Blast-induced traumatic brain injury (bTBI) is a significant health concern for military personnel, causing potential long-term neurological consequences. Given the unique and heterogeneous genetic makeup of the human population, the acute responses and evolving sequelae from blast exposure are difficult to predict. To address these challenges, murine models are invaluable in the study of bTBI, as they allow researchers to carefully control exposure parameters while examining physiological changes across genetic, cellular, and whole-organism levels over time. In this study, we investigated the role of genetic diversity in bTBI by examining six common mouse strains-A/J, 129S1/SvImJ, NOD/ShiLtJ, NZO/HILtJ, C57BL/6J, and CAST/EiJ-and their possible differential response to blast overpressure. We assessed immediate neurological impairment, respiratory symptoms, lethality thresholds, and gross pathological and histological changes following blast overpressure exposure across these strains. We observed significant strain-dependent differences across all the measured outcomes. In particular, C57BL/6J mice exhibited the longest normalized righting times and highest incidence of subdural hematomas. Notably, the strains used as models of type I/II diabetes (NZO/HILtJ and NOD/ShiLtJ) showed the highest resilience to blast-induced lethality. In comparison, the CAST/EiJ strain was the most susceptible to immediate apnea and had the lowest lethality threshold. The NZO/HILtJ mice showed the highest incidence of pulmonary bleeding. Our findings highlight the substantial influence of the genetic background on the bTBI outcomes in mice, even with highly controlled physical exposure conditions. This comprehensive characterization of strain-dependent responses to bTBI provides a foundation for investigating the genetic influences on blast injury outcomes and developing more targeted preventative and/or therapeutic strategies for bTBI.

The typical motor symptoms of Parkinson's disease (PD) are caused by selective loss of dopaminergic neurons in the substantia nigra (SN). Although conventional pharmacotherapies can temporarily alleviate symptoms, no approved therapies exist to slow or reverse the underlying pathologic processes. To address this gap, cell transplantation therapies are being pursued; however, restoration of the original neuroanatomical circuit is not a goal of traditional ectopic intra-striatal neuronal transplantations. To address this, we developed an implantable tissue engineered nigrostriatal pathway (TE-NSP) containing human stem cell derived dopaminergic neurons with pre-formed long-projecting axonal bundles to replace the circuitry connecting the SN and the striatum. However, a challenge in the translation of tissue engineered medical products is the need for storage and transportation following biofabrication to enable point-of-care surgical implantation. Herein, we describe successful creation of TE-NSPs using a commercially-available human iPSC-derived dopaminergic neuronal source and describe growth characteristics for a range of neuronal and axonal densities. We also established protocols for the biopreservation of these fully-grown, human neuron-based TE-NSPs under hypothermic (4 °C) conditions for up to 2 days. Subsequent assessment of neuronal viability and maintenance of axonal-tract architecture out to 12-weeks in vitro demonstrate that short-term hibernation of TE-NSPs consisting of 55,000 neurons did not reduce neuronal viability, axonal health, structural integrity, or survival in physioxia conditions (5 % O2) when compared to non-biopreserved controls. The long-term survival of biopreserved TE-NSPs in vitro provides proof-of-concept supporting hypothermic storage during transportation for future safety and efficacy studies. STATEMENT OF SIGNIFICANCE: Degeneration of dopaminergic neurons and their axonal projections comprising the nigrostriatal pathway leads to Parkinson's disease, the second most common neurodegenerative disease globally. To address shortcomings of current cell transplantation therapies that primarily focus on ectopic cell transplantation, we have generated an engineered microtissue with pre-formed axon tracts using human neurons. Our tissue engineered nigrostriatal pathways (TE-NSPs) are implantable engineered microtissue that structurally and functionally resemble the native nigrostriatal pathway. For future translational applications, we established their preservation under hypothermic conditions, facilitating storage and transportation to the clinical setting. The study provides proof-of-concept that biopreserved 'living neural tissue' survives under hypothermic and simulated physioxic conditions, demonstrating their translational potential in the human brain.

Early diagnosis of traumatic brain injury (TBI) is crucial to guide treatment and improve recovery. Yet neuroimaging—the current gold standard for detection—cannot detect subtle biochemical changes and is insufficient to diagnose many TBI cases. Consequently, there is an urgent need for early, brain-associated biomarkers of TBI. Following injury, brain cells release cell-free DNA (cfDNA) into peripheral blood due to neurovascular disruption. DNA methylation patterns, which inform tissue specificity, could serve as biomarkers for TBI severity and progression. To test this hypothesis, we analyzed cfDNA from peripheral blood of swine models of TBI having injuries of differing severity and type: mild and moderate contusional, and mild and moderate rotational injuries. Using whole genome bisulfite sequencing, we identified distinct brain-associated cfDNA epigenetic signatures of affected brain regions, and the underlying biological processes associated with each injury type and severity. In these brain regions, proton magnetic resonance spectroscopic imaging (1H MRSI) independently confirmed changes in biomarkers of brain health and function (choline and N-acetylaspartate metabolites). Droplet digital PCR validated that cfDNA differentially methylated regions (DMRs) tracked TBI progression. Our findings provide evidence that brain-associated cfDNA methylome signatures, combined with 1H MRSI, can characterize the neurobiological processes at sites of TBI in a preclinical model. These results support further investigation of cfDNA as a non-invasive biomarker for TBI detection and monitoring, pending validation in larger and clinically diverse cohorts.

Purpose: Traumatic brain injury (TBI) affects 69 million people annually and is most frequently caused by rapid rotational acceleration of the head. Modeling rotational acceleration injuries in pigs can employ biomechanical parameters scaled from humans, allowing researchers to answer basic and translational questions about the influence of injury kinematics on outcomes. However, precisely describing head kinematics during rotational acceleration injuries is imperative to understand the relationships between biomechanical parameters, pathology, and neurological outcomes. Methods: Using an established model of rapid rotational acceleration, we examined kinematic transfer efficiency by assessing how closely the motion of the subject's head matched the motion of the rotational device. Pigs were submitted to head rotation in the sagittal plane at either a moderate or a high target velocity. Kinematics were recorded with transducers and high frame rate videography, which was quantified manually and with the deep learning neural network, DeepLabCut. The rotational device was programmed to generate peak angular velocities ranging from 85.8-108.1 rad/s. Results: The kinematic coupling of the peak angular velocities between the head and transducer-mounted injury device was 95.30 ± 3.41% during moderate velocity TBIs and 93.09 ± 8.08% during high velocity TBI. Angular velocity exhibited strong matching between the head and injury device while angular acceleration exhibited fair-to-strong matching, depending on the kinematic term. These angular velocity and acceleration levels exceeded clinical injury thresholds from the literature based on appropriate mass scaling. Conclusions: The high degree of kinematic matching between injury device and head in both moderate and high velocity TBIs suggests a high kinematic transfer efficiency within the target range of angular velocities. This validation study provide critical insights into the fidelity of large animal rotational acceleration injury by enhancing our understanding of force transmission and head kinematics, leading to more accurate scaling and representation of human TBI events.

Closed-head traumatic brain injury (TBI) generally results in diffusely distributed neuropathology. However, factors influencing the micro-scale distribution of this neuropathology remain unknown. Because neurovasculature exhibits different mechanical properties from the surrounding parenchyma, we postulated that these material transitions would increase the likelihood of biophysical damage and resultant neuropathology. Accordingly, we measured the incidence of neuronal plasmalemmal damage in perivascular domains using an established porcine model of single or repetitive closed-head rotational acceleration induced TBI. We found a significant increase in the proportion of regions containing permeabilized neurons in the cortex, thalamus, and midbrain following a single head rotation. We next employed an unbiased sampling methodology that mapped the distribution of vasculature (location, size, and directionality) and permeabilized neurons to determine if neuronal permeability increased based on proximity to vasculature. We identified an increase in the number of permeabilized neurons and a significant decrease in the number of larger (> 100 μm) vessels in the midbrain after repetitive TBI separated by 3 days. Furthermore, we identified that perivascular areas exhibited an increased density of neuronal permeability relative to more distal, extraperivascular spaces but only when excluding blood vessels that had no associations with permeabilized neurons. Neuronal permeability distribution was not affected by vessel size. These data suggest that vascular changes and neuronal damage may be unique consequences based on injury biomechanics, timing between repetitive injuries, and neuroanatomical features. While neuroanatomical features such as distance to the nearest vessel contribute to the distribution of neuronal mechanoporation, our findings indicate that perivascular proximity is a secondary, not primary, factor influencing this distribution. More research is needed to identify other factors that affect the susceptibility and distribution of neuronal plasmalemmal pathology.

Severe peripheral nerve injuries result in incomplete recovery despite neurorrhaphy. Microsurgical suturing is technically demanding, time-intensive, and may produce variable fascicular alignment. Nerve Tape is an FDA-approved sutureless device enabling rapid, reproducible nerve coaptation. This study compared Nerve Tape with epineurial microsuturing following common peroneal nerve transection in Yucatan minipigs. Over 12 months, both groups demonstrated reinnervation of the tibialis anterior and extensor digitorum brevis, representing proximal and distal muscle targets, respectively. Tibialis anterior recovery was comparable between groups. In contrast, Nerve Tape produced greater distal motor recovery in the extensor digitorum brevis, with approximately 1.8-fold higher compound muscle action potential amplitude and 74.3% versus 46.0% recovery compared with microsutures. Compound nerve action potential amplitudes recorded from the motor branch of the deep peroneal nerve were also greater with Nerve Tape, whereas conduction velocities were comparable. Histological analysis demonstrated preserved fascicular architecture distal to the repair in both groups, with no significant differences in axon count, mean myelinated axon diameter, or g-ratio in the terminal common peroneal nerve or its distal motor branch. Clinical use was demonstrated in a representative case with progressive recovery. Nerve Tape supported durable structural and functional recovery and improved distal motor reinnervation compared with microsuturing.

Understanding how mechanical forces translate into progressive neural pathology remains a central challenge in mitigating, diagnosing, and treating traumatic brain injury (TBI), a major public health concern that affects millions annually and lacks reliable prognostic biomarkers. To address this, we combined virtual brain twins constructed using finite element methods with diffusion imaging to investigate spatiotemporal tissue alterations in two porcine TBI models: non-impact rotational TBI and controlled cortical impact (CCI). In the rotational model, subacute abnormalities were observed in the brainstem and subcortical regions, with quantitative anisotropy showing a moderate correlation with peak strain. In contrast, CCI produced delayed, but widespread, diffusion abnormalities, particularly in mean diffusivity, that were associated with cortical deformation over time. Axonal injury metrics derived from tractography-based structural connectivity showed strain-related trends in the rotational model but not in CCI, suggesting that diffuse axonal injury from inertial loading may be more directly influenced by mechanical factors, whereas axonal damage in focal impact may be more influenced by secondary, non-mechanical processes, such as neuroinflammation. These findings support a mechanistic association between simulated brain deformation and evolving imaging biomarkers, indicating that different TBI mechanisms (diffuse versus focal) are associated with distinct spatiotemporal diffusion signatures. Our study provides a translational framework for interpreting neuroimaging through the lens of biomechanics and highlights the potential of virtual brain twins to inform mechanism-specific diagnosis, monitoring, and therapeutic development in TBI.

Omega-3 polyunsaturated fatty acids (ω3 PUFAs) are critical structural components of neuronal membranes, yet the molecular specificity of their incorporation within neural cells remains incompletely defined. We integrated untargeted and targeted lipidomics with lipid ontology analysis and coarse-grained membrane simulations to characterize remodeling in primary rat cortical neurons and neuron-astrocyte co-cultures following supplementation with docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), or docosapentaenoic acid (DPA). Each ω3 PUFA produced a distinct lipidomic signature. DHA showed the most consistent incorporation, selectively enriching phosphatidylethanolamine (PE) species-particularly PE(18:0/22:6) and PE(18:1/22:6)-associated with membrane curvature and organelle organization. Ontology analysis linked DHA supplementation to intrinsic curvature-related membrane features, and membrane simulations demonstrated enhanced collective bilayer bending without substantial changes in overall membrane thickness. EPA preferentially increased EPA-containing PE species without elevating DHA levels, whereas DPA effects were variable and culture-dependent, indicating selective metabolic handling of individual ω3 species. Differences between neurons and neuron-astrocyte co-cultures underscore the importance of cellular context in ω3-driven remodeling. By resolving ω3 incorporation at molecular species resolution and linking compositional changes to predicted membrane behavior, this study provides a structural framework for understanding how dietary ω3 fatty acids may influence neuronal membrane organization and cellular resilience.

Given the heterogeneity of traumatic brain injury (TBI), the development of a therapeutic strategy has been difficult despite decades of research. To develop an accurate classification system to guide individualized treatment, new protein biomarkers of TBI have been studied. We explored if different subtypes of TBI have unique biomarker profiles and histological findings using four pig models of TBI: moderate rotational injury (100-110 r/s), mild rotational injury (85-95 r/s), moderate contusional injury (8-9 mm), and mild contusional injury (6-7 mm). Among these groups, we identified unique profile of plasma neurofilament light (NFL) and glial fibrillary acidic protein (GFAP): whereas moderate contusion animals had early peak of NFL (2-3 days) and GFAP (1 day), mild contusion animals had delayed peak of NFL (8 days) and GFAP (3 days). Diffusion tensor imaging analysis found reduced fractional anisotropy in corona radiata for contusional injured animals but rotational injured animals showed no significant changes compared to control animals. Histological analysis showed prominent vascular inflammation and axonal injury in the pericontusional cortex in contusional injured animals. In rotational injured animals, prominent axonal injury was found in perivascular white matter. Future studies for mechanistic underpinning of biomarker changes are needed to establish therapeutic targets, predict severity of injury, and determine clinical trial enrollment and therapeutic response.

BACKGROUNDTraumatic brain injury (TBI) induces cognitive deficits driven by neuroinflammation and cerebral edema. The commonly used atypical antipsychotic, quetiapine (QTP), has been recently shown to improve post-TBI outcomes. We hypothesized that QTP would thereby improve animal learning and memory 2 weeks after severe TBI.METHODSCD1 male mice (n = 35) underwent severe TBI (controlled cortical impact, injury, I) or sham craniotomy (S), followed by BID saline (P, placebo) or QTP (10 or 20 mg/kg, IP) for 2 weeks. Animals underwent Morris Water Maze (MWM) exercises to gauge spatial learning and memory. The distance and time required for swimming animals to reach the platform area (Zone 5, Z5) located in quadrant 1 (Zone 1, Z1) was calculated from digital video recordings analyzed using Ethovision software. Animal bodyweights were recorded daily and on Day 14, injured cerebral hemispheres were procured for edema determination (wet-to-dry ratio). Intergroup differences were evaluated with ANOVA/Bonferroni correction (p< 0.05).RESULTSOn Day 14, animal weight loss recovery was lowest in I + P compared to I + QTP20 and I + QTP10 (p≤ 0.01 for either). Cerebral edema was greatest in I + P, and only significantly decreased in I + QTP20 (p< 0.05). Both QTP doses similarly improved spatial learning by significantly reducing latency time and travel distance to target zones (p< 0.05). In probe memory trials, only I + QTP20 and not I + QTP10 significantly favored animal reaching or crossing into target zones (p< 0.05).CONCLUSIONPost-TBI QTP reduces brain edema and improves spatial learning and memory with a potential dose dependence impact benefiting memory up to 14 days. These data suggest an unanticipated QTP benefit following brain injury that should be specifically explored.

Although human females appear be at a higher risk of concussion and suffer worse outcomes than males, underlying mechanisms remain unclear. With increasing recognition that damage to white matter axons is a key pathologic substrate of concussion, we used a clinically relevant swine model of concussion to explore potential sex differences in the extent of axonal pathologies. At 24 h post-injury, female swine displayed a greater number of swollen axonal profiles and more widespread loss of axonal sodium channels than males. Axon degeneration for both sexes appeared to be related to individual axon architecture, reflected by a selective loss of small caliber axons after concussion. However, female brains had a higher percentage of small caliber axons, leading to more extensive axon loss after injury compared to males. Accordingly, sexual dimorphism in axonal size is associated with more extensive axonal pathology in females after concussion, which may contribute to worse outcomes.

Traumatic brain injury (TBI) is a global health problem affecting millions of individuals annually, potentially resulting in persistent neuropathology, chronic neurological deficits, and death. However, TBI not only affects neural tissue, but also affects the peripheral immune system's homeostasis and physiology. TBI disrupts the balanced signaling between the brain and the peripheral organs, resulting in immunodysregulation and increasing infection susceptibility. Indeed, secondary infections following TBI worsen neurological outcomes and are a major source of mortality and morbidity. Despite the compelling link between the damaged brain and peripheral immune functionality, little is known about how injury severity affects the peripheral immune system in closed-head diffuse TBI, the most common clinical presentation including all concussions. Therefore, we characterized peripheral blood mononuclear cells (PBMCs) and plasma changes over time and across injury severity using an established large-animal TBI model of closed-head, non-impact diffuse rotational acceleration in pigs. Across all timepoints and injury levels, we did not detect any changes to plasma cytokine concentrations. However, changes to the PBMCs were detectable and much more robust. We observed the concentration and physiology of circulating PBMCs changed in an injury severity-dependent manner, with most cellular changes occurring within the first 10 days following a high rotational velocity injury. Here, we report changes in the concentrations of myeloid and T cells, changes in PBMC composition, and changes in phagocytic clearance over time. Together, these data suggest that following a diffuse brain injury in a clinically relevant large-animal TBI model, the immune system exhibits perturbations that are detectable into the subacute timeframe. These findings invite future investigations into therapeutic interventions targeting peripheral immunity and the potential for peripheral blood cellular characterization as a diagnostic tool.

BACKGROUND:Early but not late tranexamic acid (TXA) after TBI preserves blood-brain-barrier integrity, but it is unclear if and how dose timing affects cognitive recovery beyond hours postinjury. We hypothesized that early (1 hour post-TBI) but not late (24 hours post-TBI) TXA administration improves cognitive recovery for 14 days.METHODS:CD1 male mice (n = 25) were randomized to severe TBI (injury [I], by controlled cortical impact) or sham craniotomy (S) followed by intravenous saline at 1 hour (placebo [P1]) or 30 mg/kg TXA at 1 hour (TXA1) or 24 hours (TXA24). Daily body weights, Garcia Neurological Test scores, brain/lung water content, and Morris water maze exercises quantifying swimming traffic in the platform quadrant (zone [Z] 1) and platform area (Z5) were recorded for up to 14 days.RESULTS:Among injured groups, I-TXA1 demonstrated fastest weight gain for 14 days and only I-TXA1 showed rapid (day 1) normalization of Garcia Neurological Test ( p = 0.01 vs. I-P1, I-TXA24). In cumulative spatial trials, compared with I-TXA1, I-TXA24 hindered learning (distance to Z5 and % time in Z1, p < 0.05). Compared with I-TXA1, I-TXA24 showed poorer memory with less Z5 time (0.51 vs. 0.16 seconds, p < 0.01) and Z5 crossing frequency. Unexpectedly, TXA in uninjured animals (S-TXA1) displayed faster weight gain but inferior learning and memory.CONCLUSION:Early TXA appears beneficial for cognitive and behavioral outcomes following TBI, although administration 24 hours postinjury consistently impairs cognitive recovery. Tranexamic acid in sham animals may lead to adverse effects on cognition.

Parkinson's disease is characterized by motor deficits emerging from insufficient dopamine in the striatum after degeneration of dopaminergic neurons and their long-projecting axons comprising the nigrostriatal pathway. To address this, a tissue-engineered nigrostriatal pathway (TE-NSP) featuring a tubular hydrogel with a collagen/laminin core that encases aggregated dopaminergic neurons and their axonal tracts is developed. This engineered microtissue can be implanted to replace neurons and axons with fidelity to the lost pathway and thus may provide dopamine according to feedback from host circuitry. While TE-NSPs have traditionally been fabricated with agarose, here a hyaluronic acid (HA) hydrogel is utilized to have a more bioactive encasement while expanding control over physical and biochemical properties. Using rat ventral midbrain neurons, it is found that TE-NSPs exhibited improved neurite growth with HA relative to agarose, with no differences in electrically-evoked dopamine release. When transplanted, HA hydrogels reduced average host neuron loss and inflammation around the implant compared to agarose, and TE-NSP neurons and axonal tracts survived for at least 2 weeks to structurally emulate the lost pathway. This study represents an innovative use of HA hydrogels for neuroregenerative medicine and enables future studies expanding the control and functionality of TE-NSPs.

Traumatic brain injury (TBI) is a major contributor to morbidity and mortality in the United States as several million people visit the emergency department every year due to TBI exposures. Unfortunately, there is still no consensus on the pathology underlying mild TBI, the most common severity sub-type of TBI. Previous preclinical and post-mortem human studies have detailed the presence of diffuse axonal injury following TBI, suggesting that white matter pathology is the predominant pathology of diffuse brain injury. However, the inertial loading produced by TBI results in strain fields in both gray and white matter. In order to further characterize gray matter pathology in mild TBI, our lab used a pig model (n = 25) of closed-head rotational acceleration-induced TBI to evaluate blood-brain barrier disruptions, neurodegeneration, astrogliosis, and microglial reactivity in the cerebral cortex out to 1 year post-injury. Immunohistochemical staining revealed the presence of a hyper-ramified microglial phenotype-more branches, junctions, endpoints, and longer summed process length-at 30 days post injury (DPI) out to 1 year post injury in the cingulate gyrus (p < 0.05), and at acute and subacute timepoints in the inferior temporal gyrus (p < 0.05). Interestingly, we did not find neuronal loss or astroglial reactivity paired with these chronic microglia changes. However, we observed an increase in fibrinogen reactivity-a measure of blood-brain barrier disruption-predominately in the gray matter at 3 DPI (p = 0.0003) which resolved to sham levels by 7 DPI out to chronic timepoints. Future studies should employ gene expression assays, neuroimaging, and behavioral assays to elucidate the effects of these hyper-ramified microglia, particularly related to neuroplasticity and responses to potential subsequent insults. Further understanding of the brain's inflammatory activity after mild TBI will hopefully provide understanding of pathophysiology that translates to clinical treatment for TBI.

Closed-head traumatic brain injury (TBI) is induced by rapid motion of the head, resulting in diffuse strain fields throughout the brain. The injury mechanism(s), loading thresholds, and neuroanatomical distribution of affected cells remain poorly understood, especially in the gyrencephalic brain. We utilized a porcine model to explore the relationships between rapid head rotational acceleration-deceleration loading and immediate alterations in plasmalemmal permeability within cerebral cortex, sub-cortical white matter, and hippocampus. To assess plasmalemmal compromise, Lucifer yellow (LY), a small cell-impermeant dye, was delivered intraventricularly and diffused throughout the parenchyma prior to injury in animals euthanized at 15-min post-injury; other animals (not receiving LY) were survived to 8-h or 7-days. Plasmalemmal permeability preferentially occurred in neuronal somata and dendrites, but rarely in white matter axons. The burden of LY + neurons increased based on head rotational kinematics, specifically maximum angular velocity, and was exacerbated by repeated TBI. In the cortex, LY + cells were prominent in both the medial and lateral gyri. Neuronal membrane permeability was observed within the hippocampus and entorhinal cortex, including morphological changes such as beading in dendrites. These changes correlated with reduced fiber volleys and synaptic current alterations at later timepoints in the hippocampus. Further histological observations found decreased NeuN immunoreactivity, increased mitochondrial fission, and caspase pathway activation in both LY + and LY – cells, suggesting the presence of multiple injury phenotypes. This exploratory study suggests relationships between plasmalemmal disruptions in neuronal somata and dendrites within cortical and hippocampal gray matter as a primary response in closed-head rotational TBI and sets the stage for future, traditional hypothesis-testing experiments.

BACKGROUND Early but not late tranexamic acid (TXA) after TBI preserves blood-brain-barrier integrity, but it is unclear if and how dose timing affects cognitive recovery beyond hours postinjury. We hypothesized that early (1 hour post-TBI) but not late (24 hours post-TBI) TXA administration improves cognitive recovery for 14 days. METHODS CD1 male mice (n = 25) were randomized to severe TBI (injury [I], by controlled cortical impact) or sham craniotomy (S) followed by intravenous saline at 1 hour (placebo [P1]) or 30 mg/kg TXA at 1 hour (TXA1) or 24 hours (TXA24). Daily body weights, Garcia Neurological Test scores, brain/lung water content, and Morris water maze exercises quantifying swimming traffic in the platform quadrant (zone [Z] 1) and platform area (Z5) were recorded for up to 14 days. RESULTS Among injured groups, I-TXA1 demonstrated fastest weight gain for 14 days and only I-TXA1 showed rapid (day 1) normalization of Garcia Neurological Test ( p = 0.01 vs. I-P1, I-TXA24). In cumulative spatial trials, compared with I-TXA1, I-TXA24 hindered learning (distance to Z5 and % time in Z1, p < 0.05). Compared with I-TXA1, I-TXA24 showed poorer memory with less Z5 time (0.51 vs. 0.16 seconds, p < 0.01) and Z5 crossing frequency. Unexpectedly, TXA in uninjured animals (S-TXA1) displayed faster weight gain but inferior learning and memory. CONCLUSION Early TXA appears beneficial for cognitive and behavioral outcomes following TBI, although administration 24 hours postinjury consistently impairs cognitive recovery. Tranexamic acid in sham animals may lead to adverse effects on cognition.