Gene therapy using Aβ variants for amyloid reduction

The Major Hypotheses of Alzheimer's Disease: Related Nanotechnology-Based Approaches for Its Diagnosis and Treatment

Alzheimer's disease (AD) is a well-known chronic neurodegenerative disorder that leads to the progressive death of brain cells, resulting in memory loss and the loss of other critical body functions. In March 2019, one of the major pharmaceutical companies and its partners announced that currently, there is no drug to cure AD, and all clinical trials of the new ones have been cancelled, leaving many people without hope. However, despite the clear message and startling reality, the research continued. Finally, in the last two years, the Food and Drug Administration (FDA) approved the first-ever medications to treat Alzheimer's, aducanumab and lecanemab. Despite researchers' support of this decision, there are serious concerns about their effectiveness and safety. The validation of aducanumab by the Centers for Medicare and Medicaid Services is still pending, and lecanemab was authorized without considering data from the phase III trials. Furthermore, numerous reports suggest that patients have died when undergoing extended treatment. While there is evidence that aducanumab and lecanemab may provide some relief to those suffering from AD, their impact remains a topic of ongoing research and debate within the medical community. The fact is that even though there are considerable efforts regarding pharmacological treatment, no definitive cure for AD has been found yet. Nevertheless, it is strongly believed that modern nanotechnology holds promising solutions and effective clinical strategies for the development of diagnostic tools and treatments for AD. This review summarizes the major hallmarks of AD, its etiological mechanisms, and challenges. It explores existing diagnostic and therapeutic methods and the potential of nanotechnology-based approaches for recognizing and monitoring patients at risk of irreversible neuronal degeneration. Overall, it provides a broad overview for those interested in the evolving areas of clinical neuroscience, AD, and related nanotechnology. With further research and development, nanotechnology-based approaches may offer new solutions and hope for millions of people affected by this devastating disease.

The TMEM106B T186S coding variant increases neurite arborization and synaptic density in primary hippocampal neurons

The lysosomal protein TMEM106B was identified as a risk modifier of multiple dementias including frontotemporal dementia and Alzheimer's disease. The gene comes in two major haplotypes, one associated with disease risk, and by comparison, the other with resilience. Only one coding polymorphism distinguishes the two alleles, a threonine-to-serine substitution at residue 185 (186 in mouse), that is inherited in disequilibrium with multiple non-coding variants. Transcriptional studies suggest synaptic, neuronal, and cognitive preservation in human subjects with the protective haplotype, while murine in vitro studies reveal dramatic effects of TMEM106B deletion on neuronal development. Despite this foundation, the field has not yet resolved whether coding variant is biologically meaningful, and if so, whether it has any specific effect on neuronal phenotypes. Here we studied how loss of TMEM106B or expression of the lone coding variant in isolation affected transcriptional signatures in the mature brain and neuronal structure during development in primary neurons. Homozygous expression of the TMEM106B T186S variant in knock-in mice increased cortical expression of genes associated with excitatory synaptic function and axon outgrowth, and promoted neurite branching, dendritic spine density, and synaptic density in primary hippocampal neurons. In contrast, constitutive TMEM106B deletion affected transcriptional signatures of myelination without altering neuronal development in vitro. Our findings show that the T186S variant is functionally relevant and may contribute to disease resilience during neurodevelopment.

Activity disruption causes degeneration of entorhinal neurons in a mouse model of Alzheimer's circuit dysfunction

Neurodegenerative diseases are characterized by selective vulnerability of distinct cell populations; however, the cause for this specificity remains elusive. Here, we show that entorhinal cortex layer 2 (EC2) neurons are unusually vulnerable to prolonged neuronal inactivity compared with neighboring regions of the temporal lobe, and that reelin + stellate cells connecting EC with the hippocampus are preferentially susceptible within the EC2 population. We demonstrate that neuronal death after silencing can be elicited through multiple independent means of activity inhibition, and that preventing synaptic release, either alone or in combination with electrical shunting, is sufficient to elicit silencing-induced degeneration. Finally, we discovered that degeneration following synaptic silencing is governed by competition between active and inactive cells, which is a circuit refinement process traditionally thought to end early in postnatal life. Our data suggests that the developmental window for wholesale circuit plasticity may extend into adulthood for specific brain regions. We speculate that this sustained potential for remodeling by entorhinal neurons may support lifelong memory but renders them vulnerable to prolonged activity changes in disease.

Stereotaxic-assisted gene therapy in Alzheimer's and Parkinson's diseases: therapeutic potentials and clinical frontiers

INTRODUCTION

Alzheimer's disease (AD) and Parkinson's disease (PD) are neurodegenerative disorders causing cognitive deficits and motor difficulties in the elderly. Conventional treatments are mainly symptomatic with little ability to halt disease progression. Gene therapies to correct or silence genetic mutations predisposing to AD or PD are currently being developed in preclinical studies and clinical trials, relying mostly on systemic delivery, which reduces their effectiveness. Imaging-guided stereotaxic procedures are used to locally deliver therapeutic cargos to well-defined brain sites, hence raising the question whether stereotaxic-assisted gene therapy has therapeutic potentials.

AREAS COVERED

The authors summarize the studies that investigated the use of gene therapy in PD and AD in animal and clinical studies over the past five years, with a special emphasis on the combinatorial potential with stereotaxic delivery. The advantages, limitations and futuristic challenges of this technique are discussed.

EXPERT OPINION

Robotic stereotaxis combined with intraoperative imaging has revolutionized brain surgeries. While gene therapies are bringing huge innovations to the medical field and new hope to AD and PD patients and medical professionals, the efficient and targeted delivery of such therapies is a bottleneck. We propose that careful application of stereotaxic delivery of gene therapies can improve PD and AD management. [Figure: see text].

Gene Therapy Strategy for Alzheimer's and Parkinson's Diseases Aimed at Preventing the Formation of Neurotoxic Oligomers in SH-SY5Y Cells

We present here a gene therapy approach aimed at preventing the formation of Ca2+-permeable amyloid pore oligomers that are considered as the most neurotoxic structures in both Alzheimer's and Parkinson's diseases. Our study is based on the design of a small peptide inhibitor (AmyP53) that combines the ganglioside recognition properties of the β-amyloid peptide (Aβ, Alzheimer) and α-synuclein (α-syn, Parkinson). As gangliosides mediate the initial binding step of these amyloid proteins to lipid rafts of the brain cell membranes, AmyP53 blocks, at the earliest step, the Ca2+ cascade that leads to neurodegeneration. Using a lentivirus vector, we genetically modified brain cells to express the therapeutic coding sequence of AmyP53 in a secreted form, rendering these cells totally resistant to oligomer formation by either Aβ or α-syn. This protection was specific, as control mCherry-transfected cells remained fully sensitive to these oligomers. AmyP53 was secreted at therapeutic concentrations in the supernatant of cultured cells, so that the therapy was effective for both transfected cells and their neighbors. This study is the first to demonstrate that a unique gene therapy approach aimed at preventing the formation of neurotoxic oligomers by targeting brain gangliosides may be considered for the treatment of two major neurodegenerative disorders, Alzheimer's and Parkinson's diseases.

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.