Gene therapy for neurodegenerative diseases

Stem cell therapeutics and gene therapy for neurologic disorders

Rapid advances in biological knowledge and technological innovation have greatly advanced the fields of stem cell and gene therapies to combat a broad spectrum of neurologic disorders. Researchers are currently exploring a variety of stem cell types (e.g., embryonic, progenitor, induced pluripotent) and various transplantation strategies, each with its own advantages and drawbacks. Similarly, various gene modification techniques (zinc finger, TALENs, CRISPR-Cas9) are employed with various delivery vectors to modify underlying genetic contributors to neurologic disorders. While these two individual fields continue to blaze new trails, it is the combination of these technologies which enables genetically engineered stem cells and vastly increases investigational and therapeutic opportunities. The capability to culture and expand stem cells outside the body, along with their potential to correct genetic abnormalities in patient-derived cells or enhance cells with extra gene products, unleashes the full biological potential for innovative, multifaceted approaches to treat complex neurological disorders. In this review, we provide an overview of stem cell and gene therapies in the context of neurologic disorders, highlighting recent advances and current shortcomings, and discuss prospects for future therapies in clinical settings.

A review of the advances, insights, and prospects of gene therapy for Alzheimer's disease: A novel target for therapeutic medicine

Neurodegenerative diseases such as Alzheimer's disease (AD) are still an important issue for scientists because it is difficult to cure with the available molecular medications and conventional treatments. Due to the complex nature of the brain structures and heterogeneous morphological and physiological properties of neuronal cells, interventions for cerebral-related disorders using surgical approaches, and classical and ongoing treatments remain hard for physicians. Furthermore, the development of newly designed medications attempts to target AD are not successful in improving AD, because abnormalities of tau protein, aggregation of amyloid β (Aβ) peptide, inflammatory responses, etc lead to advanced neurodegeneration processes that conventional treatments cannot stop them. In recent years, novel diagnostic strategies and therapeutic approaches have been developed to identify and cure early pathological events of AD. Accordingly, many gene-based therapies have been developed and introduce the therapeutic potential to prevent and cure AD. On the other hand, genetic investigations and postmortem assessments have detected a large number of factors associated with AD pathology. Also, genetically diverse animal models of AD help us to detect and prioritize novel resilience mechanisms. Hence, gene therapy can be considered an effective and powerful tool to identify and treat human diseases. Ultimately, gene study and gene-based therapy with a critical role in the detection and cure of various human disorders will have a fundamental role in our lives forever. This scientific review paper discusses the present status of different therapeutic strategies, particularly gene-based therapy in treating AD, along with its challenges.

Novel Gene Therapy Approaches for Targeting Neurodegenerative Disorders: Focusing on Delivering Neurotrophic Genes

Neurodegenerative illnesses (NDDs) like Alzheimer's, Parkinson's, amyotrophic lateral sclerosis, spinal muscular atrophy, and Huntington's disease have demonstrated considerable potential for gene therapy as a viable therapeutic intervention. NDDs are marked by the decline of neurons, resulting in changes in both behavior and pathology within the body. Strikingly, only symptomatic management is available without a cure for the NDDs. There is an unmet need for a permanent therapeutic approach. Many studies have been going on to target the newer therapeutic molecular targets for NDDs including gene-based therapy. Gene therapy has the potential to provide therapeutic benefits to a large number of patients with NDDs by offering mechanisms including neuroprotection, neuro-restoration, and rectification of pathogenic pathways. Gene therapy is a medical approach that aims to modify the biological characteristics of living cells by controlling the expression of specific genes in certain neurological disorders. Despite being the most complex and well-protected organ in the human body, there is clinical evidence to show that it is possible to specifically target the central nervous system (CNS). This provides hope for the prospective application of gene therapy in treating NDDs in the future. There are several advanced techniques available for using viral or non-viral vectors to deliver the therapeutic gene to the afflicted region. Neurotrophic factors (NTF) in the brain are crucial for the development, differentiation, and survival of neurons in the CNS, making them important in the context of various neurological illnesses. Gene delivery of NTF has the potential to be used as a therapeutic approach for the treatment of neurological problems in the brain. This review primarily focuses on the methodologies employed for delivering the genes of different NTFs to treat neurological disorders. These techniques are currently being explored as a viable therapeutic approach for neurodegenerative diseases. The article exclusively addresses gene delivery approaches and does not cover additional therapy strategies for NDDs. Gene therapy offers a promising alternative treatment for NDDs by stimulating neuronal growth instead of solely relying on symptom relief from drugs and their associated adverse effects. It can serve as a long-lasting and advantageous treatment choice for the management of NDDs. The likelihood of developing NDDs increases with age as a result of neuronal degradation in the brain. Gene therapy is an optimal approach for promoting neuronal growth through the introduction of nerve growth factor genes.

Allopregnanolone and its antagonist modulate neuroinflammation and neurological impairment

Neuroinflammation accompanies several brain disorders, either as a secondary consequence or as a primary cause and may contribute importantly to disease pathogenesis. Neurosteroids which act as Positive Steroid Allosteric GABA-A receptor Modulators (Steroid-PAM) appear to modulate neuroinflammation and their levels in the brain may vary because of increased or decreased local production or import from the systemic circulation. The increased synthesis of steroid-PAMs is possibly due to increased expression of the mitochondrial cholesterol transporting protein (TSPO) in neuroinflammatory tissue, and reduced production may be due to changes in the enzymatic activity. Microglia and astrocytes play an important role in neuroinflammation, and their production of inflammatory mediators can be both activated and inhibited by steroid-PAMs and GABA. What is surprising is the finding that both allopregnanolone, a steroid-PAM, and golexanolone, a novel GABA-A receptor modulating steroid antagonist (GAMSA), can inhibit microglia and astrocyte activation and normalize their function. This review focuses on the role of steroid-PAMs in neuroinflammation and their importance in new therapeutic approaches to CNS and liver disease.

Glucocorticoid receptor-dependent therapeutic efficacy of tauroursodeoxycholic acid in preclinical models of spinocerebellar ataxia type 3

Spinocerebellar ataxia type 3 (SCA3) is an adult-onset neurodegenerative disease caused by a polyglutamine expansion in the ataxin-3 (ATXN3) gene. No effective treatment is available for this disorder, other than symptom-directed approaches. Bile acids have shown therapeutic efficacy in neurodegenerative disease models. Here, we pinpointed tauroursodeoxycholic acid (TUDCA) as an efficient therapeutic, improving the motor and neuropathological phenotype of SCA3 nematode and mouse models. Surprisingly, transcriptomic and functional in vivo data showed that TUDCA acts in neuronal tissue through the glucocorticoid receptor (GR), but independently of its canonical receptor, the farnesoid X receptor (FXR). TUDCA was predicted to bind to the GR, in a similar fashion to corticosteroid molecules. GR levels were decreased in disease-affected brain regions, likely due to increased protein degradation as a consequence of ATXN3 dysfunction being restored by TUDCA treatment. Analysis of a SCA3 clinical cohort showed intriguing correlations between the peripheral expression of GR and the predicted age at disease onset in presymptomatic subjects and FKBP5 expression with disease progression, suggesting this pathway as a potential source of biomarkers for future study. We have established a novel in vivo mechanism for the neuroprotective effects of TUDCA in SCA3 and propose this readily available drug for clinical trials in SCA3 patients.

Unraveling the Genetic Landscape of Neurological Disorders: Insights into Pathogenesis, Techniques for Variant Identification, and Therapeutic Approaches

Genetic abnormalities play a crucial role in the development of neurodegenerative disorders (NDDs). Genetic exploration has indeed contributed to unraveling the molecular complexities responsible for the etiology and progression of various NDDs. The intricate nature of rare and common variants in NDDs contributes to a limited understanding of the genetic risk factors associated with them. Advancements in next-generation sequencing have made whole-genome sequencing and whole-exome sequencing possible, allowing the identification of rare variants with substantial effects, and improving the understanding of both Mendelian and complex neurological conditions. The resurgence of gene therapy holds the promise of targeting the etiology of diseases and ensuring a sustained correction. This approach is particularly enticing for neurodegenerative diseases, where traditional pharmacological methods have fallen short. In the context of our exploration of the genetic epidemiology of the three most prevalent NDDs-amyotrophic lateral sclerosis, Alzheimer's disease, and Parkinson's disease, our primary goal is to underscore the progress made in the development of next-generation sequencing. This progress aims to enhance our understanding of the disease mechanisms and explore gene-based therapies for NDDs. Throughout this review, we focus on genetic variations, methodologies for their identification, the associated pathophysiology, and the promising potential of gene therapy. Ultimately, our objective is to provide a comprehensive and forward-looking perspective on the emerging research arena of NDDs.

Nano biomaterials based strategies for enhanced brain targeting in the treatment of neurodegenerative diseases: an up-to-date perspective

Neurons and their connecting axons gradually degenerate in neurodegenerative diseases (NDs), leading to dysfunctionality of the neuronal cells and eventually their death. Drug delivery for the treatment of effected nervous system is notoriously complicated because of the presence of natural barriers, i.e., the blood-brain barrier and the blood cerebrospinal fluid barrier. Palliative care is currently the standard care for many diseases. Therefore, treatment programs that target the disease's origin rather than its symptoms are recommended. Nanotechnology-based drug delivery platforms offer an innovative way to circumvent these obstacles and deliver medications directly to the central nervous system, thereby enabling treatment of several common neurological problems, i.e., Alzheimer's, Parkinson's, Huntington's, and amyotrophic lateral sclerosis. Interestingly, the combination of nanomedicine and gene therapy enables targeting of selective mutant genes responsible for the progression of NDs, which may provide a much-needed boost in the struggle against these diseases. Herein, we discussed various central nervous system delivery obstacles, followed by a detailed insight into the recently developed techniques to restore neurological function via the differentiation of neural stem cells. Moreover, a comprehensive background on the role of nanomedicine in controlling neurogenesis via differentiation of neural stem cells is explained. Additionally, numerous phytoconstituents with their neuroprotective properties and molecular targets in the identification and management of NDs are also deliberated. Furthermore, a detailed insight of the ongoing clinical trials and currently marketed products for the treatment of NDs is provided in this manuscript.

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.

Therapeutic potential of gene therapy for gastrointestinal diseases: Advancements and future perspectives

Advancements in understanding the pathogenesis mechanisms underlying gastrointestinal diseases, encompassing inflammatory bowel disease, gastrointestinal cancer, and gastroesophageal reflux disease, have led to the identification of numerous novel therapeutic targets. These discoveries have opened up exciting possibilities for developing gene therapy strategies to treat gastrointestinal diseases. These strategies include gene replacement, gene enhancement, gene overexpression, gene function blocking, and transgenic somatic cell transplantation. In this review, we introduce the important gene therapy targets and targeted delivery systems within the field of gastroenterology. Furthermore, we provide a comprehensive overview of recent progress in gene therapy related to gastrointestinal disorders and shed light on the application of innovative gene-editing technologies in treating these conditions. These developments are fueling a revolution in the management of gastrointestinal diseases. Ultimately, we discuss the current challenges (particularly regarding safety, oral efficacy, and cost) and explore potential future directions for implementing gene therapy in the clinical settings for gastrointestinal diseases.

κ-Carrageenan Oligosaccharides Protect Nerves by Regulating Microglial Autophagy in Alzheimer's Disease

κ-Carrageenan is a linear sulfated polysaccharide extracted from the cell wall of marine red algae, and its enzymatically digested oligosaccharides (KOS) can inhibit microglial hyperactivation. Alzheimer's disease (AD) is a common chronic neurodegenerative disease, characterized by cognitive and memory impairment accompanied by nerve cell damage. Microglia activation causing enhancement of proinflammatory effects and neurotoxicity is one of the early events in AD disease. In this study, whether KOS have therapeutic or preventive effects in the AD model prepared from APP/PS1 transgenic mice was determined. Learning and memory of AD mice were detected by water maze experiments, and microglial activation-related protein expression and deposition of APP and Aβ1-42 in the brain were examined. The effects of KOS on expressed inflammatory factors and inflammation-related proteins by microglia were tested by cell experiments. Transwell coculture was used to investigate the effect of microglia on neural cell activity after KOS treatment. The results showed that KOS could relieve the clinical symptoms in AD mice, and a decrease in the expression of inflammatory factors and inflammation-related proteins in brain tissue was detected. KOS alleviated nerve cell apoptosis by inhibiting the overactivation of microglia, thus exhibiting neuroprotective effects. Exploring the protective effect of KOS inhibition of microglia inflammation is expected to provide a theoretical basis for KOS as a therapeutic drug for neurodegenerative diseases.

Regenerative medicine improve neurodegenerative diseases

Regenerative medicine is a subdivision of medicine that improves methods to regrow, repair or replace unhealthy cells and tissues to return to normal function. Cell therapy, gene therapy, nanomedicine as choices used to cure neurodegenerative disease. Recently, studies related to the treatment of neurodegenerative disorders have been focused on stem cell therapy and Nano-drugs beyond other than regenerative medicine. Hence, by data from experimental models and clinical trials, we review the impact of stem cell therapy, gene therapy, and nanomedicine on the treatment of Alzheimer's disease (AD), Parkinson's disease (PD), and Amyotrophic lateral sclerosis (ALS). Indeed, improved knowledge and continued research on gene therapy and nanomedicine in treating Alzheimer's disease, Parkinson's disease, and Amyotrophic lateral sclerosis lead to advancements in effective and practical treatments for neurodegenerative diseases.

Decoding Neurodegeneration: A Comprehensive Review of Molecular Mechanisms, Genetic Influences, and Therapeutic Innovations

Neurodegenerative disorders often acquire due to genetic predispositions and genomic alterations after exposure to multiple risk factors. The most commonly found pathologies are variations of dementia, such as frontotemporal dementia and Lewy body dementia, as well as rare subtypes of cerebral and cerebellar atrophy-based syndromes. In an emerging era of biomedical advances, molecular-cellular studies offer an essential avenue for a thorough recognition of the underlying mechanisms and their possible implications in the patient's symptomatology. This comprehensive review is focused on deciphering molecular mechanisms and the implications regarding those pathologies' clinical advancement and provides an analytical overview of genetic mutations in the case of neurodegenerative disorders. With the help of well-developed modern genetic investigations, these clinically complex disturbances are highly understood nowadays, being an important step in establishing molecularly targeted therapies and implementing those approaches in the physician's practice.

The Exosome-Mediated PI3K/Akt/mTOR Signaling Pathway in Neurological Diseases

As major public health concerns associated with a rapidly growing aging population, neurodegenerative diseases (NDDs) and neurological diseases are important causes of disability and mortality. Neurological diseases affect millions of people worldwide. Recent studies have indicated that apoptosis, inflammation, and oxidative stress are the main players of NDDs and have critical roles in neurodegenerative processes. During the aforementioned inflammatory/apoptotic/oxidative stress procedures, the phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) pathway plays a crucial role. Considering the functional and structural aspects of the blood-brain barrier, drug delivery to the central nervous system is relatively challenging. Exosomes are nanoscale membrane-bound carriers that can be secreted by cells and carry several cargoes, including proteins, nucleic acids, lipids, and metabolites. Exosomes significantly take part in the intercellular communications due to their specific features including low immunogenicity, flexibility, and great tissue/cell penetration capabilities. Due to their ability to cross the blood-brain barrier, these nano-sized structures have been introduced as proper vehicles for central nervous system drug delivery by multiple studies. In the present systematic review, we highlight the potential therapeutic effects of exosomes in the context of NDDs and neurological diseases by targeting the PI3K/Akt/mTOR signaling pathway.

Vision protection and robust axon regeneration in glaucoma models by membrane-associated Trk receptors

Activation of neurotrophic factor signaling is a promising therapy for neurodegeneration. However, the transient nature of ligand-dependent activation limits its effectiveness. In this study, we solved this problem by inventing a system that forces membrane localization of the intracellular domain of tropomyosin receptor kinase B (iTrkB), which results in constitutive activation without ligands. Our system overcomes the small size limitation of the genome packaging in adeno-associated virus (AAV) and allows high expression of the transgene. Using AAV-mediated gene therapy in the eyes, we demonstrate that iTrkB expression enhances neuroprotection in mouse models of glaucoma and stimulates robust axon regeneration after optic nerve injury. In addition, iTrkB expression in the retina was also effective in an optic tract transection model, in which the injury site is near the superior colliculus. Regenerating axons successfully formed pathways to their brain targets, resulting in partial recovery of visual behavior. Our system may also be applicable to other trophic factor signaling pathways and lead to a significant advance in the field of gene therapy for neurotrauma and neurodegenerative disorders, including glaucoma.

Progress of Microfluidic Hydrogel-Based Scaffolds and Organ-on-Chips for the Cartilage Tissue Engineering

Cartilage degeneration is among the fundamental reasons behind disability and pain across the globe. Numerous approaches have been employed to treat cartilage diseases. Nevertheless, none have shown acceptable outcomes in the long run. In this regard, the convergence of tissue engineering and microfabrication principles can allow developing more advanced microfluidic technologies, thus offering attractive alternatives to current treatments and traditional constructs used in tissue engineering applications. Herein, the current developments involving microfluidic hydrogel-based scaffolds, promising structures for cartilage regeneration, ranging from hydrogels with microfluidic channels to hydrogels prepared by the microfluidic devices, that enable therapeutic delivery of cells, drugs, and growth factors, as well as cartilage-related organ-on-chips are reviewed. Thereafter, cartilage anatomy and types of damages, and present treatment options are briefly overviewed. Various hydrogels are introduced, and the advantages of microfluidic hydrogel-based scaffolds over traditional hydrogels are thoroughly discussed. Furthermore, available technologies for fabricating microfluidic hydrogel-based scaffolds and microfluidic chips are presented. The preclinical and clinical applications of microfluidic hydrogel-based scaffolds in cartilage regeneration and the development of cartilage-related microfluidic chips over time are further explained. The current developments, recent key challenges, and attractive prospects that should be considered so as to develop microfluidic systems in cartilage repair are highlighted.

Gene Therapy in ALS and SMA: Advances, Challenges and Perspectives

Gene therapy is defined as the administration of genetic material to modify, manipulate gene expression or alter the properties of living cells for therapeutic purposes. Recent advances and improvements in this field have led to many breakthroughs in the treatment of various diseases. As a result, there has been an increasing interest in the use of these therapies to treat motor neuron diseases (MNDs), for which many potential molecular targets have been discovered. MNDs are neurodegenerative disorders that, in their most severe forms, can lead to respiratory failure and death, for instance, spinal muscular atrophy (SMA) or amyotrophic lateral sclerosis (ALS). Despite the fact that SMA has been known for many years, it is still one of the most common genetic diseases causing infant mortality. The introduction of drugs based on ASOs-nusinersen; small molecules-risdiplam; and replacement therapy (GRT)-Zolgensma has shown a significant improvement in both event-free survival and the quality of life of patients after using these therapies in the available trial results. Although there is still no drug that would effectively alleviate the course of the disease in ALS, the experience gained from SMA gene therapy gives hope for a positive outcome of the efforts to produce an effective and safe drug. The aim of this review is to present current progress and prospects for the use of gene therapy in the treatment of both SMA and ALS.

Brain and spinal cord trauma: what we know about the therapeutic potential of insulin growth factor 1 gene therapy

Although little attention has been paid to cognitive and emotional dysfunctions observed in patients after spinal cord injury, several reports have described impairments in cognitive abilities. Our group also has contributed significantly to the study of cognitive impairments in a rat model of spinal cord injury. These findings are very significant because they demonstrate that cognitive and mood deficits are not induced by lifestyle changes, drugs of abuse, and combined medication. They are related to changes in brain structures involved in cognition and emotion, such as the hippocampus. Chronic spinal cord injury decreases neurogenesis, enhances glial reactivity leading to hippocampal neuroinflammation, and triggers cognitive deficits. These brain distal abnormalities are recently called tertiary damage. Given that there is no treatment for Tertiary Damage, insulin growth factor 1 gene therapy emerges as a good candidate. Insulin growth factor 1 gene therapy recovers neurogenesis and induces the polarization from pro-inflammatory towards anti-inflammatory microglial phenotypes, which represents a potential strategy to treat the neuroinflammation that supports tertiary damage. Insulin growth factor 1 gene therapy can be extended to other central nervous system pathologies such as traumatic brain injury where the neuroinflammatory component is crucial. Insulin growth factor 1 gene therapy could emerge as a new therapeutic strategy for treating traumatic brain injury and spinal cord injury.

The Role of Striatal Cav1.3 Calcium Channels in Therapeutics for Parkinson's Disease

Parkinson's disease (PD) is a relentlessly progressive neurodegenerative disorder with typical motor symptoms that include rigidity, tremor, and akinesia/bradykinesia, in addition to a host of non-motor symptoms. Motor symptoms are caused by progressive and selective degeneration of dopamine (DA) neurons in the SN pars compacta (SNpc) and the accompanying loss of striatal DA innervation from these neurons. With the exception of monogenic forms of PD, the etiology of idiopathic PD remains unknown. While there are a number of symptomatic treatment options available to individuals with PD, these therapies do not work uniformly well in all patients, and eventually most are plagued with waning efficacy and significant side-effect liability with disease progression. The incidence of PD increases with aging, and as such the expected burden of this disease will continue to escalate as our aging population increases (Dorsey et al. Neurology 68:384-386, 2007). The daunting personal and socioeconomic burden has pressed scientists and clinicians to find improved symptomatic treatment options devoid side-effect liability and meaningful disease-modifying therapies. Federal and private sources have supported clinical investigations over the past two-plus decades; however, no trial has yet been successful in finding an effective therapy to slow progression of PD, and there is currently just one FDA approved drug to treat the antiparkinsonian side-effect known as levodopa-induced dyskinesia (LID) that impacts approximately 90% of all individuals with PD. In this review, we present biological rationale and experimental evidence on the potential therapeutic role of the L-type voltage-gated Cav1.3 calcium (Ca2+) channels in two distinct brain regions, with two distinct mechanisms of action, in impacting the lives of individuals with PD. Our primary emphasis will be on the role of Cav1.3 channels in the striatum and the compelling evidence of their involvement in LID side-effect liability. We also briefly discuss the role of these same Ca2+ channels in the SNpc and the longstanding interest in Cav1.3 in this brain region in halting or delaying progression of PD.

Neurodegenerative Diseases: From Dysproteostasis, Altered Calcium Signalosome to Selective Neuronal Vulnerability to AAV-Mediated Gene Therapy

Despite intense research into the multifaceted etiology of neurodegenerative diseases (ND), they remain incurable. Here we provide a brief overview of several major ND and explore novel therapeutic approaches. Although the cause (s) of ND are not fully understood, the accumulation of misfolded/aggregated proteins in the brain is a common pathological feature. This aggregation may initiate disruption of Ca⁺⁺ signaling, which is an early pathological event leading to altered dendritic structure, neuronal dysfunction, and cell death. Presently, ND gene therapies remain unidimensional, elusive, and limited to modifying one pathological feature while ignoring others. Considering the complexity of signaling cascades in ND, we discuss emerging therapeutic concepts and suggest that deciphering the molecular mechanisms involved in dendritic pathology may broaden the phenotypic spectrum of ND treatment. An innovative multiplexed gene transfer strategy that employs silencing and/or over-expressing multiple effectors could preserve vulnerable neurons before they are lost. Such therapeutic approaches may extend brain health span and ameliorate burdensome chronic disease states.

Emerging Roles of Microfluidics in Brain Research: From Cerebral Fluids Manipulation to Brain-on-a-Chip and Neuroelectronic Devices Engineering

Remarkable progress made in the past few decades in brain research enables the manipulation of neuronal activity in single neurons and neural circuits and thus allows the decipherment of relations between nervous systems and behavior. The discovery of glymphatic and lymphatic systems in the brain and the recently unveiled tight relations between the gastrointestinal (GI) tract and the central nervous system (CNS) further revolutionize our understanding of brain structures and functions. Fundamental questions about how neurons conduct two-way communications with the gut to establish the gut-brain axis (GBA) and interact with essential brain components such as glial cells and blood vessels to regulate cerebral blood flow (CBF) and cerebrospinal fluid (CSF) in health and disease, however, remain. Microfluidics with unparalleled advantages in the control of fluids at microscale has emerged recently as an effective approach to address these critical questions in brain research. The dynamics of cerebral fluids (i.e., blood and CSF) and novel in vitro brain-on-a-chip models and microfluidic-integrated multifunctional neuroelectronic devices, for example, have been investigated. This review starts with a critical discussion of the current understanding of several key topics in brain research such as neurovascular coupling (NVC), glymphatic pathway, and GBA and then interrogates a wide range of microfluidic-based approaches that have been developed or can be improved to advance our fundamental understanding of brain functions. Last, emerging technologies for structuring microfluidic devices and their implications and future directions in brain research are discussed.

Self-Catalytic Small Interfering RNA Nanocarriers for Synergistic Treatment of Neurodegenerative Diseases

Gene therapy has shown great potential for neurodegenerative diseases with complex pathology. However, its therapeutic effect is limited due to the delivery barriers and its own single function. Herein, self-catalytic small interfering RNA (siRNA) nanocarriers (S/Ce-PABMS) are developed to catalyze delivery process and treatment process for synergistic treatment of neurodegenerative diseases. On the one hand, the rough surface of the S/Ce-PABMS mediated by ceria (CeO₂ ) nanozymes can catalyze cellular uptake in the delivery process, so that S/Ce-PABMS with acetylcholine analogs penetrate the blood-brain barrier and enter neurons more effectively. On the other hand, the CeO₂ nanozymes can catalyze the treatment process by scavenging excess reactive oxygen species, and cooperate with siRNA-targeting SNCA to decrease the α-synuclein (α-syn) aggregation and alleviate the Parkinsonian pathology. Moreover, the S/Ce-PABMS treatment reduces the number of activated microglia and regulates the release of inflammatory cytokine, thereby relieving neuroinflammation. After treatment with S/Ce-PABMS, dyskinesia in Parkinson's disease model mice is significantly alleviated. The finding shows that the self-catalytic nanocarriers, S/Ce-PABMS, have great potential in the treatment of neurodegenerative diseases.

Whole and fractionated human platelet lysate biomaterials-based biotherapy induces strong neuroprotection in experimental models of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease of motor neurons leading to death within 3 years and without a curative treatment. Neurotrophic growth factors (NTFs) are pivotal for cell survival. A reason for the lack of patient efficacy with single recombinant NTF brain infusion is likely to be due to the synergistic neuroprotective action of multiple NTFs on a diverse set of signaling pathways. Fractionated (protein size <50, <30, <10, <3 kDa) heat-treated human platelet lysate (HHPL) preparations were adapted for use in brain tissue with the aim of demonstrating therapeutic value in ALS models and further elucidation of the mechanisms of action. In neuronal culture all fractions induced Akt-dependent neuroprotection as well as a strong anti-apoptotic and anti-ferroptotic action. In the <3 kDa fraction anti-ferroptotic properties were shown to be GPX4 dependent highlighting a role for other platelet elements associated with NTFs. In the SOD1^G86R mouse model, lifespan was strongly increased by intracerebroventricular delivery of HHPL or by intranasal administration of <3 kDa fraction. Our results suggest that the platelet lysate biomaterials are neuroprotective in ALS. Further studies would now validate theragnostic biomarker on its antiferroptotic action, for further clinical development.

Gene Therapy Approach with an Emphasis on Growth Factors: Theoretical and Clinical Outcomes in Neurodegenerative Diseases

The etiology of many neurological diseases affecting the central nervous system (CNS) is unknown and still needs more effective and specific therapeutic approaches. Gene therapy has a promising future in treating neurodegenerative disorders by correcting the genetic defects or by therapeutic protein delivery and is now an attraction for neurologists to treat brain disorders, like Alzheimer’s disease, Parkinson’s disease, amyotrophic lateral sclerosis, spinal muscular atrophy, spinocerebellar ataxia, epilepsy, Huntington’s disease, stroke, and spinal cord injury. Gene therapy allows the transgene induction, with a unique expression in cells’ substrate. This article mainly focuses on the delivering modes of genetic materials in the CNS, which includes viral and non-viral vectors and their application in gene therapy. Despite the many clinical trials conducted so far, data have shown disappointing outcomes. The efforts done to improve outcomes, efficacy, and safety in the identification of targets in various neurological disorders are also discussed here. Adapting gene therapy as a new therapeutic approach for treating neurological disorders seems to be promising, with early detection and delivery of therapy before the neuron is lost, helping a lot the development of new therapeutic options to translate to the clinic.

Gene Therapy for Polyglutamine Spinocerebellar Ataxias: Advances, Challenges, and Perspectives

Polyglutamine spinocerebellar ataxias (SCAs) comprise a heterogeneous group of six autosomal dominant ataxias caused by cytosine-adenine-guanine repeat expansions in the coding region of single genes. Currently, there is no curative or disease-slowing treatment for these disorders, but their monogenic inheritance has informed rationales for development of gene therapy strategies. In fact, RNA interference strategies have shown promising findings in cellular and/or animal models of SCA1, SCA3, SCA6, and SCA7. In addition, antisense oligonucleotide therapy has provided encouraging proofs of concept in models of SCA1, SCA2, SCA3, and SCA7, but they have not yet progressed to clinical trials. On the contrary, the gene editing strategies, such as the clustered regularly interspaced short palindromic repeat (CRISPR/Cas9), have been introduced to a limited extent in these disorders. In this article, we review the available literature about gene therapy in polyglutamine SCAs and discuss the main technological and ethical challenges toward the prospect of their use in future clinical trials. Although antisense oligonucleotide therapies are further along the path to clinical phases, the recent failure of three clinical trials in Huntington's disease may delay their utilization for polyglutamine SCAs, but they offer lessons that could optimize the likelihood of success in potential future clinical studies. © 2021 International Parkinson and Movement Disorder Society.

Understanding the Potential of Genome Editing in Parkinson's Disease

CRISPR is a simple and cost-efficient gene-editing technique that has become increasingly popular over the last decades. Various CRISPR/Cas-based applications have been developed to introduce changes in the genome and alter gene expression in diverse systems and tissues. These novel gene-editing techniques are particularly promising for investigating and treating neurodegenerative diseases, including Parkinson's disease, for which we currently lack efficient disease-modifying treatment options. Gene therapy could thus provide treatment alternatives, revolutionizing our ability to treat this disease. Here, we review our current knowledge on the genetic basis of Parkinson's disease to highlight the main biological pathways that become disrupted in Parkinson's disease and their potential as gene therapy targets. Next, we perform a comprehensive review of novel delivery vehicles available for gene-editing applications, critical for their successful application in both innovative research and potential therapies. Finally, we review the latest developments in CRISPR-based applications and gene therapies to understand and treat Parkinson's disease. We carefully examine their advantages and shortcomings for diverse gene-editing applications in the brain, highlighting promising avenues for future research.

Emerging pathogenic role of peripheral blood factors following BBB disruption in neurodegenerative disease

The responses of central nervous system (CNS) cells such as neurons and glia in neurodegenerative diseases (NDs) suggest that regulation of neuronal and glial functions could be a strategy for ND prevention and/or treatment. However, attempts to develop such therapeutics for NDs have been hindered by the challenge of blood-brain barrier (BBB) permeability and continued constitutive neuronal loss. These limitations indicate the need for additional perspectives for the prevention/treatment of NDs. In particular, the disruption of the blood-brain barrier (BBB) that accompanies NDs allows brain infiltration by peripheral factors, which may stimulate innate immune responses involved in the progression of neurodegeneration. The accumulation of blood factors like thrombin, fibrinogen, c-reactive protein (CRP) and complement components in the brain has been observed in NDs and may activate the innate immune system in the CNS. Thus, strengthening the integrity of the BBB may enhance its protective role to attenuate ND progression and functional loss. In this review, we describe the innate immune system in the CNS and the contribution of blood factors to the role of the CNS immune system in neurodegeneration and neuroprotection.

Recent Progress of Machine Learning in Gene Therapy

With new developments in biomedical technology, it is now a viable therapeutic treatment to alter genes with techniques like CRISPR. At the same time, it is increasingly cheaper to do whole genome sequencing, resulting in rapid advancement in gene therapy and editing in precision medicine. Thus, understanding the current industry and academic applications of gene therapy provides an important backdrop to future scientific developments. Additionally, machine learning and artificial intelligence techniques allow for the reduction of time and money spent in the development of new gene therapy products and techniques. In this paper, we survey the current progress of gene therapy treatments for several diseases and explore machine learning applications in gene therapy. We also discuss the ethical implications of gene therapy and the use of machine learning in precision medicine. Machine learning and gene therapy are both topics gaining popularity in various publications, and we conclude that there is still room for continued research and application of machine learning techniques in the gene therapy field.

Chemogenetics drives paradigm change in the investigation of behavioral circuits and neural mechanisms underlying drug action

Recent developments in chemogenetic approaches to the investigation of brain function have ushered in a paradigm change in the strategy for drug and behavior research and clinical drug-based medications. As the nature of the drug action is based on humoral regulation, it is a challenge to identify the neuronal mechanisms responsible for the expression of certain targeted behavior induced by drug application. The development of chemogenetic approaches has allowed researchers to control neural activities in targeted neurons through a toolbox, including engineered G protein-coupled receptors or ligand-gated ion channels together with exogenously inert synthetic ligands. This review provides a brief overview of the chemogenetics toolbox with an emphasis on the DREADDs (Designer Receptors Exclusively Activated by Designer Drugs) technique used in rodent models, which is applicable to the investigation of how specific neural circuits regulate behavioral processes. The use of chemogenetics has had a significant impact on basic neuroscience for a better understanding of the relationships between brain activity and the expression of behaviors with cell- and circuit-specific orders. Furthermore, chemogenetics is potentially a useful tool to deconstruct the neuropathological mechanisms of mental diseases and its regulation by drug, and provide us with transformative therapeutics with medication. We also review recent findings in the use of chemogenetic techniques to uncover functional circuit connections of serotonergic neurons in rodent models.

Restoration of Noradrenergic Function in Parkinson's Disease Model Mice

Dysfunction of the central noradrenergic and dopaminergic systems is the primary neurobiological characteristic of Parkinson’s disease (PD). Importantly, neuronal loss in the locus coeruleus (LC) that occurs in early stages of PD may accelerate progressive loss of dopaminergic neurons. Therefore, restoring the activity and function of the deficient noradrenergic system may be an important therapeutic strategy for early PD. In the present study, the lentiviral constructions of transcription factors Phox2a/2b, Hand2 and Gata3, either alone or in combination, were microinjected into the LC region of the PD model VMAT2 Lo mice at 12 and 18 month age. Biochemical analysis showed that microinjection of lentiviral expression cassettes into the LC significantly increased mRNA levels of Phox2a, and Phox2b, which were accompanied by parallel increases of mRNA and proteins of dopamine β-hydroxylase (DBH) and tyrosine hydroxylase (TH) in the LC. Furthermore, there was considerable enhancement of DBH protein levels in the frontal cortex and hippocampus, as well as enhanced TH protein levels in the striatum and substantia nigra. Moreover, these manipulations profoundly increased norepinephrine and dopamine concentrations in the striatum, which was followed by a remarkable improvement of the spatial memory and locomotor behavior. These results reveal that over-expression of these transcription factors in the LC improves noradrenergic and dopaminergic activities and functions in this rodent model of PD. It provides the necessary groundwork for the development of gene therapies of PD, and expands our understanding of the link between the LC-norepinephrine and dopamine systems during the progression of PD.

Skeletal Muscle in ALS: An Unappreciated Therapeutic Opportunity?

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder characterized by the selective degeneration of upper and lower motor neurons and by the progressive weakness and paralysis of voluntary muscles. Despite intense research efforts and numerous clinical trials, it is still an incurable disease. ALS had long been considered a pure motor neuron disease; however, recent studies have shown that motor neuron protection is not sufficient to prevent the course of the disease since the dismantlement of neuromuscular junctions occurs before motor neuron degeneration. Skeletal muscle alterations have been described in the early stages of the disease, and they seem to be mainly involved in the "dying back" phenomenon of motor neurons and metabolic dysfunctions. In recent years, skeletal muscles have been considered crucial not only for the etiology of ALS but also for its treatment. Here, we review clinical and preclinical studies that targeted skeletal muscles and discuss the different approaches, including pharmacological interventions, supplements or diets, genetic modifications, and training programs.

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.

Exploring the Role of Gene Therapy for Neurological Disorders

Gene therapy is one of the frontier fields of medical breakthroughs that poses as an effective solution to previously incurable diseases. The delivery of the corrective genetic material or a therapeutic gene into the cell restores the missing gene function and cures a plethora of diseases, incurable by the conventional medical approaches. This discovery holds the potential to treat many neurodegenerative disorders such as muscular atrophy, multiple sclerosis, Parkinson's disease (PD) and Alzheimer's disease (AD), among others. Gene therapy proves as a humane, cost-effective alternative to the exhaustive often arduous and timely impossible process of finding matched donors and extensive surgery. It also overcomes the shortcoming of conventional methods to cross the blood-brain barrier. However, the use of gene therapy is only possible after procuring the in-depth knowledge of the immuno-pathogenesis and molecular mechanism of the disease. The process of gene therapy can be broadly categorized into three main steps: elucidating the target gene, culling the appropriate vector, and determining the best mode of transfer; each step mandating pervasive research. This review aims to dissertate and summarize the role, various vectors and methods of delivery employed in gene therapy with special emphasis on therapy directed at the central nervous system (CNS) associated with neurodegenerative diseases.

Targeting Mitochondrial Impairment in Parkinson's Disease: Challenges and Opportunities

The underlying pathophysiology of Parkinson's disease is complex, but mitochondrial dysfunction has an established and prominent role. This is supported by an already large and rapidly growing body of evidence showing that the role of mitochondrial (dys)function is central and multifaceted. However, there are clear gaps in knowledge, including the dilemma of explaining why inherited mitochondriopathies do not usually present with parkinsonian symptoms. Many aspects of mitochondrial function are potential therapeutic targets, including reactive oxygen species production, mitophagy, mitochondrial biogenesis, mitochondrial dynamics and trafficking, mitochondrial metal ion homeostasis, sirtuins, and endoplasmic reticulum links with mitochondria. Potential therapeutic strategies may also incorporate exercise, microRNAs, mitochondrial transplantation, stem cell therapies, and photobiomodulation. Despite multiple studies adopting numerous treatment strategies, clinical trials to date have generally failed to show benefit. To overcome this hurdle, more accurate biomarkers of mitochondrial dysfunction are required to detect subtle beneficial effects. Furthermore, selecting study participants early in the disease course, studying them for suitable durations, and stratifying them according to genetic and neuroimaging findings may increase the likelihood of successful clinical trials. Moreover, treatments involving combined approaches will likely better address the complexity of mitochondrial dysfunction in Parkinson's disease. Therefore, selecting the right patients, at the right time, and using targeted combination treatments, may offer the best chance for development of an effective novel therapy targeting mitochondrial dysfunction in Parkinson's disease.

HHIP Overexpression Suppresses Human Gastric Cancer Progression and Metastasis by Reducing Its CpG Island Methylation

Human hedgehog-interacting protein (HHIP), a negative regulator of hedgehog (HH) signaling pathway, has been reported to be dysregulated in many types of cancer, including gastric cancer. However, the inhibitory role of HHIP as well as the underlying molecular mechanism of HHIP regulation in gastric cancer haven't been fully elucidated yet. In this study, we demonstrated that HHIP overexpression significantly suppressed the proliferation and invasion of AGS cells evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and transwell assays, respectively. Interestingly, methylation-specific polymerase chain reaction (MS-PCR, MSP) showed that HHIP overexpression dramatically decreased its de novo promoter methylation levels in AGS cells. Furthermore, HHIP expression was higher in adjacent non-cancerous tissue compared to matched gastric cancer tissue. High HHIP level was negatively correlated with metastasis (p = 0.035) but not local recurrence (p = 0.58). Taken together, our study suggested that HHIP can modulate gastric cancer progression and metastasis via regulation of its de novo promoter methylation levels in a feedback manner. Lower HHIP levels is positively associated with gastric cancer metastasis, which not only indicates HHIP could be served as a protective marker for gastric cancer, but also suggests restoring HHIP expression might be a potential therapeutic strategy for clinical treatment.

An update of nanoparticle-based approaches for glioblastoma multiforme immunotherapy

Glioblastoma multiforme is a serious medical issue in the brain oncology field due to its aggressiveness and recurrence. Immunotherapy has emerged as a valid approach to counteract the growth and metastasization of glioblastoma multiforme. Among the different innovative approaches investigated, nanoparticles gain attention because of their versatility which is key in allowing precise targeting of brain tumors and increasing targeted drug delivery to the brain, thus minimizing adverse effects. This article reviews the progress made in this field over the past 2 years, focusing on nonspherical and biomimetic particles and on vectors for the delivery of nucleic acids. However, challenges still need to be addressed, considering the improvement of the particles passage across the blood-meningeal barrier and/or the blood-brain barrier, promoting the clinical translatability of these approaches.

Smart Supra- and Macro-Molecular Tools for Biomedical Applications

Stimuli-responsive, “smart” polymeric materials used in the biomedical field function in a bio-mimicking manner by providing a non-linear response to triggers coming from a physiological microenvironment or other external source. They are built based on various chemical, physical, and biological tools that enable pH and/or temperature-stimulated changes in structural or physicochemical attributes, like shape, volume, solubility, supramolecular arrangement, and others. This review touches on some particular developments on the topic of stimuli-sensitive molecular tools for biomedical applications. Design and mechanistic details are provided concerning the smart synthetic instruments that are employed to prepare supra- and macro-molecular architectures with specific responses to external stimuli. Five major themes are approached: (i) temperature- and pH-responsive systems for controlled drug delivery; (ii) glycodynameric hydrogels for drug delivery; (iii) polymeric non-viral vectors for gene delivery; (iv) metallic nanoconjugates for biomedical applications; and, (v) smart organic tools for biomedical imaging.

Advances in nanotechnology-based strategies for the treatments of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS), also known as motor neuron disease (MND), is a progressive neurodegenerative disease that affects both upper and lower motor neurons, which results in loss of muscle control and eventual paralysis [1]. Currently, there are as yet unresolved challenges regarding efficient drug delivery into the central nervous system (CNS). These challenges can be attributed to multiple factors including the presence of the blood-brain barrier (BBB), blood-spinal cord barrier (BSCB), as well as the inherent characteristics of the drugs themselves (e.g. low solubility, insufficient bioavailability/bio-stability, 'off-target' effects) etc. As a result, conventional drug delivery systems may not facilitate adequate dosage of the required drugs for functional recovery in ALS patients. Nanotechnology-based strategies, however, employ engineered nanostructures that show great potential in delivering single or combined therapeutic agents to overcome the biological barriers, enhance interaction with targeted sites, improve drug bioavailability/bio-stability and achieve real-time tracking while minimizing the systemic side-effects. This review provides a concise discussion of recent advances in nanotechnology-based strategies in relation to combating specific pathophysiology relevant to ALS disease progression and investigates the future scope of using nanotechnology to develop innovative treatments for ALS patients.

Anti-ageing gene therapy: Not so far away?

Improving healthspan is the main objective of anti-ageing research. Currently, innovative gene therapy-based approaches seem to be among the most promising for preventing and treating chronic polygenic pathologies, including age-related ones. The gene-based therapy allows to modulate the genome architecture using both direct (e.g., by gene editing) and indirect (e.g., by viral or non-viral vectors) approaches. Nevertheless, considering the extraordinary complexity of processes involved in ageing and ageing-related diseases, the effectiveness of these therapeutic options is often unsatisfactory and limited by their side-effects. Thus, clinical implementation of such applications is certainly a long-time process that will require many translation phases for addressing challenges. However, after overcoming these issues, their implementation in clinical practice may obviously provide new possibilities in anti-ageing medicine. Here, we review and discuss recent advances in this rapidly developing research field.

Bone formation promoted by bone morphogenetic protein-2 plasmid-loaded porous silica nanoparticles with the involvement of autophagy

Gene therapy is one of the most common and effective ways for the regeneration of defective bone tissue, but even highly efficient gene delivery vectors are insufficient. In this study, bone morphogenetic protein-2 plasmid (pBMP-2) was encapsulated by polyethylenimine-modified porous silica nanoparticles (PPSNs), which were synthesized via an ethyl ether emulsion method. Owing to the high specific surface area and high absorption characteristics, low cytotoxicy PPSNs can efficiently load and protect pBMP-2. The resulting PPSN/pBMP-2 can transfect MC3T3-E1 cells effectively to promote osteogenic differentiation and increase calcium deposition in vitro. Interestingly, the mass of calcium deposition nodules decreased dur to the presence of an autophagy inhibitor, demonstrating that PPSNs stimulated the autophagy pathway. Because of their excellent biocompatibility, high transfection efficiency, and ability to stimulate autophagy, the as-prepared PPSN/pBMP-2 could efficiently transfect local cells in a defect area in vivo. Micro-computed tomography and histological images demonstrated that PPSN/pBMP-2 could efficiently promote new bone formation in a 5 mm sized rat calvarial defect model. Taken together, our newly synthesized PPSNs could efficiently carry pBMP-2 and deliver it to the target cells as well as stimulating the autophagy pathway, resulting in significant osteogenic differentiation and bone regeneration.

A Student's Guide to Neural Circuit Tracing

The mammalian nervous system is comprised of a seemingly infinitely complex network of specialized synaptic connections that coordinate the flow of information through it. The field of connectomics seeks to map the structure that underlies brain function at resolutions that range from the ultrastructural, which examines the organization of individual synapses that impinge upon a neuron, to the macroscopic, which examines gross connectivity between large brain regions. At the mesoscopic level, distant and local connections between neuronal populations are identified, providing insights into circuit-level architecture. Although neural tract tracing techniques have been available to experimental neuroscientists for many decades, considerable methodological advances have been made in the last 20 years due to synergies between the fields of molecular biology, virology, microscopy, computer science and genetics. As a consequence, investigators now enjoy an unprecedented toolbox of reagents that can be directed against selected subpopulations of neurons to identify their efferent and afferent connectomes. Unfortunately, the intersectional nature of this progress presents newcomers to the field with a daunting array of technologies that have emerged from disciplines they may not be familiar with. This review outlines the current state of mesoscale connectomic approaches, from data collection to analysis, written for the novice to this field. A brief history of neuroanatomy is followed by an assessment of the techniques used by contemporary neuroscientists to resolve mesoscale organization, such as conventional and viral tracers, and methods of selecting for sub-populations of neurons. We consider some weaknesses and bottlenecks of the most widely used approaches for the analysis and dissemination of tracing data and explore the trajectories that rapidly developing neuroanatomy technologies are likely to take.

Fifteen-minute consultation: A practical approach to developmental regression in children

Developmental regression is an important red flag in any child's developmental performance and should be recognised promptly. It is the loss of previously acquired skills and can affect any sphere of childhood development. Presentation and underlying causes are heterogeneous in nature, in turn presenting many clinical challenges. While broad, the causes of regression can be categorised based on clinical findings, so that investigation and management options can be tailored appropriately. It is extremely important to try and make a definitive diagnosis if possible. This allows appropriate initiation of treatment for potentially reversible causes and for specific therapies, which may alter disease progression and improve quality of life in some cases. This article outlines a systematic approach to the evaluation of a child with suspected regression, covering the nature of presentation, key differential diagnoses, first-line investigations and management.

Olesoxime in neurodegenerative diseases: Scrutinising a promising drug candidate

Over the last years, the experimental compound olesoxime, a mitochondria-targeting cholesterol derivative, has emerged as a promising drug candidate for neurodegenerative diseases. Numerous preclinical studies have successfully proved olesoxime's neuroprotective properties in cell and animal models of clinical conditions such as amyotrophic lateral sclerosis, Huntington disease, Parkinson disease, peripheral neuropathy and spinal muscular atrophy. The beneficial effects were attributed to olesoxime's potential impact on oxidative stress, mitochondrial permeability transition or cholesterol homoeostasis. Although no significant benefits have been demonstrated in patients of amyotrophic lateral sclerosis, and only the first 12 months of a phase II/III clinical trial showed an improvement in motor symptoms of spinal muscular atrophy, this orphan drug may still offer undiscovered potential in the treatment of neurological diseases. In our earlier preclinical studies, we demonstrated that administration of olesoxime in mouse and rat models of Huntington disease improved psychiatric and molecular phenotypes. Aside from stabilising mitochondrial function, the drug reduced the overactivation of calpains, a class of calcium-dependent proteases entangled in neurodegenerative conditions. This observation may be credited to olesoxime's action on calcium dyshomeostasis, a further hallmark in neurodegeneration, and linked to its targets TSPO and VDAC, two proteins of the outer mitochondrial membrane associated with mitochondrial calcium handling. Further research into the mode of action of olesoxime under pathological conditions, including its effect on neuronal calcium homeostasis, may strengthen the untapped potential of olesoxime or other similar compounds as a therapeutic for neurodegenerative diseases.

Characteristics and advantages of adeno-associated virus vector-mediated gene therapy for neurodegenerative diseases

Common neurodegenerative diseases of the central nervous system are characterized by progressive damage to the function of neurons, even leading to the permanent loss of function. Gene therapy via gene replacement or gene correction provides the potential for transformative therapies to delay or possibly stop further progression of the neurodegenerative disease in affected patients. Adeno-associated virus has been the vector of choice in recent clinical trials of therapies for neurodegenerative diseases due to its safety and efficiency in mediating gene transfer to the central nervous system. This review aims to discuss and summarize the progress and clinical applications of adeno-associated virus in neurodegenerative disease in central nervous system. Results from some clinical trials and successful cases of central neurodegenerative diseases deserve further study and exploration.

Small interfering RNA delivery to the neurons near the amyloid plaques for improved treatment of Alzheimer׳s disease

Gene therapy represents a promising treatment for the Alzheimer׳s disease (AD). However, gene delivery specific to brain lesions through systemic administration remains big challenge. In our previous work, we have developed an siRNA nanocomplex able to be specifically delivered to the amyloid plaques through surface modification with both CGN peptide for the blood–brain barrier (BBB) penetration and QSH peptide for β-amyloid binding. But, whether the as-designed nanocomplex could indeed improve the gene accumulation in the impaired neuron cells and ameliorate AD-associated symptoms remains further study. Herein, we prepared the nanocomplexes with an siRNA against β-site amyloid precursor protein-cleaving enzyme 1 (BACE1), the rate-limiting enzyme of Aβ production, as the therapeutic siRNA of AD. The nanocomplexes exhibited high distribution in the Aβ deposits-enriched hippocampus, especially in the neurons near the amyloid plaques after intravenous administration. In APP/PS1 transgenic mice, the nanocomplexes down-regulated BACE1 in both mRNA and protein levels, as well as Aβ and amyloid plaques to the level of wild-type mice. Moreover, the nanocomplexes significantly increased the level of synaptophysin and rescued memory loss of the AD transgenic mice without hematological or histological toxicity. Taken together, this work presented direct evidences that the design of precise gene delivery to the AD lesions markedly improves the therapeutic outcome.

Neuron-targeted caveolin-1 improves neuromuscular function and extends survival in SOD1G93A mice

Interventions that preserve motor neurons or restore functional motor neuroplasticity may extend longevity in amyotrophic lateral sclerosis (ALS). Delivery of neurotrophins may potentially revive degenerating motor neurons, yet this approach is dependent on the proper subcellular localization of neurotrophin receptor (NTR) to plasmalemmal signaling microdomains, termed membrane/lipid rafts (MLRs). We previously showed that overexpression of synapsin-driven caveolin-1 (Cav-1) (SynCav1) increases MLR localization of NTR [e.g., receptor tyrosine kinase B (TrkB)], promotes hippocampal synaptic and neuroplasticity, and significantly improves learning and memory in aged mice. The present study crossed a SynCav1 transgene-positive (SynCav1⁺) mouse with the mutant human superoxide dismutase glycine to alanine point mutation at amino acid 93 (hSOD1^G93A) mouse model of ALS. When compared with hSOD1^G93A, hSOD1^G93A/SynCav1⁺ mice exhibited greater body weight and longer survival as well as better motor function. Microscopic analyses of hSOD1^G93A/SynCav1⁺ spinal cords revealed preserved spinal cord α-motor neurons and preserved mitochondrial morphology. Moreover, hSOD1^G93A/SynCav1⁺ spinal cords contained more MLRs (cholera toxin subunit B positive) and MLR-associated TrkB and Cav-1 protein expression. These findings demonstrate that SynCav1 delays disease progression in a mouse model of ALS, potentially by preserving or restoring NTR expression and localization to MLRs.-Sawada, A., Wang, S., Jian, M., Leem, J., Wackerbarth, J., Egawa, J., Schilling, J. M., Platoshyn, O., Zemljic-Harpf, A., Roth, D. M., Patel, H. H., Patel, P. M., Marsala, M., Head, B. P. Neuron-targeted caveolin-1 improves neuromuscular function and extends survival in SOD1^G93A mice.

Molecular Insights into NR4A2(Nurr1): an Emerging Target for Neuroprotective Therapy Against Neuroinflammation and Neuronal Cell Death

NR4A2 is a nuclear receptor and a transcription factor, with distinctive physiological features. In the cell nuclei of the central nervous system, it is widely expressed and identified as a crucial regulator of dopaminergic (DA) neuronal differentiation, survival, and maintenance. Importantly, it has regulated different genes crucial for dopaminergic signals, and its expression has been diminished in both aged and PD post-mortem brains and reduced in PD patients. In microglia and astrocytes, the expression of NR4A2 has been found where it can be capable of inhibiting the expression of proinflammatory mediators; hence, it protected inflammation-mediated DA neuronal death. In addition, NR4A2 plays neuroprotective role via regulating different signals. However, NR4A2 has been mainly focused on Parkinson's research, but, in recent times, it has been studied in Alzheimer's disease (AD), multiple sclerosis (MS), and stroke. Altered expression of NR4A2 is connected to AD progression, and activation of its may improve cognitive function. It is downregulated in peripheral blood mononuclear cells of MS patients; nonetheless, its role in MS has not been fully clear. miR-145-5p known as a putative regulator of NR4A2 and in a middle cerebral artery occlusion/reperfusion model, anti-miR-145-5p administration promoted neurological outcomes in rat. To date, various activators and modulators of NR4A2 have been discovered and investigated as probable therapeutic drugs in neuroinflammatory and neuronal cell death models. The NR4A2 gene and cell-based therapy are described as promising drug candidates for neurodegenerative diseases. Moreover, microRNA might have a crucial role in neurodegeneration via affecting NR4A2 expression. Herein, we present the role of NR4A2 in neuroinflammation and neuronal cell death focusing on neurodegenerative conditions and display NR4A2 as a promising therapeutic target for the therapy of neuroprotection.

GDNF-mediated rescue of the nigrostriatal system depends on the degree of degeneration

Glial cell-line derived neurotrophic factor (GDNF) is a promising therapeutic molecule to treat Parkinson’s disease. Despite an excellent profile in experimental settings, clinical trials testing GDNF have failed. One of the theories to explain these negative outcomes is that the clinical trials were done in late-stage patients that have advanced nigrostriatal degeneration and may therefore not respond to a neurotrophic factor therapy. Based on this idea, we tested if the stage of nigrostriatal degeneration is important for GDNF-based therapies. Lentiviral vectors expressing regulated GDNF were delivered to the striatum of rats to allow GDNF expression to be turned on either while the nigrostriatal system was degenerating or after the nigrostriatal system had been fully lesioned by 6-OHDA. In the group of animals where GDNF expression was on during degeneration, neurons were rescued and there was a reversal of motor deficits. Turning GDNF expression on after the nigrostriatal system was lesioned did not rescue neurons or reverse motor deficits. In fact, these animals were indistinguishable from the control groups. Our results suggest that GDNF can reverse motor deficits and nigrostriatal pathology despite an ongoing nigrostriatal degeneration, if there is still a sufficient number of remaining neurons to respond to therapy.