Effects of ozone therapy on facial nerve regeneration / Efeitos da terapia com ozônio na regeneração do nervo facial

Abstract Introduction: Ozone may promote moderate oxidative stress, which increases antioxidant endogenous systems. There are a number of antioxidants that have been investigated therapeutically for improving peripheral nerve regeneration. However, no previous studies have reported the effect of ozone therapy on facial nerve regeneration. Objective: We aimed to evaluate the effect of ozone therapy on facial nerve regeneration. Methods: Fourteen Wistar albino rats were randomly divided into two groups with experimental nerve crush injuries: a control group, which received saline treatment post-crush, and an experimental group, which received ozone treatment. All animals underwent surgery in which the left facial nerve was exposed and crushed. Treatment with saline or ozone began on the day of the nerve crush. Left facial nerve stimulation thresholds were measured before crush, immediately after crush, and after 30 days. After measuring nerve stimulation thresholds at 30 days post-injury, the crushed facial nerve was excised. All specimens were studied using light and electron microscopy. Results: Post-crushing, the ozone-treated group had lower stimulation thresholds than the saline group. Although this did not achieve statistical significance, it is indicative of greater functional improvement in the ozone group. Significant differences were found in vascular congestion, macrovacuolization, and myelin thickness between the ozone and control groups. Significant differences were also found in axonal degeneration and myelin ultrastructure between the two groups. Conclusion: We found that ozone therapy exerted beneficial effect on the regeneration of crushed facial nerves in rats.

Resumo Introdução: O ozônio pode promover estresse oxidativo moderado, o que aumenta sistemas endógenos antioxidantes. Há determinado número de antioxidantes sendo investigados terapeuticamente para melhorar a regeneração do nervo periférico. No entanto, nenhum estudo anterior relatou o efeito da terapia com ozônio na regeneração do nervo facial. Objetivo: Nosso objetivo foi avaliar o efeito da terapia com ozônio na regeneração do nervo facial. Método: Ao todo, 14 ratos albinos Wistar foram divididos aleatoriamente em dois grupos com lesões experimentais por esmagamento do nervo: um grupo controle, que recebeu tratamento com solução salina pós-esmagamento; e um grupo experimental, que recebeu tratamento com ozônio. Todos os animais foram submetidos a cirurgia na qual o nervo facial esquerdo foi exposto e esmagado. O tratamento com solução salina ou ozônio se iniciou no dia do esmagamento do nervo. Os limiares de estimulação do nervo facial esquerdo foram medidos antes do esmagamento, imediatamente após o esmagamento e após 30 dias. Depois de medir limiares de estimulação do nervo aos 30 dias pós-lesão, o nervo facial esmagado foi excisado. Todas as amostras foram estudadas por meio de microscopia óptica e eletrônica. Resultados: Após o esmagamento, o grupo tratado com ozônio apresentou menores limiares de estimulação do que o grupo da solução salina. Embora isso não tenha significância estatística, é indicativo de maior melhoria funcional no grupo do ozônio. Foram encontradas diferenças significativas na congestão vascular, macrovacuolização e espessura da mielina entre os grupos do ozônio e controle. Diferenças significativas também foram encontradas na degeneração axonal e ultraestrutura de mielina entre os dois grupos. Conclusão: Verificou-se que a terapia com ozônio teve efeito benéfico sobre a regeneração dos nervos faciais esmagados em ratos.

Alteraciones de las células de la microglía del sistema nervioso central provocadas por lesiones del nervio facial / Facial nerve injuries cause changes in central nervous system microglial cells

Resumen Introducción. El grupo de investigación del Laboratorio de Neurofisiología Comportamental de la Universidad Nacional de Colombia ha descrito modificaciones estructurales y electrofisiológicas en neuronas piramidales de la corteza motora producidas por la lesión del nervio facial contralateral en ratas. Sin embargo, poco se sabe sobre la posibilidad de que dichos cambios neuronales se acompañen también de modificaciones en las células gliales circundantes. Objetivo. Caracterizar el efecto de la lesión unilateral del nervio facial sobre la activación y proliferación de las células de la microglía en la corteza motora primaria contralateral en ratas. Materiales y métodos. Se hicieron pruebas de inmunohistoquímica para detectar las células de la microglía en el tejido cerebral de ratas sometidas a lesión del nervio facial, las cuales se sacrificaron en distintos momentos después de la intervención. Se infligieron dos tipos de lesiones: reversible (por compresión, lo cual permite la recuperación de la función) e irreversible (por corte, lo cual provoca parálisis permanente). Los tejidos cerebrales de los animales sin lesión (grupo de control absoluto) y de aquellos sometidos a falsa cirugía se compararon con los de los animales lesionados sacrificados 1, 2, 7, 21 y 35 días después de la lesión. Resultados. Las células de la microglía en la corteza motora de los animales lesionados irreversiblemente mostraron signos de proliferación y activación entre el tercero y séptimo días después de la lesión. La proliferación de las células de la microglía en animales con lesión reversible fue significativa solo a los tres días de infligida la lesión. Conclusiones. La lesión del nervio facial produce modificaciones en las células de la microglía de la corteza motora primaria. Estas modificaciones podrían estar involucradas en los cambios morfológicos y electrofisiológicos descritos en las neuronas piramidales de la corteza motora que comandan los movimientos faciales.

Abstract Introduction: Our research group has described both morphological and electrophysiological changes in motor cortex pyramidal neurons associated with contralateral facial nerve injury in rats. However, little is known about those neural changes, which occur together with changes in surrounding glial cells. Objective: To characterize the effect of the unilateral facial nerve injury on microglial proliferation and activation in the primary motor cortex. Materials and methods: We performed immunohistochemical experiments in order to detect microglial cells in brain tissue of rats with unilateral facial nerve lesion sacrificed at different times after the injury. We caused two types of lesions: reversible (by crushing, which allows functional recovery), and irreversible (by section, which produces permanent paralysis). We compared the brain tissues of control animals (without surgical intervention) and sham-operated animals with animals with lesions sacrificed at 1, 3, 7, 21 or 35 days after the injury. Results: In primary motor cortex, the microglial cells of irreversibly injured animals showed proliferation and activation between three and seven days post-lesion. The proliferation of microglial cells in reversibly injured animals was significant only three days after the lesion. Conclusions: Facial nerve injury causes changes in microglial cells in the primary motor cortex. These modifications could be involved in the generation of morphological and electrophysiological changes previously described in the pyramidal neurons of primary motor cortex that command facial movements.

Retracción a largo plazo del árbol dendrítico de neuronas piramidales córtico-faciales por lesiones periféricas del nervio facial / Peripheral facial nerve lesion induced long-term dendritic retraction in pyramidal cortico-facial neurons

Introducción. Poco se sabe sobre las modificaciones morfológicas de las neuronas de la corteza motora tras lesiones en nervios periféricos, y de la implicancia de dichos cambios en la recuperación funcional tras la lesión. Objetivo. Caracterizar en ratas el efecto de la lesión del nervio facial sobre la morfología de las neuronas piramidales de la capa V de la corteza motora primaria contralateral. Materiales y métodos. Se reconstruyeron neuronas piramidales teñidas con la técnica de Golgi-Cox, de animales control (sin lesión) y animales con lesiones y sacrificados a distintos tiempos luego de la lesión. Se utilizaron cuatro grupos: sham (control), lesión 1S, lesión 3S y lesión 5S (animales con lesiones y evaluados 1, 3 y 5 semanas después de la lesión irreversible del nervio facial, respectivamente). Se evaluaron mediante el análisis de Sholl, las ramificaciones dendríticas de las células piramidales de la corteza motora contralateral a la lesión. Resultados. Los animales con lesiones presentaron parálisis completa de las vibrisas mayores durante las cinco semanas de observación. Comparadas con neuronas de animales sin lesiones, las células piramidales córtico-faciales de los lesionados mostraron una disminución significativa de sus ramificaciones dendríticas. Esta disminución se mantuvo hasta cinco semanas después de la lesión. Conclusiones. Las lesiones irreversibles de los axones de las motoneuronas del núcleo facial, provocan una retracción sostenida del árbol dendrítico en las neuronas piramidales córtico-faciales. Esta reorganización morfológica cortical persistente podría ser el sustrato fisiopatológico de algunas de las secuelas funcionales que se observan en los pacientes con parálisis facial periférica.

Introduction. Little evidence is available concerning the morphological modifications of motor cortex neurons associated with peripheral nerve injuries, and the consequences of those injuries on post lesion functional recovery. Objective. Dendritic branching of cortico-facial neurons was characterized with respect to the effects of irreversible facial nerve injury. Materials and methods. Twenty-four adult male rats were distributed into four groups: sham (no lesion surgery), and dendritic assessment at 1, 3 and 5 weeks post surgery. Eighteen lesion animals underwent surgical transection of the mandibular and buccal branches of the facial nerve. Dendritic branching was examined by contralateral primary motor cortex slices stained with the Golgi-Cox technique. Layer V pyramidal (cortico-facial) neurons from sham and injured animals were reconstructed and their dendritic branching was compared using Sholl analysis. Results. Animals with facial nerve lesions displayed persistent vibrissal paralysis throughout the fiveweek observation period. Compared with control animal neurons, cortico-facial pyramidal neurons of surgically injured animals displayed shrinkage of their dendritic branches at statistically significant levels. This shrinkage persisted for at least five weeks after facial nerve injury. Discussion. Irreversible facial motoneuron axonal damage induced persistent dendritic arborization shrinkage in contralateral cortico-facial neurons. This morphological reorganization may be the physiological basis of functional sequelae observed in peripheral facial palsy patients.

Regeneração pós-traumática do nervo facial em coelhos / Posttraumatic facial nerve regeneration in rabbits

A paralisia facial periférica traumática constitui-se em afecção freqüente. OBJETIVO: estudo da regeneração pós-traumática do nervo facial em coelhos, por avaliação funcional histológica dos nervos traumatizados comparados aos normais contralaterais. METODOLOGIA: Vinte coelhos foram submetidos à compressão do tronco do nervo facial esquerdo e sacrificados após duas (grupo AL), quatro (BL) e seis (CL) semanas da lesão. A comparação entre os grupos foi feita pelas densidades total e parcial de axônios mielinizados. ESTUDO ESTATíSTICO: método de Tukey (p < 0,05). RESULTADOS: Houve recuperação funcional parcial após duas, e completa após cinco semanas. Na análise qualitativa, verificou-se em AL um padrão degenerativo, com maior processo inflamatório tecidual. Em BL, sinais de regeneração neural, praticamente completa em CL. Os nervos normais (N) apresentaram DT média de 15705,59 e DP média de 21800,75. O grupo BL revelou DT média de 10818,55 e DP média de 15340,56 e o CL, DT média de 13920,36 e DP média de 16589,15. BL obteve 68,88 por cento, e o grupo CL, 88,63 por cento da DT de N. N mostrou DP maior que os lesados; porém, esta não evidenciou diferença estatística entre BL e CL. A DT dos nervos revelou-se um método analítico mais fidedigno do que a DP estudada.

Posttraumatic facial paralysis is a frequent disease. This work studies posttraumatic regeneration of the facial nerve in rabbits. Functional and histological analysis compared injured and normal nerves on opposite sides. The left facial nerve trunk of twenty rabbits were subjectedto compression lesion, and sacrificed after two (subgroup AL), four (BL) and six (CL) weeks. Comparison between groups was made by analysing total and partial densities of myelinated axons. STATISTICAL ANALYSIS: Tukey Method (p<0.05). RESULTS:There was partial functional recovery after two weeks, and complete recovery after five weeks. Qualitative analysis demonstrated a degenerative pattern in the AL group, with an increased tissue inflammatory process. Evident regeneration signs were observed in the BL group, and almost complete regeneration was seen in the CL group. Normal nerves (N) had an average TD of 15705.59 and average PD of 21800.75. The BL group had an average TD of 10818.55 and an average PD of 15340.56. The CL group had an average TD of 13920.36 and an average PD of 16589.15. The BL group had an average TD of N equal to 68.88 percent, and the CL group had an average TD of N equal to 88,63 percent (statistically significant). N showed a significant higher PD than injured nerves. However, this was not statistically different between BL and CL subgroups. Nerve DT was a more reliable method than PD in this study.