Injury-induced gelatinase and thrombin-like activities in regenerating and nonregenerating nervous systems.
It is now widely accepted that injured nerves, like any other injured tissue, need assistance from their extracellular milieu in order to heal. We compared the postinjury activities of thrombin and gelatinases, two types of proteolytic activities known to be critically involved in tissue healing, in nonregenerative (rat optic nerve) and regenerative (fish optic nerve and rat sciatic nerve) neural tissue. Unlike gelatinases, whose induction pattern was comparable in all three nerves, thrombin-like activity differed clearly between regenerating and nonregenerating nervous systems. Postinjury levels of this latter activity seem to dictate whether it will display beneficial or detrimental effects on the capacity of the tissue for repair. The results of this study further highlight the fact that tissue repair and nerve regeneration are closely linked and that substances that are not unique to the nervous system, but participate in wound healing in general, are also crucial for regeneration or its failure in the nervous system. (+info)
Experimental induction of retinal ganglion cell death in adult mice.
PURPOSE: Retinal ganglion cells die by apoptosis during development and after trauma such as axonal damage and exposure to excitotoxins. Apoptosis is associated with changes in the expression of genes that regulate this process. The genes that regulate apoptosis in retinal ganglion cells have not been characterized primarily because previous studies have been limited to animal models in which gene function is not easily manipulated. To overcome this limitation, the rate and mechanism of retinal ganglion cell death in mice was characterized using optic nerve crush and intravitreal injections of the glutamate analog N-methyl-D-aspartate (NMDA). METHODS: To expose retinal ganglion cells (RGCs) to excitotoxins, adult CB6F1 mice were injected intravitreally in one eye with NMDA. In an alternative protocol to physically damage the axons in the optic nerve, the nerve was crushed using self-closing fine forceps. Each animal had one or the other procedure carried out on one eye. Loss of RGCs was monitored as a percentage of cells lost relative to the fellow untreated eye. Thy1 expression was examined using in situ hybridization. DNA fragmentation in dying cells was monitored using terminal transferase-dUTP nick-end labeling (TUNEL). RESULTS: RGCs comprise 67.5% +/- 6.5% (mean +/- SD) of cells in the ganglion cell layer (GCL) of control mice based on nuclear morphology and the presence of mRNA for the ganglion cell marker Thy1. One week after optic nerve crush, these cells started to die, progressing to a maximum loss of 57.8% +/- 8.1% of the cells in the GCL by 3 weeks. Cell loss after NMDA injection was dose dependent, with injections of 10 nanomoles having virtually no effect to a maximum loss of 72.5% +/- 12.1% of the cells in the GCL within 6 days after injection of 160 nanomoles NMDA. Cell death exhibited features of apoptosis after both optic nerve crush and NMDA injection, including the formation of pyknotic nuclei and TUNEL staining. CONCLUSIONS: Quantitative RGC death can be induced in mice using two distinct signaling pathways, making it possible to test the roles of genes in this process using transgenic animals. (+info)
Differential T cell response in central and peripheral nerve injury: connection with immune privilege.
The central nervous system (CNS), unlike the peripheral nervous system (PNS), is an immune-privileged site in which local immune responses are restricted. Whereas immune privilege in the intact CNS has been studied intensively, little is known about its effects after trauma. In this study, we examined the influence of CNS immune privilege on T cell response to central nerve injury. Immunocytochemistry revealed a significantly greater accumulation of endogenous T cells in the injured rat sciatic nerve than in the injured rat optic nerve (representing PNS and CNS white matter trauma, respectively). Use of the in situ terminal deoxytransferase-catalyzed DNA nick end labeling (TUNEL) procedure revealed extensive death of accumulating T cells in injured CNS nerves as well as in CNS nerves of rats with acute experimental autoimmune encephalomyelitis, but not in injured PNS nerves. Although Fas ligand (FasL) protein was expressed in white matter tissue of both systems, it was more pronounced in the CNS. Expression of major histocompatibility complex (MHC) class II antigens was found to be constitutive in the PNS, but in the CNS was induced only after injury. Our findings suggest that the T cell response to central nerve injury is restricted by the reduced expression of MHC class II antigens, the pronounced FasL expression, and the elimination of infiltrating lymphocytes through cell death. (+info)
Bilateral optic nerve injury.
Bilateral optic nerve injury is a rare condition and is reported in 5-6 percent of all optic nerve injuries. However, there is no published series on bilateral optic nerve injury. Analysis of 31 cases of bilateral optic nerve involvement seen amongst 275 patients with optic nerve injury (11.5 percent) is discussed. Road traffic accident which is the most common cause of optic nerve injury, was recorded in 61 percent. Shotgun injury and blast in jury was the cause in 22.5 percent of cases. All the patients except 4 received steroids. Anterior cranial fossa fracture and opacity of paranasal sinuses were recorded in a third of the patients. Visual evoked potentials were recorded in 27 patients. Improvement in vision was noticed in 23 patients (74 percent). However, among the 62 eyes, 39 eyes showed improvement (62.8 percent). Possible reasons for better outcome in bilateral optic nerve injury are discussed. (+info)
Bax antisense oligonucleotides reduce axotomy-induced retinal ganglion cell death in vivo by reduction of Bax protein expression.
Following transection of the optic nerve (ON), retinal ganglion cells (RGCs) upregulate Bax protein expression and undergo apoptosis. The present study aimed at reducing Bax expression in order to test whether Bax plays a causative role in the induction of secondary RGC apoptosis. Following injection into the vitreous, fluoresceinated oligonucleotides transfected RGCs in vivo at the injection site in the temporal superior retina. Following ON lesion, and repeated injections of a partially phosphorothioated Bax antisense oligonucleotide, but not following injection of control oligonucleotides, expression of Bax protein was locally inhibited, and the number of surviving RGCs was increased in Bax antisense treated rats 8 days after axotomy. Our results indicate that Bax induction is a prerequisite for the execution of RGC apoptosis following ON axotomy. While the Bax antisense strategy offers an exciting perspective to inhibit secondary neuronal degeneration in vivo, both limited transfection efficacy, and the temporal restriction of this effect currently limit the use of this approach with respect to clinical applications for the treatment of neurodegeneration. (+info)
R-esp1, a rat homologue of drosophila groucho, is differentially expressed after optic nerve crush and mediates NGF-induced survival of PC12 cells.
The differential display reverse transcription polymerase chain reaction method was used to detect alterations in gene expression in the superior colliculus after optic nerve crush in adult rats. One of the most prominent changes observed was the selective induction of R-esp1, a homologue of the Drosophila enhancer of split locus (Groucho). Therefore, we studied the influence of R-esp1 on nerve growth factor (NGF)-induced cell survival of PC12 cells. Overexpression of R-esp1 promotes cell survival even in the absence of NGF and, conversely, it is reduced by antisense-mediated inhibition of R-esp1 expression. In conclusion, we propose a novel model in which R-esp1 protein mediates the NGF-signaling pathway. (+info)
Optic nerve crush: axonal responses in wild-type and bcl-2 transgenic mice.
Retinal ganglion cells of transgenic mice overexpressing the anti-apoptotic protein Bcl-2 in neurons show a dramatic increase of survival rate after axotomy. We used this experimental system to test the regenerative potentials of central neurons after reduction of nonpermissive environmental factors. Survival of retinal ganglion cells 1 month after intracranial crush of the optic nerve was found to be 100% in adult bcl-2 mice and 44% in matched wild-type (wt) mice. In the optic nerve, and particularly at the crush site, fibers regrowing spontaneously or simply sprouting were absent in both wt and bcl-2 mice. We attempted to stimulate regeneration implanting in the crushed nerves hybridoma cells secreting antibodies that neutralize central myelin proteins, shown to inhibit regeneration (IN-1 antibodies) (Caroni and Schwab, 1988). Again, we found that regeneration of fibers beyond the site of crush was virtually absent in the optic nerves of both wt and bcl-2 mice. However, in bcl-2 animals treated with IN-1 antibodies, fibers showed sprouting in the proximity of the hybridoma implant. These results suggest that neurons overexpressing bcl-2 are capable of surviving axotomy and sprout when faced with an environment in which inhibition of regeneration has been reduced. Nevertheless, extensive regeneration does not occur, possibly because other factors act by preventing it. (+info)
Visual outcome in optic nerve injury patients without initial light perception.
PURPOSE: To assess the prognosis for recovery of vision in patients with blindness due to head injury, and to analyse the predictive value of visual evoked potential (VEP). METHODS: One hundred consecutive patients with unilateral/bilateral blindness as a result of minor head injury were studied with regard to their visual status, CT scan, MRI scan and serial VEPs. Steroids were given to those presenting within one month of injury, 5 patients among them received methyl prednisolone. Transethmoidal decompression was done in 6 patients. RESULTS: Visual improvement was recorded in 23 patients. Initial VEP failed to reveal any wave in 29 patients and was abnormal in 71. All the 14 patients in whom VEPs were repeatedly normal, irrespective of initial VEP status, showed varying degrees of visual improvement and none of the 15 patients with persistently negative VEPs showed visual improvement. CONCLUSION: Recovery of VEP from no response to abnormal wave or abnormal wave to normal VEP were indicators of relatively good visual prognosis. Overall, 23 patients showed visual improvement, but did not return to normal. Mode of injury, CT findings and timing of surgery did not influence the outcome. (+info)