Expression of neural cell adhesion molecule (NCAM) in the peripheral nerve fibers demonstrated by postembedding immunogold method on ultrathin sections. A preliminary study.

The neural cell adhesion molecule, NCAM, is thought to be necessary for the interaction between neurons, axons and glial cells, axons and target structures, and for myelination. The NCAM localization in the peripheral nerves has been less well studied. The data have shown significant differences. In this study, the distribution of the NCAM immunoreactivity in the sciatic nerves of 10- and 15-day-old Wistar rats was examined on ultrathin sections by the immunogold postembedding method. The sections were immunotested with a polyclonal antibody (Santa Cruz Biotechnology) that recognizes rat NCAM. The antibody was visualized with donkey anti-goat IgG, conjugated to 6 nm colloidal gold. NCAM immuno-like activity was found on axoplasmic profiles of myelinated and nonmyelinated axons, at non-assembled myelin lamellae, and at axo-glial junctions of the paranodes. The compact myelin and the Schwann cell cytoplasm were immunonegative. The presence of some NCAM immunoactivity on the level of the noncompact myelin membranes, deprived of the major myelin protein Po, might be associated with the mechanism of their maintenance.     

Membrane peptidases in the peripheral nervous system of the pig: their localization by immunohistochemistry at light and electron microscopic levels.

The presence and cellular localization of five membrane peptidases has been investigated in peripheral nerves, including those of the autonomic nervous system, in the pig. Endopeptidase-24.11 ("enkephalinase") peptidyl dipeptidase A, aminopeptidase N, aminopeptidase W and dipeptidyl peptidase IV were studied by both enzymic assays of membranes prepared from samples of nerve and by immunoperoxidase histochemistry at light and in two cases, endopeptidase-24.11 and aminopeptidase W, at electron microscopic levels. All five peptidases could be quantified by enzymic assay, though the activities were about 1% of those in renal microvilli and less than those of choroid plexus membranes. Endopeptidase-24.11 was associated with Schwann cell membranes in all types of nerve examined, including major nerves containing predominantly myelinated fibres as well as autonomic nerves, such as the vagus and splenic nerves and the sympathetic chain, staining being observed in membranes associated with myelinated and unmyelinated fibres. The Schwann cell location of endopeptidase-24.11 was confirmed by correlation with immunostaining for glial fibrillary acidic protein and by electron microscopy. This peptidase is known to have a wide repertoire of susceptible substrates among neuropeptides which was here shown to include vasoactive intestinal polypeptide (Km 268 microM, kcat 568 min-1), one of a number of neuropeptides present in peripheral nerve fibres. Three of the peptidases, peptidyl dipeptidase A, aminopeptidase N and dipeptidyl peptidase IV, were associated with microvessels of peripheral nerves. Aminopeptidase N was also observed in connective tissue elements, including the perineurium. Aminopeptidase W was unique among the five peptidases in having a neuronal localization. This was observed in unmyelinated and myelinated nerves and was supported by comparison with the pattern of staining observed for neurofilament protein and by electron microscopic immunoperoxidase staining. This observation was unexpected since aminopeptidase W has not been detected as a neuronal marker in the brain. Some possible roles for the membrane peptidases in peripheral nerves are discussed.     

The glial cell in the ontogenesis of the human peripheral sympathetic nervous system and in neuroblastoma]

The developmental role of glial cells in the human peripheral sympathetic nervous system is still unclear. Immunohistochemical studies on human embryos and fetuses reveal that the migrating clusters of undifferentiated neuroblasts contain sustentacular cells and are completely separated from adjacent tissues by a peripheral layer of Schwann-like cells and continuous basement membrane. This topographic distribution seems to be strategic and suggests a role of glial cells and extracellular matrix in migration and differentiation processes of undifferentiated neuroblasts. A similar distribution pattern between glial cells/extracellular matrix and neuroblasts can be observed in neuroblastomas exhibiting a microscopic nodular growth pattern, providing additional evidence that neuroblastoma represents an arrest in the differentiation/maturation of cells during the ontogenesis of the human peripheral sympathetic nervous system. Although it is commonly believed that Schwann cells in neuroblastoma arise from cells "infiltrating neoplasia", arising from peripheral nerves adjacent tumor, our ontogenetic findings suggest that the glial cell component of neuroblastoma derives from that normally associated with developing neuroblasts. We discuss the normal development of the three lineages of the human peripheral sympathetic nervous system (ganglial, neuroendocrine or chromaffin, and glial), with special emphasis on glial cells and extracellular matrix components and on the comparison between ontogenesis and neuroblastoma.     

Selective expression of L-serine synthetic enzyme 3PGDH in schwann cells, perineuronal glia, and endoneurial fibroblasts along rat sciatic nerves and its upregulation after crush injury

Non-essential amino acid L-serine functions as a highly potent, glia-derived neurotrophic factor, because it is a precursor for syntheses of proteins, other amino acids, membrane lipids, and nucleotides, and also because its biosynthetic enzyme 3-phosphoglycerate dehydrogenase (3PGDH) is preferentially expressed in particular glial cells within the brain. Here we pursued 3PGDH expression in peripheral nerves and its change after crush injury. In the pathway of rat sciatic nerves, 3PGDH was selectively expressed in non-neuronal elements: Schwann sheaths and endoneurial fibroblasts in sciatic nerves, satellite cells in dorsal root ganglia, and astrocytes and oligodendrocytes in the spinal ventral horn. In contrast, 3PGDH was immunonegative in axons, somata of spinal motoneurons and ganglion cells, and endoneurial macrophages. One week after crush injury, 3PGDH was upregulated in the distal segment of injured nerves, where 3PGDH was intensified in activated Schwann cells and fibroblasts. 3PGDH was still negative in activated macrophages, which were instead associated or surrounded by activated Schwann cells with intensified 3PGDH. These results suggest that in the peripheral nervous system, these non-neuronal cells synthesize and may supply L-serine to satisfy metabolic demands for maintenance and regeneration of peripheral nerves and for proliferation and activation of macrophages upon nerve injury.     

Immunohistochemical localization of the neural cell adhesion molecule in the rat sciatic nerve.

The neural cell adhesion molecule (NCAM) has been widely studied in the early embryonal development of the nervous system. The data about NCAM distribution in the peripheral nerves during postnatal life are scant and some controversial. In the present study, the NCAM localization in the sciatic nerves of 15-day-old Wistar rats has been studied. Semi-thin sections of the nerves were immunotested with a polyclonal antibody (Santa Cruz Biotechnology) that recognizes rat NCAM. The antibody was visualized with donkey anti-goat IgG, conjugated to 12 nm colloidal gold, and silver amplification. In the myelinated nerve fibres, the immunoreactivity was associated with the axons, mainly with their plasma membrane, which was unstained in the nodes of Ranvier. The myelin sheaths and the myelinating Schwann cells were negative. The extracellular matrix and the bundles of non-myelinated nerve fibres were immunopositive.     

Beyond neurons: evidence that immune and glial cells contribute to pathological pain states

Chronic pain can occur after peripheral nerve injury, infection, or inflammation. Under such neuropathic pain conditions, sensory processing in the affected body region becomes grossly abnormal. Despite decades of research, currently available drugs largely fail to control such pain. This review explores the possibility that the reason for this failure lies in the fact that such drugs were designed to target neurons rather than immune or glial cells. It describes how immune cells are a natural and inextricable part of skin, peripheral nerves, dorsal root ganglia, and spinal cord. It then examines how immune and glial activation may participate in the etiology and symptomatology of diverse pathological pain states in both humans and laboratory animals. Of the variety of substances released by activated immune and glial cells, proinflammatory cytokines (tumor necrosis factor, interleukin-1, interleukin-6) appear to be of special importance in the creation of peripheral nerve and neuronal hyperexcitability. Although this review focuses on immune modulation of pain, the implications are pervasive. Indeed, all nerves and neurons regardless of modality or function are likely affected by immune and glial activation in the ways described for pain.     

Hippocampal damage induced by ischemia and intra-amygdaloid kainate injection: effect on N-methyl-D-aspartate, N-(1-[2-thienyl]cyclohexyl)piperidine and glycine binding sites

The N-methyl-D-aspartate receptor channel-complex is widely distributed in the hippocampus, particularly in the CA1 region, in the terminal field of CA3 pyramidal axons and in the fascia dentata, in the terminal field of the perforant pathway. In the present study, we have examined, in the rat, the effect of specific lesions of various neuronal populations of the hippocampus on the distribution of several markers of the N-methyl-D-aspartate receptor-channel complex. Anoxic-ischemic treatment produced a destruction of CA1 pyramidal cells (postsynaptic element): this was associated with a 50% loss of N-methyl-D-aspartate, glycine and N-(1-phenylcyclohexyl)piperidine binding sites. In contrast, the destruction of CA3 pyramidal cells and their axons (presynaptic element) by kainate treatment did not induce significant changes in the density of binding sites. The present results therefore strongly support an exclusively postsynaptic localization of the N-methyl-D-aspartate receptor-channel complex in CA1; the possibility of a localization of the remaining binding sites on glial cells or interneurons is discussed. In the molecular layer of the fascia dentata, the anoxic-ischemic treatment produced a partial destruction of the median perforant pathway (presynaptic element) associated with a decrease in the density of N-methyl-D-aspartate, N-(1-[2-thienyl]cyclohexyl)piperidine and glycine binding sites; this suggests that, in contrast to CA1, in the molecular layer of the fascia dentata, N-methyl-D-aspartate receptor-binding sites are located both pre- and postsynaptically.     

Schwann cells of the olfactory nerves contain glial fibrillary acidic protein and resemble astrocytes

—Two antisera to glial fibrillary acidic protein from human brain and an antiserum to a 49 k dalton glial filament protein from human brain detected a cross-reacting antigen in the Schwann cells of the olfactory and vomeronasal nerves. The antigen was demonstrated at light- and electron-microscope levels. It was found throughout the cytoplasm and in association with cytoplasmic filaments of olfactory nerve Schwann cells in intact tissue and in Schwann cells grown in vitro.This observation, together with observations on the ultrastructure of olfactory nerve Schwann cells, relates them to central astroglia and to glial cells of the myenteric plexus, rather than to Schwann cells of other peripheral nerves. The unusual properties of olfactory nerve Schwann cells are of interest in relation to the regenerative abilities of the olfactory nerves.     

Distribution of protein tracers in the nervous system of the crayfish (Astacus astacus L.) following systemic and local application

Summary A study was made on the penetration and cellular uptake of two protein tracers, albumin labelled with Evans blue (EBA) and horseradish peroxidase (HP), in the nervous system of the crayfish following systemic and local administration. Followingsystemic injection, EBA did not diffuse freely from the cerebral vessels into the brain parenchyma. When the tracers werelocally applied on the surface of the ventral nerve cord their penetration into the nervous parenchyma was to some extent restricted by the nerve sheath. However, unlike the perineurium of vertebrate peripheral nerves, which acts as an efficient diffusion barrier, the crayfish nerve sheath allowed the diffusion of small amounts of tracers into the ganglia. The tracers could more readily penetrate into peripheral nerves in the vicinity of ganglia. Inside the ganglion the tracers spread in extracellular spaces, between glial cell membranes and reached the neuronal surfaces. The proteins were taken up by pinocytosis in glial cells, and also in axons.     

Formation of an olfactory glomerulus: morphological aspects of development and organization.

We have studied the development of olfactory nerves in the rat from their first contact with the telencephalic vesicle until the formation of glomerular structures in the olfactory bulb at early postnatal period. The study is based on serial semithin and ultrathin sections of material prepared for electron microscopy and antibodies to label radial glial cells, glial fibrillary acidic protein and Rat-401. Beginning on embryonic day 12, developing olfactory axons from the olfactory placode are accompanied by migratory cells, also derived from the olfactory placode, that reach the prospective olfactory bulb by embryonic day 13. The mass of migratory cells accumulate superficial to the telencephalic vesicle. The cells increase in number by mitotic divisions. The majority of these cells represent precursor elements that will later develop into the ensheathing cells of the olfactory nerves and olfactory nerve layer of the adult. Some migratory cells penetrate into the prospective olfactory bulb early during development. The first synaptic contacts of olfactory axons with dendritic processes in the olfactory bulb were observed at embryonic day 18. Glomerular formation is initiated by penetration of cells from the migratory mass into the prospective glomerular layer by embryonic day 20 to postnatal day 0. These cells form walls surrounding zones of high synaptic density forming protoglomeruli. Postnatally, the peripheral processes of radial glial cells branch profusely delimiting glomerular formations and transform into periglomerular astrocytes. Rat-401 stains radial glial cells from embryonic day 14. Immunoreactivity becomes restricted to the olfactory glomeruli during the first postnatal weeks and it virtually disappears by the end of the first postnatal month. We conclude that the early penetration of cells from the migratory mass into the prospective olfactory bulb, observed immediately after the first synaptic contacts were established, initiates the formation of olfactory glomeruli which becomes completed by the transformation of radial glial cells into periglomerular astrocytes.     

Peripheral nerve pathology, including aberrant Schwann cell differentiation, is ameliorated by doxycycline in a laminin-α2-deficient mouse model of congenital muscular dystrophy

The most common form of childhood congenital muscular dystrophy, Type 1A (MDC1A), is caused by mutations in the human LAMA2 gene that encodes the laminin-α2 subunit. In addition to skeletal muscle deficits, MDC1A patients typically show a loss of peripheral nerve function. To identify the mechanisms underlying this loss of nerve function, we have examined pathology and cell differentiation in sciatic nerves and ventral roots of the laminin-α2-deficient (Lama2(-/-)) mice, which are models for MDC1A. We found that, compared with wild-type, sciatic nerves of Lama2(-/-) mice had a significant increase in both proliferating (Ki67+) cells and premyelinating (Oct6+) Schwann cells, but also had a significant decrease in both immature/non-myelinating [glial fibrillary acidic protein (GFAP)(+)] and myelinating (Krox20+) Schwann cells. To extend our previous work in which we found that doxycycline, which has multiple effects on mammalian cells, improves motor behavior and more than doubles the median life-span of Lama2(-/-) mice, we also determined how nerve pathology was affected by doxycycline treatment. We found that myelinating (Krox20+) Schwann cells were significantly increased in doxycycline-treated compared with untreated sciatic nerves. In addition, doxycycline-treated peripheral nerves had significantly less pathology as measured by assays such as amount of unmyelinated or disorganized axons. This study thus identified aberrant proliferation and differentiation of Schwann cells as key components of pathogenesis in peripheral nerves and provided proof-of-concept that pharmaceutical therapy can be of potential benefit for peripheral nerve dysfunction in MDC1A.     

Transplantation of sciatic nerve segments into normal and glia-depleted spinal cords

 Although peripheral nerves are used as guides in attempts to enhance regeneration in the central nervous system (CNS), surprisingly little is known about the interface that develops between the host tissue and the transplanted or implanted peripheral nerve. This study examines host-nerve interfaces following transplantation of segments of sciatic nerve into the spinal cord under two differing conditions, one in which the spinal cord contains normal numbers of glia and one in which the glial population is reduced. The depletion of the glial population is achieved by exposing the lumbosacral region of the spinal cord in 3-day-old rats to X-rays, a model developed in this laboratory. Twenty days later, segments of fresh or frozen sciatic nerves harvested from other 3-day-old rats were transplanted into the lumbar region of spinal cord in irradiated animals and in their non-irradiated littermate controls. Following a 20-day postoperative period, the interfaces between host spinal cord and sciatic nerves were examined ultrastructurally, and pronounced differences were noted. A distinct scar composed of multiple layers of astrocyte processes completely enveloped the transplant in non-irradiated host spinal cord and confined Schwann cells and fibroblasts to the area enclosed by the scar. Terminals from axons that appeared to have traversed the transplant during this 20-day period ended blindly in the astrocytic scar. In contrast, a complete astrocytic scar failed to form around the transplant in the irradiated, glia-depleted hosts, and Schwann cells intermingled with host tissue. Some Schwann cells migrated away from the transplant, which was placed in the dorsal funiculus, along a perivascular route and extended into the gray matter. In some instances Schwann cells were observed in the ventral gray surrounding blood vessels and motoneurons. From these observations, it is clear that the formation of a distinct astrocytic barrier at the host-graft interface is greatly reduced irradiated host. The effects of astrocyte reduction on enhanced regeneration within the spinal cord are discussed. Received: 15 April 1998 / Accepted: 9 September 1998     

Minisegments of newborn rat optic nerves in vitro: gliogenesis and myelination

Summary The question of whether the development of CNS glial cells requires the presence of axons or not can be studied with in vitro systems. In order to compare the differentiation of glial cells during development in vitro with that in situ, we have selected the optic nerve, which is anatomically as well as histotypically a well defined structure. For the in vitro investigations, small explants, called minisegments, of newborn rat optic nerves were cultivated taking four major conditions into account: (1) the regular size of the minisegments should guarantee a permanent exchange of the culture medium in order to avoid cell death, (2) neither mechanical nor enzymatic dissociation of the tissue were applied, (3) the minisegments were explanted into flasks without substrate for cell adhesion and (4) the minisegments were under constant gyratory agitation. The following in situ results were obtained: optic nerves of newborn rats are morphologically characterized by the presence of naked axons, astrocytes, glial precursors, and the absence of both differentiated oligodendrocytes and myelin. At postnatal day 5 myelin sheaths are still absent. Two weeks after birth, differentiated oligodendrocytes and microglial cells are present and numerous axons are surrounded by compact myelin. The in vitro experiments show the following main results, which were obtained after 14 h, 2 d, 5 d and 14 d in culture: during time in culture, the shape of minisegment of newborn rat optic nerves undergoes drastic changes, which indicate high cellular dynamics. After 14 h in vitro, axonal profiles, cells with pyknotic nuclei as well as clusters of astrocytes and glial precursors are present. After 2 days in culture the axonal profiles disappeared and the number of degenerating cells decreased drastically. Many large cells, probably phagocytes containing inclusions and more cells are differentiated. At the stage of 5 d in vitro 4 major types of cells can be distinguished: differentiated oligodendrocytes, which form compact and loose myelin, astrocytes, large and small glioblasts and phagocytes. Immunoprecipitates for myelin basic protein and/or myelin associated glycoprotein were found in oligodendrocytes, in their processes and associated to the myelin. Processes of some astrocytes showed immunoreactive products of glial fibrillary acidic protein. After two weeks in culture, the minisegments were mostly composed of astrocytes, whereas oligodendrocytes became rare and phagocytes disappeared. It can be concluded that CNS glial cells can attain their structural and immunocytochemical characteristics in the total absence of neuronal cell bodies and axons. However, it can be speculated that neurons (or neuronal factors) could regulate the number of astrocytes and oligodendrocytes and keep these glial cells in a physiological equilibrium.     

N-acetylated alpha-linked acidic dipeptidase is expressed by non-myelinating Schwann cells in the peripheral nervous system

Summary n-acetylated alpha-linked acidic dipeptidase is a membrane-bound brain peptidase which cleaves the neuropeptiden-acetyl-aspartyl-glutamate ton-acetyl-aspartate and glutamate. In the present study, we have determined the localization ofn-acetylated alpha-linked acidic dipeptidase in the peripheral nervous system. Using enzyme assays and immunoblotting, we demonstrate that sciatic nerve, phrenic nerve, cervical dorsal root ganglion and superior cervical ganglion containn-acetylated alpha-linked acidic dipeptidase activity as well as ann-acetylated alpha-linked acidic dipeptidase-like protein. Furthermore, we show thatn-acetylated. alpha-linked acidic dipeptidase-like immunoreactivity is extensively co-localized in peripheral nerves with immunoreactivity for glial fibrillary acidic protein, a known marker for non-myelinating Schwann cells. Using electron microscopy, we demonstraten-acetylated alpha-linked acidic dipeptidase-like immunoreactivity in cell membranes of non-myelinating Schwann cells in the superior cervical ganglion. These results show thatn-acetylated alpha-linked acidic dipeptidase is expressed in the peripheral nervous system by non-myelinating Schwann cells. This cellular localization suggests thatn-acetylated alpha-linked acidic dipeptidase may be involved in the signalling between axons and Schwann cells, for example during development or regeneration.     

Peripheral autonomic nerves of human pineal organ terminate on vessels, their supposed role in the periodic secretion of pineal melatonin

Nonvisual pineal and retinal photoreceptors are synchronizing circadian and circannual periodicity to the environmental light periods in the function of various organs. Melatonin of the pineal organ is secreted at night and represents an important factor of this periodic regulation. Night illumination suppressing melatonin secretion may result in pathological events like breast and colorectal cancer. Experimental works demonstrated the role of autonomic nerves in the pineal melatonin secretion. It was supposed that mammalian pineals have lost their photoreceptor capacity that is present in submammalians, and sympathetic fibers would mediate light information from the retina to regulate melatonin secretion. Retinal afferentation may reach the organ by central nerve fibers via the pineal habenulae as well. In our earlier works we have found that the pineal organ developing from lobular evaginations of the epithalamus differs from peripheral endocrine glands and is composed of a retina-like central nervous tissue that is comprised of cone-like pinealocytes, secondary pineal neurons and glial cells. Their autonomic nerves in submammalians as well as in mammalian animals do not terminate on pineal cells, rather, they run in the meningeal septa among pineal lobules and form vasomotor nerve endings. Concerning the adult human pineal there are no detailed fine structural data about the termination of autonomic fibers, therefore, in the present work we investigated the ultrastructure of the human pineal peripheral autonomic nerve fibers. It was found, that similarly to other parts of the brain, autonomic nerves do not enter the human pineal nervous tissue itself but separated by glial limiting membranes take their course in the meningeal septa of the organ and terminate on vessels by vasomotor endings. We suppose that these autonomic vasomotor nerves serve the regulation of the pineal blood supply according to the circadian and circannual changes of the metabolic activity of the organ and support by this effect the secretion of pineal neurohormones including melatonin.     

Antigen presentation in the peripheral nervous system: Schwann cells present endogenous myelin autoantigens to lymphocytes

Schwann cells (SC) isolated from neonatal rat sciatic nerves are shown to immunogenically present foreign and exogenous autoantigen to antigen-specific syngeneic T line cells in vitro. The antigen-presenting SC express Ia antigens on their membranes upon treatment with interferon gamma and contact with syngeneic T line cells. Monoclonal antibodies against Ia block specific antigen presentation, but not polyclonal mitogenic T cell activation. The antigen-presenting SC bind antibodies specific for astrocytic glial fibrillary acidic protein and may thus be related to the nonmyelinating glia cells of the peripheral nerve. Furthermore, SC isolated from 6-day-old rats activate rat myelin basic protein (MBP)-specific syngeneic T line cells in the absence of exogenous MBP. In contrast, they activate purified protein derivative of tuberculin (PPD)-specific T cells only in the presence of PPD. Since the MBP-specific T line cells are not activated by syngeneic professional antigen-presenting cells in the absence of MBP, endogenous MBP produced in the 6-day-old sciatic nerves appears to be presented by autochthonous SC to the autoreactive T cells.     

Glial cells in transected optic nerves of immature rats. II. An immunohistochemical study

Summary The glial response to Wallerian degeneration was studied in optic nerves 21 days after unilateral enucleation (PED21) of immature rats, 21 days old (P21), using immunohistochemical labelling. Nerves from normal P21 and P42 nerves were also studied for comparison. At PED21, there was a virtual loss of axons apart from a few solitary fibres of unknown origin. The nerve comprised a homogeneous glial scar tissue formed by dense astrocyte processes, oriented parallel to the long axis of the nerve along the tracks of degenerated axons. Astrocytes were almost perfectly co-labelled by antibodies to glial fibrillary acid protein and vimentin in both normal and transected nerves. However, there was a small population of VIM⁺GFAP^– cells in normal P21 and P42 nerves, and we discuss the possibility that they correspond to O-2A progenitor cells describedin vitro. Significantly, double immunofluorescence labelling in transected nerves revealed a distinct population of hypertrophic astrocytes which were GFAP⁺VIM^–. These cells represented a novel morphological and antigenic subtype of reactive astrocyte. It was also noted that the number of oligodendrocytes in transected nerves did not appear to be less than in normal nerves, on the basis of double immunofluorescence staining for carbonic anhydrase II, myelin oligodendrocyte glycoprotein, myelin basic protein, glial fibrillary acid protein and ED-1 (for macrophages), although it was not excluded that a small proportion may have been microglia. A further prominent feature of transected nerves was that they contained a substantial amount of myelin debris, notwithstanding that OX-42 and ED1 immunostaining showed that there were abundant microglia and macrophages, sufficient for the rapid and almost complete removal of axonal debris. In conclusion, glial cells in the immature P21 rat optic nerve reacted to Wallerian degeneration in a way equivalent to the adult CNS, i.e. astrocytes underwent pronounced reactive changes and formed a dense glial scar, oligodendrocytes persisted and were not dependent on axons for their continued survival, and there was ineffective phagocytosis of myelin possibly due to incomplete activation of microglia/macrophages.     

Bcl-2 immunoreactivity in human cutaneous Meissner and Pacinian corpuscles

The occurrence and distribution of Bcl-2, a protein involved in the death-life cell pathways, was investigated in the peripheral sensory nervous system of healthy adult humans, including lumbar dorsal root ganglia, nerve trunks and glabrous skin (to analyze sensory corpuscles) using Western blot and immunohistochemistry. The antibody used labelled a protein of 26 kDa of estimated molecular weight corresponding with Bcl-2. Immunohistochemistry showed that only a neuronal population in dorsal root ganglia, some axons in peripheral nerves and the axon supplying Meissner and Pacinian corpuscles contained Bcl-2, whereas peripheral glial cells (i.e. satellite glial cells, Schwann cell, and lamellar cells of sensory corpuscles) did not. These results suggest that in normal conditions, Bcl-2 is only present in some neuronal, but not glial, elements of the sensory peripheral nervous system. The functional significance, if any, of these results remains to be determined.     

Fabrication and evaluation of microgrooved polymers as peripheral nerve conduits

Cell alignment plays an important role in the repair of damaged peripheral nerves. The aligned Schwann cells could direct the axonal outgrowth during nerve reconstruction. One way of aligning Schwann cells is to use surface grooves in micrometric dimensions. In this study, microgrooves on chitosan or poly(d,l-lactide) (PLA) were fabricated and the behaviors of Schwann cells and glial cell line C6 on these surfaces were examined. It was found that Schwann cells and C6 cells could be successfully aligned by the microgrooves, and express the genes related to the production of neurotrophic factors. The polymer conduits with microgrooves on the inner surface were implanted in rats to repair the damaged sciatic nerve. The microgrooved conduits were demonstrated to enhance peripheral nerve regeneration as compared to the smooth conduits.