The neuroprotective effect of glial cell line-derived neurotrophic factor in fibrin glue against chronic focal cerebral ischemia in conscious rats

Targeting the Ischemic Core: A Therapeutic Microdialytic Approach to Prevent Neuronal Death and Restore Functional Behaviors

Ischemic stroke leads to cerebral ionic imbalance, increases acidosis, oxidative stress and release of glutamate and inflammatory mediators. Removing solute or stimulants from the ischemic core may block cell-damaging events and confer neuroprotection. In this study, we developed a minimally invasive therapeutic microdialysis (tMD) method, choosing to include serum albumin in the buffer because it is a multifunctional protein with osmotic properties. Aiming at the ischemic core, continuous perfusion of buffer supplemented with osmotic agents removes mediators of inflammation/cell damage/death from the lesion. This tMD treatment significantly removed the glutamate and zinc ions from the core, thereby reducing infarct volumes and affording high-grade neurobehavioral protection against ischemic stroke. The tMD treatment effectively protected neurons and reduced microglial activation. Furthermore, this tMD approach extended the therapeutic window to protect beyond 6 h after stroke onset. These findings support the potential clinical feasibility of applying tMD to patients with ischemic stroke, potentially without adverse effects.

Mechanisms and Potential Benefits of Neuroprotective Agents in Neurological Health

The brain contains many interconnected and complex cellular and molecular mechanisms. Injury to the brain causes permanent dysfunctions in these mechanisms. So, it continues to be an area where surgical intervention cannot be performed except for the removal of tumors and the repair of some aneurysms. Some agents that can cross the blood-brain barrier and reach neurons show neuroprotective effects in the brain due to their anti-apoptotic, anti-inflammatory and antioxidant properties. In particular, some agents act by reducing or modulating the accumulation of protein aggregates in neurodegenerative diseases (Alzheimer's disease, Parkinson's disease, Huntington's disease, Amyotrophic lateral sclerosis, and prion disease) caused by protein accumulation. Substrate accumulation causes increased oxidative stress and stimulates the brain's immune cells, microglia, and astrocytes, to secrete proinflammatory cytokines. Long-term or chronic neuroinflammatory response triggers apoptosis. Brain damage is observed with neuronal apoptosis and brain functions are impaired. This situation negatively affects processes such as motor movements, memory, perception, and learning. Neuroprotective agents prevent apoptosis by modulating molecules that play a role in apoptosis. In addition, they can improve impaired brain functions by supporting neuroplasticity and neurogenesis. Due to the important roles that these agents play in central nervous system damage or neurodegenerative diseases, it is important to elucidate many mechanisms. This review provides an overview of the mechanisms of flavonoids, which constitute a large part of the agents with neuroprotective effects, as well as vitamins, neurotransmitters, hormones, amino acids, and their derivatives. It is thought that understanding these mechanisms will enable the development of new therapeutic agents and different treatment strategies.

In situ slow-release recombinant growth differentiation factor 11 exhibits therapeutic efficacy in ischemic stroke

Systemic growth differentiation factor 11 (GDF11) treatment improves the vasculature in the hippocampus and cortex in mice in recent studies. However, systemic application of recombinant GDF11 (rGDF11) cannot cross the brain blood barrier (BBB). Thus, large doses and long-term administration are required, while systemically applied high-dose rGDF11 is associated with deleterious effects, such as severe cachexia. This study tested whether in situ low dosage rGDF11 (1 μg/kg) protects the brain against ischemic stroke and it investigated the underlying mechanisms. Fibrin glue mixed with rGDF11 was applied to the surgical cortex for the slow release of rGDF11 in mice after permanent middle cerebral artery occlusion (MCAO). In situ rGDF11 improved cerebral infarction and sensorimotor function by upregulating Smad2/3 and downregulating FOXO3 expression. In situ rGDF11 was associated with reductions in protein and lipid oxidation, Wnt5a, iNOS and COX2 expression, at 24 h after injury. In situ rGDF11 protected hippocampal neurons and subventricular neural progenitor cells against MCAO injury, and increased newborn neurogenesis in the peri-infarct cortex. Systematic profiling and qPCR analysis revealed that Pax5, Sox3, Th, and Cdk5rap2, genes associated with neurogenesis, were increased by in situ rGDF11 treatment. In addition, greater numbers of newborn neurons in the peri-infarct cortex were observed with in situ rGDF11 than with systemic application. Our evidence indicates that in situ rGDF11 effectively decreases the extent of damage after ischemic stroke via antioxidative, anti-inflammatory and proneurogenic activities. We suggest that in situ slow-release rGDF11 with fibrin glue is a potential therapeutic approach against ischemic stroke.

Lentivirally administered glial cell line-derived neurotrophic factor promotes post-ischemic neurological recovery, brain remodeling and contralesional pyramidal tract plasticity by regulating axonal growth inhibitors and guidance proteins

Owing to its potent longterm neuroprotective and neurorestorative properties, glial cell line-derived neurotrophic factor (GDNF) is currently studied in neurodegenerative disease clinical trials. However, little is known about the longterm effect of GDNF on neurological recovery, brain remodeling and neuroplasticity in the post-acute phase of ischemic stroke. In a comprehensive set of experiments, we examined the effects of lentiviral GDNF administration after ischemic stroke. GDNF reduced neurological deficits, neuronal injury, blood-brain barrier permeability in the acute phase in mice. As compared with control, enhanced motor-coordination and spontaneous locomotor activity were noted in GDNF-treated mice, which were associated with increased microvascular remodeling, increased neurogenesis and reduced glial scar formation in the peri-infarct tissue. We observed reduced brain atrophy and increased plasticity of contralesional pyramidal tract axons that crossed the midline in order to innervate denervated neurons in the ipsilesional red and facial nuclei. Contralesional axonal plasticity by GDNF was associated with decreased abundance of the axonal growth inhibitors brevican and versican in contralesional and ipsilesional brain tissue, reduced abundance of the growth repulsive guidance molecule ephrin b1 in contralesional brain tissue, increased abundance of the midline growth repulsive protein Slit1 in contralesional brain tissue and reduced abundance of Slit1's receptor Robo2 in ipsilesional brain tissue. These data indicate that GDNF potently induces longterm neurological recovery, peri-infarct brain remodeling and contralesional neuroplasticity, which are associated with the fine-tuned regulation of axonal growth inhibitors and guidance molecules that facilitate the growth of contralesional corticofugal axons in the direction to the ipsilesional hemisphere.

Characterizing the Neuroprotective Effects of S/B Remedy (Scutellaria baicalensis Georgi and Bupleurum scorzonerifolfium Willd) in Spinal Cord Injury

The main causes of dysfunction after a spinal cord injury (SCI) include primary and secondary injuries that occur during the first minutes, hours, to days after injury. This treatable secondary cascade provides a window of opportunity for delivering therapeutic interventions. An S/B remedy (Scutellaria baicalensis Georgi and Bupleurum scorzonerifolfium Willd) has anti-inflammatory, cytoprotective, and anticarcinogenic effects in liver or neurodegenerative diseases. The present work examined the effect of S/B on injured spinal cord neurons in cultures and in vivo. S/B effectively reduced peroxide toxicity and lipopolysaccharide stimulation in both spinal cord neuron/glial and microglial cultures with the involvement of PKC and HSP70. The effect of S/B was further conducted in contusive SCI rats. Intraperitoneal injections of S/B to SCI rats preserved spinal cord tissues and effectively attenuated microglial activation. Consistently, S/B treatment significantly improved hindlimb functions of SCI rats. In the acute stage of injury, S/B treatment markedly reduced the levels of ED1 expression and lactate and had a tendency to decrease lipid peroxidation. Taken together, we demonstrated long-term hindlimb restoration alongside histological improvements with systemic S/B remedy treatment in a clinically relevant model of contusive SCI. Our findings highlight the potential of an S/B remedy for acute therapeutic intervention after SCI.

Safety and efficacy evaluations of an adeno-associated virus variant for preparing IL10-secreting human neural stem cell-based therapeutics

Gene therapy technologies are inevitably required to boost the therapeutic performance of cell therapies; thus, validating the efficacy of gene carriers specifically used for preparing cellular therapeutics is a prerequisite for evaluating the therapeutic capabilities of gene and cell combinatorial therapies. Herein, the efficacy of a recombinant adeno-associated virus derivative (rAAVr3.45) was examined to evaluate its potential as a gene carrier for genetically manipulating interleukin-10 (IL10)-secreting human neural stem cells (hNSCs) that can potentially treat ischemic injuries or neurological disorders. Safety issues that could arise during the virus preparation or viral infection were investigated; no replication-competent AAVs were detected in the final cell suspensions, transgene expression was mostly transient, and no severe interference on endogenous gene expression by viral infection occurred. IL10 secretion from hNSCs infected by rAAVr3.45 encoding IL10 did not alter the transcriptional profile of any gene by more than threefold, but the exogenously boosted IL10 was sufficient to provoke immunomodulatory effects in an ischemic brain injury animal model, thereby accelerating the recovery of neurological deficits and the reduction of brain infarction volume. This study presents evidence that rAAVr3.45 can be potentially used as a gene carrier to prepare stem cell therapeutics.

Translational Regenerative Therapies for Chronic Spinal Cord Injury

Spinal cord injury is a chronic and debilitating neurological condition that is currently being managed symptomatically with no real therapeutic strategies available. Even though there is no consensus on the best time to start interventions, the chronic phase is definitely the most stable target in order to determine whether a therapy can effectively restore neurological function. The advancements of nanoscience and stem cell technology, combined with the powerful, novel neuroimaging modalities that have arisen can now accelerate the path of promising novel therapeutic strategies from bench to bedside. Several types of stem cells have reached up to clinical trials phase II, including adult neural stem cells, human spinal cord stem cells, olfactory ensheathing cells, autologous Schwann cells, umbilical cord blood-derived mononuclear cells, adult mesenchymal cells, and autologous bone-marrow-derived stem cells. There also have been combinations of different molecular therapies; these have been either alone or combined with supportive scaffolds with nanostructures to facilitate favorable cell⁻material interactions. The results already show promise but it will take some coordinated actions in order to develop a proper step-by-step approach to solve impactful problems with neural repair.

Protective effect of astaxanthin on acute cerebral infarction in rats

The aim of the study was to investigate the effect of astaxanthin and its possible mechanisms on acute cerebral infarction (ACI) in rat model. Male Sprague Dawley rats were randomly divided into sham group, model group, and astaxanthin-treated groups (20, 40, and 80 mg/kg). Neurological examination, the ratio of cerebral edema, and histopathology changes were assessed. Moreover, some oxidative stress markers were obtained for biochemical analysis, and the expression of neurotrophic factors gene was detected by real-time polymerase chain reaction (RT-PCR) method. The results showed that treatment with astaxanthin notably reduced neurological deficit scores and the ratio of cerebral edema compared with the model group. Meanwhile, astaxanthin increased the activity of catalase, superoxide dismutase, and glutathioneperoxidase as well as decreased the content of malondialdehyde in brain tissue. RT-PCR results showed that the expression of brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) mRNA were increased with astaxanthin treatment. The results indicated that astaxanthin could ameliorate ACI followed by suppressing oxidative stress and upregulating the expression of BDNF and NGF mRNA.

Delayed epidural transplantation of human induced pluripotent stem cell-derived neural progenitors enhances functional recovery after stroke

Induced pluripotent stem cell-derived neural progenitor cells (iPSC-NPCs) are a promising source of tailor-made cell therapy for neurological diseases. However, major obstacles to clinical use still exist. To circumvent complications related to intracerebral administration, we implanted human iPSC-NPCs epidurally over the peri-infarct cortex 7 days after permanent middle cerebral artery occlusion in adult rats. Compared to controls, cell-treated rats showed significant improvements in paretic forelimb usage and grip strength from 10 days post-transplantation (dpt) onwards, as well as reductions in lesion volumes, inflammatory infiltration and astrogliosis at 21 dpt. Few iPSC-NPCs migrated into rat peri-infarct cortices and exhibited poor survival in tissue. To examine the paracrine therapeutic mechanisms of epidural iPSC-NPC grafts, we used transmembrane co-cultures of human iPSC-NPCs with rat cortical cells subjected to oxygen-glucose deprivation. Compared to other human stem cells, iPSC-NPCs were superior at promoting neuronal survival and outgrowth, and mitigating astrogliosis. Using comparative whole-genome microarrays and cytokine neutralization, we identified a neurorestorative secretome from iPSC-NPCs, and neutralizing enriched cytokines abolished neuroprotective effects in co-cultures. This proof-of-concept study demonstrates a relatively safe, yet effective epidural route for delivering human iPSC-NPCs, which acts predominately through discrete paracrine effects to promote functional recovery after stroke.

Multiple uses of fibrin sealant for nervous system treatment following injury and disease

Lesions to the nervous system often produce hemorrhage and tissue loss that are difficult, if not impossible, to repair. Therefore, scar formation, inflammation and cavitation take place, expanding the lesion epicenter. This significantly worsens the patient conditions and impairment, increasing neuronal loss and glial reaction, which in turn further decreases the chances of a positive outcome. The possibility of using hemostatic substances that also function as a scaffold, such as the fibrin sealant, reduces surgical time and improve postoperative recovery. To date, several studies have demonstrated that human blood derived fibrin sealant produces positive effects in different interventions, becoming an efficient alternative to suturing. To provide an alternative to homologous fibrin sealants, the Center for the Study of Venoms and Venomous Animals (CEVAP, Brazil) has proposed a new bioproduct composed of certified animal components, including a thrombin-like enzyme obtained from snake venom and bubaline fibrinogen. Thus, the present review brings up to date literature assessment on the use of fibrin sealant for nervous system repair and positions the new heterologous bioproduct from CEVAP as an alternative to the commercial counterparts. In this way, clinical and pre-clinical data are discussed in different topics, ranging from central nervous system to peripheral nervous system applications, specifying positive results as well as future enhancements that are necessary for improving the use of fibrin sealant therapy.

Electroacupuncture promotes the recovery of motor neuron function in the anterior horn of the injured spinal cord

Acupuncture has been shown to lessen the inflammatory reaction after acute spinal cord injury and reduce secondary injury. However, the mechanism of action remains unclear. In this study, a rat model of spinal cord injury was established by compressing the T_8–9 segments using a modified Nystrom method. Twenty-four hours after injury, Zusanli (ST36), Xuanzhong (GB39), Futu (ST32) and Sanyinjiao (SP6) were stimulated with electroacupuncture. Rats with spinal cord injury alone were used as controls. At 2, 4 and 6 weeks after injury, acetylcholinesterase (AChE) activity at the site of injury, the number of medium and large neurons in the spinal cord anterior horn, glial cell line-derived neurotrophic factor (GDNF) mRNA expression, and Basso, Beattie and Bresnahan locomotor rating scale scores were greater in the electroacupuncture group compared with the control group. These results demonstrate that electroacupuncture increases AChE activity, up-regulates GDNF mRNA expression, and promotes the recovery of motor neuron function in the anterior horn after spinal cord injury.

Acidic FGF promotes neurite outgrowth of cortical neurons and improves neuroprotective effect in a cerebral ischemic rat model

Acidic fibroblast growth factor (aFGF) is a neurotrophic factor which is a powerful neuroprotective and neuroregenerative factor of the nervous system. Prior study had shown that levels of FGFs significantly increase following ischemic injury, reflecting a physiological protection mechanism. However, few reports demonstrated the efficacy of applying aFGF in cerebral ischemia. A recent report showed that the intranasal aFGF treatment improved neurological functional recovery; however, it did not significantly reduce the lesion size in ischemic rats. The present study examines the neuroprotective effect of aFGF on cortical neuron-glial cultures under oxygen glucose deprivation (OGD)-induced cell damage and investigates whether epidural application of slow-released aFGF could improve benefit on ischemic stroke injury in conscious rats. We used a topical application of aFGF mixed in fibrin glue, a slow-release carrier, over the peri-ischemic cortex and examined such treatment on cerebral infarction and behavioral impairments of rats subjected to focal cerebral ischemia (FCI). Results demonstrate that aFGF effectively protected cortical neuron-glial cultures from OGD-induced neuronal damage. Neurite extension from cortical neurons was significantly enhanced by aFGF, mediated through activation of AKT and ERK. In addition, topical application of fibrin glue-mixed aFGF dose-dependently reduced ischemia-induced brain infarction and improved functional restoration in ischemic stroke rats. Slow-released aFGF not only protected hippocampal and cortical cell loss but reduced microglial infiltration in FCI rats. Our results suggest that aFGF mixed in fibrin glue could prolong the protective/regenerative efficacy of aFGF to the damaged brain tissue and thus improve the functional restorative effect of aFGF.

Recovery of neurological function of ischemic stroke by application of conditioned medium of bone marrow mesenchymal stem cells derived from normal and cerebral ischemia rats

Background

Several lines of evidence have demonstrated that bone marrow-derived mesenchymal stem cells (BM-MSC) release bioactive factors and provide neuroprotection for CNS injury. However, it remains elusive whether BM-MSC derived from healthy donors or stroke patients provides equal therapeutic potential. The present work aims to characterize BM-MSC prepared from normal healthy rats (NormBM-MSC) and cerebral ischemia rats (IschBM-MSC), and examine the effects of their conditioned medium (Cm) on ischemic stroke animal model.

Results

Isolated NormBM-MSC or IschBM-MSC formed fibroblastic like morphology and expressed CD29, CD90 and CD44 but failed to express the hematopoietic marker CD34. The number of colony formation of BM-MSC was more abundant in IschBM-MSC than in NormBM-MSC. This is in contrast to the amount of Ficoll-fractionated mononuclear cells from normal donor and ischemic rats. The effect of cm of BM-MSC was further examined in cultures and in middle cerebral artery occlusion (MCAo) animal model. Both NormBM-MSC Cm and IschBM-MSC Cm effectively increased neuronal connection and survival in mixed neuron-glial cultures. In vivo, intravenous infusion of NormBM-MSC Cm and IschBM-MSC Cm after stroke onset remarkably improved functional recovery. Furthermore, NormBM-MSC Cm and IschBM-MSC Cm increased neurogenesis and attenuated microglia/ macrophage infiltration in MCAo rat brains.

Conclusions

Our data suggest equal effectiveness of BM-MSC Cm derived from ischemic animals or from a normal population. Our results thus revealed the potential of BM-MSC Cm on treatment of ischemic stroke.

Functional improvement of focal cerebral ischemia injury by subdural transplantation of induced pluripotent stem cells with fibrin glue

Ischemic stroke is the leading cause of disability in the world. Cell transplantation has emerged in various neurological diseases as a potential therapeutic approach in the postacute stroke phase. Recently, inducible pluripotent stem (iPS) cells showed potential for multilineage differentiation and provide a resource for stem cell-based therapies. However, whether iPS transplantation could improve the function of stroke-like model is still an open question. The aim of this study is to investigate the therapeutic effects of subdural transplantation of iPS mixed with fibrin glue (iPS-FG) on cerebral ischemic rats induced by middle cerebral artery occlusion (MCAO). We demonstrated an efficient method to differentiate iPS into astroglial-like and neuron-like cells which display functional electrophysiological properties. In vivo study firstly showed that the direct injection of iPS into damaged areas of rat cortex significantly decreased the infarct size and improved the motor function in rats with MCAO. Furthermore, we found that the subdural iPS-FG can also effectively reduce the total infarct volume and greatly improve the behavior of rats with MCAO to perform rotarod and grasping tasks. Importantly, analysis of cytokine expression in iPS-FG-treated ischemic brains revealed a significant reduction of pro-inflammatory cytokines and an increase of anti-inflammatory cytokines. Taken together, these results suggest that iPS cells could improve the motor function, reduce infarct size, attenuate inflammation cytokines, and mediate neuroprotection after ischemic stroke. Subdural iPS-FG could be considered as a more safe approach because this method can avoid iatrogenic injury to brain parenchyma and enhance recovering from stoke-induced impairment.

The differential effects of pathway- versus target-derived glial cell line-derived neurotrophic factor on peripheral nerve regeneration

OBJECT

Glial cell line-derived neurotrophic factor (GDNF) has potent survival effects on central and peripheral nerve populations. The authors examined the differential effects of GDNF following either a sciatic nerve crush injury in mice that overexpressed GDNF in the central or peripheral nervous systems (glial fibrillary acidic protein [GFAP]-GDNF) or in the muscle target (Myo-GDNF).

METHODS

Adult mice (GFAP-GDNF, Myo-GDNF, or wild-type [WT] animals) underwent sciatic nerve crush and were evaluated using histomorphometry and muscle force and power testing. Uninjured WT animals served as controls.

RESULTS

In the sciatic nerve crush, the Myo-GDNF mice demonstrated a higher number of nerve fibers, fiber density, and nerve percentage (p < 0.05) at 2 weeks. The early regenerative response did not result in superlative functional recovery. At 3 weeks, GFAP-GDNF animals exhibit fewer nerve fibers, decreased fiber width, and decreased nerve percentage compared with WT and Myo-GDNF mice (p < 0.05). By 6 weeks, there were no significant differences between groups.

CONCLUSIONS

Peripheral delivery of GDNF resulted in earlier regeneration following sciatic nerve crush injuries than that with central GDNF delivery. Treatment with neurotrophic factors such as GDNF may offer new possibilities for the treatment of peripheral nerve injury.

FUNCTIONAL RECOVERY AND EXPRESSION OF GDNF SEEN IN PHOTOCHEMICALLY INDUCED CEREBRAL INFARCTION

Glial cell line-derived neurotrophic factor (GDNF) is a potent neurotrophic factor involved in the survival and proliferation of neurons. However, there have been few reports examining the relationship between GDNF and functional recovery after cerebral infarction. The authors investigated the change in the expression of GDNF proteins during functional recovery in rats following photochemically induced cerebral infarctions. Functional recovery for the first 14 days after the infarction was evaluated using a beam-walking test. The number of GDNF-like immunoreactive cells around the infarction were counted at various times (24 h, 72 h, 7 days, and 14 days) post-infarction. Immunohistochemical analysis of brain sections showed that the expression of GDNF-like immunoreactive cells was significantly increased in the temporal cortex until 7 days on the side ipsilateral to the infarction, and had decreased by 14 days. Likewise, the functional recovery of paralysis was substantial until 7 days post-infarction, after which the improvement was mild. Therefore, the expression of GDNF protein might have some relationship with the functional recovery of paralysis. There are great hopes that GDNF could be used as a therapeutic agent for cerebral infarction.

Human neural stem cells overexpressing glial cell line-derived neurotrophic factor in experimental cerebral hemorrhage

Recent studies have reported that glial cell line-derived growth factor (GDNF) has neurotrophic effects on the central nervous system, and the neural stem cells (NSCs) engrafted in animal models of stroke survive and ameliorate the neurological deficits. In this study, a stable human NSC line overexpressing GDNF (F3.GDNF) was transplanted next to the intracerebral hemorrhage (ICH) lesion site and a possible therapeutic effect was investigated. F3.GDNF human NSC line was transplanted into the cortex overlying the striatal ICH lesion. ICH was induced in adult mice by the unilateral injection of bacterial collagenase into the striatum. The animals were evaluated for 8 weeks with rotarod and limb placement tests. Transplanted NSCs were detected by beta-gal immunostaining with double labeling of neurofilament, microtubule associated protein-2, glial fibrillary acidic protein or human nuclear matrix antigen (HuNuMA). F3.GDNF human NSCs produced a four times higher amount of GDNF over parental F3 cells in vitro, induced behavioral improvement in ICH mice after brain transplantation and two- to threefold increase in cell survival of transplanted NSCs at 2 and 8 weeks post-transplantation. In F3.GDNF-grafted ICH brain, a significant increase in the antiapoptotic protein and cell survival signal molecules, and a marked reduction in proapoptotic proteins were found as compared with control group. Brain transplantation of human NSCs overexpressing GDNF in ICH animals provided functional recovery in ICH animals, and survival and differentiation of grafted human NSCs. These results indicate that the F3.GDNF human NSCs should be of a great value as a cellular source for the cellular therapy in animal models of human neurological disorders including ICH.

Expression of GDNF transgene in astrocytes improves cognitive deficits in aged rats

Glial cell line-derived neurotrophic factor (GDNF) was assayed for its neurotrophic effects against the neuronal atrophy that causes cognitive deficits in old age. Aged Fisher 344 rats with impairment in the Morris water maze received intrahippocampal injections at the dorsal CA1 area of either a lentiviral vector encoding human GDNF or the same vector encoding human green fluorescent protein as a control. Recombinant lentiviral vectors constructed with human cytomegalovirus promotor and pseudotyped with lyssavirus Mokola glycoprotein specifically transduced the astrocytes in vivo. Astrocyte-secreted GDNF enhanced neuron function as shown by local increases in synthesis of the neurotransmitters acetylcholine, dopamine and serotonin. This neurotrophic effect led to cognitive improvement of the rats as early as 2 weeks after gene transduction. Spatial learning and memory testing showed a significant gain in cognitive abilities due to GDNF exposure, whereas control-transduced rats kept their performance at the chance level. These results confirm the broad spectrum of the neurotrophic action of GDNF and open new gene therapy possibilities for reducing age-related neurodegeneration.

Fibrin glue system for adjuvant brachytherapy of brain tumors with 188Re and 186Re-labeled microspheres

Brain tumors such as glioblastoma reappear in their original location in almost 50% of cases. To prevent this recurrence, we developed a radiopharmaceutical system that consists of a gel applied immediately after surgical resection of a brain tumor to deliver local radiation booster doses. The gel, which strongly adheres to tissue in the treatment area, consists of fibrin glue containing the beta-emitters rhenium-188 and rhenium-186 in microsphere-bound form. Such microspheres can be prepared by short (2 h or less) neutron activation even in low neutron flux reactors, yielding a mixture of the two beta-emitters rhenium-188 (E(max)=2.1 MeV, half life=17 h) and rhenium-186 (E(max)=1.1 MeV, half life=90.6h). The dosimetry of this rhenium-188/rhenium-186 fibrin glue system was determined using gafchromic film measurements. The treatment efficacy of the radioactive fibrin glue was measured in a 9L-glioblastoma rat model. All animals receiving the non-radioactive fibrin glue died within 17+/-3 days, whereas 60% of the treated animals survived 36 days, the final length of the experiment. Control animals that were treated with the same amount of radioactive fibrin glue, but had not received a previous tumor cell injection, showed no toxic effects over one year. The beta-radiation emitting rhenium-188/rhenium-186-based gel thus provides an effective method of delivering high doses of local radiation to tumor tissue, particularly to wet areas where high adhesive strength and long-term radiation (with or without drug) delivery are needed.

The long-term neurocompatibility of human fibrin sealant and equine collagen as biomatrices in experimental spinal cord injury

INTRODUCTION

While fibrin sealant (FS) and equine collagen (EC) have been used as scaffold materials in experimental spinal cord injury (SCI), questions concerning neurocompatibility still remain. In this study, we assessed potential adverse effects, as well as functional and histological impact of FS and EC in subtotal hemisection of the thoracic spinal cord (SC) in rats.

METHODS

124 male rats were randomly assigned to four main groups (n=31): Sham (SH), Lesion only (L), fibrin sealant (GFS) and equine collagen group (GEC). SH animals received laminectomy only; all other animals underwent subtotal lateral hemisection at T9. Treatment consisted of application of FS or EC into the lesion gap in GFS and GEC, which was left empty in L. GFS, GEC, L and SH were each further divided into 4 subgroups: One subgroup, consisting of 10 rats was subjected to behavioural and reflex testing before surgery and followed up on days 1,7, 14, 21, 28 post op and then sacrificed. Haemalaun or cresyl violet (CV) was used to identify neutrophils in parasagittal cord sections which were obtained on day 1 (n=7). Sections stained for quantification of microglia/macrophages using ED-1 on day 3 (n=7), day 7 (n=7) and day 28 (n=7 out of 10). Additionally, neural filament (NF) staining was chosen to detect axonal regeneration and the length of ingrowth into FS and EC, Luxol blue for myelination, Von Willebrand factor for vascularisation, and glial fibrillary acidic protein (GFAP) staining for detection of astrocytes in glial scars on day 28.

RESULTS

No adverse effects were observed in the treatment groups. Compared to L, GFS and GEC performed significantly better in the Basso, Beattie, Bresnahan (BBB) score and hopping responses. Proprioceptive placing was markedly improved in FS and EC compared to L. Axonal regrowth was found in GFS and GEC--the regrowth in the GFS was accompanied by myelination and vascularisation. Glial scarring occurred in all groups. Discussion Both biomatrices improved functional recovery compared to L and no adverse effects were perceived.

Post-traumatic application of brain-derived neurotrophic factor and glia-derived neurotrophic factor on the rat spinal cord enhances neuroprotection and improves motor function

We examined the potential efficacy of brain-derived neurotrophic factor (BDNF) and glial-derived neurotrophic factor (GDNF) applied over traumatized spinal cord, alone or in combination, for attenuating motor dysfunction, blood-spinal cord barrier (BSCB) breakdown, edema formation, and cell injury in a rat model. Under Equithesin anesthesia, spinal cord injury (SCI) was performed by making a unilateral incision into the right dorsal horn of the T10-11 segment. The rats were allowed to survive 5 hours after trauma. The BDNF or GDNF was applied (0.1 to 1 microg/10 microl in phosphate buffer saline) 30, 60, or 90 minutes after SCI. Topical application of BDNF or GDNF 30 minutes after SCI in high concentration (0.5 microg and 1 microg) significantly improved motor function and reduced BSCB breakdown, edema formation, and cell injury at 5 hours. These beneficial effects of neurotrophins were markedly absent when administered separately either 60 or 90 minutes after injury. However, combined application of BDNF and GDNF at 60 or 90 minutes after SCI resulted in a significant reduction in motor dysfunction and spinal cord pathology. These novel observations suggest that neurotrophins in combination have potential therapeutic value for the treatment of SCI in clinical situations.

Actions of neurotrophic factors and their signaling pathways in neuronal survival and axonal regeneration

Adult axons in the mammalian central nervous system do not elicit spontaneous regeneration after injury, although many affected neurons have survived the neurotrauma. However, axonal regeneration does occur under certain conditions. These conditions include: (a) modification of regrowth environment, such as supply of peripheral nerve bridges and transplantation of Schwann cells or olfactory ensheathing glia to the injury site; (b) application of neurotrophic factors at the cell soma and axon tips; (c) blockade of growth-inhibitory molecules such as Nogo-A, myelin-associated glycoprotein, and oligodendrocyte-myelin glycoprotein; (d) prevention of chondroitin-sulfate-proteoglycans-related scar tissue formation at the injury site using chondroitinase ABC; and (e) elevation of intrinsic growth potential of injured neurons via increasing intracellular cyclic adenosine monophosphate level. A large body of evidence suggests that these conditions achieve enhanced neuronal survival and axonal regeneration through sometimes overlapping and sometimes distinct signal transduction mechanisms, depending on the targeted neuronal populations and intervention circumstances. This article reviews the available information on signal transduction pathways underlying neurotrophic-factor-mediated neuronal survival and neurite outgrowth/axonal regeneration. Better understanding of signaling transduction is important in helping us develop practical therapeutic approaches for encouraging neuronal survival and axonal regeneration after traumatic injury in clinical context.