BDNF-, IGF-1- and GDNF-secreting human neural progenitor cells rescue amyloid β-induced toxicity in cultured rat septal neurons

NSPCs-ES: mechanisms and functional impact on central nervous system diseases

Patients with central neuronal damage may suffer severe consequences, but effective therapies remain unclear. Previous research has established the transplantation of neural stem cells that generate new neurons to replace damaged ones. In a new field of scientific research, the extracellular secretion of NPSCs (NSPCs-ES) has been identified as an alternative to current chemical drugs. Many preclinical studies have shown that NSPCs-ES are effective in models of various central nervous system diseases (CNS) injuries, from maintaining functional structures at the cellular level to providing anti-inflammatory functions at the molecular level, as well as improving memory and motor functions, reducing apoptosis in neurons, and mediating multiple signaling pathways. The NSPC-ES can travel to the damaged tissue and exert a broad range of therapeutic effects by supporting and nourishing damaged neurons. However, gene editing and cell engineering techniques have recently improved therapeutic efficacy by modifying NSPCs-ES. Consequently, future research and application of NSPCs-ES may provide a novel strategy for the treatment of CNS diseases in the future. In this review, we summarize the current progress on these aspects.

TrkB-dependent regulation of molecular signaling across septal cell types

The lateral septum (LS), a GABAergic structure located in the basal forebrain, is implicated in social behavior, learning, and memory. We previously demonstrated that expression of tropomyosin kinase receptor B (TrkB) in LS neurons is required for social novelty recognition. To better understand molecular mechanisms by which TrkB signaling controls behavior, we locally knocked down TrkB in LS and used bulk RNA-sequencing to identify changes in gene expression downstream of TrkB. TrkB knockdown induces upregulation of genes associated with inflammation and immune responses, and downregulation of genes associated with synaptic signaling and plasticity. Next, we generated one of the first atlases of molecular profiles for LS cell types using single nucleus RNA-sequencing (snRNA-seq). We identified markers for the septum broadly, and the LS specifically, as well as for all neuronal cell types. We then investigated whether the differentially expressed genes (DEGs) induced by TrkB knockdown map to specific LS cell types. Enrichment testing identified that downregulated DEGs are broadly expressed across neuronal clusters. Enrichment analyses of these DEGs demonstrated that downregulated genes are uniquely expressed in the LS, and associated with either synaptic plasticity or neurodevelopmental disorders. Upregulated genes are enriched in LS microglia, associated with immune response and inflammation, and linked to both neurodegenerative disease and neuropsychiatric disorders. In addition, many of these genes are implicated in regulating social behaviors. In summary, the findings implicate TrkB signaling in the LS as a critical regulator of gene networks associated with psychiatric disorders that display social deficits, including schizophrenia and autism, and with neurodegenerative diseases, including Alzheimer's.

TrkB-dependent regulation of molecular signaling across septal cell types

The lateral septum (LS), a GABAergic structure located in the basal forebrain, is implicated in social behavior, learning and memory. We previously demonstrated that expression of tropomyosin kinase receptor B (TrkB) in LS neurons is required for social novelty recognition. To better understand molecular mechanisms by which TrkB signaling controls behavior, we locally knocked down TrkB in LS and used bulk RNA-sequencing to identify changes in gene expression downstream of TrkB. TrkB knockdown induces upregulation of genes associated with inflammation and immune responses, and downregulation of genes associated with synaptic signaling and plasticity. Next, we generated one of the first atlases of molecular profiles for LS cell types using single nucleus RNA-sequencing (snRNA-seq). We identified markers for the septum broadly, and the LS specifically, as well as for all neuronal cell types. We then investigated whether the differentially expressed genes (DEGs) induced by TrkB knockdown map to specific LS cell types. Enrichment testing identified that downregulated DEGs are broadly expressed across neuronal clusters. Enrichment analyses of these DEGs demonstrated that downregulated genes are uniquely expressed in the LS, and associated with either synaptic plasticity or neurodevelopmental disorders. Upregulated genes are enriched in LS microglia, associated with immune response and inflammation, and linked to both neurodegenerative disease and neuropsychiatric disorders. In addition, many of these genes are implicated in regulating social behaviors. In summary, the findings implicate TrkB signaling in the LS as a critical regulator of gene networks associated with psychiatric disorders that display social deficits, including schizophrenia and autism, and with neurodegenerative diseases, including Alzheimer's.

Anti-Amyloid Immunotherapies for Alzheimer's Disease: A 2023 Clinical Update

The amyloid cascade hypothesis is a useful framework for therapeutic development in Alzheimer's disease (AD). Amyloid b1-42 (Aβ) has been the main target of experimental therapies, based on evidence of the neurotoxic effects of Aβ, and of the potential adverse effects of brain Aβ burden detected in humans in vivo by positron emission tomography (PET). Progress on passive anti-amyloid immunotherapy research includes identification of antibodies that facilitate microglial activation, catalytical disaggregation, and increased flow of Aβ from cerebrospinal fluid (CSF) to plasma, thus decreasing the neurotoxic effects of Aβ. Recently completed phase 2 and 3 trials of 3rd generation anti-amyloid immunotherapies are supportive of their clinical efficacy in reducing brain Aβ burden and preventing cognitive decline. Data from recent trials implicate these agents as the first effective disease-modifying therapies against AD and has led to the US Food and Drug Administration (FDA) recent approval of aducanumab and lecanemab, under an accelerated approval pathway. The clinical effects of these agents are modest, however, and associated with amyloid-related imaging abnormalities (ARIA). Testing the effects of anti-Aβ immunotherapies in pre-symptomatic populations and identification of more potent and safer agents is the scope of ongoing and future research. Innovations in clinical trial design will be the key for the efficient and equitable development of novel anti-Aβ immunotherapies. The progress in the field of AD therapeutics will bring new clinical, logistical, and ethical challenges, which pose to revolutionize the practice of neurology, dementia care, and preventive cognitive healthcare.

Cell non-autonomous regulation of cerebrovascular aging processes by the somatotropic axis

Age-related cerebrovascular pathologies, ranging from cerebromicrovascular functional and structural alterations to large vessel atherosclerosis, promote the genesis of vascular cognitive impairment and dementia (VCID) and exacerbate Alzheimer's disease. Recent advances in geroscience, including results from studies on heterochronic parabiosis models, reinforce the hypothesis that cell non-autonomous mechanisms play a key role in regulating cerebrovascular aging processes. Growth hormone (GH) and insulin-like growth factor 1 (IGF-1) exert multifaceted vasoprotective effects and production of both hormones is significantly reduced in aging. This brief overview focuses on the role of age-related GH/IGF-1 deficiency in the development of cerebrovascular pathologies and VCID. It explores the mechanistic links among alterations in the somatotropic axis, specific macrovascular and microvascular pathologies (including capillary rarefaction, microhemorrhages, impaired endothelial regulation of cerebral blood flow, disruption of the blood brain barrier, decreased neurovascular coupling, and atherogenesis) and cognitive impairment. Improved understanding of cell non-autonomous mechanisms of vascular aging is crucial to identify targets for intervention to promote cerebrovascular and brain health in older adults.

Brain-Derived Neurotropic Factor in Neurodegenerative Disorders

Globally, neurodegenerative diseases cause a significant degree of disability and distress. Brain-derived neurotrophic factor (BDNF), primarily found in the brain, has a substantial role in the development and maintenance of various nerve roles and is associated with the family of neurotrophins, including neuronal growth factor (NGF), neurotrophin-3 (NT-3) and neurotrophin-4/5 (NT-4/5). BDNF has affinity with tropomyosin receptor kinase B (TrKB), which is found in the brain in large amounts and is expressed in several cells. Several studies have shown that decrease in BDNF causes an imbalance in neuronal functioning and survival. Moreover, BDNF has several important roles, such as improving synaptic plasticity and contributing to long-lasting memory formation. BDNF has been linked to the pathology of the most common neurodegenerative disorders, such as Alzheimer’s and Parkinson’s disease. This review aims to describe recent efforts to understand the connection between the level of BDNF and neurodegenerative diseases. Several studies have shown that a high level of BDNF is associated with a lower risk for developing a neurodegenerative disease.

Effect of High Intensity Power Training on Cognitive Function in Older Adults with Type 2 Diabetes: Secondary Outcomes of the GREAT2DO Study

We sought to determine the effects of 12 months of power training on cognition, and whether improvements in body composition, muscle strength, and/or aerobic capacity (VO_2peak) were associated with improvements in cognition in older adults with type 2 diabetes (T2D). Participants with T2D were randomized to power training or low-intensity sham exercise control condition, 3 days per week for 12 months. Cognitive outcomes included memory, attention/speed, executive function, and global cognition. Other relevant outcomes included VO_2peak, strength, and whole body and regional body composition. One hundred and three adults with T2D (mean age 67.9 years; standard deviation [SD] 5.9; 50.5% women) were enrolled and analyzed. Unexpectedly, there was a nearly significant improvement in global cognition (p = .05) in the sham group relative to power training, although both groups improved over time (p < .01). There were significant interactions between group allocation and body composition or muscle strength in the models predicting cognitive changes. Therefore, after stratifying by group allocation, improvements in immediate memory were associated with increases in relative skeletal muscle mass (r = 0.38, p = .03), reductions in relative body fat (r = −0.40, p = .02), and increases in knee extension strength were directly related to changes in executive function (r = −0.41, p = .02) within the power training group. None of these relationships were present in the sham group (p > .05). Although power training did not significantly improve cognition compared to low-intensity exercise control, improvements in cognitive function in older adults were associated with hypothesized improvements in body composition and strength after power training.

Functionalized nanoparticles for brain targeted BDNF gene therapy to rescue Alzheimer's disease pathology in transgenic mouse model

Brain-derived neurotrophic factor (BDNF) is actively produced and utilized in cortical circuits throughout life to sustain neuronal function and synaptic plasticity. In animal models of Alzheimer's Disease (AD), highly invasive BDNF gene therapy using viral vectors has successfully shown enhanced synaptic protein expression, proliferation of neurons and attenuation of amyloidogenic processes. However, to eliminate virus-related safety issues and invasive procedures, our present study has explored brain-targeted lipid-based nanoparticles that can deliver plasmid encoding BDNF to brain in a safe and efficient manner. Efficacy of these nanoparticles was tested in early (6-months) and advanced stage (9-months) transgenic APP/PS1 AD mice. Liposomes were surface-functionalized with brain targeting ligand, mannose, and cell-penetrating peptides (rabies virus-derived peptide or penetratin). These bifunctionalized nanoparticles enhanced BDNF expression by ~2 times and resulted in >40% (p < 0.05) reduction in toxic amyloid-beta peptides in 6- and 9-months old APP/PS1 mice brains compared to their age-matched untreated controls. Plaque load was reduced ~7 and ~3 times (p < 0.05), respectively, whereas synaptic proteins, synaptophysin and PSD-95, were found to be increased >90% (p < 0.05) in both age groups of transgenic mice treated with bifunctionalized nanoparticles. No untoward adverse effects were observed throughout treatment, suggesting a safe and effective strategy to rescue AD pathology.

All roads lead to Rome - a review of the potential mechanisms by which exerkines exhibit neuroprotective effects in Alzheimer's disease

Age-related neurodegenerative disorders such as Alzheimer’s disease (AD) have become a critical public health issue due to the significantly extended human lifespan, leading to considerable economic and social burdens. Traditional therapies for AD such as medicine and surgery remain ineffective, impractical, and expensive. Many studies have shown that a variety of bioactive substances released by physical exercise (called “exerkines”) help to maintain and improve the normal functions of the brain in terms of cognition, emotion, and psychomotor coordination. Increasing evidence suggests that exerkines may exert beneficial effects in AD as well. This review summarizes the neuroprotective effects of exerkines in AD, focusing on the underlying molecular mechanism and the dynamic expression of exerkines after physical exercise. The findings described in this review will help direct research into novel targets for the treatment of AD and develop customized exercise therapy for individuals of different ages, genders, and health conditions.

Morin attenuates memory deficits in a rat model of Alzheimer's disease by ameliorating oxidative stress and neuroinflammation

This study aimed to investigate the effect of flavonoid morin on oxidative/nitrosative stress, neuroinflammation, and histological, molecular, and behavioral changes caused by amyloid-beta (Aβ)_1-42 in male Wistar rats (Alzheimer's disease model). Rats received morin (20 mg/kg, oral gavage) for 14 consecutive days after intrahippocampal injection of Aβ_1-42. Morin decreased the levels of malondialdehyde and nitric oxide, increased glutathione content, and enhanced catalase activity in the hippocampus of animals receiving Aβ_1-42. It also reduced the expression of tumor necrosis factor-α, interleukin-1β, interleukin-6, nuclear factor-kappa B, and N-methyl-D-aspartate receptor subunits 2A and 2B and increased the expression of brain-derived neurotrophic factor and α7 nicotinic acetylcholine receptor in the hippocampus of Aβ_1-42-injected rats. Besides, morin modified neuronal loss and histological changes in the CA1 region of the hippocampus. Morin allowed Aβ_1-42-infused rats to swim more time in the target quadrant in the Morris water maze test. It is concluded that morin may be suitable for the prevention and treatment of Alzheimer's disease by strengthening the antioxidant system, inhibiting neuroinflammation, preventing neuronal death, and enhancing memory function.

Engrafted stem cell therapy for Alzheimer's disease: A promising treatment strategy with clinical outcome

To date, although the microscopic alterations present in Alzheimer's disease (AD) have been well known for over a century only a handful of symptomatic treatments have been developed which are a far cry from a full cure providing volatile benefits. In this context, the intervention of stem cell therapy (SCT) has been proposed as an auxiliary treatment for AD as suggested by the rising number of pre-clinical studies that stem cell engraftment could provide an exciting future treatment regimen against neurodegeneration. Although, most of the primary enthusiasm about this approach was based on replacing deteriorating neurons, the latest studies have implied that the positive modulations fostered by stem cells are fuelled by bystander effects. Present review provides a detailed update on stem cell therapy for AD along with meticulous discussion regarding challenges in developing different stem cells from an aspect of experiment to clinical research and their potential in the milieu of AD hallmarks. Specifically, we focus and provide in depth view on recent advancements in the discipline of SCT aiming to repopulate or regenerate the degenerating neuronal circuitry in AD using stem-cell-on-a-chip and 3D bioprinting techniques. The focus is specifically on the successful restoration of cognitive functions upon engraftment of stem cells on in vivo models for the benefit of the current researchers and their understanding about the status of SCT in AD and finally summarizing on what future holds for SCT in the treatment of AD.

Genetic Therapies for Alzheimer's Disease: A Scoping Review

Effective, disease modifying therapies for Alzheimer's disease (AD) remain a quandary, following a panoply of expensive failures in human clinical trials. Given the stagnation in therapeutics, alternative approaches are needed. Recent successes of genetic therapies in other neurodegenerative diseases may highlight the way forward. This scoping review explores suggested targets of genetic therapy in AD, with a focus on vector-based approaches in pre-clinical and clinical trials. Putative targets of genetic therapies tested in pre-clinical trials include amyloid pathway intermediates and enzymes modulation, tau protein downregulation, APOE4 downregulation and APOE2 upregulation, neurotrophin expression (nerve growth factor (NGF) and brain-derived neurotrophic factor), and inflammatory cytokine alteration, among several other approaches. There have been three completed human clinical trials for genetic therapy in AD patients, all of which upregulated NGF in AD patients, showing some mixed evidence of benefit. Several impediments remain to be surpassed before genetic therapies can be successfully applied to AD, including the challenge of delivering monogenic genetic therapies for complex polygenic disorders, risks in the dominant delivery method (intracranial injection), stability of genetic therapies in vivo, poor translatability of pre-clinical AD models, and the expense of genetic therapy production. Genetic therapies represent an exciting opportunity within the world of AD therapeutics, but clinical applications likely remain a long term, rather than short term, possibility.

TrkB receptor cleavage by delta-secretase abolishes its phosphorylation of APP, aggravating Alzheimer's disease pathologies

Neurotrophins promote neuronal survival and synaptic plasticity via activating the tropomyosin receptor kinases. BDNF and its high-affinity receptor TrkB are reduced in Alzheimer's disease (AD), contributing to progressive cognitive decline. However, how the signaling mediates AD pathologies remains incompletely understood. Here we show that the TrkB receptor binds and phosphorylates APP, reducing amyloid-β production, which are abrogated by δ-secretase cleavage of TrkB in AD. Remarkably, BDNF stimulates TrkB to phosphorylate APP Y687 residue that accumulates APP in the TGN (Trans-Golgi Network) and diminishes its amyloidogenic cleavage. Delta-secretase cleaves TrkB at N365 and N486/489 residues and abolishes its neurotrophic activity, decreasing p-APP Y687 and altering its subcellular trafficking. Notably, both TrkB and APP are robustly cleaved by δ-secretase in AD brains, accompanied by mitigated TrkB signaling and reduced p-Y687. Blockade of TrkB cleavage attenuates AD pathologies in 5xFAD mice, rescuing the learning and memory. Viral expression of TrkB 1-486 fragment in the hippocampus of APP/PS1 mice facilitates amyloid pathology and mitigates cognitive functions. Hence, δ-secretase cleaves TrkB and blunts its phosphorylation of APP, facilitating AD pathogenesis.

LMDS-1, a potential TrkB receptor agonist provides a safe and neurotrophic effect for early-phase Alzheimer's disease

RATIONALE

The signaling pathways of tropomyosin-related kinase B (TrkB) receptor play a pivotal role in axonal sprouting, proliferation of dendritic arbor, synaptic plasticity, and neuronal differentiation. The levels of BDNF and TrkB receptor were reduced in patients with Alzheimer's disease (AD).

OBJECTIVES

The activation of TrkB signaling pathways is a potential strategy for AD therapies. We intended to identify potential TrkB agonists to activate the neuroprotective signaling to alleviate the pathological features of AD mice.

RESULTS

Both of the Aβ-deteriorated hippocampal primary neurons and mouse models were generated and showed AD characteristics. We first investigated 12 potential TrkB agonists with primary hippocampal neurons of mice. Both 7,8-DHF and LMDS-1 were identified to have better effect than the other compounds on dendritic arborization of the neurons and were further applied to the Aβ-injected mouse model. The short-term cognitive behavior and pathology in the mice were improved by LMDS-1. Further investigation indicated that LMDS-1 activated the TrkB through phosphorylation at Y516 rather than Y816. In addition, the ERK but not CaMKII or Akt was activated in the mouse hippocampus with LMDS-1 administration. LMDS-1 treatment also upregulated CREB and BDNF while downregulated the GSK3β active form and tau phosphorylation.

CONCLUSIONS

This study suggests that LMDS-1 upregulates the expression of BDNF and ameliorates the early-phase phenotypes of the AD-like mice through the pTrkB (Y516)-ERK-CREB pathway. In addition, LMDS-1 has better effect than 7,8-DHF in ameliorating the behavioral and pathological features of AD-like mice.

Deficiency in BDNF/TrkB Neurotrophic Activity Stimulates δ-Secretase by Upregulating C/EBPβ in Alzheimer's Disease

BDNF/TrkB neurotrophic signaling regulates neuronal development, differentiation, and survival, and deficient BDNF/TrkB activity underlies neurodegeneration in Alzheimer’s disease (AD). However, exactly how BDNF/TrkB participates in AD pathology remains unclear. Here, we show that deprivation of BDNF/TrkB increases inflammatory cytokines and activates the JAK2/STAT3 pathway, resulting in the upregulation of transcription factor C/EBPβ. This, in turn, results in increased expression of δ-secretase, leading to both APP and Tau fragmentation by δ-secretase and neuronal loss, which can be blocked by expression of STAT3 Y705F, knockdown of C/EBPβ, or the δ-secretase enzymatic-dead C189S mutant. Inhibition of this pathological cascade can also rescue impaired synaptic plasticity and cognitive dysfunctions. Importantly, reduction in BDNF/TrkB neurotrophic signaling is inversely coupled with an increase in JAK2/STAT3, C/EBPβ, and δ-secretase escalation in human AD brains. Therefore, our findings provide a mechanistic link between BDNF/TrkB reduction, C/EBPβ upregulation, δ-secretase activity, and Aβ and Tau alterations in murine brains.

Deficient BDNF/TrkB activity underlies AD pathogenesis. Wang et al. report that deprivation of BDNF/TrkB increases inflammatory cytokines and activates the JAK2/STAT3 pathway, resulting in the upregulation of C/EBPβ/AEP signaling. Reduction of BDNF is inversely coupled with the aforementioned pathway in AD brains. Inhibition of JAK2/STAT3/C/EBPβ/AEP prevents BDNF-depletion-mediated pathology.

Cotinine and 6-Hydroxy-L-Nicotine Reverses Memory Deficits and Reduces Oxidative Stress in Aβ25-35-Induced Rat Model of Alzheimer's Disease

The nicotinic derivatives, cotinine (COT), and 6-hydroxy-L-nicotine (6HLN), showed promising cognitive-improving effects without exhibiting the nicotine's side-effects. Here, we investigated the impact of COT and 6HLN on memory impairment and the oxidative stress in the Aβ25-35-induced rat model of Alzheimer's disease (AD). COT and 6HLN were chronically administered to Aβ25-35-treated rats, and their memory performances were assessed using in vivo tasks (Y-maze, novel object recognition, and radial arm maze). By using in silico tools, we attempted to associate the behavioral outcomes with the calculated binding potential of these nicotinic compounds in the allosteric sites of α7 and α4β2 subtypes of the nicotinic acetylcholine receptors (nAChRs). The oxidative status and acetylcholinesterase (AChE) activity were determined from the hippocampal tissues. RT-qPCR assessed bdnf, arc, and il-1β mRNA levels. Our data revealed that COT and 6HLN could bind to α7 and α4β2 nAChRs with similar or even higher affinity than nicotine. Consequently, the treatment exhibited a pro-cognitive, antioxidant, and anti-AChE profile in the Aβ25-35-induced rat model of AD. Finally, RT-qPCR analysis revealed that COT and 6HLN positively modulated the bdnf, arc, and il-1β genes expression. Therefore, these nicotinic derivatives that act on the cholinergic system might represent a promising choice to ameliorate AD conditions.

Myrtus communis subsp. communis improved cognitive functions in ovariectomized diabetic rats

AIM

The purpose of this study was to investigate the possible effects of Myrtus communis subsp. communis (MC) on cognitive impairment in ovariectomized diabetic rats.

MATERIAL AND METHOD

Female Sprague-Dawley rats were divided into 5 groups consisting of 15 rats each; Control (C), Diabetes (D), Ovariectomy and diabetes (OVX + D), Ovariectomy, diabetes and donepezil (OVX + D + Don), Ovariectomy, diabetes and Myrtus communis subsp. communis (OVX + D + MC). Blood glucose measurements were made at the beginning and end of the experiments. The animals underwent the novel object recognition test (NORT) and their performance was evaluated. In hippocampal tissues; amyloid beta (Aβ) and neprilysin levels, acetylcholinesterase (AChE), and choline acetyltransferase (ChAT) activities, polysialylated neural cell adhesion molecule (PSA-NCAM), α7 subunit of neuronal nicotinic acetylcholine receptor (α7-nAChR) and brain derived neurotrophic factor (BDNF) gene expressions were examined.

RESULTS

Animals with ovariectomy and diabetes showed increased levels of blood glucose, AChE activity and Aβ levels, and decreased neprilysin levels, ChAT activity, α7-nAChR, PSA-NCAM and BDNF gene expressions in parallel with a decrease in NORT performance score. On the other hand, in the MC-treated OVX + D group, there was a significant decrease observed in blood glucose levels and AChE activities while there was improvement in NORT performances and an increase in hippocampal ChAT activity, neprilysin levels, α7-nAChR, PSA-NCAM and BDNF expressions.

CONCLUSION

These results suggest that MC extract could improve cognitive and neuronal functions with its anticholinesterase and antihyperglycemic properties.

Current status and future prospects of stem cell therapy in Alzheimer's disease

Alzheimer's disease is a common progressive neurodegenerative disorder, pathologically characterized by the presence of β-amyloid plaques and neurofibrillary tangles. Current treatment approaches using drugs only alleviate the symptoms without curing the disease, which is a serious issue and influences the quality of life of the patients and their caregivers. In recent years, stem cell technology has provided new insights into the treatment of neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis. Currently, the main sources of stem cells include neural stem cells, embryonic stem cells, mesenchymal stem cells, and induced pluripotent stem cells. In this review, we discuss the pathophysiology and general treatment of Alzheimer's disease, and the current state of stem cell transplantation in the treatment of Alzheimer's disease. We also assess future challenges in the clinical application and drug development of stem cell transplantation as a treatment for Alzheimer's disease.

MicroRNA-204 silencing relieves pain of cervical spondylotic radiculopathy by targeting GDNF

Cervical spondylosis may cause chronic neck pain, radiculopathy and/or myelopathy, and consequently results in severe brain damage. Glial cell line-derived neurotrophic factor (GDNF) is a potent neurotrophic factor for motoneurons. Accumulating microRNAs (miRNAs) have highlighted as critical regulators of GDNF signaling in the mediation of neuroinflammation and neuropathic pain. Hence, we performed this study to investigate the potential role of miR-204 in the neuropathic pain of cervical spondylotic radiculopathy (CSR) by targeting GDNF. A rat model of spinal cord compression (SCC) was established to stimulate a pathologic lesion. RT-qPCR and western blot assays characterized the downregulation of GDNF and the upregulation of miR-204 in spinal cord tissues of rats under the conditions of SCC. Moreover, miR-204 could directly target GDNF, as evidenced by dual-luciferase reporter gene assay. In order to elucidate the roles of miR-204 and GDNF in SCC-induced neuropathic pain, miR-204 sponge, GDNF, or shRNA against GDNF was introduced to the rats, followed by measurements for SCC-induced neuroinflammation and neuropathic pain. GDNF upregulation or miR-204 silencing was identified to reduce the spontaneous pain score, gait scores and cell apoptosis. Furthermore, GDNF upregulation or miR-204 silencing resulted in elevated amplitude of sensory-evoked potentials (SEPs), number of motoneurons, release of pro-inflammatory factors, TNF-α, and IL-1β in addition to an increase in the anti-inflammatory factor BDNF. Taken together, upregulation of GDNF induced by miR-204 silencing confers protection against SCC-induced pain in rat models, suggesting a potential therapeutic target for CSR treatment.

The Amyloid-β Oligomer Hypothesis: Beginning of the Third Decade

The amyloid-β oligomer (AβO) hypothesis was introduced in 1998. It proposed that the brain damage leading to Alzheimer’s disease (AD) was instigated by soluble, ligand-like AβOs. This hypothesis was based on the discovery that fibril-free synthetic preparations of AβOs were potent CNS neurotoxins that rapidly inhibited long-term potentiation and, with time, caused selective nerve cell death (Lambert et al., 1998). The mechanism was attributed to disrupted signaling involving the tyrosine-protein kinase Fyn, mediated by an unknown toxin receptor. Over 4,000 articles concerning AβOs have been published since then, including more than 400 reviews. AβOs have been shown to accumulate in an AD-dependent manner in human and animal model brain tissue and, experimentally, to impair learning and memory and instigate major facets of AD neuropathology, including tau pathology, synapse deterioration and loss, inflammation, and oxidative damage. As reviewed by Hayden and Teplow in 2013, the AβO hypothesis “has all but supplanted the amyloid cascade.” Despite the emerging understanding of the role played by AβOs in AD pathogenesis, AβOs have not yet received the clinical attention given to amyloid plaques, which have been at the core of major attempts at therapeutics and diagnostics but are no longer regarded as the most pathogenic form of Aβ. However, if the momentum of AβO research continues, particularly efforts to elucidate key aspects of structure, a clear path to a successful disease modifying therapy can be envisioned. Ensuring that lessons learned from recent, late-stage clinical failures are applied appropriately throughout therapeutic development will further enable the likelihood of a successful therapy in the near-term.

Delta-secretase-cleaved Tau antagonizes TrkB neurotrophic signalings, mediating Alzheimer's disease pathologies

BDNF, an essential trophic factor implicated in synaptic plasticity and neuronal survival, is reduced in Alzheimer's disease (AD). BDNF deficiency's association with Tau pathology in AD is well documented. However, the molecular mechanisms accounting for these events remain incompletely understood. Here we show that BDNF deprivation triggers Tau proteolytic cleavage by activating δ-secretase [i.e., asparagine endopeptidase (AEP)], and the resultant Tau N368 fragment binds TrkB receptors and blocks its neurotrophic signals, inducing neuronal cell death. Knockout of BDNF or TrkB receptors provokes δ-secretase activation via reducing T322 phosphorylation by Akt and subsequent Tau N368 cleavage, inducing AD-like pathology and cognitive dysfunction, which can be restored by expression of uncleavable Tau N255A/N368A mutant. Blocking the Tau N368-TrkB complex using Tau repeat-domain 1 peptide reverses this pathology. Thus, our findings support that BDNF reduction mediates Tau pathology via activating δ-secretase in AD.

The Role of Insulin-Like Growth Factors and Insulin-Like Growth Factor-Binding Proteins in the Nervous System

The insulin-like growth factors (IGF-I and IGF-II) and their receptors are widely expressed in nervous tissue from early embryonic life. They also cross the blood brain barriers by active transport, and their regulation as endocrine factors therefore differs from other tissues. In brain, IGFs have paracrine and autocrine actions that are modulated by IGF-binding proteins and interact with other growth factor signalling pathways. The IGF system has roles in nervous system development and maintenance. There is substantial evidence for a specific role for this system in some neurodegenerative diseases, and neuroprotective actions make this system an attractive target for new therapeutic approaches. In developing new therapies, interaction with IGF-binding proteins and other growth factor signalling pathways should be considered. This evidence is reviewed, gaps in knowledge are highlighted, and recommendations are made for future research.

Targeting Alzheimer's disease with gene and cell therapies

Alzheimer's disease (AD) causes dementia in both young and old people affecting more than 40 million people worldwide. The two neuropathological hallmarks of the disease, amyloid beta (Aβ) plaques and neurofibrillary tangles consisting of protein tau are considered the major contributors to the disease. However, a more complete picture reveals significant neurodegeneration and decreased cell survival, neuroinflammation, changes in protein and energy homeostasis and alterations in lipid and cholesterol metabolism. In addition, gene and cell therapies for severe neurodegenerative disorders have recently improved technically in terms of safety and efficiency and have translated to the clinic showing encouraging results. Here, we review broadly current data within the field for potential targets that could modify AD through gene and cell therapy strategies. We envision that not only Aβ will be targeted in a disease-modifying treatment strategy but rather that a combination of treatments, possibly at different intervention times may prove beneficial in curing this devastating disease. These include decreased tau pathology, neuronal growth factors to support neurons and modulation of neuroinflammation for an appropriate immune response. Furthermore, cell based therapies may represent potential strategies in the future.

Astrocytes with previous chronic exposure to amyloid β-peptide fragment 1-40 suppress excitatory synaptic transmission

Synaptic dysfunction and neuronal death are responsible for cognitive and behavioral deficits in Alzheimer's disease (AD). It is well known that such neurological abnormalities are preceded by long-term exposure of amyloid β-peptide (Aβ) and/or hyperphosphorylated tau prior. In addition to the neurological deficit, astrocytes as a major glial cell type in the brain, significantly participate in the neuropathogenic mechanisms underlying synaptic modulation. Although astrocytes play a significant key role in modulating synaptic transmission, little is known on whether astrocyte dysfunction caused by such long-term Aβ exposure affects synapse formation and function. Here, we show that synapse formation and synaptic transmission are attenuated in hippocampal-naïve neurons co-cultured with astrocytes that have previously experienced chronic Aβ_1-40 exposure. In this abnormal astrocytic condition, hippocampal neurons exhibit decrements of evoked excitatory post-synaptic currents (EPSCs) and miniature EPSC frequency. Furthermore, size of readily releasable synaptic pools and number of excitatory synapses were also significantly decreased. Contrary to these negative effects, release probability at individual synapses was significantly increased in the same astrocytic condition. Taken together, our data indicate that lower synaptic transmission caused by astrocytes previously, and chronically, exposed to Aβ1-40 is attributable to a small number of synapses with higher release probability.

Regulation and effects of neurotrophic factors after neural stem cell transplantation in a transgenic mouse model of Alzheimer disease

According to much research, neurodegeneration and cognitive decline in Alzheimer disease (AD) are correlated with alternations of neurotrophic factors such as nerve growth factor, brain-derived neurotrophic factor, and glial cell-derived neurotrophic factor. The experimental illumination of neural stem cell (NSC) transplantation to eliminate AD symptoms is being explored frequently, and we have acknowledged that neurotrophic factors may play a pivotal role in cognitive improvement. However, the relation between the reversal of cognitive deficits after NSC transplantation and directed alternations of neurotrophic factors is not clearly expounded. Meanwhile, reduced inflammatory response, promoted vessel density, and vascular endothelial growth factor (VEGF) can be reflections of improvement in cerebrovascular function. Three weeks after NSC transplantation, spatial learning and memory function in NSC-injected (Tg-NSC) mice were significantly improved compared with vehicle-injected (Tg-Veh) mice. Meanwhile, results obtained by immunofluorescence and Western blot analyses demonstrated that the levels of neurotrophic factors, VEGF, and vessel density in the cortex of Tg-NSC mice were significantly enhanced compared with Tg-Veh mice, while the levels of proinflammatory cytokines interleukin (IL)-1β, tumor necrosis factor-α, and IL-6 were significantly decreased. Our results suggest that elevated concentrations of neurotrophic factors probably play a critical role in rescuing cognitive dysfunction in APP/PS1 transgenic mice after NSC transplantation, and neurotrophic factors may improve cerebrovascular function by means such as reducing inflammatory response and promoting angiogenesis.

Neural stem cell therapy for neurodegenerative disorders: The role of neurotrophic support

Neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease, and Huntington's disease currently affect tens of millions of people worldwide. Unfortunately, as the world's population ages, the incidence of many of these diseases will continue to rise and is expected to more than double by 2050. Despite significant research and a growing understanding of disease pathogenesis, only a handful of therapies are currently available and all of them provide only transient benefits. Thus, there is an urgent need to develop novel disease-modifying therapies to prevent the development or slow the progression of these debilitating disorders. A growing number of pre-clinical studies have suggested that transplantation of neural stem cells (NSCs) could offer a promising new therapeutic approach for neurodegeneration. While much of the initial excitement about this strategy focused on the use of NSCs to replace degenerating neurons, more recent studies have implicated NSC-mediated changes in neurotrophins as a major mechanism of therapeutic efficacy. In this mini-review we will discuss recent work that examines the ability of NSCs to provide trophic support to disease-effected neuronal populations and synapses in models of neurodegeneration. We will then also discuss some of key challenges that remain before NSC-based therapies for neurodegenerative diseases can be translated toward potential clinical testing.

PGC-1α or FNDC5 Is Involved in Modulating the Effects of Aβ1-42 Oligomers on Suppressing the Expression of BDNF, a Beneficial Factor for Inhibiting Neuronal Apoptosis, Aβ Deposition and Cognitive Decline of APP/PS1 Tg Mice

Alzheimer's disease (AD) is generally defined as the aberrant production of β-amyloid protein (Aβ) and hyperphosphorylated tau protein, which are deposited in β-amyloid plaques (APs) and neurofibrillary tangles (NFTs), respectively. Decreased levels of brain-derived neurotrophic factor (BDNF) have been detected in patients with AD compared to control subjects. However, the underlying molecular mechanisms driving the downregulation of the BDNF remain unknown. Therefore, we explored the mechanisms underlying the regulation of BDNF in the neurons of APP/PS1 transgenic (Tg) mice, an AD experimental model. Using the APP/PS1 Tg mice, we found that BDNF expression was markedly downregualted at the age of 3- and 9-month-old. After cerebroventricular injection (i.c.v) of Aβ_1-42 oligomers into the mice, BDNF was also found to be decreased, which demonstrated the critical roles of the Aβ_1-42 oligomers in regulating the expression of BDNF. In neuronal culture, peroxisome proliferators-activated receptor γ coactivator 1α (PGC-1α) and fibronectin type III domain-containing 5 (FNDC5) were found to be downregulated by treatment with the Aβ_1-42 oligomers. In addition, overexpression of either PGC-1α or FNDC5 reversed the suppressive effects of the Aβ_1-42 oligomers on the expression of BDNF in neuroblastoma 2a (n2a) cells. More importantly, elevating the levels of PGC-1α, FNDC5 or BDNF in the n2a cells counteracted the effects of the Aβ_1-42 oligomers on neuronal apoptosis. Additionally, intranasal administration BDNF in the APP/PS1 Tg mice decreased the Aβ deposition and reduced the cognitive decline of the mice.

The Effects of IGF-1 on TNF-α-Treated DRG Neurons by Modulating ATF3 and GAP-43 Expression via PI3K/Akt/S6K Signaling Pathway

Upregulation of the pro-inflammatory cytokine tumor necrosis factor α (TNF-α) is involved in the development and progression of numerous neurological disorders. Recent reports have challenged the concept that TNF-α exhibits only deleterious effects of pro-inflammatory destruction, and have raised the awareness that it may play a beneficial role in neuronal growth and function in particular conditions, which prompts us to further investigate the role of this cytokine. Insulin-like growth factor-1 (IGF-1) is a cytokine possessing powerful neuroprotective effects in promoting neuronal survival, neuronal differentiation, neurite elongation, and neurite regeneration. The association of IGF-1 with TNF-α and the biological effects, produced by interaction of IGF-1 and TNF-α, on neuronal outgrowth status of primary sensory neurons are still to be clarified. In the present study, using an in vitro model of primary cultured rat dorsal root ganglion (DRG) neurons, we demonstrated that TNF-α challenge at different concentrations elicited diverse biological effects. Higher concentration of TNF-α (10 ng/mL) dampened neurite outgrowth, induced activating transcription factor 3 (ATF3) expression, reduced growth-associated protein 43 (GAP-43) expression, and promoted GAP-43 and ATF3 coexpression, which could be reversed by IGF-1 treatment; while lower concentration of TNF-α (1 ng/mL) promoted neurite sprouting, decreased ATF3 expression, increased GAP-43 expression, and inhibited GAP-43 and ATF3 coexpression, which could be potentiated by IGF-1 supplement. Moreover, IGF-1 administration restored the activation of Akt and p70 S6 kinase (S6K) suppressed by higher concentration of TNF-α (10 ng/mL) challenge. In contrast, lower concentration of TNF-α (1 ng/mL) had no significant effect on Akt or S6K activation, and IGF-1 administration activated these two kinases. The effects of IGF-1 were abrogated by phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002. These data imply that IGF-1 counteracts the toxic effect of higher concentration of TNF-α, while potentiates the growth-promoting effect of lower concentration of TNF-α, with the node for TNF-α and IGF-1 interaction being the PI3K/Akt/S6K signaling pathway. This study is helpful for interpretation of the association of IGF-1 with TNF-α and the neurobiological effects elicited by interaction of IGF-1 and TNF-α in neurological disorders.

Neurotrophic factors in Alzheimer's and Parkinson's diseases: implications for pathogenesis and therapy

Neurotrophic factors comprise essential secreted proteins that have several functions in neural and non-neural tissues, mediating the development, survival and maintenance of peripheral and central nervous system. Therefore, neurotrophic factor issue has been extensively investigated into the context of neurodegenerative diseases. Alzheimer's disease and Parkinson's disease show changes in the regulation of specific neurotrophic factors and their receptors, which appear to be critical for neuronal degeneration. Indeed, neurotrophic factors prevent cell death in degenerative processes and can enhance the growth and function of affected neurons in these disorders. Based on recent reports, this review discusses the main findings related to the neurotrophic factor support – mainly brain-derived neurotrophic factor and glial cell line-derived neurotrophic factor – in the survival, proliferation and maturation of affected neurons in Alzheimer's disease and Parkinson's disease as well as their putative application as new therapeutic approach for these diseases management.

Mifepristone-inducible transgene expression in neural progenitor cells in vitro and in vivo

Numerous gene and cell therapy strategies are being developed for the treatment of neurodegenerative disorders. Many of these strategies use constitutive expression of therapeutic transgenic proteins, and although functional in animal models of disease, this method is less likely to provide adequate flexibility for delivering therapy to humans. Ligand-inducible gene expression systems may be more appropriate for these conditions, especially within the central nervous system (CNS). Mifepristone's ability to cross the blood-brain barrier makes it an especially attractive ligand for this purpose. We describe the production of a mifepristone-inducible vector system for regulated expression of transgenes within the CNS. Our inducible system used a lentivirus-based vector platform for the ex vivo production of mifepristone-inducible murine neural progenitor cells that express our transgenes of interest. These cells were processed through a series of selection steps to ensure that the cells exhibited appropriate transgene expression in a dose-dependent and temporally controlled manner with minimal background activity. Inducible cells were then transplanted into the brains of rodents, where they exhibited appropriate mifepristone-inducible expression. These studies detail a strategy for regulated expression in the CNS for use in the development of safe and efficient gene therapy for neurological disorders.

BDNF promotes human neural stem cell growth via GSK-3β-mediated crosstalk with the wnt/β-catenin signaling pathway

Brain-derived neurotrophic factor (BDNF) plays important roles in neural stem cell (NSC) growth. In this study, we investigated whether BDNF exerts its neurotrophic effects through the Wnt/β-catenin signaling pathway in human embryonic spinal cord NSCs (hESC-NSCs) in vitro. We found an increase in hESC-NSC growth by BDNF overexpression. Furthermore, expression of Wnt1, Frizzled1 and Dsh was upregulated, whereas GSK-3β expression was downregulated. In contrast, hESC-NSC growth was decreased by BDNF RNA interference. BDNF, Wnt1 and β-catenin components were all downregulated, whereas GSK-3β was upregulated. Next, we treated hESC-NSCs with 6-bromoindirubin-3'-oxime (BIO), a small molecule inhibitor of GSK-3β. BIO reduced the effects of BDNF upregulation/downregulation on the cell number, soma size and differentiation, and suppressed the effect of BDNF modulation on the Wnt signaling pathway. Our findings suggest that BDNF promotes hESC-NSC growth in vitro through crosstalk with the Wnt/β-catenin signaling pathway, and that this interaction may be mediated by GSK-3β.

BDNF promotes the growth of human neurons through crosstalk with the Wnt/β-catenin signaling pathway via GSK-3β

Brain-derived neurotrophic factor (BDNF) plays an important role in neuronal growth; however, the downstream regulatory mechanisms remain unclear. In this study, we investigated whether BDNF exerts its neurotrophic effects through the Wnt/β-catenin signaling pathway in human embryonic spinal cord neurons in vitro. We found that neuronal growth (soma size and average neurite length) was increased by transfection with a BDNF overexpression plasmid. Western blotting and real-time quantitative PCR showed that expression of the BDNF pathway components TrkB, PI3K, Akt and PLC-γ was increased by BDNF overexpression. Furthermore, the Wnt signaling factors Wnt, Frizzled and Dsh and the downstream target β-catenin were upregulated, whereas GSK-3β was downregulated. In contrast, when BDNF signaling was downregulated with BDNF siRNA, the growth of neurons was decreased. Furthermore, BDNF signaling factors, Wnt pathway components and β-catenin were all downregulated, whereas GSK-3β was upregulated. This suggests that BDNF affects the growth of neurons in vitro through crosstalk with Wnt signaling, and that GSK-3β may be a critical factor linking these two pathways. To evaluate this possibility, we treated neurons with 6-bromoindirubin-3'-oxime (BIO), a small molecule GSK-3β inhibitor. BIO reduced the effects of BDNF upregulation/downregulation on soma size and average neurite length, and suppressed the impact of BDNF modulation on the Wnt signaling pathway. Taken together, our findings suggest that BDNF promotes the growth of neurons in vitro through crosstalk with the Wnt/β-catenin signaling pathway, and that this interaction may be mediated by GSK-3β.

Paracrine Neuroprotective Effects of Neural Stem Cells on Glutamate-Induced Cortical Neuronal Cell Excitotoxicity

PURPOSE

Glutamate is a major excitatory neurotransmitter in mammalian central nervous system. Excessive glutamate releasing overactivates its receptors and changes calcium homeostasis that in turn leads to a cascade of intracellular events causing neuronal degeneration. In current study, we used neural stem cells conditioned medium (NSCs-CM) to investigate its neuroprotective effects on glutamate-treated primary cortical neurons.

METHODS

Embryonic rat primary cortical cultures were exposed to different concentrations of glutamate for 1 hour and then they incubated with NSCs-CM. Subsequently, the amount of cell survival in different glutamate excitotoxic groups were measured after 24 h of incubation by trypan blue exclusion assay and MTT assay. Hoechst and propidium iodide were used for determining apoptotic and necrotic cell death pathways proportion and then the effect of NSCs-CM was investigated on this proportion.

RESULTS

NSCs conditioned medium increased viability rate of the primary cortical neurons after glutamate-induced excitotoxicity. Also we found that NSCs-CM provides its neuroprotective effects mainly by decreasing apoptotic cell death rate rather than necrotic cell death rate.

CONCLUSION

The current study shows that adult neural stem cells could exert paracrine neuroprotective effects on cortical neurons following a glutamate neurotoxic insult.

Primary phospholipase C and brain disorders

In the brain, the primary phospholipase C (PLC) proteins, PLCβ, and PLCγ, are activated primarily by neurotransmitters, neurotrophic factors, and hormones through G protein-coupled receptors (GPCRs) and receptor tyrosine kinases (RTKs). Among the primary PLC isozymes, PLCβ1, PLCβ4, and PLCγ1 are highly expressed and differentially distributed, suggesting a specific role for each PLC subtype in different regions of the brain. Primary PLCs control neuronal activity, which is important for synapse function and development. In addition, dysregulation of primary PLC signaling is linked to several brain disorders including epilepsy, schizophrenia, bipolar disorder, Huntington's disease, depression and Alzheimer's disease. In this review, we included current knowledge regarding the roles of primary PLC isozymes in brain disorders.

A genetically immortalized human stem cell line: a promising new tool for Alzheimer's disease therapy

Amyloid-β peptides and hyper-phosphorylated tau are the main pathological hallmarks of Alzheimer's disease (AD). Given the recent failure of several large-scale clinical trials and the lack of disease-modifying pharmacological treatments, there is an urgent need to develop alternative therapies. A clinical grade human CTX0E03 neural stem cell line has recently passed phase I trials in people with stroke. However, this cell line has not been investigated in other neurodegenerative disorders. This study investigates the survival of CTX0E03 cells under conditions based on the underlying AD pathology. Cell viability assays showed a concentration dependence of this cell line to the toxic effects of Aβ1-42, but not Aβ1-40, and okadaic acid, a phosphatase 2A inhibitor. Notably, CTX0E03 cell line displayed toxicity at concentrations significantly higher than both rat neural stem cells and those previously reported for primary cultures. These results suggest CTX0E03 cells could be developed for clinical trials in AD patients.

Late-onset dementia: a mosaic of prototypical pathologies modifiable by diet and lifestyle

Idiopathic late-onset dementia (ILOD) describes impairments of memory, reasoning and/or social abilities in the elderly that compromise their daily functioning. Dementia occurs in several major prototypical neurodegenerative disorders that are currently defined by neuropathological criteria, most notably Alzheimer’s disease (AD), Lewy body dementia (LBD), frontotemporal dementia (FTD) and hippocampal sclerosis of aging (HSA). However, people who die with ILOD commonly exhibit mixed pathologies that vary within and between brain regions. Indeed, many patients diagnosed with probable AD exhibit only modest amounts of disease-defining amyloid β-peptide plaques and p-Tau tangles, and may have features of FTD (TDP-43 inclusions), Parkinson’s disease (α-synuclein accumulation), HSA and vascular lesions. Here I argue that this ‘mosaic neuropathological landscape’ is the result of commonalities in aging-related processes that render neurons vulnerable to the entire spectrum of ILODs. In this view, all ILODs involve deficits in neuronal energy metabolism, neurotrophic signaling and adaptive cellular stress responses, and associated dysregulation of neuronal calcium handling and autophagy. Although this mosaic of neuropathologies and underlying mechanisms poses major hurdles for development of disease-specific therapeutic interventions, it also suggests that certain interventions would be beneficial for all ILODs. Indeed, emerging evidence suggests that the brain can be protected against ILOD by lifelong intermittent physiological challenges including exercise, energy restriction and intellectual endeavors; these interventions enhance cellular stress resistance and facilitate neuroplasticity. There is also therapeutic potential for interventions that bolster neuronal bioenergetics and/or activate one or more adaptive cellular stress response pathways in brain cells. A wider appreciation that all ILODs share age-related cellular and molecular alterations upstream of aggregated protein lesions, and that these upstream events can be mitigated, may lead to implementation of novel intervention strategies aimed at reversing the rising tide of ILODs.

Effect of human umbilical cord blood derived lineage negative stem cells transplanted in amyloid-β induced cognitive impaired mice

Alzheimer's disease (AD) is pathologically characterized by extracellular deposition of insoluble amyloid-β (Aβ) plaques and intracellular tangles made up of phosphorylated tau in brain. Several therapeutic approaches are being carried out in animal AD models for testing their safety and efficacy in altering disease pathology and behavioral deficits. Very few studies have examined the effect of human umbilical cord blood (hUCB) derived stem cells in degenerative disease models despite growing number of cord blood banks worldwide. Here we have examined the therapeutic efficacy of hUCB derived lineage negative (Lin -ve) stem cells in alleviating behavioral and neuropathological deficits in a mouse model of cognitive impairment induced by bilateral intrahippocampal injection of Aβ-42. Lin -ve cells were transplanted at two doses (50,000 and 100,000) at the site of injury and examined at 10 and 60 days post transplantation for rescue of memory deficits. These cells were found to ameliorate cognitive impairment in 50,000-60 days and 100,000-10 days groups whereas, 50,000-10 days and 100,000-60 days groups could not exert any significant improvement. Further, mice showing spatial memory improvement were mediated by up-regulation of BDNF, CREB and also by concomitant down regulation of Fas-L in their brain. The transplanted cells were found in the host tissue and survived up to 60 days without expressing markers of neuronal differentiation or reducing Aβ burden in mouse brain. We suggest that these undifferentiated cells could exert neuroprotective effects either through inhibiting apoptosis and/or trophic effects in the brain.

Growth factor treatment to overcome Alzheimer's dysfunctional signaling

The number of people suffering from Alzheimer's disease (AD) will increase as the world population ages, creating a huge socio-economic burden. The three pathophysiological hallmarks of AD are the cholinergic system dysfunction, the β-amyloid peptide deposition and the Tau protein hyperphosphorylation. Current treatments have only transient effects and each tends to concentrate on a single pathophysiological aspect of AD. This review first provides an overall view of AD in terms of its pathophysiological symptoms and signaling dysfunction. We then examine the therapeutic potential of growth factors (GFs) by showing how they can overcome the dysfunctional cell signaling that occurs in AD. Finally, we discuss new alternatives to GFs that help overcome the problem of brain uptake, such as small peptides, with evidence from some of our unpublished data on human neuronal cell line.

Intranasal delivery of stem cells as therapy for central nervous system disease

Stem cells, upon entering the CNS, can preferentially migrate into disease foci, where they exert therapeutic effects that compensate for lost tissue, reconstructing damaged neuronal circuitry and establishing in the brain a new microenvironment suitable for cell survival. However, the route of stem cell delivery into the CNS remains a challenge: with systemic administration (e.g., intravenous injection), a fraction of cells may be trapped in other organs than the CNS, while direct CNS injections, e.g., intracerebroventricular or transcranial, are invasive. Intranasal (i.n.) delivery of stem cells, in contrast, can effectively bypass the blood-brain barrier, rapidly enter the CNS, and minimize systemic distribution. I.n. delivery of stem cells may therefore be a safe and non-invasive way of targeting the CNS and would thus be a promising therapeutic option for CNS disease. In this review we discuss the i.n. route for stem cell delivery into the CNS, and the perspectives of i.n. stem cell-based therapy in CNS disease.

Matrine protects neuro-axon from CNS inflammation-induced injury

Neuro-axonal injury in the central nervous system (CNS) is one of the major pathological hallmarks of experimental autoimmune encephalomyelitis (EAE), an experimental model of multiple sclerosis (MS). Matrine (MAT), a quinolizidine alkaloid derived from the herb Radix Sophorae Flave, has recently been shown to effectively suppress EAE through an anti-inflammatory mechanism. However, whether MAT can also protect myelin/axons from damage is not known. In the present study we show that, while untreated rats developed severe clinical disease, CNS inflammatory demyelination, and axonal damage, these clinical and pathological signs were significantly reduced by MAT treatment. Consistently, MAT treatment reduced the concentration of myelin basic protein in serum and downregulated expression of β-amyloid (Aβ) and B-site APP cleaving enzyme 1 (BACE-1) in the CNS. Further, the CNS of MAT-treated rats exhibited increased expression of brain-derived neurotrophic factor (BDNF), an important factor for neuronal survival and axonal growth. Together, these results demonstrate that MAT effectively prevented neuro-axonal injury, which can likely be attributed to inhibiting risk factors such as BACE-1 and upregulating neuroprotective factors such as BDNF. We conclude that this novel natural reagent, MAT, which effectively protects neuro-axons from CNS inflammation-induced damage, could be a potential candidate for the treatment of neurodegenerative diseases such as MS.

5-HT7 receptor activation promotes an increase in TrkB receptor expression and phosphorylation

The serotonin (5-HT) type 7 receptor is expressed throughout the CNS including the cortex and hippocampus. We have previously demonstrated that the application of 5-HT7 receptor agonists to primary hippocampal neurons and SH-SY5Y cells increases platelet-derived growth factor (PDGF) receptor expression and promotes neuroprotection against N-methyl-D-aspartate-(NMDA)-induced toxicity. The tropomyosin-related kinase B (TrkB) receptor is one of the receptors for brain-derived neurotrophic factor (BDNF) and is associated with neurodevelopmental and neuroprotective effects. Application of LP 12 to primary cerebral cortical cultures, SH-SY5Y cells, as well as the retinal ganglion cell line, RGC-5, increased both the expression of full length TrkB as well as its basal phosphorylation state at tyrosine 816. The increase in TrkB expression and phosphorylation was observed as early as 30 min after 5-HT7 receptor activation. In addition to full-length TrkB, kinase domain-deficient forms may be expressed and act as dominant-negative proteins toward the full length receptor. We have identified distinct patterns of TrkB isoform expression across our cell lines and cortical cultures. Although TrkB receptor expression is regulated by cyclic AMP and Gαs-coupled GPCRs in several systems, we demonstrate that, depending on the model system, pathways downstream of both Gαs and Gα12 are involved in the regulation of TrkB expression by 5-HT7 receptors. Given the number of psychiatric and degenerative diseases associated with TrkB/BDNF deficiency and the current interest in developing 5-HT7 receptor ligands as pharmaceuticals, identifying signaling relationships between these two receptors will aid in our understanding of the potential therapeutic effects of 5-HT7 receptor ligands.

Neural cell injury microenvironment induces neural differentiation of human umbilical cord mesenchymal stem cells

This study aimed to investigate the neural differentiation of human umbilical cord mesenchymal stem cells (hUCMSCs) under the induction of injured neural cells. After in vitro isolation and culture, passage 5 hUCMSCs were used for experimentation. hUCMSCs were co-cultured with normal or Aβ_1-40-injured PC12 cells, PC12 cell supernatant or PC12 cell lysate in a Transwell co-culture system. Western blot analysis and flow cytometry results showed that choline acetyltransferase and microtubule-associated protein 2, a specific marker for neural cells, were expressed in hUCMSCs under various culture conditions, and highest expression was observed in the hUCMSCs co-cultured with injured PC12 cells. Choline acetyltransferase and microtubule-associated protein 2 were not expressed in hUCMSCs cultured alone (no treatment). Cell Counting Kit-8 assay results showed that hUCMSCs under co-culture conditions promoted the proliferation of injured PC12 cells. These findings suggest that the microenvironment during neural tissue injury can effectively induce neural cell differentiation of hUCMSCs. These differentiated hUCMSCs likely accelerate the repair of injured neural cells.

Lenti-GDNF gene therapy protects against Alzheimer's disease-like neuropathology in 3xTg-AD mice and MC65 cells

AIMS

Glial cell-derived neurotrophic factor (GDNF) is emerging as a potent neurotrophic factor with therapeutic potential against a range of neurodegenerative conditions including Alzheimer's disease (AD). We assayed the effects of GDNF treatment in AD experimental models through gene-therapy procedures.

METHODS

Recombinant lentiviral vectors were used to overexpress GDNF gene in hippocampal astrocytes of 3xTg-AD mice in vivo, and also in the MC65 human neuroblastoma that conditionally overexpresses the 99-residue carboxyl-terminal (C99) fragment of the amyloid precursor protein.

RESULTS

After 6 months of overexpressing GDNF, 10-month-old 3xTg-AD mice showed preserved learning and memory, while their counterparts transduced with a green fluorescent protein vector showed cognitive loss. GDNF therapy did not significantly reduce amyloid and tau pathology, but rather, induced a potent upregulation of brain-derived neurotrophic factor that may act in concert with GDNF to protect neurons from atrophy and degeneration. MC65 cells overexpressing GDNF showed an abolishment of oxidative stress and cell death that was at least partially mediated by a reduced presence of intracellular C99 and derived amyloid β oligomers.

CONCLUSIONS

GDNF induced neuroprotection in the AD experimental models used. Lentiviral vectors engineered to overexpress GDNF showed to be safe and effective, both as a potential gene therapy and as a tool to uncover the mechanisms of GDNF neuroprotection, including cross talk between astrocytes and neurons in the injured brain.

A cGMP-applicable expansion method for aggregates of human neural stem and progenitor cells derived from pluripotent stem cells or fetal brain tissue

A cell expansion technique to amass large numbers of cells from a single specimen for research experiments and clinical trials would greatly benefit the stem cell community. Many current expansion methods are laborious and costly, and those involving complete dissociation may cause several stem and progenitor cell types to undergo differentiation or early senescence. To overcome these problems, we have developed an automated mechanical passaging method referred to as "chopping" that is simple and inexpensive. This technique avoids chemical or enzymatic dissociation into single cells and instead allows for the large-scale expansion of suspended, spheroid cultures that maintain constant cell/cell contact. The chopping method has primarily been used for fetal brain-derived neural progenitor cells or neurospheres, and has recently been published for use with neural stem cells derived from embryonic and induced pluripotent stem cells. The procedure involves seeding neurospheres onto a tissue culture Petri dish and subsequently passing a sharp, sterile blade through the cells effectively automating the tedious process of manually mechanically dissociating each sphere. Suspending cells in culture provides a favorable surface area-to-volume ratio; as over 500,000 cells can be grown within a single neurosphere of less than 0.5 mm in diameter. In one T175 flask, over 50 million cells can grow in suspension cultures compared to only 15 million in adherent cultures. Importantly, the chopping procedure has been used under current good manufacturing practice (cGMP), permitting mass quantity production of clinical-grade cell products.

Potential therapeutic effects of neurotrophins for acute and chronic neurological diseases

The neurotrophins (NTs) nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), NT-3, and NT-4/5 are proteins that regulate cell proliferation, differentiation, and survival in both the developing and mature central nervous system (CNS) by binding to two receptor classes, Trk receptors and p75 NTR. Motivated by the broad growth- and survival-promoting effects of these proteins, numerous studies have attempted to use exogenous NTs to prevent the death of cells that are associated with neurological disease or promote the regeneration of severed axons caused by mechanical injury. Indeed, such neurotrophic effects have been repeatedly demonstrated in animal models of stroke, nerve injury, and neurodegenerative disease. However, limitations, including the short biological half-lives and poor blood-brain permeability of these proteins, prevent routine application from treating human disease. In this report, we reviewed evidence for the neuroprotective efficacy of NTs in animal models, highlighting outstanding technical challenges and discussing more recent attempts to harness the neuroprotective capacity of endogenous NTs using small molecule inducers and cell transplantation.