Glial cells influence cardiac permittivity as evidenced through in vitro and in silico models

Excitation-contraction (EC) coupling in the heart has, until recently, been solely accredited to cardiomyocytes. The inherent complexities of the heart make it difficult to examine non-muscle contributions to contraction in vivo, and conventional in vitro models fail to capture multiple features and cellular heterogeneity of the myocardium. Here, we report on the development of a 3D cardiac μTissue to investigate changes in the cellular composition of native myocardium in vitro. Cells are encapsulated within micropatterned gelatin-based hydrogels formed via visible light photocrosslinking. This system enables spatial control of the microarchitecture, perturbation of the cellular composition, and functional measures of EC coupling via video microscopy and a custom algorithm to quantify beat frequency and degree of coordination. To demonstrate the robustness of these tools and evaluate the impact of altered cell population densities on cardiac μTissues, contractility and cell morphology were assessed with the inclusion of exogenous non-myelinating Schwann cells (SCs). Results demonstrate that the addition of exogenous SCs alter cardiomyocyte EC, profoundly inhibiting the response to electrical pacing. Computational modeling of connexin-mediated coupling suggests that SCs impact cardiomyocyte resting potential and rectification following depolarization. Cardiac μTissues hold potential for examining the role of cellular heterogeneity in heart health, pathologies, and cellular therapies.

Effects of processing on structural, mechanical and biological properties of collagen-based substrates for regenerative medicine

The aim of this work was to investigate the structural features of type I collagen isoforms and collagen-based films at atomic and molecular scales, in order to evaluate whether and to what extent different protocols of slurry synthesis may change the protein structure and the final properties of the developed scaffolds. Wide Angle X-ray Scattering data on raw materials demonstrated the preferential orientation of collagen molecules in equine tendon-derived collagens, while randomly oriented molecules were found in bovine skin collagens, together with a lower crystalline degree, analyzed by the assessment of FWHM (Full Width at Half Maximum), and a certain degree of salt contamination. WAXS and FT-IR (Fourier Transform Infrared) analyses on bovine collagen-based films, showed that mechanical homogenization of slurry in acidic solution was the treatment ensuring a high content of super-organization of collagen into triple helices and a high crystalline domain into the material. In vitro tests on rat Schwannoma cells showed that Schwann cell differentiation into myelinating cells was dependent on the specific collagen film being used, and was found to be stimulated in case of homogenization-treated samples. Finally DHT/EDC crosslinking treatment was shown to affect mechanical stiffness of films depending on collagen source and processing conditions.

Chronic inhibitory effect of riluzole on trophic factor production

Riluzole is the only FDA approved drug for the treatment of amyotrophic lateral sclerosis (ALS). However, the drug affords moderate protection to ALS patients, extending life for a few months by a mechanism that remains controversial. In the presence of riluzole, astrocytes increase the production of factors protective to motor neurons. The stimulation of trophic factor production by motor neuron associated cells may contribute to riluzole's protective effect in ALS. Here, we investigated the effects of media conditioned by astrocytes and Schwann cells acutely or chronically incubated with riluzole on trophic factor-deprived motor neuron survival. While acute riluzole incubation induced CT-1 secretion by astrocytes and Schwann cells, chronic treatment stimulated a significant decrease in trophic factor production compared to untreated cultures. Accordingly, conditioned media from astrocytes and Schwann cells acutely treated with riluzole protected motor neurons from trophic factor deprivation-induced cell death. Motor neuron protection was prevented by incubation with CT-1 neutralizing antibodies. In contrast, conditioned media from astrocytes and Schwann cells chronically treated with riluzole was not protective. Acute and chronic treatment of mice with riluzole showed opposite effects on trophic factor production in spinal cord, sciatic nerve and brain. There was an increase in the production of CT-1 and GDNF in the spinal cord and CT-1 in the sciatic nerve during the first days of treatment with riluzole, but the levels dropped significantly after chronic treatment with the drug. Similar results were observed in brain for CT-1 and BDNF while there was no change in GDNF levels after riluzole treatment. Our results reveal that riluzole regulates long-lasting processes involving protein synthesis, which may be relevant for riluzole therapeutic effects. Changing the regimen of riluzole administration to favor the acute effect of the drug on trophic factor production by discontinuous long-term treatment may improve the outcome of ALS patient therapy.

[Study on expression of functional proteins related with Schwann cell of rats in acrylamide exposure and convalescent]

OBJECTIVE

To explore the changes of four functional proteins which are related to Schwan cells (SCs), including myelin-associated glycoprotein (MAG), nerve growth factor (NGF), p75 neurotrophin receptor (p75NTR) and neural cell adhesion molecule (NCAM) on damage and repair of peripheral nerve induced by acrylamide (Acr). From the changes of the protein level, some meaningful information for the mechanism of Acr neurotoxicity and the screening of biomarkers might be acquired.

METHODS

Rats were administrated with Acr at dose of 7. 5, 15 and 20 mg/kg by intraperitoneal injection for 3 weeks, high-dose group were observed for 4 weeks after 3 weeks exposure of Acr to create an animal model of peripheral nerve in injury and repair. Protein level of MAG, p75NTR, NGF and NCAM in rat sciatic nerve at the end of exposure and convalescent were measured by western blot. The level of MAG in plasma at the end of exposure and convalescent was measured by ELISA.

RESULTS

(1) Rats treated with Acr appeared peripheral nerve damage symptom and began to recover after 4 weeks. The abnormal symptoms in female group were heavier than that of males, especially the high dose group. (2) Compared with the control group, the level of MAG decreased in the medium dose group and high dose group (P < 0.05), the level of p75NTR increased in high dose group (P < 0.05). There were no significant changes in the level of NGF between the control group and treated groups of male rats. Compared with the male control group, the level of NCAM in the the high dose group increased (P < 0.05). (3) Compared with the control group, the level of plasma MAG in the high dose group decreased (P < 0.05), while that in the recovery group was slightly increased.

CONCLUSION

The changes of those functional proteins may reflect the state of the peripheral nerve damage induced by Acr. The downregulation of MAG in rat plasma may be related with that in sciatic nerve.

Nerve guidance conduits based on double-layered scaffolds of electrospun nanofibers for repairing the peripheral nervous system

Compared to the nerve guidance conduits (NGCs) constructed from a single layer of aligned nanofibers, bilayer NGCs with random and aligned nanofibers in the outer and inner layers are more robust and tear-resistant during surgical procedures thanks to an isotropic mechanical property provided by the random nanofibers. However, it remains unclear whether the random nanofibers will interfere with the aligned nanofibers to alter the extension pattern of the neurites and impede regeneration. To answer this question, we seeded dorsal root ganglia (DRG) on a double-layered scaffold, with aligned and random nanofibers on the top and bottom layers, respectively, and evaluated the outgrowth of neurites. The random nanofibers in the bottom layer exerted a negative impact on the extension of neurites projecting from the DRG, giving neurites a less ordered structure compared to those cultured on a single layer of aligned nanofibers. The negative impact of the random nanofibers could be effectively mitigated by preseeding the double-layered scaffold with Schwann cells. DRG cultured on top of such a scaffold exhibited a neurite outgrowth pattern similar to that for DRG cultured on a single layer of aligned nanofibers. We further fabricated bilayer NGCs from the double-layered scaffolds and tested their ability to facilitate nerve regeneration in a rat sciatic nerve injury model. Both histomorphometric analysis and functional characterization demonstrated that bilayer NGCs with an inner surface that was preseeded with Schwann cells could reach 54%, 64.2%, and 74.9% of the performance of isografts in terms of nerve fiber number, maximum isometric tetanic force, and mass of the extensor digitorum longus muscle, respectively. It can be concluded that the bilayer NGCs hold great potential in facilitating motor axon regeneration and functional motor recovery.

Epidermal expression of Lgr6 is dependent on nerve endings and Schwann cells

Lgr5/6 proteins are stem cell markers in various tissues. However, what determines their restricted expression pattern in these tissues remains unknown. We found that in skin, Lgr6 is not only expressed in the central isthmus, directly above the hair follicle bulge cells as reported previously, but also in the interfollicular epidermis. Lgr6 expression in skin is highly correlated with the innervation sites of cutaneous nerves. In the hair follicle, Lgr6 closely localizes with the surrounding nerve endings and their corresponding Schwann cells throughout the entire hair cycle. Furthermore, ablation of cutaneous nerves leads to degeneration of Schwann cells and diminished expression of Lgr6. Our results demonstrate that the nerve endings/Schwann cells control Lgr6 expression in skin, implying that they play a role in regulation of skin epithelial cells.

Application of Raman spectroscopy for visualizing biochemical changes during peripheral nerve injury in vitro and in vivo

Raman spectroscopy can be used for analysis of objects by detecting the vibrational spectrum using label-free methods. This imaging method was applied to analysis of peripheral nerve regeneration by examining the sciatic nerve in vitro and in vivo. Raman spectra of intact nerve tissue had three particularly important peaks in the range 2800-3000 cm-1. Spectra of injured sciatic nerves showed significant changes in the ratio of these peaks. Analysis of cellular spectra suggested that the spectrum for sciatic nerve tissue reflects the axon and myelin components of this tissue. Immunohistochemical analysis showed that the number of axons and the myelinated area were reduced at 7 days after injury and then increased by 28 days. The relative change in the axon to myelin ratio showed a similar initial increase, followed by a decrease at 28 days after injury. These changes correlated with the band intensity ratio and the changes in distribution of axon and myelin in Raman spectral analysis. Thus, our results suggest that label-free biochemical imaging with Raman spectroscopy can be used to detect turnover of axon and myelin in peripheral nerve regeneration.

A tight junction-associated Merlin-angiomotin complex mediates Merlin's regulation of mitogenic signaling and tumor suppressive functions

The Merlin/NF2 tumor suppressor restrains cell growth and tumorigenesis by controlling contact-dependent inhibition of proliferation. We have identified a tight-junction-associated protein complex comprising Merlin, Angiomotin, Patj, and Pals1. We demonstrate that Angiomotin functions downstream of Merlin and upstream of Rich1, a small GTPase Activating Protein, as a positive regulator of Rac1. Merlin, through competitive binding to Angiomotin, releases Rich1 from the Angiomotin-inhibitory complex, allowing Rich1 to inactivate Rac1, ultimately leading to attenuation of Rac1 and Ras-MAPK pathways. Patient-derived Merlin mutants show diminished binding capacities to Angiomotin and are unable to dissociate Rich1 from Angiomotin or inhibit MAPK signaling. Depletion of Angiomotin in Nf2(-/-) Schwann cells attenuates the Ras-MAPK signaling pathway, impedes cellular proliferation in vitro and tumorigenesis in vivo.

[Histomorphology observation of canine whole facial nerve treated with chemically extracted acellular methods]

OBJECTIVE

Using chemically extracted acellular methods to treat extracranial section of the canine whole facial nerve, to evaluated its effects on nerve structure and the removal extent of Schwann cells and myelin.

METHODS

Twenty whole facial nerves were exposed from 10 canines [weighing (18 +/- 3) kg]. The extracranial trunk of canine facial nerve and its branches (temporal branch, zygomatic branch, buccal branch, marginal mandibular branch, and cervical branch) were dissected under light microscope. Twenty facial nerves were divided into the experimental group (n = 12) and control group (n = 8) randomly. In experimental group, the nerve was extracted with the 3%TritonX-100 and 4% sodium deoxycholate. In control group, the nerve was not extracted. HE staining and immunofluorescence histological stainings for Hoechst33258, P75, Zero, and Laminin were performed.

RESULTS

After histological staining, it was found that myelin and Schwann cells were removed from the facial nerve while the basal lamina tube remained intact. The whole canine facial nerves (one nerve trunk and multiple nerve branches) had the similar result.

CONCLUSION

The canine whole facial nerve has natural structure (one nerve trunk and multiple nerve branches) by extracted with chemically extracted acellular methods, so it is an available graft for repairing the defect of the whole facial nerve.

The controversial nosology of benign nerve sheath tumors: neurofilament protein staining demonstrates intratumoral axons in many sporadic schwannomas

Schwannomas are benign peripheral nerve sheath tumors believed to be composed purely of cells with ultrastructural features of Schwann cells; these tumors are believed to develop eccentrically from the surface of nerves and not to contain axons, other than immediately beneath the capsule. This concept has recently been disputed in cases associated with neurofibromatosis type 2. The usual presence of intratumoral axons in neurofibromas is said to allow easy distinction from schwannomas. Eighty sporadic schwannomas (20 conventional, 20 cellular, 20 ancient, 10 gastric, and 10 plexiform) were retrieved from the authors' files. Hematoxylin-and-eosin stained slides were reviewed, diagnoses were confirmed and all tumors were stained for S-100 protein and neurofilament protein (NFP). The amount (rare, focal, multifocal, and diffuse) and distribution (central and/or peripheral) of axons within the tumors were analyzed. All tumors were strongly and diffusely positive for S-100 protein (nuclear and cytoplasmic staining). NFP-positive axons were identified in 11 of 20 (55%) conventional schwannomas (2 rare, 4 focal, 3 multifocal, and 2 diffuse; 5 central, 4 peripheral, and 2 central and peripheral) and in 15 of 20 (75%) cellular schwannomas (3 rare, 6 focal, and 6 multifocal; 12 central, 1 peripheral, and 2 central and peripheral). Of the 20 ancient schwannomas, 7 cases (35%) showed intratumoral axons, highlighted by NFP immunostaining (1 rare, 4 focal, 1 multifocal, and 1 diffuse; 4 peripheral, 2 central, and 1 central and peripheral). Most cases of gastric schwannoma showed no evidence of intratumoral axons; 9 cases (90%) were negative for NFP and only 1 case (10%) was positive (focal and central). Seven of 10 cases (70%) of plexiform schwannomas were negative for NFP, whereas only 3 cases (30%) showed positive axons (2 multifocal and 1 focal; 3 central). The unexpected but quite frequent presence of intratumoral axons in schwannomas argues against conventional views of these lesions' pathogenesis as an eccentric encapsulated lesion and raises the possibility that a more diverse cell population, perhaps more closely resembling neurofibromas, may constitute these neoplasms. Although NFP-positive axons were most often present in the conventional and cellular variants of schwannoma, their presence was also observed in a minority of ancient, gastric and plexiform schwannomas. Differentiation between neurofibroma and schwannoma in cases with overlapping cytoarchitectural features should not be based solely on the presence or absence of NFP-positive axons within a given tumor.

Schwann cell-derived factors modulate synaptic activities at developing neuromuscular synapses

Glial cells are active participants in the function, formation, and maintenance of the chemical synapse. To investigate the molecular basis of neuron-glia interactions at the peripheral synapse, we examined whether and how Schwann cell-derived factors modulate synaptic function at developing neuromuscular junctions (NMJs). Schwann cell-conditioned medium (SC-CM) from Xenopus Schwann cell cultures was collected and applied to Xenopus nerve-muscle cocultures. We found that SC-CM increased the frequency of spontaneous synaptic currents (SSCs) within 3-15 min by an average of approximately 150-fold at developing neuromuscular synapses. The increase in SSC frequency by SC-CM is a presynaptic effect independent of neuronal excitability and requires the influx of Ca2+. In contrast to its potentiating effect on spontaneous transmitter release, SC-CM suppressed the evoked transmitter release. The SC-CM effect required the presence of motoneuron soma but not protein synthesis. Using molecular weight cutoff filters and dialysis membranes, we found that the molecular weight of functional factor(s) in SC-CM was within 500 and 5000 Da. The SC-CM effect was not attributable to currently known factors that modulate synaptic efficacy, including neurotrophins, glutamate, and ATP. SC-CM also enhanced spontaneous synaptic release at developing NMJs in Xenopus tadpoles in situ. Our results suggest that Schwann cells release small molecules that enhance spontaneous synaptic activities acutely and potently at developing neuromuscular synapses, and the glial cell-enhanced spontaneous neurotransmission may contribute to synaptogenesis.

[Research about schwann cells and PLGA implanted to rat transected spinal cord]

OBJECTIVE

To investigate the recovery of rat transected spinal cord injury after implantation of Schwann cells combined with poly (lactide-co-glycolide) (PLGA).

METHODS

Schwann cells were expanded, co-cultured with PLGA for 9 days in vitro, and then analyzed with scanning electron microscope (SEM). Rat spinal cord at the level of T(9) was transected. Schwann cells labeled with BrdU and PLGA scaffold were implanted to injury site. After 1, 3, 6 months, BrdU/MBP immunohistochemistry double staining, semi-thin sections stained thionin and ultra-thin section were performed to investigate myelin renew. BBB open field locomotion, motor evoked potential (MEP), compound muscle action potential (CMAP) and somatosensory evoked potential (SEP) were recorded.

RESULTS

Schwann cells grew well on PLGA under SEM. BrdU/MBP double positive cells would been seen, remyelination was thin and formed by Schwann cells at 6 months later under electron microscope (EM). BBB behavioral tests revealed no significant difference in recovery comparing with experiment group and control group. The results of MEP, CMAP and SEP showed no significant improvement in the conduction of spinal cord.

CONCLUSIONS

There are the compatibility between Schwann cells and PLGA. Although remyelination was found in morphology, function conduction of spinal cord failed to be established.

Role of Nitric Oxide as Mediator of Nerve Injury in Inflammatory Neuropathies

Different lines of evidence suggest that nitric oxide (NO) plays a key role in the pathogenesis of inflammatory neuropathies; however, it is still unclear which structures in the peripheral nerve are the primary targets of NO-mediated nerve injury. To address this issue, we determined the expression of NO metabolites in sural nerve biopsies and in cerebrospinal fluid from patients with inflammatory neuropathies and studied the pathologic effects of NO in an in vitro model of myelinated Schwann cell-neuron cocultures. In cerebrospinal fluid samples, nitrite levels remained unaltered; however, nitrotyrosine, a marker for peroxynitrite formation, could be identified in nerve biopsies from patients with inflammatory neuropathies. In an in vitro model of Schwann cell neuron cocultures, high concentrations of NO induced robust demyelination, which was the result of NO-mediated axonal injury, whereas Schwann cell viability remained unaffected. These findings suggest that in contrast to Schwann cells, sensory neurons are the primary target of NO-mediated cytotoxicity and the loss of myelin is the result of selective damage to axons rather than a direct harmful effect to Schwann cells. Our findings imply that NO contributes to the pathologic changes seen in the inflamed peripheral nervous system, which is characterized by the features of axonal injury and subsequent myelin degradation, previously described as Wallerian-like degeneration.

Expression of CD1d Molecules by Human Schwann Cells and Potential Interactions with Immunoregulatory Invariant NK T Cells

CD1d-restricted NKT cells expressing invariant TCR alpha-chains (iNKT cells) produce both proinflammatory and anti-inflammatory cytokines rapidly upon activation, and are believed to play an important role in both host defense and immunoregulation. To address the potential implications of iNKT cell responses for infectious or inflammatory diseases of the nervous system, we investigated the expression of CD1d in human peripheral nerve. We found that CD1d was expressed on the surface of Schwann cells in situ and on primary or immortalized Schwann cell lines in culture. Schwann cells activated iNKT cells in a CD1d-dependent manner in the presence of alpha-galactosylceramide. Surprisingly, the cytokine production of iNKT cells stimulated by alpha-galactosylceramide presented by CD1d+ Schwann cells showed a predominance of Th2-associated cytokines such as IL-5 and IL-13 with a marked deficiency of proinflammatory Th1 cytokines such as IFN-gamma or TNF-alpha. Our findings suggest a mechanism by which iNKT cells may restrain inflammatory responses in peripheral nerves, and raise the possibility that the expression of CD1d by Schwann cells could be relevant in the pathogenesis of infectious and inflammatory diseases of the peripheral nervous system.

Fabrication of polymeric replicas of cell surfaces with nanoscale resolution

We report an approach for fabricating biomimetic surface replicas of cells with nanoscale resolution. Fixed cells serve as a template for a two-stage replica molding process. Cast from the template, the impression replica contains a reproduction of cellular topographical features indented into its surface, and cast from the impression replica, the relief replica contains a copy of these features protruding from its surface. Various polymers and cells can be utilized, and scanning electron microscopy, atomic force microscopy, and white light interferometry analyses confirm the replication of nanoscale features. These replicas are useful for investigating cellular function and for biomimetic tissue engineering.

Expression and functional state of the corticosteroid receptors and 11 beta-hydroxysteroid dehydrogenase type 2 in Schwann cells

To investigate the role of steroid receptors in mediating the reported effects of steroids on Schwann cell (SC) myelination and growth, we determined mRNA contents and transcriptional activities of the corticosteroid (glucocorticosteroid and mineralocorticosteroid) receptors (GR and MR) and sex steroid (progesterone, androgen, and estrogen alpha and beta) receptors in rat SC cultured under proliferative (in the presence of insulin and forskolin, which induces a high intracellular cAMP content) and quiescent conditions. We found no or very low expression and activity of the sex steroid receptors, as shown by mRNA concentrations determined with real-time PCR and transcriptional activities using transient expression of reporter plasmids in SC. These data and binding studies in SC lines demonstrated that the levels of the sex steroid receptors were the limiting factors. GR was clearly expressed (approximately 8000 sequences/ng total RNA) and functional. No significant modification in GR mRNA levels was observed, but an increase in transcriptional efficiency was recorded in proliferating cells compared with quiescent cells. MR was also significantly expressed at the mRNA level (approximately 450 sequences/ng total RNA) under the two culture conditions. No MR transcriptional activity was observed in SC, but a low specific binding of aldosterone was detected in SC lines. 11 beta-Hydroxysteroid-dehydrogenase type 2 (HSD2), an enzyme that inactivates glucocorticoids, was strongly expressed and active in quiescent SC, although in proliferating cells, HSD2 exhibited a strong decrease in activity and mRNA concentration. These data support a physiological role for HSD2 regulation of glucocorticosteroid concentrations in nerve SC.

Membrane-bound CSPG mediates growth cone outgrowth and substrate specificity by Schwann cell contact with the DRG neuron cell body and not via growth cone contact

The central nervous system and peripheral nervous system (CNS/PNS) contain factors that inhibit axon regeneration, including myelin-associated glycoprotein (MAG), the Nogo protein, and chondroitin sulfate proteoglycan (CSPG). They also contain factors that promote axon regeneration, such as nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF). Axon regeneration into and within the CNS fails because the balance of factor favors inhibiting regeneration, while in the PNS, the balance of factor favors promoting regeneration. The balance of influences in the CNS can be shifted toward promoting axon regeneration by eliminating the regeneration-inhibiting factors, overwhelming them with regeneration-promoting factors, or making axon growth cones non-receptive to regeneration-inhibiting factors. The present in vitro experiments, using adult rat dorsal root ganglion (DRG) neurons, were designed to determine whether the regeneration-inhibiting influences of Schwann cell CSPG are mediated via Schwann cell membrane contact with the DRG neuron cell body or their growth cones. The average longest neurite of neurons in cell body contact with Schwann cells was 7.4-fold shorter than those of neurons without Schwann cell-neuron cell body contact (naked neurons), and the neurites showed substrate specificity, growing only on the Schwann cell membranes and not extending onto the laminin substrate. The neurites of naked neurons showed no substrate specificity and extended over the laminin substrate, as well as onto and off the Schwann cells. After digesting the Schwann cell CSPG with the enzyme C-ABC, neurons in cell body contact with Schwann cells extended neurites the same length as those of naked neurons, and their neurites showed no substrate selectivity. Further, the neurites of naked neurons were not longer than those of naked neurons not exposed to C-ABC. These data indicate that the extent of neurite outgrowth from adult rat DRG neurons and substrate specificity of their growth cone is mediated via contact between the Schwann cell membrane-bound CSPG and the DRG neuron cell body and not with their growth cones. Further, there was no apparent influence of diffusible or substrate-bound CSPG on neurite outgrowth. These results show that eliminating the CSPG of Schwann cells in contact with the cell body of DRG neurons eliminates the sensitivity of their growth cones to the CSPG-induced outgrowth inhibition. This may in turn allow the axons of these neurons to regenerate through the dorsal roots and into the spinal cord.

[Mature cystic teratoma of the ovary with a small ganglioneuroma]

A case of ganglioneuroma arising within a cystic mature teratoma of the ovary in a 34-year-old woman is reported. Patient underwent right adnexectomy. The ovary was completely replaced by a bilocular cystic lesion, measuring 8 cm in diameter and filled with adipose tissue and pilosebaceous material. Microscopically the cyst was composed by a mature cystic teratoma containing skin with dermal appendages, fatty tissue and bronchial epithelium. Furthermore a nodule (0.5 cm in size) composed of mature ganglion cells, axons and Schwann cells, was identified. Ganglion cells were positive for NSE and synaptophysin, while Schwann cells stained positively with S100 protein and GFAP. To the best of our knowledgment this is the first reported cases of ganglioneuroma arisen within a cystic mature teratoma of the ovary.

Ultrastructural localization of alpha E-catenin in the rat sciatic nerve

Alpha E-catenin is included in the same category as alpha N-catenin, and both of them have been identified as subtypes of alpha-catenin. A previous study issued from our laboratory demonstrated that alpha N-catenin is localized in the axoplasm of unmyelinated peripheral nerves, whereas the localization of alpha E-catenin in the peripheral nervous system has not yet been reported. The present study was focused on the distribution of alpha E-catenin in the rat sciatic nerve. By electron microscopy using immunocytochemical methods, alpha E-catenin immunoreactivities were generally detected in the Schwann cell cytoplasm of unmyelinated nerve and the outer loop of myelinated nerve. Those findings suggest that alpha E-catenin may be associated with Schwann cell-Schwann cell or axon-Schwann cell contacts.

Lentiviral-mediated transfer of CNTF to schwann cells within reconstructed peripheral nerve grafts enhances adult retinal ganglion cell survival and axonal regeneration

We recently described a method for reconstituting peripheral nerve (PN) sheaths using adult Schwann cells (SCs). Reconstructed PN tissue grafted onto the cut optic nerve supports the regeneration of injured adult rat retinal ganglion cell (RGC) axons. To determine whether genetic manipulation of such grafts can further enhance regeneration, adult SCs were transduced with lentiviral vectors encoding either ciliary neurotrophic factor (LV-CNTF) or green fluorescent protein (LV-GFP). SCs expressed transgenes for at least 4 weeks after transplantation. There were high levels of CNTF mRNA and CNTF protein in PN grafts containing LV-CNTF-transduced SCs. Mean RGC survival was significantly increased with these grafts (11,863/retina) compared with LV-GFP controls (7064/retina). LV-CNTF-transduced SCs enhanced axonal regeneration to an even greater extent (3097 vs 393 RGCs/retina in LV-GFP controls). Many regenerated axons were myelinated. The use of genetically modified, reconstituted PN grafts to bridge tissue defects may provide new therapeutic strategies for the treatment of both CNS and PNS injuries.

Differential recruitment of p160 coactivators by glucocorticoid receptor between Schwann cells and astrocytes

In the nervous system, glucocorticoids can exert beneficial or noxious effects, depending on their concentration and the duration of hormonal stimulation. They exert their effects on neuronal and glial cells by means of their cognate receptor, the glucocorticoid receptor (GR), which recruits the p160 coactivator family members SRC-1 (steroid receptor coactivator 1), SRC-2, and SRC-3 after hormone binding. In this study, we investigated the molecular pathways used by the GR in cultured glial cells of the central and the peripheral nervous systems, astrocytes and Schwann cells (MSC80 cells), respectively. We performed functional studies based on transient transfection of a minimal glucocorticoid-sensitive reporter gene into the glial cells to test the influence of overexpression or selective inhibition by short interfering RNA of the three p160 coactivator family members on GR transactivation. We demonstrate that, depending on the glial cell type, GR differentially recruits p160 family members: in Schwann cells, GR recruited SRC-1a, SRC-1e, or SRC-3, whereas in astrocytes, SRC-1e and SRC-2, and to a lesser extent SRC-3, were active toward GR signaling. The C-terminal nuclear receptor-interacting domain of SRC-1a participates in its exclusion from the GR transcriptional complex in astrocytes. Immunolocalization experiments revealed a cell-specific intracellular distribution of the p160s, which was dependent on the duration of the hormonal induction. For example, within astrocytes, SRC-1 and SRC-2 were mainly nuclear, whereas SRC-3 unexpectedly localized to the lumen of the Golgi apparatus. In contrast, in Schwann cells, SRC-1 showed a nucleocytoplasmic shuttling depending on hormonal stimulation, whereas SRC-2 remained strictly nuclear and SRC-3 remained predominantly cytoplasmic. Altogether, these results highlight the cell specificity and the time dependence of p160s recruitment by the activated GR in glial cells, revealing the complexity of GR-p160 assembly in the nervous system.

Shear stress alters the expression of myelin-associated glycoprotein (MAG) and myelin basic protein (MBP) in Schwann cells

Schwann cells within a peripheral nerve respond robustly after an axonal injury. Recent results have revealed that Schwann cells undergo concurrent proliferation and apoptosis after a chronic nerve injury that is independent of axonal pathology. Although the exact nature of the stimulus that produces this Schwann cell response remains unknown, we postulated that this response may be triggered directly by mechanical stimuli. Thus, we sought to determine how pure Schwann cells responded to a sustained shear stress in the form of laminar fluid flow by evaluating for proliferation, expression of S-100, myelin-associated glycoprotein (MAG), and myelin basic protein (MBP). Immunohistochemistry demonstrated that the Schwann cells were positive for S-100, MAG, and MBP in greater than 99% of the experimental cells. Stimulated cells also revealed an increased rate of proliferation by as much as 100% (p<.001). The mRNA expression of MAG and MBP was down-regulated by 21% (p<.035) and 18% (p<.015), respectively, in experimental cells from RT-PCR assays. Furthermore, Western blot showed a down-regulation in MAG and MBP protein expression by 29% (p<.035) and 35% (p<.02), respectively. This study provides novel information regarding Schwann cell direct response to this physical stimulus that is not secondary to an axonal injury.

Pseudoglandular Elements in Schwannomas

Context.—Uncommon examples of schwannomas are seen in which a coexisting glandular component is present. The pseudoglandular schwannoma is a relatively recently described variant in which cystic spaces are lined by pseudocolumnar or cuboidal-like neoplastic Schwann cells exhibiting an epithelial-like appearance.

Objectives.—To determine the incidence of pseudoglandular elements in schwannomas, to describe the variable morphology of the schwannomas that may contain pseudoglandular elements, and to discuss the potential mechanisms of development and biological significance of these elements.

Design.—We screened 202 schwannomas from any anatomic site for the presence of pseudoglandular elements and examined these with light microscopy, immunohistochemistry, and electron microscopy.

Results.—Sixteen (7.9%) of the schwannomas contained pseudoglandular elements, which ranged from poorly to well organized in appearance and which were found in schwannomas exhibiting a wide range of morphologic appearances. The Schwann cell nature of the cells composing these elements was apparent both immunohistochemically and ultrastructurally. The frequency of proliferative activity within these elements was no greater than that observed throughout the remainder of the respective schwannomas.

Conclusions.—Our observations suggest that, rather than representing a distinct phenotypic schwannoma variant, pseudoglandular elements likely arise as a response to a degenerative phenomenon, perhaps reflecting the propensity that the Schwann cell has to palisade formation. Such elements may be found within a variety of schwannoma variants and do not appear to possess a unique growth potential.

Regular expression of osteopontin in granular cell tumor: distinctive feature among Schwannian cell tumors

For further characterization of S-100 protein-positive granular cell tumor (GCT), the expression of osteopontin (OPN) in the tumor cells was compared with other types of Schwannian cell tumors. Twenty GCT, three amputation neuromas, 12 neurilemmomas (NM) and three malignant peripheral nerve sheath tumors (MPNST) were used. In addition, two granular cell epulides were employed because of histological similarity to that of GCT. Immunohistochemistry by anti-OPN-monoclonal antibody revealed OPN-immunoreactivity in tumor cells of all GCT and stromal macrophages in neurilemmomas and one MPNST, but neither in amputation neuromas nor in granular cell epulides. All nine GCT studied by in situ hybridization (ISH) and all three GCT analyzed by reverse transcription-polymerase chain reaction (RT-PCR) were positive for OPN mRNA. In contrast, seven NM and three amputation neuromas were negative for OPN mRNA by either ISH or RT-PCR, while macrophages infiltrated in these tumors had OPN mRNA consistently. Double immunostaining for OPN and CD68, a lysosome-associated glycoprotein, showed their colocalization in tumor cells of GCT, suggesting a possible degradation of OPN by lysosomes. In conclusion, GCT among Schwannian cell tumors consistently express OPN, but its biological significance requires further investigation.

Fluorescent proteins expressed in mouse transgenic lines mark subsets of glia, neurons, macrophages, and dendritic cells for vital examination

To enable vital observation of glia at the neuromuscular junction, transgenic mice were generated that express proteins of the green fluorescent protein family under control of transcriptional regulatory sequences of the human S100B gene. Terminal Schwann cells were imaged repetitively in living animals of one of the transgenic lines to show that, except for extension and retraction of short processes, the glial coverings of the adult neuromuscular synapse are stable. In other lines, subsets of Schwann cells were labeled. The distribution of label suggests that Schwann cells at individual synapses are clonally related, a finding with implications for how these cells might be sorted during postnatal development. Other labeling patterns, some present in unique lines, included astrocytes, microglia, and subsets of cerebellar Bergmann glia, spinal motor neurons, macrophages, and dendritic cells. We show that lines with labeled macrophages can be used to follow the accumulation of these cells at sites of injury.

Rearrangements of the intermediate filament GFAP in primary human schwannoma cells

Loss of the tumor suppressor protein merlin causes a variety of benign tumors such as schwannomas, meningiomas, and gliomas in man. We previously reported primary human schwannoma cells to show enhanced integrin-dependent adhesion and a hyperactivation of the small RhoGTPase Rac1. Here we show that the main intermediate filament protein of Schwann cells, the glial fibrillary acidic protein, is collapsed to the perinuclear region instead of being well-spread from the nucleus to the cell periphery. This cytoskeletal reorganization is accompanied by changes in cell shape and increased cell motility. Moreover, we report tyrosine phosphorylation to be enhanced in schwannoma cells, already described earlier in intermediate filament breakdown. Thus, we believe that Rac activation via tyrosine kinase stimulation leads to GFAP collapse in human schwannoma cells, and suggest that this process plays an important role in vivo where schwannoma cells become motile, unspecifically ensheathing extracellular matrix and forming pseudomesaxons.

Schwann cells exhibit excitotoxicity consistent with release of NMDA receptor agonists

Neurodegenerative effects of Schwann cells transplanted into the central nervous system have been observed previously. We report here that conditioned medium from Schwann cell cultures exhibit degenerative influences on hippocampal neurons. Aliquots of Schwann cell-conditioned medium compromised the morphologic integrity of the neurons, markedly elevated their intracellular calcium concentrations, and decreased their viability. The degenerative effects of Schwann cell medium on neuronal morphology and viability were blocked by N-methyl-D-aspartate (NMDA) receptor antagonists D-(-)-2-amino-5-phosphonopentanoic acid (D-APV) and 5,7-dicholorokynurenic acid (DCKA). Glutamate was detected in Schwann cell-conditioned medium at a concentration on the order of 10(-5) M. D-Amino acid oxidase (DAAOx) also attenuated the neurotoxicity exhibited by Schwann cells. These data suggest that Schwann cells release biologically relevant concentrations of excitotoxins that include glutamate and D-serine.

Schwann cells upregulate vascular endothelial growth factor secondary to chronic nerve compression injury

To better understand the pathogenesis of chronic nerve compression injuries, we investigated the possibility that Schwann cell production of vascular endothelial growth factor (VEGF) is responsible for the increased vascularity and Schwann cell proliferation associated with chronic nerve injury. In situ hybridization was used to evaluate VEGF mRNA production with immunohistochemistry to further localize the production of VEGF and its receptor proteins in an animal model of chronic nerve compression injury. VEGF mRNA and protein expression increased within Schwann cells as early as 2 weeks after compression and peaked by 1 month with a subsequent marked increase in the number of blood vessels. Thus, chronic nerve compression injury induces Schwann cells to increase VEGF production, which may be responsible for changes in neural vasculature secondary to chronic nerve compression injury. With a better understanding of these nerve injuries, more effective treatments may be developed to help patients with these impairments.

Biocompatibility of NGF-grafted GTG membranes for peripheral nerve repair using cultured Schwann cells

We previously developed a biodegradable composite with potentially good biocompatibility composed by tricalcium phosphate and gluataraldehyde cross-linking gelatin (GTG) with good mechanical property feasible for surgical manipulation. The purpose of this study was to evaluate the feasibility of immobilizing nerve growth factor (NGF) onto the composite (GTG) with carbodiimide (GEN composite). Cultured Schwann cells were seeded onto the GTG and GEN composites. For comparison, GTG membrane soaked in NGF solution without carbodiimide (GN composite) as cross-linking agent was also used to culture Schwann cells. Cell morphology was observed by a scanning electron microscope. Cell survival, cytotoxicity and cellular metabolism on the NGF-grafted GTG membrane were assessed quantitatively in terms of cell protein content, leakage of cytosolic lactate dehydrogenase (LDH) activity and by the well-established MTT assay, respectively. The result of LDH study did not show significant difference among GTG, NGF-modified GTG and control group. This indicated that GTG composite, whether cross-linking with NGF or not, has little cytotoxic effect. Comparing the protein content and MTT assay among GEN, GN composite and control group, the data confirmed more attachment of Schwann cells on GEN composite. Although GTG cross-linking with NGF did not promote Schwann cell proliferation, the techniques we used in this study provided a method to fabricate a novel biomaterial incorporation of Schwann cells and covalently immobilized NGF.

Upregulation of osteopontin in Schwann cells of the sciatic nerves of Lewis rats with experimental autoimmune neuritis

We examined the expression of osteopontin (OPN) in the sciatic nerves of rats with experimental autoimmune neuritis (EAN), using immunohistochemistry and immunoblotting, to study its involvement in the pathogenesis of autoimmune peripheral nervous system diseases. Constitutive OPN expression was detected in some Schwann cells; expression was increased after immunization with adjuvant alone. At day 14 after induction of EAN, many Schwann cells had a granular pattern of immunoreactivity, whereas very few inflammatory cells were OPN-positive. Even after recovery from hindlimb paralysis, at 24 days post-immunization, OPN expression remained elevated in the Schwann cells. The results suggest that OPN expression in Schwann cells is easily induced by immunostimulation, and further enhanced by the inflammatory reaction in EAN. Continued elevation of OPN after recovery may represent a functional recovery after a transient inflammatory insult.

Molecular profiling of malignant peripheral nerve sheath tumors associated with neurofibromatosis type 1, based on large-scale real-time RT-PCR

Background

Neurofibromatosis type 1 (NF1) is an autosomal dominant disorder with a complex range of clinical symptoms. The hallmark of NF1 is the onset of heterogeneous (dermal or plexiform) benign neurofibromas. Plexiform neurofibromas can give rise to malignant peripheral nerve sheath tumors (MPNSTs), and the underlying molecular mechanisms are largely unknown.

Results

To obtain further insight into the molecular pathogenesis of MPNSTs, we used real-time quantitative RT-PCR to quantify the mRNA expression of 489 selected genes in MPNSTs, in comparison with plexiform neurofibromas.

The expression of 28 (5.7%) of the 489 genes was significantly different between MPNSTs and plexiform neurofibromas; 16 genes were upregulated and 12 were downregulated in MPNSTs.

The altered genes were mainly involved in cell proliferation (MKI67, TOP2A, CCNE2), senescence (TERT, TERC), apoptosis (BIRC5/Survivin, TP73) and extracellular matrix remodeling (MMP13, MMP9, TIMP4, ITGB4). More interestingly, other genes were involved in the Ras signaling pathway (RASSF2, HMMR/RHAMM) and the Hedgehog-Gli signaling pathway (DHH, PTCH2). Several of the down-regulated genes were Schwann cell-specific (L1CAM, MPZ, S100B, SOX10, ERBB3) or mast cell-specific (CMA1, TPSB), pointing to a depletion and/or dedifferentiation of Schwann cells and mast cells during malignant transformation of plexiform neurofibromas.

Conclusion

These data suggest that a limited number of signaling pathways, and particularly the Hedgehog-Gli signaling pathway, may be involved in malignant transformation of plexiform neurofibromas. Some of the relevant genes or their products warrant further investigation as potential therapeutic targets in NF1.

Metastasis-associated S100A4 (Mts1) protein is expressed in subpopulations of sensory and autonomic neurons and in Schwann cells of the adult rat

S100A4 (Mts1) is a member of a family of calcium-binding proteins of the EF-hand type, which are widely expressed in the nervous system, where they appear to be involved in the regulation of neuron survival, plasticity, and response to injury or disease. S100A4 has previously been demonstrated in astrocytes of the white matter and rostral migratory stream of the adult rat. After injury, S100A4 is markedly up-regulated in affected central nervous white matter areas as well as in the periventricular area and rostral migratory stream. Here, we show that S100A4 is expressed in a subpopulation of dorsal root, trigeminal, geniculate, and nodose ganglion cells; in a subpopulation of postganglionic sympathetic and parasympathetic neurons; in chromaffin cells of the adrenal medulla; and in satellite and Schwann cells. In dorsal root ganglia, S100A4-positive cells appear to constitute a subpopulation of small ganglion neurons, a few of which coexpressed calcitonin gene-related peptide (CGRP) and Griffonia simplicifolia agglutinin (GSA) isolectin B4 (B4). S100A4 protein appears to be transported from dorsal root ganglia to the spinal cord, where it is deposited in the tract of Lissauer. After peripheral nerve or dorsal root injury, a few S100A4-positive cells coexpress CGRP, GSA, or galanin. Peripheral nerve or dorsal root injury induces a marked up-regulation of S100A4 expression in satellite cells in the ganglion and in Schwann cells at the injury site and in the distal stump. This pattern of distribution partially overlaps that of the previously studied S100B and S100A6 proteins, indicating a possible functional cooperation between these proteins. The presence of S100A4 in sensory neurons, including their processes in the central nervous system, suggests that S100A4 is involved in propagation of sensory impulses in specific fiber types.

Identification and Characterization of ZFP-57, a Novel Zinc Finger Transcription Factor in the Mammalian Peripheral Nervous System

To isolate new zinc finger genes expressed at early stages of peripheral nerve development, we have used PCR to amplify conserved zinc finger sequences. RNA from rat embryonic day 12 and 13 sciatic nerves, a stage when nerves contain Schwann cell precursors, was used to identify several genes not previously described in Schwann cells. One of them, zinc finger protein (ZFP)-57, proved to be the homologue of a mouse gene found in F9 teratocarcinoma cells. Its mRNA expression profile within embryonic and adult normal and transected peripheral nerves, and its distribution in the rest of the nervous system is described. High levels of expression are seen in embryonic nerves and spinal cord. These drop rapidly during the first few weeks after birth, a pattern mirrored in other parts of the nervous system. ZFP-57 localizes to the nucleus of Schwann and other cells. The sequence contains an N-terminal Krüppel-associated box (KRAB) domain and ZFP-57 constructs containing green fluorescent protein reveal that the protein colocalizes with heterochromatin protein 1alpha to centromeric heterochromatin in a characteristic speckled pattern in NIH3T3 cells. The KRAB domain is required for this localization, because constructs lacking it target the protein to the nucleus but not to the centromeric heterochromatin. When fused to a heterologous DNA binding domain, the KRAB domain of ZFP-57 represses transcription, and full-length ZFP-57 represses Schwann cell transcription from myelin basic protein and P(0) promoters in co-transfection assays. Zfp-57 mRNA is up-regulated in Schwann cells in response to leukemia inhibitory factor and fibroblast growth factor 2.

Caveolae localization and caveolin expressions in Schwann cells of mature rat spinal nerves

Caveolae are a specific plasmalemmal microdomain which appear as flask-like invaginations and/or vesicles attaching just beneath the plasmalemma. Caveolae are present in many cell types and are found in the Schwann cells that ensheath myelinated and unmyelinated nerve fibers of the peripheral nervous tissues. However, the precise distribution in the Schwann cell plasmalemma and the functional properties of these caveolae remains obscure. The present study revealed: (1) Caveolae are most commonly observed in the Schwann cell plasmalemma of myelinated nerve fibers. (2) Caveolae are principally located in the perikaryal plasmalemma of Schwann cells of the myelinated nerves. (3) Caveolin-1 is expressed strongly in Schwann cell caveolae. (4) Caveolin 2 and 3 are also immunohistochemically detected in Schwann cell caveolae, although the immunoreactivities are slight. The results suggested that caveolae of the peripheral nervous system are involved in cellular activities specific to Schwann cells in myelinated nerve fibers. These caveolae may contain receptors for signaling molecules that could affect the myelinated nerve fibers, and/or proteins related to ion transfer activity. Further studies are necessary in order to clarify the types of proteins associated with Schwann cell caveolae.

[Integrin alpha6 beta4 and experimental allergic neuritis]

OBJECTIVE

To explore the relationship between integrins alpha6,beta4 and the process of the injury and repair of the myelin, their expressions in experimental allergic neuritis were analyzed.

METHODS

Experimental allergic neuritis (EAN) models were induced in Lewis rats. The expressions of integrins alpha6 and beta 4 and their receptor laminin, both in the acute phase and recovery phase of EANs, were analyzed by in situ hybridization and immunohistochemistry.

RESULTS

The expression of beta4 decreased in the acute phase P<0.05 and showed no significant changes in the recovery phase(P=0.6840). There were no significant changes of the expression of alpha6 and laminin both in the acute phase and recovery phase of EANs by immunohistochemistry (alpha6 P=0.0751;laminin P=0.2047). The similar results were obtained by in situ hybridization (beta4 in acute phase P<0.05;beta4 in recovery phase P=0.823;alpha6 P= 0.81).

CONCLUSION

The expressions of integrins of Schwann cells were affected by inflammation injury, and their patterns of expression were similar to those of integrins alpha6, beta1 and beta4 during embryogenesis. It is inferred that integrin beta4 and the reformation of myelin have a more imitate relationship. The expression changes of alpha6 and beta4 correlate with the injury and repair of myelin during EAN.

Matrix metalloproteinase-dependent shedding of syndecan-3, a transmembrane heparan sulfate proteoglycan, in Schwann cells

Schwann cells transiently express the transmembrane heparan sulfate proteoglycan syndecan-3 during the late embryonic and early postnatal periods of peripheral nerve development. Neonatal rat Schwann cells released soluble syndecan-3 into the culture medium by a process that was blocked by inhibition of endogenous matrix metalloproteinase activity. When Schwann cells were plated on a substratum that binds syndecan-3, the released proteoglycan bound to the substratum adjacent to the cell border. Membrane-anchored syndecan-3 was concentrated in actin-containing filopodia that projected from the lateral edges of the Schwann cell membrane. Membrane shedding was specific for syndecan-3 and was not observed for the related proteoglycan syndecan-1. Analysis of Schwann cells transfected with wild-type and chimeric syndecan-1 and syndecan-3 cDNAs revealed that membrane shedding was a property of the syndecan-3 ectodomain. Inhibition of syndecan-3 release significantly enhanced Schwann cell adhesion and process extension on dishes coated with the non-collagenous N-terminal domain of alpha4(V) collagen, which binds syndecan-3 and mediates heparan sulfate-dependent Schwann cell adhesion. Matrix metalloproteinase-dependent syndecan-3 shedding was also observed in newborn rat peripheral nerve tissue. Syndecan-3 shedding in peripheral nerve tissue was age specific, and was not observed during later stages of postnatal nerve development. These results demonstrate that Schwann cell syndecan-3 is subject to matrix metalloproteinase-dependent membrane processing, which modulates the biological function of this proteoglycan.

The expression of NGFr and PGP 9.5 in leprosy reactional cutaneous lesions: an assessment of the nerve fiber status using immunostaining

The effects of reactional episodes on the cutaneous nerve fibers of leprosy patients was assessed in six patients (three with reversal reactions and three with erythema nodosum leprosum). Cryosections of cutaneous biopsy of reactional lesions taken during the episode and of another sample during the remission period were immunostained with anti-NGFr and anti-PGP 9.5 (indirect immunofluorescence). We found no significant statistical difference in the number of NGFr- and PGP 9.5-positive fibers between the reactional and post-reactional groups. A significant difference was detected between the number of NGFr and PGP 9.5-stained fibers inside of the reactional group of biopsy cryosections but this difference was ascribed to the distinct aspects of the nerve fibers displayed whether stained with anti-NGFr or with anti-PGP 9.5; NGFr-positive branches looked larger and so interpreted as containing more fibers. In addition, a substantial number NGFr-positive fibers were PGP 9.5-negative. No differences in the number of stained fibers among the distinct cutaneous regions examined (epidermis + upper dermis, mid and deep dermis) was detected. In conclusion, the number of PGP- and NGFr-positive fibers were not significantly different in the reactional and post-reactional biopsies in the present study. NGFr-staining of the nerve fibers is different from their PGP-imunoreactivity and the evaluation of the nerve fiber status on an innervated target organ should be carried out choosing markers for both components of nerve fibers (Schwann cells and axons).

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

The intrinsic capacity of Schwann cells to promote regeneration after limited peripheral nerve lesions has been successfully transferred to extensive peripheral nerve injuries and central nervous system lesions by autologous transplantation strategies. However, both the intrinsic ability of axotomized neurons to regenerate and the permissiveness of the parenchyma surrounding the acute injury site diminish over time. Therefore, the autologous transplantation mode requires a fast and effective method to isolate Schwann cells from peripheral nerve biopsies. Here, we report a method to purify p75 low affinity nerve growth factor receptor (p75LNGFr) expressing Schwann cells from peripheral nerve biopsies in adult rats using magnetic-activated cell separation (MACS). After 1 week of nerve degeneration in culture, nerve fragments were dissociated resulting in mixed cultures containing Schwann cells and fibroblasts. After incubation with specific anti-p75LNGFr antibodies and secondary magnetic bead conjugated antibodies followed by one cycle of MACS, 95% pure Schwann cell cultures were generated as confirmed by flow-cytometry and immunocytochemistry. In contrast to established methods, MACS separation of p75LNGFr expressing cells allows the reliable purification of Schwann cells within 9 days after biopsy employing direct selection of Schwann cells rather than fibroblast depletion assays. Therefore, this method represents an effective and fast means to generate autologous Schwann cells for clinical transplantation strategies aiming for axon repair and remyelination.

HSP27 is markedly induced in Schwann cell columns and associated regenerating axons

It is well known that regenerating axons enter Schwann cell (SC) columns, within which they grow to reinnervate the appropriate targets. The current study detected a marked induction of a 27-kDa heat shock protein (HSP27) in the SC columns of crush-injured rat sciatic nerves. Immunohistochemical studies showed the first appearance of strong HSP27-immunoreactive linear structures in the proximal stump near an injury site 7 h after an operation. The HSP27-immunoreactive linear structures crossed the injury site to the distal stump 2 days after the operation. They then extended in a more proximal and more distal direction and were found to have propagated through the entire length of the nerve 1 week after the operation. This pattern of expression was maintained until 3 weeks after the operation. Double-immunofluorescent labeling and confocal laser microscopy confirmed that the linear structures consisted of SC columns and associated multiple axons. The HSP27-immunoreactive SC columns expressed glial fibrillary acidic protein, but not S-100 protein. Electron microscopy and immunoelectron microscopy demonstrated that reactive Schwann cells (SCs) and the associated axons with an outgrowing profile exhibited a strong immunoreactivity to HSP27, with the former containing a greater number of bundles of intermediate filaments. It is suggested that HSP27 may play an essential role in axonal outgrowth, especially by contributing to cytoskeletal dynamics in SCs.

Optimization of Schwann cell adhesion in response to shear stress in an in vitro model for peripheral nerve tissue engineering

The design of nerve guidance channels (NGCs) is evolving to produce a favorable environment for neural regeneration. We created an in vitro model to evaluate the interactions between three centrally important components of this altered host environment: (1). Schwann cells, (2). substrate, and (3). sustained mechanical stimulus in the form of shear stress with laminar fluid flow. Preconfluent Schwann cells were plated on slides coated either with laminin, poly-D-lysine, type IV collagen, or fibronectin. These slides were placed into custom-designed, parallel-plate, flow chambers and were administered laminar fluid flow at a rate of 15 mL/min for 2 h. Schwann cell adhesion assays demonstrated that laminin (mean, 86.1%; SEM, 4.47%) and fibronectin (mean, 81.7%; SEM, 3.24%) were statistically superior to collagen type IV (mean, 57.7%; SEM, 3.96%) and poly-D-lysine (mean, 58.0%; SEM, 4.97%) (p < 0.001). Fibronectin (mean, 12.20%; SEM, 0.374%) induced statistically greater Schwann cell proliferation than did laminin (mean, 8.14%; SEM, 0.682%) (p < 0.001). Therefore, we recommend that fibronectin should be used as an important component of NGCs with further in vivo studies. As mechanical stress is an integral part of the host environment, our study is the first to incorporate this factor into an in vitro model for peripheral nerve tissue engineering.

Estrogen receptors in human pulp tissue

OBJECTIVE

The aim of this study was to evaluate the expression of estrogen receptor (ER)-alpha in human pulp tissue.

STUDY DESIGN

Tissue samples were collected from 51 teeth extracted for orthodontic reasons or from endodontically treated teeth. Immunohistochemical staining was performed with mouse antihuman ER-alpha 1D5 by using the alkaline phosphatase antialkaline phosphatase technique. Immunohistochemical reactivity was semiquantitatively assessed and graded on an intensity scale of 0 to 3.

RESULTS

ERs were found in odontoblasts, endothelial cells, and Schwann cells. By means of statistical analysis, ERs were found to be common in odontoblasts (1.3-1.6) and in endothelial cells (1.0-1.4), whereas in Schwann cells they were somewhat rare (0.7-1.1). Difference in expression of ERs was not found among patients in different age groups. With respect to sex, a difference in reactivity was observed in Schwann cells, which showed higher reactivity in female pulps.

CONCLUSION

The results of this study confirm the expression of ER-alpha in the human dental pulp.

In vivo proliferation, migration and phenotypic changes of Schwann cells in the presence of myelinated fibers

Following injury to a peripheral nerve, changes in the behavior of Schwann cells help to define the subsequent microenvironment for regeneration. Such changes, however, have almost exclusively been considered in the context of Wallerian degeneration distal to an injury, where loss of axonal contact or input is thought to be critical to the changes that occur. This supposition, however, may be incorrect in the proximal stumps where axons are still in contact with their cell bodies. In this work, we studied aspects of in vivo Schwann cell behavior after injury within the microenvironment of proximal stumps of transected rat sciatic nerves, where axons are preserved. In particular we studied this microenvironment proximal to the outgrowth zone, in an area containing intact myelinated fibers and a perineurial layer, by using double immunolabelling of Schwann cell markers and 5-bromo-2'-deoxyuridine (BrdU) labeling of proliferating cells. In normal sciatic nerve, Schwann cells were differentiated, in an orderly fashion, into those associated with unmyelinated fibers that labeled with glial fibrillary acidic protein (GFAP) and those associated with myelinated fibers that could be identified by individual axons and myelin sheaths. After sciatic nerve transection, there was rapid and early expansion in the population of GFAP-labeled cells in proximal stumps that was generated in part, by de novo expression of GFAP in Schwann cells of myelinated fibers. Schwann cells from this population also underwent proliferation, indicated by progressive rises in BrdU and GFAP double labeling. Finally, this Schwann cell pool also developed the property of migration, traveling to the distal outgrowth zone, but also with lateral penetration into the perineurium and epineurium, while in intimate contact with new axons. The findings suggest that other signals, in the injured proximal nerve stumps, beyond actual loss of axons, induce 'mature' Schwann cells of myelinated axons to dedifferentiate into those that up-regulated their GFAP expression, proliferate and migrate with axons.

A possible paracrine hedgehog signalling pathway in neurofibromas from patients with neurofibromatosis type 1

BACKGROUND

Hedgehogs (Hhs) and their receptors are involved in organ development as well as in tumorigenesis observed in basal cell carcinoma. Among Hhs, Desert hedgehog secreted from Schwann cells mediates the formation of peripheral nerve sheaths. However, there has been no study on the role of Hhs and their receptors in tumorigenesis of neurofibromas in neurofibromatosis type 1 (NF1).

OBJECTIVES

To clarify the expression and localization of Hhs and their receptors in neurofibromas of NF1 patients.

METHODS

Expression of Hhs and their receptors was studied by immunohistochemistry using neurofibromas from NF1 patients and control normal skin samples.

RESULTS

In neurofibromas, CD57-positive tumour cells with delicate elongated processes were positive for the receptor PTCH2. Perineurial cells of involved nerves within neurofibromas as well as those of normal cutaneous nerves expressed Indian hedgehog and Sonic hedgehog. Schwann cells of normal cutaneous nerves were positive for PTCH2.

CONCLUSIONS

Our study suggests that a paracrine Hh signalling pathway may be involved in tumorigenesis of neurofibromas in NF1.

Identification of PINCH in Schwann cells and DRG neurons: shuttling and signaling after nerve injury

Particularly interesting new cysteine-histidine rich protein (PINCH) is a double zinc finger domain (LIM)-only adapter protein that functions to recruit the integrin-linked kinase (ILK) to sites of integrin activation. Genetic studies have shown that PINCH and ILK are required for integrin signaling. Since integrin activation is associated with Schwann cell migration, neurite outgrowth and regeneration, this study examined PINCH in the normal peripheral nervous system and after chronic constriction injury (CCI) in adult Sprague-Dawley rats. Immunohistochemistry identified PINCH immunoreactivity in cell bodies of dorsal root ganglia (DRG) neurons, axons, satellite cells, and Schwann cells. PINCH immunostaining was localized to the membrane of uninjured DRG cell bodies consistent with its localization at a site of integrin activation. In contrast, 5 days following CCI, PINCH immunostaining was diffuse throughout the DRG cell cytoplasm. Confocal microscopy of primary and transformed Schwann cells localized PINCH in cytoplasmic, perinuclear and nuclear areas. Examination of the PINCH sequence revealed a putative leucine-rich nuclear export signal (NES) and an overlapping basic nuclear localization signal (NLS). To demonstrate nuclear export of PINCH, rabbit anti-PINCH IgG was microinjected into Schwann cell nuclei and allowed to combine with PINCH contained within the nucleus. Immunofluorescence showed that the PINCH and anti-PINCH IgG complex rapidly translocated to the cytoplasm. Treatment with leptomycin B caused nuclear accumulation of PINCH, indicating that the CRM1 pathway mediates nuclear export of PINCH. ILK activity in Schwann cells was enhanced by platelet-derived growth factor (PDGF) and tumor necrosis factor alpha. PINCH immunoprecipitates from PDGF- and TNFalpha-stimulated Schwann cells contained several high-molecular-weight threonine-phosphorylated proteins. Taken together, these results indicate that PINCH is an abundant shuttling/signaling protein in Schwann cells and DRG neurons.

Differences in the way a mammalian cell and yeast cells coordinate cell growth and cell-cycle progression

BACKGROUND

It is widely believed that cell-size checkpoints help to coordinate cell growth and cell-cycle progression, so that proliferating eukaryotic cells maintain their size. There is strong evidence for such size checkpoints in yeasts, which maintain a constant cell-size distribution as they proliferate, even though large yeast cells grow faster than small yeast cells. Moreover, when yeast cells are shifted to better or worse nutrient conditions, they alter their size threshold within one cell cycle. Populations of mammalian cells can also maintain a constant size distribution as they proliferate, but it is not known whether this depends on cell-size checkpoints.

RESULTS

We show that proliferating rat Schwann cells do not require a cell-size checkpoint to maintain a constant cell-size distribution, as, unlike yeasts, large and small Schwann cells grow at the same rate, which depends on the concentration of extracellular growth factors. In addition, when shifted from serum-free to serum-containing medium, Schwann cells take many divisions to increase their size to that appropriate to the new condition, suggesting that they do not have cell-size checkpoints similar to those in yeasts.

CONCLUSIONS

Proliferating Schwann cells and yeast cells seem to use different mechanisms to coordinate their growth with cell-cycle progression. Whereas yeast cells use cell-size checkpoints, Schwann cells apparently do not. It seems likely that many mammalian cells resemble Schwann cells in this respect.

Distinct claudins and associated PDZ proteins form different autotypic tight junctions in myelinating Schwann cells

The apposed membranes of myelinating Schwann cells are joined by several types of junctional specializations known as autotypic or reflexive junctions. These include tight, gap, and adherens junctions, all of which are found in regions of noncompact myelin: the paranodal loops, incisures of Schmidt-Lanterman, and mesaxons. The molecular components of autotypic tight junctions have not been established. Here we report that two homologues of Discs Lost-multi PDZ domain protein (MUPP)1, and Pals-associated tight junction protein (PATJ), are differentially localized in myelinating Schwann cells and associated with different claudins. PATJ is mainly found at the paranodal loops, where it colocalized with claudin-1. MUPP1 and claudin-5 colocalized in the incisures, and the COOH-terminal region of claudin-5 interacts with MUPP1 in a PSD-95/Disc Large/zona occludens (ZO)-1 (PDZ)-dependent manner. In developing nerves, claudin-5 and MUPP1 appear together in incisures during the first postnatal week, suggesting that they coassemble during myelination. Finally, we show that the incisures also contain four other PDZ proteins that are found in epithelial tight junctions, including three membrane-associated guanylate-kinase proteins (membrane-associated guanylate-kinase inverted-2, ZO-1, and ZO-2) and the adaptor protein Par-3. The presence of these different tight junction proteins in regions of noncompact myelin may be required to maintain the intricate cytoarchitecture of myelinating Schwann cells.

ATP-binding cassette transporter ABCA2 (ABC2) expression in the developing spinal cord and PNS during myelination

We examined developmental characteristics of the ATP-binding cassette transporter ABCA2 (or ABC2) -expressing cells in rat spinal cord and peripheral nerves. In adult spinal cord, ABCA2 immunoreactivity was detected in lysosome-like organelles of mature oligodendrocyte cell bodies, and a single specific band was detected by Western blot analysis. In postnatal developing spinal cord, ABCA2 immunolabeling was first detected in a small number of cells restricted to the ventral marginal area and the dorsal funiculus at birth (P0). ABCA2-positive cells were co-immunolabeled by O4, a marker for late progenitor and immature oligodendrocytes. At the same time, myelin basic protein was apparent in the same restricted regions. The number of ABCA2 and O4 co-immunolabeled cells increased quickly in both dorsal and ventral regions from P2 and reached a peak at P8. After transient expression from P0 to P8, O4 labeling in white matter tracts decreased and disappeared. In contrast, ABCA2-positive oligodendrocytes persisted in gray and white matter throughout the spinal cord into adulthood. These data suggest a role for the ABCA2 transporter in maturation of oligodendrocyte lineage cells and the onset of myelination in the central nervous system. In addition, ABCA2 immunoreactivity was detected in the ciliated region of the ependyma in the central canal from early postnatal development. ABCA2 immunoreactivity was also detected in the Schwann cell lineage in developing spinal nerves and in adult trigeminal and sciatic nerves. ABCA2 was also expressed in numerous undetermined cells distributed in para-nerve connective tissues and nerve sheaths throughout early postnatal development. These data indicate multiple levels of involvement for ABCA2 in nervous system development especially with strong evidence for a role in myelination.

NaX sodium channel is expressed in non-myelinating Schwann cells and alveolar type II cells in mice

Na(x) is an extracellular sodium-level-sensitive sodium channel expressed in the circumventricular organs in the brain, essential loci for the sodium-level homeostasis in body fluids. Here, we examined the localization of Na(x) throughout the visceral organs at the cellular level. In visceral organs including lung, heart, intestine, bladder, kidney and tongue, a subset of Schwann cells within the peripheral nerve trunks were highly positive for Na(x). An electron microscopic study indicated that these Na(x)-positive cells were non-myelinating Schwann cells. In the lung, Na(x)-positive signals were also observed in the alveolar type II cells, which actively absorb sodium and water to aid gas exchange through the alveolar surface. It was thus suggested that the Na(x) sodium channel is involved in controlling the local extracellular sodium level through sodium absorption activity.

Connexin29 expression, immunocytochemistry and freeze-fracture replica immunogold labelling (FRIL) in sciatic nerve

The recently discovered connexin29 (Cx29) was reported to be present in the central and peripheral nervous systems (CNS and PNS), and its mRNA was found in particular abundance in peripheral nerve. The expression and localization of Cx29 protein in sciatic nerve were investigated using an antibody against Cx29. The antibody recognized Cx29 in HeLa cells transfected with Cx29 cDNA, while nontransfected HeLa cells were devoid of Cx29. Immunoblotting of sciatic nerve homogenate revealed monomeric and possibly higher molecular weight forms of Cx29. These were distinguished from connexin32 (Cx32), which also is expressed in peripheral nerve. Double immunofluorescence labelling for Cx29 and Cx32 revealed only partial colocalization of the two connexins, with codistribution at intermittent, conical-shaped striations along nerve fibers. By freeze-fracture replica immunogold labelling (FRIL), Cx32 was found in gap junctions in the outermost layers of myelin, whereas Cx29-immunogold labelling was found only in the innermost layer of myelin in close association with hexagonally arranged intramembrane particle (IMP) 'rosettes' and gap junction-like clusters of IMPs. Although both Cx32 and Cx29 were detected in myelin of normal mice, only Cx29 was present in Schwann cell membranes in Cx32 knockout mice. The results confirm that Cx29 is a second connexin expressed in Schwann cells of sciatic nerve. In addition, Cx29 is present in distinctive IMP arrays in the inner most layer of myelin, adjacent to internodal axonal plasma membranes, where this connexin may have previously unrecognized functions.