Schwann Cell Progenitors Research Articles

MiRNA-21-5p is an important contributor to the promotion of injured peripheral nerve regeneration using hypoxia-pretreated bone marrow-derived neural crest cells.

JOURNAL/nrgr/04.03/01300535-202501000-00035/figure1/v/2024-05-14T021156Z/r/image-tiff Our previous study found that rat bone marrow-derived neural crest cells (acting as Schwann cell progenitors) have the potential to promote long-distance nerve repair. Cell-based therapy can enhance peripheral nerve repair and regeneration through paracrine bioactive factors and intercellular communication. Nevertheless, the complex contributions of various types of soluble cytokines and extracellular vesicle cargos to the secretome remain unclear. To investigate the role of the secretome and extracellular vesicles in repairing damaged peripheral nerves, we collected conditioned culture medium from hypoxia-pretreated neural crest cells, and found that it significantly promoted the repair of sensory neurons damaged by oxygen-glucose deprivation. The mRNA expression of trophic factors was highly expressed in hypoxia-pretreated neural crest cells. We performed RNA sequencing and bioinformatics analysis and found that miR-21-5p was enriched in hypoxia-pretreated extracellular vesicles of neural crest cells. Subsequently, to further clarify the role of hypoxia-pretreated neural crest cell extracellular vesicles rich in miR-21-5p in axonal growth and regeneration of sensory neurons, we used a microfluidic axonal dissociation model of sensory neurons in vitro, and found that hypoxia-pretreated neural crest cell extracellular vesicles promoted axonal growth and regeneration of sensory neurons, which was greatly dependent on loaded miR-21-5p. Finally, we constructed a miR-21-5p-loaded neural conduit to repair the sciatic nerve defect in rats and found that the motor and sensory functions of injured rat hind limb, as well as muscle tissue morphology of the hind limbs, were obviously restored. These findings suggest that hypoxia-pretreated neural crest extracellular vesicles are natural nanoparticles rich in miRNA-21-5p. miRNA-21-5p is one of the main contributors to promoting nerve regeneration by the neural crest cell secretome. This helps to explain the mechanism of action of the secretome and extracellular vesicles of neural crest cells in repairing damaged peripheral nerves, and also promotes the application of miR-21-5p in tissue engineering regeneration medicine.

A topographic atlas defines developmental origins of cell heterogeneity in the human embryonic lung

The lung contains numerous specialized cell types with distinct roles in tissue function and integrity. To clarify the origins and mechanisms generating cell heterogeneity, we created a comprehensive topographic atlas of early human lung development. Here we report 83 cell states and several spatially resolved developmental trajectories and predict cell interactions within defined tissue niches. We integrated single-cell RNA sequencing and spatially resolved transcriptomics into a web-based, open platform for interactive exploration. We show distinct gene expression programmes, accompanying sequential events of cell differentiation and maturation of the secretory and neuroendocrine cell types in proximal epithelium. We define the origin of airway fibroblasts associated with airway smooth muscle in bronchovascular bundles and describe a trajectory of Schwann cell progenitors to intrinsic parasympathetic neurons controlling bronchoconstriction. Our atlas provides a rich resource for further research and a reference for defining deviations from homeostatic and repair mechanisms leading to pulmonary diseases.

Peripheral Nerve Regeneration with 3D Printed Bionic Scaffolds Loading Neural Crest Stem Cell Derived Schwann Cell Progenitors

AbstractPeripheral nerve injuries are one of the most common types of traumatic damage to the nervous system. Treatment of peripheral nerve injuries aims to promote axon regrowth by imitating and improving the microenvironment for sciatic nerve regeneration. In this study, regeneration efficiency and behavior of peripheral nerves are compared under three treatment strategies: 1) transplantation of Schwann cell progenitors induced from purified neural crest stem cells; 2) implantation of a multiscale scaffold based on high‐resolution 3D printing; and 3) implantation of this bionic scaffold loading Schwann cell progenitors. The results of structural, electrophysiological, and behavioral tests demonstrate that the three treatment strategies result in different degrees of regeneration. The purified neural crest stem cells differentiate into functional Schwann cells and promote axon regeneration. The multifunctional 3D printed scaffold promotes oriented growth and myelination, and the myelinated nerve regrows with increased density and without visible scaffolds after six months. For the regeneration, scaffold treatment produces better performance than cell graft alone. Finally, it is shown that implantation of multiscale scaffolds preloaded with neural crest stem cell derived Schwann cell progenitors is the best strategy to promote peripheral nerve regeneration with improved anatomy and function among the three different strategies.

Neurons populating the rectal extrinsic nerves in humans express neuronal and Schwann cell markers

AbstractBackgroundIn mice, Schwann cell (SC) progenitors give rise to autonomic ganglion cells and migrate into the gut to become enteric neurons. It is unknown whether SC progenitors have a similar fate in humans. In search of evidence for human SC‐derived neurogenesis in the gastrointestinal (GI) tract, we studied the rectums from cadaveric controls and children with anorectal malformations (ARM).MethodsWe analyzed distal rectal tissue taken at autopsy from 10 children with normal GI tracts and resected rectal specimens in 48 cases of ARM. Of these specimens, 6 had neurons within the extrinsic rectal innervation. These were further investigated with immunohistochemistry for neuronal and SC/glial markers.Key ResultsPerirectal tissue from control and ARM contained GLUT1‐positive extrinsic nerves, many containing neurons. SC/glial markers (SOX10, CDH19, and PLP1) were expressed by glia in the enteric nervous system and perirectal nerves, while MPZ predominated only in glia of perirectal nerves, in both control and ARM. Neurons in perirectal nerves were 61% larger in ARM samples and co‐expressed SOX10 (81%), PLP1 (73%), and CDH19 (56%). In ARM, cytoplasmic SOX10 was co‐expressed with neuronal antigens in ~57% of submucosal and myenteric neurons, vs. ~3% in control. Furthermore, intrinsic gut neurons in ARM specimens co‐expressed PLP1 (18%) and CDH19 (18%); however, neuronal co‐expression of PLP1 and CDH19 was rarely (<2%) observed in controls.Conclusions & InferencesDual expression of glial and neuronal markers in rectal and perirectal neurons support a model of Schwann cell‐derived neurogenesis in the innervation of the human GI tract.

New evidence for secondary axonal degeneration in demyelinating neuropathies

Development of peripheral nervous system (PNS) myelin involves a coordinated series of events between growing axons and the Schwann cell (SC) progenitors that will eventually ensheath them. Myelin sheaths have evolved out of necessity to maintain rapid impulse propagation while accounting for body space constraints. However, myelinating SCs perform additional critical functions that are required to preserve axonal integrity including mitigating energy consumption by establishing the nodal architecture, regulating axon caliber by organizing axonal cytoskeleton networks, providing trophic and potentially metabolic support, possibly supplying genetic translation materials and protecting axons from toxic insults. The intermediate steps between the loss of these functions and the initiation of axon degeneration are unknown but the importance of these processes provides insightful clues. Prevalent demyelinating diseases of the PNS include the inherited neuropathies Charcot-Marie-Tooth Disease, Type 1 (CMT1) and Hereditary Neuropathy with Liability to Pressure Palsies (HNPP) and the inflammatory diseases Acute Inflammatory Demyelinating Polyneuropathy (AIDP) and Chronic Inflammatory Demyelinating Polyneuropathy (CIDP). Secondary axon degeneration is a common feature of demyelinating neuropathies and this process is often correlated with clinical deficits and long-lasting disability in patients. There is abundant electrophysiological and histological evidence for secondary axon degeneration in patients and rodent models of PNS demyelinating diseases. Fully understanding the involvement of secondary axon degeneration in these diseases is essential for expanding our knowledge of disease pathogenesis and prognosis, which will be essential for developing novel therapeutic strategies.

Dissecting the Functional Reprogramming of the Microenvironment in Bone Marrow Fibrosis at the Single Cell Level

Functional contributions of individual members of the bone marrow microenvironment to myelofibrosis (MF) in patients with myeloproliferative neoplasms (MPN) are incompletely understood. Consequently, we aimed to generate a comprehensive map of the stroma in MPN/MF on a single cell level. Our analysis revealed two distinct mesenchymal stromal cells (MSC) subsets as pro-fibrotic cells. MSCs were functionally reprogrammed in a stage-dependent manner with loss of their progenitor status and initiation of differentiation in the pre-fibrotic stage and acquisition of a pro-fibrotic and inflammatory phenotype in the fibrotic stage. In parallel, IL-33-expressing myelinating Schwann cell progenitors expanded, likely as a repair mechanism for the previously described neuropathy in MPN. IL-33 had anti-fibrotic effects on MSCs but induced expression of the alarmin S100A8 leading to loss-of-hematopoiesis support. Importantly, we demonstrate that S100A8 expression in stroma and patient plasma marks fibrosis progression and might even serve as a biomarker for disease progression.

The TSC1-mTOR-PLK axis regulates the homeostatic switch from Schwann cell proliferation to myelination in a stage-specific manner.

Proper peripheral myelination depends upon the balance between Schwann cell proliferation and differentiation programs. The serine/threonine kinase mTOR integrates various environmental cues to serve as a central regulator of cell growth, metabolism, and function. We report here that tuberous sclerosis complex 1 (TSC1), a negative regulator of mTOR activity, establishes a stage-dependent program for Schwann cell lineage progression and myelination by controlling cell proliferation and myelin homeostasis. Tsc1 ablation in Schwann cell progenitors in mice resulted in activation of mTOR signaling, and caused over-proliferation of Schwann cells and blocked their differentiation, leading to hypomyelination. Transcriptome profiling analysis revealed that mTOR activation in Tsc1 mutants resulted in upregulation of a polo-like kinase (PLK)-dependent pathway and cell cycle regulators. Attenuation of mTOR or pharmacological inhibition of polo-like kinases partially rescued hypomyelination caused by Tsc1 loss in the developing peripheral nerves. In contrast, deletion of Tsc1 in mature Schwann cells led to redundant and overgrown myelin sheaths in adult mice. Together, our findings indicate stage-specific functions for the TSC1-mTOR-PLK signaling axis in controlling the transition from proliferation to differentiation and myelin homeostasis during Schwann cell development.

KIR2DL5 mutation and loss underlies sporadic dermal neurofibroma pathogenesis and growth.

Dermal neurofibromas (DNFs) are benign peripheral nerve sheath tumors thought to originate from Schwann cell progenitors. These tumors represent one of the hallmarks of the neurofibromatosis type 1 (NF1) tumor predisposition syndrome, where they can number in the thousands. While NF1-DNFs arise due to mutations in the NF1 gene, the vast majority of DNFs occur sporadically (sp-DNFs), where the genetic etiology is currently unknown. Herein, we employed whole-exome sequencing of sp-DNFs to identify a recurrent mutation in the KIR2DL5 gene, which codes for a protein suppressor of natural killer (NK) cell activity. While the function of KIR2DL5 outside of the immune system is unknown, we identified a KIR2DL5N173D mutation in three of nine sp-DNFs, resulting in loss of KIR2DL5 protein expression. In contrast, two of these subjects had unrelated tumors, which retained KIR2DL5 protein expression. Moreover, loss of KIR2DL5 expression was demonstrated in 15 of 45 independently-identified sp-DNFs. Consistent with its potential role as a negative growth regulator important for neurofibroma maintenance, ectopic KIR2DL5N173D expression in normal human Schwann cells resulted in reduced KIR2DL5 expression and increased cell proliferation. Similarly, KIR2DL5 short hairpin RNA knockdown (KD) decreased KIR2DL5 protein levels and increased cell proliferation, as well as correlated with PDGFRβ and downstream RAS/AKT/mTOR hyperactivation. Importantly, inhibition of PDGFRβ or AKT/mTOR activity in KIR2DL5-KD human Schwann cells reduced proliferation to control levels. Collectively, these findings establish KIR2DL5 as a new Schwann cell growth regulator relevant to sp-DNF pathogenesis, which links sporadic and NF1-associated DNFs through RAS pathway hyperactivation.

Insertional Mutagenesis Identifies a STAT3/Arid1b/β-catenin Pathway Driving Neurofibroma Initiation.

To identify genes and signaling pathways that initiate Neurofibromatosis type 1 (NF1) neurofibromas, we used unbiased insertional mutagenesis screening, mouse models, and molecular analyses. We mapped an Nf1-Stat3-Arid1b/β-catenin pathway that becomes active in the context of Nf1 loss. Genetic deletion of Stat3 in Schwann cell progenitors (SCPs) and Schwann cells (SCs) prevents neurofibroma formation, decreasing SCP self-renewal and β-catenin activity. β-catenin expression rescues effects of Stat3 loss in SCPs. Importantly, P-STAT3 and β-catenin expression correlate in human neurofibromas. Mechanistically, P-Stat3 represses Gsk3β and the SWI/SNF gene Arid1b to increase β-catenin. Knockdown of Arid1b or Gsk3β in Stat3(fl/fl);Nf1(fl/fl);DhhCre SCPs rescues neurofibroma formation after in vivo transplantation. Stat3 represses Arid1b through histone modification in a Brg1-dependent manner, indicating that epigenetic modification plays a role in early tumorigenesis. Our data map a neural tumorigenesis pathway and support testing JAK/STAT and Wnt/β-catenin pathway inhibitors in neurofibroma therapeutic trials.

Runx1: a new driver in neurofibromagenesis.

The Runt-related transcription factor-1 (RUNX1 or AML1) encodes a transcription factor that serves as a master developmental regulator. It is important for hematopoiesis, angiogenesis, maturation of megakaryocytes, and differentiation of T and B cells [1]. Runx1 is also important for neuronal development and glial cell differentiation [2]. Runx1 is integrated into a complex regulatory network which acts both at the transcriptional and post-transcriptional levels. Runx1 activity can be regulated by several posttranslational modifications, including phosphorylation, de-phosphorylation, SUMOylation, acetylation, methylation and ubiquitination. These modifications control various aspects of transcriptional factors' activities such as auto inhibition, dimerization and ubiquitin-mediated degradation [3]. Besides its developmental determination role, RUNX1 is involved in malignant tumor formation. Reports have shown that RUNX1 is frequently de-regulated and has paradoxical effects in human cancers, in which it can function either as a tumor suppressor or oncogene [3, 4]. RUNX1 has been implicated as a tumor suppressor in several solid tumors including breast cancer, esophageal adenocarcinoma, colon cancer and possibly prostate cancer but acts as an oncogene in head/neck squamous cell carcinomas, endometrial cancer, and epithelial cancer [3, 4]. Because Runx1 is a sequence specific DNA-binding transcription factor, whether it functions as oncogene or tumor suppressor is dependent on its interaction with specific co-regulatory proteins. We recently showed that RUNX1 acts as an oncogene in the context of loss of neurofibromatosis type 1 (Nf1). Instead of chromosomal translocation and mutation frequently detected in other cancers, Runx1 is overexpressed in human and mouse neurofibroma-initiating cells, both at the messenger RNA and protein levels. Specifically, loss of Nf1 increases number of embryonic day 12.5 Runx1+/Blbp+ Schwann cell progenitors that enable neurofibroma formation in a mouse model (Figure ​(Figure1).1). Targeted genetic deletion of RUNX1 in Schwann cells and Schwann cell progenitors delays mouse neurofibroma formation in vivo (5). Figure 1 Model of neurofibromagenesis It is not clear how loss of Nf1 induces Runx1 overexpression and serves as an oncogene. There are several potential possibilities: 1) NF1 is known to encode a Ras-GTPase activating protein (Ras-GAP) and the Ras-MEK-ERK pathway is important for Nf1 neurofibroma formation [6]. Runx1 may be phosphorylated by the elevated MEK signaling to initiate the tumor formation process. 2) Elevated Wnt or Notch signaling can directly or indirectly activate Runx1, which can accelerate G1-S transition and stimulates cell proliferation. Consistently, our results show that loss of Runx1 in Schwann cells decreased cell proliferation by activating Trp53-p21 or increased cell apoptosis by inhibiting anti-apoptotic gene Bcl-2 in the context of Nf1−/− Schwann cell environment. It is possible that the elevated Runx1 within the neurofibroma cell alters cell fate (i.e. proliferation or differentiation) through Trp53-p21. Further experiments are needed to determine how p21 and Trp53 were activated or Bcl-2 was inactivated in the Runx1fl/fl;Nf1fl/fl; Dhhre tumors. 3) Runx1 might interact with epigenetic regulators such as the chromatin remodeling complexes, SWI/SNF, or polycomb repressive complexes to affect Runx1 activity by post-translational modification [7]. Overall, our study supports an oncogenic role of Runx1 in neurofibroma initiation and/or maintenance, but the underlying mechanism(s) are not clear. With increasing knowledge of RUNX1 biology, targeting the transcription factor RUNX1 or RUNX1 pathway might provide a novel therapy for neurofibroma as well as other tumors which overexpress RUNX1.

Runx1 contributes to neurofibromatosis type 1 neurofibroma formation.

Neurofibromatosis type 1 (NF1) patients are predisposed to neurofibromas but the driver(s) that contribute to neurofibroma formation are not fully understood. By cross comparison of microarray gene lists on human neurofibroma-initiating cells and developed neurofibroma Schwann cells (SCs) we identified RUNX1 overexpression in human neurofibroma initiation cells, suggesting RUNX1 might relate to neurofibroma formation. Immunostaining confirmed RUNX1 protein overexpression in human plexiform neurofibromas. Runx1 overexpression was confirmed in mouse Schwann cell progenitors (SCPs) and mouse neurofibromas at the messenger RNA and protein levels. Genetic inhibition of Runx1 expression by small hairpin RNA or pharmacological inhibition of Runx1 function by a Runx1/Cbfβ interaction inhibitor, Ro5-3335, decreased mouse neurofibroma sphere number in vitro. Targeted genetic deletion of Runx1 in SCs and SCPs delayed mouse neurofibroma formation in vivo. Mechanistically, loss of Nf1 increased embryonic day 12.5 Runx1(+)/Blbp(+) progenitors that enable tumor formation. These results suggest that Runx1 has an important role in Nf1 neurofibroma initiation, and inhibition of RUNX1 function might provide a novel potential therapeutic treatment strategy for neurofibroma patients.

Adult olfactory sphere cells are a source of oligodendrocyte and Schwann cell progenitors

The olfactory epithelial layer contains multipotent horizontal basal cells (HBCs) that differentiate into olfactory sensory neurons. Here, we show that rat HBCs express oligodendrocyte progenitor cell (OPC) and astrocyte markers. We generated olfactory sphere (OS) cells in cultures that were derived from adult rat olfactory mucosa. Fluorescence-activated cell sorting and immunofluorescence analyses showed that OS cells also express OPC and astrocyte markers. Interestingly, OS cells underwent oligodendrocyte differentiation in vitro. To study oligodendrocyte differentiation in vivo, OS cells were transplanted into injured rat spinal cords. The transplanted cells integrated into host tissue and differentiated into oligodendrocytes. When transected saphenous nerve ends were encased in collagen-containing silicone tubes with or without OS cells, the transplanted OS cells differentiated into Schwann cells. Our data provide new insights into of the stemness of OS cells.

Schwann cell myelination requires Dynein function.

BackgroundInteraction of Schwann cells with axons triggers signal transduction that drives expression of Pou3f1 and Egr2 transcription factors, which in turn promote myelination. Signal transduction appears to be mediated, at least in part, by cyclic adenosine monophosphate (cAMP) because elevation of cAMP levels can stimulate myelination in the absence of axon contact. The mechanisms by which the myelinating signal is conveyed remain unclear.ResultsBy analyzing mutations that disrupt myelination in zebrafish, we learned that Dynein cytoplasmic 1 heavy chain 1 (Dync1h1), which functions as a motor for intracellular molecular trafficking, is required for peripheral myelination. In dync1h1 mutants, Schwann cell progenitors migrated to peripheral nerves but then failed to express Pou3f1 and Egr2 or make myelin membrane. Genetic mosaic experiments revealed that robust Myelin Basic Protein expression required Dync1h1 function within both Schwann cells and axons. Finally, treatment of dync1h1 mutants with a drug to elevate cAMP levels stimulated myelin gene expression.ConclusionDync1h1 is required for retrograde transport in axons and mutations of Dync1h1 have been implicated in axon disease. Our data now provide evidence that Dync1h1 is also required for efficient myelination of peripheral axons by Schwann cells, perhaps by facilitating signal transduction necessary for myelination.

Abstract 4577: Targeting N-glycosylation of tyrosine kinase receptors for preventing tumorigenesis and malignant transformation of neurofibromatosis type I

Abstract Neurofibromatosis type I (NF1) is a dominantly inherited disease affecting 1 in every 2,500 to 3,000 individuals, representing the most common familial cancer predisposition syndrome. The hallmark of clinical manifestation of NF1 is the development of multiple neurofibromas, which are highly heterotypic benign tumors of peripheral nerve sheath mainly composed of immature Schwann cells, fibroblasts, perineurial and inflammatory matrix. NF1 patients are also at high risk for the development of certain maligancies such as pheochromocytomas, childhood myeloid leukemias, neuroblastomas, rhabdomyosarcomas, and malignant peripheral nerve sheath tumors (MPNSTs). Because of the potential involvement of underlying nerves and blood vessels, surgical removal of tumors is not always an option. Once progressing to MPNSTs, although the resection is possible, most patients will eventually relapse locally or systemically. There is no effective treatment for NF1, nor effective approaches for predicting or preventing the occurrence of devastating complications. Thus, to develop agents for preventing or reversing the tumorigenesis and malignant transformation of NF1 are critically needed. In this report, we found HGF, c-MET, EGF and EGFR are aberrantly expressed in clinical specimens of neurofibromas and MPNSTs with NF and that autocrine and/or paracrine HGF/c-MET and EGF/EGFR loops promote MPSNT cell migration and invasion in vitro (Fig1). We also found that the loss of Nf1 in neurofibromas and MPNSTs results in hyperactive of Ras (Fig2). Compared with normal Schwann cells, MPNST cells express more N-glycoproteins and display different N-glycoprotein signatures (Fig3). In order to confirm our hypothesis, we treated cells with Tunicamycin, or 2-DG (N-glycosylation inhibitors) respectively in variable doses for different time. We found that both Tunicamycin and 2-DG inhibited the proliferation and promoted apoptosis of MPNST cell lines but had no effect on normal human Schwann cells (Fig4); inhibited the glycosylation and phosphorylation of EGFR and c-MET and impaired receptor-mediated MEK-ERK1/2 and PI3K-AKT signaling in a dose-dependent manner (Fig5). Moreover, 2-DG inhibited the maturation of c-MET as demonstrated by the intact premature chain, failing to cleave into one mature α-chain and another mature α-chain. In addition, 2-DG inhibited the translocation of the receptors from the cytoplasm onto the cell surface and retained receptors in the ER and Golgi apparatus (Fig6). To date, 2-DG inhibition of N-glycosylation and phosphorylation of tyrosine kinase receptors has not been reported. These novel findings prompted us to explore whether 2-DG disrupts Ras-directed N-glycosylation of tyrosine receptors in Schwann cell progenitors and tumor cells and to evaluate its roles in preventing the tumorigenesis and malignant transformation of NF1. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4577. doi:1538-7445.AM2012-4577

Abstract 1433: TC21/R-Ras2 is a critical mediator of the Nf1 oncogenic switch

Abstract The TC21/R-Ras2 protein is an oncogenic member of the Ras family. Ras proteins act as binary switches which are ‘active’ when bound to GTP and ‘inactive’ when bound to GDP. GTPase activating proteins (GAPs) accelerate the hydrolysis from Ras-GTP to Ras-GDP. This Ras-related GTPase TC21 has transforming capabilities similar to H, N and K-Ras. Activated alleles of TC21 transform epithelial and fibroblast cell lines and induce tumors in vivo. To explore the role of TC21 in cancer we used a model of Ras activation driven by loss of the NF1 tumor suppressor protein, a GAP for all Ras proteins including TC21. Thus loss of NF1 predicts increased levels of activated TC21/R-Ras2. NF1 loss in Schwann cells of the peripheral nervous system causes benign tumors known as neurofibromas. Neurofibromas can transform to sarcomas known as malignant peripheral nerve sheath tumors (MPNSTs). We found that TC21 loss delayed benign neurofibroma formation in Nf1fl/fl;DhhCre mice. Nf1 loss increased mRNA encoding the cytokine transforming growth factor-beta (TGF-β) and rendered Schwann cell progenitors insensitive to TGF-β; these phenotypes could be rescued by the Ras-related protein TC21/R-Ras2 and were mediated through TGF-β receptors. Conversely, growth of Nf1;Trp53 brain tumors and NF1−/− MPNST sarcomas were accelerated by TC21 loss. MPNST from Nf1;Trp53 mice and NF1−/− MPNST xenografts had increased levels of mRNA encoding TGF- ≤ ligands, and blocking TGF- ≤ decreased sarcoma size induced by shTC21. In benign and malignant tumors an AKT-dependent pathway regulated TGF- ≤ expression. Indicating relevance to human tumorigenesis, global gene expression analyses demonstrated increases in expression of TGF- ≤ ligands and decreases in TGF- ≤ receptors in human neurofibromas and MPNSTs. Thus, we identify critical roles for TC21 in regulation of TGF- ≤ expression. The results are important because TGF- ≤ acts as a tumor suppressor in numerous types of benign tumors and is also known for its oncogenic role in cellular transformation and tumor progression. While it has been known that Ras proteins are involved in TGF- ≤ mediated tumor suppression and oncogenesis, integration between the pathways is incompletely understood, especially in vivo. The study demonstrates that TC21 can be a major regulator of the duality of TGF- ≤ effects on tumorigenesis in vivo. This work was supported by a grant to NR (NIH P50NS057531-03). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1433. doi:1538-7445.AM2012-1433

Bers-ERK Schwann Cells Coordinate Nerve Regeneration

In this issue of Neuron, Napoli et al. (2012) demonstrate that elevated ERK/MAPK signaling in Schwann cells is a crucial trigger for Schwann cell dedifferentiation in vivo. Moreover, the authors show that dedifferentiated Schwann cells have the potential to coordinate much of the peripheral nerve response to injury.

Specific Functions for ERK/MAPK Signaling during PNS Development

We have established functions of the stimulus-dependent MAPKs, ERK1/2 and ERK5, in DRG, motor neuron, and Schwann cell development. Surprisingly, many aspects of early DRG and motor neuron development were found to be ERK1/2 independent, and Erk5 deletion had no obvious effect on embryonic PNS. In contrast, Erk1/2 deletion in developing neural crest resulted in peripheral nerves that were devoid of Schwann cell progenitors, and deletion of Erk1/2 in Schwann cell precursors caused disrupted differentiation and marked hypomyelination of axons. The Schwann cell phenotypes are similar to those reported in neuregulin-1 and ErbB mutant mice, and neuregulin effects could not be elicited in glial precursors lacking Erk1/2. ERK/MAPK regulation of myelination was specific to Schwann cells, as deletion in oligodendrocyte precursors did not impair myelin formation, but reduced precursor proliferation. Our data suggest a tight linkage between developmental functions of ERK/MAPK signaling and biological actions of specific RTK-activating factors.

P64. Isolation and characterization of neural crest stem cells from adult human hair follicles

Neural crest (NC) is a transient embryonic tissue, whose cells are motile and multipotent until they reach their destination and differentiate according to microenvironmental cues into variety of cell types. However, a subpopulation of these cells remains multipotent. They were found, among other locations, in a bulge of adult murine whisker follicle and were designated epidermal neural crest stem cells (EPI-NCSCs). The aim of this work is to ascertain whether the EPI-NCSCs could be isolated from human hair follicles as well. Due to their exceptional properties, they could represent potential candidate for stem cell therapy. The presented work focuses on the isolation and characterization of EPI-NCSCs from human skin. We obtained population of cells that expressed markers of NC, NC progeny and general stem cell markers. After prolonged cultivation, subpopulation of cells spontaneously differentiated into some of NC derivatives, i.e. neurons, smooth muscle cells and Schwann cell progenitors. Targeted differentiation with neuregulin-1 highly increased the number of Schwann cells in culture. Human EPI-NCSCs were also able to grow under non-adherent conditions and form three-dimensional spheres. Microarray analysis was performed and gene profile of human EPI-NCSCs was compared with the list of key genes of murine EPI-NCSCs, and the list of genes upregulated in newly induced NC cells. This revealed 94% and 88% similarity, respectively. All the presented results strongly support the NCSCs identity and multipotency of isolated human cells. These cells thus could be a good candidate for stem cell therapy, especially because of the easy accessibility of donor tissue.

Cell Sorting during Regenerative Tissue Formation

Regeneration of transected peripheral nerves is a complex process involving the coordinated action of neuronal axons, glial cells, and fibroblasts. Using rodent models of nerve repair, Parrinello et al. (2010) find that ephrin signaling between fibroblasts and Schwann cell progenitors, involving the stemness factor Sox2, is required for nerve regeneration.

Isolation and Characterization of Neural Crest Stem Cells from Adult Human Hair Follicles

Neural crest (NC) is a transient embryonic tissue, whose cells are motile and multipotent until they reach their destination and differentiate according to microenvironmental cues into a variety of cell types. However, a subpopulation of these cells remains multipotent. They were found, among other locations, in a bulge of adult murine whisker follicle and were designated epidermal neural crest stem cells (EPI-NCSCs). The aim of this work is to ascertain whether the EPI-NCSCs could be isolated from human hair follicles as well. Due to their exceptional properties, they could represent potential candidates for stem cell therapy. The presented work focuses on the isolation and characterization of EPI-NCSCs from human skin. We obtained a population of cells that expressed markers of NC, NC progeny and general stem cell markers. After prolonged cultivation, the subpopulation of cells spontaneously differentiated into some of NC derivatives, i.e. neurons, smooth muscle cells and Schwann cell progenitors. Targeted differentiation with neuregulin 1 highly increased the number of Schwann cells in the culture. Human EPI-NCSCs could also grow under non-adherent conditions and form 3-dimensional spheres. Microarray analysis was performed and gene profile of human EPI-NCSCs was compared with the list of key genes of murine EPI-NCSCs and the list of genes up-regulated in newly induced NC cells. This revealed 94% and 88% similarity, respectively. All presented results strongly support the NCSC identity and multipotency of isolated human cells. These cells could thus be used in regenerative medicine, especially because of the easy accessibility of donor tissue.