Nerve growth factor and doublecortin expression correlates with improved outcome in children with severe traumatic brain injury

Multifaceted Roles of Nerve Growth Factor: A Comprehensive Review with a Special Insight into Pediatric Perspectives

Nerve growth factor (NGF) is a neurotrophic peptide largely revealed for its ability to regulate the growth and survival of peripheral sensory, sympathetic, and central cholinergic neurons. The pro-survival and regenerative properties of neurotrophic factors propose a therapeutic potential in a wide range of brain diseases, and NGF, in particular, has appeared as an encouraging potential treatment. In this review, a summary of clinical studies regarding NGF and its therapeutic effects published to date, with a specific interest in the pediatric context, will be attempted. NGF has been studied in neurological disorders such as hypoxic-ischemic encephalopathy, traumatic brain injury, neurobehavioral and neurodevelopmental diseases, congenital malformations, cerebral infections, and in oncological and ocular diseases. The potential of NGF to support neuronal survival, repair, and plasticity in these contexts is highlighted. Emerging therapeutic strategies for NGF delivery, including intranasal administration as well as advanced nanotechnology-based methods, are discussed. These techniques aim to enhance NGF bioavailability and target specificity, optimizing therapeutic outcomes while minimizing systemic side effects. By synthesizing current research, this review underscores the promise and challenges of NGF-based therapies in pediatric neurology, advocating for continued innovation in delivery methods to fully harness NGF's therapeutic potential.

Therapeutic benefits of quercetin in traumatic brain injury model exposed to cigarette smoke

Scientific evidences reported the deleterious effect of cigarette smoking or passive smoking on brain health particularly cognitive functions, blood-brain barrier (BBB) permeability, up-regulation of inflammatory cascades, and depletion of the antioxidant system. These combined effects become more progressive in the events of stroke, traumatic brain injury (TBI), and many other neurodegenerative diseases. In the current study, we investigated the long-term administered therapeutic potential of quercetin in ameliorating the deleterious neurobiological consequences of chronic tobacco smoke exposure in TBI mice. After exposure to 21 days of cigarette smoke and treatment with 50 mg/kg of quercetin, C57BL/6 mice were challenged for the induction of TBI by the weight drop method. Subsequently, a battery of behavioral tests and immunohistochemical analyses revealed the beneficial effect of quercetin on the locomotive and cognitive function of TBI + smoked group mice (p < 0.05 vs control sham). Immunohistochemistry analysis (Nrf2, HO-1, NFkB, caspase 3) demonstrated a marked protection after 21 days of quercetin treatment in the chronic tobacco smoking group possibly by up-regulation of antioxidant pathways, and decreased apoptosis. In conclusion, our findings support the therapeutic effectiveness of quercetin in partly protecting the central neurological functions that become aberrantly impaired in combined habitual cigarette-smoking individuals impacted with TBI.

Traumatic MicroRNAs: Deconvolving the Signal After Severe Traumatic Brain Injury

History of traumatic brain injury (TBI) represents a significant risk factor for development of dementia and neurodegenerative disorders in later life. While histopathological sequelae and neurological diagnostics of TBI are well defined, the molecular events linking the post-TBI signaling and neurodegenerative cascades remain unknown. It is not only due to the brain's inaccessibility to direct molecular analysis but also due to the lack of well-defined and highly informative peripheral biomarkers. MicroRNAs (miRNAs) in blood are promising candidates to address this gap. Using integrative bioinformatics pipeline including miRNA:target identification, pathway enrichment, and protein-protein interactions analysis we identified set of genes, interacting proteins, and pathways that are connected to previously reported peripheral miRNAs, deregulated following severe traumatic brain injury (sTBI) in humans. This meta-analysis revealed a spectrum of genes closely related to critical biological processes, such as neuroregeneration including axon guidance and neurite outgrowth, neurotransmission, inflammation, proliferation, apoptosis, cell adhesion, and response to DNA damage. More importantly, we have identified molecular pathways associated with neurodegenerative conditions, including Alzheimer's and Parkinson's diseases, based on purely peripheral markers. The pathway signature after acute sTBI is similar to the one observed in chronic neurodegenerative conditions, which implicates a link between the post-sTBI signaling and neurodegeneration. Identified key hub interacting proteins represent a group of novel candidates for potential therapeutic targets or biomarkers.

The Roles of Neurotrophins in Traumatic Brain Injury

Neurotrophins are a collection of structurally and functionally related proteins. They play important roles in many aspects of neural development, survival, and plasticity. Traumatic brain injury (TBI) leads to different levels of central nervous tissue destruction and cellular repair through various compensatory mechanisms promoted by the injured brain. Many studies have shown that neurotrophins are key modulators of neuroinflammation, apoptosis, blood–brain barrier permeability, memory capacity, and neurite regeneration. The expression of neurotrophins following TBI is affected by the severity of injury, genetic polymorphism, and different post-traumatic time points. Emerging research is focused on the potential therapeutic applications of neurotrophins in managing TBI. We conducted a comprehensive review by organizing the studies that demonstrate the role of neurotrophins in the management of TBI.

Topical delivery of nerve growth factor for treatment of ocular and brain disorders

Neurotrophins are a family of proteins that support neuronal proliferation, survival, and differentiation in the central and peripheral nervous systems, and are regulators of neuronal plasticity. Nerve growth factor is one of the best-described neurotrophins and has advanced to clinical trials for treatment of ocular and brain diseases due to its trophic and regenerative properties. Prior trials over the past few decades have produced conflicting results, which have principally been ascribed to adverse effects of systemic nerve growth factor administration, together with poor penetrance of the blood-brain barrier that impairs drug delivery. Contrastingly, recent studies have revealed that topical ocular and intranasal nerve growth factor administration are safe and effective, suggesting that topical nerve growth factor delivery is a potential alternative to both systemic and invasive intracerebral delivery. The therapeutic effects of local nerve growth factor delivery have been extensively investigated for different ophthalmic diseases, including neurotrophic keratitis, glaucoma, retinitis pigmentosa, and dry eye disease. Further, promising pharmacologic effects were reported in an optic glioma model, which indicated that topically administered nerve growth factor diffused far beyond where it was topically applied. These findings support the therapeutic potential of delivering topical nerve growth factor preparations intranasally for acquired and degenerative brain disorders. Preliminary clinical findings in both traumatic and non-traumatic acquired brain injuries are encouraging, especially in pediatric patients, and clinical trials are ongoing. The present review will focus on the therapeutic effects of both ocular and intranasal nerve growth factor delivery for diseases of the brain and eye.

Modeling of post-traumatic epilepsy and experimental research aimed at its prevention

Research on the prevention of post-traumatic epilepsy (PTE) has seen remarkable advances regarding its physiopathology in recent years. From the search for biomarkers that might be used to indicate individual susceptibility to the development of new animal models and the investigation of new drugs, a great deal of knowledge has been amassed. Various groups have concentrated efforts in generating new animal models of traumatic brain injury (TBI) in an attempt to provide the means to further produce knowledge on the subject. Here we forward the hypothesis that restricting the search of biomarkers and of new drugs to prevent PTE by using only a limited set of TBI models might hamper the understanding of this relevant and yet not preventable medical condition.

Mouse nerve growth factor promotes neurological recovery in patients with acute intracerebral hemorrhage: A proof-of-concept study

BACKGROUND

ew drugs were confirmed to be effective in the treatments of neurological dysfunction caused by acute intracerebral hemorrhage (ICH). The present prospective clinical trial aims to evaluate the effect of mouse nerve growth factor (mNGF) on neurological function in patients with acute ICH.

METHODS

60 patients with acute spontaneous ICH were randomized to receive mNGF (mNGF group) and citicoline (control group) for 4 weeks within 24-72 h after onset, respectively. The primary outcome was difference in the neurological functional outcome at 3 months by the modified Rankin Scale score (mRS). The secondary outcomes were the changes in hematoma volume at 4 weeks and 3 months.

RESULTS

There were 55 patients receiving treatment (29 patients in the mNGF group, 26 patients in the control group). Among the patients, 46 patients finished the trial at 3 months; the odds of a shift towards death or dependence (mRS > 3) at 3 months in the mNGF group were lower than that in the control group with adjustment for age, sex, NIHSS at admission, and hematoma volume at admission (adjusted OR, 0.185; 95%CI, 0.059-0.582; P = 0.0039). The hematoma was gradually reduced in all 46 patients and absorbed after non-surgical treatment at 3 months. There was no significant difference in hematoma volume between the two groups. No serious adverse event was found.

CONCLUSIONS

The administration of mNGF and citicoline was well-tolerated in patients with acute ICH. mNGF was associated with improved neurological function and less disability in patients with ICH. Therefore, the quality of life of patients with ICH may be improved by mNGF.

TRIAL REGISTRATION

The trial is registered with the Chinese Clinical Trial Registry, number ChiCTR1800020258.

A Mechanistic Rationale for PDE-4 Inhibitors to Treat Residual Cognitive Deficits in Acquired Brain Injury

Patients with acquired brain injury (ABI) suffer from cognitive deficits that interfere significantly with their daily lives. These deficits are long-lasting and no treatment options are available. A better understanding of the mechanistic basis for these cognitive deficits is needed to develop novel treatments. Intracellular cyclic adenosine monophosphate (cAMP) levels are decreased in ABI. Herein, we focus on augmentation of cAMP by PDE4 inhibitors and the potentially synergistic mechanisms in traumatic brain injury. A major acute pathophysiological event in ABI is the breakdown of the blood-brain-barrier (BBB). Intracellular cAMP pathways are involved in the subsequent emergence of edema, inflammation and hyperexcitability. We propose that PDE4 inhibitors such as roflumilast can improve cognition by modulation of the activity in the cAMP-Phosphokinase A-Ras-related C3 botulinum toxin substrate (RAC1) inflammation pathway. In addition, PDE4 inhibitors can also directly enhance network plasticity and attenuate degenerative processes and cognitive dysfunction by increasing activity of the canonical cAMP/phosphokinase-A/cAMP Responsive Element Binding protein (cAMP/PKA/CREB) plasticity pathway. Doublecourtin and microtubule-associated protein 2 are generated following activation of the cAMP/PKA/CREB pathway and are decreased or even absent after injury. Both proteins are involved in neuronal plasticity and may consist of viable markers to track these processes. It is concluded that PDE4 inhibitors may consist of a novel class of drugs for the treatment of residual symptoms in ABI attenuating the pathophysiological consequences of a BBB breakdown by their anti-inflammatory actions via the cAMP/PKA/RAC1 pathway and by increasing synaptic plasticity via the cAMP/PKA/CREB pathway. Roflumilast improves cognition in young and elderly humans and would be an excellent candidate for a proof of concept study in ABI patients.

Association of Choroid Plexus Enlargement With Cognitive, Inflammatory, and Structural Phenotypes Across the Psychosis Spectrum

OBJECTIVE

The choroid plexus is an important physiological barrier and produces CSF and neurotrophic, angiogenic, and inflammatory factors involved in brain development. Choroid plexus abnormalities have been implicated in both schizophrenia and bipolar disorder. A previous choroid plexus transcriptomic analysis of schizophrenia identified an upregulation of immune and inflammatory genes that correlated with peripheral inflammatory markers. The purpose of this study was to examine choroid plexus volume in probands across the psychosis spectrum and in their first-degree and axis II cluster A relatives, as well as choroid plexus familiality and choroid plexus covariance with clinical, cognitive, brain, and peripheral marker measures.

METHODS

Choroid plexus volume was quantified (using FreeSurfer) in psychosis probands, their first-degree and axis II cluster A relatives, and healthy control subjects, organized by DSM-IV-TR diagnosis. Analyte, structural connectivity, and genotype data were collected from a subset of study subjects.

RESULTS

Choroid plexus volume was significantly larger in probands compared with first-degree relatives or healthy control subjects; first-degree relatives had intermediate enlargement compared with healthy control subjects; and total choroid plexus volume was significantly heritable. Larger volume was associated with worse cognition, smaller total gray matter and amygdala volume, larger lateral ventricle volume, and lower structural connectivity in probands. Associations between larger volume and higher levels of interleukin 6 in probands was also observed.

CONCLUSIONS

These findings suggest the involvement of the choroid plexus across the psychosis spectrum with a potential pathophysiological mechanism involving the neuroimmune axis, which functions in maintaining brain homeostasis and interacting with the peripheral immune and inflammatory system. The choroid plexus may be an important target in future research.

Sex hormones modulate pathogenic processes in experimental traumatic brain injury

Clinical and animal studies have revealed sex-specific differences in histopathological and neurological outcome after traumatic brain injury (TBI). The impact of perioperative administration of sex steroid inhibitors on TBI is still elusive. Here, we subjected male and female C57Bl/6N mice to the controlled cortical impact (CCI) model of TBI and applied pharmacological inhibitors of steroid hormone synthesis, that is, letrozole (LET, inhibiting estradiol synthesis by aromatase) and finasteride (FIN, inhibiting dihydrotestosterone synthesis by 5α-reductase), respectively, starting 72 h prior CCI, and continuing for a further 48 h after CCI. Initial gene expression analyses showed that androgen (Ar) and estrogen receptors (Esr1) were sex-specifically altered 72 h after CCI. When examining brain lesion size, we found larger lesions in male than in female mice, but did not observe effects of FIN or LET treatment. However, LET treatment exacerbated neurological deficits 24 and 72 h after CCI. On the molecular level, FIN administration reduced calpain-dependent spectrin breakdown products, a proxy of excitotoxicity and disturbed Ca²⁺ homeostasis, specifically in males, whereas LET increased the reactive astrocyte marker glial fibrillary acid protein specifically in females. Examination of neurotrophins (brain-derived neurotrophic factor, neuronal growth factor, NT-3) and their receptors (p75^NTR , TrkA, TrkB, TrkC) revealed CCI-induced down-regulation of TrkB and TrkC protein expression, which was reduced by LET in both sexes. Interestingly, FIN decreased neuronal growth factor mRNA expression and protein levels of its receptor TrkA only in males. Taken together, our data suggest a sex-specific impact on pathogenic processes in the injured brain after TBI. Sex hormones may thus modulate pathogenic processes in experimental TBI.

NGF, TrkA-P and neuroprotection after a hypoxic event in the developing central nervous system

A decrease in the concentration of oxygen in the blood and tissues (hypoxia) produces important, sometimes irreversible, damages in the central nervous system (CNS) both during development and also postnatally. The present work aims at analyzing the expression of nerve growth factor (NGF) and p75 and the activation of TrkA in response to an acute normobaric hypoxic event and to evaluate the possible protective role of exogenous NGF. The developing chick optic tectum (OT), a recognized model of corticogenesis, was used as experimental system by means of in vivo and in vitro studies. Based on identification of the period of highest sensitivity of developmental programmed cell death (ED15) we show that hypoxia has a mild but reproducible effect that consist of a temporal increase of cell death 6 h after the end of a hypoxic treatment. Cell death was preceded by a significant early increase in the expression of Nerve Growth Factor (NGF) and its membrane receptor p75. In addition, we found a biphasic response of TrkA activation: a decrease during hypoxia followed by an increase -4 h later- that temporally coincide with the interval of NGF overexpression. To test the NGF - NGF receptors role in hypoxic cell death, we quantified, in primary neuronal cultures derived from ED15 OT, the levels of TrkA activation after an acute hypoxic treatment. A significant decline in the level of TrkA activation was observed during hypoxia followed, 24 h later, by significant cell death. Interestingly, this cell death can be reverted if TrkA inactivation during hypoxia is suppressed by the addition of NGF. Our results suggest that TrkA activation may play an important role in the survival of OT neurons subjected to acute hypoxia. The role of TrkA in neuronal survival after injury may be advantageously used for the generation of neuroprotective strategies to improve prenatal insult outcomes.

Intranasal Nerve Growth Factor administration improves cerebral functions in a child with severe traumatic brain injury: A case report

BACKGROUND

Nerve growth factor (NGF) promotes neural recovery after experimental traumatic brain injury (TBI) supporting neuronal growth, differentiation and survival of brain cells and up-regulating the neurogenesis-associated protein Doublecortin (DCX). Only a few studies reported NGF administration in paediatric patients with severe TBI.

METHODS

A four-year-old boy in a persistent unresponsive wakefulness syndrome (UWS) was treated with intranasal murine NGF administration 6 months after severe TBI. The patient received four cycles of intranasal NGF (0.1 mg/kg, twice a day for 10 consecutive days).

RESULTS

NGF administration improved functional [Positron Emission Tomography/Computed Tomography (PET/CT); Single photon emission/Computed Tomography (SPECT/CT) and Magnetic Resonance Imaging (MRI)] assessment, electrophysiological [Electroencephalogram (EEG) and Visual Evoked Potential (VEP)] studies and clinical conditions. He showed improvements in voluntary movements, facial mimicry, phonation, attention and verbal comprehension, ability to cry, cough reflex, oral motility, feeding capacity, and bowel and urinary functions. After NGF administration, raised levels of both NGF and DCX were found in the cerebrospinal fluid of the patient. No side effects were reported.

CONCLUSIONS

Although further studies are needed for better understanding the neuroprotective role of this neurotrophin, intranasal NGF administration appears to be a promising and safe rescuing strategy treatment in children with neurological impairment after TBI.

Neonatal hypoxia-ischemia in rat increases doublecortin concentration in the cerebrospinal fluid

Doublecortin (DCX) is a microtubule-associated protein widely used as an indicator of neurogenesis in immunohistochemical analyses of the postmortem adult brain. A recent study reported that DCX can be quantified in the cerebrospinal fluid (CSF) from healthy rats between postnatal day 0 (P0) and P30. However, it is currently unclear whether the concentration of DCX in the CSF (CSF-DCX) may represent a measure of endogenous neurogenesis. To address this question, this study examined the impact of a neonatal hypoxic-ischemic (HI) brain injury, known to induce neurogenesis, on CSF-DCX. HI was elicited at P7 in Sprague-Dawley rat neonates, and CSF was collected serially from the cisterna magna at P5 and P10, or at P10 and P15. A sandwich immunoassay was used to measure CSF-DCX. Brains from P10 neonates were analyzed immunohistochemically for neurogenesis and cell death markers. Mean CSF-DCX was significantly higher in HI- than in sham-exposed animals, at both P10 and P15. In the HI group at P10, CSF-DCX and stroke severity correlated positively. DCX immunoreactivity was increased in the ipsilateral neurogenic niches from the P10 HI brains in comparison with that of shams. The number of proliferative DCX-positive cells was higher in the ipsilateral hippocampal subgranular zone (SGZ) than in the HI contralateral or sham SGZ. Thus, neonatal HI brain injury disrupts the developmental time-course of DCX levels in the CSF. Our data suggest that the increased concentration of DCX in the CSF after neonatal HI is the result of both cellular injury and increased neurogenesis.

Neurotrauma: The Crosstalk between Neurotrophins and Inflammation in the Acutely Injured Brain

Traumatic brain injury (TBI) is a major cause of morbidity and mortality among young individuals worldwide. Understanding the pathophysiology of neurotrauma is crucial for the development of more effective therapeutic strategies. After the trauma occurs, immediate neurologic damage is produced by the traumatic forces; this primary injury triggers a secondary wave of biochemical cascades together with metabolic and cellular changes, called secondary neural injury. In the scenario of the acutely injured brain, the ongoing secondary injury results in ischemia and edema culminating in an uncontrollable increase in intracranial pressure. These areas of secondary injury progression, or areas of “traumatic penumbra”, represent crucial targets for therapeutic interventions. Neurotrophins are a class of signaling molecules that promote survival and/or maintenance of neurons. They also stimulate axonal growth, synaptic plasticity, and neurotransmitter synthesis and release. Therefore, this review focuses on the role of neurotrophins in the acute post-injury response. Here, we discuss possible endogenous neuroprotective mechanisms of neurotrophins in the prevailing environment surrounding the injured areas, and highlight the crosstalk between neurotrophins and inflammation with focus on neurovascular unit cells, particularly pericytes. The perspective is that neurotrophins may represent promising targets for research on neuroprotective and neurorestorative processes in the short-term following TBI.

Dynamic expression of nerve growth factor and its receptor TrkA after subarachnoid hemorrhage in rat brain

Delayed ischemic neurologic deficit after subarachnoid hemorrhage results from loss of neural cells. Nerve growth factor and its receptor TrkA may promote regeneration of neural cells, but their expression after subarachnoid hemorrhage remains unclear. In the present study, a rat model of subarachnoid hemorrhage was established using two injections of autologous blood into the cistern magna. Immunohisto-chemical staining suggested that the expression of nerve growth factor and TrkA in the cerebral cortex and brainstem increased at 6 hours, peaked at 12 hours and decreased 1 day after induction of subarachnoid hemorrhage, whereas the expression in the hippocampus increased at 6 hours, peaked on day 1, and decreased 3 days later. Compared with those for the rats in the sham and saline groups, neurobehavioral scores decreased significantly 12 hours and 3 days after subarachnoid hemorrhage (P < 0.05). These results suggest that the expression of nerve growth factor and its receptor TrkA is dynamically changed in the rat brain and may thus participate in neuronal survival and nerve regeneration after subarachnoid hemorrhage.

Plasma brain-derived neurotrophic factor levels after severe traumatic brain injury

OBJECTIVE

Severe traumatic brain injury (TBI) is associated with a 30-70% mortality rate. Nevertheless, in clinical practice there are no effective biomarkers for the prediction of fatal outcome following severe TBI. Therefore, the aim was to determine whether brain-derived neurotrophic factor (BDNF) plasma levels are associated with intensive care unit (ICU) mortality in patients with severe TBI.

METHODS

This prospective study enrolled 120 male patients who suffered severe TBI (Glasgow Coma Scale 3-8 at emergency room admission). The plasma BDNF level was determined at ICU admission (mean 6.4 hours after emergency room admission).

RESULTS

Severe TBI was associated with a 35% mortality rate and 64% of the patients presented severe TBI with multi-trauma. The mean plasma BDNF concentration among the severe TBI victims was 704.2 ± 63.4 pg ml(-1) (±SEM). Nevertheless, there were no significant differences between BDNF levels in the survivor (700.2 ± 82.8 pg ml(-1)) or non-survivor (711.6 ± 97.4 pg ml(-1)) groups (p = 0.238) or in the isolated TBI (800.4 ± 117.4 pg ml(-1)) or TBI with multi-trauma groups (650.5 ± 73.9 pg ml(-1)) (p = 0.109).

CONCLUSIONS

Plasma BDNF concentrations did not correlate with either short-term fatal outcome or type of injury following severe TBI.

Therapeutic implications of the choroid plexus-cerebrospinal fluid interface in neuropsychiatric disorders

The choroid plexus (CP) comprises an epithelial monolayer that forms an important physical, enzymatic and immunologic barrier, called the blood-cerebrospinal fluid barrier (BCSFB). It is a highly vascularized organ located in the brain ventricles that is key in maintaining brain homeostasis as it produces cerebrospinal fluid (CSF) and has other important secretory functions. Furthermore, the CP-CSF interface plays a putative role in neurogenesis and has been implicated in neuropsychiatric diseases such as the neurodevelopmental disorders schizophrenia and autism. A role for this CNS border was also implicated in sleep disturbances and chronic and/or severe stress, which are risk factors for the development of neuropsychiatric conditions. Understanding the mechanisms by which disturbance of the homeostasis at the CP-CSF interface is involved in these different chronic low-grade inflammatory diseases can give new insights into therapeutic strategies. Hence, this review discusses the different roles that have been suggested so far for the CP in these neuropsychiatric disorders, with special attention to potential therapeutic applications.

Brain injury biomarkers as outcome predictors in pediatric severe traumatic brain injury

BACKGROUND

To systematically review the literature on brain injury biomarkers, defined as any injury biomarker detected in cerebrospinal fluid (CSF) or blood injury biomarkers primarily expressed in the brain parenchyma, to determine outcome prediction in pediatric severe traumatic brain injury (sTBI).

METHODS

A search of MEDLINE(®), EMBASE(®), PsycINFO(®), Pubmed(®), and the Cochrane Database, as well as grey literature sources, personal contacts, hand searches, and reference lists. The search terms used were traumatic brain injury, biomarkers, prognosis, and children. No language, publication type, or publication date restrictions were imposed. All articles were critically reviewed by two clinicians independently.

RESULTS

A total of 7,150 articles were identified initially with 16 studies identified for review. Eighteen different biomarkers were examined; 11 in CSF and 7 in blood. Outcomes assessed included either in-hospital mortality or functional state (hospital discharge, 3-months or 6-months; Glasgow Outcome Scale or Pediatric Cerebral Performance Category). Significant correlations were established between sTBI outcomes and various biomarkers in CSF (IL-6, IL-8, IL-1β, S100β, NGF, NSE, DCX, ET-1, HMGB-1, cytochrome C) and blood (GFAP, NF-H, UCH-L1, SBDP-145, leptin). Mixed results were obtained for blood S100β. Outcome did not correlate with several biomarkers in either CSF (BDNF, GDNF, α-Syn) or blood (NSE, MBP). The Class of Evidence was considered II in 1 study and III in the remaining 15 studies.

CONCLUSIONS

Based on the status of current sTBI biomarker research, we recommend that future research should be directed at both novel biomarker discovery and validation of biomarker panels in large, well-designed longitudinal studies.

Neurotrophin treatment to promote regeneration after traumatic CNS injury

Neurotrophins are a family of growth factors that have been found to be central for the development and functional maintenance of the nervous system, participating in neurogenesis, neuronal survival, axonal growth, synaptogenesis and activity-dependent forms of synaptic plasticity. Trauma in the adult nervous system can disrupt the functional circuitry of neurons and result in severe functional deficits. The limitation of intrinsic growth capacity of adult nervous system and the presence of an inhospitable environment are the major hurdles for axonal regeneration of lesioned adult neurons. Neurotrophic factors have been shown to be excellent candidates in mediating neuronal repair and establishing functional circuitry via activating several growth signaling mechanisms including neuron-intrinsic regenerative programs. Here, we will review the effects of various neurotrophins in mediating recovery after injury to the adult spinal cord.

Neurogenesis in adult human brain after traumatic brain injury

While much work has been conducted regarding the neurogenesis response to traumatic brain injury (TBI) in rodents, it remains largely unknown whether neurogenesis in adult human brain also responds to TBI in a similar manner. Here, we performed immunocytochemistry on 11 brain specimens from patients with traumatic brain injury, who underwent surgical intervention. We found that expression of neural stem/progenitor cell (NSC) protein markers, including DCX, TUC4, PSA-NCAM, SOX2 and NeuroD, was increased in the perilesional cortex of human brain after TBI compared to that of normal brain. Confocal images showed that these NSC proteins were expressed in one single cell. We also found that proliferative markers were expressed in NSC protein-positive cells after TBI, and the number of proliferative NSCs was significantly increased after TBI. Our data suggest that TBI may also induce neurogenesis in human brain.

Etanercept attenuates traumatic brain injury in rats by reducing brain TNF- α contents and by stimulating newly formed neurogenesis

It remains unclear whether etanercept penetrates directly into the contused brain and improves the outcomes of TBI by attenuating brain contents of TNF-α and/or stimulating newly formed neurogenesis. Rats that sustained TBI are immediately treated with etanercept. Acute neurological and motor injury is assessed in all rats the day prior to and 7 days after surgery. The numbers of the colocalizations of 5-bromodeoxyuridine and doublecortin specific markers in the contused brain injury that occurred during TBI were counted by immunofluorescence staining. Enzyme immunoassay for quantitative determination of TNF-α or etanercept in brain tissues is also performed. Seven days after systemic administration of etanercept, levels of etanercept can be detected in the contused brain tissues. In addition, neurological and motor deficits, cerebral contusion, and increased brain TNF-α contents caused by TBI can be attenuated by etanercept therapy. Furthermore, the increased numbers of the colocalizations of 5-bromodeoxyuridine and doublecortin specific markers in the contused brain tissues caused by TBI can be potentiated by etanercept therapy. These findings indicate that systemically administered etanercept may penetrate directly into the contused brain tissues and may improve outcomes of TBI by reducing brain contents of TNF-α and by stimulating newly formed neurogenesis.

The cerebrospinal fluid: regulator of neurogenesis, behavior, and beyond

The cerebrospinal fluid (CSF) has attracted renewed interest as an active signaling milieu that regulates brain development, homeostasis, and disease. Advances in proteomics research have enabled an improved characterization of the CSF from development through adulthood, and key neurogenic signaling pathways that are transmitted via the CSF are now being elucidated. Due to its immediate contact with neural stem cells in the developing and adult brain, the CSF's ability to swiftly distribute signals across vast distances in the central nervous system is opening avenues to novel and exciting therapeutic approaches. In this review, we will discuss the development of the choroid plexus-CSF system, and review the current literature on how the CSF actively regulates mammalian brain development, behavior, and responses to traumatic brain injury.

Effects of nerve growth factor in experimental model of focal microgyria

AIM

The effects on neural repair of intraparenchymal nerve growth factor (NGF) administration were evaluated in neonate Wistar rats with experimentally induced focal microgyria.

METHODS

A freezing focal polymicrogyric lesion was induced on the frontal cortex in 35 newborn Wistar rats on postnatal day 1. NGF was administered in 15 cases, with 20 pups as controls. Animals were sacrificed at 72 h and 7 days after NGF administration. Real-time PCR was used for the quantification of the expression of TrkA, p75, and doublecortin (DCX) at the level of the cortical lesion in seven different groups of animals: control 72 h (n = 5), control 7 days (n = 5), microgyria 72 h (n = 5), microgyria 7 days (n = 5), microgyria + NGF 72 h (n = 5), microgyria + NGF 7 days (n = 5), and control + NGF (n = 5).

RESULTS

A significant increase in TrkA expression was found in the microgyria + NGF 7 days group compared to the others. TrkA upregulation was already visible 72 h after NGF administration. Unlike TrkA, p75 expression increased in animals subjected to the experimental focal microgyria and decreased markedly after NGF administration. DCX expression in injured animals was observed to increase strongly 7 days after NGF administration compared with other groups.

CONCLUSIONS

NGF administration interferes with neural repair mechanisms at the polymicrogyric lesion site by means of TrkA and DCX upregulation which possibly counteracts the process of apoptosis caused by the brain injury.

Expression of liquoral neuroprotection markers in children with acute lymphoblastic leukemia

Brain damage related to intrathecal methotrexate in children with acute lymphoblastic leukemia (ALL) is still unclear. Neuroinflammatory mechanisms and intracerebral production of specific biomarkers, play a key role in determining neuroprotective mechanisms after brain injury. To determine whether the CSF concentrations of neuron-specific enolase (NSE), neurotrophic factors and doublecortin (DCX) are influenced by repeated intrathecal methotrexate administrations, we prospectively collected CSF samples from 10 children with ALL and 10 controls. Our results showed an increased expression of the liquoral markers. This up-regulation could be interpreted as a neuroprotective response of the brain against the neuronal damages induced by MTX.

The locus ceruleus responds to signaling molecules obtained from the CSF by transfer through tanycytes

Neurons can access signaling molecules through two principal pathways: synaptic transmission ("wiring transmission") and nonsynaptic transmission ("volume transmission"). Wiring transmission is usually considered the far more important mode of neuronal signaling. Using embryonic chick locus ceruleus (LoC) as a model, we quantified and compared routes of delivery of the neurotrophin nerve growth factor (NGF), either through a multisynaptic axonal pathway or via the CSF. We now show that the axonal pathway from the eye to the LoC involves axo-axonic transfer of NGF with receptor switching (p75 to trkA) in the optic tectum. In addition to the axonal pathway, the LoC of chick embryos has privileged access to the CSF through a specialized glial/ependymal cell type, the tanycyte. The avian LoC internalizes from the CSF in a highly specific fashion both NGF and the hormone urotensin (corticotropin-releasing factor family ligand). Quantitative autoradiography at the ultrastructural level shows that tanycytes transcytose and deliver NGF to LoC neurons via synaptoid contacts. The LoC-associated tanycytes express both p75 and trkA receptors. The NGF extracted by tanycytes from the CSF has physiological effects on LoC neurons, as evidenced by significantly altered nuclear diameters in both gain-of-function and loss-of-function experiments. Quantification of NGF extraction shows that, compared with multisynaptic axonal routes of NGF trafficking to LoC, the tanycyte route is significantly more effective. We conclude that some clinically important neuronal populations such as the LoC can use a highly efficient "back door" interface to the CSF and can receive signals via this tanycyte-controlled pathway.

Traumatic brain injury and recovery mechanisms: peptide modulation of periventricular neurogenic regions by the choroid plexus-CSF nexus

In traumatic brain injury (TBI), severe disruptions occur in the choroid plexus (CP)-cerebrospinal fluid (CSF) nexus that destabilize the nearby hippocampal and subventricular neurogenic regions. Following invasive and non-invasive injuries to cortex, several adverse sequelae harm the brain interior: (i) structural damage to CP epithelium that opens the blood-CSF barrier (BCSFB) to protein, (ii) altered CSF dynamics and intracranial pressure (ICP), (iii) augmentation of leukocyte traffic across CP into the CSF-brain, (iv) reduction in CSF sink action and clearance of debris from ventricles, and (v) less efficient provision of micronutritional and hormonal support for the CNS. However, gradual post-TBI restitution of the injured CP epithelium and ependyma, and CSF homeostatic mechanisms, help to restore subventricular/subgranular neurogenesis and the cognitive abilities diminished by CNS damage. Recovery from TBI is facilitated by upregulated choroidal/ependymal growth factors and neurotrophins, and their secretion into ventricular CSF. There, by an endocrine-like mechanism, CSF bulk flow convects the neuropeptides to target cells in injured cortex for aiding repair processes; and to neurogenic niches for enhancing conversion of stem cells to new neurons. In the recovery from TBI and associated ischemia, the modulating neuropeptides include FGF2, EGF, VEGF, NGF, IGF, GDNF, BDNF, and PACAP. Homeostatic correction of TBI-induced neuropathology can be accelerated or amplified by exogenously boosting the CSF concentration of these growth factors and neurotrophins. Such intraventricular supplementation via the CSF route promotes neural restoration through enhanced neurogenesis, angiogenesis, and neuroprotective effects. CSF translational research presents opportunities that involve CP and ependymal manipulations to expedite recovery from TBI.

Granulocyte colony-stimulating factor enhances cellular proliferation and motor function recovery on rats subjected to traumatic brain injury

OBJECTIVE

Traumatic brain injury (TBI) results in neurological dysfunction and death through primary or secondary mechanisms. Here, we evaluated the effect of osmotic pump delivery of granulocyte colony-stimulating factor (G-CSF) on the histopathology and motor function recovery of rats after experimental TBI.

METHODS

Sprague-Dawley rats were used as experimental model by fluid percussion device to cause brain injury on the motor cortex area. The rats were simultaneously subjected to TBI and were implanted of min-osmotic pump containing recombinant human G-CSF (300 μg/700 μl) via intraperitoneal injection. Motor function was assessed by rotarod test. 5-bromo-2'-deoxyuridine (BrdU) was used to label the proliferating cells and their differentiation was evaluated by histology and immunohistochemistry.

RESULTS

The G-CSF group showed significantly better motor function recovery than the control group, and the effect lasted up to 14 days after TBI. Moreover, the G-CSF group exhibited a greater increase in the number of BrdU-positive cells compared with the control group. The G-CSF group also had a significantly higher number of DCX-positive cells in the ipsilateral subventricular zone (SVZ) than the control group.

CONCLUSIONS

These data suggest that the beneficial effect of delivering G-CSF via an osmotic pump may improve the motor function and enhance neurogenesis in the SVZ of the injured brain.

Chronic upregulation of activated microglia immunoreactive for galectin-3/Mac-2 and nerve growth factor following diffuse axonal injury

Background

Diffuse axonal injury in patients with traumatic brain injury (TBI) can be associated with morbidity ranging from cognitive difficulties to coma. Magnetic resonance imaging scans now allow early detection of axonal injury following TBI, and have linked cognitive disability in these patients to white matter signal changes. However, little is known about the pathophysiology of this white matter injury, and the role of microglial activation in this process. It is increasingly recognized that microglia constitute a heterogeneous population with diverse roles following injury. In the present studies, we tested the hypothesis that following diffuse axonal injury involving the corpus callosum, there is upregulation of a subpopulation of microglia that express the lectin galectin-3/Mac-2 and are involved in myelin phagocytosis.

Methods

Adult mice were subject to midline closed skull injury or sham operation and were sacrificed 1, 8, 14 or 28 days later. Immunohistochemistry and immunofluorescence techniques were used to analyze patterns of labelling within the corpus callosum qualitatively and quantitatively.

Results

Activated microglia immunoreactive for galectin-3/Mac-2 were most abundant 1 day following injury. Their levels were attenuated at later time points after TBI but still were significantly elevated compared to sham animals. Furthermore, the majority of galectin-3/Mac-2+ microglia were immunoreactive for nerve growth factor in both sham and injured animals.

Conclusions

Our results suggest that galectin-3/Mac-2+ microglia play an important role in the pathogenesis of diffuse axonal injury both acutely and chronically and that they mediate their effects, at least in part by releasing nerve growth factor.

Clinical management and functional neuromonitoring in traumatic brain injury in children

PURPOSE OF REVIEW

Traumatic brain injury is the main cause of childhood disability and death. In this review, we highlight recent original findings and emerging themes from published literature on children with serious traumatic brain injury.

RECENT FINDINGS

We focus this review on lessons learned from our recent randomized clinical trial of hypothermia therapy in severe traumatic brain injury in children and on bedside neuromonitoring. We propose that integrating the measurement of biomarkers into clinical care as surrogate endpoints and as potential prognostic markers would allow us to evaluate earlier the effect of injury and clinical care in children after traumatic brain injury. Several methods are now more readily available to monitor cerebral physiology in children. These methods include indices evaluating the integrity of cerebral autoregulation, such as the pressure reactivity index derived from values obtained from intracranial pressure measurements, flow velocity measurements from transcranial Doppler ultrasonography or from cerebral oximetry. Other methods allow the evaluation of coma with the nonlinear analysis of electroencephalography or the evaluation of cerebral metabolism and cell death pathways with biomarkers from serum, cerebral spinal fluid, and cerebral microdialysis.

SUMMARY

We suggest expanding clinical functional neuromonitoring to help clinicians understand the burden of exposure to physiological variables and response to therapies during intensive care in order to enhance the management of critically ill children with traumatic brain injury.

Analysis of neurotrophins in human serum by immunoaffinity capillary electrophoresis (ICE) following traumatic head injury

Neurotrophins, including brain-derived neurotrophic factor (BDNF), ciliary neurotrophic factor (CNTF), neurotrophin-3 (NT-3), neurotrophin-4 (NT-4), and beta-nerve growth factor (beta-NGF), play an active role in the development, maintenance and survival of cells of the central nervous system (CNS). Previous research has indicated that a decrease in concentrations of these neurotrophins is often associated with cell death and ultimately patient demise. However, much of the research conducted analyses of samples taken directly from the CNS, i.e., of samples that are not readily available in clinical trauma centers. In an attempt to obtain a method for evaluating neurotrophins in a more readily accessible matrix, i.e., serum, a precise and accurate immunoaffinity capillary electrophoresis (ICE) method was developed and applied to measure neurotrophins in serum from patients with various degrees of head injury. The five neurotrophins of interest were extracted and concentrated by specific immunochemically immobilized antibodies, bound directly to the capillary wall, and eluted and separated in approximately 10min. NT-3, BDNF, CNTF and beta-NGF showed a marked decrease in concentration as the severity of the head injury increased: mild versus severe: 91% decrease for NT-3; 93 % decrease for BDNF; 93 % decrease for CNTF; and a 87 % decrease for beta-NGF. This decrease in concentration is consistent with the neuro-protective roles that neurotrophins play in the maintenance and survival of neuronal cells. The results obtained by the ICE method were closely comparable with those generated by a commercially available ELISA method.

Predictors of outcome following acquired brain injury in children

Acquired brain injury (ABI) in children and adolescents can result from multiple causes, including trauma, central nervous system infections, noninfectious disorders (epilepsy, hypoxia/ischemia, genetic/metabolic disorders), tumors, and vascular abnormalities. Prediction of outcomes is important, to target interventions, allocate resources, provide education to family or caregivers, and begin appropriate planning for the future. Researchers have identified several factors associated with better or worse outcomes after ABI, including variables related to the injury itself, postinjury factors related to intervention or trajectory of recovery, and preinjury or demographic factors. When examining the scientific literature, it is important to identify how "outcome" is defined, as the predictors may change depending on the outcome studied. In addition, key variables may be specific to the etiology of injury. Therefore, predictors of outcome cannot be generalized across the various etiologies of ABI, and this review will discuss predictors within the context of multiple etiologies of ABI. This article reviews the current literature on predicting outcomes after pediatric ABI, and areas in need of further research are discussed.