochondrial fragmentation. In this study, a combination of in vitro and in vivo bTBI models were used to examine the effect of blast on astrocytic mitochondrial dynamics. Acute differential remodeling of the astrocytic mitochondrial network was observed, accompanied by an acute (4hr) and sub-acute (7 days) activation of the GTP-protein DRP1. Further, results showed a time-dependent reactive astrocyte phenotype transition in the rat hippocampus. This discovery can lead to innovative therapeutics targets to help prevent secondary injury cascades that involve mitochondria dysfunction. / Doctor of Philosophy / Blast-induced traumatic brain injury (bTBI) is a modality of injury that has become prominent considering a large number of military personnel exposed to a blast wave caused by explosives. Blast injury results from the energy transmission of the blast wave to the brain. Within the brain, there are specialized cells, called astrocytes, that help maintain a healthy environment. This work investigates the role that astrocytes play during the injury recovery process. Within the astrocytes, there are organelles called mitochondria, that help maintain the energy for the cell. The number and function of mitochondria can change in response to the brain injury. They can increase in number by a process called fission and they can decrease in number by a process called fusion. These events effect the function of the mitochondria. Researchers have methods that can identify changes in the number and function of the mitochondria. In this work, astrocyte mitochondrial dynamics were examined and compared using models of bTBI. We found significant changes in the mitochondria of astrocytes, which could lead to an unhealthy environment in the brain. This discovery can lead to new treatments for patients that may improve their quality of life following bTBI.

Across almost all types of neurological pathophysiology, inflammation and corresponding breakdown of the Blood Brain Barrier (BBB) are hallmarks of injury/disease progression. In fact, BBB disruption can occur early during neuropathophysiological development, in many cases even before neurological and cognitive impairments become apparent. Whether as an early causative factor, a side effect, or both as it pertains to neurological injury/disease, BBB breakdown and dysfunction represents a novel and under investigated target for therapeutic development, especially for neurological pathologies with unmet therapeutic needs. Toward this goal, the endocannabinoid system (ECS) has emerged as a promising biological target for drug discovery efforts. Particularly, the Cannabinoid 2 Receptor (CB2R) has been proposed as a druggable target due to its anti-inflammatory effects and since it is not associated with the neurological side effect profile representative of Cannabinoid 1 Receptor (CB1R) drugs. Interestingly, neuroinflammatory conditions promote upregulation of CB2R on brain microvascular endothelial cells (BMVECs) suggesting a possible role toward resolution of inflammation in this cell type. Moreover, previous research has shown promising effects of CB2R agonists on cerebrovascular function, although these effects cannot be directly attributed to endothelial CB2R. The central hypothesis of this research is that endothelial CB2R activation confers effects which are vascular protective and that promote BBB repair, (irrespective of the effects of CB2R in other central nervous system (CNS) cell types). To address this hypothesis, endothelial CB2R expression dynamics were assessed following experimental Traumatic Brain Injury (TBI) followed by a series of assays to assess the therapeutic potential of a novel chromenopyrazole based CB2R agonist, PM289. Results of these experiments demonstrated upregulation of CNR2, the gene which encodes CB2R, following in vivo experimental TBI and in vitro cytokine induced inflammation. Moreover, PM289 exhibited robust CB2R-dependent therapeutic potential by partially restoring TNFa-induced physical barrier disruption, attenuating TNFa-induced ICAM1 upregulation, and promoting rapid monolayer repair following electrolytic wound. Mechanistically, these effects may be explained via CB2R-dependent inhibition of NFkB/P65 signaling. Overall, these results are supportive of the notion that CB2R in BMVECs could aid in vascular protection and promote BBB function in the context of neuroinflammation. Future studies are warranted to understand the in vivo therapeutic efficacy of PM289 in a variety of injury/disease models. Additionally, alternative cell signaling mechanisms should be considered including a comprehensive examination of potential interplay between ECS components and candidates that fall under the umbrella of the endocannabionoidome (ECBome). / Biomedical Sciences