Neurodegeneration and Neuro-Regeneration-Alzheimer's Disease and Stem Cell Therapy

Microglia Mediate the Occurrence and Development of Alzheimer's Disease Through Ligand-Receptor Axis Communication

Alzheimer's disease (AD) is a common neurodegenerative disease. Its onset is insidious and its progression is slow, making diagnosis difficult. In addition, its underlying molecular and cellular mechanisms remain unclear. In this study, clustering analysis was performed on single-cell RNA sequencing (scRNA-seq) data from the prefrontal cortex of 48 AD patients. Each sample module was identified to be a specific AD cell type, eight main brain cell types were identified, and the dysfunctional evolution of each cell type was further explored by pseudo-time analysis. Correlation analysis was then used to explore the relationship between AD cell types and pathological characteristics. In particular, intercellular communication between neurons and glial cells in AD patients was investigated by cell communication analysis. In patients, neuronal cells and glial cells significantly correlated with pathological features, and glial cells appear to play a key role in the development of AD through ligand-receptor axis communication. Marker genes involved in communication between these two cell types were identified using five types of modeling: logistic regression, multivariate logistic regression, least absolute shrinkage and selection operator (LASSO) and support vector machine (SVM). LASSO modeling identified CXCR4, EGFR, MAP4K4, and IGF1R as key genes in this communication. Our results support the idea that microglia play a role in the occurrence and development of AD through ligand-receptor axis communication. In particular, our analyses identify CXCR4, EGFR, MAP4K4, and IGF1R as potential biomarkers and therapeutic targets in AD.

Intrinsic positional memory guides target-specific axon regeneration in the zebrafish vagus nerve

Regeneration after peripheral nerve damage requires that axons re-grow to the correct target tissues in a process called target-specific regeneration. Although much is known about the mechanisms that promote axon re-growth, re-growing axons often fail to reach the correct targets, resulting in impaired nerve function. We know very little about how axons achieve target-specific regeneration, particularly in branched nerves that require distinct targeting decisions at branch points. The zebrafish vagus motor nerve is a branched nerve with a well-defined topographic organization. Here, we track regeneration of individual vagus axons after whole-nerve laser severing and find a robust capacity for target-specific, functional re-growth. We then develop a new single-cell chimera injury model for precise manipulation of axon-environment interactions and find that (1) the guidance mechanism used during regeneration is distinct from the nerve's developmental guidance mechanism, (2) target selection is specified by neurons' intrinsic memory of their position within the brain, and (3) targeting to a branch requires its pre-existing innervation. This work establishes the zebrafish vagus nerve as a tractable regeneration model and reveals the mechanistic basis of target-specific regeneration.

A 3-Gene-Based Diagnostic Signature in Alzheimer's Disease

BACKGROUND

Alzheimer's disease (AD) is a chronic neurodegenerative disease. In this study, potential diagnostic biomarkers were identified for AD.

METHODS

All AD samples and healthy samples were collected from 2 datasets in the GEO database, in which differentially expressed genes (DEGs) were analyzed by using the limma package of R language. GO and KEGG pathway enrichment was conducted basing on the DEGs via the clusterProfiler package of R. And, the PPI network construction and gene prediction were performed using the STRING database and Cytoscape. Then, a logistic regression model was constructed to predict the sample type.

RESULTS

Bioinformatic analysis of GEO datasets revealed 2,063 and 108 DEGs in GSE5281 and GSE4226 datasets, separately, and 15 overlapping DEGs were found. GO and KEGG enrichment analysis revealed terms associated with neurodevelopment. Then, we built a logistic regression model based on the hub genes from the PPI network and optimized the model to 3 genes (ALDOA, ENC1, and NFKBIA). The values of area under the curve of the training set GSE5281 and testing set GSE4226 were 0.9647 and 0.7857, respectively, which implied the efficacy of this model.

CONCLUSION

The comprehensive bioinformatic analysis of gene expression in AD patients and the effective logistic regression model built in our study may provide promising research value for diagnostic methods of AD.

Blood-Brain Barrier Breakdown: An Emerging Biomarker of Cognitive Impairment in Normal Aging and Dementia

The blood–brain barrier (BBB) plays a vital role in maintaining the specialized microenvironment of the neural tissue. It separates the peripheral circulatory system from the brain parenchyma while facilitating communication. Alterations in the distinct physiological properties of the BBB lead to BBB breakdown associated with normal aging and various neurodegenerative diseases. In this review, we first briefly discuss the aging process, then review the phenotypes and mechanisms of BBB breakdown associated with normal aging that further cause neurodegeneration and cognitive impairments. We also summarize dementia such as Alzheimer's disease (AD) and vascular dementia (VaD) and subsequently discuss the phenotypes and mechanisms of BBB disruption in dementia correlated with cognition decline. Overlaps between AD and VaD are also discussed. Techniques that could identify biomarkers associated with BBB breakdown are briefly summarized. Finally, we concluded that BBB breakdown could be used as an emerging biomarker to assist to diagnose cognitive impairment associated with normal aging and dementia.

Criss-crossing autism spectrum disorder and adult neurogenesis

Autism spectrum disorder (ASD) comprises a group of multifactorial neurodevelopmental disorders primarily characterized by deficits in social interaction and repetitive behavior. Although the onset is typically in early childhood, ASD poses a lifelong challenge for both patients and caretakers. Adult neurogenesis (AN) is the process by which new functional neurons are created from neural stem cells existing in the post-natal brain. The entire event is based on a sequence of cellular processes, such as proliferation, specification of cell fate, maturation, and ultimately, synaptic integration into the existing neural circuits. Hence, AN is implicated in structural and functional brain plasticity throughout life. Accumulating evidence shows that impaired AN may underlie some of the abnormal behavioral phenotypes seen in ASD. In this review, we approach the interconnections between the molecular pathways related to AN and ASD. We also discuss existing therapeutic approaches targeting such pathways both in preclinical and clinical studies. A deeper understanding of how ASD and AN reciprocally affect one another could reveal important converging pathways leading to the emergence of psychiatric disorders.

Epigenetic regulation of neural stem cells: The emerging role of nucleoporins

Nucleoporins (Nups) are components of the nuclear pore complex that, besides regulating nucleus-cytoplasmic transport, emerged as a hub for chromatin interaction and gene expression modulation. Specifically, Nups act in a dynamic manner both at specific gene level and in the topological organization of chromatin domains. As such, they play a fundamental role during development and determination of stemness/differentiation balance in stem cells. An increasing number of reports indicate the implication of Nups in many central nervous system functions with great impact on neurogenesis, neurophysiology, and neurological disorders. Nevertheless, the role of Nup-mediated epigenetic regulation in embryonic and adult neural stem cells (NSCs) is a field largely unexplored and the comprehension of their mechanisms of action is only beginning to be unveiled. After a brief overview of epigenetic mechanisms, we will present and discuss the emerging role of Nups as new effectors of neuroepigenetics and as dynamic platform for chromatin function with specific reference to the biology of NSCs.

A Transcriptome Community-and-Module Approach of the Human Mesoconnectome

Graph analysis allows exploring transcriptome compartments such as communities and modules for brain mesostructures. In this work, we proposed a bottom-up model of a gene regulatory network to brain-wise connectome workflow. We estimated the gene communities across all brain regions from the Allen Brain Atlas transcriptome database. We selected the communities method to yield the highest number of functional mesostructures in the network hierarchy organization, which allowed us to identify specific brain cell functions (e.g., neuroplasticity, axonogenesis and dendritogenesis communities). With these communities, we built brain-wise region modules that represent the connectome. Our findings match with previously described anatomical and functional brain circuits, such the default mode network and the default visual network, supporting the notion that the brain dynamics that carry out low- and higher-order functions originate from the modular composition of a GRN complex network.

The Influence of Virus Infection on Microglia and Accelerated Brain Aging

Microglia are the resident immune cells of the central nervous system contributing substantially to health and disease. There is increasing evidence that inflammatory microglia may induce or accelerate brain aging, by interfering with physiological repair and remodeling processes. Many viral infections affect the brain and interfere with microglia functions, including human immune deficiency virus, flaviviruses, SARS-CoV-2, influenza, and human herpes viruses. Especially chronic viral infections causing low-grade neuroinflammation may contribute to brain aging. This review elucidates the potential role of various neurotropic viruses in microglia-driven neurocognitive deficiencies and possibly accelerated brain aging.

Intravenous administration of mesenchymal stem cells reduces Tau phosphorylation and inflammation in the 3xTg-AD mouse model of Alzheimer's disease

Mesenchymal stem cell (MSC) administration is a novel and promising therapeutic approach for Alzheimer's disease (AD). Focusing on an intervention easily translatable into clinical practice, we administered allogeneic bone marrow-derived MSCs intravenously in a mouse model of AD (3xTg-AD). We systematically evaluated the effects of a single-dose and multiple-doses of MSCs in young and old mice (5 or 10 months old), comparing the short-term and long-term effects after 1, 2, or 7 months of treatment. A single dose of MSCs in young mice attenuated neuroinflammation 1 and 7 months after injection, whereas multiple-doses did not show any effect. Multiple-doses of MSCs (administered at 5 to 12 mo, or 10 to 12 mo) reduced the β-secretase cleavage of the amyloid precursor protein, although levels of Aβ-42 did not change. Most interestingly, multiple doses of MSCs affected tau hyperphosphorylation. MSCs administered in young mice for 7 months decreased the pathological tau phosphorylation at T205, S214, and T231. MSCs administered in old mice for 2 months decreased tau phosphorylation at S396. Our findings show how different timing and frequency of MSC injections can affect and modulate several aspects of the AD-like neuropathology in the 3xTg-AD mouse model, strengthening the concept of fine-tuning MSC therapy for Alzheimer's disease.

A Two-Stage Process for Differentiation of Wharton's Jelly-Derived Mesenchymal Stem Cells into Neuronal-like Cells

With no permanent cure for neurodegenerative diseases, the symptoms reappear shortly after the withdrawal of medicines. A better treatment outcome can be expected if the damaged neurons are partly replaced by functional neurons and/or they are repaired using trophic factors. In this regard, safe cell therapy has been considered as a potential alternative to conventional treatment. Here, we have described a two-stage culture process to differentiate Wharton Jelly mesenchymal stem cells (WJ-MSCs) into neuronal-like cells in the presence of various cues involved in neurogenesis. The fate of cells at the end of each stage was analyzed at the morphometric, transcriptional, and translational levels. In the first stage of priming, constitutively, wingless-activated WJ-MSCs crossed the lineage boundary in favor of neuroectodermal lineage, identified by the loss of mesenchymal genes with concomitant expression of neuron-specific markers, like SOX1, PAX6, NTRK1, and NEUROD2. Neuronal-like cells formed in the second stage expressed many mature neuronal proteins like Map2, neurofilament, and Tuj1 and possessed axon hillock-like structures. In conclusion, the differentiation of a large number of neuronal-like cells from nontumorigenic and trophic factors secreting WJ-MSCs promises the development of a therapeutic strategy to treat neurodegenerative diseases.

Alzheimer's disease drug development pipeline: 2021

INTRODUCTION

The number of individuals worldwide with Alzheimer's disease (AD) is growing at a rapid rate. New treatments are urgently needed. We review the current pipeline of drugs in clinical trials for the treatment of AD.

METHODS

We interrogated ClinicalTrials.gov, the federal registry of clinical trials to identify drugs in trials.

RESULTS

There are 126 agents in 152 trials assessing new therapies for AD: 28 treatments in Phase 3 trials, 74 in Phase 2, and 24 in Phase 1. The majority of drugs in trials (82.5%) target the underlying biology of AD with the intent of disease modification; 10.3% are putative cognitive enhancing agents; and 7.1% are drugs being developed to reduce neuropsychiatric symptoms.

DISCUSSION

This pipeline analysis shows that target biological processes are more diversified, biomarkers are more regularly used, and repurposed agents are being explored to determine their utility for the treatment of AD.

One Raft to Guide Them All, and in Axon Regeneration Inhibit Them

Central nervous system damage caused by traumatic injuries, iatrogenicity due to surgical interventions, stroke and neurodegenerative diseases is one of the most prevalent reasons for physical disability worldwide. During development, axons must elongate from the neuronal cell body to contact their precise target cell and establish functional connections. However, the capacity of the adult nervous system to restore its functionality after injury is limited. Given the inefficacy of the nervous system to heal and regenerate after damage, new therapies are under investigation to enhance axonal regeneration. Axon guidance cues and receptors, as well as the molecular machinery activated after nervous system damage, are organized into lipid raft microdomains, a term typically used to describe nanoscale membrane domains enriched in cholesterol and glycosphingolipids that act as signaling platforms for certain transmembrane proteins. Here, we systematically review the most recent findings that link the stability of lipid rafts and their composition with the capacity of axons to regenerate and rebuild functional neural circuits after damage.

Advances and Perspectives in Dental Pulp Stem Cell Based Neuroregeneration Therapies

Human dental pulp stem cells (hDPSCs) are some of the most promising stem cell types for regenerative therapies given their ability to grow in the absence of serum and their realistic possibility to be used in autologous grafts. In this review, we describe the particular advantages of hDPSCs for neuroregenerative cell therapies. We thoroughly discuss the knowledge about their embryonic origin and characteristics of their postnatal niche, as well as the current status of cell culture protocols to maximize their multilineage differentiation potential, highlighting some common issues when assessing neuronal differentiation fates of hDPSCs. We also review the recent progress on neuroprotective and immunomodulatory capacity of hDPSCs and their secreted extracellular vesicles, as well as their combination with scaffold materials to improve their functional integration on the injured central nervous system (CNS) and peripheral nervous system (PNS). Finally, we offer some perspectives on the current and possible future applications of hDPSCs in neuroregenerative cell therapies.

Exposure of Mesenchymal Stem Cells to an Alzheimer's Disease Environment Enhances Therapeutic Effects

Mesenchymal stem cells (MSCs) have emerged as a promising tool for the treatment of Alzheimer's disease (AD). Previous studies suggested that the coculture of human MSCs with AD in an in vitro model reduced the expression of amyloid-beta 42 (Aβ42) in the medium as well as the overexpression of amyloid-beta- (Aβ-) degrading enzymes such as neprilysin (NEP). We focused on the role of primed MSCs (human Wharton's jelly-derived mesenchymal stem cells (WJ-MSCs) exposed to an AD cell line via a coculture system) in reducing the levels of Aβ and inhibiting cell death. We demonstrated that mouse groups treated with naïve MSCs and primed MSCs showed significant reductions in cell death, ubiquitin conjugate levels, and Aβ levels, but the effects were greater in primed MSCs. Also, mRNA sequencing data analysis indicated that high levels of TGF-β induced primed-MSCs. Furthermore, treatment with TGF-β reduced Aβ expression in an AD transgenic mouse model. These results highlighted AD environmental preconditioning is a promising strategy to reduce cell death and ubiquitin conjugate levels and maintain the stemness of MSCs. Further, these data suggest that human WJ-MSCs exposed to an AD environment may represent a promising and novel therapy for AD.

Mitochondrial Behavior in Axon Degeneration and Regeneration

Mitochondria are organelles responsible for bioenergetic metabolism, calcium homeostasis, and signal transmission essential for neurons due to their high energy consumption. Accumulating evidence has demonstrated that mitochondria play a key role in axon degeneration and regeneration under physiological and pathological conditions. Mitochondrial dysfunction occurs at an early stage of axon degeneration and involves oxidative stress, energy deficiency, imbalance of mitochondrial dynamics, defects in mitochondrial transport, and mitophagy dysregulation. The restoration of these defective mitochondria by enhancing mitochondrial transport, clearance of reactive oxidative species (ROS), and improving bioenergetic can greatly contribute to axon regeneration. In this paper, we focus on the biological behavior of axonal mitochondria in aging, injury (e.g., traumatic brain and spinal cord injury), and neurodegenerative diseases (Alzheimer's disease, AD; Parkinson's disease, PD; Amyotrophic lateral sclerosis, ALS) and consider the role of mitochondria in axon regeneration. We also compare the behavior of mitochondria in different diseases and outline novel therapeutic strategies for addressing abnormal mitochondrial biological behavior to promote axonal regeneration in neurological diseases and injuries.

Combined treatment with valproic acid and estrogen has neuroprotective effects in ovariectomized mice with Alzheimer's disease

Postmenopausal women with Alzheimer’s disease (AD) exhibit dramatically reduced sensitivity to estrogen replacement therapy, which is though to be related to an estrogen receptor (ER)α/ERβ ratio imbalance arising from a significantly decreased level of ERs of the brain. The aim of our study was to investigate whether valproic acid (VPA) can enhance the beneficial effects of estrogen on cognitive function through restoration of ERα and ERβ expression in the brain. We removed the ovaries of female APP/PS1 mice to simulate the low estrogen levels present in postmenopausal women and then administered VPA (30 mg/kg, intraperitoneal injection, once daily), 17β-estradiol (E2) (2.4 μg, intraperitoneal injection, once daily), liquiritigenin (LG) (50 μg/kg, intragastric infusion, once daily), VPA + E2, or VPA + LG for 4 successive weeks. Compared with treatment with a single drug, treatment with VPA + E2 or VPA + LG significantly increased the level of glycogen synthase kinase 3β, increased the expression of estrogen receptor α, reduced the expression of small ubiquitin-like modifiers, and increased the level of estrogen receptor β. This resulted in enhanced sensitivity to estrogen therapy, reduced amyloid β aggregation, reduced abnormal phosphorylation of the tau protein, reduced neuronal loss, increased dendritic spine and postsynaptic density, and significantly alleviated memory loss and learning impairment in mice. This study was approved by the Chongqing Medical University Animal Protection and Ethics Committee, China on March 6, 2013.

Mitochondrial Dysfunction in Pancreatic Alpha and Beta Cells Associated with Type 2 Diabetes Mellitus

Type 2 diabetes mellitus is a complex multifactorial disease of epidemic proportions. It involves genetic and lifestyle factors that lead to dysregulations in hormone secretion and metabolic homeostasis. Accumulating evidence indicates that altered mitochondrial structure, function, and particularly bioenergetics of cells in different tissues have a central role in the pathogenesis of type 2 diabetes mellitus. In the present study, we explore how mitochondrial dysfunction impairs the coupling between metabolism and exocytosis in the pancreatic alpha and beta cells. We demonstrate that reduced mitochondrial ATP production is linked with the observed defects in insulin and glucagon secretion by utilizing computational modeling approach. Specifically, a 30-40% reduction in alpha cells' mitochondrial function leads to a pathological shift of glucagon secretion, characterized by oversecretion at high glucose concentrations and insufficient secretion in hypoglycemia. In beta cells, the impaired mitochondrial energy metabolism is accompanied by reduced insulin secretion at all glucose levels, but the differences, compared to a normal beta cell, are the most pronounced in hyperglycemia. These findings improve our understanding of metabolic pathways and mitochondrial bioenergetics in the pathology of type 2 diabetes mellitus and might help drive the development of innovative therapies to treat various metabolic diseases.

Scope of β-Secretase (BACE1)-Targeted Therapy in Alzheimer's Disease: Emphasizing the Flavonoid Based Natural Scaffold for BACE1 Inhibition

Alzheimer's disease (AD) is a progressive neurodegenerative disease and the most common form of dementia in the world. Studies report the presence of extracellular amyloid plaques consisting of β-amyloid peptide and intracellular tangles consisting of hyperphosphorylated tau proteins as the histopathological indicators of AD. The process of β-amyloid peptide generation by sequential cleavage of amyloid precursor protein by β-secretase (BACE1) and γ-secretase, followed by its aggregation to form amyloid plaques, is the mechanistic basis of the amyloid hypothesis. Other popular hypotheses related to the pathogenesis of AD include the tau hypothesis and the oxidative stress hypothesis. Various targets of the amyloid cascade are now in prime focus to develop drugs for AD. Many BACE1 inhibitors, β-amyloid aggregation inhibitors, and Aβ clearance strategies using monoclonal antibodies are in various stages of clinical trials. This review provides an in-depth evaluation of the role of BACE1 in disease pathogenesis and also highlights the therapeutic approaches developed to find more potent but less toxic inhibitors for BACE1, particularly emphasizing the natural scaffold as a nontoxic lead for BACE1 inhibition. Cellular targets and signaling cascades involving BACE1 have been highlighted to understand the physiological role of BACE1. This knowledge is extremely crucial to understand the toxicity evaluations for BACE1-targeted therapy. We have particularly highlighted the scope of flavonoids as a new generation of nontoxic BACE1 inhibitory scaffolds. The structure-activity relationship of BACE1 inhibition for this group of compounds has been highlighted to provide a guideline to design more selective highly potent inhibitors. The review aims to provide a holistic overview of BACE1-targeted therapy for AD that paves the way for future drug development.

Neurite Outgrowth-Promoting Activity of Compounds in PC12 Cells from Sunflower Seeds

In the current super-aging society, the establishment of methods for prevention and treatment of Alzheimer’s disease (AD) is an urgent task. One of the causes of AD is thought to be a decrease in the revel of nerve growth factor (NGF) in the brain. Compounds showing NGF-mimicking activity and NGF-enhancing activity have been examined as possible agents for improving symptoms. In the present study, sunflower seed extract was found to have neurite outgrowth-promoting activity, which is an NGF-enhancing activity, in PC12 cells. To investigate neurite outgrowth-promoting compounds from sunflower seed extract, bioassay-guided purification was carried out. The purified active fraction was obtained by liquid-liquid partition followed by some column chromatographies. Proton nuclear magnetic resonance and gas chromatography-mass spectrometry analyses of the purified active fraction indicated that the fraction was a mixture of β-sitosterol, stigmasterol and campesterol, with β-sitosterol being the main component. Neurite outgrowth-promoting activities of β-sitosterol, stigmasterol, campesterol and cholesterol were evaluated in PC12 cells. β-Sitosterol and stigmasterol showed the strongest activity of the four sterol compounds (β-sitosterol ≈ stigmasterol > campesterol > cholesterol), and cholesterol did not show any activity. The results indicated that β-sitosterol was the major component responsible for the neurite outgrowth-promoting activity of sunflower seeds. Results of immunostaining also showed that promotion by β-sitosterol of neurite formation induced by NGF was accompanied by neurofilament expression. β-Sitosterol, which showed NGF-enhancing activity, might be a candidate ingredient in food for prevention of AD.

Memory-Enhancing Effect of a Phytosome Containing the Combined Extract of Mulberry Fruit and Ginger in an Animal Model of Ischemic Stroke with Metabolic Syndrome

The prevalence of dementia following cerebral ischemia in metabolic syndrome (MetS) condition is increasing, and most of the cases are often severe. Unfortunately, no effective strategy for treating this condition is available. Based on the positive modulation effect of a polyphenol-rich substance on dementia and the improvement in bioavailability and stability of polyphenols induced by the phytosome technique together with the use of the synergistic concept, we hypothesized that a phytosome containing the combined extract of mulberry fruit and ginger (PMG) should mitigate dementia and memory impairment following ischemic stroke in MetS. MetS was induced in male Wistar rats weighing 180-200 g by exposure to a 16-week feeding period of high-carbohydrate high-fat (HCHF) diet. MetS rats were orally given PMG at doses of 50, 100, and 200 mg·kg-1 BW 21 days before and 21 days after the occlusion of the right middle cerebral artery (Rt. MCAO). Then, their spatial memory was determined and the possible underlying mechanisms explored via the alterations of acetylcholinesterase (AChE), neuron density, malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), interleukin-6 (IL-6), and signal transduction via extracellular signal-regulated kinase (ERK) pathway in both the cerebral cortex and the hippocampus. It was found that PMG significantly enhanced memory. It also decreased AChE, IL-6, and MDA but increased SOD, CAT, GSH-Px, neuron density, and phosphorylation of ERK. These data suggested the cognitive enhancing effect of PMG. The possible underlying mechanisms might occur partly via the improvement of cholinergic function via the ERK pathway together with the decrease in neurodegeneration induced by the reduction of oxidative stress and inflammation. However, a subchronic toxicity study is also required to assure the safety of PMG consumption before moving forward to a clinical trial study.

Therapeutic Potential of Phosphodiesterase Inhibitors against Neurodegeneration: The Perspective of the Medicinal Chemist

Increasing human life expectancy prompts the development of novel remedies for cognitive decline: 44 million people worldwide are affected by dementia, and this number is predicted to triple by 2050. Acetylcholinesterase and N-methyl-d-aspartate receptors represent the targets of currently available drugs for Alzheimer’s disease, which are characterized by limited efficacy. Thus, the search for therapeutic agents with alternative or combined mechanisms of action is wide open. Since variations in 3′,5′-cyclic adenosine monophosphate, 3′,5′-cyclic guanosine monophosphate, and/or nitric oxide levels interfere with downstream pathways involved in memory processes, evidence supporting the potential of phosphodiesterase (PDE) inhibitors in contrasting neurodegeneration should be critically considered. For the preparation of this Review, more than 140 scientific papers were retrieved by searching PubMed and Scopus databases. A systematic approach was adopted when overviewing the different PDE isoforms, taking into account details on brain localization, downstream molecular mechanisms, and inhibitors currently under study, according to available in vitro and in vivo data. In the context of drug repurposing, a section focusing on PDE5 was introduced. Original computational studies were performed to rationalize the emerging evidence that suggests the role of PDE5 inhibitors as multi-target agents against neurodegeneration. Moreover, since such compounds must cross the blood–brain barrier and reach inhibitory concentrations in the central nervous system to exert their therapeutic activity, physicochemical parameters were analyzed and discussed. Taken together, literature and computational data suggest that some PDE5 inhibitors, such as tadalafil, represent promising candidates.

Progress in Modeling and Targeting Inner Ear Disorders with Pluripotent Stem Cells

Sensorineural hearing loss and vestibular dysfunction are caused by damage to neurons and mechanosensitive hair cells, which do not regenerate to any clinically relevant extent in humans. Several protocols have been devised to direct pluripotent stem cells (PSCs) into inner ear hair cells and neurons, which display many properties of their native counterparts. The efficiency, reproducibility, and scalability of these protocols are enhanced by incorporating knowledge of inner ear development. Modeling human diseases in vitro through genetic manipulation of PSCs is already feasible, thereby permitting the elucidation of mechanistic understandings of a wide array of disease etiologies. Early studies on transplantation of PSC-derived otic progenitors have been successful in certain animal models, yet restoration of function and long-term cell survival remain unrealized. Through further research, PSC-based approaches will continue to revolutionize our understanding of inner ear biology and contribute to the development of therapeutic treatments for inner ear disorders.

The Business Process Model and Notation Used for the Representation of Alzheimer’s Disease Patients Care Process

Currently, the number of patients with neurological diseases is increasing, especially those older than 65 suffering from Alzheimer’s disease. This development increases the emphasis on understanding and mapping treatment and care processes, not only for the elderly. Service providers (of both treatment and care) are under general pressure to decrease charges and maintain or improve existing levels of care. This situation is significantly influenced by a comprehensive knowledge of the whole process and its values. This publication therefore aims to describe the fundamental procedural aspects of caring for patients with Alzheimer’s disease, using Business Process Model and Notation (BPMN). It also aims to show the possibilities of using BPMN in the description of treatment and care. Modeling of the business process is more frequently being applied not only by businesses but also by scientists involved in process models. It is used to model medical topics, with approximately 10% of its publications only, and most of these publications deal only with clinical pathways, not with overall treatment and care processes. However, the BPMN model allows the whole process of medical and nonmedical care for patients with Alzheimer’s disease to be described, including the decomposition of partial activities into individual threads and sub-processes or atomic tasks. This paper presents the BPMN modeling and mapping of the specific care path for neurodegenerative patients. The text provides a new perspective on the BPMN modeling of Alzheimer’s disease. The presented model offers the option of expanding treatment cost calculation to simulate the process using graphical tools and languages. The overall view of this system creates a much more complex concept of the system and its surroundings.