Stereotactic brain injection of human umbilical cord blood mesenchymal stem cells in patients with Alzheimer's disease dementia: A phase 1 clinical trial

Hallmarks of aging and Alzheimer's Disease pathogenesis: Paving the route for new therapeutic targets

Aging is the leading risk factor for Alzheimer's Disease (AD). Understanding the intricate interplay between biological aging and the AD pathophysiology may help to discover innovative treatments. The relationship between aging and core pathways of AD pathogenesis (amyloidopathy and tauopathy) have been extensively studied in preclinical models. However, the potential discordance between preclinical models and human pathology could represent a limitation in the identification of new therapeutic targets. This narrative review aims to gather the evidence currently available on the associations of β-Amyloid and Tau pathology with the hallmarks of aging in human studies. Briefly, our review suggests that while several hallmarks exhibit a robust association with AD pathogenesis (e.g., epigenetic alterations, chronic inflammation, dysbiosis), others (e.g., telomere attrition, cellular senescence, stem cell exhaustion) demonstrate either no relationship or weak associations. This is often due to limitations such as small sample sizes and study designs, being either cross-sectional or with short follow-up intervals, limiting the generalizability of the findings. Distinct hallmarks play varying roles in different stages of AD pathology, emphasizing the need for longitudinal studies with longer follow-up periods. Considering the intricate interconnections across the hallmarks of aging, future research on AD pathology should focus on multiple hallmarks simultaneously.

Cell-free biodegradable electroactive scaffold for urinary bladder tissue regeneration

Tissue engineering heavily relies on cell-seeded scaffolds to support the complex biological and mechanical requirements of a target organ. However, in addition to safety and efficacy, translation of tissue engineering technology will depend on manufacturability, affordability, and ease of adoption. Therefore, there is a need to develop scalable biomaterial scaffolds with sufficient bioactivity to eliminate the need for exogenous cell seeding. Herein, we describe implementation of an electroactive biodegradable elastomer for urinary bladder tissue engineering. To create an electrically conductive and mechanically robust scaffold to support bladder tissue regeneration, we develop a functionalization method wherein the hydrophobic conductive polymer poly(3,4-ethylenedioxythiophene) (PEDOT) is polymerized in situ within a similarly hydrophobic citrate-based elastomer poly(octamethylene-citrate-co-octanol) (POCO) film. We demonstrate the efficacy of this scaffold for bladder augmentation in primarily female athymic rats, comparing PEDOT-POCO scaffolds to mesenchymal stromal cell-seeded POCO scaffolds. PEDOT-POCO recovers bladder function and anatomical structure comparably to the cell-seeded POCO scaffolds and significantly better than non-cell-seeded POCO scaffolds. This manuscript reports a functionalization method that confers electroactivity to a biodegradable elastic scaffold, facilitating the successful restoration of anatomical and physiological function of an organ.

Stem cell therapy in Alzheimer's disease: current status and perspectives

An incurable neurogenerative illness, Alzheimer's disease, is the cause of most global health, medical, and social disasters. The two main symptoms are cognitive impairment and neuronal loss. Current medications that target tau protein tangles and Aβ plaques are not very effective because they only slow the symptoms of AD and do not repair damaged cells. Stem cell-based treatments, however, present an alternative strategy in the treatment of AD. They have the capacity to divide into specialized adult cells, have self-renewal abilities, and multiplication. Stem cells can now be employed as a donor source for cell therapy due to developments in stem cell technology. This review covers preclinical and clinical updates on studies based on targeting the tau protein tangles and Aβ plaque, as well as four types of stem cells employed in AD treatment. The review also outlines the two basic pathologic aspects, tau protein tangles and Aβ plaques, of AD.

The Potential of Mesenchymal Stem Cells in Treating Spinocerebellar Ataxia: Advances and Future Directions

Spinocerebellar ataxia (SCA) is a heterogeneous disorder characterized by impaired balance and coordination caused by cerebellar dysfunction. The absence of treatments approved by the U.S. Food and Drug Administration for SCA has driven the investigation of alternative therapeutic strategies, including stem cell therapy. Mesenchymal stem cells (MSCs), known for their multipotent capabilities, have demonstrated significant potential in treating SCA. This review examines how MSCs may promote neuronal growth, enhance synaptic connectivity, and modulate brain inflammation. Recent findings from preclinical and clinical studies are also reviewed, emphasizing the promise of MSC therapy in addressing the unmet needs of SCA patients. Furthermore, ongoing clinical trials and future directions are proposed to address the limitations of the current approaches.

Engineered serum markers for non-invasive monitoring of gene expression in the brain

Measurement of gene expression in the brain requires invasive analysis of brain tissue or non-invasive methods that are limited by low sensitivity. Here we introduce a method for non-invasive, multiplexed, site-specific monitoring of endogenous gene or transgene expression in the brain through engineered reporters called released markers of activity (RMAs). RMAs consist of an easily detectable reporter and a receptor-binding domain that enables transcytosis across the brain endothelium. RMAs are expressed in the brain but exit into the blood, where they can be easily measured. We show that expressing RMAs at a single mouse brain site representing approximately 1% of the brain volume provides up to a 100,000-fold signal increase over the baseline. Expression of RMAs in tens to hundreds of neurons is sufficient for their reliable detection. We demonstrate that chemogenetic activation of cells expressing Fos-responsive RMA increases serum RMA levels >6-fold compared to non-activated controls. RMAs provide a non-invasive method for repeatable, multiplexed monitoring of gene expression in the intact animal brain.

Mesenchymal stem cell therapy for Alzheimer's disease: A novel therapeutic approach for neurodegenerative diseases

Alzheimer's disease (AD) is one of the most progressive and prevalent types of neurodegenerative diseases in the aging population (aged >65 years) and is considered a major factor for dementia, affecting 55 million people worldwide. In the current scenario, drug-based therapies have been employed for the treatment of Alzheimer's disease but are only able to provide symptomatic relief to patients rather than a permanent solution from Alzheimer's. Recent advancements in stem cell research unlock new horizons for developing effective and highly potential therapeutic approaches due to their self-renewal, self-replicating, regenerative, and high differentiation capabilities. Stem cells come in multiple lineages such as embryonic, neural, and induced pluripotent, among others. Among different kinds of stem cells, mesenchymal stem cells are the most investigated for Alzheimer's treatment due to their multipotent nature, low immunogenicity, ability to penetrate the blood-brain barrier, and low risk of tumorigenesis, immune & inflammatory modulation, etc. They have been seen to substantially promote neurogenesis, synaptogenesis by secreting neurotrophic growth factors, as well as in ameliorating the Aβ and tau-mediated toxicity. This review covers the pathophysiology of AD, new medications, and therapies. Further, it will focus on the advancements and benefits of Mesenchymal Stem Cell therapies, their administration methods, clinical trials concerning AD progression, along with their future prospective.

A systematic review of clinical efficacy and safety of cell-based therapies in Alzheimer's disease

There is presently no disease-modifying therapy for Alzheimer's Disease (AD), which is the most prevalent cause of dementia.

Objective

This study aspires to estimate the efficacy and safety of cell-based treatments in AD.

Methods

Observing the Joanna Briggs Institute (JBI) methods and Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement, a systematic search was accomplished in PubMed, Medical Literature Analysis and Retrieval System Online (Medline, via Ovid), Embase; Cochrane, and Cumulative Index of Nursing and Allied Health Literature - CINAHL (via EBSCO) databases up to June 2023. The relevant clinical studies in which cell-based therapies were utilized to manage AD were included. The risk of bias was evaluated using the JBI checklists, based on the study designs.

Results

Out of 1,014 screened records, a total of five studies with 70 individuals (including 59 patients receiving stem cells and 11 placebo controls) were included. In all these studies, despite the discrepancy in the origin of stem cells, cell density, and transplant site, safety goals were obtained. The intracerebroventricular injection of adipose-derived stromal vascular fraction (ADSVF) and umbilical cord-derived mesenchymal stem cells (UC-MSCs), the intravenous injection of Lomecel-B, and the bilateral hippocampi and right precuneus injection of UC-MSCs are not linked to any significant safety concerns, according to the five included studies. Studies also revealed improvements in biomarkers and clinical outcomes as a secondary outcome. Three studies had no control groups and there are concerns regarding the similarity of the groups in others. Also, there is considerable risk of bias regarding the outcome assessment scales.

Conclusion

Cell-based therapies are well tolerated by AD patients, which emphasizes the need for further, carefully planned randomized studies to reach evidence-based clinical recommendations in this respect.

Advancements in strategies for overcoming the blood-brain barrier to deliver brain-targeted drugs

The blood-brain barrier is known to consist of a variety of cells and complex inter-cellular junctions that protect the vulnerable brain from neurotoxic compounds; however, it also complicates the pharmacological treatment of central nervous system disorders as most drugs are unable to penetrate the blood-brain barrier on the basis of their own structural properties. This dramatically diminished the therapeutic effect of the drug and compromised its biosafety. In response, a number of drugs are often delivered to brain lesions in invasive ways that bypass the obstruction of the blood-brain barrier, such as subdural administration, intrathecal administration, and convection-enhanced delivery. Nevertheless, these intrusive strategies introduce the risk of brain injury, limiting their clinical application. In recent years, the intensive development of nanomaterials science and the interdisciplinary convergence of medical engineering have brought light to the penetration of the blood-brain barrier for brain-targeted drugs. In this paper, we extensively discuss the limitations of the blood-brain barrier on drug delivery and non-invasive brain-targeted strategies such as nanomedicine and blood-brain barrier disruption. In the meantime, we analyze their strengths and limitations and provide outlooks on the further development of brain-targeted drug delivery systems.

Nanomedicine in Neuroprotection, Neuroregeneration, and Blood-Brain Barrier Modulation: A Narrative Review

Nanomedicine is a newer, promising approach to promote neuroprotection, neuroregeneration, and modulation of the blood-brain barrier. This review includes the integration of various nanomaterials in neurological disorders. In addition, gelatin-based hydrogels, which have huge potential due to biocompatibility, maintenance of porosity, and enhanced neural process outgrowth, are reviewed. Chemical modification of these hydrogels, especially with guanidine moieties, has shown improved neuron viability and underscores tailored biomaterial design in neural applications. This review further discusses strategies to modulate the blood-brain barrier-a factor critically associated with the effective delivery of drugs to the central nervous system. These advances bring supportive solutions to the solving of neurological conditions and innovative therapies for their treatment. Nanomedicine, as applied to neuroscience, presents a significant leap forward in new therapeutic strategies that might help raise the treatment and management of neurological disorders to much better levels. Our aim was to summarize the current state-of-knowledge in this field.

Mesenchymal stem cells biological and biotechnological advances: Implications for clinical applications

BACKGROUND

Mesenchymal stem cells (MSCs) are multipotent stem cells that are able to differentiate into multiple lineages including bone, cartilage, muscle and fat. They hold immunomodulatory properties and therapeutic ability to treat multiple diseases, including autoimmune and chronic degenerative diseases. In this article, we reviewed the different biological properties, applications and clinical trials of MSCs. Also, we discussed the basics of manufacturing conditions, quality control, and challenges facing MSCs in the clinical setting.

METHODS

Extensive review of the literature was conducted through the databases PubMed, Google Scholar, and Cochrane. Papers published since 2015 and covering the clinical applications and research of MSC therapy were considered. Furthermore, older papers were considered when referring to pioneering studies in the field.

RESULTS

The most widely studied stem cells in cell therapy and tissue repair are bone marrow-derived mesenchymal stem cells. Adipose tissue-derived stem cells became more common and to a lesser extent other stem cell sources e.g., foreskin derived MSCs. MSCs therapy were also studied in the setting of COVID-19 infections, ischemic strokes, autoimmune diseases, tumor development and graft rejection. Multiple obstacles, still face the standardization and optimization of MSC therapy such as the survival and the immunophenotype and the efficiency of transplanted cells. MSCs used in clinical settings displayed heterogeneity in their function despite their extraction from healthy donors and expression of similar surface markers.

CONCLUSION

Mesenchymal stem cells offer a rising therapeutic promise in various diseases. However, their potential use in clinical applications requires further investigation.

Olfactory Ecto-Mesenchymal Stem Cells in Modeling and Treating Alzheimer's Disease

Alzheimer's disease (AD) is a condition in the brain that is marked by a gradual and ongoing reduction in memory, thought, and the ability to perform simple tasks. AD has a poor prognosis but no cure yet. Therefore, the need for novel models to study its pathogenesis and therapeutic strategies is evident, as the brain poorly recovers after injury and neurodegenerative diseases and can neither replace dead neurons nor reinnervate target structures. Recently, mesenchymal stem cells (MSCs), particularly those from the human olfactory mucous membrane referred to as the olfactory ecto-MSCs (OE-MSCs), have emerged as a potential avenue to explore in modeling AD and developing therapeutics for the disease due to their lifelong regeneration potency and facile accessibility. This review provides a comprehensive summary of the current literature on isolating OE-MSCs and delves into whether they could be reliable models for studying AD pathogenesis. It also explores whether healthy individual-derived OE-MSCs could be therapeutic agents for the disease. Despite being a promising tool in modeling and developing therapies for AD, some significant issues remain, which are also discussed in the review.

MicroRNA (miRNA) as a biomarker for diagnosis, prognosis, and therapeutics molecules in neurodegenerative disease

Neurodegenerative diseases that include Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), Parkinson's disease (PD), Huntington's disease (HD), and multiple sclerosis (MS) that arise due to numerous causes like protein accumulation and autoimmunity characterized by neurologic depletion which lead to incapacity in normal physiological function such as thinking and movement in these patients. Glial cells perform an important role in protective neuronal function; in the case of neuroinflammation, glial cell dysfunction can promote the development of neurodegenerative diseases. miRNA that participates in gene regulation and plays a vital role in many biological processes in the body; in the central nervous system (CNS), it can play an essential part in neural maturation and differentiation. In neurodegenerative diseases, miRNA dysregulation occurs, enhancing the development of these diseases. In this review, we discuss neurodegenerative disease (Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS), and multiple sclerosis (MS)) and how miRNA is preserved as a diagnostic biomarker or therapeutic agent in these disorders. Finally, we highlight miRNA as therapy.

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.

Mechanistic insights and emerging therapeutic stratagems for Alzheimer's disease

Alzheimer's disease (AD), a multi-factorial neurodegenerative disorder has affected over 30 million individuals globally and these numbers are expected to increase in the coming decades. Current therapeutic interventions are largely ineffective as they focus on a single target. Development of an effective drug therapy requires a deep understanding of the various factors influencing the onset and progression of the disease. Aging and genetic factors exert a major influence on the development of AD. Other factors like post-viral infections, iron overload, gut dysbiosis, and vascular dysfunction also exacerbate the onset and progression of AD. Further, post-translational modifications in tau, DRP1, CREB, and p65 proteins increase the disease severity through triggering mitochondrial dysfunction, synaptic loss, and differential interaction of amyloid beta with different receptors leading to impaired intracellular signalling. With advancements in neuroscience tools, new inter-relations that aggravate AD are being discovered including pre-existing diseases and exposure to other pathogens. Simultaneously, new therapeutic strategies involving modulation of gene expression through targeted delivery or modulation with light, harnessing the immune response to promote clearance of amyloid deposits, introduction of stem cells and extracellular vesicles to replace the destroyed neurons, exploring new therapeutic molecules from plant, marine and biological sources delivered in the free state or through nanoparticles and use of non-pharmacological interventions like music, transcranial stimulation and yoga. Polypharmacology approaches involving combination of therapeutic agents are also under active investigation for superior therapeutic outcomes. This review elaborates on various disease-causing factors, their underlying mechanisms, the inter-play between different disease-causing players, and emerging therapeutic options including those under clinical trials, for treatment of AD. The challenges involved in AD therapy and the way forward have also been discussed.

Application of mesenchymal stem cells for neurodegenerative diseases therapy discovery

Neurodegenerative diseases are central or peripheral nervous system disorders associated with progressive brain cell degeneration. Common neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis have been widely studied. However, current therapeutics only reduce the symptoms and do not ameliorate the pathogenesis of these diseases. Recent studies suggested the roles of neuroinflammation, apoptosis, and oxidative stress in neurodegenerative diseases. Mesenchymal stem cells (MSCs) exert anti-apoptotic, anti-inflammatory, and antioxidative effects. Therefore, investigating the effects of MSCs and their applications may lead to the discovery of more effective therapies for neurodegenerative diseases. In this study, we review different approaches used to identify therapies for neurodegenerative diseases using MSCs.

Blood-based therapies to combat neurodegenerative diseases

Neurodegeneration, known as the progressive loss of neurons in terms of their structure and function, is the principal pathophysiological change found in the majority of brain-related disorders. Ageing has been considered the most well-established risk factor in most common neurodegenerative diseases, such as Parkinson's disease (PD) and Alzheimer's disease (AD). There is currently no effective treatment or cure for these diseases; the approved therapeutic options to date are only for palliative care. Ageing and neurodegenerative diseases are closely intertwined; reversing the aspects of brain ageing could theoretically mitigate age-related neurodegeneration. Ever since the regenerative properties of young blood on aged tissues came to light, substantial efforts have been focused on identifying and characterizing the circulating factors in the young and old systemic milieu that may attenuate or accentuate brain ageing and neurodegeneration. Later studies discovered the superiority of old plasma dilution in tissue rejuvenation, which is achieved through a molecular reset of the systemic proteome. These findings supported the use of therapeutic blood exchange for the treatment of degenerative diseases in older individuals. The first objective of this article is to explore the rejuvenating properties of blood-based therapies in the ageing brains and their therapeutic effects on AD. Then, we also look into the clinical applications, various limitations, and challenges associated with blood-based therapies for AD patients.

Management of oxidative stress for cell therapy through combinational approaches of stem cells, antioxidants, and photobiomodulation

Over the recent decades, stem cell-based therapies have been considered as a beneficial approach for the treatment of various diseases. In these types of therapies, the stem cells and their products are used as treating agents. Despite the helpful efficacy of stem cell-based therapies, there may be challenges. Oxidative stress (OS) is one of these challenges that can affect the therapeutic properties of stem cells. Therefore, it seems that employing strategies for the reduction of OS in combination with stem cell therapy can lead to better results of these therapies. Based on the available evidence, antioxidant therapy and photobiomodulation (PBM) are strategies that can regulate the OS in the cells. Antioxidant therapy is a method in which various antioxidants are used in the therapeutic processes. PBM is also the clinical application of light that gained importance in medicine. Antioxidants and PBM can regulate OS by the effect on mitochondria as an important source of OS in the cells. Considering the importance of OS in pathologic pathways and its effect on the treatment outcomes of stem cells, in the present review first the stem cell therapy and effects of OS on this type of therapy are summarized. Then, antioxidant therapy and PBM as approaches for reducing OS with a focus on mitochondrial function are discussed. Also, a novel combination treatment with the hope of achieving better and more stable outcomes in the treatment process of diseases is proposed.

MSC-Based Cell Therapy in Neurological Diseases: A Concise Review of the Literature in Pre-Clinical and Clinical Research

Mesenchymal stem cells (MSCs) are multipotent stromal cells with the ability to self-renew and multi-directional differentiation potential. Exogenously administered MSCs can migrate to damaged tissue sites and participate in the repair of damaged tissues. A large number of pre-clinical studies and clinical trials have demonstrated that MSCs have the potential to treat the abnormalities of congenital nervous system and neurodegenerative diseases. Therefore, MSCs hold great promise in the treatment of neurological diseases. Here, we summarize and highlight current progress in the understanding of the underlying mechanisms and strategies of MSC application in neurological diseases.

Allogeneic mesenchymal stem cells may be a viable treatment modality in cerebral palsy

BACKGROUND

Cerebral palsy (CP) describes a group of disorders affecting movement, balance, and posture. Disturbances in motor functions constitute the main body of CP symptoms. These symptoms surface in early childhood and patients are affected for the rest of their lives. Currently, treatment involves various pharmacotherapies for different types of CP, including antiepileptics for epilepsy and Botox A for focal spasticity. However, none of these methods can provide full symptom relief. This has prompted researchers to look for new treatment modalities, one of which is mesenchymal stem cell therapy (MSCT). Despite being a promising tool and offering a wide array of possibilities, mesenchymal stem cells (MSCs) still need to be investigated for their efficacy and safety.

AIM

To analyze the efficacy and safety of MSCT in CP patients.

METHODS

Our sample consists of four CP patients who cannot stand or walk without external support. All of these cases received allogeneic MSCT six times as 1 × 106/kg intrathecally, intravenously, and intramuscularly using umbilical cord-derived MSCs (UC-MSC). We monitored and assessed the patients pre- and post-treatment using the Wee Functional Independence Measure (WeeFIM), Gross Motor Function Classification System (GMFCS), and Manual Ability Classification Scale (MACS) instruments. We utilized the Modified Ashworth Scale (MAS) to measure spasticity.

RESULTS

We found significant improvements in MAS scores after the intervention on both sides. Two months: Right χ2 = 4000, P = 0.046, left χ2 = 4000, P = 0.046; four months: Right χ2 = 4000, P = 0.046, left χ2 = 4000, P = 0.046; 12 months: Right χ2 = 4000, P = 0.046, left χ2 = 4000, P = 0.046. However, there was no significant difference in motor functions based on WeeFIM results (P > 0.05). GMFCS and MACS scores differed significantly at 12 months after the intervention (P = 0.046, P = 0.046). Finally, there was no significant change in cognitive functions (P > 0.05).

CONCLUSION

In light of our findings, we believe that UC-MSC therapy has a positive effect on spasticity, and it partially improves motor functions.

Cell-free biodegradable electroactive scaffold for urinary bladder regeneration

Tissue engineering heavily relies on cell-seeded scaffolds to support the complex biological and mechanical requirements of a target organ. However, in addition to safety and efficacy, translation of tissue engineering technology will depend on manufacturability, affordability, and ease of adoption. Therefore, there is a need to develop scalable biomaterial scaffolds with sufficient bioactivity to eliminate the need for exogenous cell seeding. Herein, we describe synthesis, characterization, and implementation of an electroactive biodegradable elastomer for urinary bladder tissue engineering. To create an electrically conductive and mechanically robust scaffold to support bladder tissue regeneration, we developed a phase-compatible functionalization method wherein the hydrophobic conductive polymer poly(3,4-ethylenedioxythiophene) (PEDOT) was polymerized in situ within a similarly hydrophobic citrate-based elastomer poly(octamethylene-citrate-co-octanol) (POCO) film. We demonstrate the efficacy of this film as a scaffold for bladder augmentation in athymic rats, comparing PEDOT-POCO scaffolds to mesenchymal stromal cell-seeded POCO scaffolds. PEDOT-POCO recovered bladder function and anatomical structure comparably to the cell-seeded POCO scaffolds and significantly better than non-cell seeded POCO scaffolds. This manuscript reports: (1) a new phase-compatible functionalization method that confers electroactivity to a biodegradable elastic scaffold, and (2) the successful restoration of the anatomy and function of an organ using a cell-free electroactive scaffold.

Perinatal Tissue-Derived Stem Cells: An Emerging Therapeutic Strategy for Challenging Neurodegenerative Diseases

Over the past 20 years, stem cell therapy has been considered a promising option for treating numerous disorders, in particular, neurodegenerative disorders. Stem cells exert neuroprotective and neurodegenerative benefits through different mechanisms, such as the secretion of neurotrophic factors, cell replacement, the activation of endogenous stem cells, and decreased neuroinflammation. Several sources of stem cells have been proposed for transplantation and the restoration of damaged tissue. Over recent decades, intensive research has focused on gestational stem cells considered a novel resource for cell transplantation therapy. The present review provides an update on the recent preclinical/clinical applications of gestational stem cells for the treatment of protein-misfolding diseases including Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD) and amyotrophic lateral sclerosis (ALS). However, further studies should be encouraged to translate this promising therapeutic approach into the clinical setting.

A New Paradigm in Spinal Cord Injury Therapy: from Cell-free Treatment to Engineering Modifications

Spinal cord injury (SCI) is an intractable and poorly prognostic neurological disease, and current treatments are still unable to cure it completely and avoid sequelae. Extracellular vesicles (EVs), as important carriers of intercellular communication and pharmacological effects, are considered to be the most promising candidates for SCI therapy because of their low toxicity and immunogenicity, their ability to encapsulate endogenous bioactive molecules (e.g., proteins, lipids, and nucleic acids), and their ability to cross the blood-brain/cerebrospinal barriers. However, poor targeting, low retention rate, and limited therapeutic efficacy of natural EVs have bottlenecked EVs-based SCI therapy. A new paradigm for SCI treatment will be provided by engineering modified EVs. Furthermore, our limited understanding of the role of EVs in SCI pathology hinders the rational design of novel EVbased therapeutic approaches. In this study, we review the pathophysiology after SCI, especially the multicellular EVs-mediated crosstalk; briefly describe the shift from cellular to cell-free therapies for SCI treatment; discuss and analyze the issues related to the route and dose of EVs administration; summarize and present the common strategies for EVs drug loading in the treatment of SCI and point out the shortcomings of these drug loading methods; finally, we analyze and highlight the feasibility and advantages of bio-scaffold-encapsulated EVs for SCI treatment, providing scalable insights into cell-free therapy for SCI.

Positron Emission Tomography/Computed Tomography Imaging in Therapeutic Clinical Trials in Alzheimer's Disease: An Overview of the Current State of the Art of Research

The integration of positron emission tomography/computed tomography (PET/CT) has revolutionized the landscape of Alzheimer's disease (AD) research and therapeutic interventions. By combining structural and functional imaging, PET/CT provides a comprehensive understanding of disease pathology and response to treatment assessment. PET/CT, particularly with 2-deoxy-2-[fluorine-18]fluoro-D-glucose (18F-FDG), facilitates the visualization of glucose metabolism in the brain, enabling early diagnosis, staging, and monitoring of neurodegenerative disease progression. The advent of amyloid and tau PET imaging has further propelled the field forward, offering invaluable tools for tracking pathological hallmarks, assessing treatment response, and predicting clinical outcomes. While some therapeutic interventions targeting amyloid plaque load showed promising results with the reduction of cerebral amyloid accumulation over time, others failed to demonstrate a significant impact of anti-amyloid agents for reducing the amyloid plaques burden in AD brains. Tau PET imaging has conversely fueled the advent of disease-modifying therapeutic strategies in AD by supporting the assessment of neurofibrillary tangles of tau pathology deposition over time. Looking ahead, PET imaging holds immense promise for studying additional targets such as neuroinflammation, cholinergic deficit, and synaptic dysfunction. Advances in radiotracer development, dedicated brain PET/CT scanners, and Artificial Intelligence-powered software are poised to enhance the quality, sensitivity, and diagnostic power of molecular neuroimaging. Consequently, PET/CT remains at the forefront of AD research, offering unparalleled opportunities for unravelling the complexities of the disease and advancing therapeutic interventions, although it is not yet enough alone to allow patients' recruitment in therapeutic clinical trials.

The role of neurotrophic factors in novel, rapid psychiatric treatments

Neurotrophic factors are a family of growth factors that modulate cellular growth, survival, and differentiation. For many decades, it has been generally believed that a lack of neurotrophic support led to the decreased neuronal synaptic plasticity, death, and loss of non-neuronal supportive cells seen in neuropsychiatric disorders. Traditional psychiatric medications that lead to immediate increases in neurotransmitter levels at the synapse have been shown also to elevate synaptic neurotrophic levels over weeks, correlating with the time course of the therapeutic effects of these drugs. Recent advances in psychiatric treatments, such as ketamine and psychedelics, have shown a much faster onset of therapeutic effects (within minutes to hours). They have also been shown to lead to a rapid release of neurotrophins into the synapse. This has spurred a significant shift in understanding the role of neurotrophins and how the receptor tyrosine kinases that bind neurotrophins may work in concert with other signaling systems. In this review, this renewed understanding of synaptic receptor signaling interactions and the clinical implications of this mechanistic insight will be discussed within the larger context of the well-established roles of neurotrophic factors in psychiatric disorders and treatments.

Recent advancement in therapeutic strategies for Alzheimer's disease: Insights from clinical trials

Alzheimer's disease (AD) is the most prevalent form of dementia, characterized by the presence of plaques of amyloid beta and Tau proteins. There is currently no permanent cure for AD; the only medications approved by the FDA for mild to moderate AD are cholinesterase inhibitors, NMDA receptor antagonists, and immunotherapies against core pathophysiology, that provide temporary relief only. Researchers worldwide have made significant attempts to find new targets and develop innovative therapeutic molecules to treat AD. The FDA-approved drugs are palliative and couldn't restore the damaged neuron cells of AD. Stem cells have self-differentiation properties, making them prospective therapeutics to treat AD. The promising results in pre-clinical studies of stem cell therapy for AD seek attention worldwide. Various stem cells, mainly mesenchymal stem cells, are currently in different phases of clinical trials and need more advancements to take this therapy to the translational level. Here, we review research from the past decade that has identified several hypotheses related to AD pathology. Moreover, this article also focuses on the recent advancement in therapeutic strategies for AD treatment including immunotherapy and stem cell therapy detailing the clinical trials that are currently undergoing development.

Potential use of iPSCs for disease modeling, drug screening, and cell-based therapy for Alzheimer's disease

Alzheimer's disease (AD) is a chronic illness marked by increasing cognitive decline and nervous system deterioration. At this time, there is no known medication that will stop the course of Alzheimer's disease; instead, most symptoms are treated. Clinical trial failure rates for new drugs remain high, highlighting the urgent need for improved AD modeling for improving understanding of the underlying pathophysiology of disease and improving drug development. The development of induced pluripotent stem cells (iPSCs) has made it possible to model neurological diseases like AD, giving access to an infinite number of patient-derived cells capable of differentiating neuronal fates. This advance will accelerate Alzheimer's disease research and provide an opportunity to create more accurate patient-specific models of Alzheimer's disease to support pathophysiological research, drug development, and the potential application of stem cell-based therapeutics. This review article provides a complete summary of research done to date on the potential use of iPSCs from AD patients for disease modeling, drug discovery, and cell-based therapeutics. Current technological developments in AD research including 3D modeling, genome editing, gene therapy for AD, and research on familial (FAD) and sporadic (SAD) forms of the disease are discussed. Finally, we outline the issues that need to be elucidated and future directions for iPSC modeling in AD.

Mesenchymal stem cell secretome and extracellular vesicles for neurodegenerative diseases: Risk-benefit profile and next steps for the market access

Neurodegenerative diseases represent a growing burden on healthcare systems worldwide. Mesenchymal stem cells (MSCs) have shown promise as a potential therapy due to their neuroregenerative, neuroprotective, and immunomodulatory properties, which are, however, linked to the bioactive substances they release, collectively known as secretome. This paper provides an overview of the most recent research on the safety and efficacy of MSC-derived secretome and extracellular vesicles (EVs) in clinical (if available) and preclinical models of Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, multiple sclerosis, Huntington's disease, acute ischemic stroke, and spinal cord injury. The article explores the biologically active substances within MSC-secretome/EVs, the mechanisms responsible for the observed therapeutic effects, and the strategies that may be used to optimize MSC-secretome/EVs production based on specific therapeutic needs. The review concludes with a critical discussion of current clinical trials and a perspective on potential future directions in translating MSC-secretome and EVs into the clinic, specifically regarding how to address the challenges associated with their pharmaceutical manufacturing, including scalability, batch-to-batch consistency, adherence to Good Manufacturing Practices (GMP) guidelines, formulation, and storage, along with quality controls, access to the market and relative costs, value for money and impact on total expenditure.

Stem cells in central nervous system diseases: Promising therapeutic strategies

Central nervous system (CNS) diseases are a leading cause of death and disability. Due to CNS neurons have no self-renewal and regenerative ability as they mature, their loss after injury or disease is irreversible and often leads to functional impairments. Unfortunately, therapeutic options for CNS diseases are still limited, and effective treatments for these notorious diseases are warranted to be explored. At present, stem cell therapy has emerged as a potential therapeutic strategy for improving the prognosis of CNS diseases. Accumulating preclinical and clinical evidences have demonstrated that multiple molecular mechanisms, such as cell replacement, immunoregulation and neurotrophic effect, underlie the use of stem cell therapy for CNS diseases. However, several issues have yet to be addressed to support its clinical application. Thus, this review article aims to summarize the role and underlying mechanisms of stem cell therapy in treating CNS diseases. And it is worthy of further evaluation for the potential therapeutic applications of stem cell treatment in CNS disease.

Conditioned medium of human menstrual blood-derived endometrial stem cells protects against cell inflammation and apoptosis of Npc1KO N2a cells

Niemann-Pick disease type C1 (NPC1) is a hereditary neurodegenerative disorder caused by a mutation in the NPC1 gene. This gene encodes a transmembrane protein found in lysosomes. This disease characterized by hepatosplenomegaly, neurological impairments and premature death. Recent preclinical studies have shown promising results in using mesenchymal stem cells (MSCs) to alleviate the symptoms of NPC1. One type of MSCs, known as human menstrual blood-derived endometrial stem cells (MenSCs), has attracted attention due to its accessibility, abundant supply, and strong proliferation and regeneration capabilities. However, it remains uncertain whether the conditioned medium of MenSCs (MenSCs-CM) can effectively relieve the symptoms of NPC1. To investigate this further, we employed the CRISPR-Cas9 technique to successfully create a Npc1 gene knockout N2a cell line (Npc1KO N2a). Sanger sequencing confirmed the occurrence of Npc1 gene mutation in these cells, while western blotting revealed a lack of NPC1 protein expression. Filipin staining provided visual evidence of unesterified cholesterol accumulation in Npc1KO N2a cells. Moreover, Npc1KO N2a cells exhibited significantly decreased viability, increased inflammation, and heightened cell apoptosis. Notably, our study demonstrated that the viability of Npc1KO N2a cells was most significantly improved after being cultured by 36 h-collected MenSCs-CM for 0.5 days. Additionally, MenSCs-CM exhibited the ability to effectively reduce inflammation, counteract cell apoptosis, and ameliorate unesterified cholesterol accumulation in Npc1KO N2a cells. This groundbreaking finding establishes, for the first time, the protective effect of MenSCs-CM on N2a cells with Npc1 gene deletion. These findings suggest that the potential of MenSCs-CM as a beneficial therapeutic approach for NPC1 and other neurodegenerative diseases.

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.

Identification of potential biomarkers related to mesenchymal stem cell response in patients with Alzheimer's disease

BACKGROUND

Preclinical studies showed that mesenchymal stem cells (MSCs) ameliorate tau phosphorylation, amyloid-beta accumulation, and inflammation in Alzheimer's disease (AD) mouse models via secretion of neurotrophic factors and cytokines. We aimed to identify CSF biomarkers that can be used to predict or monitor the response to MSCs in patients with AD.

METHODS

AD patients were injected with human umbilical cord blood-MSCs (n = 22) or placebo (n = 12). The cerebrospinal fluid (CSF) samples were collected at baseline, one day after the first injection, and one day after the third injection. The patients injected with MSCs were classified into good responder (GR) or poor responder (PR) groups based on the rate of changes in the ratio of total-tau and phosphorylated-tau in the CSF. We selected three typical participants in each group, and their CSF protein levels were analyzed using liquid chromatography/tandem mass spectrometry (LC-MS/MS).

RESULTS

In the LC-MS/MS analysis, 1,667 proteins were identified. Eleven proteins showed significant differences between the typical GR and PR at baseline. Based on their significance level and known functions, two proteins, reticulocalbin-3 (RCN3) and follistatin-related protein 3 (FSTL3), were selected as potential biomarkers to predict MSC response. A total of 173 proteins showed significant change one day after the third injection compared to the baseline in typical GR. We excluded 45 proteins that showed significant change after the third injection compared to the baseline in the typical PR. Based on their significance level and known function, four proteins, scrapie-responsive protein 1 (SCRG1), neural proliferation differentiation and control protein (NPDC1), apolipoprotein E (ApoE), and cystatin C (CysC), were selected as potential biomarker to monitor MSC response. Additionally, functional analysis revealed that the increased CSF proteins after the third injection compared to the baseline in the typical GR were associated with synaptogenesis.

CONCLUSIONS

This study identified two proteins (RCN3 and FSTL3) that may be potential biomarkers for predicting MSC response and four proteins (SCRG1, NPDC1, ApoE, CysC) that may be potential biomarkers for monitoring MSC response in patients with AD. Further studies are needed to validate our results. Trial registration Clinical Trials.gov, NCT02054208. Registered on 4 February 2014. Samsung Medical Center IRB File No.2017-04-025. Registered on 20 June 2017.

Clinical utility of mesenchymal stem/stromal cells in regenerative medicine and cellular therapy

Mesenchymal stem/stromal cells (MSCs) have been carefully examined to have tremendous potential in regenerative medicine. With their immunomodulatory and regenerative properties, MSCs have numerous applications within the clinical sector. MSCs have the properties of multilineage differentiation, paracrine signaling, and can be isolated from various tissues, which makes them a key candidate for applications in numerous organ systems. To accentuate the importance of MSC therapy for a range of clinical indications, this review highlights MSC-specific studies on the musculoskeletal, nervous, cardiovascular, and immune systems where most trials are reported. Furthermore, an updated list of the different types of MSCs used in clinical trials, as well as the key characteristics of each type of MSCs are included. Many of the studies mentioned revolve around the properties of MSC, such as exosome usage and MSC co-cultures with other cell types. It is worth noting that MSC clinical usage is not limited to these four systems, and MSCs continue to be tested to repair, regenerate, or modulate other diseased or injured organ systems. This review provides an updated compilation of MSCs in clinical trials that paves the way for improvement in the field of MSC therapy.

Alzheimer's Disease Treatment: The Search for a Breakthrough

As the search for modalities to cure Alzheimer's disease (AD) has made slow progress, research has now turned to innovative pathways involving neural and peripheral inflammation and neuro-regeneration. Widely used AD treatments provide only symptomatic relief without changing the disease course. The recently FDA-approved anti-amyloid drugs, aducanumab and lecanemab, have demonstrated unclear real-world efficacy with a substantial side effect profile. Interest is growing in targeting the early stages of AD before irreversible pathologic changes so that cognitive function and neuronal viability can be preserved. Neuroinflammation is a fundamental feature of AD that involves complex relationships among cerebral immune cells and pro-inflammatory cytokines, which could be altered pharmacologically by AD therapy. Here, we provide an overview of the manipulations attempted in pre-clinical experiments. These include inhibition of microglial receptors, attenuation of inflammation and enhancement of toxin-clearing autophagy. In addition, modulation of the microbiome-brain-gut axis, dietary changes, and increased mental and physical exercise are under evaluation as ways to optimize brain health. As the scientific and medical communities work together, new solutions may be on the horizon to slow or halt AD progression.

Small Extracellular Vesicles' miRNAs: Biomarkers and Therapeutics for Neurodegenerative Diseases

Neurodegenerative diseases are critical in the healthcare system as patients suffer from progressive diseases despite currently available drug management. Indeed, the growing ageing population will burden the country's healthcare system and the caretakers. Thus, there is a need for new management that could stop or reverse the progression of neurodegenerative diseases. Stem cells possess a remarkable regenerative potential that has long been investigated to resolve these issues. Some breakthroughs have been achieved thus far to replace the damaged brain cells; however, the procedure's invasiveness has prompted scientists to investigate using stem-cell small extracellular vesicles (sEVs) as a non-invasive cell-free therapy to address the limitations of cell therapy. With the advancement of technology to understand the molecular changes of neurodegenerative diseases, efforts have been made to enrich stem cells' sEVs with miRNAs to increase the therapeutic efficacy of the sEVs. In this article, the pathophysiology of various neurodegenerative diseases is highlighted. The role of miRNAs from sEVs as biomarkers and treatments is also discussed. Lastly, the applications and delivery of stem cells and their miRNA-enriched sEVs for treating neurodegenerative diseases are emphasised and reviewed.

Stem cells in the treatment of Alzheimer's disease - Promises and pitfalls

Alzheimer's disease (AD) is the most widespread form of neurodegenerative disorder that causes memory loss and multiple cognitive issues. The underlying mechanisms of AD include the build-up of amyloid-β and phosphorylated tau, synaptic damage, elevated levels of microglia and astrocytes, abnormal microRNAs, mitochondrial dysfunction, hormonal imbalance, and age-related neuronal loss. However, the etiology of AD is complex and involves a multitude of environmental and genetic factors. Currently, available AD medications only alleviate symptoms and do not provide a permanent cure. Therefore, there is a need for therapies that can prevent or reverse cognitive decline, brain tissue loss, and neural instability. Stem cell therapy is a promising treatment for AD because stem cells possess the unique ability to differentiate into any type of cell and maintain their self-renewal. This article provides an overview of the pathophysiology of AD and existing pharmacological treatments. This review article focuses on the role of various types of stem cells in neuroregeneration, the potential challenges, and the future of stem cell-based therapies for AD, including nano delivery and gaps in stem cell technology.

Umbilical Cord Blood Transplantation: Connecting Its Origin to Its Future

Transplantation of umbilical cord blood (UCB) is an attractive alternative source of hematopoietic stem cells (HSCs). The unique properties of cord blood and its distinct immune tolerance and engraftment kinetics compared to bone marrow (BM) and peripheral blood progenitor cells, permit a wider disparity in human leukocyte antigen levels between a cord blood donor and recipient after an unrelated umbilical cord blood transplant (UCBT). In addition, it is readily available and has a lowered risk of graft-versus-host disease (GvHD), with similar long-term clinical outcomes, compared to BM transplants. However, the relatively low number of cells administered by UCB units, as well as the associated delayed engraftment and immune reconstitution, pose limitations to the wide application of UCBT. Research into several aspects of UCBT has been evaluated, including the ex vivo expansion of cord blood HSCs and the process of fucosylation to enhance engraftment. Additionally, UCB has also been used in the treatment of several neurodegenerative and cardiovascular disorders with varying degrees of success. In this article, we will discuss the biology, clinical indications, and benefits of UCBT in pediatric and adult populations. We will also discuss future directions for the use of cord blood.

Mesenchymal Stem Cell Therapy for Huntington Disease: A Meta-Analysis

Objective

Mesenchymal stem cell (MSC) therapy has been explored in Huntington disease (HD) as a potential therapeutic approach; however, a complete synthesis of these results is lacking. We conducted a meta-analysis to evaluate the effects of MSCs on HD.

Method

Eligible studies published before November 2022 were screened from Embase, PubMed, Web of Science, Medline, and Cochrane in accordance with PRISMA guidelines. ClinicalTrial.gov and the World Health Organization International Clinical Trials Registry Platform were also searched for registered clinical trials. The outcomes in rodent studies evaluated included morphological changes (striatal volume and ventricular volume), motor function (rotarod test, wire hang test, grip strength test, limb-clasping test, apomorphine-induced rotation test, and neuromuscular electromyography activity), cognition (Morris water maze test), and body weight.

Result

The initial search returned 362 records, of which 15 studies incorporating 346 HD rodents were eligible for meta-analysis. Larger striatal and smaller ventricular volumes were observed in MSC-treated animals compared to controls. MSCs transplanted before the occurrence of motor dysfunction rescued the motor incoordination of HD. Among different MSC sources, bone marrow mesenchymal stem cells were the most investigated cells and were effective in improving motor coordination. MSC therapy improved muscle strength, neuromuscular electromyography activity, cortex-related motor function, and striatum-related motor function, while cognition was not changed. The body weight of male HD rodents increased after MSC transplantation, while that of females was not affected.

Conclusion

Meta-analysis showed a positive effect of MSCs on HD rodents overall, as reflected in morphological changes, motor coordination, muscle strength, neuromuscular electromyography activity, cortex-related motor function, and striatum-related motor function, while cognition was not changed by MSC therapy.

Mesenchymal stem cells for regenerative medicine in central nervous system

Mesenchymal stem cells (MSCs) are multipotent stem cells, whose paracrine and immunomodulatory potential has made them a promising candidate for central nervous system (CNS) regeneration. Numerous studies have demonstrated that MSCs can promote immunomodulation, anti-apoptosis, and axon re-extension, which restore functional neural circuits. The therapeutic effects of MSCs have consequently been evaluated for application in various CNS diseases including spinal cord injury, cerebral ischemia, and neurodegenerative disease. In this review, we will focus on the research works published in the field of mechanisms and therapeutic effects of MSCs in CNS regeneration.

Nanoparticles-based anti-aging treatment of Alzheimer's disease

Age is the strongest risk factor for Alzheimer's disease (AD). In recent years, the relationship between aging and AD has been widely studied, with anti-aging therapeutics as the treatment for AD being one of the mainstream research directions. Therapeutics targeting senescent cells have shown improvement in AD symptoms and cerebral pathological changes, suggesting that anti-aging strategies may be a promising alternative for AD treatment. Nanoparticles represent an excellent approach for efficiently crossing the blood-brain barrier (BBB) to achieve better curative function and fewer side effects. Thereby, nanoparticles-based anti-aging treatment may exert potent anti-AD therapeutic efficacy. This review discusses the relationship between aging and AD and the application and prospect of anti-aging strategies and nanoparticle-based therapeutics in treating AD.

Engineered Extracellular Vesicles with SHP2 High Expression Promote Mitophagy for Alzheimer's Disease Treatment

Mitochondrial dysfunction is a fundamental pathological feature of Alzheimer's disease (AD). However, toxicity and poor brain enrichment of existing mitophagy inducers limit their further applications. In this study, a platform for AD therapy is developed using nanosized mesenchymal-stem-cells-derived extracellular vesicles with tyrosine phosphatase-2 (SHP2) high-expression (MSC-EVs-SHP2). The high blood-brain barrier penetration ability of MSC-EVs-SHP2 is demonstrated in AD-mice, facilitating SHP2 delivery to the brain. In addition, MSC-EVs-SHP2 significantly induces mitophagy of neuronal cells, which alleviates mitochondrial damage-mediated apoptosis and NLRP3 inflammasome activation. Mitophagy further diminishes neuronal cells apoptosis and neuroinflammation, culminating with rescued synaptic loss and cognitive decline in an AD mouse model. The EV-engineering technology provides a potential platform for effective AD therapy by inducing mitophagy.

The bHLH Transcription Factors in Neural Development and Therapeutic Applications for Neurodegenerative Diseases

The development of functional neural circuits in the central nervous system (CNS) requires the production of sufficient numbers of various types of neurons and glial cells, such as astrocytes and oligodendrocytes, at the appropriate periods and regions. Hence, severe neuronal loss of the circuits can cause neurodegenerative diseases such as Huntington's disease (HD), Parkinson's disease (PD), Alzheimer's disease (AD), and Amyotrophic Lateral Sclerosis (ALS). Treatment of such neurodegenerative diseases caused by neuronal loss includes some strategies of cell therapy employing stem cells (such as neural progenitor cells (NPCs)) and gene therapy through cell fate conversion. In this report, we review how bHLH acts as a regulator in neuronal differentiation, reprogramming, and cell fate determination. Moreover, several different researchers are conducting studies to determine the importance of bHLH factors to direct neuronal and glial cell fate specification and differentiation. Therefore, we also investigated the limitations and future directions of conversion or transdifferentiation using bHLH factors.

Stem-Cell-Based Therapy: The Celestial Weapon against Neurological Disorders

Stem cells are a versatile source for cell therapy. Their use is particularly significant for the treatment of neurological disorders for which no definitive conventional medical treatment is available. Neurological disorders are of diverse etiology and pathogenesis. Alzheimer's disease (AD) is caused by abnormal protein deposits, leading to progressive dementia. Parkinson's disease (PD) is due to the specific degeneration of the dopaminergic neurons causing motor and sensory impairment. Huntington's disease (HD) includes a transmittable gene mutation, and any treatment should involve gene modulation of the transplanted cells. Multiple sclerosis (MS) is an autoimmune disorder affecting multiple neurons sporadically but induces progressive neuronal dysfunction. Amyotrophic lateral sclerosis (ALS) impacts upper and lower motor neurons, leading to progressive muscle degeneration. This shows the need to try to tailor different types of cells to repair the specific defect characteristic of each disease. In recent years, several types of stem cells were used in different animal models, including transgenic animals of various neurologic disorders. Based on some of the successful animal studies, some clinical trials were designed and approved. Some studies were successful, others were terminated and, still, a few are ongoing. In this manuscript, we aim to review the current information on both the experimental and clinical trials of stem cell therapy in neurological disorders of various disease mechanisms. The different types of cells used, their mode of transplantation and the molecular and physiologic effects are discussed. Recommendations for future use and hopes are highlighted.

Ultrasound-mediated blood-brain barrier opening: An effective drug delivery system for theranostics of brain diseases

Blood-brain barrier (BBB) remains a significant obstacle to drug therapy for brain diseases. Focused ultrasound (FUS) combined with microbubbles (MBs) can locally and transiently open the BBB, providing a potential strategy for drug delivery across the BBB into the brain. Nowadays, taking advantage of this technology, many therapeutic agents, such as antibodies, growth factors, and nanomedicine formulations, are intensively investigated across the BBB into specific brain regions for the treatment of various brain diseases. Several preliminary clinical trials also have demonstrated its safety and good tolerance in patients. This review gives an overview of the basic mechanisms, ultrasound contrast agents, evaluation or monitoring methods, and medical applications of FUS-mediated BBB opening in glioblastoma, Alzheimer's disease, and Parkinson's disease.

The Link between Oxidative Stress, Mitochondrial Dysfunction and Neuroinflammation in the Pathophysiology of Alzheimer's Disease: Therapeutic Implications and Future Perspectives

Alzheimer's disease (AD), the most common form of dementia, has increasing incidence, increasing mortality rates, and poses a huge burden on healthcare. None of the currently approved drugs for the treatment of AD influence disease progression. Many clinical trials aiming at inhibiting amyloid plaque formation, increasing amyloid beta clearance, or inhibiting neurofibrillary tangle pathology yielded inconclusive results or failed. Meanwhile, research has identified many interlinked vicious cascades implicating oxidative stress, mitochondrial dysfunction, and chronic neuroinflammation, and has pointed to novel therapeutic targets such as improving mitochondrial bioenergetics and quality control, diminishing oxidative stress, or modulating the neuroinflammatory pathways. Many novel molecules tested in vitro or in animal models have proven efficient, but their translation into clinic needs further research regarding appropriate doses, delivery routes, and possible side effects. Cell-based therapies and extracellular vesicle-mediated delivery of messenger RNAs and microRNAs seem also promising strategies allowing to target specific signaling pathways, but need further research regarding the most appropriate harvesting and culture methods as well as control of the possible tumorigenic side effects. The rapidly developing area of nanotechnology could improve drug delivery and also be used in early diagnosis.

Exosomes as Potential Functional Nanomaterials for Tissue Engineering

Exosomes are cell-derived extracellular vesicles of 40-160 nm diameter, which carry numerous biomolecules and transmit information between cells. They are used as functional nanomaterials with great potential in biomedical areas, such as active agents and delivery systems for advanced drug delivery and disease therapy. In recent years, potential applications of exosomes in tissue engineering have attracted significant attention, and some critical progress has been made. This review gives a complete picture of exosomes and their applications in the regeneration of various tissues, such as the central nervous systems, kidney, bone, cartilage, heart, and endodontium. Approaches employed for modifying exosomes to equip them with excellent targeting capacity are summarized. Furthermore, current concerns and future outlook of exosomes in tissue engineering are discussed.

Umbilical cord mesenchymal stromal cells-from bench to bedside

In recent years, mesenchymal stromal cells (MSCs) have generated a lot of attention due to their paracrine and immuno-modulatory properties. mesenchymal stromal cells derived from the umbilical cord (UC) are becoming increasingly recognized as having increased therapeutic potential when compared to mesenchymal stromal cells from other sources. The purpose of this review is to provide an overview of the various compartments of umbilical cord tissue from which mesenchymal stromal cells can be isolated, the differences and similarities with respect to their regenerative and immuno-modulatory properties, as well as the single cell transcriptomic profiles of in vitro expanded and freshly isolated umbilical cord-mesenchymal stromal cells. In addition, we discuss the therapeutic potential and biodistribution of umbilical cord-mesenchymal stromal cells following systemic administration while providing an overview of pre-clinical and clinical trials involving umbilical cord-mesenchymal stromal cells and their associated secretome and extracellular vesicles (EVs). The clinical applications of umbilical cord-mesenchymal stromal cells are also discussed, especially in relation to obstacles and potential solutions for their effective translation from bench to bedside.

Mesenchymal stromal cells for the treatment of Alzheimer’s disease: Strategies and limitations

Alzheimer’s disease (AD) is a major cause of age-related dementia and is characterized by progressive brain damage that gradually destroys memory and the ability to learn, which ultimately leads to the decline of a patient’s ability to perform daily activities. Although some of the pharmacological treatments of AD are available for symptomatic relief, they are not able to limit the progression of AD and have several side effects. Mesenchymal stem/stromal cells (MSCs) could be a potential therapeutic option for treating AD due to their immunomodulatory, anti-inflammatory, regenerative, antioxidant, anti-apoptotic, and neuroprotective effects. MSCs not only secret neuroprotective and anti-inflammatory factors to promote the survival of neurons, but they also transfer functional mitochondria and miRNAs to boost their bioenergetic profile as well as improve microglial clearance of accumulated protein aggregates. This review focuses on different clinical and preclinical studies using MSC as a therapy for treating AD, their outcomes, limitations and the strategies to potentiate their clinical translation.

Emerging therapeutic developments in neurodegenerative diseases: A clinical investigation

Despite a century of intensive research, there is still a lack of disease-modifying treatments for neurodegenerative diseases that pose a threat to human society. A well-documented knowledge and resource gap has impeded the translation of fundamental research into promising therapies. In addition, the analysis of extensive preclinical data to allow the improved selection of therapeutic technologies and clinical candidates for further development is challenging. To address this need, we describe technologies that have emerged over the past decade that have enabled the development of novel, high-quality, cost-effective treatments for major neurodegenerative diseases, including Alzheimer's disease and Parkinson's disease. Moreover, we benchmark emerging technologies that have been adopted by top pharmaceutical companies looking to bridge the gap between drug discovery and drug development in neurodegenerative disease.

Applying stem cell therapy in intractable diseases: a narrative review of decades of progress and challenges

Background and Objective

Stem cell therapy (SCT) is one of the vastly researched branches of regenerative medicine as a therapeutic tool to treat incurable diseases. With the use of human stem cells such as embryonic stem cells (ESCs), adult stem cells (ASCs) and induced pluripotent stem cells (iPSCs), stem cell therapy aims to regenerate or repair damaged tissues and congenital defects. As stem cells are able to undergo infinite self-renewal, differentiate into various types of cells and secrete protective paracrine factors, many researchers have investigated the potential of SCT in regenerative medicine. Therefore, this review aims to provide a comprehensive review on the recent application of SCT in various intractable diseases, namely, haematological diseases, neurological diseases, diabetes mellitus, retinal degenerative disorders and COVID-19 infections along with the challenges faced in the clinical translation of SCT.

Methods

An extensive search was conducted on Google scholar, PubMed and Clinicaltrials.gov using related keywords. Latest articles on stem cell therapy application in selected diseases along with their challenges in clinical applications were selected.

Key content and findings

In vitro and in vivo studies involving SCT are shown to be safe and efficacious in treating various diseases covered in this review. There are also a number of small-scale clinical trials that validated the positive therapeutic outcomes of SCT. Nevertheless, the effectiveness of SCT are highly variable as some SCT works best in patients with early-stage diseases while in other diseases, SCT is more likely to work in patients in late stages of illnesses. Among the challenges identified in SCT translation are uncertainty in the underlying stem cell mechanism, ethical issues, genetic instability and immune rejection.

Conclusions

SCT will be a revolutionary treatment in the future that will provide hope to patients with intractable diseases. Therefore, studies ought to be done to ascertain the long-term effects of SCT while addressing the challenges faced in validating SCT for clinical use. Moreover, as there are many studies investigating the safety and efficacy of SCT, future studies should look into elucidating the regenerative and reparative capabilities of stem cells which largely remains unknown.