Biomedical subjects

S P Niclou

Publications and source records attributed to S P Niclou.

6 recordsLinked to original sources

PubMed2002

Viral vector-mediated gene expression in olfactory ensheathing glia implants in the lesioned rat spinal cord.

Implantation of olfactory ensheathing glia (OEG) is a promising strategy to augment long-distance regeneration in the injured spinal cord. In this study, implantation of OEG following unilateral hemisection of the dorsal cervical spinal cord was combined with ex vivo gene transfer techniques. We report, to our knowledge for the first time, that purified cultures of primary OEG are capable of expressing a foreign gene following adenoviral (AdV) and lentiviral (LV) vector-mediated gene transfer. OEG implants subjected to AdV vector-mediated gene transfer expressed high levels of transgenic protein in both intact and lesioned spinal cord at 7 days after implantation. However, the levels of transgene expression gradually declined between 7 and 30 days after implantation in lesioned spinal cord. Infection with LV vectors resulted in stable transduction of primary OEG cultures and transgene expression persisted for at least 4 months after implantation. Genetic engineering of OEG opens the possibility of expressing additional neurotrophic genes and create optimal 'bridging' substrates to support spinal axon regeneration. Furthermore, stable transduction of OEG allows us to reliably study the behaviour of implanted cells and to obtain better understanding of their regeneration supporting properties.

Adenoviridae↗

PubMed2000

Slit2 is a repellent for retinal ganglion cell axons.

We set out to isolate inhibitory guidance cues that affect retinal ganglion cell (RGC) axons in vitro and that could potentially be involved in RGC pathfinding decisions. Here we describe the biochemical purification of an RGC growth cone collapsing factor from bovine brain membranes and its identification as Slit2. Recombinant human Slit2 collapses and repels RGC growth cones from all quadrants of the chick retina. In the developing mouse visual system, slit2 is expressed in the eye, in the optic stalk, and in the ventral diencephalon. Slit2 expression is strong in anterior ventral diencephalic structures but is absent from the ventral midline where the optic chiasm forms. The putative receptors for Slits, robo1 and robo2, are expressed in the inner retinal layer in which RGCs are located. A comparison of the expression patterns of Slit2 and retinal axon trajectories suggests that slit2 acts as a short range repellent for retinal ganglion cell axons.

Animals↗

PubMed1998

Changes in the expression of protease-activated receptor 1 and protease nexin-1 mRNA during rat nervous system development and after nerve lesion.

HDs racI Thrombin causes profound metabolic and morphological changes in cultured neural cells via activation of the thrombin receptor, also called protease-activated receptor 1 (PAR1). PAR1 mRNA is present in the rat brain, but the role of this receptor in the nervous system remains elusive. The expression of PAR1 and the potent thrombin inhibitor protease nexin-1 (PN-1) was investigated in the developing rat brain and spinal cord and after peripheral nerve lesion. As seen by in situ hybridization, the PAR1 mRNA signal in the late embryonic and early postnatal nervous system was widespread, but generally of low intensity whereas in the adult it was more pronounced and confined to particular neuronal cells. These include the mesencephalic dopaminergic neurons, several thalamic and brainstem nuclei, the mitral cells in the olfactory bulb and the Purkinje cells in the cerebellum. In the spinal cord, PAR1 mRNA was abundant in motoneurons and a particularly high expression was detected in the preganglionic neurons of the autonomic nervous system. High PAR1 mRNA expression was also found in the dorsal root ganglia. Interestingly, strong immunoreactivity for the protease inhibitor PN-1 was present in spinal motoneuron cell bodies, although its transcript was undetectable there. In response to sciatic nerve transection, the signal intensity of PAR1 mRNA as seen by Northern analysis increased in the proximal and the distal part of the lesioned nerve and in the denervated muscle, whereas the PN-1 mRNA signal strongly increased only in the distal part of the nerve but remained unchanged in the proximal part and in the muscle. After facial nerve transection, PAR1 mRNA expression substantially decreased in facial motoneurons. No PAR1 transcript was detected in reactive astrocytes. Similar to PAR1, PN-1 mRNA which was expressed in interneurons within the facial nucleus was also decreased following facial nerve transection.

Amyloid beta-Protein Precursor↗

PubMed1996

The thrombin receptor is present in myoblasts and its expression is repressed upon fusion.

Cultured myoblasts derived from limb muscle of newborn rats express thrombin receptor immunoreactivity on their surface. Receptor expression is repressed upon myoblast fusion. This is due at least in part to a decrease in the amount of the thrombin receptor mRNA. Addition of thrombin triggers calcium transients only in mono- but not multinucleated muscle cells. Furthermore, thrombin increases the rate of myoblast proliferation that coincides with an activation of mitogen-activated protein kinase. Northern analysis of thrombin receptor mRNA expression in skeletal muscle showed that the transcript is present at a relatively high level at birth, but is almost undetectable in the adult. By in situ hybridization, the mRNA at birth appeared to be present mostly in mononucleated cells grouped in clusters, but not in muscle fibers. Very few nuclei surrounded by a mRNA signal were present on muscle sections of rats 24 days postnatally. These results suggest that the thrombin receptor plays a role in muscle development.

Amino Acid Sequence↗

PubMed1996

The serine protease granzyme A does not induce platelet aggregation but inhibits responses triggered by thrombin.

Granzyme A is a serine protease stored in cytoplasmic granules of cytotoxic and helper T lymphocytes. This protease seems to elicit thrombin receptor-mediated responses in neural cells, thereby triggering neurite retraction and reversal of astrocyte stellation. Here we report that granzyme A does not cause platelet aggregation even at concentrations that are more than two orders of magnitude higher than the EC50 for granzyme A in causing morphological changes in neural cells. However, granzyme A blocks thrombin-induced platelet aggregation in a dose-dependent manner without affecting the response to either ADP or to the peptide agonist of the thrombin receptor SFLLRN that corresponds in sequence to the tethered ligand domain. The inability of granzyme A to cause aggregation and its inhibition of thrombin-induced aggregation were seen in platelets from man, rat and mouse. Granzyme A does not affect the catalytic activity of thrombin in cleaving a chromogenic substrate or the macromolecular substrate fibrinogen. However, granzyme A does seem to cleave the thrombin receptor on platelets to produce a weak Ca2+ signal and reduce the response to subsequent challenge with thrombin, but does not induce a signal in thrombin-stimulated platelets. It is proposed that granzyme A interacts with the thrombin receptor found on platelets in a manner that is insufficient to cause aggregation, but sufficient to compete with thrombin for the receptor. These results suggest that granzyme A cleaves the thrombin receptor at a rate that is insufficient to cause platelet aggregation but is sufficient to cause morphological changes in neural cells. Furthermore, these observations demonstrate that granzyme A release occurring during immune responses within blood vessels would not directly cause platelet aggregation.

Amino Acid Sequence↗

PubMed1996

The thrombin receptor in the nervous system.

Neurite retraction and reversal of astrocyte stellation triggered by the serine protease thrombin are receptor-mediated events. This article summarizes the current knowledge about the cellular effects that are induced by thrombin and its receptor in neural cells. The data presented show that the thrombin receptor messenger RNA is expressed in cultured astrocytes and that the reversal of stellation caused by thrombin in these cells is prevented by the protein kinase inhibitor staurosporine. Peptides based in sequence on the tethered ligand domain of the thrombin receptor were shown to mimic the effect of thrombin in most systems investigated. Platelets of some species, however, aggregate only in response to thrombin but not to the peptides. This observation is confirmed here. Rodent receptor-activating peptides did not cause aggregation of rat or mouse platelets. In contrast, all peptides triggered reversal of stellation in rat astrocytes and neurite retraction in mouse neuroblastoma cells, supporting the proposed mechanism of cleavage-induced receptor activation in neural cells. Finally, evidence is presented that serum withdrawal causes a decrease in the amount of the thrombin receptor mRNA in different types of neuronal cells. The possible role played by the thrombin receptor in the nervous system is discussed.

Animals↗