Ciro Ferreira da Silva

Correlation between parameters of electrophysiological, histomorphometric and sciatic functional index evaluations after rat sciatic nerve repair

The rat sciatic nerve is a well-established model for the study of recovery from peripheral nerve injuries. Traditional methods of assessing nerve regeneration after nerve injury and repair, such as electrophysiology and histomorphometry, despite widely used in neural regeneration experiments, do not necessarily correlate with return of motor and sensory functions. The aim of this experimental study is to investigate the possible correlation between several parameters of peripheral nerve regeneration after repair of sectioned sciatic nerve in Wistar rat. A two-stage approach was used to obtain 17 parameters after electrophysiological, morphometric and sciatic functional index evaluations. Pearsons correlation analysis was performed between these results. Only two positives correlations between different classes of peripheral nerve assessments were noted, between sciatic functional index and proximal nerve fiber diameter (r=0.56, p<0.01) and between sciatic functional index and distal fiber diameter (r=0.50, p<0.01). The data presented in our study demonstrates that there is a poor correlation between the sciatic functional index and outcome measures of electrophysiological and morphometric evaluations.

Mesenchymal bone marrow stem cells within polyglycolic acid tube observed in vivo after six weeks enhance facial nerve regeneration

Autografting is the gold-standard method for facial nerve repair with tissue loss. Its association with high-quality scaffolds and cell implants has disclosed distinct experimental outcomes. The aim of this study was to evaluate the functional and histological effects of bone marrow stem cells (BMSC) combined with polyglycolic acid tube (PGAt) in autografted rat facial nerves. After neurotmesis of the mandibular branch of the rat facial nerve, surgical repair consisted of nerve autografting (groups A-E) contained in pGAT (groups B-E), filled with basement membrane matrix (groups C-E) with undifferentiated BMSC (group D) or Schwann-like cells that had differentiated from BMSC (group E). Axon morphometrics and an objective compound muscle action potentials (CMAP) analysis were conducted. Immunofluorescence assays were carried out with Schwann cell marker S100 and anti-β-galactosidase to label exogenous cells. Six weeks after surgery, animals from either cell-containing group had mean CMAP amplitudes significantly higher than control groups. Differently from other groups, facial nerves with Schwann-like cell implants had mean axonal densities within reference values. This same group had the highest mean axonal diameter in distal segments. We observed expression of the reporter gene lacZ in nerve cells in the graft and distally from it in groups D and E. Group-E cells had lacZ coexpressed with S100. In conclusion, regeneration of the facial nerve was improved by BMSC within PGAt in rats, yet Schwann-like cells were associated with superior effects. Accordingly, groups D and E had BMSC integrated in neural tissue with maintenance of former cell phenotype for six weeks.

Electrophysiologic assessment of regeneration in rat sciatic nerve repair using suture, fibrin glue or a combination of both techniques

We evaluated the repair of sectioned rat sciatic nerve by the comparison of electrophysiologic parameters. The repair was effected with suture (group A), fibrin glue (group B) or a combination of both techniques (group C). The amplitude, latency and conduction velocity of the motor and nerve action potentials were assessed before the nerve section and at reoperation after 24 weeks. There was no difference between the groups when the nerve action potential was evaluated. Rats of group B presented better results than those of group A (p<0.05) when latency and the nerve conduction velocity assessed at the reoperation, and the ratio between the conduction velocity at the reoperation and before the nerve section in the motor action potential evaluation were measured. Animals of group C presented better results than those of group A when the ratio between the conduction velocity of motor action potential at the reoperation and before the nerve division was considered (p<0.05). No difference between groups B and C was found. We conclude that repair using fibrin glue presented better results than suture following transection of sciatic nerve when the motor action potential was evaluated in the rat experimental model.

A utilização do tubo de ácido poliglicólico e FK506 na regeneração de nervos periféricos

Extensive losses of neural tissue preclude the repair performed by means of primary anastomosis. In those cases, nerve autograft is considered as the treatment of choice. The synthetic tube constituted by polyglycoic acid is an option for nerve graft. The FK506 is an immunosuppressive agent, which increases the neural regeneration rates in vivo and in vitro. The purpose of this study was to compare, in rats, the degree of neural regeneration, by using histological analysis, a count of the number of regenerated myelinated axons, and a functional analysis, obtained by interposing the autogenous graft (group A), polyglycoic acid tube (group B) and a combination of polyglycoic acid tube with FK506 (group C) in 5-cm defects of the sciatic nerve. Neuroma formation was observed only in group A. Groups B and C presented similar histological patterns. The quantitative analysis of the number of regenerated myelinated axons has determined that: 1) group B presented, in average, a lower number when compared to the other groups; 2) there was no significant difference between control group A and group C. For functional recovery, there was no statistically significant change between the three groups, despite the qualitative and quantitative histological differences seen.

Effects of hyperbaric oxygen therapy on facial nerve regeneration

Conclusion. Hyperbaric oxygen treatment (HBOT) promoted an increase of the mean axonal diameter in the group evaluated 2 weeks after lesion induction, which suggests a more advanced regeneration process. However, the number of myelin nerve fibers of the facial nerve of the rabbits was similar when compared to the control and treatment groups, in both evaluation periods. Objective. To evaluate the effect of HBOT on the histological pattern of the facial nerve in rabbits exposed to a nerve crush injury. Materials and methods. Twenty rabbits were exposed to facial nerve crush injury. Ten rabbits received HBOT, 10 rabbits comprised the control group. The rabbits were sacrificed 2 and 4 weeks after the trauma. Qualitative morphological analysis, measurement of the external axonal diameters and myelin fiber count were carried out in an area of 185 000 µm2. Results. There was an increase in the area of the axons and thicker myelin in the 2 weeks treatment group in comparison with the control group. The mean diameter of the axons was of 2.34 µm in the control group and of 2.81 µm in the HBOT group, with statistically significant differences. The 2 week control group had a mean number of myelin fibers of 1865.2±664, and the HBOT group had a mean number of 2026.3±302; this was not statistically significant. The 4 week control group presented a mean of 2495.1±479 fibers and the HBOT group presented a mean of 2359.9±473; this was not statistically significant.CONCLUSION Hyperbaric oxygen treatment (HBOT) promoted an increase of the mean axonal diameter in the group evaluated 2 weeks after lesion induction, which suggests a more advanced regeneration process. However, the number of myelin nerve fibers of the facial nerve of the rabbits was similar when compared to the control and treatment groups, in both evaluation periods. OBJECTIVE To evaluate the effect of HBOT on the histological pattern of the facial nerve in rabbits exposed to a nerve crush injury. MATERIALS AND METHODS Twenty rabbits were exposed to facial nerve crush injury. Ten rabbits received HBOT, 10 rabbits comprised the control group. The rabbits were sacrificed 2 and 4 weeks after the trauma. Qualitative morphological analysis, measurement of the external axonal diameters and myelin fiber count were carried out in an area of 185 000 microm2. RESULTS There was an increase in the area of the axons and thicker myelin in the 2 weeks treatment group in comparison with the control group. The mean diameter of the axons was of 2.34 microm in the control group and of 2.81 microm in the HBOT group, with statistically significant differences. The 2 week control group had a mean number of myelin fibers of 1865.2 +/- 664, and the HBOT group had a mean number of 2026.3 +/- 302; this was not statistically significant. The 4 week control group presented a mean of 2495.1 +/- 479 fibers and the HBOT group presented a mean of 2359.9 +/- 473; this was not statistically significant.

Posttraumatic facial nerve regeneration in rabbits

UNLABELLED 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 subjected to 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%, and the CL group had an average TD of N equal to 88,63% (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.

Evaluation of the systemic use of riluzole in post-traumatic facial nerve regeneration: experimental study in rabbits.

Conclusions. Riluzole promoted increase and/or preservation of axon density in the animals treated with this drug as compared to the control group; it did not increase the mean diameter of facial nerve fibres as compared to the non-treated group; and it did not provide a better functional motor recovery than in the control group. Objective. Traumatic peripheral facial paralysis is a frequent affection. In incomplete nerve injuries, systemic drugs acting on regeneration may decrease the patients period of morbidity. This study aimed to determine the effect of the drug riluzole on regeneration of the facial nerve of rabbits submitted to post-traumatic facial paralysis. Materials and methods. Eighteen rabbits were submitted to compression of the facial nerve and divided into control (A) and treated (B) groups. The animals were sacrificed 4 weeks after the injury and their nerves were studied regarding density of myelinated axons and measure of external axon diameters. Results. Partial functional recovery was observed within 2 weeks and complete recovery 5 weeks after injury. Mean neural density was 12 679.7 axons/mm2 (SD±237.5) in group A, and 19 073.8 axons/mm2 (SD±3549.9) in group B. Group A presented less than two-thirds the density of group B. There was no statistical difference in axon diameters between the studied groups.

Tubo de ácido poliglicólico e GM1 na regeneração de nervos periféricos

INTRODUCAO: A auto-enxertia de nervo e considerada tratamento de escolha nas grandes perdas de tecido neural que nao permitam a reparacao atraves de anastomose primaria. Nesses casos, o tubo sintetico a base de acido poliglicolico e uma alternativa para enxertia de nervo. Por outro lado, muitos estudos tem enfatizado a importância dos fatores neurotroficos na regeneracao neural: o monossialotetraesosilgangliosideo (GM1), um dos principais glicoesfingolipides do tecido nervoso de mamiferos, e tido como potencializador dos efeitos desses fatores. OBJETIVO: Comparar, em ratos, o grau de regeneracao neural, utilizando analise histologica, contagem do numero de axonios mielinizados regenerados e analise funcional com a utilizacao do neurotubo e do GM1. METODOS: Essa avaliacao foi obtida com a interposicao de enxerto autogeno (grupo A), tubo de acido poliglicolico (grupo B) e da associacao do tubo de acido poliglicolico a administracao de GM1 (grupo C) em defeitos de 5 mm no nervo ciatico. RESULTADOS: Foi observada formacao de neuroma apenas no grupo A. Os grupos A e C apresentaram padroes histologicos semelhantes, exceto que os axonios regenerados do grupo C apresentavam-se mais organizados e mielinizados que o grupo A. CONCLUSAO: Na recuperacao funcional, nao houve diferenca estatisticamente significativa entre os tres grupos, a despeito das diferencas histologicas qualitativas e quantitativas verificadas.

Regeneração pós-traumática do nervo facial em coelhos

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%, and the CL group had an average TD of N equal to 88,63% (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.

Quantitative histological analysis of the mandibular branch of the facial nerve in rats

PURPOSE To establish a model to quantitative histological analysis of the mandibular branch of the facial nerve in rats. METHODS Eleven Wistar rats had their right and left mandibular branches of the facial nerve surgically removed and were sacrificed afterwards. Quantitative histological analysis was performed with: a) partial number of axons; b) partial area of the transversal cut of the nerve (9000 μm(2)); c) partial density. The averages of partial density were obtained. The statistical study was established by Wilcoxon test (p=0.05). RESULTS In relation to density of axons, comparison between sides shows no statistically significant difference (p=0.248; p=0.533). Mean partial density of distal and proximal samples was, respectively, 0.18 ± 0.02 and 0.19 ± 0.02 axons/μm(2). Comparison between proximal and distal samples shows no statistically significant difference (p=0.859; p=0.182). CONCLUSION This study has successfully established a model to histological quantitative analysis of the mandibular branch of the facial nerve in rats.