S-100 protein and laminin: immunocytochemical markers for human Schwann cells in vitro

Human Schwann Cells in vitro III. Analytical Methods and a Practical Approach for Quality Control

This paper introduces simple analytical methods and bioassays to promptly assess the identity and function of in vitro cultured human Schwann cells (hSCs). A systematic approach is proposed to unequivocally discriminate hSCs from other glial cells, non-glial cells, and non-human SCs (authentication), identify hSCs at different stages of differentiation, and determine whether individual hSCs are proliferative or senescent. Examples of how to use distinct cell-based approaches for quality control and routine troubleshooting are provided to confirm the constitution (identity, purity, and heterogeneity) and potency (bioactivity) of hSC cultures from multiple sources. The bioassays are valuable for rapidly gauging the responses of hSCs to mitogenic and differentiating factors and ascertaining the cells' basic properties before performing co-culture or cell grafting studies. The assays are image based and use adherent hSCs established in monoculture to simplify the experimental setup and interpretation of results. Finally, all sections contain thorough background information, notes, and references to facilitate decision making, data interpretation, and ad hoc method development for diverse applications.

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.

The properties of human Schwann cells: Lessons from in vitro culture and transplantation studies

Human Schwann cells (hSCs) can be isolated directly from peripheral nerve and cultured using methods similar to those used for SCs from other species. Yet, important interspecies differences are revealed when the primary or expanded hSCs are compared to their nonhuman counterparts. This review addresses the special properties of nerve-derived hSCs that have resulted to date from both in vitro studies and in vivo research on cell transplantation in animal models and human subjects. A consensus has yet to emerge about the essential attributes of cultured normal hSCs. Thus, an emphasis is placed on the importance of validating hSC cultures by means of purity, identity, and biological activity to reliably use them as in vitro models of the SC phenotype and cell therapy products for injury repair. Combining traditional immunological methods, high-resolution omics approaches, and assorted cell-based assays is so far the best approach to unequivocally identify hSC populations obtained by direct isolation or derivation from stem cells. Special considerations are required to understand and manage the variability and heterogeneity proper of donor batches, as well as to evaluate risk factors. This is particularly important if the intended use of the hSCs is implantation in the human body, diagnosis of disease, or drug testing aimed at targeting any aspect of SC function in human patients. To conclude, in view of their unique properties, new concepts and methods are needed to better understand the biology of hSCs and exploit their full potential in basic science and regenerative medicine.

Proliferative effects of melatonin on Schwann cells: implication for nerve regeneration following peripheral nerve injury

Activation of proliferation of Schwann cells is crucial for axonal guidance and successful nerve regeneration following peripheral nerve injury (PNI). Considering melatonin plays an important role in proliferative regulation of central glial cells, the present study determined whether melatonin can effectively promote Schwann cell proliferation and improve nerve regeneration after PNI. The spontaneous immortalized rat Schwann cell line (RSC 96 cells) was first analyzed by quantitative polymerase chain reaction (QPCR) to detect the potential existence of melatonin receptors. The melatonin receptor-mediated signaling responsible for proliferation was examined by measuring the phosphorylation of extracellular signal-regulated kinases (ERK1/2) pathway. The in vivo model of PNI was performed by the end-to-side neurorrhaphy. The quantity of Schwann cells as well as the number of re-innervated motor end plates (MEP) on target muscles was examined to represent the functional recovery of injured nerves. QPCR results indicated that MT1 is the dominant receptor in Schwann cells. Immunoblotting and proliferation assay revealed an enhanced phosphorylation of ERK1/2 and increased number of RSC 96 cells following melatonin administration. Nonselective melatonin receptor antagonist (luzindole) treatment significantly suppressed all the above findings, suggesting that the proliferative effects of melatonin were mediated by a receptor-dependent pathway. In vivo results corresponded well with in vitro findings in which melatonin effectively increased the amount of proliferated Schwann cells and re-innervated MEP on target muscles following PNI. As melatonin successfully improves nerve regeneration by promoting Schwann cell proliferation, therapeutic use of melatonin may thus serve as a promising strategy to counteract the PNI-induced neuronal disability.

Mutations associated with Charcot-Marie-Tooth disease cause SIMPLE protein mislocalization and degradation by the proteasome and aggresome-autophagy pathways

Mutations in SIMPLE cause an autosomal dominant, demyelinating form of peripheral neuropathy termed Charcot-Marie-Tooth disease type 1C (CMT1C), but the pathogenic mechanisms of these mutations remain unknown. Here, we report that SIMPLE is an early endosomal membrane protein that is highly expressed in the peripheral nerves and Schwann cells. Our analysis has identified a transmembrane domain (TMD) embedded within the cysteine-rich (C-rich) region that anchors SIMPLE to the membrane, and suggests that SIMPLE is a post-translationally inserted, C-tail-anchored membrane protein. We found that CMT1C-linked pathogenic mutations are clustered within or around the TMD of SIMPLE and that these mutations cause mislocalization of SIMPLE from the early endosome membrane to the cytosol. The CMT1C-associated SIMPLE mutant proteins are unstable and prone to aggregation, and they are selectively degraded by both the proteasome and aggresome-autophagy pathways. Our findings suggest that SIMPLE mutations cause CMT1C peripheral neuropathy by a combination of loss-of-function and toxic gain-of-function mechanisms, and highlight the importance of both the proteasome and autophagy pathways in the clearance of CMT1C-associated mutant SIMPLE proteins.

Increased expression of the close homolog of the adhesion molecule L1 in different cell types over time after rat spinal cord contusion

The close homolog of the adhesion molecule L1 (CHL1) is important during CNS development, but a study with CHL1 knockout mice showed greater functional recovery after spinal cord injury (SCI) in its absence. We investigated CHL1 expression from 1 to 28 days after clinically relevant contusive SCI in Sprague-Dawley rats. Western blot analysis showed that CHL1 expression was significantly up-regulated at day 1 and further increased over 4 weeks after SCI. Immunohistochemistry of tissue sections showed that CHL1 in the intact spinal cord was expressed at low levels. By 1 day and through 4 weeks after SCI, CHL1 became highly expressed in NG2(+) cells. Hypertrophic GFAP(+) astrocytes also expressed CHL1 by 1 week after injury. The increase in CHL1 protein paralleled that of NG2 in the first week and GFAP between 1 and 4 weeks after injury. At 4 weeks, NG2(+) /CHL1(+) cells and GFAP(+) /CHL1(+) astrocytes were concentrated at the boundary between residual spinal cord tissue and the central lesion. NF200(+) spinal cord axons approached but did not penetrate this boundary. In contrast, CHL1(+) cells in the central lesion at 1 week and later colabeled with p75 and NG2 and were chronically associated with many NF200(+) axons, presumably axons that had sprouted in association with CHL1(+) Schwann cells infiltrating the cord after contusion. Thus, our study demonstrates up-regulation of CHL1 in multiple cell types and locations in a rat model of contusion injury and suggests that this molecule may be involved both in inhibition of axonal regeneration and in recovery processes after SCI.

The dorsal root ganglion in Friedreich's ataxia

Atrophy of dorsal root ganglia (DRG) and thinning of dorsal roots (DR) are hallmarks of Friedreich's ataxia (FRDA). Many previous authors also emphasized the selective vulnerability of larger neurons in DRG and thicker myelinated DR axons. This report is based on a systematic reexamination of DRG, DR and ventral roots (VR) in 19 genetically confirmed cases of FRDA by immunocytochemistry and single- and double-label immunofluorescence with antibodies to specific proteins of myelin, neurons and axons; S-100alpha as a marker of satellite and Schwann cells; laminin; and the iron-responsive proteins ferritin, mitochondrial ferritin, and ferroportin. Confocal images of axons and myelin allowed the quantitative analysis of fiber density and size, and the extent of DR and VR myelination. A novel technology, high-definition X-ray fluorescence (HDXRF) of polyethylene glycol-embedded fixed tissue, was used to "map" iron in DRG. Unfixed frozen tissue of DRG in three cases was available for the chemical assay of total iron. Proliferation of S-100alpha-positive satellite cells accompanied neuronal destruction in DRG of all FRDA cases. Double-label visualization of peripheral nerve myelin protein 22 and phosphorylated neurofilament protein confirmed the known loss of large myelinated DR fibers, but quantitative fiber counts per unit area did not change. The ratio of myelinated to neurofilament-positive fibers in DR rose significantly from 0.55 to 0.66. In VR of FRDA patients, fiber counts and degree of myelination did not differ from normal. Pooled histograms of axonal perimeters disclosed a shift to thinner fibers in DR, but also a modest excess of smaller axons in VR. Schwann cell cytoplasm in DR of FRDA was depleted while laminin reaction product remained prominent. Numerous small axons clustered around fewer Schwann cells. Ferritin in normal DRG localized to satellite cells, and proliferation of these cells in FRDA caused wide rims of reaction product about degenerating nerve cells. Mitochondrial ferritin was not detectable. Ferroportin was present in the cytoplasm of normal satellite cells and neurons, and in large axons of DR and VR. In FRDA, some DRG neurons lost their cytoplasmic ferroportin immunoreactivity, whereas the cytoplasm of satellite cells remained ferroportin positive. Ferroportin in DR axons disappeared in parallel with atrophy of large fibers. HDXRF of DRG detected regional and diffuse increases in iron fluorescence that matched ferritin expression in satellite cells. The observations support the conclusions that satellite cells and DRG neurons are affected by iron dysmetabolism; and that regeneration and inappropriate myelination of small axons in DR are characteristic of the disease.

Ablation of adhesion molecule L1 in mice favours Schwann cell proliferation and functional recovery after peripheral nerve injury

The adhesion molecule L1 is one of the few adhesion molecules known to be beneficial for repair processes in the adult central nervous system of vertebrates by promoting axonal growth and neuronal survival. In the peripheral nervous system, L1 is up-regulated by myelination-competent Schwann cells and regenerating axons after nerve damage but its functional role has remained unknown. Here we tested the hypothesis that L1 is, as in the central nervous system, beneficial for nerve regeneration in the peripheral nervous system by performing combined functional and histological analyses of adult L1-deficient mice (L1y/-) and wild-type (L1y/+) littermates. Contrary to our hypothesis, quantitative video-based motion analysis revealed better locomotor recovery in L1y/- than in L1y/+ mice at 4-12 weeks after transection and surgical repair of the femoral nerve. Motoneuron regeneration in L1y/- mice was also enhanced as indicated by attenuated post-traumatic loss of motoneurons, enhanced precision of motor reinnervation, larger cell bodies of regenerated motoneurons and diminished loss of inhibitory synaptic input to motoneurons. In search of mechanisms underlying the observed effects, we analysed peripheral nerves at short time-periods (3-14 days) after transection and found that Schwann cell proliferation is strongly augmented in L1y/- versus L1y/+ mice. L1-deficient Schwann cells showed increased proliferation than wild-type Schwann cells, both in vivo and in vitro. These findings suggest a novel role for L1 in nerve regeneration. We propose that L1 negatively regulates Schwann cell proliferation after nerve damage, which in turn restricts functional recovery by limiting the trophic support for regenerating motoneurons.

Surface modification and characterization of chitosan or PLGA membrane with laminin by chemical and oxygen plasma treatment for neural regeneration

Attachment to and proliferation on the substrate are deemed important considerations when Schwann cells (SCs) are to be seeded in synthetic nerve grafts. Good attachment is a prerequisite for the SCs to survive. Fast proliferation will yield large numbers of SCs in a short time, which appears to be promising for stimulating peripheral nerve regeneration. However, surface properties are the dominating factor in influencing the interactions between cells and synthetic nerve grafts. The aim of this study was to investigate the surface effects of laminin modified PLGA and chitosan membranes after chemical method and plasma treatment. Laminin, the extracellular matrix protein, is a permissive protein for SCs adhesion used in neural regeneration. The surface properties of laminin modified membranes were assayed by BCA, FTIR and XPS analysis. Results showed that laminin was covalently bonded onto the surface of both PLGA and chitosan membranes either by chemical method or by oxygen plasma treatment. The cell affinity of the laminin modified membranes was verified by Schwann cells culturing. Our results also indicate that oxygen plasma is indeed a better method to incorporate laminin onto the surface of membrane. Laminin-modified chitosan membrane significantly increases SCs attachment and affinity for directing peripheral nerve regeneration.

Adhesion and proliferation of human Schwann cells on adhesive coatings

Attachment to and proliferation on the substrate are deemed important considerations when Schwann cells (SCs) are to be seeded in synthetic nerve grafts. Attachment is a prerequisite for the SCs to survive and fast proliferation will yield large numbers of SCs in a short time, which appears promising for stimulation of peripheral nerve regeneration. The aim of the present study was to compare the adhesion and proliferation of human Schwann cells (HSCs) on different substrates. The following were selected for their suitability as an internal coating of synthetic nerve grafts; the extracellular matrix proteins fibronectin, laminin and collagen type I and the poly-electrolytes poly(d-lysine) (PDL) and poly(ethylene-imine) (PEI). On all coatings, attachment of HSCs was satisfactory and comparable, indicating that this factor is not a major consideration in choosing a suitable coating. Proliferation was best on fibronectin, laminin and PDL, and worst on collagen type I and PEI. Since nerve regeneration is enhanced by laminin and/or fibronectin, these are preferred as coatings for synthetic nerve grafts seeded with SCs.

Improved culture methods to expand Schwann cells with altered growth behaviour from CMT1A patients

A duplication of the gene for myelin protein PMP22 is by far the most common cause of the hereditary demyelinating neuropathy CMT1A. A role for PMP22 in cell growth in addition to its function as a myelin protein has been suggested because PMP22 is homologous to a gene specifically upregulated during growth arrest. Furthermore, transfected rat Schwann cells overexpressing PMP22 show reduced growth. In addition, abnormal Schwann cell differentiation has been described in nerve biopsies from CMT1A patients. To analyse whether the duplication of the PMP22 gene in CMT1A neuropathy primarily alters Schwann cell differentiation and to exclude nonspecific secondary responses, we improved human Schwann cell culturing. This allowed us long-term passaging of human Schwann cells with unchanged phenotype, assessed by expression of different Schwann cell markers. Subsequently we established Schwann cell cultures from CMT1A nerve biopsies. We find decreased proliferation of Schwann cells from different CMT1A patients in all passages. We also demonstrate PMP22 mRNA overexpression in cultured CMT1A Schwann cells. We conclude that decreased proliferation in cultured Schwann cells that carry the CMT1A duplication indicates abnormal differentiation of CMT1A Schwann cells. The identification of an abnormal phenotype of CMT1A Schwann cells in culture could possibly lead to an in vitro disease model.

Denervated skeletal muscle stimulates migration of Schwann cells from the distal stump of transected peripheral nerve: an in vivo study

We have tested the stimulation of Schwann cell migration from the distal stump of a 1 week transected sciatic nerve of adult rats by denervated skeletal muscle. Migrating Schwann cells were distinguished by the presence of non-specific cholinesterase (nChE) activity and glial fibrillary acidic protein (GFAP) at a distance of about 6 mm among denervated muscle fibres 4 weeks after insertion of the distal stump. In addition, the distal stump was introduced into the open end of a silicone chamber packed with artificial fibrin sponge (Gelaspon) soaked in homogenate from intact or denervated muscles. A larger amount of migrated Schwann cells was observed in the chambers filled with homogenate from denervated muscles. An alteration in the amounts of Schwann cells migrating into the silicone chambers observed after histochemical staining (nChE or GFAP) was supported by biochemical measurements of the nChE activity. The biochemical assessment of the nChE activity revealed the increased amounts of migrated Schwann cells in proportion to the protein contents of homogenates from the denervated muscles. In addition, heating of homogenate from the denervated muscles resulted in a diminution of Schwann cell migration. Bromodeoxyuridine incorporation did not show an increased proliferation of Schwann cells inside the chambers following application of homogenate from the denervated muscles in comparison with the homogenate from the innervated muscles. Our results suggest a stimulation of Schwann cell migration from the distal stump of the transected sciatic nerve by soluble factor(s) produced by denervated skeletal muscles.

Physiology of peripheral nerve graft incorporation

The degree of cell survival and the rate and extent of cellular migration was studied in fresh- and freeze-killed nerve grafts using an animal model with isogeneic nerve grafts performed between inbred rats. Nerve isografts 1.4 cm in length were used to bridge a 1.0 cm gap created in recipient animals. Vital fluorescent staining was used to monitor cell viability and to track cell migration between the nerve graft and the recipient host's nerve endings. The fresh nerve grafts maintained their fluorescent label, indicating that these grafts maintained their viability. The freeze-killed grafts had significantly lower cell survival, as determined by percent area of fluorescence, both 14 and 25 days after nerve grafting. The freeze-killed grafts also demonstrated a lower percentage of incorporation of labeled host cells from the proximal host nerve ending. Since the fresh nerve grafts maintained their viability, even though they were performed as nonvascularized grafts, free vascularized nerve grafts may not be necessary if a good vascular bed is present.

Antibodies to interleukin-6 inhibit Schwann cell proliferation induced by unfractionated cytokines

We have previously demonstrated that unfractionated cytokines induce proliferation of neonatal rat Schwann cells in vitro. Incubation of Schwann cells with natural or recombinant human interleukin-1 (IL-1) does not induce Schwann cell proliferation, but antibodies to IL-1 inhibit Schwann cell proliferation induced by unfractionated cytokines of human origin. In this study we investigated the effect of interleukin-6 (IL-6), another monokine, on proliferation of rat Schwann cells. Incubation of Schwann cells with recombinant (r) mouse IL-6 and two types of human rIL-6 did not induce proliferation of Schwann cells or of endoneurial fibroblasts. However, antibodies to rhIL-6 inhibited Schwann cell proliferation induced by unfractionated cytokines but had no effect on fibroblast proliferation. Addition of excess rhIL-6 to a mixture of unfractionated cytokines plus anti-rhIL-6 abrogated the inhibitory effect of the anti-rhIL-6. Therefore, IL-6 is a co-mitogen for neonatal Schwann cells in vitro.

Cold storage of peripheral nerves: an in vitro assay of cell viability and function

The development of a nerve bank as a source of donor material to repair large defects in peripheral nerve injuries requires an understanding of the influence of cold storage on cell viability and function in these potential nerve grafts. Segments of peripheral nerves from both human and rat were stored in University of Wisconsin Cold Storage Solution (UW) at 4 degrees C for < 12 h, 3 days, and 1, 2, or 3 weeks. Cellular viability was initially assessed by the degree of cellular outgrowth from explants of the stored nerves placed in culture, and then further quantitated by dissociating the cultured nerve explants and calculating the type and number of cells per milligram of peripheral nerve. Rat Schwann cells (SCs) obtained from the stored (control and 1 and 2 weeks) nerves were tested for their functional ability to myelinate dorsal root ganglion (DRG) neurons in culture. Our findings indicate that human and rat peripheral nerves contain few viable SCs and fibroblasts after 3 weeks of cold storage with the quantity of viable cells within the human cold stored peripheral nerves decreasing significantly after 1 week of cold storage. Despite their reduced number, some SCs from rat nerves stored up to 2 weeks are capable of myelinating DRG axons in culture. These results suggest that short intervals (< 1 week) of cold storage will result in potential peripheral nerve grafts containing large populations of functional cells, while long-term (> or = 3 weeks) cold stored peripheral nerves will contain few viable cells.

hsp70 synthesis in Schwann cells in response to heat shock and infection with Mycobacterium leprae

Induction of heat shock protein synthesis was monitored in murine and monkey Schwann cells exposed to elevated temperatures. Synthesis of the stress-inducible 70-kDa heat shock protein (hsp70) was detected in both murine and primate Schwann cells by metabolic labelling and by immunoblotting with a specific monoclonal antibody. hsp70 synthesis was also induced in Schwann cells after infection with Mycobacterium leprae and was detected from 24 h to 1 week postinfection. These results are discussed with respect to the possible role of heat shock proteins in immunopathological events associated with the clinical manifestations of leprosy.

Selective culture of mitotically active human Schwann cells from adult sural nerves

We devised a simple method to isolate mitotically active human Schwann cells from sural nerve biopsy specimens and expand the population in culture. Nerve fascicles were treated with cholera toxin for 7 days in culture before dissociation, which increased the cell yield at least twenty-five-fold over immediated tissue dissociation. Digesting the tissue completely with enzymes in serum-containing medium resulted in the highest cell viability, and released 2 to 6 x 10(4) cells/mg of tissue. Seeding the cells on a poly-L-lysine substrate in a small volume of serum-free medium optimized the plating efficiency. Although Schwann cells comprised 90% of the initial culture population, their numbers declined over time due to a faster mitotic rate of the fibroblasts in the presence of cholera toxin alone. However, treating the cultures with a combination of cholera toxin and forskolin, which act synergistically to elevate cyclic AMP levels, inhibited fibroblast growth without causing Schwann cell toxicity. Adding glial growth factor to the adenyl cyclase activators maximized Schwann cell proliferation, and the population rapidly and selectively expanded. Therefore, it should be possible to generate large numbers of Schwann cells from diseased nerves to study defects in cell function or from normal nerves to study the effects of Schwann cell grafts on neuronal regeneration.

Sural nerve immunoreactivity for nerve growth factor receptor in a case of localized hypertrophic neuropathy

Immunoreactivity for nerve growth factor receptor (NGFR) was examined using a monoclonal antibody against human NGFR in the sural nerve of a 24-year-old woman, affected by localized hypertrophic neuropathy (LHN). NGFR expression was correlated with electron microscopy and with immunoreactivity for S-100 protein, laminin, HLA-DR, HNK-1, P0 glycoprotein and neurofilament peptides. Our results indicate that in LHN most of whorl-forming cells are NGFR positive and S-100 protein or HLA-DR negative. These data along with the ultrastructural features suggest their origin from perineurium.

Differentiation and heterogeneity in T-antigen immortalized precursor cell lines from mouse cerebellum

Recently, various techniques have been developed to transfer oncogenes into brain cells in order to generate immortalized neural cell lines. It is of interest to establish how well such cell lines reflect their cellular origin. Here we report the characterization of sixteen cell lines from mouse cerebellum and, as a control, six cell lines from skin. Lines were established by immortalizing postnatal primary cell cultures with a retrovirus carrying a modified temperature-sensitive variant of SV40 large T antigen. The cell lines reflect many properties of the cell type from which they were derived. All of the sixteen cerebellar lines expressed one or more markers of the neural precursor cells, namely, nestin and epitopes for NG2 and A2B5. In contrast, none of the six skin lines expressed neural precursor markers. Both types of cell lines expressed vimentin and fibronectin. Differentiation occurred in some of the cerebellar lines and was enhanced in defined medium. A small percentage of cerebellar cells, usually less than 5%, was positive for a marker of differentiation, e.g., glial fibrillary acidic protein (GFAP), galactocerebroside (GalC), or L1. Expression of GFAP colocalized with that of nestin at varying levels of intensity, indicating a gradual replacement of nestin by GFAP in the cytoskeleton. Both the cells positive for precursor markers and those positive for differentiation markers tended to be located in clusters, suggesting that stochastic processes or cell-cell interactions are important for the determination of the fate of cells within a clonal cell line in vitro. The degree of differentiation seemed to correlate with a shift from serum-containing to defined medium, but not with a shift from the permissive to the nonpermissive temperature for T antigen expression. The immortalization approach described here thus allows the establishment of cell lines which are "captured" in the precursor state of the developing mouse neuroepithelium.

Immunology of peripheral nerves and response to trauma

Research in limb reconstruction using peripheral nerve tissue has been hampered by tissue rejection. In order to provide more information on the immunology of peripheral nerves, 35 specimens (26 from seven cadavers and nine from surgical biopsies) were analyzed for the presence of human leukocyte antigens (HLA), which are a key component of major histocompatibility complex class II (MHC Class II) antigens. MHC Class II antigens were noted in all human nerve specimens, and the percentage of areas of positive staining by immunohistochemistry was significantly higher (3.82% +/- 1.01%) than that of negative controls (.05% +/- 0.02%) (p less than 0.01). The negative controls consisted of serial sections that were stained in the same manner except that the primary antibody was deleted. There was no significant difference in the presence of MHC Class II antigens between sensory and mixed motor nerves or among the different HLA groups (HLA-DR, HLA-DP, HLA-DQ). A mouse model was used to evaluate the effect of trauma on the presence of MHC Class II antigens. Three weeks after transsection of the sciatic nerve there was a statistically significant increase (p less than 0.05) in the presence of MHC Class II antigens in the distal portion of the nerve (4.49% +/- 0.78%) as compared with samples from animals that had had exposure of the nerve without transsection (1.44% +/- 0.21%) or in nerves from animals that had had no surgery (1.02% +/- 0.21%). The presence of MHC Class II antigens could require more complex cross-matching for tissue transplantation. Nerve grafts that have undergone Wallerian degeneration may actually be more prone to rejection than are other peripheral nerve tissue transplants.

Establishment of Schwann cell lines by oncogene transfer

Schwann cell cultures prepared from murine sciatic nerves (MuSN), rat sciatic nerves (RSN) and murine dorsal root ganglia (MuDRG) were transformed by the introduction of oncogenes (v-arc, c-Ha-ras, and v-mos). The transformation was carried out by infection with helper-free retroviruses containing the oncogene and the neomycin-resistant gene which were produced in psi-2 cells. After G418 selection and cloning of cells showing spindle shape morphology, six different transformed cell clones, i.e., MuSN-arc, MuDRG-arc, MuDRG-ras, MuDRG-mos, RSN-arc, and RSN-mos, were established. All of the clones were labeled with antibodies to the S-100 protein and the laminin, which are specific markers for Schwann cells. Fibronectin and vimentin were not detected in these cell clones, in contrast to fibroblasts as 3T3 and Rat-2. These cell clones have been maintained with characteristics of Schwann cells for over 18 months. When RSN-mos, one of the Schwann cell clones, and rat retinas were cocultured direct cellular interaction was demonstrated. Furthermore, by the addition of conditioned medium of the RSN-mos, a prominent activity promoting neurite outgrowth in PC12 pheochromocytoma cells was observed.

The ontogenesis of Fc gamma receptors and complement receptors CR1 in human peripheral nerve

The ontogenesis of Fc gamma receptors (FcR) and C3b/C4b receptors (CR1) was studied in peripheral nerves from ten fetuses aged from 20 to 38 weeks using immunohistochemical and functional assays. Monoclonal antibodies (mAbs) against FcR and CR1 stained nerve fibers at 10 weeks of gestation and the staining intensity increased during nerve maturation. FcR and CR1 are probably expressed on Schwann cells and are early markers during the development of peripheral nerves. Functional FcR activity was detected in nerve sections before initiation of myelination, which occurs at approximately 18-19 weeks, whereas functional CR1 activity was found in the sections after myelination. Functional CR1 activity may, therefore, be related to myelin. The ontogenesis of FcR and CR1 was also studied on Schwann cells in culture from three fetuses aged 14, 16 and 19 weeks, using immunofluorescence technique with mAbs. The FcR and CR1 are lost on cultured Schwann cells. This suggests that the receptors are not intrinsic to the cells or that Schwann cells require axonal contact for the expression of FcR and CR1.

Evidence for phagosome-lysosome fusion in Mycobacterium leprae-infected murine Schwann cells

Murine Schwann cells were infected with viable armadillo-derived Mycobacterium leprae in vitro, and the lysosomal marker enzyme, acid phosphatase, was stained by the Gomori reaction. Electron microscopic analysis revealed that Schwann cells infected with M. leprae possess acid phosphatase and that lysosomes fuse with infected phagosomes.

Human fetal Schwann cells in culture: phenotypic expressions and proliferative capability

In this report we examined the phenotypic expressions and the proliferative capability of cultured human fetal Schwann cells. Antigens that were expressed included laminin, nerve growth factor receptor, neural cell adhesion molecule, S-100 protein, and that recognized by the monoclonal antibody HNK-1. In addition, HLA-A,B,C and HLA-DR, respectively, class I and class II antigens of the major histocompatibility complex, were demonstrated on Schwann cells. Mitotic capability was high, with an average of 34% of Schwann cells undergoing proliferation over a 2-day period.

Migration of Schwann cells and axons into developing chick forelimb muscles following removal of either the neural tube or the neural crest

A study has been made of the effects of neural crest and neural tube removal at the brachial level on the migration of Schwann cells and axons into the flexor digitorum profundus (fdp) and flexor carpi ulnaris (fcu) muscles of the avian forelimb. The identification of Schwann cells was based on the assumption that antibody HNK-1 uniquely labels these cells at the growing end of limb nerves. Myotubes and nerves were identified by using antibodies to myosin and to neurofilament protein, respectively. The removal of neural crest cells at stage 13 gave a complete Schwann cell-free embryo at the brachial level. Motor axons only grew to the base of the forelimb, forming a rudimentary plexus by stage 27, and failed to penetrate the limb. Removal of the neural tube at stage 13 did not prevent sensory axons from forming a plexus at the base of the limb; these axons subsequently developed into the brachialis longus inferior (bli n) and superior (bls n) nerves. By stage 27 the bli n had branched into the interosseus nerve (in n) and the medial-ulnar nerve (m-u n) trunks. However, unlike the result in control embryos, no nerves were detected amongst the developing fdp and fcu muscles, thus indicating that sensory axons do not grow into the muscles in the absence of motor axons. In contrast, Schwann cells were observed amongst the myotubes at the level of the in n and m-u nerve trunks. The present observations show that motor axons do not enter the limb bud and innervate limb muscles in the absence of Schwann cells. Furthermore, in the absence of motor axons (neural-tube-removed embryos) sensory axons still enter the limb (behind migrating Schwann cells) but fail to innervate developing muscles even though Schwann cells are present among the developing myotubes.

Specific lysis by CD8+ T cells of Schwann cells expressing Mycobacterium leprae antigens

In vitro cultured murine Schwann cells which were devoid of class I and class II gene products of the major histocompatibility complex expressed class I, though not class II, antigens after stimulation with recombinant interferon-gamma. Recombinant IFN-gamma-stimulated Schwann cells after priming with M. leprae were lysed by antigen-specific CD8+ T lymphocytes in vitro. These findings suggest that specific lysis of M. leprae-infected Schwann cells by CD8+ CTL plays a role in leprosy.

Cultures of human Schwann cells isolated from fetal nerves

We describe a technique for the preparation of highly purified populations of Schwann cells (SC) from human fetal nerves. Cultures were prepared by chemical and mechanical dissociation of human fetal sciatic nerves by modification of the method of Kreider et al. developed for newborn rat nerve. A time course analysis of some SC-associated markers at different times in vitro was performed employing immunofluorescence (IF) and immunoperoxidase (IP) to determine the percentage of SC in culture and to evaluate the maintenance of specific SC characteristics. We compared this method with that of Askanas et al. which produces enriched SC cultures by utilizing successive re-explantation of the original nerve explant. After 48 h, approximately 90% of the cells were bipolar and S-100+ and over the next two weeks about 70-80% of cells were SC by cytologic and immunocytologic criteria. At 35 days, 35% were SC, whereas less than or equal to 2.5% of 35-day-old multi-explant cultures were SC. The SC obtained by this method displayed the typical morphological and immunological characteristics: they expressed surface laminin and nerve growth factor receptors, whereas fibronectin, which is localized on fibroblast surface, was absent.

Expression of nerve growth factor receptor during human peripheral nerve development

The expression of NGF receptors on human Schwann cells during development and myelination and in culture was analyzed using a murine monoclonal antibody to human NGF receptor. Nonmyelinated femoral nerves from 13- to 14-week fetuses stained strongly for NGF receptor, whereas tissues from later stages of development showed a decrease in the staining intensity. These changes correlated with the initiation of myelination (17-19 weeks), as observed by phase-contrast and electron microscopy, and the reactivity with monoclonal antibody 4C5, a marker of mature Schwann cells. In adult nerves, only the perineurium and few endoneurial cells were stained with anti-NGF receptor antibody. Cultured human fetal Schwann cells were positive for NGF receptor by immunofluorescence irregardless of donor age or length of time in culture. The decreased staining of NGF receptor with nerve maturation may reflect a dependence of antigen expression on Schwann cell differentiation and/or neuron-Schwann cell interaction.