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Major signaling pathways known to be involved in Schwann cell development. (Left): drawings schematically depict the major stages of Schwann cell (SC) development: neural crest (NC) formation, neural crest cell migration, Schwann cell precursor formation, and Schwann cell differentiation and maturation (from top to bottom). (Middle): color gradients indicate the developmental phases in which the indicated signaling pathways are known to be important. (Right): lists of some of the molecules frequently used for in vitro differentiation, assigned to the neural crest induction phase and Schwann cell specification phase. Color codes of the individual molecules in the right part match the corresponding activated pathways depicted in the middle.
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Schwann cells are glial cells of the peripheral nervous system. They exist in several subtypes and perform a variety of functions in nerves. Their derivation and culture in vitro are interesting for applications ranging from disease modeling to tissue engineering. Since primary human Schwann cells are challenging to obtain in large quantities, in v...
Citations
... Schwann cell differentiation protocols are following this trajectory and have gone through several iterations. 36,37 We have developed a Schwann cell differentiation protocol that is efficient and reproducible. 5 The resulting cells exhibit molecular, morphological, and functional characteristics of Schwann cells. ...
... Unfortunately, current Schwann cell differentiation protocols, including our own, are either unable to myelinate or very inefficiently myelinate neurons in vitro. 5,37,41 It may be worth exploring functional differences in hESC-and hiPSC-derived Schwann cells caused by gene expression changes like cell proliferation, migration and elongation. We would also like to note that differentiation protocols requiring FACS sorting introduce multiple variables into the process of differentiation Schwann cells. ...
... A34964). Six-well plates were coated with 0.1% gelatin in water (StemCell Technologies, 07903) and incubated at37 C for 30 minutes prior to seeding approximately 300,000 MEFs per well in MEF medium (DMEM [Thermo Fisher Scientific, 11965092] supplemented with 10% FBS [Thermo Fisher Scientific, 26140095]). MEFs were cultured in 5% CO 2 at 37 C overnight before seeding stem cells. ...
... At embryonic day 12-13, neural crest cells give rise to Schwann cell precursors (SCPs), which closely resemble neural crest stem cells (NCSCs), but also exhibit features characteristic of immature SCs [66,67]. Subsequently, SCPs further differentiate into immature SCs at embryonic day 13-15 [68]. Postnatally, immature SCs bifurcate along either myelinating or non-myelinating trajectories, depending on the diameter of contacting axons [68]. ...
... Subsequently, SCPs further differentiate into immature SCs at embryonic day 13-15 [68]. Postnatally, immature SCs bifurcate along either myelinating or non-myelinating trajectories, depending on the diameter of contacting axons [68]. Immature SCs with a small SC-to-axon ratio differentiate into mature non-myelinating SCs (nmSCs), while immature SCs with a large SC-to-axon ratio become mature myelinating SCs (mSCs) [69]. ...
Simple Summary
In this review, we explore how interactions between tumorigenic Schwann cells and infiltrating immune cells shape the development and malignant transformation of peripheral nerve sheath tumors in neurofibromatosis type 1. We summarize the current state of the field and address key knowledge gaps surrounding the impact of neurofibromin haploinsufficiency on immune cell function, as well as the impact of Schwann cell lineage states on immune cell recruitment and activation within the tumor microenvironment. Furthermore, we discuss emerging evidence suggesting a dueling role of the immune system in promoting benign tumor initiation while potentially restraining malignant outgrowth. Finally, we highlight the potential implications of these findings and suggest future directions for research relevant to the diagnosis, risk-assessment, and treatment of peripheral nerve sheath tumors, utilizing immunomodulatory therapeutics.
Abstract
Neurofibromatosis type 1 (NF1) is a common genetic disorder resulting in the development of both benign and malignant tumors of the peripheral nervous system. NF1 is caused by germline pathogenic variants or deletions of the NF1 tumor suppressor gene, which encodes the protein neurofibromin that functions as negative regulator of p21 RAS. Loss of NF1 heterozygosity in Schwann cells (SCs), the cells of origin for these nerve sheath-derived tumors, leads to the formation of plexiform neurofibromas (PNF)—benign yet complex neoplasms involving multiple nerve fascicles and comprised of a myriad of infiltrating stromal and immune cells. PNF development and progression are shaped by dynamic interactions between SCs and immune cells, including mast cells, macrophages, and T cells. In this review, we explore the current state of the field and critical knowledge gaps regarding the role of NF1(Nf1) haploinsufficiency on immune cell function, as well as the putative impact of Schwann cell lineage states on immune cell recruitment and function within the tumor field. Furthermore, we review emerging evidence suggesting a dueling role of Nf1+/- immune cells along the neurofibroma to MPNST continuum, on one hand propitiating PNF initiation, while on the other, potentially impeding the malignant transformation of plexiform and atypical neurofibroma precursor lesions. Finally, we underscore the potential implications of these discoveries and advocate for further research directed at illuminating the contributions of various immune cells subsets in discrete stages of tumor initiation, progression, and malignant transformation to facilitate the discovery and translation of innovative diagnostic and therapeutic approaches to transform risk-adapted care.
... The distinction between the beneficial and pathological actions of the different phenotypes of SCs appears to be related to the EVs they produce, and more specifically, the microRNA cargos these SCEVs carry. Recent investigations have shown that distinct phenotypes of SCs release EVs with unique cargos that confer neuroprotection, are proreparative, or which influence axonal conduction and synaptic transmission [62,130,131,143] or play a role in axon myelination [158], or, conversely, trigger the development of peripheral neuropathies [159,160]. ...
Exosomes are nanoscale-sized membrane vesicles released by cells into their extracellular milieu. Within these nanovesicles reside a multitude of bioactive molecules, which orchestrate essential biological processes, including cell differentiation, proliferation, and survival, in the recipient cells. These bioactive properties of exosomes render them a promising choice for therapeutic use in the realm of tissue regeneration and repair. Exosomes possess notable positive attributes, including a high bioavailability, inherent safety, and stability, as well as the capacity to be functionalized so that drugs or biological agents can be encapsulated within them or to have their surface modified with ligands and receptors to imbue them with selective cell or tissue targeting. Remarkably, their small size and capacity for receptor-mediated transcytosis enable exosomes to cross the blood–brain barrier (BBB) and access the central nervous system (CNS). Unlike cell-based therapies, exosomes present fewer ethical constraints in their collection and direct use as a therapeutic approach in the human body. These advantageous qualities underscore the vast potential of exosomes as a treatment option for neurological injuries and diseases, setting them apart from other cell-based biological agents. Considering the therapeutic potential of exosomes, the current review seeks to specifically examine an area of investigation that encompasses the development of Schwann cell (SC)-derived exosomal vesicles (SCEVs) as an approach to spinal cord injury (SCI) protection and repair. SCs, the myelinating glia of the peripheral nervous system, have a long history of demonstrated benefit in repair of the injured spinal cord and peripheral nerves when transplanted, including their recent advancement to clinical investigations for feasibility and safety in humans. This review delves into the potential of utilizing SCEVs as a therapy for SCI, explores promising engineering strategies to customize SCEVs for specific actions, and examines how SCEVs may offer unique clinical advantages over SC transplantation for repair of the injured spinal cord.
... Myelin improves conduction velocity by restricting the regions of ionic transfer along the axon to the nodes of Ranvier, resulting in faster propagation of the action potential, called saltatory conduction [3,4]. Schwann cells play a significant role in promoting axonal regeneration as they are a major source of neurotrophic factors that normally interact with tyrosine kinase receptors to alter the gene expression profile of the neuron to promote regeneration [5,6]. NGF has a low level of expression in healthy nerves, but is activated in Schwann cells under injury. ...
Introduction: Peripheral nerve injuries are common conditions with a broad spectrum of symptoms depending on the severity and nerves involved. Although a large amount of knowledge about the mechanisms of damage and regeneration has been accumulated, but the number of reliable methods of treatment that ensure full functional recovery is not enough. Materials and Methods: The study included 93 men aged 21 to 59 years with neuropathies and plexopathies, which were divided into 3 groups. All patients underwent neurological, electroneuromyographic, and ultrasound examination. Immunological research was carried out during 12 to 24 months after the onset of the disease. Results: In our study, we found a statistically significant correlation between the content of Beta-NGF and the level of peripheral blood eosinophils (R=0.41, p=0.0191) in patients with post-traumatic gunshot neuropathies and plexopathies. A correlation between the content of Beta-NGF and the CD2+ indicator levels (R=0.56, p=0.00105) in patients with post-traumatic non-gunshot neuropathies and plexopathies was revealed. Conclusion: The analysis of the received research data and literature resources demonstrates an important correlation between the neurotrophins and immunological indicators, which opens up further promising opportunities in the development and use of complex pathogenetic therapy of post-traumatic neuropathies and plexopathies in order to improve the restoration of impaired functions and the quality of life of patients.
The differentiation of bone marrow stromal cells (BMSCs) into Schwann‐like cells (SCLCs) has the potential to promote the structural and functional restoration of injured axons. However, the optimal induction protocol and its underlying mechanisms remain unclear. This study aimed to compare the effectiveness of different induction protocols in promoting the differentiation of rat BMSCs into SCLCs and to explore their potential mechanisms. BMSCs were induced using two distinct methods: a composite factor induction approach (Protocol‐1) and a conditioned culture medium induction approach (Protocol‐2). The expression of Schwann cells (SCs) marker proteins and neurotrophic factors (NTFs) in the differentiated cells was assessed. Cell proliferation and apoptosis were also measured. During induction, changes in miR‐21 and Sprouty RTK signaling antagonist 2 (SPRY2) mRNA were analyzed. Following the transfection of BMSCs with miR‐21 agomir or miR‐21 antagomir, induction was carried out using both protocols, and the expression of SPRY2, ERK1/2, and SCs marker proteins was examined. The results revealed that NTFs expression was higher in Protocol‐1, whereas SCs marker proteins expression did not significantly differ between the two groups. Compared to Protocol‐1, Protocol‐2 exhibited enhanced cell proliferation and fewer apoptotic and necrotic cells. Both protocols showed a negative correlation between miR‐21 and SPRY2 expression throughout the induction stages. After induction, the miR‐21 agomir group exhibited reduced SPRY2 expression, increased ERK1/2 expression, and significantly elevated expression of SCs marker proteins. This study demonstrates that Protocol‐1 yields higher NTFs expression, whereas Protocol‐2 results in stronger SCLCs proliferation. Upregulating miR‐21 suppresses SPRY2 expression, activates the ERK1/2 signaling pathway, and promotes BMSC differentiation into SCLCs.
After peripheral nervous system injury, Schwann cells (SCs) can repair axons by providing a growth‐promoting microenvironment. The aim of this study is to explore the effects and mechanisms of LKB1 and CRMP1 on the repair of sciatic nerve injury (SNI). The expressions of LKB1 and CRMP1 were changed in rats with SNI from 12 h to 4 weeks by hematoxylin–eosin staining, RT‐PCR assay, immunohistochemical staining, and western blotting. Immunofluorescence results show that LKB1 and CRMP1 are co‐localized in the regenerated axons of the sciatic nerve tissue of SNI rats. Co‐immunoprecipitation indicates that LKB1 interacts with CRMP1. LKB1 interference suppresses the phosphorylation level of CRMP1. Overexpression of LKB1 and CRMP1 promotes the invasion and migration of SCs, and nerve cell protuberance extends. The structure of the myelin sheath in the sciatic nerve of the model group was found to be loose and disordered. Rats in the model group had higher pain thresholds and heat sensitivity response times than those in the control group. Nerve conduction velocity, the latency of action potential, and the peak value of compound muscle action potential in the SNI group were significantly lower than those in the control group, and the muscle atrophy was severe. Overexpression of LKB1 may significantly improve the above conditions. However, the function of LKB1 to improve SNI is abolished by the interference of CRMP1. In summary, the interaction between LKB1 and CRMP promotes the migration and differentiation of SCs and the extension of neurons, thereby improving the repair of nerve injury.
Schwann cells (SCs) have a critical role in the peripheral nervous system. These cells are able to support axons during homeostasis and after injury. However, mutations in genes associated with the SCs repair program or myelination result in dysfunctional SCs. Several neuropathies such as Charcot–Marie–Tooth (CMT) disease, diabetic neuropathy and Guillain–Barré syndrome show abnormal SC functions and an impaired regeneration process. Thus, understanding SCs-axon interaction and the nerve environment in the context of homeostasis as well as post-injury and disease onset is necessary. Several neurotrophic factors, cytokines, and regulators of signaling pathways associated with proliferation, survival and regeneration are involved in this process. Preclinical studies have focused on the discovery of therapeutic targets for peripheral neuropathies and injuries. To study the effect of new therapeutic targets, modeling neuropathies and peripheral nerve injuries (PNIs) in vitro and in vivo are useful tools. Furthermore, several in vitro protocols have been designed using SCs and neuron cell lines to evaluate these targets in the regeneration process. SCs lines have been used to generate effective myelinating SCs without success. Alternative options have been investigated using direct conversion from somatic cells to SCs or SCs derived from pluripotent stem cells to generate functional SCs. This review will go over the advantages of these systems and the problems associated with them. In addition, there have been challenges in establishing adequate and reproducible protocols in vitro to recapitulate repair SC-neuron interactions observed in vivo . So, we also discuss the mechanisms of repair SCs-axon interactions in the context of peripheral neuropathies and nerve injury (PNI) in vitro and in vivo . Finally, we summarize current preclinical studies evaluating transgenes, drug, and novel compounds with translational potential into clinical studies.
In this issue, Majd et al.¹ derive Schwann cells from human pluripotent stem cells (hPSCs), which can be used to study Schwann cell development and physiology and model diabetic neuropathy. hPSC-derived Schwann cells possess the molecular features of primary Schwann cells and are capable of myelination in vitro and in vivo.
Adult human Schwann cells represent a relevant tool for studying peripheral neuropathies and developing regenerative therapies to treat nerve damage. Primary adult human Schwann cells are, however, difficult to obtain and challenging to propagate in culture. One potential solution is to generate Schwann cells from human induced pluripotent stem cells (hiPSCs). Previously published protocols, however, in our hands did not deliver sufficient viable cell numbers of hiPSC-derived Schwann cells (hiPSC-SCs). We present here, two modified protocols from two collaborating laboratories that overcome these challenges. With this, we also identified the relevant parameters to be specifically considered in any proposed differentiation protocol. Furthermore, we are, to our knowledge, the first to directly compare hiPSC-SCs to primary adult human Schwann cells using immunocytochemistry and RT-qPCR. We conclude the type of coating to be important during the differentiation process from Schwann cell precursor cells or immature Schwann cells to definitive Schwann cells, as well as the amounts of glucose in the specific differentiation medium to be crucial for increasing its efficiency and the final yield of viable hiPSC-SCs. Our hiPSC-SCs further displayed high similarity to primary adult human Schwann cells.
