Targeted delivery of nerve growth factor to the cholinergic basal forebrain of Alzheimer's disease patients: application of a second-generation encapsulated cell biodelivery device

Targeted gene delivery systems for T-cell engineering

T lymphocytes are indispensable for the host systems of defense against pathogens, tumors, and environmental threats. The therapeutic potential of harnessing the cytotoxic properties of T lymphocytes for antigen-specific cell elimination is both evident and efficacious. Genetically engineered T-cells, such as those employed in CAR-T and TCR-T cell therapies, have demonstrated significant clinical benefits in treating cancer and autoimmune disorders. However, the current landscape of T-cell genetic engineering is dominated by strategies that necessitate in vitro T-cell isolation and modification, which introduce complexity and prolong the development timeline of T-cell based immunotherapies. This review explores the complexities of gene delivery systems designed for T cells, covering both viral and nonviral vectors. Viral vectors are known for their high transduction efficiency, yet they face significant limitations, such as potential immunogenicity and the complexities involved in large-scale production. Nonviral vectors, conversely, offer a safer profile and the potential for scalable manufacturing, yet they often struggle with lower transduction efficiency. The pursuit of gene delivery systems that can achieve targeted gene transfer to T cell without the need for isolation represents a significant advancement in the field. This review assesses the design principles and current research progress of such systems, highlighting the potential for in vivo gene modification therapies that could revolutionize T-cell based treatments. By providing a comprehensive analysis of these systems, we aim to contribute valuable insights into the future development of T-cell immunotherapy.

Stimulating myelin restoration with BDNF: a promising therapeutic approach for Alzheimer's disease

Alzheimer's Disease (AD) is a chronic neurodegenerative disorder constituting the most common form of dementia (60%-70% of cases). Although AD presents majorly a neurodegenerative pathology, recent clinical evidence highlights myelin impairment as a key factor in disease pathogenesis. The lack of preventive or restorative treatment is emphasizing the need to develop novel therapeutic approaches targeting to the causes of the disease. Recent studies in animals and patients have highlighted the loss of myelination of the neuronal axons as an extremely aggravating factor in AD, in addition to the formation of amyloid plaques and neurofibrillary tangles that are to date the main pathological hallmarks of the disease. Myelin breakdown represents an early stage event in AD. However, it is still unclear whether myelin loss is attributed only to exogenous factors like inflammatory processes of the tissue or to impaired oligodendrogenesis as well. Neurotrophic factors are well established protective molecules under many pathological conditions of the neural tissue, contributing also to proper myelination. Due to their inability to be used as drugs, many research efforts are focused on substituting neurotrophic activity with small molecules. Our research team has recently developed novel micromolecular synthetic neurotrophin mimetics (MNTs), selectively acting on neurotrophin receptors, and thus offering a unique opportunity for innovative therapies against neurodegenerative diseases. These small sized, lipophilic molecules address the underlying biological effect of these diseases (neuroprotective action), but also they exert significant neurogenic actions inducing neuronal replacement of the disease areas. One of the significant neurotrophin molecules in the Central Nervous System is Brain-Derived-Neurotrophin-Factor (BDNF). BDNF is a neurotrophin that not only supports neuroprotection and adult neurogenesis, but also mediates pro-myelinating effects in the CNS. BDNF binds with high-affinity on the TrkB neurotrophin receptor and enhances myelination by increasing the density of oligodendrocyte progenitor cells (OPCs) and playing an important role in CNS myelination. Conclusively, in the present review, we discuss the myelin pathophysiology in Alzheimer's Diseases, as well as the role of neurotrophins, and specifically BDNF, in myelin maintenance and restoration, revealing its valuable therapeutic potential against AD.

The basal forebrain cholinergic system as target for cell replacement therapy in Parkinson's disease

In recent years there has been a renewed interest in the basal forebrain cholinergic system as a target for the treatment of cognitive impairments in patients with Parkinson's disease, due in part to the need to explore novel approaches to treat the cognitive symptoms of the disease and in part to the development of more refined imaging tools that have made it possible to monitor the progressive changes in the structure and function of the basal forebrain system as they evolve over time. In parallel, emerging technologies allowing the derivation of authentic basal forebrain cholinergic neurons from human pluripotent stem cells are providing new powerful tools for the exploration of cholinergic neuron replacement in animal models of Parkinson's disease-like cognitive decline. In this review, we discuss the rationale for cholinergic cell replacement as a potential therapeutic strategy in Parkinson's disease and how this approach can be explored in rodent models of Parkinson's disease-like cognitive decline, building on insights gained from the extensive animal experimental work that was performed in rodent and primate models in the 1980s and 90s. Although therapies targeting the cholinergic system have so far been focused mainly on patients with Alzheimer's disease, Parkinson's disease with dementia may be a more relevant condition. In Parkinson's disease with dementia, the basal forebrain system undergoes progressive degeneration and the magnitude of cholinergic cell loss has been shown to correlate with the level of cognitive impairment. Thus, cell therapy aimed to replace the lost basal forebrain cholinergic neurons represents an interesting strategy to combat some of the major cognitive impairments in patients with Parkinson's disease dementia.

Emerging Pro-neurogenic Therapeutic Strategies for Neurodegenerative Diseases: A Review of Pre-clinical and Clinical Research

The neuroscience community has largely accepted the notion that functional neurons can be generated from neural stem cells in the adult brain, especially in two brain regions: the subventricular zone of the lateral ventricles and the subgranular zone in the dentate gyrus of the hippocampus. However, impaired neurogenesis has been observed in some neurodegenerative diseases, particularly in Alzheimer's, Parkinson's, and Huntington's diseases, and also in Lewy Body dementia. Therefore, restoration of neurogenic function in neurodegenerative diseases emerges as a potential therapeutic strategy to counteract, or at least delay, disease progression. Considering this, the present study summarizes the different neuronal niches, provides a collection of the therapeutic potential of different pro-neurogenic strategies in pre-clinical and clinical research, providing details about their possible modes of action, to guide future research and clinical practice.

Polyethersulfone Polymer for Biomedical Applications and Biotechnology

Polymers stand out as promising materials extensively employed in biomedicine and biotechnology. Their versatile applications owe much to the field of tissue engineering, which seamlessly integrates materials engineering with medical science. In medicine, biomaterials serve as prototypes for organ development and as implants or scaffolds to facilitate body regeneration. With the growing demand for innovative solutions, synthetic and hybrid polymer materials, such as polyethersulfone, are gaining traction. This article offers a concise characterization of polyethersulfone followed by an exploration of its diverse applications in medical and biotechnological realms. It concludes by summarizing the significant roles of polyethersulfone in advancing both medicine and biotechnology, as outlined in the accompanying table.

Cyanidin Ameliorates Bisphenol A-Induced Alzheimer's Disease Pathology by Restoring Wnt/β-Catenin Signaling Cascade: an In Vitro Study

Alzheimer's disease (AD) is a progressive neurodegenerative disorder causing memory loss and cognitive decline, linked to amyloid-beta (Aβ) plaques and hyperphosphorylated tau protein accumulation in the brain. Environmental pollutant bisphenol A (BPA) has been implicated in AD pathology due to its neurotoxic effects. This study aims to evaluate cyanidin from flower bracts of Musa acuminata Colla (red variety; AAA group) for its neuroprotective properties against BPA-induced AD pathology. The extraction of cyanidin was optimized using 70% ethanol in acidified water, showing promising anti-acetylcholinesterase activity. Cyanidin was effectively purified from the resultant extract and characterized using spectroscopic techniques. Two gradient doses of cyanidin (90 and 10 µg/ml) were determined based on cell viability assay. The role of cyanidin in promoting nerve growth and differentiation was assessed in PC12 cells for up to 72 h. A discernible and statistically significant difference was assessed in neurite extension at both doses at 72 h, followed by pre-treatment with cyanidin. BPA stimulation significantly increased the p-tau expression compared to the control (p < 0.0001). Pre-treatment with cyanidin reduced the tau expression; however, a significant difference was observed compared to control cells (p = 0.0003). Cyanidin significantly enhanced the mRNA expression of Wnt3a (p < 0.0001), β-catenin (p = 0.0004), and NeuroD1 (p = 0.0289), and decreased the expression of WIF1(p = 0.0040) and DKK1 (p < 0.0001), which are Wnt antagonist when compared to cells stimulated with BPA. Conclusively, our finding suggests that cyanidin could agonize nerve growth factor and promote neuronal differentiation, reduce tau-hyperphosphorylation by restoring the Wnt/β-catenin signaling cascade, and thereby render its neuroprotective potential against BPA-induced AD pathology.

Recent approaches in regenerative medicine in the fight against neurodegenerative disease

Neurodegenerative diseases arise due to slow and gradual loss of structure and/or function of neurons and glial cells and cause different degrees of loss of cognition abilities and sensation. The little success in developing effective treatments imposes a high and regressive economic impact on society, patients and their families. In recent years, regenerative medicine has provided a great opportunity to research new innovative strategies with strong potential to treatleva these diseases. These effects are due to the ability of suitable cells and biomaterials to regenerate damaged nerves with differentiated cells, creating an appropriate environment for recovering or preserving existing healthy neurons and glial cells from destruction and damage. Ultimately, a better understanding and thus a further investigation of stem cell technology, tissue engineering, gene therapy, and exosomes allows progress towards practical and effective treatments for neurodegenerative diseases. Therefore, in this review, advances currently being developed in regenerative medicine using animal models and human clinical trials in neurological disorders are summarized.

The function of previously unappreciated exerkines secreted by muscle in regulation of neurodegenerative diseases

The initiation and progression of neurodegenerative diseases (NDs), distinguished by compromised nervous system integrity, profoundly disrupt the quality of life of patients, concurrently exerting a considerable strain on both the economy and the social healthcare infrastructure. Exercise has demonstrated its potential as both an effective preventive intervention and a rehabilitation approach among the emerging therapeutics targeting NDs. As the largest secretory organ, skeletal muscle possesses the capacity to secrete myokines, and these myokines can partially improve the prognosis of NDs by mediating the muscle-brain axis. Besides the well-studied exerkines, which are secreted by skeletal muscle during exercise that pivotally exert their beneficial function, the physiological function of novel exerkines, e.g., apelin, kynurenic acid (KYNA), and lactate have been underappreciated previously. Herein, this review discusses the roles of these novel exerkines and their mechanisms in regulating the progression and improvement of NDs, especially the significance of their functions in improving NDs' prognoses through exercise. Furthermore, several myokines with potential implications in ameliorating ND progression are proposed as the future direction for investigation. Elucidation of the function of exerkines secreted by skeletal muscle in the regulation of NDs advances the understanding of its pathogenesis and facilitates the development of therapeutics that intervene in these processes to cure NDs.

Unveiling the Molecular Footprint: Proteome-Based Biomarkers for Alzheimer's Disease

Alzheimer's disease (AD) is a devastating neurodegenerative disorder characterized by progressive cognitive decline and memory loss. Early and accurate diagnosis of AD is crucial for implementing timely interventions and developing effective therapeutic strategies. Proteome-based biomarkers have emerged as promising tools for AD diagnosis and prognosis due to their ability to reflect disease-specific molecular alterations. There is of great significance for biomarkers in AD diagnosis and management. It emphasizes the limitations of existing diagnostic approaches and the need for reliable and accessible biomarkers. Proteomics, a field that comprehensively analyzes the entire protein complement of cells, tissues, or bio fluids, is presented as a powerful tool for identifying AD biomarkers. There is a diverse range of proteomic approaches employed in AD research, including mass spectrometry, two-dimensional gel electrophoresis, and protein microarrays. The challenges associated with identifying reliable biomarkers, such as sample heterogeneity and the dynamic nature of the disease. There are well-known proteins implicated in AD pathogenesis, such as amyloid-beta peptides, tau protein, Apo lipoprotein E, and clusterin, as well as inflammatory markers and complement proteins. Validation and clinical utility of proteome-based biomarkers are addressing the challenges involved in validation studies and the diagnostic accuracy of these biomarkers. There is great potential in monitoring disease progression and response to treatment, thereby aiding in personalized medicine approaches for AD patients. There is a great role for bioinformatics and data analysis in proteomics for AD biomarker research and the importance of data preprocessing, statistical analysis, pathway analysis, and integration of multi-omics data for a comprehensive understanding of AD pathophysiology. In conclusion, proteome-based biomarkers hold great promise in the field of AD research. They provide valuable insights into disease mechanisms, aid in early diagnosis, and facilitate personalized treatment strategies. However, further research and validation studies are necessary to harness the full potential of proteome-based biomarkers in clinical practice.

Recipient Reaction and Composition of Autologous Sural Nerve Tissue Grafts into the Human Brain

Parkinson's disease (PD) is a severe neurological disease for which there is no effective treatment or cure, and therefore it remains an unmet need in medicine. We present data from four participants who received autologous transplantation of small pieces of sural nerve tissue into either the basal forebrain containing the nucleus basalis of Meynert (NBM) or the midbrain substantia nigra (SN). The grafts did not exhibit significant cell death or severe host-tissue reaction up to 55 months post-grafting and contained peripheral cells. Dopaminergic neurites showed active growth in the graft area and into the graft in the SN graft, and cholinergic neurites were abundant near the graft in the NBM. These results provide a histological basis for changes in clinical features after autologous peripheral nerve tissue grafting into the NBM or SN in PD.

Enhancement of neural regeneration as a therapeutic strategy for Alzheimer's disease (Review)

Alzheimer's disease (AD), the most common cause of dementia worldwide, has gradually become a global health concern for society and individuals with the process of global ageing. Although extensive research has been carried out on AD, the etiology and pathological mechanism of the disease are still unclear, and there is no specific drug to cure or delay AD progression. The exploration of enhancing nerve regeneration in AD has gradually attracted increasing attention. In the current review, the existing therapeutic strategies were summarized to induce nerve regeneration which can increase the number of neurons, and improve the survival of neurons, the plasticity of synapses and synaptic activity. The strategies include increasing neurotrophic expression (such as brain-derived neurotrophic factor and nerve growth factor), inhibiting acetylcholinesterase (such as donepezil, tacrine, rivastigmine and galanthamine), elevating histone deacetylase levels (such as RGFP-966, Tasquinimod, CM-414 and 44B), stimulating the brain by physiotherapy (such as near-infrared light, repetitive transcranial magnetic stimulation, and transcranial direct current stimulation) and transplanting exogenous neural stem cells. However, further evaluations need to be performed to determine the optimal treatment. The present study reviews recent interventions for enhancing adult neurogenesis and attempts to elucidate their mechanisms of action, which may provide a theoretical basis for inducing nerve regeneration to fight against AD.

Feasibility and therapeutical potential of local intracerebral encapsulated cell biodelivery of BDNF to AppNL-G-F knock-in Alzheimer mice

BACKGROUND

Alzheimer's disease (AD) is an age-related disease characterized by altered cognition, neuroinflammation, and neurodegeneration against which there is presently no effective cure. Brain-derived neurotrophic factor (BDNF) is a key neurotrophin involved in the learning and memory process, with a crucial role in synaptic plasticity and neuronal survival. Several findings support that a reduced BDNF expression in the human brain is associated with AD pathogenesis. BDNF has been proposed as a potential therapy for AD, but BDNF has low brain penetration. In this study, we used an innovative encapsulated cell biodelivery (ECB) device, containing genetically modified cells capable of releasing BDNF and characterized its feasibility and therapeutic effects in the novel App knock-in AD mouse model (AppNL-G-F).

METHODS

ECB's containing human ARPE-19 cells genetically modified to release BDNF (ECB-BDNF devices) were stereotactically implanted bilaterally into hippocampus of 3-month-old AppNL-G-F mice. The stability of BDNF release and its effect on AD pathology were evaluated after 1, 2-, and 4-months post-implantation by immunohistochemical and biochemical analyses. Exploratory and memory performance using elevated plus maze (EPM) and Y-maze test were performed in the 4-months treatment group. Immunological reaction towards ECB-BDNF devices were studied under ex vivo and in vivo settings.

RESULTS

The surgery and the ECB-BDNF implants were well tolerated without any signs of unwanted side effects or weight loss. ECB-BDNF devices did not induce host-mediated immune response under ex vivo set-up but showed reduced immune cell attachment when explanted 4-months post-implantation. Elevated BDNF staining around ECB-BDNF device proximity was detected after 1, 2, and 4 months treatment, but the retrieved devices showed variable BDNF release. A reduction of amyloid-β (Aβ) plaque deposition was observed around ECB-BDNF device proximity after 2-months of BDNF delivery.

CONCLUSIONS

The result of this study supports the use of ECB device as a promising drug-delivery approach to locally administer BBB-impermeable factors for treating neurodegenerative conditions like AD. Optimization of the mouse-sized devices to reduce variability of BDNF release is needed to employ the ECB platform in future pre-clinical research and therapy development studies.

Sustained secretion of human growth hormone from TheraCyte devices encapsulated with PiggyBac-engineered retinal pigment epithelium cells

Growth hormone (GH) deficiency is characterized by impaired growth and development, and is currently treated by repeated administration of recombinant human GH (hGH). Encapsulated cell therapy (ECT) may offer a less demanding treatment-strategy for long-term production and release of GH into circulation. We used PiggyBac-based (PB) transposon delivery for engineering retinal pigment epithelial cells (ARPE-19), and tested a series of viral and non-viral promoters as well as codon-optimization to enhance transgene expression. Engineered cells were loaded into TheraCyte macrocapsules and secretion was followed in vitro and in vivo. The cytomegalovirus (CMV) promoter supports strong and persistent transgene expression, and we achieved clonal cell lines secreting over 6 µg hGH/10⁶ cells/day. Codon-optimization of the hGH gene did not improve secretion. ARPE-19 cells endured encapsulation in TheraCyte devices, and resulted in steady hormone release for at least 60 days in vitro. A short-term pilot experiment in immunodeficient SCID mice demonstrated low systemic levels of hGH from a single 40 µL capsule implanted subcutaneously. No significant increase in weight increase or systemic hGH was detected after 23 days in the GH-deficient lit/SCID mouse model using 4.5 µL capsules loaded with the highest secreting clone of ARPE-19 cells. Our results demonstrate that PB-mediated engineering of ARPE-19 is an efficient way to generate hormone secreting cell lines compatible with macroencapsulation, and our CMV-driven expression cassette allows for identification of clones with high level and long-term secretory activity without addition of insulator elements. Our results pave the way for further in vivo studies of encapsulated cell therapy.

Cell Encapsulation and 3D Bioprinting for Therapeutic Cell Transplantation

The promise of cell therapy has been augmented by introducing biomaterials, where intricate scaffold shapes are fabricated to accommodate the cells within. In this review, we first discuss cell encapsulation and the promising potential of biomaterials to overcome challenges associated with cell therapy, particularly cellular function and longevity. More specifically, cell therapies in the context of autoimmune disorders, neurodegenerative diseases, and cancer are reviewed from the perspectives of preclinical findings as well as available clinical data. Next, techniques to fabricate cell-biomaterials constructs, focusing on emerging 3D bioprinting technologies, will be reviewed. 3D bioprinting is an advancing field that enables fabricating complex, interconnected, and consistent cell-based constructs capable of scaling up highly reproducible cell-biomaterials platforms with high precision. It is expected that 3D bioprinting devices will expand and become more precise, scalable, and appropriate for clinical manufacturing. Rather than one printer fits all, seeing more application-specific printer types, such as a bioprinter for bone tissue fabrication, which would be different from a bioprinter for skin tissue fabrication, is anticipated in the future.

Honey and Alzheimer's Disease-Current Understanding and Future Prospects

Alzheimer's disease (AD), a leading cause of dementia, has been a global concern. AD is associated with the involvement of the central nervous system that causes the characteristic impaired memory, cognitive deficits, and behavioral abnormalities. These abnormalities caused by AD is known to be attributed by extracellular aggregates of amyloid beta plaques and intracellular neurofibrillary tangles. Additionally, genetic factors such as abnormality in the expression of APOE, APP, BACE1, PSEN-1, and PSEN-2 play a role in the disease. As the current treatment aims to treat the symptoms and to slow the disease progression, there has been a continuous search for new nutraceutical agent or medicine to help prevent and cure AD pathology. In this quest, honey has emerged as a powerful nootropic agent. Numerous studies have demonstrated that the high flavonoids and phenolic acids content in honey exerts its antioxidant, anti-inflammatory, and neuroprotective properties. This review summarizes the effect of main flavonoid compounds found in honey on the physiological functioning of the central nervous system, and the effect of honey intake on memory and cognition in various animal model. This review provides a new insight on the potential of honey to prevent AD pathology, as well as to ameliorate the damage in the developed AD.

Prospects for Neurotrophic Factor-Based Early Intervention in Schizophrenia: Lessons Learned from the Effects of Antipsychotic Drugs on Cognition, Neurogenesis, and Neurotrophic Factors

Although reducing psychotic symptoms in schizophrenia has been a major focus of therapeutic interventions for decades, improving cognition is considered a better predictor of functional outcomes. However, the most commonly prescribed antipsychotic drugs (APDs) show only marginal beneficial effects on cognition in patients with schizophrenia. The neural mechanisms underlying cognitive disturbances in schizophrenia remain unknown that making drug development efforts very challenging. Since neurotrophic factors are the primary architects of neurogenesis, synaptic plasticity, learning, and memory, the findings from preclinical and clinical studies that assess changes in neurogenesis and neurotrophic factors and their relationship to cognitive performance in schizophrenia, and how these mechanisms might be impacted by APD treatment, may provide valuable clues in developing therapies to combat cognitive deficit in schizophrenia. Numerous evidence produced over the years suggests a deficit in a wide spectrum of neurotrophic factors in schizophrenia. Since schizophrenia is considered a neurodevelopmental disorder, early intervention with neurotrophic factors may be more effective in ameliorating the cognitive deficits and psychopathological symptoms associated with this pathology. In this context, results from initial clinical trials with neurotrophic factors and their future potential to improve cognition and psychosocial functioning in schizophrenia are discussed.

Depiction of nervous system disorders in television medical drama: A content analysis of 18 seasons of Grey's Anatomy

BACKGROUND

Television medical dramas enjoy great popularity among the general public, and can be a source of information and misinformation about medical disorders. Nervous system disorders have always received attention in popular media, yet no studies have been performed to analyze their depiction and accuracy, to our knowledge.

OBJECTIVE

To investigate the representation of neurological and neurosurgical diseases in Grey's Anatomy, one of most popular and longest running primetime medical melodramas in American television.

METHODS

We performed a quantitative and qualitative content analysis of depictions of nervous system disorders in all 18 seasons of Grey's Anatomy, in addition to investigating the medical accuracy and the global quality of the portrayed medical content.

RESULTS

A total of 285 depictions were identified in 314 out of 400 episodes (78.5%) of Grey's Anatomy. Most of portrayed characters were males (59.2%), Caucasians (72.6%), and adults (76.4%), with a mean age of 32.6 ± 19.7 years for those mentioned. Most of the portrayals were of acute nature (65.5%), with neurosurgical diseases constituting the majority; 85.6%, while 31.6% depicted neurological diseases, and 19.3% had both. The most common clinical presentations were altered level of consciousness (16.5%) and seizures (14.4%). Traumatic brain injury was the most common portrayed diagnosis (39.3%), followed by brain tumors (13.7%), stroke (8.4%), and spinal injury (8.1%). Management was surgical for the majority of cases (79.6%), while only 17.9% received pharmacotherapy. The prognosis of portrayed cases was generally favorable, as 79.5% showed good/full recovery, while mortality rate was 18.6%. Forty cases (14.0%) were depictions of rare to very rare diseases. As regards to medical accuracy, 74.3% of depictions were deemed accurate within reason, with a mean GQS score of 4.38 ± 1.4. Four clinical trials involving the nervous system have been depicted throughout the show.

CONCLUSIONS

Neurosurgical and neurological diseases were portrayed in most episodes of Grey's Anatomy, with a good quality of its scientific content within reason. This study demonstrated that Grey's Anatomy had a good amount of medical information that could be able to improve the public perception of the specialty. However, there is still a room for significant improvement to acknowledge certain inaccuracies and misrepresentations in future episodes.

The Molecular Effects of Environmental Enrichment on Alzheimer's Disease

Environmental enrichment (EE) is an environmental paradigm encompassing sensory, cognitive, and physical stimulation at a heightened level. Previous studies have reported the beneficial effects of EE in the brain, particularly in the hippocampus. EE improves cognitive function as well as ameliorates depressive and anxiety-like behaviors, making it a potentially effective neuroprotective strategy against neurodegenerative diseases such as Alzheimer's disease (AD). Here, we summarize the current evidence for EE as a neuroprotective strategy as well as the potential molecular pathways that can explain the effects of EE from a biochemical perspective using animal models. The effectiveness of EE in enhancing brain activity against neurodegeneration is explored with a view to differences present in early and late life EE exposure, with its potential application in human being discussed. We discuss EE as one of the non pharmacological approaches in preventing or delaying the onset of AD for future research.

Neurotrophin-targeted therapeutics: A gateway to cognition and more?

Neurotrophins, such as brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF), are small proteins expressed in the brain and peripheral tissues, which regulate several key aspects of neuronal function, including neurogenesis, synaptic plasticity and neuroprotection, but also programmed cell death. This broad range of effects is a result of a complex downstream signaling pathway, with differential spatial and temporal activation patterns further diversifying their physiological effects. Alterations in neurotrophin levels, or known polymorphisms in neurotrophin genes, have been linked to a variety of disorders, including depression and Alzheimer's disease (AD). Historically, their therapeutic potential in these disorders has been hampered by the lack of suitable tool molecules for clinical studies. However, recent advancements have led to the development of new therapeutic candidates, which are now in clinical testing.

Immortalized human myoblast cell lines for the delivery of therapeutic proteins using encapsulated cell technology

Despite many promising results obtained in previous preclinical studies, the clinical development of encapsulated cell technology (ECT) for the delivery of therapeutic proteins from macrocapsules is still limited, mainly due to the lack of an allogeneic cell line compatible with therapeutic application in humans. In our work, we generated an immortalized human myoblast cell line specifically tailored for macroencapsulation. In the present report, we characterized the immortalized myoblasts and described the engineering process required for the delivery of functional therapeutic proteins including a cytokine, monoclonal antibodies and a viral antigen. We observed that, when encapsulated, the novel myoblast cell line can be efficiently frozen, stored, and thawed, which limits the challenge imposed by the manufacture and supply of encapsulated cell-based therapeutic products. Our results suggest that this versatile allogeneic cell line represents the next step toward a broader development and therapeutic use of ECT.

Microglia Impairs Proliferation and Induces Senescence In-Vitro in NGF Releasing Cells Used in Encapsulated Cell Biodelivery for Alzheimer's Disease Therapy

There is no cure yet available for Alzheimer's disease (AD). We recently optimized encapsulated cell biodelivery (ECB) devices releasing human mature nerve growth factor (hmNGF), termed ECB-NGF, to the basal forebrain of AD patients. The ECB-NGF delivery resulted in increased CSF cholinergic markers, improved glucose metabolism, and positive effects on cognition in AD patients. However, some ECB-NGF implants showed altered hmNGF release post-explantation. To optimize the ECB-NGF platform for future therapeutic purposes, we initiated in-vitro optimization studies by exposing ECB-NGF devices to physiological factors present within the AD brain. We report here that microglia cells can impair hmNGF release from ECB-NGF devices in-vitro, which can be reversed by transferring the devices to fresh culture medium. Further, we exposed the hmNGF secreting human ARPE-19 cell line (NGC0211) to microglia (HMC3) conditioned medium (MCM; untreated or treated with IL-1β/IFNγ/Aβ₄₀/Aβ₄₂), and evaluated biochemical stress markers (ROS, GSH, ΔΨ_m, and Alamar Blue assay), cell death indicators (Annexin-V/PI), cell proliferation (CFSE retention and Ki67) and senescence markers (SA-β-gal) in NGC0211 cells. MCMs from activated microglia reduced cell proliferation and induced cell senescence in NGC0211 cells, which otherwise resist biochemical alterations and cell death. These data indicate a critical but reversible impact of activated microglia on NGC0211 cells.

The synapse as a treatment avenue for Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disorder with devastating symptoms, including memory impairments and cognitive deficits. Hallmarks of AD pathology are amyloid-beta (Aβ) deposition forming neuritic plaques and neurofibrillary tangles (NFTs). For many years, AD drug development has mainly focused on directly targeting the Aβ aggregation or the formation of tau tangles, but this disease has no cure so far. Other common characteristics of AD are synaptic abnormalities and dysfunctions such as synaptic damage, synaptic loss, and structural changes in the synapse. Those anomalies happen in the early stages of the disease before behavioural symptoms have occurred. Therefore, better understanding the mechanisms underlying the synaptic dysfunction found in AD and targeting the synapse, especially using early treatment windows, can lead to finding novel and more effective treatments that could improve the lives of AD patients. Researchers have recently started developing different disease-modifying treatments targeting the synapse to rescue and prevent synaptic dysfunction in AD. The main objectives of these new strategies are to halt synaptic loss, strengthen synaptic connections, and improve synaptic density, potentially leading to the rescue or prevention of cognitive impairments. This article aims to address the mechanisms of synaptic degeneration in AD and discuss current strategies that focus on the synapse for AD therapy. Alzheimer's disease (AD) is a neurodegenerative disorder that significantly impairs memory and causes cognitive and behavioural deficits. Scientists worldwide have tried to find a treatment that can reverse or rescue AD symptoms, but there is no cure so far. One prominent characteristic of AD is the brain atrophy caused by significant synaptic loss and overall neuronal damage, which starts at the early stages of the disease before other AD hallmarks such as neuritic plaques and NFTs. The present review addresses the underlying mechanisms behind synaptic loss and dysfunction in AD and discusses potential strategies that target the synapse.

The combination of autologous mesenchymal stem cell-derived exosomes and neurotrophic factors as an intervention for amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis is a chronic progressive degeneration of motor neurons and has a high mortality. Riluzole and edaravone are the only approved medications currently being used for amyotrophic lateral sclerosis in clinical settings. However, they can lead to serious complications, such as injuries to the liver and kidney. To date, there is no effective treatment for amyotrophic lateral sclerosis. In this regard, investigations concerning the employment of exosomes, mesenchymal stem cells, and neurotrophic factors to ameliorate amyotrophic lateral sclerosis are attracting considerable attention in the scientific community. Herein, we systematically analyze the relationship relevant to autologous mesenchymal stem cell derived-exosomes, neurotrophic factors and amyotrophic lateral sclerosis. Mesenchymal stem cells modulate immune response, mitigate oxidative stress, promote neuronal regeneration, and differentiate into neuronal and glial cells. Furthermore, exosomes from mesenchymal stem cells exert beneficial effects on their mother cells by preventing abnormal differentiation of mesenchymal stem cells. Similarly, neurotrophic factors regulate inflammatory response, stimulate the neuron repair, and the recovery of neuronal functioning. Therefore, autologous mesenchymal stem cells-derived exosomes combined with neurotrophic factors could potentially be an effective interventional medium for amyotrophic lateral sclerosis.

Ultrasound delivery of a TrkA agonist confers neuroprotection to Alzheimer-associated pathologies

Early degeneration of basal forebrain cholinergic neurons (BFCNs) contributes substantially to cognitive decline in Alzheimer's disease (AD). Evidence from preclinical models of neuronal injury and aging support a pivotal role for nerve growth factor (NGF) in neuroprotection, resilience, and cognitive function. However, whether NGF can provide therapeutic benefit in the presence of AD-related pathologies remains unresolved. Perturbations in the NGF signaling system in AD may render neurons unable to benefit from NGF administration. Additionally, challenges related to brain delivery remain for clinical translation of NGF-based therapies in AD. To be safe and efficient, NGF-related agents should stimulate the NGF receptor, tropomyosin receptor kinase A (TrkA), avoid activation through the p75 neurotrophin receptor (p75NTR), and be delivered non-invasively to targeted brain areas using real-time monitoring. We addressed these limitations using MRI-guided focused ultrasound (MRIgFUS) to increase blood-brain barrier (BBB) permeability locally and transiently, allowing an intravenously administered TrkA agonist that does not activate p75NTR, termed D3, to enter targeted brain areas. Here, we report the therapeutic potential of selective TrkA activation in a transgenic mouse model that recapitulates numerous AD-associated pathologies. Repeated MRIgFUS-mediated delivery of D3 (D3/FUS) improved cognitive function in the TgCRND8 model of AD. Mechanistically, D3/FUS treatment effectively attenuated cholinergic degeneration and promoted functional recovery. D3/FUS treatment also resulted in widespread reduction of brain amyloid pathology and dystrophic neurites surrounding amyloid plaques. Furthermore, D3/FUS markedly enhanced hippocampal neurogenesis in TgCRND8 mice, implicating TrkA agonism as a novel therapeutic target to promote neurogenesis in the context of AD-related pathology. Thus, this study provides evidence that selective TrkA agonism confers neuroprotection to effectively counteract AD-related vulnerability. Recent clinical trials demonstrate that non-invasive BBB modulation using MRIgFUS is safe, feasible and reversible in AD patients. TrkA receptor agonists coupled with MRIgFUS delivery constitute a promising disease-modifying strategy to foster brain health and counteract cognitive decline in AD.

A Review of Potential Novel Glaucoma Therapeutic Options Independent of Intraocular Pressure

Glaucoma, a progressive optic neuropathy characterized by retinal ganglion cell degeneration and visual field loss, is the leading cause of irreversible blindness worldwide. Intraocular pressure (IOP) is presently the only modifiable risk factor demonstrated to slow or halt disease progression; however, glaucomatous damage persists in almost 50% of patients despite significant IOP reduction. Many studies have investigated the non-IOP-related risk factors that contribute to glaucoma progression as well as interventions that can prevent or delay glaucomatous neurodegeneration and preserve vision throughout life, independently of IOP. A vast number of experimental studies have reported effective neuroprotection in glaucoma, and clinical studies are ongoing attempting to provide strong evidence of effectiveness of these interventions. In this review, we look into the current understanding of the pathophysiology of glaucoma and explore the recent advances in non-IOP related strategies for neuroprotection and neuroregeneration in glaucoma.

Intranasal Delivery of Nerve Growth Factor in Neurodegenerative Diseases and Neurotrauma

Since the 1980s, the development of a pharmacology based on nerve growth factor (NGF) has been postulated for the therapy of Alzheimer’s disease (AD). This hypothesis was based on the rescuing effect of the neurotrophin on the cholinergic phenotype of the basal forebrain neurons, primarily compromised during the development of AD. Subsequently, the use of NGF was put forward to treat a broader spectrum of neurological conditions affecting the central nervous system, such as Parkinson’s disease, degenerative retinopathies, severe brain traumas and neurodevelopmental dysfunctions. While supported by solid rational assumptions, the progress of a pharmacology founded on these hypotheses has been hampered by the difficulty of conveying NGF towards the brain parenchyma without resorting to invasive and risky delivery methods. At the end of the last century, it was shown that NGF administered intranasally to the olfactory epithelium was able to spread into the brain parenchyma. Notably, after such delivery, pharmacologically relevant concentration of exogenous NGF was found in brain areas located at considerable distances from the injection site along the rostral-caudal axis. These observations paved the way for preclinical characterization and clinical trials on the efficacy of intranasal NGF for the treatment of neurodegenerative diseases and of the consequences of brain trauma. In this review, a summary of the preclinical and clinical studies published to date will be attempted, as well as a discussion about the mechanisms underlying the efficacy and the possible development of the pharmacology based on intranasal conveyance of NGF to the brain.

Luteolin stimulates the NGF-induced neurite outgrowth in cultured PC12 cells through binding with NGF and potentiating its receptor signaling

Luteolin, a flavonoid in fruits and vegetables, has neurotrophic functions without a well-characterized mechanism. Here, we hypothesize a direct interaction of luteolin with nerve growth factor (NGF); as such, the functionality of the NGF could be potentiated. The direct binding of luteolin with NGF was validated by ultra-filtration, Biacore, and docking analyses. In cultured PC12 cells, application of luteolin in combination with a low dose of NGF potentiated the NGF-induced differentiation of neurons by an increase of the differentiated cell number to 25.4 ± 4.8% (p < 0.01), as well as the increased expression of neurofilaments by 119 ± 32.1% (p < 0.05), 191 ± 12.6% (p < 0.01), and 110 ± 23.4% (p < 0.05) for NF68, NF160 and NF200, respectively. The co-treatment induced the phosphorylations of tropomyosin receptor kinase A (TrkA), extracellular signal-regulated kinase 1/2 (ERK1/2), protein kinase B (Akt), phospholipase C-γ1 (PLCγ1), and cAMP response element-binding protein (CREB) by 2 to 3 fold: these induced phosphorylations were mimicking that of a high dose of NGF. Moreover, the application of the TrkA inhibitor, K252a, blocked the luteolin-mediated induction of neurofilament expression and neurite outgrowth in cultured PC12 cells, suggesting the target specificity. The result supports the development of luteolin as a therapeutic, or preventive, agent for NGF insufficiency-associated neurodegenerative diseases.

Amyloid-Beta Peptides and Activated Astroglia Impairs Proliferation of Nerve Growth Factor Releasing Cells In Vitro: Implication for Encapsulated Cell Biodelivery-Mediated AD Therapy

Alzheimer’s disease (AD) treatment is constrained due to the inability of peripherally administered therapeutic molecules to cross the blood–brain barrier. Encapsulated cell biodelivery (ECB) devices, a tissue-targeted approach for local drug release, was previously optimized for human mature nerve growth factor (hmNGF) delivery in AD patients but was found to have reduced hmNGF release over time. To understand the reason behind reduced ECB efficacy, we exposed hmNGF-releasing cells (NGC0211) in vitro to human cerebrospinal fluid (CSF) obtained from Subjective Cognitive Impairment (SCI), Lewy Body Dementia (LBD), and AD patients. Subsequently, we exposed NGC0211 cells directly to AD-related factors like amyloid-β peptides (Aβ_40/42) or activated astrocyte-conditioned medium (Aβ_40/42/IL-1β/TNFα-treated) and evaluated biochemical stress markers, cell death indicators, cell proliferation marker (Ki67), and hmNGF release. We found that all patients’ CSF significantly reduced hmNGF release from NGC0211 cells in vitro. Aβ_40/42, inflammatory molecules, and activated astrocytes significantly affected NGC0211 cell proliferation without altering hmNGF release or other parameters important for essential functions of the NGC0211 cells. Long-term constant cell proliferation within the ECB device is critically important to maintain a steady cell population needed for stable mNGF release. These data show hampered proliferation of NGC0211 cells, which may lead to a decline of the NGC0211 cell population in ECBs, thereby reducing hmNGF release. Our study highlights the need for future studies to strengthen ECB-mediated long-term drug delivery approaches.

The Development of Pharmacological Therapies for Alzheimer's Disease

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder that currently has no cure. The aged population is growing globally, creating an urgent need for more promising therapies for this debilitating disease. Much effort has been made in recent decades, and the field is highly dynamic, with numerous trials. The main focus of these trials includes disease modification and symptomatic treatment. Some have shown beneficial outcomes, while others have shown no significant benefits. Here, we cover the outcome of recently published AD clinical trials, as well as the mechanism of action of these therapeutical agents, to re-think drug development strategies and directions for future studies.

CSF and Plasma Cholinergic Markers in Patients With Cognitive Impairment

Introduction

Alzheimer’s disease (AD) is the most prevalent form of dementia with symptoms of deteriorating cognitive functions and memory loss, partially as a result of a decrease in cholinergic neurotransmission. The disease is incurable and treatment with cholinesterase inhibitors (ChEIs) is symptomatic. Choline acetyltransferase (ChAT), the enzyme that synthesizes acetylcholine (ACh), has been proven recently to be present in both cerebrospinal fluid (CSF) and plasma. As ChAT plays a role in regulating the extracellular ACh levels, it may have an impact on prognosis and cognitive performance in AD patients.

Objectives

To measure ChAT activity and its protein concentration in CSF and plasma from patients with AD, mild cognitive impairment (MCI), or Subjective cognitive impairment (SCI).

Methods

Plasma and CSF samples were obtained from 21 AD, 32 MCI, and 30 SCI patients. The activity and protein levels of ChAT and acetylcholinesterase (AChE), the enzyme catalyzing the hydrolysis of ACh, were analyzed using an integrated activity and protein concentration ELISA-like assay. A Cholinergic Index was calculated as the ratio of ChAT to AChE activities in CSF. The data were analyzed in relation to dementia biomarkers and cognitive performance of the patients.

Results

The CSF ChAT activity was significantly higher (55–67%) in MCI patients compared to AD and SCI cases. The CSF Cholinergic Index was 41 and 22% lower in AD patients than in MCI and SCI subjects, respectively. This index correlated positively with the Aβ₄₂/p-tau ratio in CSF in SCI but negatively with that in AD and MCI. The ChAT activity and protein levels in plasma exhibited significant differences with the pattern of AD>>MCI>SCI.

Conclusion

This is the first study investigating soluble levels of the key cholinergic enzyme, ChAT, in both plasma and CSF of individuals at different clinical stages of dementia. Although further validation is needed, the overall pattern of the results suggests that in the continuum of AD, the cholinergic signaling exhibits an inverse U-shape dynamic of changes in the brain that greatly differs from the changes observed in the plasma compartment.

Gene therapy in epilepsy

Gene therapy may constitute a promising alternative to conventional pharmacological tools and surgeries for epilepsy. For primary epilepsy, a single variant leading to a significant effect is relatively rare, while other forms are considered complex in inheritances with multiple susceptible mutations and impacts from the environment. Gene therapy in preclinical models of epilepsy has attempted to perform antiepileptogenic, anticonvulsant, or disease-modifying effects during epileptogenesis or after establishing the disease. Creating gene vectors tailored for different situations is the key to expanding gene therapy, and choosing the appropriate therapeutic target remains another fundamental problem. A variety of treatment strategies, from overexpressing inhibitory neuropeptides to modulating the expression of neurotransmitters or ion channels, have been tested in animal models. Additionally, emerging new approaches of optogenetics and chemogenetics, as well as genome-editing tools will further boost the prosperity of gene therapy. This review summarizes the experience obtained to date and discusses the challenges and opportunities in clinical translations.

A Review of Techniques for Biodelivery of Nerve Growth Factor (NGF) to the Brain in Relation to Alzheimer's Disease

Age-dependent progressive neurodegeneration and associated cognitive dysfunction represent a serious concern worldwide. Currently, dementia accounts for the fifth highest cause of death, among which Alzheimer's disease (AD) represents more than 60% of the cases. AD is associated with progressive cognitive dysfunction which affects daily life of the affected individual and associated family. The cognitive dysfunctions are at least partially due to the degeneration of a specific set of neurons (cholinergic neurons) whose cell bodies are situated in the basal forebrain region (basal forebrain cholinergic neurons, BFCNs) but innervate wide areas of the brain. It has been explicitly shown that the delivery of the neurotrophic protein nerve growth factor (NGF) can rescue BFCNs and restore cognitive dysfunction, making NGF interesting as a potential therapeutic substance for AD. Unfortunately, NGF cannot pass through the blood-brain barrier (BBB) and thus peripheral administration of NGF protein is not viable therapeutically. NGF must be delivered in a way which will allow its brain penetration and availability to the BFCNs to modulate BFCN activity and viability. Over the past few decades, various methodologies have been developed to deliver NGF to the brain tissue. In this chapter, NGF delivery methods are discussed in the context of AD.

Identification of Novel Positive Allosteric Modulators of Neurotrophin Receptors for the Treatment of Cognitive Dysfunction

Alzheimer's disease (AD) is the most common neurodegenerative disorder and results in severe neurodegeneration and progressive cognitive decline. Neurotrophins are growth factors involved in the development and survival of neurons, but also in underlying mechanisms for memory formation such as hippocampal long-term potentiation. Our aim was to identify small molecules with stimulatory effects on the signaling of two neurotrophins, the nerve growth factor (NGF) and the brain derived neurotrophic factor (BDNF). To identify molecules that could potentiate neurotrophin signaling, 25,000 molecules were screened, which led to the identification of the triazinetrione derivatives ACD855 (Ponazuril) and later on ACD856, as positive allosteric modulators of tropomyosin related kinase (Trk) receptors. ACD855 or ACD856 potentiated the cellular signaling of the neurotrophin receptors with EC50 values of 1.9 and 3.2 or 0.38 and 0.30 µM, respectively, for TrkA or TrkB. ACD855 increased acetylcholine levels in the hippocampus by 40% and facilitated long term potentiation in rat brain slices. The compounds acted as cognitive enhancers in a TrkB-dependent manner in several different behavioral models. Finally, the age-induced cognitive dysfunction in 18-month-old mice could be restored to the same level as found in 2-month-old mice after a single treatment of ACD856. We have identified a novel mechanism to modulate the activity of the Trk-receptors. The identification of the positive allosteric modulators of the Trk-receptors might have implications for the treatment of Alzheimer's diseases and other diseases characterized by cognitive impairment.

Nerve Growth Factor Biodelivery: A Limiting Step in Moving Toward Extensive Clinical Application?

Nerve growth factor (NGF) was the first-discovered member of the neurotrophin family, a class of bioactive molecules which exerts powerful biological effects on the CNS and other peripheral tissues, not only during development, but also during adulthood. While these molecules have long been regarded as potential drugs to combat acute and chronic neurodegenerative processes, as evidenced by the extensive data on their neuroprotective properties, their clinical application has been hindered by their unexpected side effects, as well as by difficulties in defining appropriate dosing and administration strategies. This paper reviews aspects related to the endogenous production of NGF in healthy and pathological conditions, along with conventional and biomaterial-assisted delivery strategies, in an attempt to clarify the impediments to the clinical application of this powerful molecule.

Optimized Protocol for Subcutaneous Implantation of Encapsulated Cells Device and Evaluation of Biocompatibility

Improving a drug delivery system is critical to treat central nervous system disorders. Here we studied an innovative approach based on implantation of a wireless-powered cell-based device in mice. This device, coupling biologic material and electronics, is the first of its kind. The advantage of this technology is its ability to control the secretion of a therapeutic molecule and to switch the classical permanent delivery to activation on demand. In diseases with relapsing-remitting phases such as multiple sclerosis, such activation could be selectively achieved in relapsing phases. However, the safety (tolerance to biomaterials and surgical procedure) of such a clinical device needs to be verified. Therefore, the development of tools to assess the biocompatibility of the system in animal models is an essential step. We present the development of this new therapeutic approach, the challenges we encountered during the different steps of its development (such as cell loading in the chamber, surgery protocol for subcutaneous implantation of the device) and the tools we used to evaluate cell viability and biocompatibility of the device.

Shared Genetic Etiology between Alzheimer's Disease and Blood Levels of Specific Cytokines and Growth Factors

Late-onset Alzheimer’s disease (AD) has a significant genetic and immunological component, but the molecular mechanisms through which genetic and immunity-related risk factors and their interplay contribute to AD pathogenesis are unclear. Therefore, we screened for genetic sharing between AD and the blood levels of a set of cytokines and growth factors to elucidate how the polygenic architecture of AD affects immune marker profiles. For this, we retrieved summary statistics from Finnish genome-wide association studies of AD and 41 immune marker blood levels and assessed for shared genetic etiology, using a polygenic risk score-based approach. For the blood levels of 15 cytokines and growth factors, we identified genetic sharing with AD. We also found positive and negative genetic concordances—implying that genetic risk factors for AD are associated with higher and lower blood levels—for several immune markers and were able to relate some of these results to the literature. Our results imply that genetic risk factors for AD also affect specific immune marker levels, which may be leveraged to develop novel treatment strategies for AD.

Peptides Derived from Growth Factors to Treat Alzheimer's Disease

Alzheimer's disease (AD) is a devastating neurodegenerative disease characterized by progressive neuron losses in memory-related brain structures. The classical features of AD are a dysregulation of the cholinergic system, the accumulation of amyloid plaques, and neurofibrillary tangles. Unfortunately, current treatments are unable to cure or even delay the progression of the disease. Therefore, new therapeutic strategies have emerged, such as the exogenous administration of neurotrophic factors (e.g., NGF and BDNF) that are deficient or dysregulated in AD. However, their low capacity to cross the blood-brain barrier and their exorbitant cost currently limit their use. To overcome these limitations, short peptides mimicking the binding receptor sites of these growth factors have been developed. Such peptides can target selective signaling pathways involved in neuron survival, differentiation, and/or maintenance. This review focuses on growth factors and their derived peptides as potential treatment for AD. It describes (1) the physiological functions of growth factors in the brain, their neuronal signaling pathways, and alteration in AD; (2) the strategies to develop peptides derived from growth factor and their capacity to mimic the role of native proteins; and (3) new advancements and potential in using these molecules as therapeutic treatments for AD, as well as their limitations.

Neuroprotective Natural Products for Alzheimer's Disease

Alzheimer's disease (AD) is the number one neurovegetative disease, but its treatment options are relatively few and ineffective. In efforts to discover new strategies for AD therapy, natural products have aroused interest in the research community and in the pharmaceutical industry for their neuroprotective activity, targeting different pathological mechanisms associated with AD. A wide variety of natural products from different origins have been evaluated preclinically and clinically for their neuroprotective mechanisms in preventing and attenuating the multifactorial pathologies of AD. This review mainly focuses on the possible neuroprotective mechanisms from natural products that may be beneficial in AD treatment and the natural product mixtures or extracts from different sources that have demonstrated neuroprotective activity in preclinical and/or clinical studies. It is believed that natural product mixtures or extracts containing multiple bioactive compounds that can work additively or synergistically to exhibit multiple neuroprotective mechanisms might be an effective approach in AD drug discovery.

Contemporary Transposon Tools: A Review and Guide through Mechanisms and Applications of Sleeping Beauty, piggyBac and Tol2 for Genome Engineering

Transposons are mobile genetic elements evolved to execute highly efficient integration of their genes into the genomes of their host cells. These natural DNA transfer vehicles have been harnessed as experimental tools for stably introducing a wide variety of foreign DNA sequences, including selectable marker genes, reporters, shRNA expression cassettes, mutagenic gene trap cassettes, and therapeutic gene constructs into the genomes of target cells in a regulated and highly efficient manner. Given that transposon components are typically supplied as naked nucleic acids (DNA and RNA) or recombinant protein, their use is simple, safe, and economically competitive. Thus, transposons enable several avenues for genome manipulations in vertebrates, including transgenesis for the generation of transgenic cells in tissue culture comprising the generation of pluripotent stem cells, the production of germline-transgenic animals for basic and applied research, forward genetic screens for functional gene annotation in model species and therapy of genetic disorders in humans. This review describes the molecular mechanisms involved in transposition reactions of the three most widely used transposon systems currently available (Sleeping Beauty, piggyBac, and Tol2), and discusses the various parameters and considerations pertinent to their experimental use, highlighting the state-of-the-art in transposon technology in diverse genetic applications.

Elevated Levels of miR-144-3p Induce Cholinergic Degeneration by Impairing the Maturation of NGF in Alzheimer's Disease

Cholinergic degeneration is one of the key pathological hallmarks of Alzheimer’s disease (AD), a condition that is characterized by synaptic disorders and memory impairments. Nerve growth factor (NGF) is secreted in brain regions that receive projections from the basal forebrain cholinergic neurons. The trophic effects of NGF rely on the appropriate maturation of NGF from its precursor, proNGF. The ratio of proNGF/NGF is known to be increased in patients with AD; however, the mechanisms that underlie this observation have yet to be elucidated. Here, we demonstrated that levels of miR-144-3p are increased in the hippocampi and the medial prefrontal cortex of an APP/PS1 mouse model of AD. These mice also exhibited cholinergic degeneration (including the loss of cholinergic fibers, the repression of choline acetyltransferase (ChAT) activity, the reduction of cholinergic neurons, and an increased number of dystrophic neurites) and synaptic/memory deficits. The elevated expression of miR-144-3p specifically targets the mRNA of tissue plasminogen activator (tPA) and reduces the expression of tPA, thus resulting in the abnormal maturation of NGF. The administration of miR-144-3p fully replicated the cholinergic degeneration and synaptic/memory deficits observed in the APP/PS1 mice. The injection of an antagomir of miR-144-3p into the hippocampi partially rescued cholinergic degeneration and synaptic/memory impairments by restoring the levels of tPA protein and by correcting the ratio of proNGF/NGF. Collectively, our research revealed potential mechanisms for the disturbance of NGF maturation and cholinergic degeneration in AD and identified a potential therapeutic target for AD.

Injectable Glycosaminoglycan-Based Cryogels from Well-Defined Microscale Templates for Local Growth Factor Delivery

Glycosaminoglycan-based hydrogels hold great potential for applications in tissue engineering and regenerative medicine. By mimicking the natural extracellular matrix processes of growth factor binding and release, such hydrogels can be used as a sustained delivery device for growth factors. Since neural networks commonly follow well-defined, high-aspect-ratio paths through the central and peripheral nervous system, we sought to create a fiber-like, elongated growth factor delivery system. Cryogels, with networks formed at subzero temperatures, are well-suited for the creation of high-aspect-ratio biomaterials, because they have a macroporous structure making them mechanically robust (for ease of handling) yet soft and highly compressible (for interfacing with brain tissue). Unlike hydrogels, cryogels can be synthesized in advance of their use, stored with ease, and rehydrated quickly to their original shape. Herein, we use solvent-assisted microcontact molding to form sacrificial templates, in which we produced highly porous cryogel microscale scaffolds with a well-defined elongated shape via the photopolymerization of poly(ethylene glycol) diacrylate and maleimide-functionalized heparin. Dissolution of the template yielded cryogels that could load nerve growth factor (NGF) and release it over a period of 2 weeks, causing neurite outgrowth in PC12 cell cultures. This microscale template-assisted synthesis technique allows tight control over the cryogel scaffold dimensions for high reproducibility and ease of injection through fine gauge needles.

Bridging Scales in Alzheimer's Disease: Biological Framework for Brain Simulation With The Virtual Brain

Despite the acceleration of knowledge and data accumulation in neuroscience over the last years, the highly prevalent neurodegenerative disease of AD remains a growing problem. Alzheimer's Disease (AD) is the most common cause of dementia and represents the most prevalent neurodegenerative disease. For AD, disease-modifying treatments are presently lacking, and the understanding of disease mechanisms continues to be incomplete. In the present review, we discuss candidate contributing factors leading to AD, and evaluate novel computational brain simulation methods to further disentangle their potential roles. We first present an overview of existing computational models for AD that aim to provide a mechanistic understanding of the disease. Next, we outline the potential to link molecular aspects of neurodegeneration in AD with large-scale brain network modeling using The Virtual Brain (www.thevirtualbrain.org), an open-source, multiscale, whole-brain simulation neuroinformatics platform. Finally, we discuss how this methodological approach may contribute to the understanding, improved diagnostics, and treatment optimization of AD.

Nerve Growth Factor as an Ocular Therapy: Applications, Challenges, and Future Directions

Nerve growth factor (NGF), the prototypical neurotrophin first discovered in the 1950s, has recently garnered increased interest as a therapeutic agent promoting neuronal health and regeneration. After gaining orphan drug status within the last decade, NGF-related research and drug development has accelerated. The purpose of this article is to review the preclinical and clinical evidence of NGF in various applications, including central and peripheral nervous system, skin, and ophthalmic disorders. We focus on the ophthalmic applications including not only the FDA-approved indication of neurotrophic keratitis but also retinal disease and glaucoma. NGF represents a promising therapy whose therapeutic profile is evolving. The challenges related to this therapy are reviewed, along with possible solutions and future directions.

Targeted Delivery for Neurodegenerative Disorders Using Gene Therapy Vectors: Gene Next Therapeutic Goals

The technique of gene therapy, ever since its advent nearly fifty years ago, has been utilized by scientists as a potential treatment option for various disorders. This review discusses some of the major neurodegenerative diseases (NDDs) like Alzheimer's disease (AD), Parkinson's Disease (PD), Motor neuron diseases (MND), Spinal Muscular Atrophy (SMA), Huntington's Disease (HD), Multiple Sclerosis (MS), etc. and their underlying genetic mechanisms along with the role that gene therapy can play in combating them. The pathogenesis and the molecular mechanisms specifying the altered gene expression of each of these NDDs have also been discussed in elaboration. The use of gene therapy vectors can prove to be an effective tool in the field of curative modern medicine for the generations to come. Therefore, consistent efforts and progressive research towards its implementation can provide us with powerful treatment options for disease conditions that have so far been considered as incurable.

Targeting for Success: Demonstrating Proof-of-Concept with Mechanistic Early Phase Clinical Pharmacology Studies for Disease-Modification in Neurodegenerative Disorders

The clinical failure rate for disease-modifying treatments (DMTs) that slow or stop disease progression has been nearly 100% for the major neurodegenerative disorders (NDDs), with many compounds failing in expensive and time-consuming phase 2 and 3 trials for lack of efficacy. Here, we critically review the use of pharmacological and mechanistic biomarkers in early phase clinical trials of DMTs in NDDs, and propose a roadmap for providing early proof-of-concept to increase R&D productivity in this field of high unmet medical need. A literature search was performed on published early phase clinical trials aimed at the evaluation of NDD DMT compounds using MESH terms in PubMed. Publications were selected that reported an early phase clinical trial with NDD DMT compounds between 2010 and November 2020. Attention was given to the reported use of pharmacodynamic (mechanistic and physiological response) biomarkers. A total of 121 early phase clinical trials were identified, of which 89 trials (74%) incorporated one or multiple pharmacodynamic biomarkers. However, only 65 trials (54%) used mechanistic (target occupancy or activation) biomarkers to demonstrate target engagement in humans. The most important categories of early phase mechanistic and response biomarkers are discussed and a roadmap for incorporation of a robust biomarker strategy for early phase NDD DMT clinical trials is proposed. As our understanding of NDDs is improving, there is a rise in potentially disease-modifying treatments being brought to the clinic. Further increasing the rational use of mechanistic biomarkers in early phase trials for these (targeted) therapies can increase R&D productivity with a quick win/fast fail approach in an area that has seen a nearly 100% failure rate to date.

The Cholinergic System, the Adrenergic System and the Neuropathology of Alzheimer's Disease

Neurodegenerative diseases are a major public health problem worldwide with a wide spectrum of symptoms and physiological effects. It has been long reported that the dysregulation of the cholinergic system and the adrenergic system are linked to the etiology of Alzheimer’s disease. Cholinergic neurons are widely distributed in brain regions that play a role in cognitive functions and normal cholinergic signaling related to learning and memory is dependent on acetylcholine. The Locus Coeruleus norepinephrine (LC-NE) is the main noradrenergic nucleus that projects and supplies norepinephrine to different brain regions. Norepinephrine has been shown to be neuroprotective against neurodegeneration and plays a role in behavior and cognition. Cholinergic and adrenergic signaling are dysregulated in Alzheimer’s disease. The degeneration of cholinergic neurons in nucleus basalis of Meynert in the basal forebrain and the degeneration of LC-NE neurons were reported in Alzheimer’s disease. The aim of this review is to describe current literature on the role of the cholinergic system and the adrenergic system (LC-NE) in the pathology of Alzheimer’s disease and potential therapeutic implications.

Gene and cell therapy for the nucleus basalis of Meynert with NGF in Alzheimer's disease

There is currently no effective treatment for the most common of the dementia disorders, Alzheimer's disease (AD). It has been known for decades that the central cholinergic system is important for memory. The cholinergic neurons in the basal forebrain with its cortical and hippocampal projections degenerate in AD and thus contribute to the cognitive decline characteristic of AD. This knowledge led to the development of the currently approved treatment for AD, with inhibitors of acetylcholine-esterase targeting the cholinergic system with beneficial but mild effects. In recent years, other approaches to influence the degenerating cholinergic system in AD focusing on nerve growth factor (NGF) have been undertaken. NGF is required for the survival and function of the basal forebrain cholinergic neurons, the most important being the nucleus basalis of Meynert (nbM). Since there is a lack of NGF and its receptors in the AD forebrain, the hypothesis is that local delivery of NGF to the nbM could revive the cholinergic circuitry and thereby restore cognitive functions. Since NGF does not pass through the blood-brain barrier, approaches involving cerebral injections of genetically modified cells or viral vectors or implantation of encapsulated cells in the nbM in AD patients have been used. These attempts have been partially successful but also have limitations, which are presented and discussed here. In conclusion, these trials point to the importance of further development of NGF-related therapies in AD.

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

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

Is Combining an Anticholinergic with a Cholinesterase Inhibitor a Good Strategy for High-Level CNS Cholinesterase Inhibition?

The currently approved cholinesterase inhibitors (donepezil, rivastigmine, and galantamine) produce gastrointestinal toxicity which limits dosing to that which produces only about 25% to 35% CNS cholinesterase inhibition in Alzheimer's disease patients undergoing treatment, below the minimum therapeutic target of about 40% to 50% CNS inhibition considered necessary to treat cognitive impairment. A recent strategy for producing high-level CNS acetylcholinesterase (AChE) inhibition (50% or higher) is to co-administer a muscarinic anticholinergic with the AChE inhibitor to block the dose-limiting cholinergic overstimulation of the gastrointestinal system, allow more robust AChE inhibition in the CNS, and improve efficacy in the treatment of Alzheimer's disease. Unfortunately, most common muscarinic anticholinergics, including solifenacin, readily penetrate the CNS and are directly associated with long-term exacerbation of the underlying neuropathology of Alzheimer's disease and increased brain atrophy. The co-administration of an anticholinergic with an AChE inhibitor is a rational strategy for improving efficacy in the symptomatic treatment of dementia, but there are significant long-term risks that have not yet been considered. For long-term safety against accelerating the underlying disease processes in Alzheimer's disease, anticholinergics used to increase the tolerability of AChE inhibitors should not penetrate, or have very limited penetration, of the blood-brain barrier. Neurotrophic-mediated mechanisms by which cholinergic drugs may affect neurodegeneration in Alzheimer's disease are explored and improved treatment options are suggested.

In vitro platform establishes antigen-specific CD8+ T cell cytotoxicity to encapsulated cells via indirect antigen recognition

The curative potential of non-autologous cellular therapy is hindered by the requirement of anti-rejection therapy. Cellular encapsulation within nondegradable biomaterials has the potential to inhibit immune rejection, but the efficacy of this approach in robust preclinical and clinical models remains poor. While the responses of innate immune cells to the encapsulating material have been characterized, little attention has been paid to the contributions of adaptive immunity in encapsulated graft destabilization. Avoiding the limitations of animal models, we established an efficient, antigen-specific in vitro platform capable of delineating direct and indirect host T cell recognition to microencapsulated cellular grafts and evaluated their consequential impacts. Using ovalbumin (OVA) as a model antigen, we determined that alginate microencapsulation abrogates direct CD8+ T cell activation by interrupting donor-host interaction; however, indirect T cell activation, mediated by host antigen presenting cells (APCs) primed with shed donor antigens, still occurs. These activated T cells imparted cytotoxicity on the encapsulated cells, likely via diffusion of cytotoxic solutes. Overall, this platform delivers unique mechanistic insight into the impacts of hydrogel encapsulation on host adaptive immune responses, comprehensively addressing a long-standing hypothesis of the field. Furthermore, it provides an efficient benchtop screening tool for the investigation of new encapsulation methods and/or synergistic immunomodulatory agents.