Avaliaçäo morfométrica de fibras nervosas do nervo ulnar após reparaçäo cirúrgica com auto-enxerto e prótese tubular em cäes / Morphometric evaluation of nerve fibers after surgical repair by allograft and tubular prothesis of the ulnar nerve in dogs

O objetivo da investigaçäo foi o de comparar os resultados observados por meio de avaliaçäo morfométrica de fibras nervosas regeneradas, em cäes, após 26 semanas da reparaçäo cirúrgica de falhas do nervo ulnar, através de auto-enxertos e próteses tubulares de silicone. Para cada procedimento foram utilizados quatro animais. Dos nervos regenerados e dos enxertos foram retirados segmentos para avaliaçäo em nível de microscopia eletrônica. De cada corte foram amostrados seis campos distintos com 1,750µm elevado ao quadrado cada, que foram fotografados com aumentos de 1.880 vezes. Através de sistema computadorizado de morfometria (SigmaScan - Jandel Co., USA), obtiveram-se os seguintes parâmetros: diâmetros das fibras mielínicas; diâmetros dos axônios mielínicos; espessuras das bainhas de mielina e diâmetro dos axônios amielínicos. Os nervos regenerados no interior das próteses tubulares apresentaram diâmetros das fibras mielínicas com média de 5,12ñ1,67µm; média dos diâmetros dos axônios mielínicos de 4,08ñ1,52µm; média das espessuras das bainhas de mielina de 0,52ñ0,18µm; média dos diâmetros dos axônios amielínicos de 0,98ñ0,37µm. Os enxertos apresentaram os seguintes valores: média dos diâmetros das fibras mielínicas de 6,04ñ2,27µm; média dos diâmetros dos axônios mielínicos de 4,59ñ1,95µm; média das espessuras das bainhas de mielina de 0,72ñ0,23µm; média dos diâmetros dos axônios amielínios de 0,96ñ0,40µm. Estes resultados permitiram concluir que os procedimentos cirúrgicos utilizados, quando analisadas as fibras regeneradas no interior das próteses tubulares e dos auto-enxertos, näo apresentaram diferenças morfométricas significantes, decorridas 26 semanas de observaçäo pós-operatória

Reduced sensory neuron regeneration by C57BL/6J mice

The tube repair method was used to study peripheral nerve regeneration in five different inbred mouse strains. The sciatic nerve of male adult mice of the C57BL/6J,DBA/1J, C3H/HeJ, BALB/cJ and A/J strains (N=3) was cut and both proximal and distal nerve stumps were inserted into a polyethylene tube leaving a 4-mm nerve gap. After 6 weeks the tubes containing the regenerated nerve cables were processed for total myelinated axon counts. C57BL/6J mice regenerated significantly fewer myelinated axons (1024 + or - 178, mean + or - SEM) compared to the BALB/cJ (1618+ or - 64), a/j (1788 + OR - 95), dba/1j(2168 + OR - 296) OR c3h/hEj (3468 + OR - 36) strains. Horseradish peroxidase was applied 3 mm distal to be tube 4 and 40 weeks after tube implantation to further characterize the reduced regenerative response of C57BL/6J mice. Labeled sensory and somatic motor neurons were counted in the spinal cord and L4,5,6 dorsal root ganglia (DRG), respectively. Sciatic nerves from four intact C57BL/6J mice were processed in the same fashion and used as normal controls. No significant difference in the number of motor neurons was detected between the experimental (4 weeks = 663 + or - 13) animals. However, there were fewer labeled neurons in the DRG of the operated group (4 weeks = 1163 + or - 167; 40 weeks = 2574 + or - 104) compared to the control group (4211 + or - 96). These results indicated that sensory neurons are responsible for the diminished regenerative response in C57BL/6J mice after peripheral nerve transection. Neurotrophic factors may be implicated in the reduced response, although no systematic study has been done to quantify either trophic factors or their receptor synthesis in different mouse strains during Wallerian degeneration. Diminished peripheral nerve fiber regeneration makes the C57BL/6J mouse strain an ideal experimental model to evaluate the effects of exogenous substances on nerve repair

Local addition of monosialoganglioside GM1 stimulates peripheral axon regeneration in vivo

Tubulization repair technique is a useful model to study peripheral nerve regeneration by offering quantifiable parameters to assess the possible effect of exogenously applied substances on nerve repair. In the present study we demonstrated that locally administered GM1 inside a tubular prosthesis at the time of implantation can significantly improve the repair process. The sciatic nerve of 8 male C57BL/6J mice, approximately 3 months old at the time of surgery and divided into two groups of 4 animals each, was transected and the proximal and distal nerve stumps were sutured into a polyethylene tube (PT), 0.76 mm internal diameter (ID), to bridge a nerve gap of 4 mm. The tubes contained 2 microliters of collagen type I (2.4 mg/ml) alone or in combination (1:1 volume ratio) with monosialoganglioside GM1 (10 mg/ml in the final solution). Four additional animals received a PT with 1.14 mm ID filled with 5.5 microliters of collagen/GM1 (at the same ratio and final concentration as above). After 6 weeks the PT with the regenerating nerve cables were processed for total myelinated axon counts with a computer-controlled system. GM1 significantly increased peripheral axon regeneration (3427 +/- 64 myelinated axons for the 0.76-mm PT and 3623 +/- 270 for the 1.14-mm PT, mean +/- SEM) compared to the group receiving collagen alone (2516 +/- 156) and this effect did not depend on tube diameter. This action is possibly due to a stimulating effect of GM1 on neurite outgrowth and sprouting