Age-at-Injury Determines the Extent of Long-Term Neuropathology and Microgliosis After a Diffuse Brain Injury in Male Rats (original) (raw)
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Molecular correlates of age-specific responses to traumatic brain injury in mice
Experimental gerontology, 2006
Aged traumatic brain injury (TBI) patients suffer higher rates of mortality and disability than younger patients. Cognitive problems common to TBI patients are associated with damage to the hippocampus, a central locus of learning and memory. To investigate the molecular mechanisms of age-related vulnerability to brain injury in a mouse model of TBI, we studied the effects of TBI on hippocampal gene expression in young and aged mice. Young and aged male C57Bl/6 mice were subjected to sham injury or TBI and sacrificed 24 h post-injury. We used laser capture microdissection to obtain pure populations of neurons from the CA1, CA3, and dentate gyrus subfields of the hippocampus. We compared injury-induced gene expression in hippocampal neurons of young and aged mice using quantitative ribonuclease protection assay analysis of linearly amplified mRNA from laser captured neurons. Both increased age and TBI were associated with increased expression of neuroprotective (brain-derived neurotrophic factor), pro-inflammatory (interleukin-1b), and proapoptotic (caspase-3) genes in mouse hippocampal neurons. Our data support previous reports that suggested the CA3 subregion is highly susceptible to fluid percussion TBI and that age-related changes in gene expression are one potential mechanism of increased vulnerability of the aged brain to TBI.
Developmental Neuroscience, 2016
Development and aging are influenced by external factors with the potential to impact health throughout the life span. Traumatic brain injury (TBI) can initiate and sustain a lifetime of physical and mental health symptoms. Over 1.7 million TBIs occur annually in the USA alone, with epidemiology suggesting a higher incidence for young age groups. Additionally, increasing life spans mean more years to age with TBI. While there is ongoing research of experimental pediatric and adult TBI, few studies to date have incorporated animal models of pediatric, adolescent, and adult TBI to understand the role of age at injury across the life span. Here, we explore repeated behavioral performance between rats exposed to diffuse TBI at five different ages. Our aim was to follow neurological morbidities across the rodent life span with respect to age at injury. A single cohort of male Sprague-Dawley rats (n = 69) was received at postnatal day (PND) 10. Subgroups of this cohort (n = 11-12/group) w...
Age-Dependent Responses Following Traumatic Brain Injury
Traumatic Brain Injury - Pathobiology, Advanced Diagnostics and Acute Management
Traumatic brain injury (TBI) is a growing health concern worldwide that affects a broad range of the population. As TBI is the leading cause of disability and mortality in children, several preclinical models have been developed using rodents at a variety of different ages; however, key brain maturation events are overlooked that leave some age groups more or less vulnerable to injury. Thus, there has been a large emphasis on producing relevant animal models to elucidate molecular pathways that could be of therapeutic potential to help limit neuronal injury and improve behavioral outcome. TBI involves a host of different biochemical events, including disruption of the cerebral vasculature and breakdown of the blood-brain barrier (BBB) that exacerbates secondary injuries. A better understanding of age-related mechanism(s) underlying brain injury will aid in establishing more effective treatment strategies aimed at improving restoration and preventing further neuronal loss. This review looks at studies that focus on modeling the adolescent population and highlights the importance of individualized aged therapeutics to TBI.
Effects of advanced age upon astrocyte-specific responses to acute traumatic brain injury in mice
2019
BackgroundOlder-age individuals are at the highest risk for disability from a traumatic brain injury (TBI). Astrocytes are the most numerous glia in the brain, necessary for brain function, yet there is little known about unique responses of astrocytes in the aged-brain following TBI.MethodsOur approach examined astrocytes in young adult, 4-month-old, versus aged, 18-month-old mice, at 1, 3, and 7 days post-TBI. We selected these time points to span the critical period in the transition from acute injury to presumably irreversible tissue damage and disability. Two approaches were used to define the astrocyte contribution to TBI by age interaction: 1) tissue histology and morphological phenotyping, and 2) transcriptomics on enriched astrocytes from the injured brain.ResultsAging was found to have a profound effect on the TBI-induced loss of homeostatic astrocyte function needed for maintaining water transport and edema – namely, aquaporin-4. The loss of homoeostatic responses was cou...
Journal of Neurotrauma, 2012
Traumatic brain injury (TBI) affects many infants and children, and results in enduring motor and cognitive impairments with accompanying changes in white matter tracts, yet few experimental studies in rodent juvenile models of TBI (jTBI) have examined the timeline and nature of these deficits, histologically and functionally. We used a single controlled cortical impact (CCI) injury to the parietal cortex of rats at post-natal day (P) 17 to evaluate behavioral alterations, injury volume, and morphological and molecular changes in gray and white matter, with accompanying measures of electrophysiological function. At 60 days post-injury (dpi), we found that jTBI animals displayed behavioral deficits in foot-fault and rotarod tests, along with a left turn bias throughout their early developmental stages and into adulthood. In addition, anxiety-like behaviors on the zero maze emerged in jTBI animals at 60 dpi. The final lesion constituted only *3% of brain volume, and morphological tissue changes were evaluated using MRI, as well as immunohistochemistry for neuronal nuclei (NeuN), myelin basic protein (MBP), neurofilament-200 (NF200), and oligodendrocytes (CNPase). White matter morphological changes were associated with a global increase in MBP immunostaining and reduced compound action potential amplitudes at 60 dpi. These results suggest that brain injury early in life can induce long-term white matter dysfunction, occurring in parallel with the delayed development and persistence of behavioral deficits, thus modeling clinical and longitudinal TBI observations.
Neuroscience, 1998
Clinical studies have demonstrated that patients sustain prolonged behavioral deficits following traumatic brain injury, in some cases culminating in the cognitive and histopathological hallmarks of Alzheimer's disease. However, few studies have examined the long-term consequences of experimental traumatic brain injury. In the present study, anesthetized male Sprague-Dawley rats (n=185) were subjected to severe lateral fluid-percussion brain injury (n=115) or sham injury (n=70) and evaluated up to one year post-injury for cognitive and neurological deficits and histopathological changes. Compared with sham-injured controls, brain-injured animals showed a spatial learning impairment that persisted up to one year post-injury. In addition, deficits in specific neurologic motor function tasks also persisted up to one year post-injury. Immunohistochemistry using multiple antibodies to the amyloid precursor protein and/or amyloid precursor protein-like proteins revealed novel axonal degeneration in the striatum, corpus callosum and injured cortex up to one year post-injury and in the thalamus up to six months post-injury. Histologic evaluation of injured brains demonstrated a progressive expansion of the cortical cavity, enlargement of the lateral ventricles, deformation of the hippocampus, and thalamic calcifications. Taken together, these findings indicate that experimental traumatic brain injury can cause long-term cognitive and neurologic motor dysfunction accompanied by continuing neurodegeneration. 1998 IBRO. Published by Elsevier Science Ltd.
Apoptotic neurodegeneration following trauma is markedly enhanced in the immature brain
Annals of Neurology, 1999
Age dependency of apoptotic neurodegeneration was studied in the developing rat brain after percussion head trauma. In 7-day-old rats, mechanical trauma, applied by means of a weight drop device, was shown to trigger widespread cell death in the hemisphere ipsilateral to the trauma site, which first appeared at 6 hours, peaked at 24 hours, and subsided by 5 days after trauma. Ultrastructurally, degenerating neurons displayed features consistent with apoptosis. A decrease of bcl-2 in conjunction with an increase of c-jun mRNA levels, which were evident at 1 hour after trauma and were accompanied by elevation of CPP 32-like proteolytic activity and oligonucleosomes in vulnerable brain regions, confirmed the apoptotic nature of this process. Severity of trauma-triggered apoptosis in the brains of 3-to 30-day-old rats was age dependent, was highest in 3-and 7-day-old animals, and demonstrated a subsequent rapid decline. Adjusting the mechanical force in accordance with age-specific brain weights revealed a similar vulnerability profile. Thus, apoptotic neurodegeneration contributes in an age-dependent fashion to neuropathological outcome after head trauma, with the immature brain being exceedingly vulnerable. These results help explain unfavorable outcomes of very young pediatric head trauma patients and imply that, in this group, an antiapoptotic regimen may constitute a successful neuroprotective approach.
Repeat Mild Traumatic Brain Injury in Adolescent Rats Increases Subsequent β-Amyloid Pathogenesis
Journal of Neurotrauma, 2017
Single moderate-to-severe traumatic brain injuries (TBIs) may increase subsequent risk for neurodegenerative disease by facilitating b-amyloid (Ab) deposition. However, the chronic effects on Ab pathogenesis of repetitive mild TBIs (rTBI), which are common in adolescents and young adults, remain uncertain. We examined the effects of rTBI sustained during adolescence on subsequent deposition of Ab pathology in a transgenic APP/PS1 rat model. Transgenic rats received sham or four individual mild TBIs (rTBIs) separated by either 24-or 72-h intervals at post-natal day 35 (before Ab plaque deposition). Animals were euthanized at 12 months of age and underwent immunohistochemical analyses of Ab plaque deposition. Significantly greater hippocampal Ab plaque deposition was observed after rTBI separated by 24 h relative to rTBI separated by 72 h or sham injuries. These increases in hippocampal Ab plaque load were driven by increases in both plaque number and size. Similar, though less-pronounced, effects were observed in extrahippocampal regions. Increases in Ab plaque deposition were observed both ipsilaterally and contralaterally to the injury site and in both males and females. rTBIs sustained in adolescence can increase subsequent deposition of Ab pathology, and these effects are critically dependent on interinjury interval.
Journal of neurotrauma, 2015
Although accumulating evidence suggests that repeated mild TBI (rmTBI) may cause long-term cognitive dysfunction in adults, whether rmTBI causes similar deficits in the immature brain is unknown. Here we used an experimental model of rmTBI in immature brain to answer this question. Postnatal day (PND) 18 rats were subjected to either one, two or three mild TBIs (mTBI) or an equivalent number of sham insults 24h apart. After one or two mTBIs or sham insults histology was evaluated at 7d. After three mTBIs or sham insults motor (d1-5), cognitive (d11-92) and histological (d21-92) outcome was evaluated. At 7d silver degeneration staining revealed axonal argyrophilia in the external capsule and corpus callosum after a single mTBI, with a second impact increasing axonal injury. Iba-1 immunohistochemistry showed amoeboid shaped microglia within the amygdalae bilaterally after mTBI proportional to the degree of axonal injury. After three mTBI, there were no differences in beam balance, Mor...
Developmental Neuroscience, 2010
weight method and diffusion-weighted MRI. Blood-brain barrier permeability, as measured by the Evans blue dye technique, peaked at 20 min after trauma in all age groups, with a second peak found only in adult animals at 24 h after injury. Phosphorus MR spectroscopy showed no significant changes in the brain energy metabolism of immature rats with moderate DTBI, in contrast to significant decreases previously identified in adult animals.