The L2/HNK-1 Carbohydrate Epitope is Involved in the Preferential Outgrowth of Motor Neurons on Ventral Roots and Motor Nerves

Based on the observation that in adult mice the carbohydrate epitope L2/HNK-1 is detectable on Schwann cells in ventral spinal roots, but only scarcely in dorsal roots (Martini et al., Dev. Biol., 129, 330 - 338, 1988), the possibility was investigated that the carbohydrate is involved in the outgrowth of regenerating motor neuron axons on peripheral nerve substrates expressing the epitope. To monitor whether the L2 carbohydrate remains present during the time periods in which regenerating axons penetrate the denervated distal nerve stumps, the expression of L2 in motor and sensory branches of the femoral nerve was investigated in normal animals and after a crush lesion. During the first two postoperative weeks, L2 immunoreactivity remained high in the myelinating Schwann cells of the motor branch, whereas L2 immunoreactivity was virtually absent in the sensory branch. In a first experimental approach, cryosections of ventral and dorsal spinal roots and of motor and sensory nerves of adult rats and mice were used as substrates for neurite outgrowth. Neurites of motor neurons from chicken embryos were approximately 35% longer after 30 h of maintenance on ventral roots than on dorsal roots. Neurites from sensory neurons had the same length on dorsal as on ventral motors and were as long as neurites from motor neurons grown on dorsal roots. L2 antibodies reduced neurite outgrowth of motor neurons on ventral roots but not on dorsal roots. Neurite outgrowth of sensory neurons on both roots was not altered by the antibodies. Neurite outgrowth of motor neurons on a mixture of the extracellular matrix glycoprotein laminin and the L2 carbohydrate-carrying glycolipid was significantly higher than on the laminin substrate mixture with GD1b ganglioside or sulphatide. L2 antibodies reduced neurite outgrowth of motor neurons by 50% on the L2 glycolipid, but not on GD1b or sulphatide. These observations indicate that the L2 carbohydrate promotes neurite outgrowth of motor neurons in vitro and may thus contribute to the preferential reinnervation of motor nerves by regenerating motor axons in vivo.     

Development of the spinal nerves of the larval lamprey: IV. Spinal nerve roots of 21-mm larval and adult lampreys, with special reference to the relation of meninges with the root sheath and the perineurium

Spinal nerve roots of 21-mm larval and adult lampreys were electron microscopically studied. In 21-mm larval lampreys, each ventral and dorsal rootlet contains axons of various diameters enclosed together as groups in individual troughs of a Schwann cell cytoplasm, lying in direct contact with one another, and is further ensheathed entirely by a basal lamina. Dorsal roots possess visceral axons, while ventral roots lack them. In adult lampreys the ventral and dorsal roots possess individual sheaths for larger somatic axons, each being surrounded by a single Schwann cell and the basal lamina and separated from one another by a considerable amount of connective tissue. Visceral fibers are present in both the dorsal and ventral roots of adult lampreys. They aggregate to form fascicles that lie among somatic axons, being separated from them. Two layers of the meningeal tissue invaginate to form a root sheath around the distal portion of individual dorsal and ventral roots of 21-mm larval lampreys. In adult lampreys the sheath is similarly formed but extends over most of the dorsal and ventral roots. The perineurium is not developed in 21-mm larval lampreys, but is present and ensheaths only the proximal portion of spinal nerve trunks outside the meninges in adult lampreys: it is completely absent along most of the length of peripheral nerves. In both larval and adult lampreys, the outer cell layer of the root sheath is open-ended near the middle of nerve roots with respect to the extramedullary connective tissue space. Similar loosening of the cellular barrier is seen along blood vessels. Thus, the outer meningeal fibrous layer is directly continuous with the extra medullary connective tissue space by way of the inner fibrous layer of the root sheath.     

Demyelination and early remyelination in experimental allergic encephalomyelitis passively transferred with myelin basic protein-sensitized lymphocytes in the Lewis rat

Histological studies were performed on Lewis rats with experimental allergic encephalomyelitis (EAE) passively transferred by myelin basic protein (MBP)-sensitized syngeneic spleen cells in order to determine the relationship between demyelination and neurological signs. Neither inflammation nor demyelination was present on the day prior to the onset of neurological signs but both were present in the spinal roots and spinal cord on the day of onset of tail weakness (4 days after passive transfer). Demyelination and the neurological signs both increased over the next 48 h. There was evidence that the caudal roots were more severely affected than the rostral roots. The peripheral nerves were spared. Demyelination in the spinal cord was concentrated in the dorsal root entry and ventral root exit zones. The initial stages of repair of demyelinated spinal root fibres by Schwann cells were observed on the earliest day that clinical recovery commenced (day 7). At this time some demyelinated fibres were closely associated with debris-free Schwann cells, and occasional fibres were completely invested by 1-2 layers of Schwann cell cytoplasm. Remyelination (compact myelin lamellae formation) by Schwann cells was first observed in the spinal roots on day 9. By the time of complete clinical recovery (day 11) the majority of affected spinal root cores had thin new myelin sheaths. Repair of central nervous system myelin by oligodendrocytes was slower than peripheral nervous system myelin repair. Investment of demyelinated spinal cord axons by oligodendrocytes was observed on day 9, and remyelination by these cells was seen on day 10. We conclude that the neurological signs of passively induced MBP-EAE can be accounted for by demyelination of the lumbar, sacral and coccygeal spinal roots and spinal cord root entry and exit zones, and that the subsequent clinical recovery can be explained by investment and remyelination of demyelinated peripheral and central nervous system fibres by Schwann cells and oligodendrocytes respectively.     

Schwann cells orchestrate peripheral nerve inflammation through the expression of CSF1, IL-34, and SCF in amyotrophic lateral sclerosis

Distal axonopathy is a recognized pathological feature of amyotrophic lateral sclerosis (ALS). In the peripheral nerves of ALS patients, motor axon loss elicits a Wallerian-like degeneration characterized by denervated Schwann cells (SCs) together with immune cell infiltration. However, the pathogenic significance of denervated SCs accumulating following impaired axonal growth in ALS remains unclear. Here, we analyze SC phenotypes in sciatic nerves of ALS patients and paralytic SOD1^G93A rats, and identify remarkably similar and specific reactive SC phenotypes based on the pattern of S100β, GFAP, isolectin and/or p75^NTR immunoreactivity. Different subsets of reactive SCs expressed colony-stimulating factor-1 (CSF1) and Interleukin-34 (IL-34) and closely interacted with numerous endoneurial CSF-1R-expressing monocyte/macrophages, suggesting a paracrine mechanism of myeloid cell expansion and activation. SCs bearing phagocytic phenotypes as well as endoneurial macrophages expressed stem cell factor (SCF), a trophic factor that attracts and activates mast cells through the c-Kit receptor. Notably, a subpopulation of Ki67+ SCs expressed c-Kit in the sciatic nerves of SOD1^G93A rats, suggesting a signaling pathway that fuels SC proliferation in ALS. c-Kit+ mast cells were also abundant in the sciatic nerve from ALS donors but not in controls. Pharmacological inhibition of CSF-1R and c-Kit with masitinib in SOD1^G93A rats potently reduced SC reactivity and immune cell infiltration in the sciatic nerve and ventral roots, suggesting a mechanism by which the drug ameliorates peripheral nerve pathology. These findings provide strong evidence for a previously unknown inflammatory mechanism triggered by SCs in ALS peripheral nerves that has broad application in developing novel therapies.     

Laminin--developmental expression and role in axonal outgrowth in the peripheral nervous system of the chick.

The possible role of laminin on axon outgrowth and guidance in vivo was examined by: (1) determining its developmental expression, and relationship to outgrowth of sensory, motor and sympathetic axons in the chick embryo; and (2) evaluating the changes in the pattern of sympathetic preganglionic projections subsequent to injections of laminin, antilaminin and other laminin function blockers (JG22, INO) into their pathways during axon outgrowth. Double immunofluorescent staining for laminin and neurofilaments in peripheral nerves prior to and during initial outgrowth showed no obvious relationship between laminin and potential nerve pathways. Even though weak laminin immunostaining is apparent throughout the mesenchyme through which axons grow, the most prominent laminin immunostaining is on basement membranes of the neural tube, notochord and dermamyotome. However, as peripheral nerves mature, laminin becomes localized to nerve fascicles throughout the peripheral nervous system, beginning with the dorsal and ventral roots, and progressing later to more distal spinal nerves. Microinjections of antilaminin, JG22 (a monoclonal antibody against laminin/fibronectin receptors) and INO (a monoclonal antibody against a laminin-heparan sulfate proteoglycan complex) into the pathway of sympathetic preganglionic axons prior to and during outgrowth had no effect on the spatio-temporal patterns of sympathetic preganglionic projections. An alternate laminin-rich pathway produced by injecting laminin into the region of the sympathetic trunk immediately adjacent but caudal to the T1 spinal level also did not alter the projection of T1 preganglionic axons. These results suggest that laminin may not be crucial to the initial of peripheral axons. The localization of laminin in nerve fascicles in later stages of development suggests instead that laminin may be important in the maintenance of these structures.     

Peripheral nerve involvement in Werdnig-Hoffmann disease

The number of large myelinated axons was markedly decreased in almost all the intramuscular nerve bundles included in 32 muscle biopsies from patients with Werdnig-Hoffmann disease compared to that in normals. The morphometric analysis of peripheral nerves in 5 epon-embedded sections also showed a selective loss of larger myelinated fibers. The ultrastructural findings of the nerves were similar to those seen in Wallerian degeneration including axonal degeneration, myelin breakdown with phagocytosis, Schwann cell proliferation forming Schwann cell columns, axonal sprouting and probable remyelination. The earlier and more striking peripheral nerve involvement than that previously believed was not different from that seen in amyotrophic lateral sclerosis (ALS). The earlier damage to the peripheral nerves probably resulted from a degeneration of the anterior horn cells or anterior spinal roots as in ALS rather than from a dying-back process.     

Upregulation of B-50/GAP-43 in Schwann cells at denervated motor endplates and in motoneurons after rat facial nerve crush

Crush or transection of peripheral nerves of the adult rat is accompanied by changes in protein expression, including the growth associated protein (GAP-43) B-50. Following peripheral nerve crush in rat enhanced B-50 immunoreactivity was observed in regenerating nerve fibres and in newly formed axon terminals. However, before reinnervation was apparent, an unexpected transient increase in B-50 immunoreactivity was observed at denervated motor endplates [J. Neurosci. 8 (1988) 1759]. This study was performed to clarify this observation. Four days following facial nerve crush B-50 immunoreactivity was detected by double immunofluorescence microscopy in Sl00-positive Schwann cells covering the denervated endplates. Using diluted polyclonal and monoclonal B-50 antibodies we found that B-50 immunoreactivity at the denervated motor endplates was strongly increased in comparison to innervated motor endplates in which B-50 immunoreactivity was hardly detectable. However, when a high concentration of B-50 antibodies was applied the normal innervated motor endplates were also B-50 immunoreactive. Muscle fibres did not display B-50 immunoreactivity. Northern blot analysis revealed elevated B-50 mRNA in denervated muscle and in degenerating nerve with respect to the controls. The B-50 mRNA levels in these non-neuronal tissues were very low compared to the intact and injured facial nucleus containing the neuronal cell bodies. Electron microscopy demonstrated that the B-50 protein was localized in the processes of Schwann cells covering axon terminals of intact and vacant motor endplates and in axon varicosities of sympathetic nerves. This study has confirmed that prior to reinnervation B-50 immunoreactivity is increased at denervated motor endplates and shows that B-50 is co-localized with S100 in Schwann cells. Therefore, upregulation of B-50 expression in Schwann cells may explain the early occurrence of B-50 immunoreactivity at the motor endplate.     

Expression of ciliary neurotrophic factor is maintained in spinal motor neurons of amyotrophic lateral sclerosis

Ciliary neurotrophic factor (CNTF) was originally identified as a potent survival factor for a variety of neuronal cell types in vitro and in vivo and in particular in spinal motor neurons of embryonic chick and rat. Using a monoclonal antibody against CNTF (clone 4–68) we analysed the expression of CNTF in paraffin sections of seven human brains and spinal cords immunocytochemically using the ABC method and compared these results with sections of the spinal cords of patients suffering from amyotrophic lateral sclerosis (ALS). In normal human tissue of the central nervous system CNTF immunoreactivity was found in most of the motor neurons of the motor cortex and ventral horn, neurons of the nucleus oculomotorius, intermediolateralis, thoracicus, ependymal cells as well as in smooth muscle cells and endothelial cells of small arteries. A reduced number of astrocytes showed a positive immunocytochemical reaction. In peripheral nerves and nerve roots of the spinal cord we also found a positive staining of Schwann cells and some axons. These immunoreactions could be confirmed by Western blot analyses. Next we analysed postmortem paraffin sections of the spinal cord of seven patients suffering from ALS (age range 30–76 years, median age 46 years, female/male = 4:3). We found CNTF immunoreactivity in most of the motor neurons of the ventral horn in 5 cases. In two cases the number of positively stained motor neurons was less. From these results we conclude that CNTF is expressed in a high number of upper and lower motor neurons in the human CNS and that its expression is maintained in ALS patients.     

神经节苷脂在SD大鼠周围神经中分布的实验研究

目的了解神经节苷脂在大鼠的运动和感觉神经中的分布情况,为阐明与神经节苷脂抗体有关的周围神经疾病的发病机制提供实验依据。方法应用免疫组化技术对正常SD大鼠的脊髓前根和后根进行免疫组化染色,并对两者进行比较。结果神经节苷脂存在于大鼠周围神经的轴索中,运动和感觉神经比较无明显差异。结论SD大鼠运动和感觉神经中神经节苷脂的分布无差异,神经节苷脂成分并非急性运动性轴索型神经病等周围神经疾病中运动轴索选择性受累的主要原因。     

α‐Synuclein pathology in the cranial and spinal nerves in Lewy body disease

Accumulation of phosphorylated α‐synuclein in neurons and glial cells is a histological hallmark of Lewy body disease (LBD) and multiple system atrophy (MSA). Recently, filamentous aggregations of phosphorylated α‐synuclein have been reported in the cytoplasm of Schwann cells, but not in axons, in the peripheral nervous system in MSA, mainly in the cranial and spinal nerve roots. Here we conducted an immunohistochemical investigation of the cranial and spinal nerves and dorsal root ganglia of patients with LBD. Lewy axons were found in the oculomotor, trigeminal and glossopharyngeal‐vagus nerves, but not in the hypoglossal nerve. The glossopharyngeal‐vagus nerves were most frequently affected, with involvement in all of 20 subjects. In the spinal nerve roots, Lewy axons were found in all of the cases examined. Lewy axons in the anterior nerves were more frequent and numerous in the thoracic and sacral segments than in the cervical and lumbar segments. On the other hand, axonal lesions in the posterior spinal nerve roots appeared to increase along a cervical‐to‐sacral gradient. Although Schwann cell cytoplasmic inclusions were found in the spinal nerves, they were only minimal. In the dorsal root ganglia, axonal lesions were seldom evident. These findings indicate that α‐synuclein pathology in the peripheral nerves is axonal‐predominant in LBD, whereas it is restricted to glial cells in MSA.     

THE EFFECT OF SUB-DURAL NERVE TISSUE TRANSPLANTATION ON THE SPINAL CORD OF THE RAT

Blakemore W.F. (1980) Neuropathology and Applied Neurobiology 6, 433–447
The effect of sub-dural nerve transplantation on the spinal cord of the rat
The effects of sub-dural transplantation of autologous sciatic nerve on the dorsal columns of the rat was investigated. Combinations of the following procedures were used: 1 local X-irradiation with 4000 rad to suppress inherent remyelination activity; 2 small areas of primary demyelination induced by injection of lysolecithin or 6-aminonicotinamide; 3 transplantation of untreated or freeze-killed nerve, either teased or unteased. The lesions formed were examined for suppression of remyelination by local cells, remyelination by transplanted Schwann cells, deleterious effects of transplantation on the spinal cord, and the presence of suprapial nerve fibres. The following conclusions were drawn: 1 that 4000 rad of local X-irradiation suppresses inherent remyelination by oligodendroglia and local Schwann cells even when transplanted freeze-killed sciatic nerve is present; 2 that demyelinated axons can be remyelinated by Schwann cells from transplanted untreated nerve; 3 that the placing of peripheral nerve over the dorsal columns induces primary demyelination in both irradiated and non-irradiated animals; 4 that the placing of peripheral nerve over demyelinated locally X-irradiated spinal cord can lead to fibrous tissue invasion of the spinal cord and partial demyelination of the lateral and ventral columns; and 5 that transplantation of viable peripheral nerve onto the dorsal columns induces the formation of suprapial nerve fibres, which increase in number if demyelination or axonal damage is present in the dorsal columns. It seems probable, therefore, that elements in the peripheral nerve may exert trophic effects on dorsal column nerve fibres.     

The spinal cord-ventral root junction in the Trembler mouse

Summary The Trembler mouse suffers from an hereditary demyelinating neuropathy. Schwann cell myelination of peripheral nerve fibres in the Trembler mouse is abnormal. Myelination of central nerve fibres in the deeper layers of white matter of the spinal cord is normal. At the junction between the peripheral nervous system and the central nervous system in the ventral roots in the Trembler mouse central-type nerve fibres are abnormally thinly myelinated. It is suggested that the normal process of myelination of central nerve fibres in this region is affected by abnormalities of the Schwann cell in the peripheral nervous system.     

Quantitative and qualitative morphological properties of the soleus motor nerve and the L5 ventral root in young and old rats. Relation to the number of soleus muscle fibers

The motor nerve to the soleus muscle and the L5 ventral root from young adult (3-6 months) and old (20-25 months) male Wistar rats were studied with regard to total number of myelinated nerve fibres, calibre spectra of myelinated fibres and morphological properties. The soleus muscle was examined with respect to total number of muscle fibres. A significant decrease in the number of myelinated nerve fibres was found in the old soleus nerves, and was mainly confined to the large-diameter fibers. Similarly, there was a significant decrease in the number of large myelinated fibres in the L5 ventral roots of old animals. Morphological changes in old nerves and spinal roots consisted of axonal degeneration with areas devoid of myelinated nerve fibres, and also myelin sheath irregularities, including myelin splitting with myelin balloon formation, infolded myelin loops and myelin reduplication. The axonal degeneration was more pronounced in the peripheral nerves than in spinal roots. In conformity with other studies, the soleus muscle showed an age-related decrease in the number of muscle fibres. These findings indicate that the decrease in fibre number in old soleus muscle is associated with degenerative neuronal changes and loss of alpha-motoneurons.     

Functional connections are established in the deafferented rat spinal cord by peripherally transplanted human embryonic sensory neurons

Functionally useful repair of the mature spinal cord following injury requires axon growth and the re-establishment of specific synaptic connections. We have shown previously that axons from peripherally grafted human embryonic dorsal root ganglion cells grow for long distances in adult host rat dorsal roots, traverse the interface between the peripheral and central nervous system, and enter the spinal cord to arborize in the dorsal horn. Here we show that these transplants mediate synaptic activity in the host spinal cord. Dorsal root ganglia from human embryonic donors were transplanted in place of native adult rat ganglia. Two to three months after transplantation the recipient rats were examined anatomically and physiologically. Human fibres labelled with a human-specific axon marker were distributed in superficial as well as deep laminae of the recipient rat spinal cord. About 36% of the grafted neurons were double labelled following injections of the fluorescent tracers MiniRuby into the sciatic and Fluoro-Gold into the lower lumbar spinal cord, indicating that some of the grafted neurons had grown processes into the spinal cord as well as towards the denervated peripheral targets. Electrophysiological recordings demonstrated that the transplanted human dorsal roots conducted impulses that evoked postsynaptic activity in dorsal horn neurons and polysynaptic reflexes in ipsilateral ventral roots. The time course of the synaptic activation indicated that the human fibres were non-myelinated or thinly myelinated. Our findings show that growing human sensory nerve fibres which enter the adult deafferentated rat spinal cord become anatomically and physiologically integrated into functional spinal circuits.     

Astrocytic proteins in the dorsal and ventral roots in amyotrophic lateral sclerosis and Werdnig-Hoffmann disease

Abnormalities were detected by two-dimensional gel electrophoresis in the protein composition of both the dorsal and ventral roots of three of six patients who succumbed to amyotrophic lateral sclerosis (ALS). The abnormalities consisted of a cascade of acidic protein spots on silver-stained gels which were shown by immunoblotting to react with an antiserum to human glial fibrillary acidic protein (GFAP). They were found distal to the normal central nervous system/peripheral nervous system (CNS/PNS) transition zone and were undetected in cervical and lumbar root segments taken at the same distances from the spinal cord of eight control patients. Similar changes were observed in the dorsal and ventral roots of one patient with Werdnig-Hoffmann disease (WHD), while a second patient with WHD had the changes in only the ventral roots. The abnormalities probably reflect the presence of radicular glial bundles, which are pathological extensions of glial cells into the spinal roots, indicating that subclinical changes occurred in the sensory nerves of the affected ALS and WHD patients. While no other qualitative abnormalities were noted on gels of ALS and WHD spinal roots, some quantitative changes may be present.     

The Microtubular Pattern Changes at the Spinal Cord-Root Junction and Reverts at the Root-Peripheral Nerve Junction in Sensory and Motor Fibres of the Rat

In the rat, we studied the microtubular content of central nervous system (CNS) axons (pyramidal tract, dorsal funiculus, and intracord domain of motor axons), of radicular axons (ventral and dorsal roots), and of peripheral axons (sural and lateral gastrocnemius nerves). The microtubular density had an inverse relationship with the size of the axon. Within the CNS, values ranged from over 120 microtubules/microm2 for axons smaller than 0.1 microm2 of the pyramidal tract and dorsal funiculus to 24 for 3-microm motor axons (area, 7 microm2) in their spinal cord domain. Peripheral nerve and CNS axons of the same size had comparable microtubular densities. In contrast, the microtubular density of dorsal and ventral root axons was one half that of CNS or peripheral nerve axons of equal calibre. Considered along the axon, the microtubular density of motor and sensory fibres is high in the CNS domain, low in the root, and high again in the peripheral nerve domain. These observations are inconsistent with the notion that the cytoskeleton moves coherently away from the perikaryon. We conclude that the axonal microtubular content accords with the calibre of the fibre and with the anatomical region where it courses. We propose that axonal microtubules are regulated by local cues.     

Schwann cell multiplication deficit in nerve roots of newborn dystrophic mice: A radioautographic and ultrastructural study

Neonatal Schwann cell development was studied in mice with genetic muscular dystrophy (dy^2J/dy^2J) to investigate the pathogenesis of the bare axonal segments which characterize certain spinal roots and peripheral nerves in these animals. From the day of birth to 3 weeks of age, dystrophic and control animals were injected with tritiated thymidine 1 hr prior to sacrifice. Cross-sections of their L4 ventral roots and sciatic nerves were processed for radioautography. Labelled and unlabelled Schwann cell nuclei, as well as numbers of myelinated fibres, were counted by phase microscopy and the same nerves examined by electron microscopy.On the day of birth, groups of large naked axons were present in the roots of dystrophic animals while in control roots most axons were isolated by Schwann cells or their processes. The number of myelinated fibres increased rapidly between days 1 and 9 in control roots but failed to increase in the dystrophic roots. On day 2, Schwann cell labelling indices were significantly lower in dystrophic roots than controls but were similar in dystrophic and control sciatic nerves. Many Schwann cells in the dystrophic roots did not encircle axons.It is concluded that the Schwann cell deficit in dystrophic mice is a developmental abnormality present at birth and associated with a neonatal impairment of Schwann cell multiplication. The presence of this unique abnormality of Schwann cell proliferation suggests an impairment of the mechanisms involved in the control of axon and Schwann cell populations during development.     

Basic fibroblast growth factor immunoreactivity in the peripheral motor system of the rat

We have used immunohistochemistry and electron microscopy to investigate the distribution of basic fibroblast growth factor (bFGF) in the peripheral motor system of the adult rat. In the lumbar segments of the spinal cord, bFGF immunoreactivity (bFGF-I) was seen in motor neurons and glial cells but not in axons. The neuronal immunostaining was seen as two or three intensely fluorescent spots in the nuclei with weak and more diffuse staining of the perinuclear cytoplasm. In the sciatic nerve, bFGF-I was seen in Schwann cells with strong intensity at the nodes of Ranvier. Axonal immunostaining could not be detected. At the electron microscopic level, the intense nodal immunostaining of Schwann cells was confirmed and was found to be localized to the Schwann cell membrane at the nodal gap. The intensity of staining decreased with distance from the node. In the soleus and gastrocnemius muscles, bFGF-I was seen at the motor endplates in sites corresponding to the motor nerve terminals in addition to faint staining within the muscle fibers. Electron microscopy showed that bFGF-I was localized within the nerve terminals. Histochemical localization of bFGF in the peripheral motor system is compatible with the functions ascribed for this protein in this system.     

Inflammatory cells in the peripheral nervous system in motor neuron disease

Summary We examined post-mortem material of the peripheral nervous system of 26 cases of motor neuron disease (MND) for the presence of lymphocyte subsets and macrophages. Findings were quantified and compared with those in control nerves. Lymphocytes in chronic and acute axonal degeneration were studied in sural nerve biopsy and animal material. Signs of demyelination were studied in MND and controls with infiltrates of T cells. A few T lymphocytes were scattered diffusely within the fascicles. The numbers did not differ between MND and controls. About half of the T cells was positive for CD45RA, the other half being positive for CD45RO. T cells were negative for CD25, CD54 and major histocompatibility complex (MHC)-class II. There were hardly and B lymphocytes. The numbers of lymphocytes in nerves with and without axonal degeneration did not differ. Increased MHC class II expression was present on denervated Schwann cells and macrophages in MND and in sural nerves with axonal degeneration. Macrophages were increased in number and in size, both in MND and in control material with axonal degeneration. No signs of demyelination were present either in MND or in controls. It is concluded that a T cell-mediated process in peripheral nerves in MND is very unlikely.Supported by a grant from the Dutch Foundation for Research into ALS and Spinal Muscular Atrophy     

Live imaging of amyotrophic lateral sclerosis pathogenesis: Disease onset is characterized by marked induction of GFAP in Schwann cells

Amyotrophic lateral sclerosis (ALS) is a late‐onset neurological disease characterized by progressive loss of motor neurons. At present, the pathological events precipitating disease onset and the exact pattern of disease progression are not fully understood. Recent studies suggest that glial cells, in particular activated astrocytes, can release factors that can directly kill motor neurons. To further investigate the involvement of glial cells (astrocytes and Schwann cells) in the pathogenesis of ALS, we generated ALS‐(GFAP‐luciferase/SOD^G93A) reporter mouse in which upregulation of glial fibrillary acidic protein (GFAP) can be visualized from live animals throughout the different stages of disease. Our results suggest that the disease in mice is initiated simultaneously in the spinal cord and in the peripheral nerves and is characterized by several cycles of GFAP upregulation. Immunohistochemical analysis confirmed that the induction GFAP bioluminescence signals were associated with the significant increases in GFAP immunoreactivity. The first pathological GFAP signals occurring at 25–30 days were asymptomatic and detectable at the level of lumbar spinal cord projections and at the periphery. These early events were then followed by GFAP promoter inductions that were associated with the distinct clinical symptoms. As expected, the onset of paralysis (112 days) was associated with the gradual and marked GFAP upregulation in the spinal cord. Interestingly, however, the disease onset (90 days) was characterized by sharp and synchronized induction of GFAP in peripheral nerve Schwann cells suggesting that peripheral nerves pathology/denervation and associated Schwann cell stress may play an important role in the ALS pathogenesis. © 2008 Wiley‐Liss, Inc.