Armin Buss

Identification of regeneration-associated genes after central and peripheral nerve injury in the adult rat

BackgroundIt is well known that neurons of the peripheral nervous system have the capacity to regenerate a severed axon leading to functional recovery, whereas neurons of the central nervous system do not regenerate successfully after injury. The underlying molecular programs initiated by axotomized peripheral and central nervous system neurons are not yet fully understood.ResultsTo gain insight into the molecular mechanisms underlying the process of regeneration in the nervous system, differential display polymerase chain reaction has been used to identify differentially expressed genes following axotomy of peripheral and central nerve fibers. For this purpose, axotomy induced changes of regenerating facial nucleus neurons, and non-regenerating red nucleus and Clarkes nucleus neurons have been analyzed in an intra-animal side-to-side comparison. One hundred and thirty five gene fragments have been isolated, of which 69 correspond to known genes encoding for a number of different functional classes of proteins such as transcription factors, signaling molecules, homeobox-genes, receptors and proteins involved in metabolism. Sixty gene fragments correspond to genomic mouse sequences without known function. In situ-hybridization has been used to confirm differential expression and to analyze the cellular localization of these gene fragments. Twenty one genes (~15%) have been demonstrated to be differentially expressed.ConclusionsThe detailed analysis of differentially expressed genes in different lesion paradigms provides new insights into the molecular mechanisms underlying the process of regeneration and may lead to the identification of genes which play key roles in functional repair of central nervous tissues.

Major histocompatibility complex class II expression by activated microglia caudal to lesions of descending tracts in the human spinal cord is not associated with a T cell response.

Abstract Lesion-induced microglial/macrophage responses were investigated in post-mortem human spinal cord tissue of 20 patients who had died at a range of survival times after spinal trauma or brain infarction. Caudal to the spinal cord injury or brain infarction, a strong increase in the number of activated microglial cells was observed within the denervated intermediate grey matter and ventral horn of patients who died shortly after the insult (4–14 days). These cells were positive for the leucocyte common antigen (LCA) and for the major histocompatibility complex class II antigen (MHC II), with only a small proportion staining for the CD68 antigen. After longer survival times (1–4 months), MHC II-immunoreactivity (MHC II-IR) was clearly reduced in the grey matter but abundant in the white matter, specifically within the degenerating corticospinal tract, co-localising with CD68. In this fibre tract, elevated MHC II-IR and CD68-IR were still detectable 1 year after trauma or stroke. It is likely that the subsequent expression of CD68 on MHC II-positive microglia reflects the conversion to a macrophage phenotype, when cells are phagocytosing degenerating presynaptic terminals in grey matter target regions at early survival times and removing axonal and myelin debris in descending tracts at later survival times. No T or B cell invasion or involvement of co-stimulatory B7 molecules (CD80 and CD86) was observed. It is possible that the up-regulation of MHC II on microglia that lack the expression of B7 molecules may be responsible for the prevention of a T cell response, thus protecting the spinal cord from secondary tissue damage.

Expression pattern of NOGO-A protein in the human nervous system

The distribution pattern of NOGO-A protein, an important axon growth inhibitory molecule and member of the reticulon family, has been investigated in the adult human brain, spinal cord, retina and dorsal root ganglia. Intense NOGO-A immunoreactivity was detected in oligodendroglial cell bodies and their myelin sheaths in nerve fibre tracts of the central nervous system. Furthermore, numerous populations of neurons in the brain and spinal cord expressed NOGO-A to a variable extent in their cell bodies and neurites, suggesting additional, as-yet-unknown, functions of this protein.

Substantial early, but nonprogressive neuronal loss in multiple sclerosis (ms) spinal cord†

Research in multiple sclerosis (MS) has recently been focusing on the extent of neuroaxonal damage and its contribution to disease outcome. In the present study, we examined spinal cord tissue from 30 clinically well‐characterized MS patients. MS, amyotrophic lateral sclerosis (ALS), and control spinal cord tissue were subjected to morphometric analysis and immunohistochemistry for markers of cell damage and regeneration. Data were related to disease duration and age at death. Here, we present evidence for substantial, nonprogressive neuronal loss on the cervical and lumbar levels early in the disease course of MS. Chromatolytic neurons and immunoreactivity for c‐Jun and GAP43 were observed in the ventral gray matter in and adjacent to actively demyelinating lesions, pointing toward neuronal damage and regeneration as an early response to lesion formation. Ann Neurol 2009;66:698–704

Functional polymorphisms in matrix metalloproteinases -1, -3, -9 and -12 in relation to cervical artery dissection

BackgroundCervical artery dissection is a leading cause of cerebral ischemia in young adults. Morphological investigations have shown alterations in the extracellular matrix (ECM) of affected vessel walls. As matrix metalloproteinases (MMP) play a central role in the regulation of the ECM, an increased expression of these enzymes might lead to the endothelial damage in spontaneous cervical artery dissection (sCAD). Five different DNA polymorphisms in MMP-1, -3, -9 and -12 were tested for their frequency in patients with sCAD and compared with those of a control population.MethodsBlood was sampled from 70 unrelated patients presenting consecutively in the department of neurology of the Aachen University Medical School with sCAD and from 87 control subjects living in the same area as the patients. The MMP polymorphisms were analyzed with hybridization probes using the LightCycler™ (Roche Diagnostics), by sequencing using the ABI 310 Genetic Analyzer (Applied Biosystems) and with the GeneScan program on a ABI 310 Genetic Analyzer.ResultsNo statistically significant differences in the allelic distribution were found between sCAD patients and the controls.ConclusionAlleles of these 5 functional polymorphisms of MMPs seem not to be associated with structural alterations in the blood vessel wall of sCAD patients. However, this does not exclude a pathogenetic role for MMPs in sCAD via secondary factors such as cytokines that are able to induce these enzymes in cervical blood vessel walls.

Regulation of stearoyl-CoA desaturase-1 after central and peripheral nerve lesions.

BackgroundInterruption of mature axons activates a cascade of events in neuronal cell bodies which leads to various outcomes from functional regeneration in the PNS to the failure of any significant regeneration in the CNS. One factor which seems to play an important role in the molecular programs after axotomy is the stearoyl Coenzyme A-desaturase-1 (SCD-1). This enzyme is needed for the conversion of stearate into oleate. Beside its role in membrane synthesis, oleate could act as a neurotrophic factor, involved in signal transduction pathways via activation of protein kinases C.ResultsIn situ hybridization and immunohistochemistry demonstrated a strong up-regulation of SCD at mRNA and protein level in regenerating neurons of the rat facial nucleus whereas non-regenerating Clarkes and Red nucleus neurons did not show an induction of this gene.ConclusionThis differential expression points to a functionally significant role for the SCD-1 in the process of regeneration.