Inhibition of brain-derived neurotrophic factor and glial cell line-derived neurotrophic factor expression reduces dopaminergic sprouting in the injured striatum

pTDP-43 levels correlate with cell type specific molecular alterations in the prefrontal cortex of C9orf72 ALS/FTD patients

Repeat expansions in the C9orf72 gene are the most common genetic cause of amyotrophic lateral sclerosis and familial frontotemporal dementia (ALS/FTD). To identify molecular defects that take place in the dorsolateral frontal cortex of patients with C9orf72 ALS/FTD, we compared healthy controls with C9orf72 ALS/FTD donor samples staged based on the levels of cortical phosphorylated TAR DNA binding protein (pTDP-43), a neuropathological hallmark of disease progression. We identified distinct molecular changes in different cell types that take place during FTD development. Loss of neurosurveillance microglia and activation of the complement cascade take place early, when pTDP-43 aggregates are absent or very low, and become more pronounced in late stages, suggesting an initial involvement of microglia in disease progression. Reduction of layer 2-3 cortical projection neurons with high expression of CUX2/LAMP5 also occurs early, and the reduction becomes more pronounced as pTDP-43 accumulates. Several unique features were observed only in samples with high levels of pTDP-43, including global alteration of chromatin accessibility in oligodendrocytes, microglia, and astrocytes; higher ratios of premature oligodendrocytes; increased levels of the noncoding RNA NEAT1 in astrocytes and neurons, and higher amount of phosphorylated ribosomal protein S6. Our findings reveal previously unknown progressive functional changes in major cell types found in the frontal cortex of C9orf72 ALS/FTD patients that shed light on the mechanisms underlying the pathology of this disease.

Lipocalin-2 Is a Key Regulator of Neuroinflammation in Secondary Traumatic and Ischemic Brain Injury

Reactive glial cells are hallmarks of brain injury. However, whether these cells contribute to secondary inflammatory pathology and neurological deficits remains poorly understood. Lipocalin-2 (LCN2) has inflammatory and neurotoxic effects in various disease models; however, its pathogenic role in traumatic brain injury remains unknown. The aim of the present study was to investigate the expression of LCN2 and its role in neuroinflammation following brain injury. LCN2 expression was high in the mouse brain after controlled cortical impact (CCI) and photothrombotic stroke (PTS) injury. Brain levels of LCN2 mRNA and protein were also significantly higher in patients with chronic traumatic encephalopathy (CTE) than in normal subjects. RT-PCR and immunofluorescence analyses revealed that astrocytes were the major cellular source of LCN2 in the injured brain. Lcn2 deficiency or intracisternal injection of an LCN2 neutralizing antibody reduced CCI- and PTS-induced brain lesions, behavioral deficits, and neuroinflammation. Mechanistically, in cultured glial cells, recombinant LCN2 protein enhanced scratch injury-induced proinflammatory cytokine gene expression and inhibited Gdnf gene expression, whereas Lcn2 deficiency exerted opposite effects. Together, our results from CTE patients, rodent brain injury models, and cultured glial cells suggest that LCN2 mediates secondary damage response to traumatic and ischemic brain injury by promoting neuroinflammation and suppressing the expression of neurotropic factors.

Practically Defined Off-State Dyskinesia Following Repeated Intraputamenal Glial Cell Line-Derived Neurotrophic Factor Administration

BACKGROUND

We recently showed that by employing an enhanced drug-delivery approach, repeated administration of glial cell line-derived neurotrophic factor (GDNF) can produce a spatially distributed increased ¹⁸ F-DOPA positron emission tomography (PET) uptake, suggesting sprouting of dopaminergic terminals throughout the putamen structure. Despite this, we failed to prove a significant measurable clinical response. Since, however, we have identified a subject demonstrating a temporal relationship between repeated GDNF infusions and dyskinesia arising in the practically defined off (pracoff) state.

OBJECTIVES

To describe the development of pracoff dyskinesia across our study population and consider its utility as an indicator that trophic factor-induced terminal sprouting can affect enhanced endogenous dopamine levels.

METHODS

This was a blinded retrospective analysis of videotaped motor assessments at eight weekly study visits. Dyskinesia in the pracoff and supramaximal on state were rated using the Clinical Dyskinesia Rating Scale. Logistic regression was employed to explore the predictors of pracoff dyskinesia. Generalized estimated equations were used to estimate the cumulative effect of repeated GDNF infusions.

RESULTS

Mild-moderate choreiform dyskinesia in the pracoff state were seen in 47 assessments in 17 (n = 41) subjects. During the 18-month timeframe, each subsequent 8-week period of receiving GDNF increased the risk of demonstrating pracoff state dyskinesia by 34% (odds ratio [OR], 1.34 (95% confidence interval [CI], 1.20, 1.50); P < 0.001). An increasing supramaximal on dyskinesia score (OR, 1.17 [95% CI, 1.07, 1.30]; P = 0.001) also increased the likelihood of pracoff dyskinesia at that visit.

CONCLUSIONS

We report the first description of increasingly prevalent pracoff-state dyskinesia developing during the course of a trophic factor study. This may provide a surrogate marker that GDNF can enable recovery of endogenous dopamine release even in advanced Parkinson's disease. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Balneotherapy decreases mechanical hyperalgesia by reversing BDNF and NOS2 immunocontent in spinal cord of mice with neuropathic pain

In the last decades, balneotherapy or thermalism has been used for health promotion and in the treatment of inflammatory and chronic processes. We found that balneotherapy reduced mechanical hyperalgesia, as well the increase of BDNF and NOS2 levels in the spinal cord, while increased BDNF and NOS1 in the paw. The data presented herein demonstrated for the first time in a murine model of neuropathic pain, the analgesic effect of balneotherapy with the water from the natural springs of Santo Amaro da Imperatriz-Brazil. Nevertheless, future clinical trials should be conducted to test the effectiveness of balneotherapy in neuropathic pain patients.

Extended Treatment with Glial Cell Line-Derived Neurotrophic Factor in Parkinson's Disease

Background:

Intraputamenal glial cell line-derived neurotrophic factor (GDNF), administered every 4 weeks to patients with moderately advanced Parkinson’s disease, did not show significant clinical improvements against placebo at 40 weeks, although it significantly increased [¹⁸F]DOPA uptake throughout the entire putamen.

Objective:

This open-label extension study explored the effects of continued (prior GDNF patients) or new (prior placebo patients) exposure to GDNF for another 40 weeks.

Methods:

Using the infusion protocol of the parent study, all patients received GDNF without disclosing prior treatment allocations (GDNF or placebo). The primary outcome was the percentage change from baseline to Week 80 in the OFF state Unified Parkinson’s Disease Rating Scale (UPDRS) motor score.

Results:

All 41 parent study participants were enrolled. The primary outcome decreased by 26.7±20.7% in patients on GDNF for 80 weeks (GDNF/GDNF; N = 21) and 27.6±23.6% in patients on placebo for 40 weeks followed by GDNF for 40 weeks (placebo/GDNF, N = 20; least squares mean difference: 0.4%, 95% CI: –13.9, 14.6, p = 0.96). Secondary endpoints did not show significant differences between the groups at Week 80 either. Prespecified comparisons between GDNF/GDNF at Week 80 and placebo/GDNF at Week 40 showed significant differences for mean OFF state UPDRS motor (–9.6±6.7 vs. –3.8±4.2 points, p = 0.0108) and activities of daily living score (–6.9±5.5 vs. –1.0±3.7 points, p = 0.0003). No treatment-emergent safety concerns were identified.

Conclusions:

The aggregate study results, from the parent and open-label extension suggest that future testing with GDNF will likely require an 80- rather than a 40-week randomized treatment period and/or a higher dose.

GDNF, A Neuron-Derived Factor Upregulated in Glial Cells during Disease

In a healthy adult brain, glial cell line-derived neurotrophic factor (GDNF) is exclusively expressed by neurons, and, in some instances, it has also been shown to derive from a single neuronal subpopulation. Secreted GDNF acts in a paracrine fashion by forming a complex with the GDNF family receptor α1 (GFRα1), which is mainly expressed by neurons and can act in cis as a membrane-bound factor or in trans as a soluble factor. The GDNF/GFRα1 complex signals through interactions with the "rearranged during transfection" (RET) receptor or via the neural cell adhesion molecule (NCAM) with a lower affinity. GDNF can also signal independently from GFRα1 by interacting with syndecan-3. RET, which is expressed by neurons involved in several pathways (nigro-striatal dopaminergic neurons, motor neurons, enteric neurons, sensory neurons, etc.), could be the main determinant of the specificity of GDNF's pro-survival effect. In an injured brain, de novo expression of GDNF occurs in glial cells. Neuroinflammation has been reported to induce GDNF expression in activated astrocytes and microglia, infiltrating macrophages, nestin-positive reactive astrocytes, and neuron/glia (NG2) positive microglia-like cells. This disease-related GDNF overexpression can be either beneficial or detrimental depending on the localization in the brain and the level and duration of glial cell activation. Some reports also describe the upregulation of RET and GFRα1 in glial cells, suggesting that GDNF could modulate neuroinflammation.

Randomized trial of intermittent intraputamenal glial cell line-derived neurotrophic factor in Parkinson's disease

We investigated the effects of glial cell line-derived neurotrophic factor (GDNF) in Parkinson’s disease, using intermittent intraputamenal convection-enhanced delivery via a skull-mounted transcutaneous port as a novel administration paradigm to potentially afford putamen-wide therapeutic delivery. This was a single-centre, randomized, double-blind, placebo-controlled trial. Patients were 35–75 years old, had motor symptoms for 5 or more years, and presented with moderate disease severity in the OFF state [Hoehn and Yahr stage 2–3 and Unified Parkinson’s Disease Rating Scale motor score (part III) (UPDRS-III) between 25 and 45] and motor fluctuations. Drug delivery devices were implanted and putamenal volume coverage was required to exceed a predefined threshold at a test infusion prior to randomization. Six pilot stage patients (randomization 2:1) and 35 primary stage patients (randomization 1:1) received bilateral intraputamenal infusions of GDNF (120 µg per putamen) or placebo every 4 weeks for 40 weeks. Efficacy analyses were based on the intention-to-treat principle and included all patients randomized. The primary outcome was the percentage change from baseline to Week 40 in the OFF state (UPDRS-III). The primary analysis was limited to primary stage patients, while further analyses included all patients from both study stages. The mean OFF state UPDRS motor score decreased by 17.3 ± 17.6% in the active group and 11.8 ± 15.8% in the placebo group (least squares mean difference: −4.9%, 95% CI: −16.9, 7.1, P = 0.41). Secondary endpoints did not show significant differences between the groups either. A post hoc analysis found nine (43%) patients in the active group but no placebo patients with a large clinically important motor improvement (≥10 points) in the OFF state (P = 0.0008). ¹⁸F-DOPA PET imaging demonstrated a significantly increased uptake throughout the putamen only in the active group, ranging from 25% (left anterior putamen; P = 0.0009) to 100% (both posterior putamina; P < 0.0001). GDNF appeared to be well tolerated and safe, and no drug-related serious adverse events were reported. The study did not meet its primary endpoint. ¹⁸F-DOPA imaging, however, suggested that intermittent convection-enhanced delivery of GDNF produced a putamen-wide tissue engagement effect, overcoming prior delivery limitations. Potential reasons for not proving clinical benefit at 40 weeks are discussed.

mGluR5 Allosteric Modulation Promotes Neurorecovery in a 6-OHDA-Toxicant Model of Parkinson's Disease

Parkinson's disease is a neurodegenerative disease characterized by a loss of dopaminergic substantia nigra neurons and depletion of dopamine. To date, current therapeutic approaches focus on managing motor symptoms and trying to slow neurodegeneration, with minimal capacity to promote neurorecovery. mGluR5 plays a key role in neuroplasticity, and altered mGluR5 signaling contributes to synucleinopathy and dyskinesia in patients with Parkinson's disease. Here, we tested whether the mGluR5-negative allosteric modulator, (2-chloro-4-[2[2,5-dimethyl-1-[4-(trifluoromethoxy) phenyl] imidazol-4-yl] ethynyl] pyridine (CTEP), would be effective in improving motor deficits and promoting neural recovery in a 6-hydroxydopamine (6-OHDA) mouse model. Lesions were induced by 6-ODHA striatal infusion, and 30 days later treatment with CTEP (2 mg/kg) or vehicle commenced for either 1 or 12 weeks. Animals were subjected to behavioral, pathological, and molecular analyses. We also assessed how long the effects of CTEP persisted, and finally, using rapamycin, determined the role of the mTOR pathway. CTEP treatment induced a duration-dependent improvement in apomorphine-induced rotation and performance on rotarod in lesioned mice. Moreover, CTEP promoted a recovery of striatal tyrosine hydroxylase-positive fibers and normalized FosB levels in lesioned mice. The beneficial effects of CTEP were paralleled by an activation of mammalian target of rapamycin (mTOR) pathway and elevated brain-derived neurotrophic factor levels in the striatum of lesioned mice. The mTOR inhibitor, rapamycin (sirolimus), abolished CTEP-induced neurorecovery and rescue of motor deficits. Our findings indicate that mTOR pathway is a useful target to promote recovery and that mGluR5 allosteric regulators may potentially be repurposed to selectively target this pathway to enhance neuroplasticity in patients with Parkinson's disease.

Therapeutic Potential of Neurotrophins for Repair After Brain Injury: A Helping Hand From Biomaterials

Stroke remains the leading cause of long-term disability with limited options available to aid in recovery. Significant effort has been made to try and minimize neuronal damage following stroke with use of neuroprotective agents, however, these treatments have yet to show clinical efficacy. Regenerative interventions have since become of huge interest as they provide the potential to restore damaged neural tissue without being limited by a narrow therapeutic window. Neurotrophins, such as brain-derived neurotrophic factor (BDNF), and their high affinity receptors are actively produced throughout the brain and are involved in regulating neuronal activity and normal day-to-day function. Furthermore, neurotrophins are known to play a significant role in both protection and recovery of function following neurodegenerative diseases such as stroke and traumatic brain injury (TBI). Unfortunately, exogenous administration of these neurotrophins is limited by a lack of blood-brain-barrier (BBB) permeability, poor half-life, and rapid degradation. Therefore, we have focused this review on approaches that provide a direct and sustained neurotrophic support using pharmacological therapies and mimetics, physical activity, and potential drug delivery systems, including discussion around advantages and limitations for use of each of these systems. Finally, we discuss future directions of biomaterial drug-delivery systems, including the incorporation of heparan sulfate (HS) in conjunction with neurotrophin-based interventions.

Striatal Reinnervation Process after Acute Methamphetamine-Induced Dopaminergic Degeneration in Mice

Methamphetamine (METH), an amphetamine derivate, may increase the risk of developing Parkinson's disease (PD). Human and animal studies have shown that METH produces persistent dopaminergic neurotoxicity in the nigrostriatal pathway, despite initial partial recovery. To determine the processes leading to early compensation, we studied the detailed morphology and distribution of tyrosine hydroxylase immunoreactive fibers (TH-ir) classified by their thickness (types I-IV) before and after METH. Applying three established neurotoxic regimens of METH: single high dose (1 × 30 mg/kg), multiple lower doses (3 × 5 mg/kg) or (3 × 10 mg/kg), we show that METH primarily damages type I fibers (the thinner ones), and to a much lesser extend types II-IV fibers including sterile axons. The striatal TH terminal partial recovery process, consisting of a progressive regrowth increases in types II, III, and IV fibers, demonstrated by co-localization of GAP-43, a sprouting marker, was observed 3 days post-METH treatment. In addition, we demonstrate the presence of growth-cone-like TH-ir structures, indicative of new terminal generation as well as improvement in motor functions after 3 days. A temporal relationship was observed between decreases in TH-expression and increases in silver staining, a marker of degeneration. Striatal regeneration was associated with an increase in astroglia and decrease in microglia expression, suggesting a possible role for the neuroimmune system in regenerative processes. Identification of regenerative compensatory mechanisms in response to neurotoxic agents could point to novel mechanisms in countering the neurotoxicity and/or enhancing the regenerative processes.

Neuroimmune and Inflammatory Signals in Complex Disorders of the Central Nervous System

An extensive microglial-astrocyte-monocyte-neuronal cross talk seems to be crucial for normal brain function, development, and recovery. However, under certain conditions neuroinflammatory interactions between brain cells and neuroimmune cells influence disease outcome and brain pathology. Microglial cells express a range of functional states with dynamically pleomorphic profiles from a surveilling status of synaptic transmission to an active player in major events of development such as synaptic elimination, regeneration, and repair. Also, inflammation mediates a series of neurotoxic roles in neuropsychiatric conditions and neurodegenerative diseases. The present review discusses data on the involvement of neuroinflammatory conditions that alter neuroimmune interactions in four different pathologies. In the first section of this review, we discuss the ability of the early developing brain to respond to a focal lesion with a rapid compensatory plasticity of intact axons and the role of microglial activation and proinflammatory cytokines in brain repair. In the second section, we present data of neuroinflammation and neurodegenerative disorders and discuss the role of reactive astrocytes in motor neuron toxicity and the progression of amyotrophic lateral sclerosis. In the third section, we discuss major depressive disorders as the consequence of dysfunctional interactions between neural and immune signals that result in increased peripheral immune responses and increase proinflammatory cytokines. In the last section, we discuss autism spectrum disorders and altered brain circuitries that emerge from abnormal long-term responses of innate inflammatory cytokines and microglial phenotypic dysfunctions.

Exercise-Induced Neuroprotection of the Nigrostriatal Dopamine System in Parkinson's Disease

Epidemiological studies indicate that physical activity and exercise may reduce the risk of developing Parkinson's disease (PD), and clinical observations suggest that physical exercise can reduce the motor symptoms in PD patients. In experimental animals, a profound observation is that exercise of appropriate timing, duration, and intensity can reduce toxin-induced lesion of the nigrostriatal dopamine (DA) system in animal PD models, although negative results have also been reported, potentially due to inappropriate timing and intensity of the exercise regimen. Exercise may also minimize DA denervation-induced medium spiny neuron (MSN) dendritic atrophy and other abnormalities such as enlarged corticostriatal synapse and abnormal MSN excitability and spiking activity. Taken together, epidemiological studies, clinical observations, and animal research indicate that appropriately dosed physical activity and exercise may not only reduce the risk of developing PD in vulnerable populations but also benefit PD patients by potentially protecting the residual DA neurons or directly restoring the dysfunctional cortico-basal ganglia motor control circuit, and these benefits may be mediated by exercise-triggered production of endogenous neuroprotective molecules such as neurotrophic factors. Thus, exercise is a universally available, side effect-free medicine that should be prescribed to vulnerable populations as a preventive measure and to PD patients as a component of treatment. Future research needs to establish standardized exercise protocols that can reliably induce DA neuron protection, enabling the delineation of the underlying cellular and molecular mechanisms that in turn can maximize exercise-induced neuroprotection and neurorestoration in animal PD models and eventually in PD patients.

Intrinsic Regenerative Ability of Mature CNS Neurons

A prevailing view in neuroscience is that the mature CNS has relatively little capacity to respond adaptively to injury. Recent data indicating a high degree of structural plasticity in the adult brain provides an impetus to reexamine how central neurons react to trauma. An analysis of both in vivo and in vitro experimental studies demonstrates that certain brain neurons may have an intrinsic ability to respond to structural injury by an attempt at regenerative sprouting. Indeed, aberrant sprouting following neuronal injury may be the cause of epilepsy following brain trauma and may underlie the neuronal changes stimulated by plaque formation in Alzheimer’s disease. An understanding of the stereotypical reaction to injury of different CNS neurons, as well as the role of nonneuronal cells, may provide new avenues for therapeutic intervention for a range of neurodegenerative diseases and “acquired” forms of CNS injury.

Effects of striatal transplantation of cells transfected with GDNF gene without pre- and pro-regions in mouse model of Parkinson's disease

Background

Previously, we have shown that transgenic cells bearing the GDNF gene with deleted pre- and pro-regions (mGDNF) can release transgenic GDNF. The medium conditioned by transgenic cells with mGDNF induced axonal growth in rat embryonic spinal ganglion in vitro. Here we demonstrate a neurotrophic effect of mGDNF on PC12 cells in vitro as well as its neuroprotective effect on dopaminergic neurons in the substantia nigra pars compacta in vivo as indicated by improved motor coordination and sleep-wakefulness cycle in the MPTP mouse model of Parkinson’s disease.

Results

HEK293 cells were transfected with a vector encoding an isoform of the human GDNF gene with deleted pre- and pro-regions (mGDNF). This factor in the medium conditioned by the transfected cells was shown to induce axonal growth in PC12 cells. The early Parkinson’s disease model was established by injection of the dopaminergic pro-neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) into C57Bl/6 mice. Transgenic HEK293/mGDNF/GFP cells were transplanted into the striatum (caudate-putamen) of experimental mice. The sleep-wakefulness cycle was studied by continuous EEG and motor activity monitoring 1 and 2 weeks after MPTP injection. After the experiment, the motor coordination of experimental animals was evaluated in the rotarod test, and dopaminergic neurons in the substantia nigra pars compacta were counted in cross-sections of the midbrain. MPTP administration lowered the number of tyrosine hydroxylase immunopositive cells in the substantia nigra pars compacta, decreased motor coordination, and increased the total wake time during the dark period. The transplantation of HEK293/mGDNF cells into the caudate-putamen 3 days prior to MPTP injection smoothed these effects, while the control transplantation of HEK293 cells showed no notable impact.

Conclusions

Transplantation of transgenic cells with the GDNF gene lacking the pre- and pro-sequences can protect dopaminergic neurons in the mouse midbrain from the subsequent administration of the pro-neurotoxin MPTP, which is confirmed by polysomnographic, behavioral and histochemical data. Hence it is released from transfected cells and preserves the differentiation activity and neuroprotective properties.

Targeting the CD80/CD86 costimulatory pathway with CTLA4-Ig directs microglia toward a repair phenotype and promotes axonal outgrowth

Among the costimulatory factors widely studied in the immune system is the CD28/cytotoxic T-lymphocyte antigen-4 (CTLA4)-CD80/CD86 pathway, which critically controls the nature and duration of the T-cell response. In the brain, up-regulated expression of CD80/CD86 during inflammation has consistently been reported in microglia. However, the role of CD80/CD86 molecules has mainly been studied in a context of microglia-T cell interactions in pathological conditions, while the function of CD80/CD86 in the regulation of intrinsic brain cells remains largely unknown. In this study, we used a transgenic pig line in which neurons express releasable CTLA4-Ig, a synthetic molecule mimicking CTLA4 and binding to CD80/CD86. The effects of CTLA4-Ig on brain cells were analyzed after intracerebral transplantation of CTLA4-Ig-expressing neurons or wild-type neurons as control. This model provided in vivo evidence that CTLA4-Ig stimulated axonal outgrowth, in correlation with a shift of the nearby microglia from a compact to a ramified morphology. In a culture system, we found that the CTLA4-Ig-induced morphological change of microglia was mediated through CD86, but not CD80. This was accompanied by microglial up-regulated expression of the anti-inflammatory molecule Arginase 1 and the neurotrophic factor BDNF, in an astrocyte-dependent manner through the purinergic P2Y1 receptor pathway. Our study identifies for the first time CD86 as a key player in the modulation of microglia phenotype and suggests that CTLA4-Ig-derived compounds might represent new tools to manipulate CNS microglia.

Topographical Distribution of Morphological Changes in a Partial Model of Parkinson's Disease--Effects of Nanoencapsulated Neurotrophic Factors Administration

Administration of various neurotrophic factors is a promising strategy against Parkinson's disease (PD). An intrastriatal infusion of 6-hydroxidopamine (6-OHDA) in rats is a suitable model to study PD. This work aims to describe stereological parameters regarding rostro-caudal gradient, in order to characterize the model and verify its suitability for elucidating the benefits of therapeutic strategies. Administration of 6-OHDA induced a reduction in tyrosine hidroxylase (TH) reactivity in the dorsolateral part of the striatum, being higher in the caudal section than in the rostral one. Loss of TH-positive neurons and axodendritic network was highly significant in the external third of substantia nigra (e-SN) in the 6-OHDA group versus the saline one. After the administration of nanospheres loaded with neurotrophic factors (NTF: vascular endothelial growth factor (VEGF) + glial cell line-derived neurotrophic factor (GDNF)), parkinsonized rats showed more TH-positive fibers than those of control groups; this recovery taking place chiefly in the rostral sections. Neuronal density and axodendritic network in e-SN was more significant than in the entire SN; the topographical analysis showed that the highest difference between NTF versus control group was attained in the middle section. A high number of bromodeoxyuridine (BrdU)-positive cells were found in sub- and periventricular areas in the group receiving NTF, where most of them co-expressed doublecortin. Measurements on the e-SN achieved more specific and significant results than in the entire SN. This difference in rostro-caudal gradients underpins the usefulness of a topological approach to the assessment of the lesion and therapeutic strategies. Findings confirmed the neurorestorative, neurogenic, and synergistic effects of VEGF+GDNF administration.

Roles for the TGFβ superfamily in the development and survival of midbrain dopaminergic neurons

The adult midbrain contains 75% of all dopaminergic neurons in the CNS. Within the midbrain, these neurons are divided into three anatomically and functionally distinct clusters termed A8, A9 and A10. The A9 group plays a functionally non-redundant role in the control of voluntary movement, which is highlighted by the motor syndrome that results from their progressive degeneration in the neurodegenerative disorder, Parkinson's disease. Despite 50 years of investigation, treatment for Parkinson's disease remains symptomatic, but an intensive research effort has proposed delivering neurotrophic factors to the brain to protect the remaining dopaminergic neurons, or using these neurotrophic factors to differentiate dopaminergic neurons from stem cell sources for cell transplantation. Most neurotrophic factors studied in this context have been members of the transforming growth factor β (TGFβ) superfamily. In recent years, an intensive research effort has focused on understanding the function of these proteins in midbrain dopaminergic neuron development and their role in the molecular architecture that regulates the development of this brain region, with the goal of applying this knowledge to develop novel therapies for Parkinson's disease. In this review, the current evidence showing that TGFβ superfamily members play critical roles in the regulation of midbrain dopaminergic neuron induction, differentiation, target innervation and survival during embryonic and postnatal development is analysed, and the implications of these findings are discussed.

Lentiviral vector-mediated gradients of GDNF in the injured peripheral nerve: effects on nerve coil formation, Schwann cell maturation and myelination

Although the peripheral nerve is capable of regeneration, only a small minority of patients regain normal function after surgical reconstruction of a major peripheral nerve lesion, resulting in a severe and lasting negative impact on the quality of life. Glial cell-line derived neurotrophic factor (GDNF) has potent survival- and outgrowth-promoting effects on motoneurons, but locally elevated levels of GDNF cause trapping of regenerating axons and the formation of nerve coils. This phenomenon has been called the “candy store” effect. In this study we created gradients of GDNF in the sciatic nerve after a ventral root avulsion. This approach also allowed us to study the effect of increasing concentrations of GDNF on Schwann cell proliferation and morphology in the injured peripheral nerve. We demonstrate that lentiviral vectors can be used to create a 4 cm long GDNF gradient in the intact and lesioned rat sciatic nerve. Nerve coils were formed throughout the gradient and the number and size of the nerve coils increased with increasing GDNF levels in the nerve. In the nerve coils, Schwann cell density is increased, their morphology is disrupted and myelination of axons is severely impaired. The total number of regenerated and surviving motoneurons is not enhanced after the distal application of a GDNF gradient, but increased sprouting does result in higher number of motor axon in the distal segment of the sciatic nerve. These results show that lentiviral vector mediated overexpression of GDNF exerts multiple effects on both Schwann cells and axons and that nerve coil formation already occurs at relatively low concentrations of exogenous GDNF. Controlled expression of GDNF, by using a viral vector with regulatable GDNF expression, may be required to avoid motor axon trapping and to prevent the effects on Schwann cell proliferation and myelination.

Activation of microglial cells triggers a release of brain-derived neurotrophic factor (BDNF) inducing their proliferation in an adenosine A2A receptor-dependent manner: A2A receptor blockade prevents BDNF release and proliferation of microglia

Background

Brain-derived neurotrophic factor (BDNF) has been shown to control microglial responses in neuropathic pain. Since adenosine A_2A receptors (A_2ARs) control neuroinflammation, as well as the production and function of BDNF, we tested to see if A_2AR controls the microglia-dependent secretion of BDNF and the proliferation of microglial cells, a crucial event in neuroinflammation.

Methods

Murine N9 microglial cells were challenged with lipopolysaccharide (LPS, 100 ng/mL) in the absence or in the presence of the A_2AR antagonist, SCH58261 (50 nM), as well as other modulators of A_2AR signaling. The BDNF cellular content and secretion were quantified by Western blotting and ELISA, A_2AR density was probed by Western blotting and immunocytochemistry and cell proliferation was assessed by BrdU incorporation. Additionally, the A_2AR modulation of LPS-driven cell proliferation was also tested in primary cultures of mouse microglia.

Results

LPS induced time-dependent changes of the intra- and extracellular levels of BDNF and increased microglial proliferation. The maximal LPS-induced BDNF release was time-coincident with an LPS-induced increase of the A_2AR density. Notably, removing endogenous extracellular adenosine or blocking A_2AR prevented the LPS-mediated increase of both BDNF secretion and proliferation, as well as exogenous BDNF-induced proliferation.

Conclusions

We conclude that A_2AR activation plays a mandatory role controlling the release of BDNF from activated microglia, as well as the autocrine/paracrine proliferative role of BDNF.

Activated immune cells in Parkinson's disease

Recently, an interaction between neurodegenerative processes and the innate and adaptive immune responses has been increasingly recognized. Activation of microglia, infiltration of peripheral T lymphocytes, and T-cell interaction with microglia may strongly affect the progression of Parkinson's disease (PD) both in patients and in animal models of the disease. Here, we summarize the current knowledge regarding the role of microglia in the progression of PD. The plasticity of the microglial response is also discussed in the context of PD. In addition, we also focus on the influence of several peripheral T-cell subsets on PD progression as well as on possible pathways by which they might act. This review should help increase our understanding of the effects of innate and adaptive immune cells in the pathogenesis of PD.

Circulating levels of brain-derived neurotrophic factor: correlation with mood, cognition and motor function

Brain-derived neurotrophic factor (BDNF) is the most widely distributed neurotrophin in the CNS, where it plays several pivotal roles in synaptic plasticity and neuronal survival. As a consequence, BDNF has become a key target in the physiopathology of several neurological and psychiatric diseases. Recent studies have consistently reported altered levels of BDNF in the circulation (i.e., serum or plasma) of patients with major depression, bipolar disorder, Alzheimer's disease, Huntington's disease and Parkinson's disease. Correlations between serum BDNF levels and affective, cognitive and motor symptoms have also been described. BDNF appears to be an unspecific biomarker of neuropsychiatric disorders characterized by neurodegenerative changes.

Estrogen reduces BDNF level, but maintains dopaminergic cell density in the striatum of MPTP mouse model

Degeneration of dopaminergic (DA) axons in the striatum triggers upregulation of striatal trophic activity and striatal DA neuronal number in animal models of Parkinson's disease (PD). The present study investigated the effects of 17beta-estradiol (E2) on brain-derived neurotrophic factor (BDNF) expression and the density of DA neurons in the striatum of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model in correlation with nigrostriatal DA innervation. Adult male C57Bl/6 mice were treated with E2 or vehicle for 11 days. Following 5 days of E2 or vehicle pretreatment, animals were injected with MPTP on day 6. On day 11, all mice were sacrificed, and the striatum were collected and processed for tyrosine hydroxylase (TH) and BDNF immunohistochemistry. Striatal TH-immunoreactive (IR) neurons were counted. Extent of DA innervation and BDNF expression in the striatum were assessed by measuring optical density of TH and BDNF immunoreactivity, respectively. Pretreatment with E2 partially prevented DA denervation and decreased striatal BDNF upregulation triggered by MPTP, but maintained the density of striatal TH-IR neurons to that observed in MPTP group. These findings suggest that estrogen protection of nigrostriatal DA axons against MPTP as well as preservation of the striatal TH-IR cell density in MPTP/E2 mice may be not mediated by BDNF.

Depression: a repair response to stress-induced neuronal microdamage that can grade into a chronic neuroinflammatory condition?

Depression is a major contributor to the global burden of disease and disability, yet it is poorly understood. Here we review data supporting a novel theoretical model for the biology of depression. In this model, a stressful life event leads to microdamage in the brain. This damage triggers an injury repair response consisting of a neuroinflammatory phase to clear cellular debris and a spontaneous tissue regeneration phase involving neurotrophins and neurogenesis. During healing, released inflammatory mediators trigger sickness behavior and psychological pain via mechanisms similar to those that produce physical pain during wound healing. The depression remits if the neuronal injury repair process resolves successfully. Importantly, however, the acute psychological pain and neuroinflammation often transition to chronicity and develop into pathological depressive states. This hypothesis for depression explains substantially more data than alternative models, including why emerging data show that analgesic, anti-inflammatory, pro-neurogenic and pro-neurotrophic treatments have antidepressant effects. Thus, an acute depressive episode can be conceptualized as a normally self-limiting but highly error-prone process of recuperation from stress-triggered neuronal microdamage.

9-Methyl-beta-carboline has restorative effects in an animal model of Parkinson's disease

In a previous study, a primary culture of midbrain cells was exposed to 9-methyl-beta-carboline for 48 h, which caused an increase in the number of tyrosine hydroxylase-positive cells. Quantitative RT-PCR revealed increased transcription of genes participating in the maturation of dopaminergic neurons. These in vitro findings prompted us to investigate the restorative actions of 9-methyl-beta-carboline in vivo. The compound was delivered for 14 days into the left cerebral ventricle of rats pretreated with the neurotoxin 1-methyl-4-phenyl-pyridinium ion (MPP+) for 28 days applying a dose which lowered dopamine by approximately 50%. Interestingly, 9-methyl-beta-carboline reversed the dopamine-lowering effect of the neurotoxin in the left striatum. Stereological counts of tyrosine hydroxylase-immunoreactive cells in the substantia nigra revealed that the neurotoxin caused a decrease in the number of those cells. However, when treated subsequently with 9-methyl-beta-carboline, the number reached normal values. In search of an explanation for the restorative activity, we analyzed the complexes that compose the respiratory chain in striatal mitochondria by 2-dimension gel electrophoresis followed by MALDI-TOF peptide mass fingerprinting.We found no changes in the overall composition of the complexes. However, the activity of complex I was increased by approximately 80% in mitochondria from rats treated with MPP+ and 9-methyl-beta-carboline compared to MPP+ and saline and to sham-operated rats, as determined by measurements of nicotinamide adenine dinucleotide dehydrogenase activity. Microarray technology and single RT-PCR revealed the induction of neurotrophins: brain-derived neurotrophic factor, conserved dopamine neurotrophic factor, cerebellin 1 precursor protein, and ciliary neurotrophic factor. Selected western blots yielded consistent results. The findings demonstrate restorative effects of 9-methyl-beta-carboline in an animal model of Parkinson's disease that improve the effectiveness of the respiratory chain and promote the transcription and expression of neurotrophin-related genes.

Long-term gliosis and molecular changes in the cervical spinal cord of the rhesus monkey after traumatic brain injury

Recovery of fine motor skills after traumatic brain injury (TBI) is variable, with some patients showing progressive improvements over time while others show poor recovery. We therefore studied possible cellular mechanisms accompanying the recovery process in a non-human primate model system, in which the lateral frontal motor cortex areas controlling the preferred upper limb were unilaterally lesioned, and the animals eventually regained fine hand motor function. Immunohistochemical staining of the cervical spinal cord, the site of compensatory sprouting and degeneration of corticospinal axons, showed profound increases in immunoreactivities for major histocompatibility complex class II molecule (MHC-II) and extracellular signal-regulated kinases (ERK1/2) up to 12 months post lesion, particularly within the lateral corticospinal tract (LCST). Double immunostaining demonstrated that phosphorylated ERK1/2 colocalized within the MCH-II + microglia, suggesting a trophic role of long-term microglia activation after TBI at the site of compensatory sprouting. Active sprouting was observed in the LCST as well as in the spinal gray matter of the lesioned animals, as illustrated by increases in growth associated protein 43. Upregulation of Nogo receptor and glutamate transporter expression was also observed in this region after TBI, suggesting possible mechanisms for controlling aberrant sprouting and/or synaptic formation en route and interstitial glutamate concentration changes at the site of axon degeneration, respectively. Taken together, these changes in the non-human primate spinal cord support a long-term trophic/tropic role for reactive microglia, in particular, during functional and structural recovery after TBI.

Adaptive immune regulation of glial homeostasis as an immunization strategy for neurodegenerative diseases

Neurodegenerative diseases, notably Alzheimer's and Parkinson's diseases, are amongst the most devastating disorders afflicting the elderly. Currently, no curative treatments or treatments that interdict disease progression exist. Over the past decade, immunization strategies have been proposed to combat disease progression. Such strategies induce humoral immune responses against misfolded protein aggregates to facilitate their clearance. Robust adaptive immunity against misfolded proteins, however, accelerates disease progression, precipitated by induced effector T cell responses that lead to encephalitis and neuronal death. Since then, mechanisms that attenuate such adaptive neurotoxic immune responses have been sought. We propose that shifting the balance between effector and regulatory T cell activity can attenuate neurotoxic inflammatory events. This review summarizes advances in immune regulation to achieve a homeostatic glial response for therapeutic gain. Promising new ways to optimize immunization schemes and measure their clinical efficacy are also discussed.

Pericontusion axon sprouting is spatially and temporally consistent with a growth-permissive environment after traumatic brain injury

We previously reported that pericontusional extracellular chondroitin sulfate proteoglycans (CSPGs) are profoundly reduced for 3 weeks after experimental traumatic brain injury, indicating a potential growth-permissive window for plasticity. Here, we investigate the extracellular environment of sprouting neurons after controlled cortical impact injury in adult rats to determine the spatial and temporal arrangement of inhibitory and growth-promoting molecules in relation to growth-associated protein 43-positive (GAP43+) neurons. Spontaneous cortical sprouting was maximal in pericontused regions at 7 and 14 days after injury but absent by 28 days. Perineuronal nets containing CSPGs were reduced at 7 days after injury in the pericontused region (p < 0.05), which was commensurate with a reduction in extracellular CSPGs. Sprouting was restricted to the perineuronal nets and CSPG-deficient regions at 7 days, indicating that the pericontused region is temporarily and spatially permissive to new growth. At this time point,GAP43+ neurons were associated with brain regions containing cells positive for polysialic acid neural cell adhesion molecule but not with fibronectin-positive cells. Brain-derived neurotrophic factor was reduced in the immediate pericontused region at 7 days. Along with prior Western blot evidence, these data suggest that a lowered intrinsic growth stimulus, together with a later return of growth-inhibitory CSPGs, may contribute to the ultimate disappearance of sprouting neurons after traumatic brain injury.

Control of neuroinflammation as a therapeutic strategy for amyotrophic lateral sclerosis and other neurodegenerative disorders

Neurodegenerative diseases, Alzheimer's and Parkinson's diseases, and amyotrophic lateral sclerosis (ALS) are progressive and devastating disorders of the nervous system without cure. Although a number of distinct, but not mutually exclusive, mechanisms can affect disease pathogenesis, neuroinflammation stands in common. Neuroinflammatory responses occur as a consequence of oxidative and excitotoxic neuronal damage, mitochondrial dysfunction, and protein aggregation. Thus, it is believed drugs that modulate inflammation may combat disease progression. Such strategies include those commented on in the report by Arie Neymotin et al. demonstrating lenalidomide's anti-inflammatory and neuroprotective responses in the G93A mutant superoxide dismutase-1 mouse model of ALS (Neymotin et al., 2009). While anti-inflammatory interventions may be required, they may not be sufficient to positively affect clinical outcomes. The targeting of combinations of pathogenic events including clearance of disaggregated proteins together with neuroprotective and immune modulatory strategies may all be required to facilitate positive therapeutic outcomes. This may include the targeting of both innate and adaptive neurotoxic immune responses. This commentary is designed to summarize the promises and perils in achieving immunoregulation for brain homeostatic responses and inevitable therapeutic gain. Promising new ways to optimize immunization schemes and measure their clinical efficacy are discussed with a particular focus on ALS.

Increased glial-derived neurotrophic factor in the small intestine of rats infected with the tapeworm, Hymenolepis diminuta

The neurotrophin, glial-derived neurotrophic factor (GDNF), is essential for the development of the enteric nervous system (ENS) in both the embryo and neonate and may be important for maintenance and plasticity of ENS. The tapeworm, Hymenolepis diminuta, altered the number of cells containing GNDF in the host's jejunum and ileum. Numbers and locations of GDNF-containing cells were determined by applying monoclonal anti-GDNF antibody to intestinal segments collected from infected and uninfected age-matched rats during the initial 34 days post-infection (dpi). Most cells staining positive for GDNF were present in the lamina propria of the jejunum and ileum from both infected and uninfected rats. The co-localization of staining by the antibodies, anti-GDNF and anti-ED2 (a nuclear specific antibody for resident macrophages) indicated that at least 74% of the cells staining for GDNF were macrophages. Mast cells did not stain with the anti-GDNF antibody. The increased number of GDNF+ cells in the infected rat intestine suggests that this neurotrophin may play a role in the neural and mucosal responses to lumenal tapeworm infection.

Morphophysiology of the Zuckerkandl's paraganglion: effects of dexamethasone and aging

The extra-adrenal Zuckerkandl's paraganglion is used as a source of chromaffin cells for transplantation in parkinsonian animals. Aging can affect its viability, and this tissue needs further characterization for improving grafting procedures. The objectives were: (i) to compare the main morpho-functional characteristics of prepubertal and old Zuckerkandl's paraganglion (ZP), and (ii) to discern phenotypic changes after sub-chronic dexamethasone treatment in extra-adrenal tissue of prepubertal rats. For these purposes, immunostaining methods, stereology, voltammetry, cell culture, Western blotting, and ELISA were employed. The findings revealed that all paraganglia were composed of mesenchymal tissue and chromaffin cells. In prepubertal rats, chromaffin cells are arranged as large or small clusters. Large clusters (also known as "cell nests") contain densely packed chromaffin cells, and they are seen as fascicles in longitudinal sections. In old paraganglia, cell nests disappear, and chromaffin cells are found to be arranged as small cell clusters or dispersed throughout the mesenchyma. Paraganglionic chromaffin cells possess a rounded morphology with diameter ranging from 12 to 15 μm, with intracytoplasmic granules (100-500 nm in diameter) containing catecholamines. Prepubertal and old ZP chromaffin cells are mostly noradrenergics, and a few of them are dopaminergics. Aging reduces the amount of chromaffin tissue (28% in adult rats vs. 11% in old animals, both in relation to total volume of the paraganglion), and induces the presence of adrenergic cells and adrenaline. Both prepubertal and old cells express the neurotrophic factors GDNF and TGF-β₁, aging leading to reduced levels of both growth factors. Dexamethasone (50 μg/kg daily, 5 days) leads to the expression of phenylethanolamine-N-methyl-transferase in prepubertal paraganglia, and to a higher content and release of adrenaline.

Comparison of inflammation in the brain and spinal cord following mechanical injury

Inflammation in the CNS predominantly involves microglia and macrophages, and is believed to be a significant cause of secondary injury following trauma. This study compares the microglial and macrophage response in the rat brain and spinal cord following discrete mechanical injury to better appreciate the degree to which these cells could contribute to secondary damage in these areas. We find that, 1 week after injury, the microglial and macrophage response is significantly greater in the spinal cord compared to the brain. This is the case for injuries to both gray and white matter. In addition, we observed a greater inflammatory response in white matter compared to gray matter within both the brain and spinal cord. Because activated microglia and macrophages appear to be effectors of secondary damage, a greater degree of inflammation in the spinal cord is likely to result in more extensive secondary damage. Tissue saving strategies utilizing anti-inflammatory treatments may therefore be more useful in traumatic spinal cord than brain injury.

Dynamic changes in nerve growth factor and substance P in the murine hair cycle induced by depilation

Increasing evidence suggests that various neurotrophins and neuropeptides play an important role in the progression of hair follicle cycling. Among them, nerve growth factor (NGF) and substance P (SP) have attracted special interest recently. However, the interaction between these factors during hair cycling has not yet been systematically studied. We therefore investigated the mutual relationships between NGF and SP and the mechanism by which the anagen stage of the hair cycle is initiated. Fluctuations in numbers of SP-positive nerve fibers and variations in amounts of SP, NGF, and another neurotrophic factor, glial cell-derived neurotrophic factor, in skin in the C57BL/6 mouse depilation-induced hair cycle model, together with the spatiotemporal expression patterns of each of these factors, were followed simultaneously by enzyme-linked immunosorbent assay and immunohistochemistry. The main finding was that a surge in NGF expression and a rapid increase in NGF content in skin is an initial event within 1 day after depilation, followed by elevation of SP content and numbers of SP-containing fibers 2 days after the increase in NGF. Our findings suggest that a rapid and abundant increase in NGF plays a key role in the induction and progression of anagen hair cycling through keratinocyte growth promotion. NGF may also induce plastic changes such as sprouting and hyperplasia in dermal nerve fibers and enhance their SP production. Elevated levels of SP in skin may additionally contribute to the progression of consecutive anagen hair cycles.

The role of Ret receptor tyrosine kinase in dopaminergic neuron development

Glial cell line-derived neurotrophic factor (GDNF) is one of the most potent trophic factors identified for promoting survival and function of dopaminergic (DA) neurons in the midbrain. Ret, a member of the receptor tyrosine kinase (RTK) superfamily transduces GDNF signaling. The role of Ret in the development of DA neurons is not clear however. Here we demonstrate the involvement of Ret in the DA neuron development both in vitro and in vivo. The dopamine transporter (DAT) gene was clearly induced in rat embryonic neural precursors that had been transfected with Ret. Temporary blockade of Ret expression in embryos using Ret antisense oligonucleotides (Ret-AS-ODN) in vivo led to reduced striatal DA content and a decrease of tyrosine hydroxylase (TH) positive fibers in the striatum. Additionally, some DA neurons in the substantia nigra (SN) underwent apoptotic cell death following the Ret-AS-ODN treatment. Taken together, the data suggest that normal function of Ret is required in vivo for the maturation of DA neurons, in particular for cell survival and fiber innervation. We further demonstrated Ret-induced expression of DAT in vitro.

Nogo-A-deficient mice reveal strain-dependent differences in axonal regeneration

Nogo-A, a membrane protein enriched in myelin of the adult CNS, inhibits neurite growth and regeneration; neutralizing antibodies or receptor blockers enhance regeneration and plasticity in the injured adult CNS and lead to improved functional outcome. Here we show that Nogo-A-specific knock-outs in backcrossed 129X1/SvJ and C57BL/6 mice display enhanced regeneration of the corticospinal tract after injury. Surprisingly, 129X1/SvJ Nogo-A knock-out mice had two to four times more regenerating fibers than C57BL/6 Nogo-A knock-out mice. Wild-type newborn 129X1/SvJ dorsal root ganglia in vitro grew a much higher number of processes in 3 d than C57BL/6 ganglia, confirming the stronger endogenous neurite growth potential of the 129X1/SvJ strain. cDNA microarrays of the intact and lesioned spinal cord of wild-type as well as Nogo-A knock-out animals showed a number of genes to be differentially expressed in the two mouse strains; many of them belong to functional categories associated with neurite growth, synapse formation, and inflammation/immune responses. These results show that neurite regeneration in vivo, under the permissive condition of Nogo-A deletion, and neurite outgrowth in vitro differ significantly in two widely used mouse strains and that Nogo-A is an important endogenous inhibitor of axonal regeneration in the adult spinal cord.

Localization of nerve growth factor, neurotrophin-3, and glial cell line-derived neurotrophic factor in nestin-expressing reactive astrocytes in the caudate-putamen of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated C57/Bl mice

To address the hypothesis that reactive astrocytes in the basal ganglia of an animal model of Parkinson's disease serve neurotrophic roles, we studied the expression pattern of neurotrophic factors in the basal ganglia of C57/Bl mice that had been treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to induce the degeneration of nigral dopamine neurons and parkinsonism. MPTP induced significant neuronal degeneration in the substantia nigra pars compacta as detected with Fluoro-Jade B staining, and this was accompanied by an increase in nestin-expressing astrocytes within the caudate-putamen. The number of nestin-positive reactive astrocytes in the caudate-putamen peaked within 3-5 days following MPTP treatment and then declined progressively toward the basal level by 21 days after treatment. Immunofluorescence and confocal microscopy confirmed coexpression of nestin or Ki-67 (cell proliferation marker) in glial fibrillary acid protein-positive astrocytes in the caudate-putamen. Double immunolabeling further revealed immunoreactivities for nerve growth factor (NGF), neurotrophin-3 (NT3), and glial cell line-derived neurotrophic factor (GDNF) in nestin-positive reactive astrocytes. Semiquantification of data obtained from mice 5 days after MPTP injection indicated that the majority of nestin-expressing cells expressed NGF (92%), NT3 (90%), or GDNF (86%). Our results present novel evidence of neurotrophic features among reactive astrocytes in the dopamine-depleted striatum. These nestin-expressing reactive astrocytes may therefore play neurotrophic roles in neural remodeling of the basal ganglia in Parkinson's disease.

Dopaminergic innervation of the human striatum in Parkinson's disease

In Parkinson's disease (PD), dopaminergic input to the caudate nucleus and a band of putaminal tissue abutting the external globus pallidus seems well preserved on immunohistochemical staining for the dopamine transporter. Counting of dopaminergic terminals showed that terminal density in these regions in PD was the same as that in controls, which indicates that input is truly preserved and not a consequence of a compensatory upregulation of metabolism in a reduced pool of surviving terminals. When the branching pattern of dopaminergic axons coursing through the globus pallidus was examined, we found no evidence for increased axonal sprouting in PD that might have contributed to preservation of dopaminergic input to the putamen or caudate nucleus. Although terminal counting indicated that anatomic input was preserved to parts of the striatum, dopamine uptake site density in these regions was reduced significantly. This suggests that the impact of disease in these areas is more profound than was thought previously.

Combination of hTERT and bmi-1, E6, or E7 induces prolongation of the life span of bone marrow stromal cells from an elderly donor without affecting their neurogenic potential

Murine bone marrow stromal cells differentiate not only into mesodermal derivatives, such as osteocytes, chondrocytes, adipocytes, skeletal myocytes, and cardiomyocytes, but also into neuroectodermal cells in vitro. Human bone marrow stromal cells are easy to isolate but difficult to study because of their limited life span. To overcome this problem, we attempted to prolong the life span of bone marrow stromal cells and investigated whether bone marrow stromal cells modified with bmi-1, hTERT, E6, and E7 retained their differentiated capability, or multipotency. In this study, we demonstrated that the life span of bone marrow stromal cells derived from a 91-year-old donor could be extended and that the stromal cells with an extended life span differentiated into neuronal cells in vitro. We examined the neuronally differentiated cells morphologically, physiologically, and biologically and compared the gene profiles of undifferentiated and differentiated cells. The neuronally differentiated cells exhibited characteristics similar to those of midbrain neuronal progenitors. Thus, the results of this study support the possible use of autologous-cell graft systems to treat central nervous system diseases in geriatric patients.

Inhibiting BDNF expression by antisense oligonucleotide infusion causes loss of nigral dopaminergic neurons

Brain derived neurotrophic factor (BDNF) expression is significantly reduced in the Parkinson's disease substantia nigra. This neurotrophin has potent affects on dopaminergic neuron survival protecting them from the neurotoxins MPTP and 6-hydroxydopamine (6-OHDA) commonly used to create animal models of Parkinson's disease and also promoting dopaminergic axonal sprouting. In this study, we demonstrate that an antisense oligonucleotide infusion (200 nM for 28 days) to prevent BDNF production in the substantia nigra of rats mimics many features of the classical animal models of Parkinson's disease. 62% of antisense treated rats rotate (P < or = 0.05) in response to dopaminergic receptor stimulation by apomorphine. 40% of substantia nigra pars compacta tyrosine hydroxylase immunoreactive neurons are lost (P < or = 0.00001) and dopamine uptake site density measured by (3)H-mazindol autoradiography is reduced by 34% (P < or = 0.005). Loss of haematoxylin and eosin stained nigral neurons is significant (P < or = 0.0001) but less extensive (34%). These observations indicate that loss of BDNF expression leads both to down regulation of the dopaminergic phenotype and to dopaminergic neuronal death. Therefore, reduced BDNF mRNA expression in Parkinson's disease substantia nigra may contribute directly to the death of nigral dopaminergic neurons and the development of Parkinson's disease.