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W Tetzlaff

Publications and source records attributed to W Tetzlaff.

At least 19 recordsLinked to original sources
PubMed2006

Class A plexin expression in axotomized rubrospinal and facial motoneurons.

The semaphorin family of guidance molecules plays a role in many aspects of neural development, and more recently semaphorins have been implicated to contribute to the failure of injured CNS neurons to regenerate. While semaphorin expression patterns after neural injury are partially understood, little is known about the expression of their signal transducing transmembrane receptors, the plexins. Therefore, in this study, we compared the expression patterns of all class A plexins (Plxn-A1, A2, A3, A4) in mouse CNS (rubrospinal) and peripheral nervous system (PNS)-projecting (facial) motoneurons for up to two weeks following axonal injury. Using in situ hybridization, immunohistochemistry, and Western blot analysis, in rubrospinal neurons, Plxn-A1 mRNA and protein and Plxn-A4 expression did not change as a result of injury while Plxn-A2 mRNA increased and Plxn-A3 mRNA was undetectable. In facial motoneurons, Plxn-A1, -A3 and -A4 mRNA expression increased, Plxn-A2 mRNA decreased while Plxn-A1 protein expression did not change following injury. We demonstrate that with the exception of the absence of Plxn-A3 mRNA in rubrospinal neurons, both injured rubrospinal (CNS) and facial (PNS) neurons maintain expression of all plexin A family members tested. Hence, there are distinct expression patterns of the individual plexin-A family members suggesting that regenerating rubrospinal and facial motoneurons have a differential ability to transduce semaphorin signals.

Animals↗
PubMed2006

Als2-deficient mice exhibit disturbances in endosome trafficking associated with motor behavioral abnormalities.

ALS2 is an autosomal recessive form of spastic paraparesis (motor neuron disease) with juvenile onset and slow progression caused by loss of function of alsin, an activator of Rac1 and Rab5 small GTPases. To establish an animal model of ALS2 and derive insights into the pathogenesis of this illness, we have generated alsin-null mice. Cytosol from brains of Als2(-/-) mice shows marked diminution of Rab5-dependent endosome fusion activity. Furthermore, primary neurons from Als2(-/-) mice show a disturbance in endosomal transport of insulin-like growth factor 1 (IGF1) and BDNF receptors, whereas neuronal viability and endocytosis of transferrin and dextran seem unaltered. There is a significant decrease in the size of cortical motor neurons, and Als2(-/-) mice are mildly hypoactive. Altered trophic receptor trafficking in neurons of Als2(-/-) mice may underlie the histopathological and behavioral changes observed and the pathogenesis of ALS2.

Animals↗
PubMed2006

BDNF promotes connections of corticospinal neurons onto spared descending interneurons in spinal cord injured rats.

Although regeneration of injured axons is inhibited within the adult CNS, moderate recovery can be found in patients and animals with incomplete spinal cord injury (SCI). This can be partly attributed to sprouting of spared and injured axons, rostral and caudal to the lesion, respectively. Recently, it has been reported that following a thoracic SCI such sprouting can result in indirect reconnections of the lesioned axons to caudal targets via propriospinal interneurons (PrI). Here, we attempted to further promote this spontaneous repair mechanism by applying the neurotrophic factor BDNF (brain-derived neurotrophic factor), in the vicinity of the cell bodies of lesioned corticospinal neurons or NT-3, intrathecally to the cervical spinal cord. We performed a dorsal over-hemisection at the thoracic spinal cord sparing only the left ventrolateral quadrant. This type of lesion did not promote sprouting of injured corticospinal axons or re-routing via commissural PrI. Also, in rats that received NT-3 at the cervical enlargement, no increase in sprouting was found. However, animals receiving BDNF at the cell bodies of lesioned corticospinal neurons showed a significant increase in collateral sprouting and in the number of contacts with PrI. This was not observed when BDNF was administered to unlesioned animals. Although no statistical difference in the horizontal ladder walking was found between the groups, the increase in collateral sprouting and in the number of contacts correlated with the functional recovery. Hence, cell body treatment can promote plasticity of the injured CNS and may be a valuable treatment approach in conjunction with local regeneration promoting strategies.

Animals↗
PubMed2005

Regulation of neuronal and glial galectin-1 expression by peripheral and central axotomy of rat primary afferent neurons.

Galectin-1 (Gal1) is an endogenously-expressed protein important for the embryonic development of the full complement of primary sensory neurons and their synaptic connections in the spinal cord. Gal1 also promotes axonal regeneration following peripheral nerve injury, but the regulation of Gal1 by axotomy in primary afferent neurons has not yet been examined. Here, we show by immunohistochemistry and in situ hybridization that Gal1 expression is differentially regulated by peripheral nerve injury and by dorsal rhizotomy. Following peripheral nerve injury, the proportion of Gal1-positive DRG neurons was increased. An increase in the proportion of large-diameter DRG neurons immunopositive for Gal1 was paralleled by an increase in the depth of immunoreactivity in the dorsal horn, where Gal1-positive terminals are normally restricted to laminae I and II. Dorsal rhizotomy did not affect the proportions of neurons containing Gal1 mRNA or protein, but did deplete the ipsilateral dorsal horn of Gal1 immunoreactivity, indicating that it is transported centrally by dorsal root axons. Dorsal rhizotomy also resulted in an increase in Gal1 mRNA the nerve peripheral to the PNS-CNS interface (likely within Schwann cells and/or macrophages), and to a lesser extent within deafferented spinal cord regions undergoing Wallerian degeneration. This latter increase was notable in the dorsal columns and along the prior trajectories of myelinated afferents into the deeper dorsal horn. These results show that neuronal and glial expressions of Gal1 are tightly correlated with regenerative success. Thus, the differential expression pattern of Gal1 following peripheral axotomy and dorsal rhizotomy suggests that endogenous Gal1 may be a factor important to the regenerative response of injured axons.

Analysis of Variance↗
PubMed2005

Prolonged local neurotrophin-3 infusion reduces ipsilateral collateral sprouting of spared corticospinal axons in adult rats.

The corticospinal tract is widely used to study regeneration and is essential for voluntary movements in humans. In young rats, corticospinal axons on the uninjured side sprout and grow into the denervated side. Neurotrophin-3 (NT-3) induces such crossed collateral sprouting in adults. We investigated whether local intraspinal NT-3 infusions would promote collateral sprouting of spared corticospinal terminals from within a partially denervated side, as this would be more appropriate for enhancing function of unilateral and specific movements. Adult rats received a partial bilateral transection of the pyramids, leaving approximately 40% of each tract intact. Vehicle or vehicle plus NT-3 (3 or 10 microg/day) was infused for 14 days into the left side of the cervical (C5/6) or lumbar (L2) cord. The corticospinal processes on the left side were anterogradely traced with cholera toxin B (CTB; which labeled gray matter processes more robustly than biotinylated dextran amine) injected into the front or hind limb area of the right sensorimotor cortex, respectively, 3 days before analysis. Unexpectedly, approximately 40% fewer CTB-labeled corticospinal processes were detectable in the cervical or lumbar gray matter of NT-3-treated rats than in vehicle-infused ones. Vehicle-infused injured rats had more corticospinal processes in the center of the cord than normal rats, evidence for lesion-induced collateral sprouting. NT-3 caused sprouting of local calcitonin gene-related peptide-positive fibers. These results suggest that NT-3 reduces collateral sprouting of spared corticospinal axons from within the denervated regions, possibly because of the injury environment or by increasing sprouting of local afferents. They identify an unexpected context-dependent outgrowth inhibitory effect of NT-3.

Animals↗
PubMed2005

Expression and functions of galectin-1 in sensory and motoneurons.

Galectin-1 (Gal1) was the first identified member of the galectin family of beta-galactosidase-binding proteins. Gal1 has important roles in processes fundamental to growth and survival of an organism, including cell adhesion, cell proliferation and apoptosis, and is expressed in many tissues, including the nervous system. In the 1980s, research focused on the developmental regulation of Gal1 expression during neurogenesis. Gal1 was found to be expressed mainly in peripherally-projecting neurons beginning early in neurogenesis, and its expression is maintained at high levels in subpopulations of these neurons in the adult rodent. Although the expression pattern of Gal1 implied that it may be involved in axonal guidance or targeting of subsets of sensory and motoneurons, possible roles of Gal1 in the nervous system had not been confirmed until recently. Gal1 has since been shown to be required for the proper guidance of subsets of primary olfactory axons (to targets in the olfactory bulb) and of primary somatosensory axons (to targets in the superficial dorsal horn). In addition, Gal1 has been implicated in the regenerative response of axons following peripheral nerve injury. Gal1 has been shown to promote axonal regeneration through the activation of macrophages. Also, Gal1 may act within the injured neuron to enhance regrowth: the injury-induced regulation of Gal1 in numerous types of peripherally- and centrally-projecting neurons correlates positively with the regenerative potential of their axons. In this review, we discuss the expression pattern of Gal1 in sensory and motoneurons, and the potential roles of Gal1 in development, axonal regeneration and neuropathic pain.

Animals↗
PubMed2004

Altered primary afferent anatomy and reduced thermal sensitivity in mice lacking galectin-1.

The transmission of nociceptive information occurs along non-myelinated, or thinly myelinated, primary afferent axons. These axons are generally classified as peptidergic (CGRP-expressing) or non-peptidergic (IB4-binding), although there is a sub-population that is both CGRP-positive and IB4-binding. During neuronal development and following injury, trophic factors and their respective receptors regulate their survival and repair. Recent reports also show that the carbohydrate-binding protein galectin-1 (Gal1), which is expressed by nociceptive primary afferent neurons during development and into adulthood, is involved in axonal pathfinding and regeneration. Here we characterize anatomical differences in dorsal root ganglia (DRG) of Gal1 homozygous null mutant mice (Gal1(-/-)), as well as behavioural differences in tests of nociception. Gal1(-/-) mice have a significantly reduced proportion of IB4-binding DRG neurons, an increased proportion of NF200-immunoreactive DRG neurons, increased depth of central terminals of IB4-binding and CGRP-immunoreactive axons in the dorsal horn, and a reduced number of Fos-positive second order neurons following thermal (cold or hot) stimulation. While there is no difference in the total number of axons in the dorsal root of Gal1(-/-) mice, there are an increased number of myelinated axons, suggesting that in the absence of Gal1, neurons that are normally destined to become IB4-binding instead become NF200-expressing. In addition, mice lacking Gal1 have a decreased sensitivity to noxious thermal stimuli. We conclude that Gal1 is involved in nociceptive neuronal development and that the lack of this protein results in anatomical and functional deficits in adulthood.

Afferent Pathways↗
PubMed2004

Galectin-1 expression correlates with the regenerative potential of rubrospinal and spinal motoneurons.

Axotomized spinal motoneurons are able to regenerate to their peripheral targets, whereas injured rubrospinal neurons that lie completely within the CNS fail to regenerate. The differing cell body reactions to axotomy of these two neuronal populations have been implicated in their disparate regenerative ability. Recently, the lectin galectin-1 has been shown to be involved in both spinal motoneurons and primary afferent regeneration. Using in situ hybridization, we compared the endogenous galectin-1 mRNA expression in spinal motoneurons and rubrospinal neurons after axotomy. We found that 7 and 14 days after axotomy, galectin-1 mRNA increased in spinal motoneurons but decreased in rubrospinal neurons. Infusion of the brain-derived neurotrophic factor into the vicinity of the injured rubrospinal nucleus, which we have previously shown to increase the regenerative capacity of rubrospinal neurons, significantly increased galectin-1 mRNA compared with uninjured control levels. Thus, the expression of galectin-1 in neurons correlates with the regenerative propensity.

Analysis of Variance↗
PubMed2004

Galectin-1 in regenerating motoneurons.

The exogenous application of recombinant galectin-1 has recently been shown to promote the rate of peripheral nerve regeneration. Endogenous neuronal galectin-1 expression has recently been demonstrated to increase after axotomy. Here we demonstrate a significant increase in the endogenous neuronal expression of galectin-1 mRNA in facial motoneurons after either a nerve resection or crush injury in mice. This increase in galectin-1 expression was due in part to the loss of target-derived factor(s) as indicated by both the return of galectin-1 expression to control levels following target re-innervation and the increase in galectin-1 expression after blockade of axonal transport by an interneuronal colchicine injection. Furthermore, interneuronal injections of glial-derived neurotrophic factor into the uninjured nerve also increased galectin-1 mRNA expression within facial motoneurons suggesting that positive signals may also be involved in the regulation of galectin-1 expression. Galectin-1 null mutant mice showed an attenuated rate of functional recovery of whisking movement after a facial nerve crush.

Animals↗
PubMed2003

Endogenous expression of inhibitor of apoptosis proteins in facial motoneurons of neonatal and adult rats following axotomy.

The inhibitor of apoptosis protein family members inhibit cell death resulting from a variety of apoptotic stimuli. However, the endogenous expression of neuronal inhibitor of apoptosis proteins following axonal injury has not been thoroughly examined. Neonatal facial motoneurons are highly susceptible to axotomy-induced apoptosis, whereas adult facial motoneurons survive axotomy. We hypothesized that the endogenous expression of inhibitor of apoptosis proteins may be involved in the differential susceptibility of adult and neonatal facial motoneurons to axonal injury. In this study, we examined the expression of two endogenous inhibitor of apoptosis proteins, neuronal apoptosis inhibitory protein and x-linked inhibitory apoptosis protein, in adult and neonatal rat facial motoneurons following axotomy. Analyses using reverse-transcription polymerase chain reaction and in situ hybridization indicated that neuronal apoptosis inhibitory protein mRNA was increased in neonatal facial nuclei 24 h post axotomy. In the adult, neuronal apoptosis inhibitory protein mRNA expression increased at 1, 3, 7 and 14 days post axotomy, while little change in the expression of X-linked inhibitory apoptosis protein mRNA was detected at any age or time point time point analyzed. Interestingly, immunohistochemistry using antibodies for neuronal apoptosis inhibitory protein and X-linked inhibitory apoptosis protein, revealed the level of these proteins was higher in the neonatal motoneurons when compared with the adult. Furthermore, immunohistochemistry and western blot for neuronal apoptosis inhibitory protein revealed, in contrast to the observed increase in neuronal apoptosis inhibitory protein mRNA, a decline in the expression of neuronal apoptosis inhibitory protein following axotomy in the adult, whereas no change in neuronal apoptosis inhibitory protein was detected in neonatal facial motoneurons. X-linked inhibitory apoptosis protein, as analyzed by immunohistochemistry and western blot, remained unchanged by axotomy in neonatal motoneurons and adult motoneurons. These results indicate differential expression and/or turnover of inhibitor of apoptosis proteins in neonatal versus adult facial motoneurons, and suggest the level of inhibitor of apoptosis protein expression alone is not an indicator of cell fate following axotomy.

Animals↗
PubMed2003

In vivo application of mitochondrial pore inhibitors blocks the induction of apoptosis in axotomized neonatal facial motoneurons.

Axotomy induces apoptosis in motoneurons of neonatal rodents. To identify the key players in motoneuron apoptosis, we assessed the progression of apoptosis at 4 h intervals following facial motoneuron axotomy. The mitochondrial release of cytochrome c, caspase-3 activation and nuclear condensation were first observed in the motoneuron cell bodies 16 h postaxotomy. In vivo application of inhibitors of the mitochondrial permeability transition pore, Bongkrekic acid and cyclosporin A prevented cytochrome c release as well as caspase-3 activation and attenuated motoneuron apoptosis. Similarly, in vivo application of RU360, an inhibitor of the mitochondrial calcium uniporter, also protected axotomized motoneurons from apoptosis. Taken together, our results show that cytochrome c release and subsequent caspase-3 activation are critical events that precipitate the apoptotic death of axotomized neonatal motoneurons in vivo. In addition, these results provide evidence that application of mitochondrial pore inhibitors in vivo can block the induction of apoptosis following motoneuron axotomy.

Animals↗
PubMed2002

Brain-derived neurotrophic factor applied to the motor cortex promotes sprouting of corticospinal fibers but not regeneration into a peripheral nerve transplant.

Previous experiments from our laboratory have shown that application of brain-derived neurotrophic factor (BDNF) to the red nucleus or the motor cortex stimulates an increase in the expression of regeneration-associated genes in rubrospinal and corticospinal neurons. Furthermore, we have previously shown that BDNF application stimulates regeneration of rubrospinal axons into a peripheral graft after a thoracic injury. The current study investigates whether application of BDNF to the motor cortex will facilitate regeneration of corticospinal neurons into a peripheral nerve graft placed into the thoracic spinal cord. In adult Sprague Dawley rats, the dorsal columns and the corticospinal tract between T9 and T10 were ablated by suction, and a 5-mm-long segment of predegenerated tibial nerve was autograft implanted into the lesion. With an osmotic pump, BDNF was infused directly into the parenchyma of the motor cortex for 14 days. Growth of the corticospinal tract into the nerve graft was then evaluated by transport of an anterograde tracer. Anterogradely labeled corticospinal fibers were not observed in the peripheral nerve graft in animals treated with saline or BDNF. Serotinergic and noradrenergic fibers, as well as peripheral sensory afferents, were observed to penetrate the graft, indicating the viability of the peripheral nerve graft as a permissive growth substrate for these specific fiber types. Although treatment of the corticospinal fibers with BDNF failed to produce regeneration into the graft, there was a distinct increase in the number of axonal sprouts rostral to the injury site. This indicates that treatment of corticospinal neurons with neurotrophins, e.g., BDNF, can be used to enhance sprouting of corticospinal axons within the spinal cord. Whether such sprouting leads to functional recovery after spinal cord injury is currently under investigation.

Animals↗
PubMed2001

Spinal cord regeneration: from gene to transplants.

The past 20 years has seen the emergence of many exciting and promising experimental therapeutic strategies to promote regeneration of the injured spinal cord in laboratory animals. A greater understanding of the pathophysiologic mechanisms that contribute to the initial and secondary cord injury may facilitate the development of neuroprotective strategies that preserve axonal function and prevent apoptotic cell death, thus optimizing neurologic function. Neurotrophic factors have been used to augment the poor intrinsic regenerative capacity of central nervous system neurons, and the need for sophisticated delivery of such trophic agents has stimulated the application of gene therapy in this context. In addition to augmenting the neuronal capacity to regenerate axons, many researchers are developing strategies to overcome the inhibitory environment into which these axons must grow. Characterizing the inhibitory elements of the glial scar at the site of injury and of myelin in the distal tracts is therefore a focus of intense scientific interest. To this effect, a number of strategies have also been developed to bridge the injury site and facilitate axonal growth across the lesion with a variety of cellular substrates. These include fetal tissue transplants, stem cells, Schwann cells, and olfactory ensheathing cells. With the collaboration of basic scientists and clinicians, it is hoped that these experimental strategies coupled with a greater understanding of the neurobiology of spinal cord injury will be translatable to the clinical setting in the near future.

Animals↗
PubMed2000

Model for focal demyelination of the spinal dorsal columns of transgenic MBP-LacZ mice by phototargeted ablation of oligodendrocytes.

Focal demyelination models provide powerful tools to study demyelination and remyelination in the central nervous system. In this report, we present a novel technique, which selectively targets oligodendrocytes within the spinal cord of transgenic mice to produce focal demyelination. Transgenic mice expressing the E. coli LacZ (beta-galactosidase) gene from the myelin basic protein promotor allowed for oligodendrocyte-specific cleavage of topically applied fluorescein-di-beta-galactopyranoside liberating photoactivatable fluorescein. Subsequent fluorescence illumination generated oxygen radicals that oxidized a second exogenous substrate, 3-amino-9-ethyl carbazole, to form a toxic precipitate within oligodendrocytes. Histochemical staining of the spinal cord dorsal columns 8 days following phototargeting revealed that the treated region no longer contained beta-galactosidase-positive cells. Focal demyelination of the dorsal columns was observed to a depth of 150 microm in transverse semithin plastic sections. Numerous bundles of naked axons interspersed with myelin, debris-laden macrophages, and reactive astrocytes were evident by electron microscopy. Remyelination of axons by both oligodendrocytes and invading Schwann cells was observed within the treated region 14 days after phototargeting. Newly generated oligodendrocytes were identified within the demyelinated region by their incorporation of bromodeoxyuridine. Thus, this novel focal demyelination protocol provides: (1) a method for selective targeted ablation of oligodendrocytes in vivo, (2) control over the extent of the demyelinated region, with (3) an environment that maintains its remyelination capacity. Phototargeted ablation of oligodendrocytes may therefore be a useful model for studying axon-glia interactions, axon regeneration within a demyelinated zone, and remyelination of axons.

Animals↗
PubMed2000

Immunological myelin disruption does not alter expression of regeneration-associated genes in intact or axotomized rubrospinal neurons.

The inability of axotomized neurons to regenerate within the CNS has been partially attributed to a number of inhibitory factors associated with CNS myelin that are extrinsic to the severed neurons. However, some neurons are capable of limited regeneration after injury and this ability has been shown to correlate with the expression of certain regeneration-associated genes (RAGs) intrinsic to injured neurons. It has therefore been postulated that neutralization of inhibitory factors, as well as the induction of an appropriate neuronal cell body response, would facilitate improved regrowth of injured CNS axons. In previous studies we have shown that immunological removal of myelin from the spinal cord facilitates axonal regeneration by rubrospinal neurons, as indicated by retrograde transport of a fluorescent dye placed distal to the site of injury. Here, we investigated whether the immunological focal removal of spinal cord myelin, following a thoracic spinal cord injury, concomitantly stimulated an increase in the expression of RAGs in rubrospinal neurons. In situ hybridization for Talpha-1 tubulin and GAP-43 at days 7, 14, and 21 revealed no significant increase in gene expression in rubrospinal neurons following immunological demyelination. The ability of various neuronal populations to sprout or slowly regrow without expressing the previously characterized cell body response is reviewed. We conclude that the recently demonstrated regeneration of rubrospinal tract, after immunologically directed spinal cord demyelination, is the result of either axonal sprouting or slow axonal regrowth without the increased expression of RAGs characteristic for fast axon regeneration.

Animals↗
PubMed2000

Fibroblast growth factor treatment produces differential effects on survival and neurite outgrowth from identified bulbospinal neurons in vitro.

The in vivo application of appropriate trophic factors may enhance regeneration of bulbospinal projections after spinal cord injury. Currently, little is known about the sensitivities of specific bulbospinal neuron populations to the many identified trophic factors. We devised novel in vitro assays to study trophic effects on the survival and neurite outgrowth of identified bulbospinal neurons. Carbocyanine dye crystals implanted into the cervical spinal cord of embryonic day (E)5 chick embryos retrogradely labeled developing bulbospinal neurons. On E8, dissociated cultures containing labeled bulbospinal neurons were prepared. Fibroblast growth factor (FGF)-2 (but not FGF-1) promoted the survival of bulbospinal neurons. FGF receptor expression was widespread in the E8 brainstem, but not detected in young bulbospinal neurons, suggesting that nonneuronal cells mediated the FGF-stimulated survival response. Astrocytes synthesize a variety of trophic factors, and astrocyte-conditioned medium (ACM) also promoted the survival of bulbospinal neurons. As might be expected, FGF-2 function blocking antibodies did not suppress ACM-promoted survival, nor did an ELISA detect FGF-2 in ACM. This suggests that nonneuronal cells synthesize other factors in response to exogenous FGF-2 which promote the survival of bulbospinal neurons. Focusing on vestibulospinal neurons, dissociated (survival assay) or explant (neurite outgrowth assay) cultures were prepared. FGF-2 promoted both survival and neurite outgrowth of identified vestibulospinal neurons. Interestingly, FGF-1 promoted neurite outgrowth but not survival; the converse was true of FGF-9. Thus, differential effects of specific growth factors on survival or neurite outgrowth of bulbospinal neurons were distinguished.

Animals↗