Diversity of Adult Neural Stem and Progenitor Cells in Physiology and Disease

Roles of cerebrospinal fluid-contacting neurons as potential neural stem cells in the repair and regeneration of spinal cord injuries

Cerebrospinal fluid-contacting neurons (CSF-cNs) represent a distinct group of interneurons characterized by their prominent apical globular protrusions penetrating the spinal cord's central canal and their basal axons extending towards adjacent cells. Identified nearly a century back, the specific roles and attributes of CSF-cNs have just started to emerge due to the historical lack of definitive markers. Recent findings have confirmed that CSF-cNs expressing PKD2L1 possess attributes of neural stem cells, suggesting a critical function in the regeneration processes following spinal cord injuries. This review aims to elucidate the molecular markers of CSF-cNs as potential neural stem cells during spinal cord development and assess their roles post-spinal cord injury, with an emphasis on their potential therapeutic implications for spinal cord repair.

Neural regeneration in the human central nervous system-from understanding the underlying mechanisms to developing treatments. Where do we stand today?

Mature neurons in the human central nervous system (CNS) fail to regenerate after injuries. This is a common denominator across different aetiologies, including multiple sclerosis, spinal cord injury and ischemic stroke. The lack of regeneration leads to permanent functional deficits with a substantial impact on patient quality of life, representing a significant socioeconomic burden worldwide. Great efforts have been made to decipher the responsible mechanisms and we now know that potent intra- and extracellular barriers prevent axonal repair. This knowledge has resulted in numerous clinical trials, aiming to promote neuroregeneration through different approaches. Here, we summarize the current understanding of the causes to the poor regeneration within the human CNS. We also review the results of the treatment attempts that have been translated into clinical trials so far.

AAV6 mediated Gsx1 expression in neural stem progenitor cells promotes neurogenesis and restores locomotor function after contusion spinal cord injury

Genomic screened homeobox 1 (Gsx1 or Gsh1) is a neurogenic transcription factor required for the generation of excitatory and inhibitory interneurons during spinal cord development. In the adult, lentivirus (LV) mediated Gsx1 expression promotes neural regeneration and functional locomotor recovery in a mouse model of lateral hemisection spinal cord injury (SCI). The LV delivery method is clinically unsafe due to insertional mutations to the host DNA. In addition, the most common clinical case of SCI is contusion/compression. In this study, we identify that adeno-associated virus serotype 6 (AAV6) preferentially infects neural stem/progenitor cells (NSPCs) in the injured spinal cord. Using a rat model of contusion SCI, we demonstrate that AAV6 mediated Gsx1 expression promotes neurogenesis, increases the number of neuroblasts/immature neurons, restores excitatory/inhibitory neuron balance and serotonergic neuronal activity through the lesion core, and promotes locomotor functional recovery. Our findings support that AAV6 preferentially targets NSPCs for gene delivery and confirmed Gsx1 efficacy in clinically relevant rat model of contusion SCI.

Environmental toxicology of bisphenol A: Mechanistic insights and clinical implications on the neuroendocrine system

Bisphenol A (BPA) is a widely used environmental estrogen found in a variety of products, including food packaging, canned goods, baby bottle soothers, reusable cups, medical devices, tableware, dental sealants, and other consumer goods. This substance has been found to have detrimental effects on both the environment and human health, particularly on the reproductive, immune, embryonic development, nervous, endocrine, and respiratory systems. This paper aims to provide a comprehensive review of the effects of BPA on the neuroendocrine system, with a primary focus on its impact on the brain, neurons, oligodendrocytes, neural stem cell proliferation, DNA damage, and behavioral development. Additionally, the review explores the clinical implications of BPA, specifically examining its role in the onset and progression of various diseases associated with the neuroendocrine metabolic system. By delving into the mechanistic analysis and clinical implications, this review aims to serve as a valuable resource for studying the impacts of BPA exposure on organisms.

Stem Cell Therapy for the Treatment of Parkinson's Disease: What Promise Does it Hold?

Parkinson's disease (PD) is a common, progressive neurodegenerative disorder characterized by substantia nigra dopamine cell death and a varied clinical picture that affects older people. Although more than two centuries have passed since the earliest attempts to find a cure for PD, it remains an unresolved problem. With this in mind, cell replacement therapy is a new strategy for treating PD. This novel approach aims to replace degenerated dopaminergic (DAergic) neurons with new ones or provide a new source of cells that can differentiate into DAergic neurons. Induced pluripotent stem cells (iPSCs), mesenchymal stem cells (MSCs), neural stem cells (NSCs), and embryonic stem cells (ESCs) are among the cells considered for transplantation therapies. Recently disease-modifying strategies like cell replacement therapies combined with other therapeutic approaches, such as utilizing natural compounds or biomaterials, are proposed to modify the underlying neurodegeneration. In the present review, we discuss the current advances in cell replacement therapy for PD and summarize the existing experimental and clinical evidence supporting this approach.

Sodium Butyrate Induced Neural Stem/Progenitor Cell Death in an Experimental Model of Japanese Encephalitis

The anti-inflammatory and neuroprotective effects of short chain fatty acid (SCFA) butyrate have been explored in a wide array of neurological pathologies. It is a 4-carbon SCFA produced from the fermentation of dietary fibers by the gut-microbiota. As evident from previous literature, butyrate plays a wide array of functions in CNS and interestingly enhances the differentiation potential of Neural stem/Progenitor Cells (NSPCs). Japanese encephalitis virus (JEV) is a well-known member of the Flaviviridae family and has been shown to alter neural stem cell pool of the brain, causing devastating consequences. In this study, we administered sodium butyrate (NaB) post JEV infection in BALB/c mouse model to examine any possible amelioration of the viral infection in NSPCs. In addition, ex vivo neurospheres and in vitro model of NSPCs were also used to study the effect of sodium butyrate in JEV infection. As an unprecedented finding, butyrate treated infected animals presented early onset of symptoms, as compared to their respective JEV infected groups. Alongside, we observed an increased viral load in NSPCs isolated from these animals as well as in cell culture models upon sodium butyrate treatment. Cytometric bead array analysis also revealed an increase in inflammatory cytokines, particularly, MCP-1 and IL-6. Further, increased expression of the key members of the canonical NF-κB pathway, viz-a-viz p-NF-κB, p-Iκ-Bα and p-IKK was observed. Overall, the increased inflammation and cell death caused early symptom progression in NaB-treated JEV infected animal model, which is contradictory to the well documented protective nature of NaB and therefore a better understanding of SCFA-based modulation of the gut-brain axis in viral infections is required.

CCN-Hippo YAP signaling in vision and its role in neuronal, glial and vascular cell function and behavior

The retina is a highly specialized tissue composed of a network of neurons, glia, and vascular and epithelial cells; all working together to coordinate and transduce visual signals to the brain. The retinal extracellular matrix (ECM) shapes the structural environment in the retina but also supplies resident cells with proper chemical and mechanical signals to regulate cell function and behavior and maintain tissue homeostasis. As such, the ECM affects virtually all aspects of retina development, function and pathology. ECM-derived regulatory cues influence intracellular signaling and cell function. Reversibly, changes in intracellular signaling programs result in alteration of the ECM and downstream ECM-mediated signaling network. Our functional studies in vitro, genetic studies in mice, and multi omics analyses have provided evidence that a subset of ECM proteins referred to as cellular communication network (CCN) affects several aspects of retinal neuronal and vascular development and function. Retinal progenitor, glia and vascular cells are major sources of CCN proteins particularly CCN1 and CCN2. We found that expression of the CCN1 and CCN2 genes is dependent on the activity of YAP, the core component of the hippo-YAP signaling pathway. Central to the Hippo pathway is a conserved cascade of inhibitory kinases that regulate the activity of YAP, the final transducer of this pathway. Reversibly, YAP expression and/or activity is dependent on CCN1 and CCN2 downstream signaling, which creates a positive or negative feedforward loop driving developmental processes (e.g., neurogenesis, gliogenesis, angiogenesis, barriergenesis) and, when dysregulated, disease progression in a range of retinal neurovascular disorders. Here we describe mechanistic hints involving the CCN-Hippo-YAP regulatory axis in retina development and function. This regulatory pathway represents an opportunity for targeted therapies in neurovascular and neurodegenerative diseases. The CCN-YAP regulatory loop in development and pathology.

Role of brahma-related gene 1/brahma-associated factor subunits in neural stem/progenitor cells and related neural developmental disorders

Different fates of neural stem/progenitor cells (NSPCs) and their progeny are determined by the gene regulatory network, where a chromatin-remodeling complex affects synergy with other regulators. Here, we review recent research progress indicating that the BRG1/BRM-associated factor (BAF) complex plays an important role in NSPCs during neural development and neural developmental disorders. Several studies based on animal models have shown that mutations in the BAF complex may cause abnormal neural differentiation, which can also lead to various diseases in humans. We discussed BAF complex subunits and their main characteristics in NSPCs. With advances in studies of human pluripotent stem cells and the feasibility of driving their differentiation into NSPCs, we can now investigate the role of the BAF complex in regulating the balance between self-renewal and differentiation of NSPCs. Considering recent progress in these research areas, we suggest that three approaches should be used in investigations in the near future. Sequencing of whole human exome and genome-wide association studies suggest that mutations in the subunits of the BAF complex are related to neurodevelopmental disorders. More insight into the mechanism of BAF complex regulation in NSPCs during neural cell fate decisions and neurodevelopment may help in exploiting new methods for clinical applications.

The Use of Stem Cells as a Potential Treatment Method for Selected Neurodegenerative Diseases: Review

Stem cells have been the subject of research for years due to their enormous therapeutic potential. Most neurological diseases such as multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS), Alzheimer's disease (AD), Parkinson's disease (PD), and Huntington's disease (HD) are incurable or very difficult to treat. Therefore new therapies are sought in which autologous stem cells are used. They are often the patient's only hope for recovery or slowing down the progress of the disease symptoms. The most important conclusions arise after analyzing the literature on the use of stem cells in neurodegenerative diseases. The effectiveness of MSC cell therapy has been confirmed in ALS and HD therapy. MSC cells slow down ALS progression and show early promising signs of efficacy. In HD, they reduced huntingtin (Htt) aggregation and stimulation of endogenous neurogenesis. MS therapy with hematopoietic stem cells (HSCs) inducted significant recalibration of pro-inflammatory and immunoregulatory components of the immune system. iPSC cells allow for accurate PD modeling. They are patient-specific and therefore minimize the risk of immune rejection and, in long-term observation, did not form any tumors in the brain. Extracellular vesicles derived from bone marrow mesenchymal stromal cells (BM-MSC-EVs) and Human adipose-derived stromal/stem cells (hASCs) cells are widely used to treat AD. Due to the reduction of Aβ42 deposits and increasing the survival of neurons, they improve memory and learning abilities. Despite many animal models and clinical trial studies, cell therapy still needs to be refined to increase its effectiveness in the human body.

Neural stem cell transplantation in patients with progressive multiple sclerosis: an open-label, phase 1 study

Innovative pro-regenerative treatment strategies for progressive multiple sclerosis (PMS), combining neuroprotection and immunomodulation, represent an unmet need. Neural precursor cells (NPCs) transplanted in animal models of multiple sclerosis have shown preclinical efficacy by promoting neuroprotection and remyelination by releasing molecules sustaining trophic support and neural plasticity. Here we present the results of STEMS, a prospective, therapeutic exploratory, non-randomized, open-label, single-dose-finding phase 1 clinical trial ( NCT03269071 , EudraCT 2016-002020-86), performed at San Raffaele Hospital in Milan, Italy, evaluating the feasibility, safety and tolerability of intrathecally transplanted human fetal NPCs (hfNPCs) in 12 patients with PMS (with evidence of disease progression, Expanded Disability Status Scale ≥6.5, age 18-55 years, disease duration 2-20 years, without any alternative approved therapy). The safety primary outcome was reached, with no severe adverse reactions related to hfNPCs at 2-year follow-up, clearly demonstrating that hfNPC therapy in PMS is feasible, safe and tolerable. Exploratory secondary analyses showed a lower rate of brain atrophy in patients receiving the highest dosage of hfNPCs and increased cerebrospinal fluid levels of anti-inflammatory and neuroprotective molecules. Although preliminary, these results support the rationale and value of future clinical studies with the highest dose of hfNPCs in a larger cohort of patients.

Unraveling the Mechanisms of Clinical Drugs-Induced Neural Tube Defects Based on Network Pharmacology and Molecular Docking Analysis

Chemotherapeutic agents such as methotrexate (MTX), raltitrexed (RTX), 5-fluorouracil (5-FU), hydroxyurea (HU), and retinoic acid (RA), and valproic acid (VPA), an antiepileptic drug, all can cause malformations in the developing central nervous system (CNS), such as neural tube defects (NTDs). However, the common pathogenic mechanisms remain unclear. This study aimed to explore the mechanisms of NTDs caused by MTX, RTX, 5-FU, HU, RA, and VPA (MRFHRV), based on network pharmacology and molecular biology experiments. The MRFHRV targets were integrated with disease targets, to find the potential molecules related to MRFHRV-induced NTDs. Protein-protein interaction analysis and molecular docking were performed to analyze these common targets. Utilizing the kyoto encyclopedia of genes and genomes (KEGG) signaling pathways, we analyzed and searched the possible causative pathogenic mechanisms by crucial targets and the signaling pathway. Results showed that MRFHRV induced NTDs through several key targets (including TP53, MAPK1, HSP90AA1, ESR1, GRB2, HDAC1, EGFR, PIK3CA, RXRA, and FYN) and multiple signaling pathways such as PI3K/Akt pathway, suggesting that abnormal proliferation and differentiation could be critical pathogenic contributors in NTDs induced by MRFHRV. These results were further validated by CCK8 assay in mouse embryonic stem cells and GFAP staining in embryonic brain tissue. This study indicated that chemotherapeutic and antiepileptic agents induced NTDs might through predicted targets TP53, MAPK1, GRB2, HDAC1, EGFR, PIK3CA, RXRA, and FYN and multiple signaling pathways. More caution was required for the clinical administration for women with childbearing potential and pregnant.

In-vitro differentiation of human embryonic stem cells into spinal cord neural stem cells

In-vitro differentiation of human embryonic stem cells into spinal cord neural stem cells (NSCs) can help researchers better understand the cellular processes associated with spinal cord development and regeneration, and provide therapeutic strategies for spinal cord disorders. However, effective and consistent methods for the generation of human spinal cord NSCs are rare. Objective of the study is to establish methods for the in-vitro induction and long-term maintenance of human spinal cord NSCs. H9 cells were treated with neural induction medium for 10 days under single-cell seeding condition, followed by treatment with neural maintenance medium and replacement with NSC medium after five passages. The identity of the generated cells was determined by immunofluorescence, immunoblotting, and cleavage under targets and tagmentation (CUT&Tag) assays. After the neural induction, OCT4, an embryonic stem cell marker, was significantly reduced, whereas NESTIN and PAX6, two NSC markers, were clearly increased. After the neural maintenance, most of the H9-derived cells consistently expressed NESTIN and PAX6 together with SOX1 and HOXC9, two spinal cord markers. The Homer known motif enrichment results of the CUT&Tag assay confirmed the expression of HOXC9 in the H9-derived spinal cord NSCs, which can be maintained for more than 40 days under an in vitro culture system. This study sheds new light on effective induction and maintenance of human spinal cord NSCs.

A Microfluidic Eye Facsimile System to Examine the Migration of Stem-like Cells

Millions of adults are affected by progressive vision loss worldwide. The rising incidence of retinal diseases can be attributed to damage or degeneration of neurons that convert light into electrical signals for vision. Contemporary cell replacement therapies have transplanted stem and progenitor-like cells (SCs) into adult retinal tissue to replace damaged neurons and restore the visual neural network. However, the inability of SCs to migrate to targeted areas remains a fundamental challenge. Current bioengineering projects aim to integrate microfluidic technologies with organotypic cultures to examine SC behaviors within biomimetic environments. The application of neural phantoms, or eye facsimiles, in such systems will greatly aid the study of SC migratory behaviors in 3D. This project developed a bioengineering system, called the μ-Eye, to stimulate and examine the migration of retinal SCs within eye facsimiles using external chemical and electrical stimuli. Results illustrate that the imposed fields stimulated large, directional SC migration into eye facsimiles, and that electro-chemotactic stimuli produced significantly larger increases in cell migration than the individual stimuli combined. These findings highlight the significance of microfluidic systems in the development of approaches that apply external fields for neural repair and promote migration-targeted strategies for retinal cell replacement therapy.