Increased jun immunoreactivity in an in vitro model of mammalian spinal neuron physical injury

Animal studies in spinal cord injury: a systematic review of methylprednisolone

The objective of this study was to examine whether animal studies can reliably be used to determine the usefulness of methylprednisolone (MP) and other treatments for acute spinal cord injury (SCI) in humans. This was achieved by performing a systematic review of animal studies on the effects of MP administration on the functional outcome of acute SCI. Data were extracted from the published articles relating to: outcome; MP dosing regimen; species/strain; number of animals; methodological quality; type of injury induction; use of anaesthesia; functional scale used; and duration of follow-up. Subgroup analyses were performed, based on species or strain, injury method, MP dosing regimen, functional outcome measured, and methodological quality. Sixty-two studies were included, which involved a wide variety of animal species and strains. Overall, beneficial effects of MP administration were obtained in 34% of the studies, no effects in 58%, and mixed results in 8%. The results were inconsistent both among and within species, even when attempts were made to detect any patterns in the results through subgroup analyses. The results of this study demonstrate the barriers to the accurate prediction from animal studies of the effectiveness of MP in the treatment of acute SCI in humans. This underscores the need for the development and implementation of validated testing methods.

Linking impact to cellular and molecular sequelae of CNS injury: modeling in vivo complexity with in vitro simplicity

Traumatic brain injury (TBI) represents one of most common disorders to the central nervous system (CNS). Despite significant efforts, though, an effective clinical treatment for TBI is not yet available. The complexity of human TBI is modeled with a broad group of experimental models, with each model matching some aspect of the human condition. In the past 15 years, these in vivo models were complemented with a group of in vitro models, with these in vitro models allowing investigators to more precisely identify the mechanism(s) of TBI, the different intracellular events that occur in acute period following injury, and the possible treatment of this injury in vitro. In this paper, we review the available in vitro models to study TBI, discuss their biomechanical basis for human TBI, and review the findings from these in vitro models. Finally, we synthesize the current knowledge and point out possible future directions for this group of models, especially in the effort toward developing new therapies for the traumatically brain injured patient.

A Molecular Basis for the Efficacy of Magnesium Treatment following Traumatic Brain Injury in Rats

Magnesium ions have been shown to be a promising treatment for brain lesions caused by traumatic brain injury (TBI), as well as for the associated acute neurodegeneration and progressive functional deficits. This study investigated the effects of magnesium on the expression of the cell death/survival related proteins following TBI. Male Sprague-Dawley (SD) rats (n = 66, 280-320 g body weight) were subjected to sham surgery alone (n = 14), or to the surgery followed by a lateral fluid percussion brain injury of moderate severity (n = 52, 2.4-2.7 atm). The injured rats were randomly treated with an intravenous bolus of magnesium chloride (n = 26, 125 micromol) or saline vehicle (n = 26). The coronal brain sections were quantitatively analyzed for cell apoptosis and the expression of p53-related proteins, Bcl-2, cyclin D1 and PCNA at 1, 2, and 4 days post-injury by immunohistochemistry or in situ hybridization. Tissue damage was observed primarily in the ipsilateral cortex of the injured region with the induction of apoptosis and p53 mRNA level at 2 days after TBI. The expression of p53 and responding proteins (p21(WAF1/CIP1), Mdm2 and Bax) showed a temporal pattern similar to the apoptotic events in the time course experiments. They were induced in the early time points of days 1-2, decreasing by day 4 after TBI. In contrast, the expression of the cell survival related proteins - Bcl-2, cyclin D1, and PCNA - was most significant at day 4 post-injury, when the rate of apoptosis decreased. Magnesium treatment resulted in a reduction in apoptosis and expression of p53-related proteins. However, it had only a slight additive effect on the expression of the survival related proteins in the same time-course. These results provide a molecular basis for the efficiency of magnesium in treating TBI-induced tissue damage.

Contact call-driven zenk mRNA expression in the brain of the budgerigar (Melopsittacus undulatus)

Contact call-driven zenk (zif268, egr1, NGF1A, Krox 24) mRNA expression was mapped with in situ hybridization histochemistry in a vocal learning parrot, the budgerigar (M. undulatus). Relative to controls, call stimulation induced high zenk mRNA expression in all auditory areas including those closely associated with the vocal system within the anterior forebrain (Brauth et al. (2001) J. Comp. Neurol. 432, 481; (2002) Learn. Memory 9, 76). Thus there is a high correspondence between the distributions of neurons exhibiting contact call-driven zenk protein and mRNA expression in budgerigars. Field L2a, an area reported previously to express only perinucleolar zenk protein localization (Brauth et al. (2002) Learn. Memory 9, 76) also showed zenk mRNA expression.

Activated/effector CD4+ T cells exacerbate acute damage in the central nervous system following traumatic injury

CD4(+) helper T cells (Th) have been demonstrated to participate in the chronic phase of traumatic injury repair in the central nervous system (CNS). Here, we show that CD4(+) T cells can also contribute to the severity of the acute phase of CNS traumatic injury. We compared the area of tissue damage and the level of cellular apoptosis in aseptic cerebral injury (ACI) sites of C57BL/6 wild type and RAG1(-/-) immunodeficient mice. We demonstrate that ACI is attenuated in RAG1(-/-) mice compared to C57BL/6 animals. Adoptive transfer of CD4(+)CD62L(low)CD44(high) activated/effector T cells 24 h prior to ACI into RAG1(-/-) mice resulted in a significantly enhanced acute ACI that was comparable to ACI in the C57BL/6 animals. Adoptive transfer of CD4(+)CD62L(high)CD44(low) naive/non-activated T cells did not increase ACI in the brains of RAG1(-/-) mice. T cell inhibitory agents, cyclosporin A (CsA) and FK506, significantly decreased ACI-induced acute damage in C57BL/6 mice. These results suggest a previously undescribed role for activated/effector CD4(+) T cells in exacerbating ACI-induced acute damage in the CNS and raise a novel possibility for acute treatment of sterile traumatic brain injury.

Apoptotic neurodegeneration following trauma is markedly enhanced in the immature brain

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.