RESUMO
OBJECTIVES: In the clinical set, autologus nerve grafts are the current option for reconstruction of nerve tissue losses. The length of the nerve graft has been suggested to affect outcomes. Experiments were performed in the rat in order to test this assumption and to detect a possible mechanism to explain differences in recovery. METHODS: The rat median nerve was repaired by ulnar nerve grafts of different lengths. Rats were evaluated for 12 months by behavioural assessment and histological studies, including ATPase myofibrillary histochemistry and retrograde neuronal labelling. RESULTS: It was demonstrated that graft length interferes in behavioural functional recovery that here correlates to muscle weight recovery. Short nerve grafts recovered faster and better. Reinnervation was not specific either at the trunk level or in the muscle itself. The normal mosaic pattern of Type I muscle fibres was never restored and their number remained largely augmented. An increment in the number of motor fibres was observed after the nerve grafting in a predominantly sensory branch in all groups. This increment was more pronounced in the long graft group. In the postoperative period, about a 20% reduction in the number of misdirected motor fibres occurred in the short nerve graft group only. CONCLUSION: Variation in the length of nerve grafts interferes in behavioural recovery and increases motor fibres misdirection. Early recovery onset was related to a better outcome, which occurs in the short graft group.
Assuntos
Nervo Mediano/cirurgia , Músculo Esquelético/fisiologia , Transferência de Nervo/métodos , Recuperação de Função Fisiológica/fisiologia , Transplante Autólogo/métodos , Nervo Ulnar/transplante , Adenosina Trifosfatases/metabolismo , Análise de Variância , Animais , Células do Corno Anterior/metabolismo , Comportamento Animal , Benzofuranos/metabolismo , Feminino , Força da Mão/fisiologia , Histocitoquímica/métodos , Nervo Mediano/fisiopatologia , Modelos Animais , Músculo Esquelético/anatomia & histologia , Músculo Esquelético/inervação , Tamanho do Órgão/fisiologia , Desempenho Psicomotor/fisiologia , Ratos , Ratos Sprague-Dawley , Fatores de TempoRESUMO
Spinal cord injury (SCI) releases a cascade of events that leads to the onset of an inhibitory milieu for axonal regeneration. Some of these changes result from the presence of repulsive factors that may restrict axonal outgrowth after trauma. The Eph receptor tyrosine kinase (RTK) family has emerged as a key repellent cue known to be involved in neurite outgrowth, synapse formation, and axonal pathfinding during development. Given the nonpermissive environment for axonal regeneration after SCI, we questioned whether re-expression of one of these molecules occurs during regenerative failure. We examined the expression profile of EphA3 at the mRNA and protein levels after SCI, using the NYU contusion model. There is a differential distribution of this molecule in the adult spinal cord and EphA3 showed an increase in expression after several injury models like optic nerve and brain injury. Standardized semi-quantitative RT-PCR analysis demonstrated a time-dependent change in EphA3 mRNA levels, without alterations in beta-actin levels. The basal level of EphA3 mRNA in the adult spinal cord is low and its expression was induced 2 days after trauma (the earliest time point analyzed) and this upregulation persisted for 28 days post-injury (the latest time point examined). These results were corroborated at the protein level by immunohistochemical analysis and the cell phenotype identified by double labeling studies. In control animals, EphA3 immunoreactivity was observed in motor neurons of the ventral horn but not in lesioned animals. In addition, GFAP-positive cells were visualized in the ventral region of injured white matter. These results suggest that upregulation of EphA3 in reactive astrocytes may contribute to the repulsive environment for neurite outgrowth and may be involved in the pathophysiology generated after SCI.
Assuntos
Receptores Proteína Tirosina Quinases/metabolismo , Traumatismos da Medula Espinal/metabolismo , Medula Espinal/metabolismo , Regulação para Cima/fisiologia , Animais , Células do Corno Anterior/metabolismo , Astrócitos/metabolismo , Lesões Encefálicas/genética , Lesões Encefálicas/metabolismo , Lesões Encefálicas/fisiopatologia , Comunicação Celular/fisiologia , Modelos Animais de Doenças , Feminino , Regulação da Expressão Gênica/fisiologia , Proteína Glial Fibrilar Ácida/metabolismo , Cones de Crescimento/metabolismo , Inibidores do Crescimento/genética , Inibidores do Crescimento/metabolismo , Regeneração Nervosa/fisiologia , Vias Neurais/metabolismo , Vias Neurais/fisiopatologia , Traumatismos do Nervo Óptico/genética , Traumatismos do Nervo Óptico/metabolismo , Traumatismos do Nervo Óptico/fisiopatologia , RNA Mensageiro/metabolismo , Ratos , Ratos Sprague-Dawley , Receptores Proteína Tirosina Quinases/genética , Medula Espinal/fisiopatologia , Traumatismos da Medula Espinal/genética , Traumatismos da Medula Espinal/fisiopatologiaRESUMO
The Na+,K(+)-ATPase plays a key role in the regulation of ion fluxes and membrane repolarization in the CNS. We have studied glucocorticoid effects on biosynthesis of the Na+,K(+)-ATPase and on ouabain binding in the ventral horn of the spinal cord using intact rats, adrenalectomized (ADX) rats, and ADX rats receiving dexamethasone (ADX+DEX) during 4 days. Cryostat sections from spinal cords were incubated with a 35S-oligonucleotide coding for the alpha 3-subunit or a 3H-cDNA coding for the beta 1-subunit of the Na+,K(+)-ATPase using in situ hybridization techniques. In ventral horn motoneurons, grain density per cell and grain density per area of soma for both probes were slightly reduced in ADX rats but significantly increased in the ADX+DEX group, using ANOVA and the Bonferroni's test. Statistical analysis of frequency histograms of neuronal densities further indicated a significant shift to the right for intact rats compared with ADX rats for both probes. Concomitantly, [3H]ouabain binding to membrane preparations from ventral horns was reduced in ADX rats and restored to normal by DEX administration. No effect of adrenalectomy or DEX treatment was obtained in the dorsal horn. In conclusion, glucocorticoids positively modulate the mRNA for the alpha 3-subunit and the beta 1-subunit of the Na+,K(+)-ATPase and recover ouabain binding to normal values. The increments of the synthesis and activity of an enzyme affecting membrane repolarization and synaptic neurotransmission are consistent with the alleged stimulatory effect of glucocorticoids on spinal cord function.