Zeb2 is essential for Schwann cell differentiation, myelination and nerve repair

Ultrasound-responsive microfibers promoted infected wound healing with neuro-vascularization by segmented sonodynamic therapy and electrical stimulation

Bacteria-infected wounds pose challenges to healing due to persistent infection and associated damage to nerves and vessels. Although sonodynamic therapy can help kill bacteria, it is limited by the residual oxidative stress, resulting in prolonged inflammation. To tackle these barriers, novel 4 octyl itaconate-coated Li-doped ZnO/PLLA piezoelectric composite microfibers are developed, offering a whole-course "targeted" treatment under ultrasound therapy. The inclusion of Li atoms causes the ZnO lattice distortion and increases the band gap, enhancing the piezoelectric and sonocatalytic properties of the composite microfibers, collaborated by an aligned PLLA conformation design. During the infection and inflammation stages, the piezoelectric microfibers exhibit spatiotemporal-dependent therapeutic effects, swiftly eliminating over 94.2 % of S. aureus within 15 min under sonodynamic therapy. Following this phase, the microfibers capture reactive oxygen species and aid macrophage reprogramming, restoring mitochondrial function, achieving homeostasis, and shortening inflammation cycles. As the wound progresses through the healing stages, bioactive Zn2+ and Li + ions are continuously released, improving cell recruitment, and the piezoelectrical stimulation enhances wound recovery with neuro-vascularization. Compared to commercially available dressings, our microfibers accelerate the closure of rat wounds (Φ = 15 mm) without scarring in 12 days. Overall, this "one stone, four birds" wound management strategy presents a promising avenue for infected wound therapy.

Genes in Axonal Regeneration

This review explores the molecular and genetic underpinnings of axonal regeneration and functional recovery post-nerve injury, emphasizing its significance in reversing neurological deficits. It presents a systematic exploration of the roles of various genes in axonal regrowth across peripheral and central nerve injuries. Initially, it highlights genes and gene families critical for axonal growth and guidance, delving into their roles in regeneration. It then examines the regenerative microenvironment, focusing on the role of glial cells in neural repair through dedifferentiation, proliferation, and migration. The concept of "traumatic microenvironments" within the central nervous system (CNS) and peripheral nervous system (PNS) is discussed, noting their impact on regenerative capacities and their importance in therapeutic strategy development. Additionally, the review delves into axonal transport mechanisms essential for accurate growth and reinnervation, integrating insights from proteomics, genome-wide screenings, and gene editing advancements. Conclusively, it synthesizes these insights to offer a comprehensive understanding of axonal regeneration's molecular orchestration, aiming to inform effective nerve injury therapies and contribute to regenerative neuroscience.

Schwann Cell Development and Myelination

Glial cells in the peripheral nervous system (PNS), which arise from the neural crest, include axon-associated Schwann cells (SCs) in nerves, synapse-associated SCs at the neuromuscular junction, enteric glia, perikaryon-associated satellite cells in ganglia, and boundary cap cells at the border between the central nervous system (CNS) and the PNS. Here, we focus on axon-associated SCs. These SCs progress through a series of formative stages, which culminate in the generation of myelinating SCs that wrap large-caliber axons and of nonmyelinating (Remak) SCs that enclose multiple, small-caliber axons. In this work, we describe SC development, extrinsic signals from the axon and extracellular matrix (ECM) and the intracellular signaling pathways they activate that regulate SC development, and the morphogenesis and organization of myelinating SCs and the myelin sheath. We review the impact of SCs on the biology and integrity of axons and their emerging role in regulating peripheral nerve architecture. Finally, we explain how transcription and epigenetic factors control and fine-tune SC development and myelination.

Myelinated peripheral axons are more vulnerable to mechanical trauma in a model of enlarged axonal diameters

The velocity of axonal impulse propagation is facilitated by myelination and axonal diameters. Both parameters are frequently impaired in peripheral nerve disorders, but it is not known if the diameters of myelinated axons affect the liability to injury or the efficiency of functional recovery. Mice lacking the adaxonal myelin protein chemokine-like factor-like MARVEL-transmembrane domain-containing family member-6 (CMTM6) specifically from Schwann cells (SCs) display appropriate myelination but increased diameters of peripheral axons. Here we subjected Cmtm6-cKo mice as a model of enlarged axonal diameters to a mild sciatic nerve compression injury that causes temporarily reduced axonal diameters but otherwise comparatively moderate pathology of the axon/myelin-unit. Notably, both of these pathological features were worsened in Cmtm6-cKo compared to genotype-control mice early post-injury. The increase of axonal diameters caused by CMTM6-deficiency thus does not override their injury-dependent decrease. Accordingly, we did not detect signs of improved regeneration or functional recovery after nerve compression in Cmtm6-cKo mice; depleting CMTM6 in SCs is thus not a promising strategy toward enhanced recovery after nerve injury. Conversely, the exacerbated axonal damage in Cmtm6-cKo nerves early post-injury coincided with both enhanced immune response including foamy macrophages and SCs and transiently reduced grip strength. Our observations support the concept that larger peripheral axons are particularly susceptible toward mechanical trauma.

Sox10 Activity and the Timing of Schwann Cell Differentiation Are Controlled by a Tle4-Dependent Negative Feedback Loop

The HMG-domain containing transcription factor Sox10 plays a crucial role in regulating Schwann cell survival and differentiation and is expressed throughout the entire Schwann cell lineage. While its importance in peripheral myelination is well established, little is known about its role in the early stages of Schwann cell development. In a search for direct target genes of Sox10 in Schwann cell precursors, the transcriptional co-repressor Tle4 was identified. At least two regions upstream of the Tle4 gene appear involved in mediating the Sox10-dependent activation. Once induced, Tle4 works in tandem with the bHLH transcriptional repressor Hes1 and exerts a dual inhibitory effect on Sox10 by preventing the Sox10 protein from transcriptionally activating maturation genes and by suppressing Sox10 expression through known enhancers of the gene. This mechanism establishes a regulatory barrier that prevents premature activation of factors involved in differentiation and myelin formation by Sox10 in immature Schwann cells. The identification of Tle4 as a critical downstream target of Sox10 sheds light on the gene regulatory network in the early phases of Schwann cell development. It unravels an elaborate regulatory circuitry that fine-tunes the timing and extent of Schwann cell differentiation and myelin gene expression.

Neddylation orchestrates the complex transcriptional and posttranscriptional program that drives Schwann cell myelination

Myelination is essential for neuronal function and health. In peripheral nerves, >100 causative mutations have been identified that cause Charcot-Marie-Tooth disease, a disorder that can affect myelin sheaths. Among these, a number of mutations are related to essential targets of the posttranslational modification neddylation, although how these lead to myelin defects is unclear. Here, we demonstrate that inhibiting neddylation leads to a notable absence of peripheral myelin and axonal loss both in developing and regenerating mouse nerves. Our data indicate that neddylation exerts a global influence on the complex transcriptional and posttranscriptional program by simultaneously regulating the expression and function of multiple essential myelination signals, including the master transcription factor EGR2 and the negative regulators c-Jun and Sox2, and inducing global secondary changes in downstream pathways, including the mTOR and YAP/TAZ signaling pathways. This places neddylation as a critical regulator of myelination and delineates the potential pathogenic mechanisms involved in CMT mutations related to neddylation.

Skin derived precursors induced Schwann cells mediated tissue engineering-aided neuroregeneration across sciatic nerve defect

A central question in neural tissue engineering is how the tissue-engineered nerve (TEN) translates detailed transcriptional signals associated with peripheral nerve regeneration into meaningful biological processes. Here, we report a skin-derived precursor-induced Schwann cell (SKP-SC)-mediated chitosan/silk fibroin-fabricated tissue-engineered nerve graft (SKP-SCs-TEN) that can promote sciatic nerve regeneration and functional restoration nearly to the levels achieved by autologous nerve grafts according to behavioral, histological, and electrophysiological evidence. For achieving better effect of neuroregeneration, this is the first time to jointly apply a dynamic perfusion bioreactor and the ascorbic acid to stimulate the SKP-SCs secretion of extracellular matrix (ECM). To overcome the limitation of traditional tissue-engineered nerve grafts, jointly utilizing SKP-SCs and their ECM components were motivated by the thought of prolongating the effect of support cells and their bioactive cues that promote peripheral nerve regeneration. To further explore the regulatory model of gene expression and the related molecular mechanisms involved in tissue engineering-aided peripheral nerve regeneration, we performed a cDNA microarray analysis of gene expression profiling, a comprehensive bioinformatics analysis and a validation study on the grafted segments and dorsal root ganglia tissues. A wealth of transcriptomic and bioinformatics data has revealed complex molecular networks and orchestrated functional regulation that may be responsible for the effects of SKP-SCs-TEN on promoting peripheral nerve regeneration. Our work provides new insights into transcriptomic features and patterns of molecular regulation in nerve functional recovery aided by SKP-SCs-TEN that sheds light on the broader possibilities for novel repair strategies of peripheral nerve injury.

Dihydromyricetin reverses capecitabine-induced peripheral myelin dysfunction through modulation of oxidative stress

Previous clinical reports have shown that capecitabine, an oral prodrug of 5-fluorouracil (5-Fu), can induce peripheral neuropathy, resulting in numbness, paresthesia and hypoesthesia. However, the mechanism through which capecitabine causes peripheral nerve injury remains unclear. Here, we demonstrate that systemic administration of capecitabine leads to myelin abnormalities in the peripheral nerves of mice, which are possibly attributed to the death of Schwann cells, the myelinating cells in the peripheral nervous system. Furthermore, our results show that 5-Fu induces significant oxidative stress in Schwann cells by inhibiting the expression of the anti-oxidative protein DJ-1, leading to a decrease in Schwann cell markers. We found that the anti-oxidant dihydromyricetin (DMY) reverses 5-Fu-induced Schwann cell death and oxidative stress and alleviates capecitabine-induced myelin abnormalities. Taken together, our data indicate that capecitabine induces peripheral myelin dysfunction by regulating DJ-1-mediated oxidative stress in Schwann cells and reveal DMY as a potential therapeutic strategy for capecitabine-induced peripheral neuropathy.

Mowat-Wilson syndrome factor ZEB2 controls early formation of human neural crest through BMP signaling modulation

Mowat-Wilson syndrome is caused by mutations in ZEB2, with patients exhibiting characteristics indicative of neural crest (NC) defects. We examined the contribution of ZEB2 to human NC formation using a model based on human embryonic stem cells. We found ZEB2 to be one of the earliest factors expressed in prospective human NC, and knockdown revealed a role for ZEB2 in establishing the NC state while repressing pre-placodal and non-neural ectoderm genes. Examination of ZEB2 N-terminal mutant NC cells demonstrates its requirement for the repression of enhancers in the NC gene network and proper NC cell terminal differentiation into osteoblasts and peripheral neurons and neuroglia. This ZEB2 mutation causes early misexpression of BMP signaling ligands, which can be rescued by the attenuation of BMP. Our findings suggest that ZEB2 regulates early human NC specification by modulating proper BMP signaling and further elaborate the molecular defects underlying Mowat-Wilson syndrome.

The transcription factor Stat-1 is essential for Schwann cell differentiation, myelination and myelin sheath regeneration

BACKGROUND

Myelin sheath is a crucial accessory to the functional nerve-fiber unit, its disruption or loss can lead to axonal degeneration and subsequent neurodegenerative diseases (NDs). Notwithstanding of substantial progress in possible molecular mechanisms underlying myelination, there is no therapeutics that prevent demyelination in NDs. Therefore, it is crucial to seek for potential intervention targets. Here, we focused on the transcriptional factor, signal transducer and activator of transcription 1 (Stat1), to explore its effects on myelination and its potential as a drug target.

METHODS

By analyzing the transcriptome data obtained from Schwann cells (SCs) at different stages of myelination, it was found that Stat1 might be involved in myelination. To test this, we used the following experiments: (1) In vivo, the effect of Stat1 on remyelination was observed in an in vivo myelination mode with Stat1 knockdown in sciatic nerves or specific knockdown in SCs. (2) In vitro, the RNA interference combined with cell proliferation assay, scratch assay, SC aggregate sphere migration assay, and a SC differentiation model, were used to assess the effects of Stat1 on SC proliferation, migration and differentiation. Chromatin immunoprecipitation sequencing (ChIP-Seq), RNA-Seq, ChIP-qPCR and luciferase activity reporter assay were performed to investigate the possible mechanisms of Stat1 regulating myelination.

RESULTS

Stat1 is important for myelination. Stat1 knockdown in nerve or in SCs reduces the axonal remyelination in the injured sciatic nerve of rats. Deletion of Stat1 in SCs blocks SC differentiation thereby inhibiting the myelination program. Stat1 interacts with the promoter of Rab11-family interacting protein 1 (Rab11fip1) to initiate SC differentiation.

CONCLUSION

Our findings demonstrate that Stat1 regulates SC differentiation to control myelinogenic programs and repair, uncover a novel function of Stat1, providing a candidate molecule for clinical intervention in demyelinating diseases.

Modulation of Schwann cell homeostasis by the BAP1 deubiquitinase

Schwann cell programming during myelination involves transcriptional networks that activate gene expression but also repress genes that are active in neural crest/embryonic differentiation of Schwann cells. We previously found that a Schwann cell-specific deletion of the EED subunit of the Polycomb Repressive Complex (PRC2) led to inappropriate activation of many such genes. Moreover, some of these genes become re-activated in the pro-regenerative response of Schwann cells to nerve injury, and we found premature activation of the nerve injury program in a Schwann cell-specific knockout of Eed. Polycomb-associated histone modifications include H3K27 trimethylation formed by PRC2 and H2AK119 monoubiquitination (H2AK119ub1), deposited by Polycomb repressive complex 1 (PRC1). We recently found dynamic regulation of H2AK119ub1 in Schwann cell genes after injury. Therefore, we hypothesized that H2AK119 deubiquitination modulates the dynamic polycomb repression of genes involved in Schwann cell maturation. To determine the role of H2AK119 deubiquitination, we generated a Schwann cell-specific knockout of the H2AK119 deubiquitinase Bap1 (BRCA1-associated protein). We found that loss of Bap1 causes tomacula formation, decreased axon diameters and eventual loss of myelinated axons. The gene expression changes are accompanied by redistribution of H2AK119ub1 and H3K27me3 modifications to extragenic sites throughout the genome. BAP1 interacts with OGT in the PR-DUB complex, and our data suggest that the PR-DUB complex plays a multifunctional role in repression of the injury program. Overall, our results indicate Bap1 is required to restrict the spread of polycomb-associated histone modifications in Schwann cells and to promote myelin homeostasis in peripheral nerve.

Effects of Curcumin on Axon Growth and Myelin Sheath Formation in an In Vitro Model

Although the beneficial effects of curcumin, extracted from rhizomes of the ginger family genus Curcuma, on the repair and regeneration of nerves have been evaluated in vitro, there are few studies concerning its effects on axon myelination. Here, we used pheochromocytoma cells as an in vitro model of peripheral nerves. Pheochromocytoma cells were cultured alone or cocultured with Schwann cells and treated with increasing concentrations of curcumin. Cell growth was observed, and the expression levels of growth-associated protein 43 (GAP-43), microtubule-associated protein 2 (MAP-2), myelin basic protein (MBP), myelin protein zero (MPZ), Krox-20, and octamer binding factor 6 (Oct-6) were quantified. We found a significant increase in expression of all six proteins following curcumin treatment, with a corresponding increase in the levels of MBP, MPZ, Krox-20, and Oct-6 mRNA. Upregulation was greater with increasing curcumin concentration, showing a concentration-dependent effect. The results suggested that curcumin can promote the growth of axons by upregulating the expression of GAP-43 and MAP-2, stimulate synthesis and secretion of myelin-related proteins, and facilitate formation of the myelin sheath in axons by upregulating the expression of Krox-20 and Oct-6. Therefore, curcumin could be widely applied in future strategies for the treatment of nerve injuries.

Evaluation of the Aging Effect on Peripheral Nerve Regeneration: A Systematic Review

INTRODUCTION

Peripheral nerve injuries have been associated with increased healthcare costs and decreased patients' quality of life. Aging represents one factor that slows the speed of peripheral nervous system (PNS) regeneration. Since cellular homeostasis imbalance associated with aging lead to an increased failure in nerve regeneration in mammals of advanced age, this systematic review aims to determine the main molecular and cellular mechanisms involved in peripheral nerve regeneration in aged murine models after a peripheral nerve injuries.

METHODS

Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, a literature search of 4 databases was conducted in July 2022 for studies comparing the peripheral nerve regeneration capability between young and aged murine models.

RESULTS

After the initial search yielded 744 publications, ten articles fulfilled the inclusion criteria. These studies show that age-related changes such as chronic inflammatory state, delayed macrophages' response to injury, dysfunctional Schwann Cells (SCs), and microenvironment alterations cause a reduction in the regenerative capability of the PNS in murine models. Furthermore, identifying altered gene expression patterns of SC after nerve damage can contribute to the understanding of physiological modifications produced by aging.

CONCLUSIONS

The interaction between macrophages and SC plays a crucial role in the nerve regeneration of aged models. Therefore, studies aimed at developing new and promising therapies for nerve regeneration should focus on these cellular groups to enhance the regenerative capabilities of the PNS in elderly populations.

Hypoxic culture of umbilical cord mesenchymal stem cell-derived sEVs prompts peripheral nerve injury repair

Introduction

Repair and regeneration of the peripheral nerve are important for the treatment of peripheral nerve injury (PNI) caused by mechanical tears, external compression injuries and traction injuries. Pharmacological treatment can promote the proliferation of fibroblasts and Schwann cells (SCs), which longitudinally fill the endoneurial canal and form Bungner’s band, helping the repair of peripheral nerves. Therefore, the development of new drugs for the treatment of PNI has become a top priority in recent years.

Methods

Here, we report that small extracellular vesicles (sEVs) produced from umbilical cord mesenchymal stem cells (MSC-sEVs) cultured under hypoxia promote repair and regeneration of the peripheral nerve in PNI and may be a new therapeutic drug candidate.

Results

The results showed that the amount of secreted sEVs was significantly increased in UC-MSCs compared with control cells after 48 h of culture at 3% oxygen partial pressure in a serum-free culture system. The identified MSC-sEVs could be taken up by SCs in vitro, promoting the growth and migration of SCs. In a spared nerve injury (SNI) mouse model, MSC-sEVs accelerated the recruitment of SCs at the site of PNI and promoted peripheral nerve repair and regeneration. Notably, repair and regeneration in the SNI mouse model were enhanced by treatment with hypoxic cultured UC-MSC-derived sEVs.

Discussion

Therefore, we conclude that hypoxic cultured UC-MSC-derived sEVs may be a promising candidate drug for repair and regeneration in PNI.

Zeb2 DNA-Binding Sites in Neuroprogenitor Cells Reveal Autoregulation and Affirm Neurodevelopmental Defects, Including in Mowat-Wilson Syndrome

Functional perturbation and action mechanism studies have shown that the transcription factor Zeb2 controls cell fate decisions, differentiation, and/or maturation in multiple cell lineages in embryos and after birth. In cultured embryonic stem cells (ESCs), Zeb2’s mRNA/protein upregulation is necessary for the exit from primed pluripotency and for entering general and neural differentiation. We edited mouse ESCs to produce Flag-V5 epitope-tagged Zeb2 protein from one endogenous allele. Using chromatin immunoprecipitation coupled with sequencing (ChIP-seq), we mapped 2432 DNA-binding sites for this tagged Zeb2 in ESC-derived neuroprogenitor cells (NPCs). A new, major binding site maps promoter-proximal to Zeb2 itself. The homozygous deletion of this site demonstrates that autoregulation of Zeb2 is necessary to elicit the appropriate Zeb2-dependent effects in ESC-to-NPC differentiation. We have also cross-referenced all the mapped Zeb2 binding sites with previously obtained transcriptome data from Zeb2 perturbations in ESC-derived NPCs, GABAergic interneurons from the ventral forebrain of mouse embryos, and stem/progenitor cells from the post-natal ventricular-subventricular zone (V-SVZ) in mouse forebrain, respectively. Despite the different characteristics of each of these neurogenic systems, we found interesting target gene overlaps. In addition, our study also contributes to explaining developmental disorders, including Mowat-Wilson syndrome caused by ZEB2 deficiency, and also other monogenic syndromes.

Stepwise fate conversion of supporting cells to sensory hair cells in the chick auditory epithelium

In contrast to mammals, the avian cochlea, specifically the basilar papilla, can regenerate sensory hair cells, which involves fate conversion of supporting cells to hair cells. To determine the mechanisms for converting supporting cells to hair cells, we used single-cell RNA sequencing during hair cell regeneration in explant cultures of chick basilar papillae. We identified dynamic changes in the gene expression of supporting cells, and the pseudotime trajectory analysis demonstrated the stepwise fate conversion from supporting cells to hair cells. Initially, supporting cell identity was erased and transition to the precursor state occurred. A subsequent gain in hair cell identity progressed together with downregulation of precursor-state genes. Transforming growth factor β receptor 1-mediated signaling was involved in induction of the initial step, and its inhibition resulted in suppression of hair cell regeneration. Our data provide new insights for understanding fate conversion from supporting cells to hair cells in avian basilar papillae.

Models and methods to study Schwann cells

Schwann cells (SCs) are fundamental components of the peripheral nervous system (PNS) of all vertebrates and play essential roles in development, maintenance, function, and regeneration of peripheral nerves. There are distinct populations of SCs including: (1) myelinating SCs that ensheath axons by a specialized plasma membrane, called myelin, which enhances the conduction of electric impulses; (2) non-myelinating SCs, including Remak SCs, which wrap bundles of multiple axons of small caliber, and perysinaptic SCs (PSCs), associated with motor axon terminals at the neuromuscular junction (NMJ). All types of SCs contribute to PNS regeneration through striking morphological and functional changes in response to nerve injury, are affected in peripheral neuropathies and show abnormalities and a diminished plasticity during aging. Therefore, methodological approaches to study and manipulate SCs in physiological and pathophysiological conditions are crucial to expand the present knowledge on SC biology and to devise new therapeutic strategies to counteract neurodegenerative conditions and age-derived denervation. We present here an updated overview of traditional and emerging methodologies for the study of SCs for scientists approaching this research field.

Transcriptional Control of Peripheral Nerve Regeneration

Transcription factors are master regulators of various cellular processes under diverse physiological and pathological conditions. Many transcription factors that are differentially expressed after injury to peripheral nerves play important roles in nerve regeneration. Considering that rapid and timely regrowth of injured axons is a prerequisite for successful target reinnervation, here, we compile transcription factors that mediates axon elongation, including axon growth suppressor Klf4 and axon growth promoters c-Myc, Sox11, STAT3, Atf3, c-Jun, Smad1, C/EBPδ, and p53. Besides neuronal changes, Schwann cell phenotype modulation is also critical for nerve regeneration. The activation of Schwann cells at early time points post injury provides a permissive microenvironment whereas the re-differentiation of Schwann cells at later time points supports myelin sheath formation. Hence, c-Jun and Sox2, two critical drivers for Schwann cell reprogramming, as well as Krox-20 and Sox10, two essential regulators of Schwann cell myelination, are reviewed. These transcription factors may serve as promising targets for promoting the functional recovery of injured peripheral nerves.

YAP1-TEAD1 mediates the perineural invasion of prostate cancer cells induced by cancer-associated fibroblasts

Perineural invasion (PNI) driven by the tumor microenvironment (TME) has emerged as a key pattern of metastasis of prostate cancer (PCa), while its underlying mechanism is still elusive. Here, we identified increased CAFs and YAP1 expression levels in patients with metastatic PCa. In the cultured PCa cell line LNCaP, co-culture with cancer-associated fibroblasts (CAFs) could upregulate YAP1 protein expression. Either ectopic overexpression of YAP1 or co-culture with CAFs could promote the infiltration of LNCaPs towards dorsal root ganglia (DRG). This effect could be blocked using an YAP1 inhibitor. In vivo, overexpression of YAP1 could increase PNI in a mouse model of sciatic nerve tumor invasion. Mechanistically, TEAD1 binds to the NGF promotor and YAP1/TEAD1 activates its transcription and consequently increases NGF secretion. In turn, PCa cells treated with CM from CAFs or stable YAP1 overexpression can stimulate DRG to secrete CCL2. The epithelial-to-mesenchymal transition (EMT) of PCa cells is thus activated via CCL2/CCR2. Overall, our data demonstrate that CAFs can activate YAP1/TEAD1 signaling and increase the secretion of NGF, therefore promoting PCa PNI. In addition, EMT induced by PNI suggests a feedback loop is present between neurons and PCa cells.

A Glance at the Molecules That Regulate Oligodendrocyte Myelination

Oligodendrocyte (OL) myelination is a critical process for the neuronal axon function in the central nervous system. After demyelination occurs because of pathophysiology, remyelination makes repairs similar to myelination. Proliferation and differentiation are the two main stages in OL myelination, and most factors commonly play converse roles in these two stages, except for a few factors and signaling pathways, such as OLIG2 (Oligodendrocyte transcription factor 2). Moreover, some OL maturation gene mutations induce hypomyelination or hypermyelination without an obvious function in proliferation and differentiation. Herein, three types of factors regulating myelination are reviewed in sequence.

Spindle-Like Zinc Silicate Nanoparticles Accelerating Innervated and Vascularized Skin Burn Wound Healing

The treatment of severe burn injuries is a crucial challenge in skin tissue engineering. Severe burns are always accompanied with large-area neurovascular networks damage, leading to the lack of excitation functions and difficulty in self-healing. Therefore, it is of great importance to develop biomaterials which can not only promote wound healing but also simultaneously reconstruct cutaneous neurovascular networks. In this study, Zn₂ SiO₄ (ZS) nanoparticles-incorporated bioactive nanofibrous scaffolds are designed for innervated and vascularized skin burn wound healing. ZS nanoparticles with spindle-like morphology are synthesized via a facile hydrothermal method. The incorporation of ZS nanoparticles endows the scaffolds with excellent angiogenic and neurogenic activities in vitro. Additionally, in vivo results show that the ZS nanoparticles-incorporated scaffolds have favorable re-epithelialization, innervation, and vascularization abilities through local release of bioactive Zn and Si ions from ZS nanoparticles, leading to rapid wound healing featuring with newly formed blood vessels and nerve fibers. Taken together, this study suggests that the spindle-like ZS nanoparticles are useful bioactive agents for stimulating vascularization and innervation of functional skin repair. The bioactive inorganic nanoparticles may be used for multifunctional tissue regeneration.

Long intergenic non-protein coding RNA 847 promotes laryngeal squamous cell carcinoma progression through the microRNA-181a-5p/zinc finger E-box binding homeobox 2 axis

The present study is targeted at investigating the effects of long intergenic non-protein coding RNA 847 (LINC00847) on the malignant biological behaviors of laryngeal squamous cell carcinoma (LSCC) cells, and the mechanisms. Quantitative real-time PCR and Western blotting were conducted for detecting the expressions of LINC00847, microRNA-181a-5p (miR-181a-5p) and zinc finger E-box binding homeobox 2 (ZEB2) in LSCC cell lines and tissue samples. BrdU, cell counting kit-8, scratch wound healing, Transwell and flow cytometry assays were utilized for detecting cell proliferation, migration, invasion, and cell cycle progression. Dual-luciferase reporter gene, RNA binding protein immunoprecipitation (RIP), and RNA pull-down assays were utilized to investigate the interaction among LINC00847, miR-181a-5p, and ZEB2. The subcellular location of LINC00847 was determined by RNA fluorescence in situ hybridization (RNA-FISH) assay. Tumor growth was evaluated using a xenograft model of nude mice. It was revealed that LINC00847 expression was increased in LSCC tissues, and its high expression was associated with lymph node metastasis and poor differentiation. LINC00847 was mainly located in the cytoplasm of LSCC cells, and LINC00847 overexpression promoted LSCC cell proliferation, migration, invasion, and accelerated the cell cycle progression while knocking down LINC00847 had the opposite effects in vitro and inhibited the tumor growth in vivo. LINC00847 directly targeted miR-181a-5p and negatively modulated miR-181a-5p expression. ZEB2 was a target gene of miR-181a-5p, and was positively and indirectly modulated by LINC00847. Our data suggest that LINC00847 promotes LSCC progression by regulating the miR-181a-5p/ZEB2 axis.

A genetic compensatory mechanism regulated by Jun and Mef2d modulates the expression of distinct class IIa Hdacs to ensure peripheral nerve myelination and repair

The class IIa histone deacetylases (HDACs) have pivotal roles in the development of different tissues. Of this family, Schwann cells express Hdac4, 5, and 7 but not Hdac9. Here, we show that a transcription factor regulated genetic compensatory mechanism within this family of proteins, blocks negative regulators of myelination ensuring peripheral nerve developmental myelination and remyelination after injury. Thus, when Hdac4 and 5 are knocked-out from Schwann cells in mice, a JUN-dependent mechanism induces the compensatory overexpression of Hdac7 permitting, although with a delay, the formation of the myelin sheath. When Hdac4, 5, and 7 are simultaneously removed, the myocyte-specific enhancer-factor d (MEF2D) binds to the promoter and induces the de novo expression of Hdac9, and although several melanocytic lineage genes are misexpressed and Remak bundle structure is disrupted, myelination proceeds after a long delay. Thus, our data unveil a finely tuned compensatory mechanism within the class IIa Hdac family, coordinated by distinct transcription factors, that guarantees the ability of Schwann cells to myelinate during development and remyelinate after nerve injury.

Icariin Ameliorates Alzheimer's Disease Pathology by Alleviating Myelin Injury in 3 × Tg-AD Mice

Alzheimer's disease (AD) is a neurodegenerative disease characterized by excessive deposition of β amyloid (Aβ), hyperphosphorylation of tau protein, and neuronal cell death. Recent studies have shown that myelin cell damage, which leads to cognitive dysfunction, occurs before AD-related pathological changes. Here, we examine the effect of icariin (ICA), a prenylated flavonol glycoside, in improving cognitive function in AD model mice. ICA has been reported to exhibit cardiovascular protective functions and antiaging effects. In this study, we used 3 × Tg-AD mice as an AD model. The Morris water maze and Y maze tests were performed to assess the learning and memory of the mice. Immunofluorescence analysis of Aβ1-42 deposition and myelin basic protein (MBP) expression in the mouse hippocampus was performed. Tau protein phosphorylation and MBP protein expression in the hippocampus were further analyzed by Western blotting. Myelin damage in the mouse optic nerve was evaluated by electron microscopy, and LFB staining was performed to assess myelin morphology in the mouse corpus callosum. MBP, Mpp5, and Egr2 transcript levels were quantified by qPCR. We observed that ICA treatment improved the learning and memory of 3 × Tg-AD mice and reduced Aβ deposition and tau protein phosphorylation in the hippocampus. Moreover, this treatment protocol increased myelin-related gene expression and reduced myelin damage.

Application of Hybrid Electrically Conductive Hydrogels Promotes Peripheral Nerve Regeneration

Peripheral nerve injury (PNI) occurs frequently, and the prognosis is unsatisfactory. As the gold standard of treatment, autologous nerve grafting has several disadvantages, such as lack of donors and complications. The use of functional biomaterials to simulate the natural microenvironment of the nervous system and the combination of different biomaterials are considered to be encouraging alternative methods for effective tissue regeneration and functional restoration of injured nerves. Considering the inherent presence of an electric field in the nervous system, electrically conductive biomaterials have been used to promote nerve regeneration. Due to their singular physical properties, hydrogels can provide a three-dimensional hydrated network that can be integrated into diverse sizes and shapes and stimulate the natural functions of nerve tissue. Therefore, conductive hydrogels have become the most effective biological material to simulate human nervous tissue's biological and electrical characteristics. The principal merits of conductive hydrogels include their physical properties and their electrical peculiarities sufficient to effectively transmit electrical signals to cells. This review summarizes the recent applications of conductive hydrogels to enhance peripheral nerve regeneration.

OUP accepted manuscript

In oligodendrocytes of the vertebrate central nervous system a complex network of transcriptional regulators is required to ensure correct and timely myelination of neuronal axons. Here we identify Zfp276, the only mammalian ZAD-domain containing zinc finger protein, as a transcriptional regulator of oligodendrocyte differentiation and central myelination downstream of Sox10. In the central nervous system, Zfp276 is exclusively expressed in mature oligodendrocytes. Oligodendroglial deletion of Zfp276 led to strongly reduced expression of myelin genes in the early postnatal mouse spinal cord. Retroviral overexpression of Zfp276 in cultured oligodendrocyte precursor cells induced precocious expression of maturation markers and myelin genes, further supporting its role in oligodendroglial differentiation. On the molecular level, Zfp276 directly binds to and represses Sox10-dependent gene regulatory regions of immaturity factors and functionally interacts with the transcriptional repressor Zeb2 to enable fast transition of oligodendrocytes to the myelinating stage.

Zinc finger E-Box binding homeobox 2 (ZEB2)-induced astrogliosis protected neuron from pyroptosis in cerebral ischemia and reperfusion injury

Ischemia injury can cause cell death or impairment of neuron and astrocytes, and thus induce loss of nerve function. central nervous systems injury induces an aberrant activation of astrocytes called astrogliosis. Pyroptosis, which is a kind of programmed cell death, was proved play an important role in ischemia injury. Zinc Finger E-Box Binding Homeobox 2 (ZEB2) promoted neuron astrogliosis, which play a protected role in neuron regeneration. However, its precise mechanism remains unclear. This study investigated the mechanism of ZEB2 on astrogliosis and neuron regeneration after cerebral ischemia reperfusion condition. To confirm our hypothesis, Neurons and astrocytes were isolated from fetal Sprague Dawley rats, in vivo Middle Cerebral Artery Occlusion/reperfusion (MCAO/R) rat model and in vitro oxygen-glucose deprivation/reperfusion (OGD/R)-treated astrocytes and neurocytes model were constructed. Our results showed that ZEB2 was expressed in nucleus of astrocyte and upregulated after OGD/R induction, ZEB2 promoted astrogliosis. Further upregulation of ZEB2 promoted the astrogliosis, which promoted neuron proliferation and regeneration by decreased pyroptosis. Moreover, this finding was further confirmed in vivo MCAO/R rat model. Overexpression of ZEB2 promoted astrogliosis, which decreased infarct volume and accumulated recovery of neurological function by alleviated pyroptosis. This finding revealed that ZEB2 was a regulator of the astrogliosis after ischemia/reperfusion injury, and then astrogliosis promoted neuron regeneration via decreased neuron pyroptosis. Therefore, ZEB2 may be a potential therapeutic target for ischemia/reperfusion injury.

Melanoma Immunotherapy and Precision Medicine in the Era of Tumor Micro-Tissue Engineering: Where Are We Now and Where Are We Going?

Malignant melanoma still remains a cancer with very poor survival rates, although it is at the forefront of personalized medicine. Most patients show partial responses and disease progressed due to adaptative resistance mechanisms, preventing long-lasting clinical benefits to the current treatments. The response to therapies can be shaped by not only taking into account cancer cell heterogeneity and plasticity, but also by its structural context as well as the cellular component of the tumor microenvironment (TME). Here, we review the recent development in the field of immunotherapy and target-based therapy and how, in the era of tumor micro-tissue engineering, ex-vivo assays could help to enhance our melanoma biology knowledge in its complexity, translating it in the development of successful therapeutic strategies, as well as in the prediction of therapeutic benefits.

Meta-Analysis Reveals Transcription Factor Upregulation in Cells of Injured Mouse Sciatic Nerve

Following peripheral nerve injury, transcription factors upregulated in the distal nerve play essential roles in Schwann cell reprogramming, fibroblast activation and immune cell function to create a permissive distal nerve environment for axonal regrowth. In this report, we first analysed four microarray data sets to identify transcription factors that have at least twofold upregulation in the mouse distal nerve stump at day 3 and day 7 post-injury. Next, we compared their relative mRNA levels through the analysis of an available bulk mRNA sequencing data set at day 5 post-injury. We then investigated the expression of identified TFs in analysed single-cell RNA sequencing data sets for the distal nerve at day 3 and day 9 post-injury. These analyses identified 55 transcription factors that have at least twofold upregulation in the distal nerve following mouse sciatic nerve injury. Expression profile for the identified 55 transcription factors in cells of the distal nerve stump was further analysed on the scRNA-seq data. Transcription factor network and functional analysis were performed in Schwann cells. We also validated the expression pattern of Jun, Junb, Runx1, Runx2, and Sox2 in the mouse distal nerve stump by immunostaining. The findings from our study not only could be used to understand the function of key transcription factors in peripheral nerve regeneration but also could be used to facilitate experimental design for future studies to investigate the function of individual TFs in peripheral nerve regeneration.

Peripheral Nerve Development and the Pathogenesis of Peripheral Neuropathy: the Sorting Point

Nerve development requires a coordinated sequence of events and steps to be accomplished for the generation of functional peripheral nerves to convey sensory and motor signals. Any abnormality during development may result in pathological structure and function of the nerve, which evolves in peripheral neuropathy. In this review, we will briefly describe different steps of nerve development while we will mostly focus on the molecular mechanisms involved in radial sorting of axons, one of these nerve developmental steps. We will summarize current knowledge of molecular pathways so far reported in radial sorting and their possible interactions. Finally, we will describe how disruption of these pathways may result in human neuropathies.

Lessons from Injury: How Nerve Injury Studies Reveal Basic Biological Mechanisms and Therapeutic Opportunities for Peripheral Nerve Diseases

Since Waller and Cajal in the nineteenth and early twentieth centuries, laboratory traumatic peripheral nerve injury studies have provided great insight into cellular and molecular mechanisms governing axon degeneration and the responses of Schwann cells, the major glial cell type of peripheral nerves. It is now evident that pathways underlying injury-induced axon degeneration and the Schwann cell injury-specific state, the repair Schwann cell, are relevant to many inherited and acquired disorders of peripheral nerves. This review provides a timely update on the molecular understanding of axon degeneration and formation of the repair Schwann cell. We discuss how nicotinamide mononucleotide adenylyltransferase 2 (NMNAT2) and sterile alpha TIR motif containing protein 1 (SARM1) are required for axon survival and degeneration, respectively, how transcription factor c-JUN is essential for the Schwann cell response to nerve injury and what each tells us about disease mechanisms and potential therapies. Human genetic association with NMNAT2 and SARM1 strongly suggests aberrant activation of programmed axon death in polyneuropathies and motor neuron disorders, respectively, and animal studies suggest wider involvement including in chemotherapy-induced and diabetic neuropathies. In repair Schwann cells, cJUN is aberrantly expressed in a wide variety of human acquired and inherited neuropathies. Animal models suggest it limits axon loss in both genetic and traumatic neuropathies, whereas in contrast, Schwann cell secreted Neuregulin-1 type 1 drives onion bulb pathology in CMT1A. Finally, we discuss opportunities for drug-based and gene therapies to prevent axon loss or manipulate the repair Schwann cell state to treat acquired and inherited neuropathies and neuronopathies.

Myelin Biology

Myelin is a key evolutionary specialization and adaptation of vertebrates formed by the plasma membrane of glial cells, which insulate axons in the nervous system. Myelination not only allows rapid and efficient transmission of electric impulses in the axon by decreasing capacitance and increasing resistance but also influences axonal metabolism and the plasticity of neural circuits. In this review, we will focus on Schwann cells, the glial cells which form myelin in the peripheral nervous system. Here, we will describe the main extrinsic and intrinsic signals inducing Schwann cell differentiation and myelination and how myelin biogenesis is achieved. Finally, we will also discuss how the study of human disorders in which molecules and pathways relevant for myelination are altered has enormously contributed to the current knowledge on myelin biology.

Diversity of developing peripheral glia revealed by single-cell RNA sequencing

The peripheral nervous system responds to a wide variety of sensory stimuli, a process that requires great neuronal diversity. These diverse neurons are closely associated with glial cells originating from the neural crest. However, the molecular nature and diversity among peripheral glia are not understood. Here, we used single-cell RNA sequencing to profile developing and mature glia from somatosensory dorsal root ganglia and auditory spiral ganglia. We found that glial precursors (GPs) in these two systems differ in their transcriptional profiles. Despite their unique features, somatosensory and auditory GPs undergo convergent differentiation to generate molecularly uniform myelinating and non-myelinating Schwann cells. By contrast, somatosensory and auditory satellite glial cells retain system-specific features. Lastly, we identified a glial signature gene set, providing new insights into commonalities among glia across the nervous system. This survey of gene expression in peripheral glia constitutes a resource for understanding functions of glia across different sensory modalities.

Targeted chromatin conformation analysis identifies novel distal neural enhancers of ZEB2 in pluripotent stem cell differentiation

The transcription factor zinc finger E-box binding protein 2 (ZEB2) controls embryonic and adult cell fate decisions and cellular maturation in many stem/progenitor cell types. Defects in these processes in specific cell types underlie several aspects of Mowat–Wilson syndrome (MOWS), which is caused by ZEB2 haplo-insufficiency. Human ZEB2, like mouse Zeb2, is located on chromosome 2 downstream of a ±3.5 Mb-long gene-desert, lacking any protein-coding gene. Using temporal targeted chromatin capture (T2C), we show major chromatin structural changes based on mapping in-cis proximities between the ZEB2 promoter and this gene desert during neural differentiation of human-induced pluripotent stem cells, including at early neuroprogenitor cell (NPC)/rosette state, where ZEB2 mRNA levels increase significantly. Combining T2C with histone-3 acetylation mapping, we identified three novel candidate enhancers about 500 kb upstream of the ZEB2 transcription start site. Functional luciferase-based assays in heterologous cells and NPCs reveal co-operation between these three enhancers. This study is the first to document in-cis Regulatory Elements located in ZEB2’s gene desert. The results further show the usability of T2C for future studies of ZEB2 REs in differentiation and maturation of multiple cell types and the molecular characterization of newly identified MOWS patients that lack mutations in ZEB2 protein-coding exons.

Hydroxypropyl chitosan/soy isolate protein conduits promote peripheral nerve regeneration

Designing scaffolds, with optimized micro-structure and function for promoting the release of neuro-related factors, is significant in peripheral nerve regeneration. Herein, a series of hydroxypropyl chitosan/soy protein isolate composite sponges (HCSS) were fabricated by a freeze-drying technique. The physicochemical properties of the resultant HCSS were examined by a Fourier infrared spectrometer, X-ray diffractometer, scanning electron microscope, water absorption assay, water retention assay, and compressive strength assay. The results indicated that HCSS exhibited an interconnected porous micro-structure and a high water retention ratio with the increase in SPI content. The biological characterization found that the HCSS-50 containing 50% SPI content profoundly promoted the proliferation of RSC96 cells and the secretion of neuro-related factors without excessive ROS production. In addition, HCSS-50 could significantly promote the expression of neuro-related factors; for example, the expression of TGF-β was 3 times higher than that of the control group. Finally, an optimized HCSS-based conduit was fabricated from HCSS-50 to repair sciatic nerve injury in rats with the combination of BMSCs or BMSC-derived Schwann cells. The results suggested that the constructed HCSS-based conduit accompanying BMSC-derived Schwann cells could effectively promote axonal regeneration and upregulate expression of neuro-related factors such as Krox20, Zeb2, and GAP43. Collectively, a newly engineered nerve conduit system was developed by incorporating HCSS-50 and BMSC-derived Schwann cells, which could be an alternative candidate for peripheral nerve regeneration.

Enhanced enteric neurogenesis by Schwann cell precursors in mouse models of Hirschsprung disease

Hirschsprung disease (HSCR) is characterized by congenital absence of enteric neurons in distal portions of the gut. Although recent studies identified Schwann cell precursors (SCPs) as a novel cellular source of enteric neurons, it is unknown how SCPs contribute to the disease phenotype of HSCR. Using Schwann cell-specific genetic labeling, we investigated SCP-derived neurogenesis in two mouse models of HSCR; Sox10 haploinsufficient mice exhibiting distal colonic aganglionosis and Ednrb knockout mice showing small intestinal aganglionosis. We also examined Ret dependency in SCP-derived neurogenesis using mice displaying intestinal aganglionosis in which Ret expression was conditionally removed in the Schwann cell lineage. SCP-derived neurons were abundant in the transition zone lying between the ganglionated and aganglionic segments, although SCP-derived neurogenesis was scarce in the aganglionic region. In the transition zone, SCPs mainly gave rise to nitrergic neurons that are rarely observed in the SCP-derived neurons under the normal condition. Enhanced SCP-derived neurogenesis was also detected in the transition zone of mice lacking RET expression in the Schwann cell lineage. Increased SCP-derived neurogenesis in the transition zone suggests that reduction in the vagal neural crest-derived enteric neurons promotes SCP-derived neurogenesis. SCPs may adopt a neuronal subtype by responding to changes in the gut environment. Robust SCP-derived neurogenesis can occur in a Ret-independent manner, which suggests that SCPs are a cellular source to compensate for missing enteric neurons in HSCR.

ZEB2, the Mowat-Wilson Syndrome Transcription Factor: Confirmations, Novel Functions, and Continuing Surprises

After its publication in 1999 as a DNA-binding and SMAD-binding transcription factor (TF) that co-determines cell fate in amphibian embryos, ZEB2 was from 2003 studied by embryologists mainly by documenting the consequences of conditional, cell-type specific Zeb2 knockout (cKO) in mice. In between, it was further identified as causal gene causing Mowat-Wilson Syndrome (MOWS) and novel regulator of epithelial-mesenchymal transition (EMT). ZEB2's functions and action mechanisms in mouse embryos were first addressed in its main sites of expression, with focus on those that helped to explain neurodevelopmental and neural crest defects seen in MOWS patients. By doing so, ZEB2 was identified in the forebrain as the first TF that determined timing of neuro-/gliogenesis, and thereby also the extent of different layers of the cortex, in a cell non-autonomous fashion, i.e., by its cell-intrinsic control within neurons of neuron-to-progenitor paracrine signaling. Transcriptomics-based phenotyping of Zeb2 mutant mouse cells have identified large sets of intact-ZEB2 dependent genes, and the cKO approaches also moved to post-natal brain development and diverse other systems in adult mice, including hematopoiesis and various cell types of the immune system. These new studies start to highlight the important adult roles of ZEB2 in cell-cell communication, including after challenge, e.g., in the infarcted heart and fibrotic liver. Such studies may further evolve towards those documenting the roles of ZEB2 in cell-based repair of injured tissue and organs, downstream of actions of diverse growth factors, which recapitulate developmental signaling principles in the injured sites. Evident questions are about ZEB2's direct target genes, its various partners, and ZEB2 as a candidate modifier gene, e.g., in other (neuro)developmental disorders, but also the accurate transcriptional and epigenetic regulation of its mRNA expression sites and levels. Other questions start to address ZEB2's function as a niche-controlling regulatory TF of also other cell types, in part by its modulation of growth factor responses (e.g., TGFβ/BMP, Wnt, Notch). Furthermore, growing numbers of mapped missense as well as protein non-coding mutations in MOWS patients are becoming available and inspire the design of new animal model and pluripotent stem cell-based systems. This review attempts to summarize in detail, albeit without discussing ZEB2's role in cancer, hematopoiesis, and its emerging roles in the immune system, how intense ZEB2 research has arrived at this exciting intersection.

H3K27 demethylases are dispensable for activation of Polycomb-regulated injury response genes in peripheral nerve

The induction of nerve injury response genes in Schwann cells depends on both transcriptional and epigenomic reprogramming. The nerve injury response program is regulated by the repressive histone mark H3K27 trimethylation (H3K27me3), deposited by Polycomb repressive complex 2 (PRC2). Loss of PRC2 function leads to early and augmented induction of the injury response gene network in peripheral nerves, suggesting H3K27 demethylases are required for derepression of Polycomb-regulated nerve injury genes. To determine the function of H3K27 demethylases in nerve injury, we generated Schwann cell-specific knockouts of H3K27 demethylase Kdm6b and double knockouts of Kdm6b/Kdm6a (encoding JMJD3 and UTX). We found that H3K27 demethylases are largely dispensable for Schwann cell development and myelination. In testing the function of H3K27 demethylases after injury, we found early induction of some nerve injury genes was diminished compared with control, but most injury genes were largely unaffected at 1 and 7 days post injury. Although it was proposed that H3K27 demethylases are required to activate expression of the cyclin-dependent kinase inhibitor Cdkn2a in response to injury, Schwann cell-specific deletion of H3K27 demethylases affected neither the expression of this gene nor Schwann cell proliferation after nerve injury. To further characterize the regulation of nerve injury response genes, we found that injury genes are associated with repressive histone H2AK119 ubiquitination catalyzed by PRC1, which declines after injury. Overall, our results indicate H3K27 demethylation is not required for induction of injury response genes and that other mechanisms likely are involved in activating Polycomb-repressed injury genes in peripheral nerve.

Rethinking the biology of metastatic melanoma: a holistic approach

Over the past decades, melanoma-related mortality has remained nearly stable. The main reason is treatment failure of metastatic disease and the inherently linked knowledge gap regarding metastasis formation. In order to elicit invasion, melanoma cells manipulate the tumor microenvironment, gain motility, and adhere to the extracellular matrix and cancer-associated fibroblasts. Melanoma cells thereby express different cell adhesion molecules like laminins, integrins, N-cadherin, and others. Epithelial-mesenchymal transition (EMT) is physiological during embryologic development, but reactivated during malignancy. Despite not being truly epithelial, neural crest-derived malignancies like melanoma share similar biological programs that enable tumorigenesis, invasion, and metastasis. This complex phenomenon is termed phenotype switching and is intertwined with oncometabolism as well as dormancy escape. Additionally, it has been shown that primary melanoma shed exosomes that create a favorable premetastatic niche in the microenvironment of secondary organs and lymph nodes. Although the growing body of literature describes the aforementioned concepts separately, an integrative holistic approach is missing. Using melanoma as a tumor model, this review will shed light on these complex biological principles in an attempt to clarify the mechanistic metastatic pathways that dictate tumor and patient fate.

Effects of early crush on aging wild type and Connexin 32 knockout mice: Evidence for a neuroprotective state in CMT1X mouse nerve

The long-term sequelae of nerve injury as well as age-related neurodegeneration have been documented in numerous studies, however the role of Cx32 in these processes is not well understood. There is a need for better understanding of the molecular mechanisms that underlie long-term suboptimal nerve function and for approaches to prevent or improve it. In this communication we describe our studies using whole animal electrophysiology to examine the long-term sequelae of sciatic nerve crush in both WT and Cx32KO mice, a model of X-linked Charcot Marie Tooth disease, a subtype of inherited peripheral neuropathies. We present results from electrical nerve recordings done 14 to 27 days and 18 to 20 months after a unilateral sciatic nerve crush performed on 35 to 37-day old mice. Contrary to expectations, we find that whereas crush injury leads to a degradation of WT nerve function relative to uninjured nerves at 18 to 20 months, previously crushed Cx32KO nerves perform at the same level as their uninjured counterparts. Thus, 18 to 20 months after injury, WT nerves perform below the level of normal (uninjured) WT nerves in both motor and sensory nerve function. In contrast, measures of nerve function in Cx32KO mice are degraded for sensory axons but exhibit no additional dysfunction in motor axons. Early nerve injury has no negative electrophysiologic effect on the Cx32 KO motor nerves. Based on our prior demonstration that the transcriptomic profile of uninjured Cx32KO and injured WT sciatic nerves are very similar, the lack of an additional effect of crush on Cx32KO motor nerve parameters suggests that Cx32 knockout may implement a form of neuroprotection that limits the effects of subsequent injury.

Role of the Peripheral Nervous System in PD Pathology, Diagnosis, and Treatment

Studies on Parkinson disease (PD) have mostly focused on the central nervous system—specifically, on the loss of mesencephalic dopaminergic neurons and associated motor dysfunction. However, the peripheral nervous system (PNS) is gaining prominence in PD research, with increasing clinical attention being paid to non-motor symptoms. Researchers found abnormal deposition of α-synuclein and neuroinflammation in the PNS. Attempts have been made to use these pathological changes during the clinical diagnosis of PD. Animal studies demonstrated that combined transplantation of autologous peripheral nerves and cells with tyrosine hydroxylase activity can reduce dopaminergic neuronal damage, and similar effects were observed in some clinical trials. In this review, we will systematically explain PNS performance in PD pathology and its clinical diagnostic research, describe PNS experimental results [especially Schwann cell (SC) transplantation in the treatment of PD animal models] and the results of clinical trials, and discuss future directions. The mechanism by which SCs produce such a therapeutic effect and the safety of transplantation therapy are briefly described.

Endothelial Zeb2 preserves the hepatic angioarchitecture and protects against liver fibrosis

Aims

Hepatic capillaries are lined with specialized liver sinusoidal endothelial cells (LSECs) which support macromolecule passage to hepatocytes and prevent fibrosis by keeping hepatic stellate cells (HSCs) quiescent. LSEC specialization is co-determined by transcription factors. The zinc-finger E-box-binding homeobox (Zeb)2 transcription factor is enriched in LSECs. Here, we aimed to elucidate the endothelium-specific role of Zeb2 during maintenance of the liver and in liver fibrosis.

Methods and results

To study the role of Zeb2 in liver endothelium we generated EC-specific Zeb2 knock-out (EC^KO) mice. Sequencing of liver EC RNA revealed that deficiency of Zeb2 results in prominent expression changes in angiogenesis-related genes. Accordingly, the vascular area was expanded and the presence of pillars inside EC^KO liver vessels indicated that this was likely due to increased intussusceptive angiogenesis. LSEC marker expression was not profoundly affected and fenestrations were preserved upon Zeb2 deficiency. However, an increase in continuous EC markers suggested that Zeb2-deficient LSECs are more prone to dedifferentiation, a process called ‘capillarization’. Changes in the endothelial expression of ligands that may be involved in HSC quiescence together with significant changes in the expression profile of HSCs showed that Zeb2 regulates LSEC–HSC communication and HSC activation. Accordingly, upon exposure to the hepatotoxin carbon tetrachloride (CCl₄), livers of EC^KO mice showed increased capillarization, HSC activation, and fibrosis compared to livers from wild-type littermates. The vascular maintenance and anti-fibrotic role of endothelial Zeb2 was confirmed in mice with EC-specific overexpression of Zeb2, as the latter resulted in reduced vascularity and attenuated CCl₄-induced liver fibrosis.

Conclusion

Endothelial Zeb2 preserves liver angioarchitecture and protects against liver fibrosis. Zeb2 and Zeb2-dependent genes in liver ECs may be exploited to design novel therapeutic strategies to attenuate hepatic fibrosis.

Transcriptional profiling of mouse peripheral nerves to the single-cell level to build a sciatic nerve ATlas (SNAT)

Peripheral nerves are organ-like structures containing diverse cell types to optimize function. This interactive assembly includes mostly axon-associated Schwann cells, but also endothelial cells of supporting blood vessels, immune system-associated cells, barrier-forming cells of the perineurium surrounding and protecting nerve fascicles, and connective tissue-resident cells within the intra-fascicular endoneurium and inter-fascicular epineurium. We have established transcriptional profiles of mouse sciatic nerve-inhabitant cells to foster the fundamental understanding of peripheral nerves. To achieve this goal, we have combined bulk RNA sequencing of developing sciatic nerves up to the adult with focused bulk and single-cell RNA sequencing of Schwann cells throughout postnatal development, extended by single-cell transcriptome analysis of the full sciatic nerve both perinatally and in the adult. The results were merged in the transcriptome resource Sciatic Nerve ATlas (SNAT: https://www.snat.ethz.ch). We anticipate that insights gained from our multi-layered analysis will serve as valuable interactive reference point to guide future studies.

Genetic Events and Signaling Mechanisms Underlying Schwann Cell Fate in Development and Cancer

In this review, we describe Schwann cell development from embryonic neural crest cells to terminally differentiated myelinated and nonmyelinated mature Schwann cells. We focus on the genetic drivers and signaling mechanisms mediating decisions to proliferate versus differentiate during Schwann cell development, highlighting pathways that overlap with Schwann cell development and are dysregulated in tumorigenesis. We conclude by considering how our knowledge of the events underlying Schwann cell development and mouse models of schwannoma, neurofibroma, and malignant peripheral nerve sheath tumor can inform novel therapeutic strategies for patients with cancers derived from Schwann cell lineages.

Schwann cell plasticity regulates neuroblastic tumor cell differentiation via epidermal growth factor-like protein 8

Adult Schwann cells (SCs) possess an inherent plastic potential. This plasticity allows SCs to acquire repair-specific functions essential for peripheral nerve regeneration. Here, we investigate whether stromal SCs in benign-behaving peripheral neuroblastic tumors adopt a similar cellular state. We profile ganglioneuromas and neuroblastomas, rich and poor in SC stroma, respectively, and peripheral nerves after injury, rich in repair SCs. Indeed, stromal SCs in ganglioneuromas and repair SCs share the expression of nerve repair-associated genes. Neuroblastoma cells, derived from aggressive tumors, respond to primary repair-related SCs and their secretome with increased neuronal differentiation and reduced proliferation. Within the pool of secreted stromal and repair SC factors, we identify EGFL8, a matricellular protein with so far undescribed function, to act as neuritogen and to rewire cellular signaling by activating kinases involved in neurogenesis. In summary, we report that human SCs undergo a similar adaptive response in two patho-physiologically distinct situations, peripheral nerve injury and tumor development.

YAP and TAZ regulate Schwann cell proliferation and differentiation during peripheral nerve regeneration

YAP and TAZ are effectors of the Hippo pathway that controls multicellular development by integrating chemical and mechanical signals. Peripheral nervous system development depends on the Hippo pathway. We previously showed that loss of YAP and TAZ impairs the development of peripheral nerve as well as Schwann cell myelination. The role of the Hippo pathway in peripheral nerve regeneration has just started to be explored. After injury, Schwann cells adopt new identities to promote regeneration by converting to a repair‐promoting phenotype. While the reprogramming of Schwann cells to repair cells has been well characterized, the maintenance of such repair phenotype cannot be sustained for a very long period, which limits nerve repair in human. First, we show that short or long‐term myelin maintenance is not affected by defect in YAP and TAZ expression. Using crush nerve injury and conditional mutagenesis in mice, we also show that YAP and TAZ are regulators of repair Schwann cell proliferation and differentiation. We found that YAP and TAZ are required in repair Schwann cells for their redifferentiation into myelinating Schwann cell following crush injury. In this present study, we describe how the Hippo pathway and YAP and TAZ regulate remyelination over time during peripheral nerve regeneration.