Purification of Schwann cells by selection of p75 low affinity nerve growth factor receptor expressing cells from adult peripheral nerve

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.

A glycolytic shift in Schwann cells supports injured axons

Axon degeneration is a hallmark of many neurodegenerative disorders. The current assumption is that the decision of injured axons to degenerate is cell-autonomously regulated. Here we show that Schwann cells (SCs), the glia of the peripheral nervous system, protect injured axons by virtue of a dramatic glycolytic upregulation that arises in SCs as an inherent adaptation to axon injury. This glycolytic response, paired with enhanced axon-glia metabolic coupling, supports the survival of axons. The glycolytic shift in SCs is largely driven by the metabolic signaling hub, mammalian target of rapamycin complex 1, and the downstream transcription factors hypoxia-inducible factor 1-alpha and c-Myc, which together promote glycolytic gene expression. The manipulation of glial glycolytic activity through this pathway enabled us to accelerate or delay the degeneration of perturbed axons in acute and subacute rodent axon degeneration models. Thus, we demonstrate a non-cell-autonomous metabolic mechanism that controls the fate of injured axons.

Spectral Characterization of Stem Cell-Derived Myelination within the Injured Adult PNS Using the Solvatochromic Dye Nile Red

Background: Myelin is an essential component of the peripheral and central nervous system, enabling fast axonal conduction and supporting axonal integrity; limited tools exist for analysis of myelin composition in-vivo. Objective: To demonstrate that the photophysical properties of myelin-incorporated solvatochromic dyes can be exploited to probe the biochemical composition of living peripheral nerve myelin at high spatial resolution. Methods: Using the myelin-incorporated fluorescent dye Nile Red we sequentially analyzed the spectral characteristics of remyelinating myelin membranes both in-vitro and in-vivo, including in living rats. Results: We demonstrated a consistent bi-phasic evolution of emission spectra during early remyelination, and visually report the reliable biochemical flux of myelin membrane composition in-vitro and in-vivo. Conclusions: Solvatochromic spectroscopy enables the analysis of myelin membrane maturity during remyelination, and can be performed in-vivo. As the formation of myelin during early-to-late remyelination likely incorporates fluctuating fractions of lipophilic components and changes in lateral membrane mobility, we propose that our spectrochemical data reflects the observation of these biochemical processes.

M2 Phenotype Macrophages Colocalize with Schwann Cells in Human Dental Pulp

Macrophages are immune cells with high plasticity that perform many functions related to tissue injury and repair. They are generally categorized as 2 functional phenotypes: M1 (proinflammatory) and M2 (anti-inflammatory and prohealing). To investigate the role of macrophages in human dental pulp, we examined the localization and distributional alterations of macrophages in healthy dental pulp as well as during the reparative process of pulp capping with mineral trioxide aggregate (MTA) and in cariously inflamed pulp of adult human teeth. We also quantified the populations of M1/M2 macrophages in healthy dental pulp by flow cytometric analysis. CD68⁺CD86⁺ cells (M1 phenotype) and CD68⁺CD163⁺ cells (M2 phenotype) were 2.11% ± 0.50% and 44.99% ± 2.22%, respectively, of 2.96% ± 0.41% CD68⁺ cells (pan-macrophages) in whole healthy dental pulp. Interestingly, M2 phenotype macrophages were associated with Schwann cells in healthy pulp, during mineralized bridge formation, and in pulp with carious infections in vivo. Furthermore, the M2 macrophages associated with Schwann cells expressed brain-derived neurotrophic factor (BDNF) under all in vivo conditions. Moreover, we found that plasma cells expressed BDNF. Coculture of Schwann cells isolated from human dental pulp and human monocytic cell line THP-1 showed that Schwann cells induced M2 phenotypic polarization of THP-1 cell-derived macrophages. The THP-1 macrophages that maintained contact with Schwann cells were stimulated, leading to elongation of their cell shape and expression of M2 phenotype marker CD163 in cocultures. In summary, we revealed the spatiotemporal localization of macrophages and potent induction of the M2 phenotype by Schwann cells in human dental pulp. M2 macrophages protect neural elements, whereas M1 cells promote neuronal destruction. Therefore, suppressing the neurodestructive M1 phenotype and maintaining the neuroprotective M2 phenotype of macrophages by Schwann cells may be critical for development of effective treatment strategies to maintain the viability of highly innervated dental pulp.

Evaluation of two methods to isolate Schwann cells from murine sciatic nerve

BACKGROUND

Schwann cells (SC) and macrophages play key roles in the response to peripheral nerve injury (PNI). Accurate isolation of such cells is essential for further analyses that can lead to better understanding of the repair process after PNI. Separation of live SC from the injury site without culture enrichment is necessary for targeted gene expression analysis.

NEW METHODS

Two flow cytometric techniques are presented for rapid enrichment of live SC and macrophages from injured murine peripheral nerve without the need for culture.

RESULTS

SC were isolated by fluorescent activated cell sorting (FACS) using transgenic expression of eGFP in SC, or by exclusion of other cell types collected from the injury site.

COMPARISON WITH EXISTING METHOD(S)

Gene expression analyses of peripheral nerve repair have commonly used whole nerve lysates. Isolating SC allows more accurate understanding of their specific role in repair. SC are commonly enriched from nerve by culture, however this changes gene expression patterns and limits the utility for transcriptomic analysis. The surface marker p75-NTR has variable expression in different SC phenotypes and during the course of injury and repair. Using p75-NTR for SC isolation might enrich only a subset of SC. More stably expressed lineage markers for SC are intracellular and not suitable for sorting for gene expression. The methods used here avoid the requirement for surface marker labeling of SC.

CONCLUSION

Gene expression analysis of sorted cells from both methods showed successful enrichment of SC. Lineage markers such as Map1b, p75-NTR and S100b were enriched in the sorted SC population. SC sorting by eGFP expression showed improved enrichment, particularly of mature myelinating genes, although this could represent sampling of a subset of SC.

A novel approach to 32-channel peripheral nervous system myelin imaging in vivo, with single axon resolution

OBJECTIVE Intravital spectral imaging of the large, deeply situated nerves in the rat peripheral nervous system (PNS) has not been well described. Here, the authors have developed a highly stable platform for performing imaging of the tibial nerve in live rodents, thus allowing the capture of high-resolution, high-magnification spectral images requiring long acquisition times. By further exploiting the qualities of the topically applied myelin dye Nile red, this technique is capable of visualizing the detailed microenvironment of peripheral nerve demyelination injury and recovery, while allowing us to obtain images of exogenous Schwann cell myelination in a living animal. METHODS The authors caused doxorubicin-induced focal demyelination in the tibial nerves of 25 Thy-1 GFP rats, of which 2 subsets (n = 10 each) received either BFP-labeled SKP-SCs or SCs to the zone of injury. Prior to acquiring images of myelin recovery in these nerves, a tibial nerve window was constructed using a silicone hemitube, a fast drying silicone polymer, and a small coverslip. This construct was then affixed to a 3D-printed nerve stage, which in turn was affixed to an external fixation/microscope stage device. Myelin visualization was facilitated by the topical application of Nile red. RESULTS The authors reliably demonstrated intravital peripheral nerve myelin imaging with micron-level resolution and magnification, and minimal movement artifact. The detailed microenvironment of nerve remyelination can be vividly observed, while exogenously applied Schwann cells and skin-derived precursor Schwann cells can be seen myelinating axons. CONCLUSIONS Topically applied Nile red enables intravital study of myelin in the living rat PNS. Furthermore, the use of a tibial nerve window facilitates stable intravital peripheral nerve imaging, making possible high-definition spectral imaging with long acquisition times.

Olfactory Ensheathing Cells for Spinal Cord Injury: Sniffing Out the Issues

Olfactory ensheathing cells (OECs) are glia reported to sustain the continuous axon extension and successful topographic targeting of the olfactory receptor neurons responsible for the sense of smell (olfaction). Due to this distinctive property, OECs have been trialed in human cell transplant therapies to assist in the repair of central nervous system injuries, particularly those of the spinal cord. Though many studies have reported neurological improvement, the therapy remains inconsistent and requires further improvement. Much of this variability stems from differing olfactory cell populations prior to transplantation into the injury site. While some studies have used purified cells, others have used unpurified transplants. Although both preparations have merits and faults, the latter increases the variability between transplants received by recipients. Without a robust purification procedure in OEC transplantation therapies, the full potential of OECs for spinal cord injury may not be realised.

Vein wrapping facilitates basic fibroblast growth factor-induced heme oxygenase-1 expression following chronic nerve constriction injury

The clinical efficacy of autologous vein wrapping for recurrent compressive neuropathy has been demonstrated; however, the underlying mechanisms of this technique remain unclear. Rats were divided into chronic constriction injury (CCI) and CCI + vein wrapping (CCI + VW) groups. Mechanical allodynia was evaluated using von Frey filaments. To identify the neuroprotective factors released from veins, basic fibroblast growth factor (bFGF) mRNA expression in veins was compared to that in the sciatic nerve. The response of heme oxygenase-1 (HO-1) expression to vein wrapping was evaluated by RT-PCR and enzyme-linked immunosorbent assays. The effects of exogenous bFGF on HO-1 expression were evaluated using a sciatic nerve cell culture. Vein wrapping significantly increased the withdraw threshold levels compared to the untreated CCI group. bFGF mRNA expression in veins was higher than that in untreated sciatic nerves. HO-1 mRNA expression was induced at higher levels in sciatic nerve cells in the presence of exogenous bFGF compared to untreated control cells. HO-1 mRNA and protein expression in the sciatic nerve were also higher in the CCI + VW group compared with the CCI group. Our results suggest that vein-derived bFGF contributes to the therapeutic benefit of vein wrapping through the induction of HO-1 in the sciatic nerve. Vein wrapping is a useful technique for reducing neuropathic pain. Further understanding of the neurotrophic factors released from veins may help to optimize current procedures for treating recurrent compressive neuropathy and traumatic peripheral nerve injury, and lead to the development of new therapeutic methods using recombinant neurotrophic factors. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:898-905, 2018.

Adult skin-derived precursor Schwann cell grafts form growths in the injured spinal cord of Fischer rats

In this study, GFP⁺ skin-derived precursor Schwann cells (SKP-SCs) from adult rats were grafted into the injured spinal cord of immunosuppressed rats. Our goal was to improve grafted cell survival in the injured spinal cord, which is typically low. Cells were grafted in hyaluronan-methylcellulose hydrogel (HAMC) or hyaluronan-methylcellulose modified with laminin- and fibronectin-derived peptide sequences (eHAMC). The criteria for selection of hyaluronan was for its shear-thinning properties, making the hydrogel easy to inject, methylcellulose for its inverse thermal gelation, helping to keep grafted cells in situ, and fibronectin and laminin to improve cell attachment and, thus, prevent cell death due to dissociation from substrate molecules (i.e., anoikis). Post-mortem examination revealed large masses of GFP⁺ SKP-SCs in the spinal cords of rats that received cells in HAMC (5 out of n = 8) and eHAMC (6 out of n = 8). Cell transplantation in eHAMC caused significantly greater spinal lesions compared to lesion and eHAMC only control groups. A parallel study showed similar masses in the contused spinal cord of rats after transplantation of adult GFP⁺ SKP-SCs without a hydrogel or immunosuppression. These findings suggest that adult GFP⁺ SKP-SCs, cultured/transplanted under the conditions described here, have a capacity for uncontrolled proliferation. Growth-formation in pre-clinical research has also been documented after transplantation of: human induced pluripotent stem cell-derived neural stem cells (Itakura et al 2015 PLoS One 10 e0116413), embryonic stem cells and embryonic stem cell-derived neurons (Brederlau et al 2006 Stem Cells 24 1433-40; Dressel et al 2008 PLoS One 3 e2622), bone marrow derived mesenchymal stem cells (Jeong et al 2011 Circ. Res. 108 1340-47) and rat nerve-derived SCs following in vitro expansion for >11 passages (Funk et al 2007 Eur. J. Cell Biol. 86 207-19; Langford et al 1988 J. Neurocytology 17 521-9; Morrissey et al 1991 J. Neurosci. 11 2433-42). It is of upmost importance to define the precise culture/transplantation parameters for maintenance of normal cell function and safe and effective use of cell therapy.

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.

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.

Isolation and Purification of Schwann Cells from Spinal Nerves of Neonatal Rat

Primary cultured Schwann cells (SCs) are widely used in the investigation of the biology of SC and are important seed cells for neural tissue engineering. Here, we describe a novel protocol for harvesting primary cultured SCs from neonatal Sprague-Dawley (SD) rats. In the present protocol, dissociated SCs are isolated from the spinal nerves of neonatal rats and purified by the treatment of cytosine arabinoside (AraC).

Isolation of rat Schwann cells based on cell sorting

The present study presented a protocol that can be used to obtain rapidly a high purity of proliferating rat Schwann cells from freshly dissociated rat peripheral nerves. The sciatic nerves of newborn rats (1–3 day old) were dissociated, and the Schwann cells (SCs) were purified using fluorescence-activated cell sorting (FACS) based on the SC membrane-specific expression of the low-affinity nerve growth factor receptor, p75NGFR and oligodendrocyte marker 4. Following sorting, the cells were plated on poly-l-lysine-coated dishes in SC culture medium containing DMEM with 10% FBS, 1% penicillin/streptomycin, 2 µM forskolin and 10 ng/ml HRG. The purified rat SCs were propagated for passaging until confluent. This protocol resulted in SC cultures, which were >98% pure. This FACS-based protocol can be used to facilitate future investigations of general SC biology.

Human eyelid adipose tissue-derived Schwann cells promote regeneration of a transected sciatic nerve

Schwann cells (SCs) can promote the regeneration of injured peripheral nerves while the clinical application is limited by donor site complications and the inability to generate an ample amount of cells. In this study, we have isolated human eyelid adipose-derived Schwann cells (hE-SCs) from human eyelid adipose tissue and identified the cell phenotype and function. Using immunofluorescence and H & E staining, we detected subtle nerve fibers and SCs in human eyelid adipose tissue. Immunofluorescence staining indicated that hE-SCs expressed glial markers, such as S100, p75NTR GFAP, Sox10 and Krox20. To explore whether hE-SCs promote the regeneration of injured peripheral nerves in vivo, a Balb/c-nu mice model was used in the study, and mice were randomly assigned to five groups: Matrigel; hE-SCs/P0; hE-SCs/P2; hE-FLCs/P2; and Autograft. After 12 weeks, functional and histological assessments of the regenerated nerves showed that sciatic nerve defect was more effectively repaired in the hE-SCs/P2 group which achieved 66.1 ± 6.5% purity, than the other three groups and recovered to similar level to the Autograft group. These results indicated that hE-SCs can promote the regeneration of injured peripheral nerve and the abundant, easily accessible supply of adipose tissue might be a promising source of SCs for peripheral nerve repair.

Characterization and Schwann Cell Seeding of up to 15.0 cm Long Spider Silk Nerve Conduits for Reconstruction of Peripheral Nerve Defects

Nerve reconstruction of extended nerve defect injuries still remains challenging with respect to therapeutic options. The gold standard in nerve surgery is the autologous nerve graft. Due to the limitation of adequate donor nerves, surgical alternatives are needed. Nerve grafts made out of either natural or artificial materials represent this alternative. Several biomaterials are being explored and preclinical and clinical applications are ongoing. Unfortunately, nerve conduits with successful enhancement of axonal regeneration for nerve defects measuring over 4.0 cm are sparse and no conduits are available for nerve defects extending to 10.0 cm. In this study, spider silk nerve conduits seeded with Schwann cells were investigated for in vitro regeneration on defects measuring 4.0 cm, 10.0 cm and 15.0 cm in length. Schwann cells (SCs) were isolated, cultured and purified. Cell purity was determined by immunofluorescence. Nerve grafts were constructed out of spider silk from Nephila edulis and decellularized ovine vessels. Finally, spider silk implants were seeded with purified Schwann cells. Cell attachment was observed within the first hour. After 7 and 21 days of culture, immunofluorescence for viability and determination of Schwann cell proliferation and migration throughout the conduits was performed. Analyses revealed that SCs maintained viable (>95%) throughout the conduits independent of construct length. SC proliferation on the spider silk was determined from day 7 to day 21 with a proliferation index of 49.42% arithmetically averaged over all conduits. This indicates that spider silk nerve conduits represent a favorable environment for SC attachment, proliferation and distribution over a distance of least 15.0 cm in vitro. Thus spider silk nerve implants are a highly adequate biomaterial for nerve reconstruction.

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

We herein developed a protocol for the rapid procurement of adult nerve-derived Schwann cells (SCs) that was optimized to implement an immediate enzymatic dissociation of fresh nerve tissue while maintaining high cell viability, improving yields and minimizing fibroblast and myelin contamination. This protocol introduces: (1) an efficient method for enzymatic cell release immediately after removal of the epineurium and extensive teasing of the nerve fibers; (2) an adaptable drop-plating method for selective cell attachment, removal of myelin debris, and expansion of the initial SC population in chemically defined medium; (3) a magnetic-activated cell sorting purification protocol for rapid and effective fibroblast elimination; and (4) an optional step of cryopreservation for the storage of the excess of cells. Highly proliferative SC cultures devoid of myelin and fibroblast growth were obtained within three days of nerve processing. Characterization of the initial, expanded, and cryopreserved cell products confirmed maintenance of SC identity, viability and growth rates throughout the process. Most importantly, SCs retained their sensitivity to mitogens and potential for differentiation even after cryopreservation. To conclude, this easy-to-implement and clinically relevant protocol allows for the preparation of expandable homogeneous SC cultures while minimizing time, manipulation of the cells, and exposure to culture variables.

Dispase rapidly and effectively purifies Schwann cells from newborn mice and adult rats

In the present study, Schwann cells were isolated from the sciatic nerve of neonatal mice and purified using dispase and collagenase. Results showed that after the first round of purification with dispase, most of the Schwann cells appeared round in shape and floated in culture solution after 15 minutes. In addition, cell yield and cell purity were higher when compared to the collagenase group. After the second round of purification, the final cell yield for the dispase group was higher than that for the collagenase group, but no significant difference was found in cell purity. Moreover, similar results in cell quantity and purity were observed in adult Sprague-Dawley rats. These findings indicate that purification with dispase can result in the rapid isolation of Schwann cells with a high yield and purity.

An efficient system for selection and culture of Schwann cells from adult rat peripheral nerves

Schwann cells (SCs), the supporting cells of the peripheral nerves, are indispensable for regenerating the peripheral and central nervous system. Copious preparation of these cells in a well-defined manner is to be a privileged position. SCs cultivation is overwhelmed by contaminating fibroblasts which are often outgrowing as the predominant cell type in an in vitro culture. This study introduces a technically simple and efficient procedure for SCs isolation and enrichment based on implementing recombinant and defined supplements. Collected adult rat sciatic nerves were cultured for 10 days as in vitro predegeneration. After dissociation and plating, the medium changed to knockout serum replacement supplemented DMDM/F12 medium containing various growth factors. The whole procedure took 3 weeks and SCs purity was then evaluated through implementing specific cytoplasmic and membranous markers. The viability of enriched SCs were evaluated by MTT assay. Within 10 days, over 99 % homogenous SCs were achieved and confirmed through immunofluorescence staining and flow-cytometry for P75(NTR) and S100 markers, respectively. MTT data revealed that the viability and metabolic activities of purified SCs were increased in expansion medium. This study provides a technically easy and efficient method with the benefits of not utilizing bovine serum or other animal products for SCs isolation and enrichment.

Purification of Schwann cells

This article introduces methods for the acute purification and primary culture of Schwann cells from the mouse sciatic nerve. Immunopanning can be used to isolate Schwann cells from intact nerves during early postnatal development as well as to purify Schwann cells from adult nerves following sciatic nerve injury. These methods facilitate the exploration of mouse Schwann cell biology in the healthy and injured peripheral nerve.

The Lyme disease spirochete Borrelia burgdorferi induces inflammation and apoptosis in cells from dorsal root ganglia

Background

Lyme neuroborreliosis (LNB), caused by the spirochete Borrelia burgdorferi, affects both the peripheral and the central nervous systems. Radiculitis or nerve root inflammation, which can cause pain, sensory loss, and weakness, is the most common manifestation of peripheral LNB in humans. We previously reported that rhesus monkeys infected with B. burgdorferi develop radiculitis as well as inflammation in the dorsal root ganglia (DRG), with elevated levels of neuronal and satellite glial cell apoptosis in the DRG. We hypothesized that B. burgdorferi induces inflammatory mediators in glial and neuronal cells and that this inflammatory milieu precipitates glial and neuronal apoptosis.

Methods

To model peripheral neuropathy in LNB we incubated normal rhesus DRG tissue explants with live B. burgdorferi ex vivo and identified immune mediators, producer cells, and verified the presence of B. burgdorferi in tissue sections by immunofluorescence staining and confocal microscopy. We also set up primary cultures of DRG cells from normal adult rhesus macaques and incubated the cultures with live B. burgdorferi. Culture supernatants were subjected to multiplex ELISA to detect immune mediators, while the cells were evaluated for apoptosis by the in situ TUNEL assay. A role for inflammation in mediating apoptosis was assessed by evaluating the above phenomena in the presence and absence of various concentrations of the anti-inflammatory drug dexamethasone. As Schwann cells ensheath the dorsal roots of the DRG, we evaluated the potential of live B. burgdorferi to induce inflammatory mediators in human Schwann cell (HSC) cultures.

Results

Rhesus DRG tissue explants exposed to live B. burgdorferi showed localization of CCL2 and IL-6 in sensory neurons, satellite glial cells and Schwann cells while IL-8 was seen in satellite glial cells and Schwann cells. Live B. burgdorferi induced elevated levels of IL-6, IL-8 and CCL2 in HSC and DRG cultures and apoptosis of sensory neurons. Dexamethasone reduced the levels of immune mediators and neuronal apoptosis in a dose dependent manner.

Conclusion

In this model, B. burgdorferi induced an inflammatory response and neuronal apoptosis of DRG. These pathophysiological processes could contribute to peripheral neuropathy in LNB.

Tissue engineered constructs for peripheral nerve surgery

BACKGROUND

Tissue engineering has been defined as "an interdisciplinary field that applies the principles of engineering and life sciences toward the development of biological substitutes that restore, maintain, or improve tissue function or a whole organ". Traumatic peripheral nerve injury resulting in significant tissue loss at the zone of injury necessitates the need for a bridge or scaffold for regenerating axons from the proximal stump to reach the distal stump.

METHODS

A review of the literature was used to provide information on the components necessary for the development of a tissue engineered peripheral nerve substitute. Then, a comprehensive review of the literature is presented composed of the studies devoted to this goal.

RESULTS

Extensive research has been directed toward the development of a tissue engineered peripheral nerve substitute to act as a bridge for regenerating axons from the proximal nerve stump seeking the distal nerve. Ideally this nerve substitute would consist of a scaffold component that mimics the extracellular matrix of the peripheral nerve and a cellular component that serves to stimulate and support regenerating peripheral nerve axons.

CONCLUSIONS

The field of tissue engineering should consider its challenge to not only meet the autograft "gold standard" but also to understand what drives and inhibits nerve regeneration in order to surpass the results of an autograft.

Adult craniofacial stem cells: sources and relation to the neural crest

During the process of development, neural crest cells migrate out from their niche between the newly formed ectoderm and the neural tube. Thereafter, they give rise not only to ectodermal cell types, but also to mesodermal cell types. Cell types with neural crest ancestry consequently comprise a number of specialized varieties, such as ectodermal neurons, melanocytes and Schwann cells, as well as mesodermal osteoblasts, adipocytes and smooth muscle cells. Numerous recent studies suggest that stem cells with a neural crest origin persist into adulthood, especially within the mammalian craniofacial compartment. This review discusses the sources of adult neural crest-derived stem cells (NCSCs) derived from the cranium, as well as their differentiation potential and expression of key stem cell markers. Furthermore, the expression of marker genes associated with embryonic stem cells and the issue of multi- versus pluripotency of adult NCSCs is reviewed. Stringent tests are proposed, which, if performed, are anticipated to clarify the issue of adult NCSC potency. Finally, current pre-clinical and clinical data are discussed in light of the clinical impact of adult NCSCs.

Sodium-dependent vitamin C transporter 2 deficiency causes hypomyelination and extracellular matrix defects in the peripheral nervous system

Ascorbic acid (vitamin C) is necessary for myelination of Schwann cell/neuron cocultures and has shown beneficial effects in the treatment of a Charcot-Marie-Tooth neuropathy 1A (CMT1A) mouse model. Although clinical studies revealed that ascorbic acid treatment had no impact on CMT1A, it is assumed to have an important function in peripheral nerve myelination and possibly in remyelination. However, the transport pathway of ascorbic acid into peripheral nerves and the mechanism of ascorbic acid function in peripheral nerves in vivo remained unclear. In this study, we used sodium-dependent vitamin C transporter 2-heterozygous (SVCT2(+/-)) mice to elucidate the functions of SVCT2 and ascorbic acid in the murine peripheral nervous system. SVCT2 and ascorbic acid levels were reduced in SVCT2(+/-) peripheral nerves. Morphometry of sciatic nerve fibers revealed a decrease in myelin thickness and an increase in G-ratios in SVCT2(+/-) mice. Nerve conduction velocities and sensorimotor performance in functional tests were reduced in SVCT2(+/-) mice. To investigate the mechanism of ascorbic acid function, we studied the expression of collagens in the extracellular matrix of peripheral nerves. Here, we show that expression of various collagen types was reduced in sciatic nerves of SVCT2(+/-) mice. We found that collagen gene transcription was reduced in SVCT2(+/-) mice but hydroxyproline levels were not, indicating that collagen formation was regulated on the transcriptional and not the posttranslational level. These results help to clarify the transport pathway and mechanism of action of ascorbic acid in the peripheral nervous system and may lead to novel therapeutic approaches to peripheral neuropathies by manipulation of SVCT2 function.

Culture and proliferation of highly purified adult Schwann cells from rat, dog, and man

This chapter presents fast and easy protocols to obtain highly purified cultures of proliferating adult rat, canine, and human Schwann cells. Cell preparation from predegenerated adult sciatic nerves combined with the use of melanocyte growth medium supplemented with forskolin, fibroblast growth factor-2, pituitary extract, and heregulin as selective, serum-free culture medium and two methods for a consecutive cell-enrichment step are described. Our protocols result in approximately 90% pure Schwann cell cultures (or higher). The average time to obtain highly purified in vitro cultures of adult Schwann cells is 21 days.

Sciatic nerve regeneration in rats by a promising electrospun collagen/poly(ε-caprolactone) nerve conduit with tailored degradation rate

Background

To cope with the limitations faced by autograft acquisitions particularly for multiple nerve injuries, artificial nerve conduit has been introduced by researchers as a substitute for autologous nerve graft for the easy specification and availability for mass production. In order to best mimic the structures and components of autologous nerve, great efforts have been made to improve the designation of nerve conduits either from materials or fabrication techniques. Electrospinning is an easy and versatile technique that has recently been used to fabricate fibrous tissue-engineered scaffolds which have great similarity to the extracellular matrix on fiber structure.

Results

In this study we fabricated a collagen/poly(ε-caprolactone) (collagen/PCL) fibrous scaffold by electrospinning and explored its application as nerve guide substrate or conduit in vitro and in vivo. Material characterizations showed this electrospun composite material which was made of submicron fibers possessed good hydrophilicity and flexibility. In vitro study indicated electrospun collagen/PCL fibrous meshes promoted Schwann cell adhesion, elongation and proliferation. In vivo test showed electrospun collagen/PCL porous nerve conduits successfully supported nerve regeneration through an 8 mm sciatic nerve gap in adult rats, achieving similar electrophysiological and muscle reinnervation results as autografts. Although regenerated nerve fibers were still in a pre-mature stage 4 months postoperatively, the implanted collagen/PCL nerve conduits facilitated more axons regenerating through the conduit lumen and gradually degraded which well matched the nerve regeneration rate.

Conclusions

All the results demonstrated this collagen/PCL nerve conduit with tailored degradation rate fabricated by electrospinning could be an efficient alternative to autograft for peripheral nerve regeneration research. Due to its advantage of high surface area for cell attachment, it is believed that this electrospun nerve conduit could find more application in cell therapy for nerve regeneration in future, to further improve functional regeneration outcome especially for longer nerve defect restoration.

Human Schwann cells retain essential phenotype characteristics after immortalization

Schwann cells (SCs) play an important role in the pathogenesis of peripheral nerve diseases and represent a potential target for development of therapies. However, use of primary human SCs (hSCs) for in vitro models is limited because these cells are difficult to prepare and maintain in high yield and purity under common cell culture conditions. To circumvent this obstacle, we immortalized primary human fetal SCs using the SV40 large T-antigen and human telomerase reverse transcriptase expression vectors. After cloning, selection, and purification, we evaluated several immortalized SC lines for their ability to express extracellular matrix (ECM) molecules and myelinate embryonic rat sensory axons. In addition, we established a gene expression profile and explored their sensitivity to oxidative stress in a simple in vitro assay. Immortalized hSC clones expressed common glial markers and a broad variety of growth factors, receptors, and ECM molecules as determined by immunocytochemistry, microarray, and quantitative reverse transcription-polymerase chain reaction. In neuron-SC co-cultures, these cells were able to myelinate rat dorsal root ganglia neurons, although their effectiveness was lower in comparison to primary rat SCs. In toxicity assays, immortalized hSCs remain susceptible to oxidative stress induced by H(2)O(2). This study shows that, using specific immortalization techniques, it is possible to establish hSC lines that retain characteristics of typical primary hSCs. These cells are particularly useful for drug screening and studies aimed at disease mechanisms involving SCs.

Transient lysosomal activation is essential for p75 nerve growth factor receptor expression in myelinated Schwann cells during Wallerian degeneration

Myelinated Schwann cells in the peripheral nervous system express the p75 nerve growth factor receptor (p75NGFR) as a consequence of Schwann cell dedifferentiation during Wallerian degeneration. p75NGFR has been implicated in the remyelination of regenerating nerves. Although many studies have shown various mechanisms underlying Schwann cell dedifferentiation, the molecular mechanism contributing to the re-expression of p75NGFR in differentiated Schwann cells is largely unknown. In the present study, we found that lysosomes were transiently activated in Schwann cells after nerve injury and that the inhibition of lysosomal activation by chloroquine or lysosomal acidification inhibitors prevented p75NGFR expression at the mRNA transcriptional level in an ex vivo Wallerian degeneration model. Lysosomal acidification inhibitors suppressed demyelination, but not axonal degeneration, thereby suggesting that demyelination mediated by lysosomes may be an important signal for inducing p75NGFR expression. Tumor necrosis factor-α (TNF-α) has been suggested to be involved in regulating p75NGFR expression in Schwann cells. In this study, we found that removing TNF-α in vivo did not significantly suppress the induction of both lysosomes and p75NGFR. Thus, these findings suggest that lysosomal activation is tightly correlated with the induction of p75NGFR in demyelinating Schwann cells during Wallerian degeneration.

Stem cell and neuron co-cultures for the study of nerve regeneration

Many experimental in vivo studies have indicated that Schwann cells are key facilitators of peripheral nerve regeneration but their clinical therapeutic potential may be limited. Recent advances suggest that stem cell therapy could one day be used to treat nerve traumas. We have shown how adult stem cells can be differentiated into a Schwann cell phenotype, characterised by expression of glial cell proteins and promotion of neurite outgrowth. The development of new cell culture models which mimic the in vivo regeneration environment will help us to better understand the functional benefits of these cells. Here, we describe a stepwise approach towards this, moving from traditional two-dimensional non-contact co-cultures to new three-dimensional models utilising fibrin matrices.

Purification and transfection of cochlear Schwann cells

Schwann cells line nerve fibers in the peripheral nervous system (PNS) and synthesize myelin. In addition, they support neuronal survival, neurite growth and regeneration. In dissociated cultures of postnatal mouse spiral ganglia, regenerating neurites spontaneously associate with Schwann cells. However, the mechanisms and consequences of interactions between cochlear Schwann cells and spiral ganglion neurites have not been examined. Further, the similarities and differences between cochlear Schwann cells and other PNS Schwann cells have not been studied. Experiments to examine these questions will rely on the ability to purify and characterize cochlear Schwann cells. Here we present methods for purifying Schwann cells from postnatal mouse cochleas and for transfecting them with expression plasmids. Dissociated spiral ganglia were plated on poly-D-lysine/laminin in medium containing neurotrophins, leukemia inhibitory factor (LIF), N2 supplement and serum and maintained for 5 days. Cells were harvested with trypsin/EDTA and subjected to an immuno-magnetic purification procedure. After 24 h in vitro, cultures were >85% Schwann cells. Nucleofection of purified Schwann cells with pMax-green fluorescent protein (pMax-GFP) plasmid, or with pEGFP-C-vimentin plasmid returned >45% transfection efficiency. These methods will allow the in-depth characterization of cochlear Schwann cells and an evaluation of their biochemical, functional, and genetic mechanisms that may promote neurite growth from the spiral ganglion.

Adenoviral gene transfer of bone morphogenetic protein-7 enhances functional recovery after sciatic nerve injury in rats

Bone morphogenetic proteins (BMPs), members of the transforming growth factor-β subfamily, function as instructive signals for neuronal lineage commitment and promote neuronal differentiation. However, the mechanism of BMP7 action in vivo after peripheral nerve injury is poorly understood. This study examines the efficacy of gene transfer of adenoviral (Ad) BMP7 on peripheral neuropathy. Transgene expression was found in both Ad-infected sciatic nerves and their respective remote neurons, indicating Ad transduction by a retrograde transport. After AdBMP7 infection to nerves, the sciatic nerves were crushed or transected. Hind limb functional behavior, including rotarod test and sciatic functional index, were conducted in rats weekly after nerve injury. Interestingly, enhanced BMP7 expression significantly improved hind limb functional recovery in AdBMP7-transduced rats when compared with AdGFP-transduced nerve-crushed or transected rats. Furthermore, AdBMP7 transduction reduced injury-induced macrophage activation, nerve demyelination and axonal degeneration. By contrast, AdBMP7 infection did not affect the hyperalgesia paw-withdrawal latency after nerve injury. We further examined the effect of AdBMP7 infection on sciatic nerve explant and Schwann cell cultures. Enhanced cell proliferation was significantly increased by AdBMP7 transduction in both cultures. Taken together, BMP7 overexpression by Ad gene transfer was beneficial in both nerves and Schwann cells on functional recovery after sciatic nerve injury in rats.

Sodium-dependent vitamin C transporter 2 (SVCT2) is necessary for the uptake of L-ascorbic acid into Schwann cells

Ascorbic acid has been shown to be an essential component for in vitro myelination and to improve the clinical and pathological phenotype of a mouse model of Charcot-Marie-tooth disease 1A. The mechanism of ascorbic acid uptake into peripheral nerves, however, has not been addressed so far. Hence, we studied the expression and activity of sodium-dependent vitamin C transporters 1 and 2 (SVCT1 and 2) in the peripheral nervous system. Using immunohistochemistry, immunoblotting, and reverse transcription PCR, we could show that SVCT1 and 2 were differentially expressed in myelinated peripheral nerve fibers and Schwann cell (SC) cultures. SVCT1 was expressed at very low levels confined to the axons, whereas SVCT2 was highly expressed both in the axons and in the SCs. SVCT2 was localized particularly in SC compartments of uncompacted myelin. Uptake assays using (14)C-labeled ascorbic acid showed transport of ascorbic acid into SC cultures. Ascorbic acid transport was dependent on the concentration of sodium, magnesium, and calcium in the extracellular medium. Treatment with the flavonoid phloretin, a known inhibitor of SVCT1 and 2, and specific RNA interference with SVCT2 caused significant reductions in ascorbic acid uptake into SCs. Phloretin-inhibited uptake of ascorbic acid was further shown in freshly dissected, cell-culture-naïve rat sciatic nerves. These results provide evidence for the first time that uptake of ascorbic acid in the peripheral nervous system is crucially dependent on the expression and activity of SVCT2.

Novel method to obtain highly enriched cultures of adult rat Schwann cells

Schwann cells (SCs) can be used to repair both the peripheral and central nervous systems. Therefore, establishment of a procedure to obtain activated, highly proliferative SCs, in an appropriate time for clinical applications, is a prerequisite. Purification is complicated by contamination with fibroblasts which often become the predominant cell type in an in vitro SC culture. This study describes a novel and efficient method to enrich SCs by utilizing the differential detachment properties of the two cell types. In culture, cells were treated with two different media and the chelator, EGTA, which detached SCs faster than fibroblasts and allowed for easy isolation of SCs. Within seven days, high yields of SCs with a purity of greater than 99% were achieved. This was confirmed by immunostaining characterization and flow-cytometric analyses using an antibody against the p75 low affinity nerve growth factor receptor (p75LNGFR). The entire procedure was completed in approximately 21 days. This method has the advantage of being technically easier, faster, and more efficient than other previously described methods. An SC culture that was about 99% homogenous was achieved.

A novel method for isolating Schwann cells using the extracellular domain of Necl1

Myelinating cocultures of Schwann cells and dorsal root ganglion neurons are a powerful experimental system for probing the molecular mechanisms of axon-Schwann cell interaction. The isolation of a pure population of myelination-competent Schwann cells is a prerequisite for this experimental system. We describe here a protocol for a FACS-based isolation of Schwann cells utilizing a specific affinity reagent (Necl1-Fc) and the use of these isolated cells in myelinating cocultures. An advantage of the myelinating coculture system is that Schwann cells and the neurons can be genetically manipulated before they are cocultured. We further show that our method allows the isolation of virally transduced Schwann cells in a single purification step. This protocol for the FACS-based isolation of myelination-competent Schwann cells by Necl1-Fc and the use of these cells in myelinating cocultures should significantly facilitate future studies aimed at delineation of the molecular mechanisms of axon-Schwann cell interactions and myelination.

Cytocompatibility of a novel, longitudinally microstructured collagen scaffold intended for nerve tissue repair

Traumatic injury to the nervous system induces functional deficits as a result of axonal destruction and the formation of scar tissue, cystic cavitation, and physical gaps. Bioengineering bridging materials should ideally act as cell carriers for the implantation of axon growth-promoting glia, as well as supporting integration with host cell types. Here, we describe the cytocompatibility of a novel, micro-structured porcine collagen scaffold containing densely packed and highly orientated channels that, in three-dimensional (3D) tissue culture, supports attachment, proliferation, aligned process extension, and directed migration by populations of glial cells (olfactory nerve ensheathing cells and astrocytes) and orientated axonal growth by neurons (differentiated human SH-SY5Y neuroblastoma cell line). The seeded glia required several weeks to penetrate deeply into the highly porous scaffold, where they adopted an orientated morphology similar to that displayed in simple 2D cultures. The direct interaction between SH-SY5Y-derived nerve fibers and the collagen scaffold also resulted in highly orientated axonal growth. It is likely that biocompatible scaffolds that are capable of promoting glial cell attachment, migration, and highly orientated process outgrowth will be important for future repair strategies for traumatically injured nervous tissues.

In vitro cell alignment obtained with a Schwann cell enriched microstructured nerve guide with longitudinal guidance channels

Therapeutic benefits of autologous nerve grafting in repair of peripheral nerve lesions have not been reached using any alternative nerve guide. Nevertheless, issues of co-morbidity and limited availability of donor nerves urgently ask for a need of bioartificial nerve guides which could either replace or complement autologous nerve grafts. It is increasingly appreciated that optimal nerve guides comprise both physical and molecular cues in support of peripheral axon regeneration. Now, we present a collagen-based microstructured 3D nerve guide containing numerous longitudinal guidance channels with dimensions resembling natural endoneurial tubes. Moreover, these nerve guides could be functionalized by Schwann cell (SC) seeding. Viable SCs did not only adhere to the nerve guide, but also migrated throughout the guidance channels. Of particular importance was the observation that SCs within the guidance channels formed cellular columns reminiscent of "Bands of Büngner", which are crucial structures in the natural process of peripheral nerve regeneration during the Wallerian degeneration. We, therefore, conclude that our orientated 3D nerve guides (decorated with SCs) with their physical and molecular properties may hold great promise in the repair of peripheral nerve lesion and serve as a basis for future experimental regeneration studies.

Inhibition of N-cadherin and beta-catenin function reduces axon-induced Schwann cell proliferation

N-cadherin and beta-catenin are involved in cell adhesion and cell cycle in tumor cells and neural crest. Both are expressed at key stages of Schwann cell (SC) development, but little is known about their function in the SC lineage. We studied the role of these molecules in adult rat derived SC-embryonic dorsal root ganglion cocultures by using low-Ca(2+) conditions and specific blocking antibodies to interfere with N-cadherin function and by using small interfering RNA (siRNA) to decrease beta-catenin expression in both SC-neuron cocultures and adult rat-derived SC monocultures. N-cadherin blocking conditions decreased SC-axon association and reduced axon-induced SC proliferation. In SC monocultures, beta-catenin reduction diminished the proliferative response of SCs to the mitogen beta1-heregulin, and, in SC-DRG cocultures, beta-catenin reduction inhibited axon-contact-dependent SC proliferation. Stimulation of SC cultures with beta1-heregulin increased total beta-catenin protein amount, phosphorylation of GSK-3beta and beta-catenin presence in nuclear extracts. In conclusion, our findings suggest a previously unrecognized contribution of beta-catenin and N-cadherin to axon-induced SC proliferation.

Targeting of pancreatic glia in type 1 diabetes

OBJECTIVE

Type 1 diabetes reflects autoimmune destruction of beta-cells and peri-islet Schwann cells (pSCs), but the mechanisms of pSC death and the T-cell epitopes involved remain unclear.

RESEARCH DESIGN AND METHODS

Primary pSC cultures were generated and used as targets in cytotoxic T-lymphocyte (CTL) assays in NOD mice. Cognate interaction between pSC and CD8(+) T-cells was assessed by transgenic restoration of beta2-microglobulin (beta2m) to pSC in NOD.beta2m(-/-) congenics. I-A(g7) and K(d) epitopes in the pSC antigen glial fibrillary acidic protein (GFAP) were identified by peptide mapping or algorithms, respectively, and the latter tested by immunotherapy.

RESULTS

pSC cultures did not express major histocompatibility complex (MHC) class II and were lysed by ex vivo CTLs from diabetic NOD mice. In vivo, restoration of MHC class I in GFAP-beta2m transgenics significantly accelerated adoptively transferred diabetes. Target epitopes in the pSC autoantigen GFAP were mapped to residues 79-87 and 253-261 for K(d) and 96-110, 116-130, and 216-230 for I-A(g7). These peptides were recognized spontaneously in NOD spleens as early as 2.5 weeks of age, with proliferative responses peaking around weaning and detectable lifelong. Several were also recognized by T-cells from new-onset type 1 diabetic patients. NOD mouse immunotherapy at 8 weeks with the CD8(+) T-cell epitope, GFAP 79-87 but not 253-261, significantly inhibited type 1 diabetes and was associated with reduced gamma-interferon production to whole protein GFAP.

CONCLUSIONS

Collectively, these findings elucidate a role for pSC-specific CD8(+) T-cells in islet inflammation and type 1 diabetes pathogenesis, further supporting neuronal involvement in beta-cell demise.

Isolation of skin-derived precursors (SKPs) and differentiation and enrichment of their Schwann cell progeny

This protocol describes methods of isolating skin-derived precursors (SKPs) from rodent and human skin, and for generating and enriching Schwann cells from rodent SKPs. SKPs are isolated as a population of non-adherent cells from the dermis that proliferate and self-renew as floating spheres in response to fibroblast growth factor 2 (FGF2) and epidermal growth factor (EGF). Their differentiation into Schwann cells and subsequent enrichment of these differentiated progeny involves culturing SKPs as adherent cells in the absence of FGF2 and EGF, but in the presence of neuregulins, and then mechanically isolating the Schwann cell colonies using cloning cylinders. Methods for expanding and characterizing these Schwann cells are provided. Generation of primary SKPs takes approximately 2 weeks, while differentiation of Schwann cells requires an additional 4-6 weeks.

On the presence of neurotrophin p75 receptor on rat sympathetic cerebrovascular nerves

Although the presence of neurotrophin p75 receptor on sympathetic nerves is a well-recognised feature, there is still a scarcity of details of the distribution of the receptor on cerebrovascular nerves. This study examined the distribution of p75 receptor on perivascular sympathetic nerves of the middle cerebral artery and the basilar artery of healthy young rats using immunohistochemical methods at the laser confocal microscope and transmission electron microscope levels. Immunofluorescence methods of detection of tyrosine hydroxylase (TH) in sympathetic nerves, p75 receptor associated with the nerves, and also S-100 protein in Schwann cells were applied in conjunction with confocal microscopy, while the pre-embedding single and double immunolabelling methods (ExtrAvidin and immuno-gold-silver) were applied for the electron microscopic examination. Immunofluorescence studies revealed "punctuate" distribution of the p75 receptor on sympathetic nerves including accompanying Schwann cells. Image analysis of the nerves showed that the level of co-localization of p75 receptor and TH was low. Immunolabelling applied at the electron microscope level also showed scarce co-localization of TH (which was intra-axonal) and p75. Immunoreactivity for p75 receptor was present on the cell membrane of perivascular axons and to a greater extent on the processes of accompanying Schwann cells. Some Schwann cell processes were adjacent to each other displaying strong immunoreactivity for p75 receptor; immunoreactivity was located on the extracellular sites of the adjacent cell membranes suggesting that the receptor was involved in cross talk between these. It is likely that variability of locations of p75 receptor detected in the study reflects diverse interactions of p75 receptor with axons and Schwann cells. It might also imply a diverse role for the receptor and/or the plasticity of sympathetic cerebrovascular nerves to neurotrophin signalling.

Guidance of glial cell migration and axonal growth on electrospun nanofibers of poly-ε-caprolactone and a collagen/poly-ε-caprolactone blend

Our long-term goal is to develop an artificial implant as a conduit for axonal regeneration after peripheral nerve injury. In this study, biodegradable, aligned poly-epsilon-caprolactone (PCL) and collagen/PCL (C/PCL) nanofibers designed as guidance structures were produced by electrospinning and tested in cell culture assays. We compared fibers of 100% PCL with fibers consisting of a 25:75% C/PCL blend. To test their biocompatibility, assays of cell adhesion, survival, migration, effects on cell morphology, axonal growth and axonal guidance were performed. Both types of eletrospun fibers supported oriented neurite outgrowth and glial migration from dorsal root ganglia (DRG) explants. Schwann cell migration, neurite orientation, and process formation of Schwann cells, fibroblasts and olfactory ensheathing cells were improved on C/PCL fibers, when compared to pure PCL fibers. While the velocity of neurite elongation from DRG explants was higher on PCL fibers, analysis of isolated sensory neurons showed significantly better axonal guidance by the C/PCL material. The data demonstrate that electrospun fibers composed of a collagen and PCL blend represent a suitable substrate for supporting cell proliferation, process outgrowth and migration and as such would be a good material for artificial nerve implants.