A rapid and versatile method for the isolation, purification and cryogenic storage of Schwann cells from adult rodent nerves

GFP-labeled Schwann cell-like cells derived from hair follicle epidermal neural crest stem cells promote the acellular nerve allografts to repair facial nerve defects in rats

BACKGROUND

Acellular nerve allografts (ANAs) have been successfully applied to bridge facial nerve defects, and transplantation of stem cells may enhance the regenerative results. Up to now, application of hair follicle epidermal neural crest stem cell-derived Schwann cell-like cells (EPI-NCSC-SCLCs) combined with ANAs for bridging facial nerve defects has not been reported.

METHODS

The effect of ANAs laden with green fluorescent protein (GFP)-labeled EPI-NCSC-SCLCs (ANA + cells) on bridging rat facial nerve trunk defects (5-mm-long) was detected by functional and morphological examination, as compared with autografts and ANAs, respectively.

RESULTS

(1) EPI-NCSC-SCLCs had good compatibility with ANAs in vitro. (2) In the ANA + cells group, the GFP signals were observed by in vivo imaging system for small animals within 8 weeks, and GFP-labeled EPI-NCSC-SCLCs were detected in the tissue slices at 16 weeks postoperatively. (3) The facial symmetry at rest after surgery in the ANA + cells group was better than that in the ANA group (p < 0.05), and similar to that in the autograft group (p > 0.05). The initial recovery time of vibrissal and eyelid movement in the ANA group was 2 weeks later than that in the other two groups. (4) The myelinated fibers, myelin sheath thickness and diameter of the axons of the buccal branches in the ANA group were significantly worse than those in the other two groups (P < 0.05), and the results in the ANA + cells group were similar to those in the autograft group (p > 0.05).

CONCLUSIONS

EPI-NCSC-SCLCs could promote functional and morphological recovery of rat facial nerve defects, and GFP labeling could track the transplanted EPI-NCSC-SCLCs in vivo for a certain period of time. These may provide a novel choice for clinical treatment of peripheral nerve defects.

Influence of Magnesium Degradation on Schwannoma Cell Responses to Nerve Injury Using an In Vitro Injury Model

Nerve guidance conduits for peripheral nerve injuries can be improved using bioactive materials such as magnesium (Mg) and its alloys, which could provide both structural and trophic support. Therefore, we investigated whether exposure to Mg and Mg-1.6wt%Li thin films (Mg/Mg-1.6Li) would alter acute Schwann cell responses to injury. Using the RT4-D6P2T Schwannoma cell line (SCs), we tested extracts from freeze-killed cells (FKC) and nerves (FKN) as in vitro injury stimulants. Both FKC and FKN induced SC release of the macrophage chemoattractant protein 1 (MCP-1), a marker of the repair SC phenotype after injury. Next, FKC-stimulated cells exposed to Mg/Mg-1.6Li reduced MCP-1 release by 30%, suggesting that these materials could have anti-inflammatory effects. Exposing FKC-treated cells to Mg/Mg-1.6Li reduced the gene expression of the nerve growth factor (NGF), glial cell line-derived neurotrophic factor (GDNF), and myelin protein zero (MPZ), but not the p75 neurotrophin receptor. In the absence of FKC, Mg/Mg-1.6Li treatment increased the expression of NGF, p75, and MPZ, which can be beneficial to nerve regeneration. Thus, the presence of Mg can differentially alter SCs, depending on the microenvironment. These results demonstrate the applicability of this in vitro nerve injury model, and that Mg has wide-ranging effects on the repair SC phenotype.

Fabry disease Schwann cells release p11 to induce sensory neuron hyperactivity

Patients with Fabry disease suffer from chronic debilitating pain and peripheral sensory neuropathy with minimal treatment options, but the cellular drivers of this pain are unknown. Here, we propose a mechanism we believe to be novel in which altered signaling between Schwann cells and sensory neurons underlies the peripheral sensory nerve dysfunction we observed in a genetic rat model of Fabry disease. Using in vivo and in vitro electrophysiological recordings, we demonstrated that Fabry rat sensory neurons exhibited pronounced hyperexcitability. Schwann cells probably contributed to this finding because application of mediators released from cultured Fabry Schwann cells induced spontaneous activity and hyperexcitability in naive sensory neurons. We examined putative algogenic mediators using proteomic analysis and found that Fabry Schwann cells released elevated levels of the protein p11 (S100A10), which induced sensory neuron hyperexcitability. Removal of p11 from Fabry Schwann cell media caused hyperpolarization of neuronal resting membrane potentials, indicating that p11 may contribute to the excessive neuronal excitability caused by Fabry Schwann cells. These findings demonstrate that sensory neurons from rats with Fabry disease exhibit hyperactivity caused in part by Schwann cell release of the protein p11.

Cultivation of Schwann cells from fresh and non-fresh adult equine peripheral nerves

BACKGROUND

Over the past 25 years, acquired equine polyneuropathy (AEP) has emerged as a neurological disease in Scandinavian horses. This condition is characterized by histopathological features including the presence of Schwann cell (SC) inclusions. Cultivated equine SCs would serve as a valuable resource for investigations of factors triggering this Schwannopathy. Ideally, cells should be sampled for cultivation from fresh nerves immediately after death of the animal, however the availability of fresh material is limited, due to the inconsistent case load and the inherent technical and practical challenges to collection of samples in the field. This study aimed to cultivate SCs from adult equine peripheral nerves and assess their ability to survive in sampled nerve material over time to simulate harvesting of SCs in field situations.

NEW METHODS

Peripheral nerves from five non-neurological horses were used. After euthanasia, both fresh and non-fresh nerve samples were harvested from each horse. Flow cytometry was employed to confirm the cellular identity and to determine the SC purity.

RESULTS

The results revealed successful establishment of SC cultures from adult equine peripheral nerves, with the potential to achieve high SC purity from both fresh and non-fresh nerve samples.

COMPARISON WITH EXISTING METHOD

While most SC isolation methods focus on harvest of cells from fresh nerve materials from laboratory animals, our approach highlights the possibility of utilizing SC cultures from field-harvested and transported nerve samples from horses.

CONCLUSIONS

We describe a method for isolating SCs with high purity from both fresh and non-fresh peripheral nerves of adult horses.

Human Schwann Cells in vitro I. Nerve Tissue Processing, Pre-degeneration, Isolation, and Culturing of Primary Cells

This paper presents versatile protocols to prepare primary human Schwann cell (hSC) cultures from mature peripheral nervous system tissues, including fascicles from long spinal nerves, nerve roots, and ganglia. This protocol starts with a description of nerve tissue procurement, handling, and dissection to obtain tissue sections suitable for hSC isolation and culturing. A description follows on how to disintegrate the nerve tissue by delayed enzymatic dissociation, plate the initial cell suspensions on a two-dimensional substrate, and culture the primary hSCs. Each section contains detailed procedures, technical notes, and background information to aid investigators in understanding and managing all steps. Some general recommendations are made to optimize the recovery, growth, and purity of the hSC cultures irrespective of the tissue source. These recommendations include: (1) pre-culturing epineurium- and perineurium-free nerve fascicles under conditions of adherence or suspension depending on the size of the explants to facilitate the release of proliferative, in vitro-activated hSCs; (2) plating the initial cell suspensions as individual droplets on a laminin-coated substrate to expedite cell adhesion and thereby increase the recovery of viable cells; and (3) culturing the fascicles (pre-degeneration step) and the cells derived therefrom in mitogen- and serum-supplemented medium to accelerate hSC dedifferentiation and promote mitogenesis before and after tissue dissociation, respectively. The hSC cultures obtained as suggested in this protocol are suitable for assorted basic and translational research applications. With the appropriate adaptations, donor-relevant hSC cultures can be prepared using fresh or postmortem tissue biospecimens of a wide range of types and sizes.

Schwann cell release of p11 induces sensory neuron hyperactivity in Fabry disease

Patients with Fabry disease suffer from chronic debilitating pain and peripheral sensory neuropathy with minimal treatment options, but the cellular drivers of this pain are unknown. Here, we propose a novel mechanism by which altered signaling between Schwann cells and sensory neurons underlies the peripheral sensory nerve dysfunction we observe in a genetic rat model of Fabry disease. Using in vivo and in vitro electrophysiological recordings, we demonstrate that Fabry rat sensory neurons exhibit pronounced hyperexcitability. Schwann cells likely contribute to this finding as application of mediators released from cultured Fabry Schwann cells induces spontaneous activity and hyperexcitability in naïve sensory neurons. We examined putative algogenic mediators using proteomic analysis and found that Fabry Schwann cells release elevated levels of the protein p11 (S100-A10) which induces sensory neuron hyperexcitability. Removal of p11 from Fabry Schwann cell media causes hyperpolarization of neuronal resting membrane potential, indicating that p11 contributes to the excessive neuronal excitability caused by Fabry Schwann cells. These findings demonstrate that rats with Fabry disease exhibit sensory neuron hyperexcitability caused in part by Schwann cell release of the protein p11.

Application of a Magnetic Platform in α6 Integrin-Positive iPSC-TM Purification

The emergence of induced pluripotent stem cell (iPSC) technology has provided a new approach to regenerating decellularized trabecular meshwork (TM) in glaucoma. We have previously generated iPSC-derived TM (iPSC-TM) using a medium conditioned by TM cells and verified its function in tissue regeneration. Because of the heterogeneity of iPSCs and the isolated TM cells, iPSC-TM cells appear to be heterogeneous, which impedes our understanding of how the decellularized TM may be regenerated. Herein, we developed a protocol based on a magnetic-activated cell sorting (MACS) system or an immunopanning (IP) method for sorting integrin subunit alpha 6 (ITGA6)-positive iPSC-TM, an example of the iPSC-TM subpopulation. We first analyzed the purification efficiency of these two approaches by flow cytometry. In addition, we also determined cell viability by analyzing the morphologies of the purified cells. To conclude, the MACS-based purification could yield a higher ratio of ITGA6-positive iPSC-TM and maintain a relatively higher cell viability than the IP-based method, allowing for the preparation of any iPSC-TM subpopulation of interest and facilitating a better understanding of the regenerative mechanism of iPSC-based therapy.

Targeting USP10 induces degradation of oncogenic ANLN in esophageal squamous cell carcinoma

Anillin (ANLN) is a mitosis-related protein that promotes contractile ring formation and cytokinesis, but its cell cycle-dependent degradation mechanisms in cancer cells remain unclear. Here, we show that high expression of ANLN promotes cytokinesis and proliferation in esophageal squamous cell carcinoma (ESCC) cells and is associated with poor prognosis in ESCC patients. Furthermore, the findings of the study showed that the deubiquitinating enzyme USP10 interacts with ANLN and positively regulates ANLN protein levels. USP10 removes the K11- and K63-linked ubiquitin chains of ANLN through its deubiquitinase activity and prevents ANLN ubiquitin-mediated degradation. Importantly, USP10 promotes contractile ring assembly at the cytokinetic furrow as well as cytokinesis by stabilizing ANLN. Interestingly, USP10 and the E3 ubiquitin ligase APC/C co-activator Cdh1 formed a functional complex with ANLN in a non-competitive manner to balance ANLN protein levels. In addition, the macrolide compound FW-04-806 (F806), a natural compound with potential for treating ESCC, inhibited the mitosis of ESCC cells by targeting USP10 and promoting ANLN degradation. F806 selectively targeted USP10 and inhibited its catalytic activity but did not affect the binding of Cdh1 to ANLN and alters the balance of the USP10-Cdh1-ANLN complex. Additionally, USP10 expression was positively correlated with ANLN level and poor prognosis of ESCC patients. Overall, targeting the USP10-ANLN axis can effectively inhibit ESCC cell-cycle progression.

Runt-related transcription factor 3, mediated by DNA-methyltransferase 1, regulated Schwann cell proliferation and myelination during peripheral nerve regeneration via JAK/STAT signaling pathway

Schwann cells (SCs) play a crucial role in peripheral nerve injury and regeneration. Recently, RUNX3 was found to be linked with neurological dysfunction. We examined the RUNX3 expression in sciatic nerve stumps with peripheral nerve injury of rats, cyclic adenosine monophosphate (cAMP)-induced SCs. MTT assay was applied to determine the proliferation of SCs. Cell migration and apoptosis were assessed using wound healing assay and flow cytometry. Subsequently, we detected the methylation level of RUNX3 using Methylation-specific PCR assay and verified its regulation by DNMT1. The RUNX3 expressions were increased in sciatic nerve stumps with peripheral nerve injury and cAMP-induced SCs differentiation, which were related to demethylation of its promoter region regulated by DNMT1. RUNX3 knockdown notably suppressed the proliferation and migration, and induced the cell apoptosis of SCs. Silencing of RUNX3 inhibited the cAMP-induced morphological changes of SCs and the increase of myelin-related proteins induced by cAMP in SCs, while RUNX3 overexpression exerted opposite effects. Besides, the overexpression of RUNX3 promoted the activation of JAK/STAT signaling to regulate SCs proliferation and myelination. Meanwhile, DNMT1 overexpression inhibited the expression of RUNX3, and cell proliferation and myelination. In conclusion, RUNX3 mediated by DNMT1 regulated SC proliferation and myelination via JAK/STAT signaling pathway.

Peripheral sensory neurons and non-neuronal cells express functional Piezo1 channels

Here, we present evidence showing Piezo1 protein expression in the primary sensory neurons (PSNs) and non-neuronal cells of rat peripheral nervous system. Using a knockdown/knockout validated antibody, we detected Piezo1 immunoreactivity (IR) in ∼60% of PSNs of rat dorsal root ganglia (DRG) with higher IR density in the small- and medium-sized neurons. Piezo1-IR was clearly identified in DRG perineuronal glia, including satellite glial cells (SGCs) and Schwann cells; in sciatic nerve Schwann cells surrounding the axons and cutaneous afferent endings; and in skin epidermal Merkel cells and melanocytes. Neuronal and non-neuronal Piezo1 channels were functional since various cells (dissociated PSNs and SGCs from DRGs, isolated Schwann cells, and primary human melanocytes) exhibited a robust response to Piezo1 agonist Yoda1 by an increase of intracellular Ca²⁺ concentration ([Ca²⁺]_i). These responses were abolished by non-specific Piezo1 antagonist GsMTx4. Immunoblots showed elevated Piezo1 protein in DRG proximal to peripheral nerve injury-induced painful neuropathy, while PSNs and SGCs from rats with neuropathic pain showed greater Yoda1-evoked elevation of [Ca²⁺]_i and an increased frequency of cells responding to Yoda1, compared to controls. Sciatic nerve application of GsMTx4 alleviated mechanical hypersensitivity induced by Yoda1. Overall, our data show that Piezo1 is widely expressed by the neuronal and non-neuronal cells in the peripheral sensory pathways and that painful nerve injury appeared associated with activation of Piezo1 in PSNs and peripheral glial cells.

Glial cell line-derived neurotrophic factor and brain-derived neurotrophic factor regulate the interaction between astrocytes and Schwann cells at the trigeminal root entry zone

The trigeminal root entry zone is the zone at which the myelination switches from peripheral Schwann cells to central oligodendrocytes. Its special anatomical and physiological structure renders it susceptible to nerve injury. The etiology of most primary trigeminal neuralgia is closely related to microvascular compression of the trigeminal root entry zone. This study aimed to develop an efficient in vitro model mimicking the glial environment of trigeminal root entry zone as a tool to investigate the effects of glial cell line-derived neurotrophic factor and brain-derived neurotrophic factor on the structural and functional integrity of trigeminal root entry zone and modulation of cellular interactions. Primary astrocytes and Schwann cells isolated from trigeminal root entry zone of postnatal rats were inoculated into a two-well silicon culture insert to mimic the trigeminal root entry zone microenvironment and treated with glial cell line-derived neurotrophic factor and brain-derived neurotrophic factor. In monoculture, glial cell line-derived neurotrophic factor promoted the migration of Schwann cells, but it did not have effects on the migration of astrocytes. In the co-culture system, glial cell line-derived neurotrophic factor promoted the bidirectional migration of astrocytes and Schwann cells. Brain-derived neurotrophic factor markedly promoted the activation and migration of astrocytes. However, in the co-culture system, brain-derived neurotrophic factor inhibited the migration of astrocytes and Schwann cells to a certain degree. These findings suggest that glial cell line-derived neurotrophic factor and brain-derived neurotrophic factor are involved in the regulation of the astrocyte-Schwann cell interaction in the co-culture system derived from the trigeminal root entry zone. This system can be used as a cell model to study the mechanism of glial dysregulation associated with trigeminal nerve injury and possible therapeutic interventions.

Comparison of human skin- and nerve-derived Schwann cells reveals many similarities and subtle genomic and functional differences

Skin is an easily accessible tissue and a rich source of Schwann cells (SCs). Toward potential clinical application of autologous SC therapies, we aim to improve the reliability and specificity of our protocol to obtain SCs from small skin samples. As well, to explore potential functional distinctions between skin-derived SCs (Sk-SCs) and nerve-derived SCs (N-SCs), we used single-cell RNA-sequencing and a series of in vitro and in vivo assays. Our results showed that Sk-SCs expressed typical SC markers. Single-cell sequencing of Sk- and N-SCs revealed an overwhelming overlap in gene expression with the exception of HLA genes which were preferentially up-regulated in Sk-SCs. In vitro, both cell types exhibited similar levels of proliferation, migration, uptake of myelin debris and readily associated with neurites when co-cultured with human iPSC-induced motor neurons. Both exhibited ensheathment of multiple neurites and early phase of myelination, especially in N-SCs. Interestingly, dorsal root ganglion (DRG) neurite outgrowth assay showed substantially more complexed neurite outgrowth in DRGs exposed to Sk-SC conditioned media compared to those from N-SCs. Multiplex ELISA array revealed shared growth factor profiles, but Sk-SCs expressed a higher level of VEGF. Transplantation of Sk- and N-SCs into injured peripheral nerve in nude rats and NOD-SCID mice showed close association of both SCs to regenerating axons. Myelination of rodent axons was observed infrequently by N-SCs, but absent in Sk-SC xenografts. Overall, our results showed that Sk-SCs share near-identical properties to N-SCs but with subtle differences that could potentially enhance their therapeutic utility.

An EPO ‐loaded multifunctional hydrogel synergizing with adipose‐derived stem cells restores neurogenic erectile function via enhancing nerve regeneration and penile rehabilitation

Neurogenic erectile dysfunction (nED) is one of the most common and intractable postoperative complications of rectal and prostate cancer surgery and sometimes accompanies patients lifelong. The transplantation of stem cells has been proved a promising way for treatment. However, the therapeutic efficacy is severely impaired by excessive cell loss and death and poor accumulation in the injury site along with the traditional implantation strategy. Herein, an EPO‐loaded multifunctional hydrogel was designed. The hydrogels' adhesive property and mechanical strength were enhanced by adding catechol‐catechol adducts, thus significantly improving adipose‐derived stem cells (ADSC) retention and rescuing cell loss in the injury site. Meanwhile, the sustained release of EPO effectively ameliorated the viability and paracrine activity of ADSC, leading to enhanced migration of Schwann cells and differentiation of PC12 cells in vivo. On a bilateral cavernous nerve injury rat model, the present stem cell‐EPO‐hydrogel implanted strategy could significantly alleviate erectile dysfunction. The higher expression of Tuj1 and lower expression of GFAP in the major pelvic ganglia (MPG) indicated the acceleration of neural differentiation while the suppressing development of astrocytes. Also, the combined therapy restored the expression levels of eNOs, nNOs, and α‐SMA in penile tissues, suggesting the rehabilitation of the penis. Further analysis of Masson trichrome staining and apoptosis evaluation of the corpus cavernosum showed the preservation of vascular endothelium content and the prevention of penile fibrosis after denervation. Overall, we believe that this combined strategy presents a promising way not only for restoring neurogenic erectile function but also for the clinical translation of stem cell therapy.

Engineered Schwann Cell-Based Therapies for Injury Peripheral Nerve Reconstruction

Compared with the central nervous system, the adult peripheral nervous system possesses a remarkable regenerative capacity, which is due to the strong plasticity of Schwann cells (SCs) in peripheral nerves. After peripheral nervous injury, SCs de-differentiate and transform into repair phenotypes, and play a critical role in axonal regeneration, myelin formation, and clearance of axonal and myelin debris. In view of the limited self-repair capability of SCs for long segment defects of peripheral nerve defects, it is of great clinical value to supplement SCs in necrotic areas through gene modification or stem cell transplantation or to construct tissue-engineered nerve combined with bioactive scaffolds to repair such tissue defects. Based on the developmental lineage of SCs and the gene regulation network after peripheral nerve injury (PNI), this review summarizes the possibility of using SCs constructed by the latest gene modification technology to repair PNI. The therapeutic effects of tissue-engineered nerve constructed by materials combined with Schwann cells resembles autologous transplantation, which is the gold standard for PNI repair. Therefore, this review generalizes the research progress of biomaterials combined with Schwann cells for PNI repair. Based on the difficulty of donor sources, this review also discusses the potential of “unlimited” provision of pluripotent stem cells capable of directing differentiation or transforming existing somatic cells into induced SCs. The summary of these concepts and therapeutic strategies makes it possible for SCs to be used more effectively in the repair of PNI.

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.

Single-Cell Regulatory Network Inference and Clustering Identifies Cell-Type Specific Expression Pattern of Transcription Factors in Mouse Sciatic Nerve

Advances in single-cell RNA sequencing technologies and bioinformatics methods allow for both the identification of cell types in a complex tissue and the large-scale gene expression profiling of various cell types in a mixture. In this report, we analyzed a single-cell RNA sequencing (scRNA-seq) dataset for the intact adult mouse sciatic nerve and examined cell-type specific transcription factor expression and activity during peripheral nerve homeostasis. In total, we identified 238 transcription factors expressed in nine different cell types of intact mouse sciatic nerve. Vascular smooth muscle cells have the lowest number of transcription factors expressed with 17 transcription factors identified. Myelinating Schwann cells (mSCs) have the highest number of transcription factors expressed, with 61 transcription factors identified. We created a cell-type specific expression map for the identified 238 transcription factors. Our results not only provide valuable information about the expression pattern of transcription factors in different cell types of adult peripheral nerves but also facilitate future studies to understand the function of key transcription factors in the peripheral nerve homeostasis and disease.

"Tripartite Synapses" in Taste Buds: A Role for Type I Glial-like Taste Cells

In mammalian taste buds, Type I cells comprise half of all cells. These are termed "glial-like" based on morphologic and molecular features, but there are limited studies describing their function. We tested whether Type I cells sense chemosensory activation of adjacent chemosensory (i.e., Types II and III) taste bud cells, similar to synaptic glia. Using Gad2;;GCaMP3 mice of both sexes, we confirmed by immunostaining that, within taste buds, GCaMP expression is predominantly in Type I cells (with no Type II and ≈28% Type III cells expressing weakly). In dissociated taste buds, GCaMP+ Type I cells responded to bath-applied ATP (10-100 μm) but not to 5-HT (transmitters released by Type II or III cells, respectively). Type I cells also did not respond to taste stimuli (5 μm cycloheximide, 1 mm denatonium). In lingual slice preparations also, Type I cells responded to bath-applied ATP (10-100 μm). However, when taste buds in the slice were stimulated with bitter tastants (cycloheximide, denatonium, quinine), Type I cells responded robustly. Taste-evoked responses of Type I cells in the slice preparation were significantly reduced by desensitizing purinoceptors or by purinoceptor antagonists (suramin, PPADS), and were essentially eliminated by blocking synaptic ATP release (carbenoxolone) or degrading extracellular ATP (apyrase). Thus, taste-evoked release of afferent ATP from type II chemosensory cells, in addition to exciting gustatory afferent fibers, also activates glial-like Type I taste cells. We speculate that Type I cells sense chemosensory activation and that they participate in synaptic signaling, similarly to glial cells at CNS tripartite synapses.SIGNIFICANCE STATEMENT Most studies of taste buds view the chemosensitive excitable cells that express taste receptors as the sole mediators of taste detection and transmission to the CNS. Type I "glial-like" cells, with their ensheathing morphology, are mostly viewed as responsible for clearing neurotransmitters and as the "glue" holding the taste bud together. In the present study, we demonstrate that, when intact taste buds respond to their natural stimuli, Type I cells sense the activation of the chemosensory cells by detecting the afferent transmitter. Because Type I cells synthesize GABA, a known gliotransmitter, and cognate receptors are present on both presynaptic and postsynaptic elements, Type I cells may participate in GABAergic synaptic transmission in the manner of astrocytes at tripartite synapses.

Heregulin Activity Assays for Residual Testing of Cell Therapy Products

Background

Heregulin is a ligand for the protooncogene product ErbB/HER that acts as  a key mitogenic factor for human Schwann cells (hSCs). Heregulin is required for sustained hSC growth in vitro but must be thoroughly removed before cell collection for transplantation due to potential safety concerns. The goal of this study was to develop simple cell-based assays to assess the effectiveness of heregulin addition to and removal from aliquots of hSC culture medium. These bioassays were based on the capacity of a β1-heregulin peptide to elicit ErbB/HER receptor signaling in adherent ErbB2+/ErbB3+ cells.

Results

Western blotting was used to measure the activity of three different β1-heregulin/ErbB-activated kinases (ErbB3/HER3, ERK/MAPK and Akt/PKB) using phospho-specific antibodies against key activating residues. The duration, dose-dependency and specificity of β1-heregulin-initiated kinase phosphorylation were investigated, and controls were implemented for assay optimization and reproducibility to detect β1-heregulin activity in the nanomolar range. Results from these assays showed that the culture medium from transplantable hSCs elicited no detectable activation of the aforementioned kinases in independent rounds of testing, indicating that the implemented measures can ensure that the final hSC product is devoid of bioactive β1-heregulin molecules prior to transplantation.

Conclusions

These assays may be valuable to detect impurities such as undefined soluble factors or factors for which other biochemical or biological assays are not yet available. Our workflow can be modified as necessary to determine the presence of ErbB/HER, ERK, and Akt activators other than β1-heregulin using native samples, such as fresh isolates from cell- or tissue extracts in addition to culture medium.

A fast and efficient method for isolating Schwann cells from sciatic nerves of neonatal mice

BACKGROUND

Schwann cells (SCs) isolation is one of the basic techniques for study of peripheral nervous system and peripheral neuropathy. A combined and effective method of isolating SCs from sciatic nerves of newborn mice with high yield and purity is still lacking.

NEW METHODS

Sciatic nerves from neonatal mice aged 3-5 days serve as the source of SCs. Removal of adjacent connective tissue and epineurium, treatment with arabinoside hydrochloride and differential cell detachment technique were applied to eliminate fibroblast contamination and increase the purity of SCs. Combined use of collagenase/dispase and trypsin was chosen to increase the yield of SCs. Culture dishes precoated with poly-l-lysine and laminin, culture medium supplemented with heregulin β-1 and forskolin, and reasonable cell seeding density were implemented to increase the growth and proliferation of cultured SCs. Immunostaining of S100β and p75 neurotrophin receptor was used to identify the purity of SCs.

RESULTS

Our method is able to obtain high-yield SCs with a purity of 90% within five days and a purity more than 99% within seven days from sciatic nerves of neonatal mice.

COMPARISON WITH EXISTING METHODS

Previous SCs isolation mostly focused on rats or adult mice and have a few limitations due to fibroblasts contamination, low yield and time-consuming. Our method permits SCs isolation from neonatal mice with a high yield and purity of primary SCs within 7 days.

CONCLUSION

We described a fast, efficient and step-by-step method of isolating SCs from sciatic nerves of neonatal mice with high yield and purity.

Nerve guidance conduit development for primary treatment of peripheral nerve transection injuries: A commercial perspective

Commercial nerve guidance conduits (NGCs) for repair of peripheral nerve discontinuities are of little use in gaps larger than 30 mm, and for smaller gaps they often fail to compete with the autografts that they are designed to replace. While recent research to develop new technologies for use in NGCs has produced many advanced designs with seemingly positive functional outcomes in animal models, these advances have not been translated into viable clinical products. While there have been many detailed reviews of the technologies available for creating NGCs, none of these have focussed on the requirements of the commercialisation process which are vital to ensure the translation of a technology from bench to clinic. Consideration of the factors essential for commercial viability, including regulatory clearance, reimbursement processes, manufacturability and scale up, and quality management early in the design process is vital in giving new technologies the best chance at achieving real-world impact. Here we have attempted to summarise the major components to consider during the development of emerging NGC technologies as a guide for those looking to develop new technology in this domain. We also examine a selection of the latest academic developments from the viewpoint of clinical translation, and discuss areas where we believe further work would be most likely to bring new NGC technologies to the clinic. STATEMENT OF SIGNIFICANCE: NGCs for peripheral nerve repairs represent an adaptable foundation with potential to incorporate modifications to improve nerve regeneration outcomes. In this review we outline the regulatory processes that functionally distinct NGCs may need to address and explore new modifications and the complications that may need to be addressed during the translation process from bench to clinic.

Piezo2 mechanosensitive ion channel is located to sensory neurons and nonneuronal cells in rat peripheral sensory pathway: implications in pain

ABSTRACT

Piezo2 mechanotransduction channel is a crucial mediator of sensory neurons for sensing and transducing touch, vibration, and proprioception. We here characterized Piezo2 expression and cell specificity in rat peripheral sensory pathway using a validated Piezo2 antibody. Immunohistochemistry using this antibody revealed Piezo2 expression in pan primary sensory neurons of dorsal root ganglia in naïve rats, which was actively transported along afferent axons to both central presynaptic terminals innervating the spinal dorsal horn (DH) and peripheral afferent terminals in the skin. Piezo2 immunoreactivity (IR) was also detected in the postsynaptic neurons of the DH and in the motor neurons of the ventral horn, but not in spinal glial fibrillary acidic protein-positive and Iba1-positive glia. Notably, Piezo2-IR was clearly identified in peripheral nonneuronal cells, including perineuronal glia, Schwann cells in the sciatic nerve and surrounding cutaneous afferent endings, as well as in skin epidermal Merkel cells and melanocytes. Immunoblots showed increased Piezo2 in dorsal root ganglia ipsilateral to plantar injection of complete Freund's adjuvant, and immunostaining revealed increased Piezo2-IR intensity in the DH ipsilateral to complete Freund's adjuvant injection. This elevation of DH Piezo2-IR was also evident in various neuropathic pain models and monosodium iodoacetate knee osteoarthritis pain model, compared with controls. We conclude that (1) the pan neuronal profile of Piezo2 expression suggests that Piezo2 may function extend beyond simply touch or proprioception mediated by large-sized low-threshold mechanosensitive primary sensory neurons; (2) Piezo2 may have functional roles involving sensory processing in the spinal cord, Schwann cells, and skin melanocytes; and (3) aberrant Piezo2 expression may contribute pain pathogenesis.

Human Schwann Cell Transplantation for Spinal Cord Injury: Prospects and Challenges in Translational Medicine

The benefits of transplanting cultured Schwann cells (SCs) for the treatment of spinal cord injury (SCI) have been systematically investigated in experimental animals since the early 1990s. Importantly, human SC (hSC) transplantation for SCI has advanced to clinical testing and safety has been established via clinical trials conducted in the USA and abroad. However, multiple barriers must be overcome to enable accessible and effective treatments for SCI patients. This review presents available information on hSC transplantation for SCI with the intention to uncover gaps in our knowledge and discuss areas for future development. To this end, we introduce the historical progression of the work that supports existing and prospective clinical initiatives and explain the reasons for the choice of hSCs while also addressing their limitations as cell therapy products. A search of the relevant literature revealed that rat SCs have served as a preclinical model of reference since the onset of investigations, and that hSC transplants are relatively understudied, possibly due to the sophisticated resources and expertise needed for the traditional processing of hSC cultures from human nerves. In turn, we reason that additional experimentation and a reexamination of the available data are needed to understand the therapeutic value of hSC transplants taking into consideration that the manufacturing of the hSCs themselves may require further development for extended uses in basic research and clinical settings.

Merlin-Deficient Schwann Cells Are More Susceptible to Radiation Injury than Normal Schwann Cells In Vitro

Objectives Vestibular schwannomas (VS) are intracranial tumors, which are caused by NF2 gene mutations that lead to loss of merlin protein. A treatment for VS is stereotactic radiosurgery, a form of radiation. To better understand the radiobiology of VS and radiation toxicity to adjacent structures, our main objectives were (1) investigate effects of single fraction (SF) radiation on viability, cytotoxicity, and apoptosis in normal Schwann cells (SCs) and merlin-deficient Schwann cells (MD-SCs) in vitro, and (2) analyze expression of double strand DNA breaks (γ-H2AX) and DNA repair protein Rad51 following irradiation.

Study Design This is a basic science study.

Setting This study is conducted in a research laboratory.

Participants Patients did not participate in this study.

Main Outcome Measures In irradiated normal SCs and MD-SCs (0–18 Gy), we measured (1) viability, cytotoxicity, and apoptosis using cell-based assays, and (2) percentage of cells with γ-H2AX and Rad51 on immunofluorescence.

Results A high percentage of irradiated MD-SCs expressed γ-H2AX, which may explain the dose-dependent losses in viability in rodent and human cell lines. In comparison, the viabilities of normal SCs were only compromised at higher doses of radiation (>12 Gy, human SCs), which may be related to less Rad51 repair. There were no further reductions in viability in human MD-SCs beyond 9 Gy, suggesting that <9 Gy may be insufficient to initiate maximal tumor control.

Conclusion The MD-SCs are more susceptible to radiation than normal SCs, in part through differential expression of γ-H2AX and Rad51. Understanding the radiobiology of MD-SCs and normal SCs is important for optimizing radiation protocols to maximize tumor control while limiting radiation toxicity in VS patients.

Adjustable conduits for guided peripheral nerve regeneration prepared from bi-zonal unidirectional and multidirectional laminar scaffold of type I collagen

Shortness of donor nerves has led to the development of nerve conduits that connect sectioned peripheral nerve stumps and help to prevent the formation of neuromas. Often, the standard diameters of these devices cannot be adapted at the time of surgery to the diameter of the nerve injured. In this work, scaffolds were developed to form filled nerve conduits with an inner matrix with unidirectional channels covered by a multidirectional pore zone. Collagen type I dispersions (5 mg/g and 8 mg/g) were sequentially frozen using different methods to obtain six laminar scaffolds (P1 to P5) formed by a unidirectional (U) pore/channel zone adjacent to a multidirectional (M) pore zone. The physicochemical and microstructural properties of the scaffolds were determined and compared, as well as their biodegradability, residual glutaraldehyde and cytocompatibility. Also, the Young's modulus of the conduits made by rolling up the bizonal scaffolds from the unidirectional to the multidirectional zone was determined. Based on these comparisons, the proliferation and differentiation of hASC were assessed only in the P3 scaffolds. The cells adhered, aligned in the same direction as the unidirectional porous fibers, proliferated, and differentiated into Schwann-like cells. Adjustable conduits made with the P3 scaffold were implanted in rats 10 mm sciatic nerve lesions to compare their performance with that of autologous sciatic nerve grafted lesions. The in vivo results demonstrated that the tested conduit can be adapted to the diameter of the nerve stumps to guide their growth and promote their regeneration.

SDF-1α gene-activated collagen scaffold drives functional differentiation of human Schwann cells for wound healing applications

Enhancing angiogenesis is the prime target of current biomaterial-based wound healing strategies. However, these approaches largely overlook the angiogenic role of the cells of the nervous system. Therefore, we explored the role of a collagen-chondroitin sulfate scaffold functionalized with a proangiogenic gene stromal-derived factor-1α (SDF-1α)-an SDF-1α gene-activated scaffold on the functional regulation of human Schwann cells (SCs). A preliminary 2D study was conducted by delivering plasmids encoding for the SDF-1α gene into a monolayer of SCs using polyethyleneimine-based nanoparticles. The delivery of the SDF-1α gene into the SCs enhanced the production of proangiogenic vascular endothelial growth factor (VEGF). Subsequently, we investigated the impact of SDF-1α gene-activated scaffold (3D) on the SCs for 2 weeks, using a gene-free scaffold as control. The transfection of the SCs within the gene-activated scaffold resulted in transient overexpression of SDF-1α transcripts and triggered the production of bioactive VEGF that enhanced endothelial angiogenesis. The overexpression of SDF-1α also caused transient activation of the transcription factor c-Jun and supported the differentiation of SCs towards a repair phenotype. This was characterized by elevated expression of neurotrophin receptor p75NGFR. During this developmental stage, the SCs also performed an extensive remodelling of the basement matrix (fibronectin, collagen IV, and laminin) to enrich their environment with the pro-neurogenic matrix protein laminin, revealing an enhanced pro-neurogenic behavior. Together, this study shows that SDF-1α gene-activated scaffold is a highly bioinstructive scaffold capable of enhancing proangiogenic regenerative response in human SCs for improved wound healing.

Magnetic separation of peripheral nerve-resident cells underscores key molecular features of human Schwann cells and fibroblasts: an immunochemical and transcriptomics approach

Nerve-derived human Schwann cell (SC) cultures are irreplaceable models for basic and translational research but their use can be limited due to the risk of fibroblast overgrowth. Fibroblasts are an ill-defined population consisting of highly proliferative cells that, contrary to human SCs, do not undergo senescence in culture. We initiated this study by performing an exhaustive immunological and functional characterization of adult nerve-derived human SCs and fibroblasts to reveal their properties and optimize a protocol of magnetic-activated cell sorting (MACS) to separate them effectively both as viable and biologically competent cells. We next used immunofluorescence microscopy imaging, flow cytometry analysis and next generation RNA sequencing (RNA-seq) to unambiguously characterize the post-MACS cell products. High resolution transcriptome profiling revealed the identity of key lineage-specific transcripts and the clearly distinct neural crest and mesenchymal origin of human SCs and fibroblasts, respectively. Our analysis underscored a progenitor- or stem cell-like molecular phenotype in SCs and fibroblasts and the heterogeneity of the fibroblast populations. In addition, pathway analysis of RNA-seq data highlighted putative bidirectional networks of fibroblast-to-SC signaling that predict a complementary, yet seemingly independent contribution of SCs and fibroblasts to nerve regeneration. In sum, combining MACS with immunochemical and transcriptomics approaches provides an ideal workflow to exhaustively assess the identity, the stage of differentiation and functional features of highly purified cells from human peripheral nerve tissues.

Schwann Cell-Like Cells: Origin and Usability for Repair and Regeneration of the Peripheral and Central Nervous System

Functional recovery after neurotmesis, a complete transection of the nerve fiber, is often poor and requires a surgical procedure. Especially for longer gaps (>3 mm), end-to-end suturing of the proximal to the distal part is not possible, thus requiring nerve graft implantation. Artificial nerve grafts, i.e., hollow fibers, hydrogels, chitosan, collagen conduits, and decellularized scaffolds hold promise provided that these structures are populated with Schwann cells (SC) that are widely accepted to promote peripheral and spinal cord regeneration. However, these cells must be collected from the healthy peripheral nerves, resulting in significant time delay for treatment and undesired morbidities for the donors. Therefore, there is a clear need to explore the viable source of cells with a regenerative potential similar to SC. For this, we analyzed the literature for the generation of Schwann cell-like cells (SCLC) from stem cells of different origins (i.e., mesenchymal stem cells, pluripotent stem cells, and genetically programmed somatic cells) and compared their biological performance to promote axonal regeneration. Thus, the present review accounts for current developments in the field of SCLC differentiation, their applications in peripheral and central nervous system injury, and provides insights for future strategies.

Thrombomodulin facilitates peripheral nerve regeneration through regulating M1/M2 switching

Background

Excessive inflammation within damaged tissue usually leads to delayed or insufficient regeneration, and nerves in the peripheral nervous system (PNS) generally do not recover fully following damage. Consequently, there is growing interest in whether modulation of the inflammatory response could help to promote nerve regeneration in the PNS. However, to date, there are no practical therapeutic strategies for manipulating inflammation after nerve injury. Thrombomodulin (TM) is a transmembrane glycoprotein containing five domains. The lectin-like domain of TM has the ability to suppress the inflammatory response. However, whether TM can modulate inflammation in the PNS during nerve regeneration has yet to be elucidated.

Methods

We investigated the role of TM in switching proinflammatory type 1 macrophages (M1) to anti-inflammatory type 2 macrophages (M2) in a human monocytic cell line (THP-1) and evaluated the therapeutic application of TM in transected sciatic nerve injury in rats.

Results

The administration of TM during M1 induction significantly reduced the expression levels of inflammatory cytokines, including TNF-a (p < 0.05), IL-6 (p < 0.05), and CD86 (p < 0.05), in THP-1 cells. Simultaneously, the expression levels of M2 markers, including IL-10 (p < 0.05) and CD206 (p < 0.05), were significantly increased in TM-treated THP-1 cells. Inhibition of IL-4R-c-Myc-pSTAT6-PPARγ signaling abolished the expression levels of IL-10 (p < 0.05) and CD206 (p < 0.05). The conditioned medium (CM) collected from M1 cells triggered an inflammatory response in primary Schwann cells, while CM collected from M1 cells treated with TM resulted in a dose-dependent reduction in inflammation. TM treatment led to better nerve regeneration when tested 6 weeks after injury and preserved effector muscle function. In addition, TM treatment reduced macrophage infiltration at the site of injury and led to potent M1 to M2 transition, thus indicating the anti-inflammatory capacity of TM.

Conclusions

Collectively, our findings demonstrate the anti-inflammatory role of TM during nerve regeneration. Therefore, TM represents a potential drug for the promotion and modulation of functional recovery in peripheral nerves that acts by regulating the M1/M2 ratio.

Schwann Cell Cultures: Biology, Technology and Therapeutics

Schwann cell (SC) cultures from experimental animals and human donors can be prepared using nearly any type of nerve at any stage of maturation to render stage- and patient-specific populations. Methods to isolate, purify, expand in number, and differentiate SCs from adult, postnatal and embryonic sources are efficient and reproducible as these have resulted from accumulated refinements introduced over many decades of work. Albeit some exceptions, SCs can be passaged extensively while maintaining their normal proliferation and differentiation controls. Due to their lineage commitment and strong resistance to tumorigenic transformation, SCs are safe for use in therapeutic approaches in the peripheral and central nervous systems. This review summarizes the evolution of work that led to the robust technologies used today in SC culturing along with the main features of the primary and expanded SCs that make them irreplaceable models to understand SC biology in health and disease. Traditional and emerging approaches in SC culture are discussed in light of their prospective applications. Lastly, some basic assumptions in vitro SC models are identified in an attempt to uncover the combined value of old and new trends in culture protocols and the cellular products that are derived.

MicroRNA-124 Overexpression in Schwann Cells Promotes Schwann Cell-Astrocyte Integration and Inhibits Glial Scar Formation Ability

Schwann cell (SC) transplantation is a promising approach for the treatment of spinal cord injury (SCI); however, SC grafts show a low migratory capacity within the astrocytic environment, which inevitably hampers their therapeutic efficacy. The purpose of this study was to explore mechanisms to modify the characteristics of SCs and astrocytes (ASs), as well as to adjust the SC-AS interface to break the SC-AS boundary, thus improving the benefits of SCI treatment. We observed that the expression levels of miR-124 in SCs and ASs were significantly lower than those in the normal spinal cord. Furthermore, overexpressing miR-124 in SCs (miR-124-SCs) significantly inhibited gene and protein expression levels of SC-specific markers, such as GFAP and Krox20. The expression of neurotrophic factors, Bdnf and Nt-3, was up-regulated in miR-124-SCs without affecting their proliferation. Further, the boundary assay showed an increased number of miR-124-SCs that had actively migrated and entered the astrocytic region to intermingle with ASs, compared with normal SCs. In addition, although Krox20 protein expression was down-regulated in miR-124-SCs, the luciferase assay showed that Krox20 is not a direct target of miR-124. RNA sequencing of miR-124-SCs revealed seven upregulated and eleven downregulated genes involved in cell migration and motility. Based on KEGG pathway and KOG functional analyses, changes in these genes corresponded to the activation of Hippo, FoxO, and TGF-beta signaling pathways, cytokine-cytokine receptor interactions, and the cell cycle. Finally, co-culturing of miR-124-SCs and ASs in a transwell system revealed that GFAP and p-STAT3 protein expression in ASs was significantly reduced. Collectively, these results show that overexpression of miR-124 in SCs promotes SC-AS integration in vitro and may attenuate the capacity of ASs to form glial scars. Thus, this study provides novel insights into modifying SCs by overexpressing miR-124 to improve their therapeutic potential in SCI.

Automated image analysis of stained cytospins to quantify Schwann cell purity and proliferation

In response to injury, adult Schwann cells (SCs) re-enter the cell cycle, change their expression profile, and exert repair functions important for wound healing and the re-growth of axons. While this phenotypical instability of SCs is essential for nerve regeneration, it has also been implicated in cancer progression and de-myelinating neuropathies. Thus, SCs became an important research tool to study the molecular mechanisms involved in repair and disease and to identify targets for therapeutic intervention. A high purity of isolated SC cultures used for experimentation must be demonstrated to exclude that novel findings are derived from a contaminating fibroblasts population. In addition, information about the SC proliferation status is an important parameter to be determined in response to different treatments. The evaluation of SC purity and proliferation, however, usually depends on the time consuming, manual assessment of immunofluorescence stainings or comes with the sacrifice of a large amount of SCs for flow cytometry analysis. We here show that rat SC culture derived cytospins stained for SC marker SOX10, proliferation marker EdU, intermediate filament vimentin and DAPI allowed the determination of SC identity and proliferation by requiring only a small number of cells. Furthermore, the CellProfiler software was used to develop an automated image analysis pipeline that quantified SCs and proliferating SCs from the obtained immunofluorescence images. By comparing the results of total cell count, SC purity and SC proliferation rate between manual counting and the CellProfiler output, we demonstrated applicability and reliability of the established pipeline. In conclusion, we here combined the cytospin technique, a multi-colour immunofluorescence staining panel, and an automated image analysis pipeline to enable the quantification of SC purity and SC proliferation from small cell aliquots. This procedure represents a solid read-out to simplify and standardize the quantification of primary SC culture purity and proliferation.

Immunomodulatory and anti-oxidative effect of the direct TRPV1 receptor agonist capsaicin on Schwann cells

Background

Only few studies describe the impact of nutritive factors on chronic inflammatory demyelinating polyneuropathy (CIDP), an inflammatory disease of the peripheral nervous system. The active component of chili pepper, capsaicin, is the direct agonist of the transient receptor potential channel vanilloid subfamily member 1. Its anti-inflammatory effect in the animal model experimental autoimmune neuritis (EAN) has been previously demonstrated.

Methods

In the present study, we describe the anti-inflammatory and anti-oxidative influence of capsaicin on Schwann cells (SCs) in an in vitro setting. Hereby, we analyze the effect of capsaicin on Schwann cells’ gene expression pattern, major histocompatibility complex class II (MHC-II) presentation, and H₂O₂-induced oxidative stress. Furthermore, the effect of capsaicin on myelination was examined in a SC-dorsal root ganglia (DRG) coculture by myelin basic protein staining. Finally, in order to investigate the isolated effect of capsaicin on SCs in EAN pathology, we transplant naïve and capsaicin pre-treated SCs intrathecally in EAN immunized rats and analyzed clinical presentation, electrophysiological parameters, and cytokine expression in the sciatic nerve.

Results

In SC monoculture, incubation with capsaicin significantly reduces interferon gamma-induced MHC-II production as well as toll-like receptor 4 and intercellular adhesion molecule 1 mRNA expression. Calcitonin gene-related peptide mRNA production is significantly upregulated after capsaicin treatment. Capsaicin reduces H₂O₂-induced oxidative stress in SC in a preventive, but not therapeutic setting. In a SC-DRG coculture, capsaicin does not affect myelination rate. After intrathecal transplantation of naïve and capsaicin pre-treated SCs in EAN-immunized rats, naïve, but not capsaicin pre-treated intrathecal SCs, ameliorated EAN pathology in rats.

Conclusions

In conclusion, we were able to demonstrate a direct immunomodulatory and anti-oxidative effect of capsaicin in a SC culture by reduced antigen presentation and expression of an anti-inflammatory profile. Furthermore, capsaicin increases the resistance of SCs against oxidative stress. A primary effect of capsaicin on myelination was not proven. These results are in concordance with previous data showing an anti-inflammatory effect of capsaicin, which might be highly relevant for CIDP patients.

Co-overexpression of VEGF and GDNF in adipose-derived stem cells optimizes therapeutic effect in neurogenic erectile dysfunction model

Objectives

To evaluate the rapid repair potential of adipose‐derived stem cells (ADSCs) co‐overexpressing VEGF and GDNF on bilateral cavernous nerve injury (BCNI) in rat models. Progressive fibrosis of the penis that occurs shortly after BCNI is a key cause of clinical treatment difficulty of erectile dysfunction (ED). Traditional medications are ineffective for ED caused by BCNI. ADSCs have shown therapeutic effects in animal models, but disappointing in clinical treatment suggests that we should explore optimal treatment of it.

Materials and methods

We extracted ADSCs from rat epididymis. Lentiviral transfection was verified by western blot and immunofluorescence. Thirty‐six SD rats (10 weeks old) were randomly divided into six groups (n = 6 per group): sham surgery, and remaining five BCNI groups transplanted PBS or ADSCs which were genetically modified by vehicle, VEGF (ADSC‐V), GDNF (ADSC‐G), or VEGF&GDNF (ADSC‐G&V) around major pelvic ganglion (MPG). We investigated the therapeutic effects of BCNI rat model which is characterized by ED, penile tissue fibrosis and hypoxia, and lack of nitrogen nerves or vascular atrophy.

Results

Erectile function was almost recovered after 2 weeks of transplantation of ADSC‐G&V, promoted cavernous nerve repair, prevented penile fibrosis and preserving the vascular endothelium, which was significant differences amongst ADSC‐V or ADSC‐G. Moreover, GM‐ADSCs were detected in MPG and penis, indicating that their participation in repair of target organs and transverse nerves.

Conclusions

These promising data indicate that ADSCs co‐overexpressed VEGF and GDNF‐induced synergistic effects, make it a potential tool for recovering of erectile function speedily after BCNI.

Fluorescent Detection of Merlin-deficient Schwann Cells and Primary Human Vestibular Schwannoma Cells Using Sodium Fluorescein

HYPOTHESIS

Merlin-deficient Schwann cells (MD-SC) and primary human vestibular schwannoma (VS) cells exhibit selective uptake of sodium-fluorescein (SF), allowing for fluorescent detection and improved visualization of tumor cells, when compared with Schwann cells (SC).

BACKGROUND

SF is a fluorescent compound used for fluorescence-guided resection of gliomas. The utility of SF for VS surgery has not been assessed.

METHODS

Mouse MD-SCs and rat SCs were cultured on 96-well plates at different cell densities and treated with SF at several drug concentrations and durations. Relative fluorescence units (RFU) were measured using a fluorometer to determine optimal treatment parameters in vitro. Subsequently, a four-point Likert scale for fluorescence visualization of pelleted cells was created and validated. Blinded observers rated SF-treated primary human VS and SC cultures, which were developed from deidentified specimens obtained from live and cadaveric donors, respectively.

RESULTS

In contrast to SCs that showed low levels of fluorescence, MD-SCs demonstrated dose-dependent increases in RFUs when treated with incremental dosages of SF as well as longer treatment and fluorescent excitation times. In addition, RFUs were higher at greater MD-SC densities. The Likert scale for fluorescence visualization was validated using nine blinded observers and there were excellent inter- and intrarater reliabilities (intraclass coefficients of 0.989 and >0.858, respectively). Using the Likert scale, human VS treated with SF received higher scores than human SCs (p < 0.001).

CONCLUSION

Mouse MD-SC and human VS cells demonstrate preferential uptake of SF when compared with normal primary SCs. Observers detected differences in fluorescence using the validated Likert scale. Further investigations into the utility of SF-guidance in VS surgery are warranted.

Laminin-coated electrodes improve cochlear implant function and post-insertion neuronal survival

The benefits of Cochlear implant (CI) technology depend among other factors on the proximity of the electrode array to the spiral ganglion neurons. Laminin, a component of the extracellular matrix, regulates Schwann cell proliferation and survival as well as reorganization of actin fibers within their cytoskeleton, which is necessary for myelination of peripheral axons. In this study we explore the effectiveness of laminin-coated electrodes in promoting neuritic outgrowth from auditory neurons towards the electrode array and the ability to reduce acoustic and electric auditory brainstem response (i.e. aABR and eABR) thresholds. In vitro: Schwann cells and neurites are attracted towards laminin-coated surfaces with longer neuritic processes in laminin-coated dishes compared to uncoated dishes. In vivo: Animals implanted with laminin-coated electrodes experience significant decreases in eABR and aABR thresholds at selected frequencies compared to the results from the uncoated electrodes group. At 1 month post implantation there were a greater number of spiral ganglion neurons and neuritic processes projecting into the scala tympani of animals implanted with laminin-coated electrodes compared to animals with uncoated electrodes. These data suggest that Schwann cells are attracted towards laminin-coated electrodes and promote neuritic outgrowth/ guidance and promote the survival of spiral ganglion neurons following electrode insertion trauma.

Cell and context-dependent sorting of neuropathy-associated protein NDRG1 - insights from canine tissues and primary Schwann cell cultures

BACKGROUND

Mutations in the N-myc downstream-regulated gene 1 (NDRG1) can cause degenerative polyneuropathy in humans, dogs, and rodents. In humans, this motor and sensory neuropathy is known as Charcot-Marie-Tooth disease type 4D, and it is assumed that analogous canine diseases can be used as models for this disease. NDRG1 is also regarded as a metastasis-suppressor in several malignancies. The tissue distribution of NDRG1 has been described in humans and rodents, but this has not been studied in the dog.

RESULTS

By immunolabeling and Western blotting, we present a detailed mapping of NDRG1 in dog tissues and primary canine Schwann cell cultures, with particular emphasis on peripheral nerves. High levels of phosphorylated NDRG1 appear in distinct subcellular localizations of the Schwann cells, suggesting signaling-driven rerouting of the protein. In a nerve from an Alaskan malamute homozygous for the disease-causing Gly98Val mutation in NDRG1, this signal was absent. Furthermore, NDRG1 is present in canine epithelial cells, predominantly in the cytosolic compartment, often with basolateral localization. Constitutive expression also occurs in mesenchymal cells, including developing spermatids that are transiently positive for NDRG1. In some cells, NDRG1 localize to centrosomes.

CONCLUSIONS

Overall, canine NDRG1 shows a cell and context-dependent localization. Our data from peripheral nerves and primary Schwann cell cultures suggest that the subcellular localization of NDRG1 in Schwann cells is dynamically influenced by signaling events leading to reversible phosphorylation of the protein. We propose that disease-causing mutations in NDRG1 can disrupt signaling in myelinating Schwann cells, causing disturbance in myelin homeostasis and axonal-glial cross talk, thereby precipitating polyneuropathy.

Intrathecal triamcinolone acetonide exerts anti-inflammatory effects on Lewis rat experimental autoimmune neuritis and direct anti-oxidative effects on Schwann cells

Background

Corticosteroids dominate in the treatment of chronic autoimmune neuropathies although long-term use is characterized by devastating side effects.

Methods

We introduce the intrathecal application of the synthetic steroid triamcinolone (TRIAM) as a novel therapeutic option in experimental autoimmune neuritis in Lewis rats

Results

After immunization with neuritogenic P2 peptide, we show a dose-dependent therapeutic effect of one intrathecal injection of 0.3 or 0.6 mg/kg TRIAM on clinical and electrophysiological parameters of neuritis with a lower degree of inflammatory infiltrates (T cells and macrophages) and demyelination in the sciatic nerve. In vitro studies in Schwann cell cultures showed an increased expression of IL-1 receptor antagonist and reduced expression of Toll-like receptor 4 after incubation with TRIAM as well as a protective effect of TRIAM against oxidative stress after H₂O₂ exposure.

Conclusion

Intrathecal TRIAM application could be a novel immunomodulatory and potentially neuroprotective option for autoimmune neuropathies with a direct effect on Schwann cells.

Cryopreservation of Canine Primary Dorsal Root Ganglion Neurons and Its Impact upon Susceptibility to Paramyxovirus Infection

Canine dorsal root ganglion (DRG) neurons, isolated post mortem from adult dogs, could provide a promising tool to study neuropathogenesis of neurotropic virus infections with a non-rodent host spectrum. However, access to canine DRG is limited due to lack of donor tissue and the cryopreservation of DRG neurons would greatly facilitate experiments. The present study aimed (i) to establish canine DRG neurons as an in vitro model for canine distemper virus (CDV) infection; and (ii) to determine whether DRG neurons are cryopreservable and remain infectable with CDV. Neurons were characterized morphologically and phenotypically by light microscopy, immunofluorescence, and functionally, by studying their neurite outgrowth and infectability with CDV. Cryopreserved canine DRG neurons remained in culture for at least 12 days. Furthermore, both non-cryopreserved and cryopreserved DRG neurons were susceptible to infection with two different strains of CDV, albeit only one of the two strains (CDV R252) provided sufficient absolute numbers of infected neurons. However, cryopreserved DRG neurons showed reduced cell yield, neurite outgrowth, neurite branching, and soma size and reduced susceptibility to CDV infection. In conclusion, canine primary DRG neurons represent a suitable tool for investigations upon the pathogenesis of neuronal CDV infection. Moreover, despite certain limitations, cryopreserved canine DRG neurons generally provide a useful and practicable alternative to address questions regarding virus tropism and neuropathogenesis.

Scalable Differentiation and Dedifferentiation Assays Using Neuron-Free Schwann Cell Cultures

This chapter describes protocols to establish simplified in vitro assays of Schwann cell (SC) differentiation in the absence of neurons. The assays are based on the capacity of isolated primary SCs to increase or decrease the expression of myelination-associated genes in response to the presence or absence of cell permeable analogs of cyclic adenosine monophosphate (cAMP). No special conditions of media or substrates beyond the administration or removal of cAMP analogs are required to obtain a synchronous response on differentiation and dedifferentiation. The assays are cost-effective and far easier to implement than traditional myelinating SC-neuron cultures. They are scalable to a variety of plate formats suited for downstream experimentation and analysis. These cell-based assays can be used as drug discovery platforms for the evaluation of novel agents controlling the onset, maintenance, and reversal of the differentiated state using any typical adherent SC population.

Effect of Exosomes from Rat Adipose-Derived Mesenchymal Stem Cells on Neurite Outgrowth and Sciatic Nerve Regeneration After Crush Injury

Peripheral nerve injury requires optimal conditions in both macro-environment and microenvironment for promotion of axonal regeneration. However, most repair strategies of traumatic peripheral nerve injury often lead to dissatisfying results in clinical outcome. Though various strategies have been carried out to improve the macro-environment, the underlying molecular mechanism of axon regeneration in the microenvironment provided by nerve conduit remains unclear. In this study, we evaluate the effects of from adipose-derived mesenchymal stem cells (adMSCs) originating exosomes with respect to sciatic nerve regeneration and neurite growth. Molecular and immunohistochemical techniques were used to investigate the presence of characteristic exosome markers. A co-culture system was established to determine the effect of exosomes on neurite elongation in vitro. The in vivo walking behaviour of rats was evaluated by footprint analysis, and the nerve regeneration was assessed by immunocytochemistry. adMSCs secrete nano-vesicles known as exosomes, which increase neurite outgrowth in vitro and enhance regeneration after sciatic nerve injury in vivo. Furthermore, we showed the presence of neural growth factors transcripts in adMSC exosomes for the first time. Our results demonstrate that exosomes, constitutively produced by adMSCs, are involved in peripheral nerve regeneration and have the potential to be utilised as a therapeutic tool for effective tissue-engineered nerves.

Phenotypic and Functional Characteristics of Human Schwann Cells as Revealed by Cell-Based Assays and RNA-SEQ

This study comprehensively addresses the phenotype, function, and whole transcriptome of primary human and rodent Schwann cells (SCs) and highlights key species-specific features beyond the expected donor variability that account for the differential ability of human SCs to proliferate, differentiate, and interact with axons in vitro. Contrary to rat SCs, human SCs were insensitive to mitogenic factors other than neuregulin and presented phenotypic variants at various stages of differentiation, along with a mixture of proliferating and senescent cells, under optimal growth-promoting conditions. The responses of human SCs to cAMP-induced differentiation featured morphological changes and cell cycle exit without a concomitant increase in myelin-related proteins and lipids. Human SCs efficiently extended processes along those of other SCs (human or rat) but failed to do so when placed in co-culture with sensory neurons under conditions supportive of myelination. Indeed, axon contact-dependent human SC alignment, proliferation, and differentiation were not observed and could not be overcome by growth factor supplementation. Strikingly, RNA-seq data revealed that ~ 44 of the transcriptome contained differentially expressed genes in human and rat SCs. A bioinformatics approach further highlighted that representative SC-specific transcripts encoding myelin-related and axon growth-promoting proteins were significantly affected and that a deficient expression of key transducers of cAMP and adhesion signaling explained the fairly limited potential of human SCs to differentiate and respond to axonal cues. These results confirmed the significance of combining traditional bioassays and high-resolution genomics methods to characterize human SCs and identify genes predictive of cell function and therapeutic value.

Magnetic-Activated Cell Sorting for the Fast and Efficient Separation of Human and Rodent Schwann Cells from Mixed Cell Populations

To date, magnetic-activated cell sorting (MACS) remains a powerful method to isolate distinct cell populations based on differential cell surface labeling. Optimized direct and indirect MACS protocols for cell immunolabeling are presented here as methods to divest Schwann cell (SC) cultures of contaminating cells (specifically, fibroblast cells) and isolate SC populations at different stages of differentiation. This chapter describes (1) the preparation of single-cell suspensions from established human and rat SC cultures, (2) the design and application of cell selection strategies using SC-specific (p75^NGFR, O4, and O1) and fibroblast-specific (Thy-1) markers, and (3) the characterization of both the pre- and post-sorting cell populations. A simple protocol for the growth of hybridoma cell cultures as a source of monoclonal antibodies for cell surface immunolabeling of SCs and fibroblasts is provided as a cost-effective alternative for commercially available products. These steps allow for the timely and efficient recovery of purified SC populations without compromising the viability and biological activity of the cells.

Isolation, Culture, and Cryopreservation of Adult Rodent Schwann Cells Derived from Immediately Dissociated Teased Fibers

Adult Schwann cell (SC) cultures are usually derived from nerves subjected to a lengthy step of pre-degeneration to facilitate enzymatic digestion and recovery of viable cells. To overcome the need for pre-degeneration, we developed a method that allows the isolation of adult rat sciatic nerve SCs immediately after tissue harvesting. This method combines the advantages of implementing a rapid enzymatic dissociation of the nerve fibers and a straightforward separation of cells versus myelin that improves both cell yield and viability. Essentially, the method consists of (1) acute dissociation with collagenase and dispase immediately after removal of the epineurium layer and extensive teasing of the nerve fibers, (2) removal of myelin debris by selective attachment of the cells to a highly adhesive poly-L-lysine/laminin substrate, (3) expansion of the initial SC population in medium containing chemical mitogens, and (4) preparation of cryogenic stocks for transfer or delayed experimentation. This protocol allows for the procurement of homogeneous SC cultures deprived of myelin and fibroblast growth as soon as 3-4 days after nerve tissue dissection. SC cultures can be used as such for experimentation or subjected to consecutive rounds of expansion prior to use, purification, or cryopreservation.

Detailed Protocols for the Isolation, Culture, Enrichment and Immunostaining of Primary Human Schwann Cells

This chapter emphasizes detailed protocols for the effective establishment of highly enriched human Schwann cell cultures and their characterization via immunostaining. The Schwann cells are isolated from immediately dissociated fascicle tissue and expanded prior to purification. Two purification methods are described that use either fluorescence-activated cell sorting for the Schwann cell marker TNR16 (p75^NTR) or a less-manipulative two-step enrichment exploiting the differential adhesion properties of Schwann cells and fibroblasts, which is especially useful for low Schwann cell numbers. In addition, a method to determine Schwann cell purity via stained cytospin slides is introduced. Together with an immunofluorescence staining procedure for the combined analysis of extra- and intracellular markers, this chapter provides a solid basis to study human primary Schwann cells.

Axon contact-driven Schwann cell dedifferentiation

Mature Schwann cells (SCs) retain dedifferentiation potential throughout adulthood. Still, how dedifferentiation occurs remains uncertain. Results from a variety of cell-based assays using in vitro cultured cAMP-differentiated and myelinating SCs revealed the existence of a novel dedifferentiating activity expressed on the surface of dorsal root ganglion (DRG) axons. This activity had the capacity to prevent SC differentiation and elicit dedifferentiation through direct SC-axon contact. Evidence is provided showing that a rapid loss of myelinating SC markers concomitant to proliferation occurred even in the presence of elevated cAMP, a signal that is required to drive and maintain a differentiated state. The dedifferentiating activity was a membrane-bound protein found exclusively in DRG neurons, as judged by its subcellular partitioning, sensitivity to proteolytic degradation and cell-type specificity, and remained active even after disruption of cellular organization. It differed from the membrane-anchored neuregulin-1 isoforms that are responsible for axon contact-induced SC proliferation and exerted its action independently of mitogenic signaling emanating from receptor tyrosine kinases and mitogen-activated protein kinases such as ERK and JNK. Interestingly, dedifferentiation occurred without concomitant changes in the expression of Krox-20, a transcriptional enhancer of myelination, and c-Jun, an inhibitor of myelination. In sum, our data indicated the existence of cell surface axon-derived signals that override pro-differentiating cues, drive dedifferentiation and allow SCs to proliferate in response to axonal mitogens. This axonal signal may negatively regulate myelination at the onset or reversal of the differentiated state. GLIA 2017;65:851-863.