Hemorrhagic progression of a contusion after traumatic brain injury: a review

The magnitude of damage to cerebral tissues following head trauma is determined by the primary injury, caused by the kinetic energy delivered at the time of impact, plus numerous secondary injury responses that almost inevitably worsen the primary injury. When head trauma results in a cerebral contusion, the hemorrhagic lesion often progresses during the first several hours after impact, either expanding or developing new, non-contiguous hemorrhagic lesions, a phenomenon termed hemorrhagic progression of a contusion (HPC). Because a hemorrhagic contusion marks tissues with essentially total unrecoverable loss of function, and because blood is one of the most toxic substances to which the brain can be exposed, HPC is one of the most severe types of secondary injury encountered following traumatic brain injury (TBI). Historically, HPC has been attributed to continued bleeding of microvessels fractured at the time of primary injury. This concept has given rise to the notion that continued bleeding might be due to overt or latent coagulopathy, prompting attempts to normalize coagulation with agents such as recombinant factor VIIa. Recently, a novel mechanism was postulated to account for HPC that involves delayed, progressive microvascular failure initiated by the impact. Here we review the topic of HPC, we examine data relevant to the concept of a coagulopathy, and we detail emerging data elucidating the mechanism of progressive microvascular failure that predisposes to HPC after head trauma.     

Cleaved-tau: a biomarker of neuronal damage after traumatic brain injury

Previous studies from our laboratory indicate that traumatic brain injury (TBI) in humans results in proteolysis of neuronally-localized, intracellular microtubule associated protein (MAP)-tau to produce cleaved tau (C-tau). The present study evaluated the utility of C-tau to function as a biomarker of neuronal injury and as a biomarker for evaluating neuroprotectant drug efficacy in a controlled cortical impact model of rat TBI. Brain C-tau was determined in rats subjected to controlled cortical impact-induced mild, moderate or severe levels of TBI. A significant severity-dependent increase in C-tau levels was observed in the cortex and hippocampus (1.5-8-fold) of TBI rats compared to shams 72 h after impact. C-tau rat brain and serum time course was determined by measuring levels at 0.25, 6, 24, 48, 72 and 168 h after TBI. A significant time-dependent increase in C-tau levels was observed in ipsilateral cortex (5-16-fold) and hippocampus (2-40-fold) compared to sham animals. C-tau levels increased as early as 6 h after TBI with peak C-tau levels observed 168 h after injury. Elevated brain C-tau levels were associated with TBI-induced tissue loss, which was histologically determined. The effect of cyclosporin-A (CsA), previously demonstrated to be neuroprotective in rat TBI, on brain C-tau levels was examined. CsA (20 mg/kg i.p., 15 min and 24 h after TBI) significantly attenuated the TBI-induced increase in hippocampal C-tau levels observed in vehicle-treated animals confirming CsA's neuroprotectant effect. CsA treatment also lowered ipsilateral cortical C-tau levels, although it did not reach statistical significance. CsA's neuroprotectant effect was confirmed utilizing histologic measures of TBI-induced tissue loss. In addition, serum C-tau levels were significantly increased 6 h after TBI but not at later time points. These results suggest that C-tau is a reliable, quantitative biomarker for evaluating TBI-induced neuronal injury and a potential biomarker of neuroprotectant drug efficacy in the rat TBI model. Serum data suggests that C-tau levels are dependent both on a compromised blood-brain barrier as well as release of TBI biomarkers from the brain, which has implications for the study of human serum TBI biomarkers.     

Disruption of Bax protein prevents neuronal cell death but produces cognitive impairment in mice following traumatic brain injury

Apoptosis contributes to delayed neuronal cell death in traumatic brain injury (TBI). To investigate if Bax plays a role in neuronal cell death and functional outcome after TBI, Bax gene disrupted (null) mice and wild-type (WT) controls were subjected to the controlled cortical impact (CCI) model of TBI. Motor function in WT and Bax null mice was evaluated using the round beam balance and the wire grip test on days 0-5. Spatial memory was assessed using a Morris Water Maze adopted for mice on days 14-18 post-injury. For histopathological analysis, animals were sacrificed 24 h and 21 days post-injury. In all three behavioral tests, the sham and TBI-injured Bax null mice performed significantly worse than their WT sham and TBI-injured counterparts. However, Bax null mice exhibited a higher percentage of surviving neurons in the CA1 and CA3 regions of hippocampus measured at 21 days post-injury. At 24 h after trauma, Bax null mice had fewer TUNEL positive cells in the CA1 and dentate regions of hippocampus as compared to WT mice, suggesting that deletion of the Bax gene ameliorates hippocampal cell death after TBI. Sham-operated Bax null mice had significantly greater brain volume as compared to WT mice. Thus, it is possible that Bax deficiency in the transgenic mice produces developmental behavioral effects, perhaps due to Bax's role in regulating cell death during development.     

Effect of inducible nitric oxide synthase on cerebral blood flow after experimental traumatic brain injury in mice

Inducible nitric oxide synthase (iNOS) has been suggested to play a complex role in the response to central nervous system insults such as traumatic brain injury (TBI) and cerebral ischemia. In the current study, we quantified maps of regional cerebral blood flow (CBF) using an arterial spin-labeling magnetic resonance imaging (MRI) technique, at 24 and 72 h after experimental TBI in iNOS knockout (KO) and wild-type (WT) mice. Our hypothesis was that iNOS would contribute to the level of CBF at 72 h after experimental TBI in mice. Comparing anatomical brain regions of interest (ROIs) at 24-h post controlled cortical impact (CCI), there were significant reductions in CBF in the hemisphere, cortex, and contusion-rich area of the cortex of injured animals versus naive, regardless of genotype. Regional assessment of CBF at 72 h after injury demonstrated that recovery of CBF was reduced in the ipsilateral hippocampus, thalamus, and amygdala/piriform cortex in iNOS KO versus WT mice by 26%, 15%, and 21%, respectively; this attenuated recovery was restricted to structures outside the contusion. These regions with reduced CBF in iNOS KO mice represented ROIs where CBF in the WT was either numerically or statistically greater than that seen in respective WT naive, suggesting a contribution of iNOS to delayed posttraumatic hyperemia. However, pixel analysis denoted that the contribution of iNOS to CBF at 72 h was not limited to hyperemia flows. In conclusion, iNOS plays a role in the recovery of CBF after CCI in mice. Questions remain if this effect represents a homeostatic component of CBF recovery, pathologic vasodilatation linked to inflammation, or NO-mediated facilitation of angiogenesis.     

The effect of brain temperature on hemoglobin extravasation after traumatic brain injury

OBJECT: Although the benefits of posttraumatic hypothermia have been reported in experimental studies, the potential for therapeutic hypothermia to increase intracerebral hemorrhage remains a clinical concern. The purpose of this study was to quantify the amount of extravasated hemoglobin after traumatic brain injury (TBI) and to assess the changes in intracerebral hemoglobin concentrations under posttraumatic hypothermic and hyperthermic conditions. METHODS: Intubated and anesthetized rats were subjected to fluid-percussion injury (FPI). In the first experiment, rats were divided into moderate (1.8-2.2 atm) and severe (2.4-2.7 atm) TBI groups. In the second experiment, the effects of 3 hours of posttraumatic hypothermia (33 or 30 degrees C), hyperthermia (39 degrees C), or normothermia (37 degrees C) on hemoglobin levels following moderate trauma were assessed. The rats were perfused with saline at 24 hours postinjury, and then the traumatized and contralateral hemispheres, including the cerebellum, were dissected from whole brain. The hemoglobin level in each brain was quantified using a spectrophotometric hemoglobin assay. The results of these assays indicate that moderate and severe FPI induce increased levels of hemoglobin in the ipsilateral hemisphere (p < 0.0001). After severe TBI, the hemoglobin concentration was also significantly increased in the contralateral hemisphere (p < 0.05) and cerebellum (p < 0.005). Posttraumatic hypothermia (30 degrees C) attenuated hemoglobin levels (p < 0.005) in the ipsilateral hemisphere, whereas hyperthermia had a marked adverse effect on the hemoglobin concentration in the contralateral hemisphere (p < 0.05) and cerebellum (p < 0.005). CONCLUSIONS: Injury severity is an important determinant of the degree of hemoglobin extravasation after TBI. Posttraumatic hypothermia reduced hemoglobin extravasation, whereas hyperthermia increased hemoglobin levels compared with normothermia. These findings are consistent with previous data reporting that posttraumatic temperature manipulations alter the cerebrovascular and inflammatory consequences of TBI.     

Brain death after severe traumatic brain injury: the role of systemic secondary brain insults

Secondary brain insults predominantly due to hypotension are frequent among patients with fatal traumatic brain injury. We assessed the correlation between different systemic secondary brain insults and brain death in 404 patients admitted to our intensive care unit (ICU) after severe traumatic brain injury. We collated data on hypoxemia and hypotension prior to as well as the occurrence of hypoxemia, hypotension, shock, anemia, hyperglycemia, and hyperthermia within the first 24 hours after ICU admission. We also considered both the presence of extracranial injuries and the category of traumatic brain injury using computerized tomography. The 59 patients (14.6%) who developed brain death, were significantly older than patients without a fatal neurological outcome (46.1 +/- 22 vs 29.5 +/- 14.9 years; P < .0001). Intracranial mass lesions, whether surgically evacuated were more frequent among brain-dead patients. The systemic secondary brain insults significantly associated with brain death were hypoxemia, hypotension, shock, anemia, and hyperglycemia within the first 24 hours after ICU admission. After multivariate analysis, the factors that independently predicted brain death were the occurrence of shock (odds ratio [OR], 6.74; 95% confidence interval [CI], 2.85-15.84; P = .001) and older age (OR, 1.05; 95% CI, 1.03-1.07; P = .003). In conclusion, early shock seems to be the major systemic secondary brain insult associated with brain death in patients with severe traumatic brain injury. Prevention of or correction of shock might help to either decrease the occurrence of a fatal neurological outcome or in brain-dead patients to preserve organs in better condition for procurement.     

Prehospital HBOC-201 after traumatic brain injury and hemorrhagic shock in swine

BACKGROUND: Data are limited on the actions of hemoglobin based oxygen carriers (HBOCs) after traumatic brain injury (TBI). This study evaluates neurotoxicity, vasoactivity, cardiac toxicity, and inflammatory activity of HBOC-201 (Biopure, Cambridge, Mass.) resuscitation in a TBI model. METHODS: Swine received TBI and hemorrhage. After 30 minutes, resuscitation was initiated with 10 mL/kg normal saline (NS), followed by either HBOC-201 (6 mL/kg, n = 10) or NS control (n = 10). Supplemental NS was administered to both groups to maintain mean arterial pressure (MAP) >60 mm Hg until 60 minutes, and to maintain cerebral perfusion pressure (CPP) >70 mm Hg from 60 to 300 minutes. The control group received mannitol (1 g/kg) and blood (10 mL/kg) at 90 minutes and half (n = 5) received CPP directed phenylephrine (PE) therapy after 120 minutes. Serum cytokines were measured with ELISA and coagulation was evaluated with thromboelastography. Brains were harvested for neuropathology. RESULTS: With HBOC administration, MAP, CPP, and brain tissue PO2 were restored within 30 minutes and maintained until 300 minutes. Clot strength and fibrin formation were maintained and 9/10 successfully extubated. In contrast, with control, MAP and brain tissue PO2 did not correct until 120 minutes, after mannitol, transfusion and 40% more crystalloid. Furthermore, without PE, CPP did not reach target and 0/5 could be extubated. Lactate, heart rate, cardiac output, mixed venous oxygenation, muscle oxygenation, serum cytokines, and histology did not differ between groups. CONCLUSIONS: After TBI, a single HBOC-201 bolus with minimal supplements provided rapid resuscitation, while maintaining CPP and improving brain oxygenation, without causing cardiac dysfunction, coagulopathy, cytokine release, or brain structural changes.     

Cell-specific upregulation of survivin after experimental traumatic brain injury in rats

In this study, we examined the expression and cellular localization of survivin and proliferating cell nuclear antigen (PCNA) after controlled cortical impact traumatic brain injury (TBI) in rats. There was a remarkable and sustained induction of survivin mRNA and protein in the ipsilateral cortex and hippocampus of rats after TBI, peaking at five days post injury. In contrast, both survivin mRNA and protein were virtually undetectable in craniotomy control animals. Concomitantly, expression of PCNA was also significantly enhanced in the ipsilateral cortex and hippocampus of these rats with similar temporal and spatial patterns. Immunohistochemistry revealed that survivin and PCNA were co-expressed in the same cells and had a focal distribution within the injured brain. Further analysis revealed a frequent co-localization of survivin and GFAP, an astrocytic marker, in both the ipsilateral cortex and hippocampus, while a much smaller subset of cells showed co-localization of survivin and NeuN, a mature neuronal marker. Neuronal localization of survivin was observed predominantly in the ipsilateral cortex and contralateral hippocampus after TBI. PCNA protein expression was detected in both astrocytes and neurons of the ipsilateral cortex and hippocampus after TBI. Collectively these data demonstrate that the anti-apoptotic protein survivin, previously characterized in cancer cells, is abundantly expressed in brain tissues of adult rats subjected to TBI. We found survivin expression in both astrocytes and a sub-set of neurons. In addition, the expression of survivin was co-incident with PCNA, a cell cycle protein. This suggests that survivin may be involved in regulation of neural cell proliferative responses after traumatic brain injury.     

Hypernatremia severity and the risk of death after traumatic brain injury

Purpose

To investigate the relationship between severity of hypernatremia and the risk of death for patients with traumatic brain injury (TBI) who have been admitted to the neurosurgical intensive care unit (NICU).

Methods

A total of 1044 patients with TBI were admitted to our NICU from January 2005 to January 2010. Of these patients, 881 were included in this study. Based on blood serum sodium level in the NICU the 881 patients were divided into four groups: 614 had normal serum sodium (Na < 150 mmol/L), 34 had mild hypernatremia (Na 150–<155 mmol/L), 66 had moderate hypernatremia (Na 155–160 mmol/L) and 167 had severe hypernatremia (Na ≥ 160 mmol/L).

Results

The mortality rates for the mild, moderate, and severe hypernatremia groups were 20.6%, 42.4%, and 86.8%, respectively; the mortality rate for the normal group was 2.0%. In multivariable analysis, mild, moderate, and severe hypernatremia were independent risk factors for mortality; compared with the normal group the odds ratios of mild, moderate, and severe hypernatremia were 9.50, 4.34, and 29.35, respectively.

Conclusions

Severe hypernatremia is an independent risk factor with extremely high odds ratio for death in patients with TBI who are admitted to the NICU.     

颅脑外伤后进展性脑损害的研究进展

颅脑外伤后进展性脑损害,包括脑出血、脑缺血、脑水肿,都是影响颅脑外伤预后的重要因素.本文复习文献,对颅脑外伤后进展性脑损害的发病率、发生机制、早期诊断方法、治疗和预后等相关问题的研究进展进行了综述.     

Severe brief pressure-controlled hemorrhagic shock after traumatic brain injury exacerbates functional deficits and long-term neuropathological damage in mice

Abstract Hypotension after traumatic brain injury (TBI) worsens outcome. We published the first report of TBI plus hemorrhagic shock (HS) in mice using a volume-controlled approach and noted increased neuronal death. To rigorously control blood pressure during HS, a pressure-controlled HS model is required. Our hypothesis was that a brief, severe period of pressure-controlled HS after TBI in mice will exacerbate functional deficits and neuropathology versus TBI or HS alone. C57BL6 male mice were randomized into four groups (n=10/group): sham, HS, controlled cortical impact (CCI), and CCI+HS. We used a pressure-controlled shock phase (mean arterial pressure [MAP]=25-27?mm Hg for 35?min) and its treatment after mild to moderate CCI including, a 90?min pre-hospital phase, during which lactated Ringer's solution was given to maintain MAP >70?mm Hg, and a hospital phase, when the shed blood was re-infused. On days 14-20, the mice were evaluated in the Morris water maze (MWM, hidden platform paradigm). On day 21, the lesion and hemispheric volumes were quantified. Neuropathology and hippocampal neuron counts (hematoxylin and eosin [H&E], Fluoro-Jade B, and NeuN) were evaluated in the mice (n=60) at 24?h, 7 days, or 21 days (n=5/group/time point). HS reduced MAP during the shock phase in the HS and CCI+HS groups (p<0.05). Fluid requirements during the pre-hospital phase were greatest in the CCI+HS group (p<0.05), and were increased in HS versus sham and CCI animals (p<0.05). MWM latency was increased on days 14 and 15 after CCI+HS (p<0.05). Swim speed and visible platform latency were impaired in the CCI+HS group (p<0.05). CCI+HS animals had increased contusion volume versus the CCI group (p<0.05). Hemispheric volume loss was increased 33.3% in the CCI+HS versus CCI group (p<0.05). CA1 cell loss was seen in CCI+HS and CCI animals at 24?h and 7 days (p<0.05). CA3 cell loss was seen after CCI+HS (p<0.05 at 24?h and 7 days). CA1 cell loss at 21 days was seen only in CCI+HS animals (p<0.05). Brief, severe, pressure-controlled HS after CCI produces robust functional deficits and exacerbates neuropathology versus CCI or HS alone.     

Neurogenesis after traumatic brain injury

With the hope of replacing neurons lost in traumatic brain injury (TBI), experimental models are being used to investigate TBI-induced neurogenesis. Although selectively vulnerable to TBI, the neurogenic hippocampus may have the unique ability to replace damaged neurons locally. Injury may also activate signaling pathways that induce neuroblasts from the subventricular zone to migrate to areas of focal cortical damage. Additionally, there is some evidence for local activation of latent neural progenitor cells in the injured neocortex itself. Each of these themes is discussed, with emphasis on the possibility of future therapeutic intervention.     

Apoptosis after traumatic brain injury

Apoptosis of neurons and glia contribute to the overall pathology of traumatic brain injury (TBI) in both humans and animals. In both head-injured humans and following experimental brain injury, apoptotic cells have been observed alongside degenerating cells exhibiting classic necrotic morphology. Neurons undergoing apoptosis have been identified within contusions in the acute port-traumatic period, and in regions remote from the site of impact in the days and weeks after trauma. Apoptotic oligodendrocytes and astrocytes have been observed within injured white matter tracts. We review the regional and temporal patterns of apoptosis following TBI and the possible mechanisms underlying trauma-induced apoptosis. While excitatory amino acids, increases in intracellular calcium, and free radicals can all cause cells to undergo apoptosis, in vitro studies have determined that neural cells can undergo apoptosis via many other pathways. It is generally accepted that a shift in the balance between pro- and anti-apoptotic protein factors towards the expression of proteins that promote death may be one mechanism underlying apoptotic cell death. The effect of TBI on regional cellular patterns of expression of survival promoting-proteins such as Bcl-2, Bcl-xL, and extracellular signal regulated kinases, and death-inducing proteins such as Bax, c-Jun N-terminal kinase, tumor-suppressor gene, p53, and the caspase family of proteases are reviewed. Finally, in light of pharmacologic strategies that have been devised to reduce the extent of apoptotic cell death in animal models of TBI, our review also considers whether apoptosis may serve a protective role in the injured brain.     

Coagulopathy after traumatic brain injury

Traumatic brain injury has long been associated with abnormal coagulation parameters, but the exact mechanisms underlying this phenomenon are poorly understood. Coagulopathy after traumatic brain injury includes hypercoagulable and hypocoagulable states that can lead to secondary injury by either the induction of microthrombosis or the progression of hemorrhagic brain lesions. Multiple hypotheses have been proposed to explain this phenomenon, including the release of tissue factor, disseminated intravascular coagulation, hyperfibrinolysis, hypoperfusion with protein C activation, and platelet dysfunction. The diagnosis and management of these complex patients are difficult given the lack of understanding of the underlying mechanisms. The goal of this review is to summarize the current knowledge regarding the mechanisms of coagulopathy after blunt traumatic brain injury. The current and emerging diagnostic tools, radiological findings, treatment options, and prognosis are discussed.     

Expression of intestinal CD40 after experimental traumatic brain injury in rats

Background

Nuclear factor kappa B (NF-κB) has been shown to be activated in the intestine after traumatic brain injury (TBI), and results in gastrointestinal mucosal injury. In addition, CD40 has a major role in the activation of NF-κB and is up-regulated in inflammatory bowel disease. However, we found no study in the literature investigating the intestinal expression of CD40 after TBI. Hence, we designed the current study to explore the intestinal expression pattern of CD40 after TBI in rats. We hypothesized that CD40 could mediate inflammation and ultimately contribute to acute intestinal mucosal injury after TBI.

Methods

We randomly divided rats into control and TBI groups at 3, 6, 12, 24, and 72 h, respectively. We assessed the expression of CD40 by quantitative real-time polymerase chain reaction, Western blotting, and immunohistochemical study, and detected the levels of tumor necrosis factor-α (TNF-α), intracellular adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecule-1 (VCAM-1) by enzyme-linked immunosorbent assay.

Results

The mRNA and protein levels of -CD40 increased by 3 and 6 h, peaked at 6 and 12 h, and remained elevated until 24 and 72 h post-injury, respectively. Levels of TNF-α, VCAM-1, and ICAM-1 also markedly increased in jejunum tissue after TBI. Interestingly, there was a positive relationship between the expression of CD40 and that of TNF-α, VCAM-1, and ICAM-1.

Conclusions

CD40 could be markedly elevated in intestine after TBI in rats, and it might have an important role in the pathogenesis of acute intestinal mucosal injury mediated by inflammatory response.     

Effects of magnesium sulfate on brain mitochondrial respiratory function in rats after experimental traumatic brain injury

Objective:To study the effects of magnesium sulfate on brain mitochondrial respiratory function in rats after experimental traumatic brain injury and the possible mechanism.Methods:The middle degree brain injury in rats was made by BIM-III multi-function impacting machine.The brain mitochondrial respiratory function was measured with oxygen electrode and the ultra-structural changes were observed with transmission electron microscope(TEM).Results:1.The brain mitochondrial respiratory stage III and respiration control rate reduced significantly in the untreated groups within 24 and 72 hours.But treated Group A showed certain degree of recovery of respiratiory function;treated Group B showed further improvement.2. Untreated Group,treated Groups A and B had different degrees of mitochondrial ultra-structural damage respectively, which could be attenuated after the treatment with magnesium sulfate.Conclusions:The mitochondrial respiratory function decreases significantly after traumatic brain injury.But it can be apparently improved after magnesium sulfate management along with the attenuated damage of mitochondria discovered by TEM.The longer course of treatment can obtain a better improvement of mitochondrial respiratory function.     

Neuroprotective effect of hypothermia on neuronal injury in diffuse traumatic brain injury coupled with hypoxia and hypotension.

It is well established in mechanical head trauma that posttraumatic secondary insults, such as hypoxia and hypotension exacerbate neuronal injury and lead to worse outcome. In this study, the neuroprotective effect of hypothermia on the reduction of supraventricular subcortical neuronal damage was evaluated using an impact-acceleration model of diffuse traumatic brain injury coupled with both moderate and severe periods of hypoxia and hypotension. A total of 135 adult male Sprague-Dawley rats (340-375 g) were divided into three experimental studies: (I) physiological evaluation (n = 36); (II) quantitative analysis of the effect of trauma coupled with moderate and severe hypotension on neuronal damage assessed at 4 (n = 39) and 24 h (n = 24); and (III) the neuroprotective effect of hypothermia following moderate secondary insult (n = 36). Induction of hypothermia occurred at 15 min postinjury, to a level of 30 degrees C for 60 min. At the designated time points (4 and 24 h), the animals were sacrificed via standard transcardial perfusion techniques for histological processing. Quantitative assessment of neuronal damage using routine H&E staining at 4 hours showed neuronal damage which correlated with the severity of secondary insult. Animals exposed to trauma alone had a mean number of damaged neurons of 7.61 +/- 3.08/high powered field (hpf) compared with a mean of 1.21 +/- 0.30/hpf in the sham operated group (p = 0.015). Animals exposed to trauma with 10 min of hypoxia and hypotension (THH-10) showed a statistically significant number of damaged neurons compared to the sham-operated animals (7.50 +/- 2.15 damaged neurons/hpf, p = 0.013), whereas, neuronal damage in animals undergoing trauma with a 30-min secondary insult of hypoxia and hypotension (THH-30) was markedly increased (100 +/- 30.20/hpf, p = 0.002). Statistical analysis showed no significant difference in neuronal damage in animals subjected to secondary insult alone. At 24 h, the evolution of neuronal damage in the trauma alone group (5.08 +/- 1.63/hpf) was relatively static; however, there was a remarkable increase in the neuronal damage of the THH-10 group (29.88 50 +/- 8.20/hpf). However, hypothermia provided nearly complete protection against secondary insults, and neuronal damage was equal to that of the trauma alone group (p = 0.42). The results of this study confirm that hypothermia provides remarkable protection against the adverse effects of neuronal damage exacerbated by secondary injury. This study also presents a new model of secondary insult, which can be used experimentally to further define the mechanism of increased vulnerability of the injured brain.     

Targeting cell death in vivo in experimental traumatic brain injury by a novel molecular probe

Traumatic brain injury (TBI) remains a frequent and major challenge in neurological and neurosurgical practice. Apoptosis may play a role in cerebral tissue damage induced by the traumatic insult, and thus its detection and inhibition may advance patient care. DDC (N,N'-didansyl-L-cystine) is a novel fluorescent probe for detection of apoptotic cells. We now report on the performance of DDC in experimental TBI. Closed head injury was induced in mice by weight-drop. DDC was administered intravenously in vivo. Two hours later, animals were sacrificed, and brain tissue was subjected to fluorescent microcopy, for assessment of DDC uptake, in correlation with histopathological assessment of apoptosis by TUNEL and caspase substrates, and also in correlation with the neurological deficits, as assessed by Neurological Severity Score (NSS). Selective uptake of DDC was observed at the primary site of injury, and also at remote sites. Uptake was at the cellular level, with accumulation of DDC in the cytoplasm. Cells manifesting DDC uptake were confirmed as apoptotic cells by detection of the characteristic apoptotic DNA fragmentation (positive TUNEL staining) and detection of activated caspases. The damaged region stained by DDC fluorescence correlated with the severity of neuronal deficits. Our study confirms the role of apoptosis in TBI, and proposes DDC as a useful tool for its selective targeting and detection in vivo. Such imaging of apoptosis, following future radiolabeling of DDC, may advance care for patients with head injury, by allowing real-time evaluation of the extent of tissue damage, assessment of novel therapeutic strategies, and optimization of treatment for the individual patient.