Peroneal nerve reconstruction by using glycerol-preserved veins: histological and functional assessment in rats

PURPOSE: To compare the degree of neural regeneration in rats upon interposition of autologous nerve graft, autogenous vein, glycerol-preserved autogenous vein, and glycerol-preserved allogeneic vein using qualitative and quantitative histological analyses as well as functional assessments. METHODS: Peroneal nerves were reconstructed differently in four groups of animals. Functional assessments were performed pre- and postoperatively for a period of six weeks. After six weeks, the animals were sacrificed and histological evaluations were performed. RESULTS: Histological patterns of autogenous veins without preservation showed pronounced neoangiogenesis and extensive axonal rarefaction, as confirmed by axonal counting and functional assessments. Glycerol-preserved veins had results similar to the control. CONCLUSIONS: Glycerol-preserved autogenous or allogeneic veins showed similar results to autograft results. The autogenous vein (without preservation in glycerol) presented histological and functional outcomes statistically lower than other groups.

Pharmacological immunomodulation enhances peripheral nerve regeneration

To assess the effect of N-Acetylmuramyl-L-Alanyl-D-Isoglutamine MDP topically administrated on the regenerating peripheral neurons, twelve male C57BL/6J adult mice were equally distributed into three groups. Four mice underwent unilateral sciatic nerve transection and polyethylene tubulization, with a 4mm gap between the proximal and distal nerve stumps and were implanted with collagen + PBS (COL). Other four animals underwent the same surgical procedure but received collagen + MDP (COL/MDP) inside the prosthesis. Four animals were not operated and served as control group (NOR). After 4 weeks, the regenerated nerve cables were processed for total myelinated axon counting and myelinated fiber diameter measurement. The L5 dorsal root ganglion (DRG) was also removed and sectioned for sensory neurons counting and measurement. The results revealed significant difference (p<0.05) in axonal counting among the groups NOR (4,355±32), COL (1,869±289) and COL/MDP (2,430±223). There was a significant reduction in the axonal diameter in the operated groups (COL=3.38µm±1.16 and COL/MDP=3.54µm±1.16) compared to NOR (6.19µm±2.45). No difference was found in the number of DRG neurons between the experimental groups (COL=564±51; COL/MDP=514±56), which presented fewer sensory neurons compared to NOR (1,097±142). Data obtained indicate that locally applied MDP stimulates peripheral nerve regeneration in mice.

Para avaliar o efeito do NAcetilmuramil- L-Alanil-D-Isoglutamina administrado topicamente em neurônios periféricos em regeneração, doze camundongos C57BL/6J machos adultos foram igualmente separados em três grupos. Quatro animais sofreram transecção unilateral do nervo ciático que foi ancorado no interior de um tubo de polietileno, mantendo-se 4 mm de distância entre as extremidades dos nervos e receberam colágeno + PBS (COL) dentro do tubo. Outros quatro animais sofreram o mesmo procedimento cirúrgico, porém receberam colágeno + MDP (COL/MDP) no interior da prótese. Quatro animais não foram operados e serviram como controle de normalidade (NOR). Após quatro semanas, os cabos de regeneração foram coletados para determinação do número de axônios mielínicos e da mêdia do diâmetro das fibras mielínicas regeneradas. O gânglio da raiz dorsal L5 também foi coletado para contagem e mensuração dos neurônios sensitivos. Os resultados revelaram diferença significativa no número de axônios entre os grupos NOR (4355±32), COL (1869±289) e COL/MDP (2430±223). Houve redução significativa no diâmetro das fibras mielínicas nos grupos que receberam as próteses tubulares (COL=3,38µm±1,16 e COL/ MDP=3,54µm±1,16) quando comparados ao grupo NOR (6,19µm±2,45). O número de neurônios não diferiu entre os grupos experimentais (COL=564±51 e COL/MDP=514±56), os quais apresentaram menor número de neurônios sensitivos em relação ao grupo não operado (NOR=1097±142). Os dados obtidos indicam que a aplicação local do MDP estimula a regeneração de nervos em camundongos.

Intervençöes farmacológicas no trauma raquimedular: uma nova visäo terapêutica / Pharmacological interventions in spinal cord trauma: a therapeutic approach

O imenso déficit neurológico decorrente da lesao da medula espinhal advém do somatório de dois eventos distintos: a lesao mecânica inicial e a lesao endógena secundária conseqüente à primeira. A lesao secundária da medula espinhal envolve complexas mudanças bioquímicas, que podem ser minimizadas pela introduçao de agentes farmacológicos recentes. Para limitar o dano tecidual e promover o reparo funcional, essas alteraçoes teciduais patológicas devem ser interrompidas. Avanços clínicos e científicos indicam que as lesoes agudas na medula espinhal podem ser manipuladas por terapêuticas farmacológicas utilizadas em curto espaço de tempo. A metilprednisolona administrada dentro das primeiras oito horas pós-trauma é o primeiro agente farmacológico a demonstrar melhora significativa na recuperaçao do trauma raquimedular em seres humanos. Outras drogas, como tilirazade e o GM-1, ainda sob investigaçao clínica, apresentam excelentes resultados preliminares. Esses avanços podem representar grande melhora na qualidade de vida de pacientes com lesao da medula espinhal, desde que sejam adotados pela prática clínica.

An ultrastructural study of the temporal progress of neuromuscular junction regeneration after sciatic nerve transection and tubulization repair

The aim of this investigation was to study the timecourse of motor endplates in the extensor digitorum logus (EDL) muscle after peripheral nerve transection and tubulization repair. Adult male C57BL/6J mice received sciatic nerve transection at midhigh level and both proximal and distal nerve stumps were stured into a 5-mm long polyethylene tube to bridge a final nerve gap distance of 3mm. At 2 to 40 weeks postoperatively the EDL muscle on the operated side was fixed in situ and processed histochemically for visualization of cholinesterase-rich sites. Groups of muscle fibers containing motor endplates were then processed for electron microscopy (EM). Two weeks after tubulization the EDL muscle was entirely denervated: Schwann cells came into contact with the post-synaptic folds of the muscle fibers; there was an increase in concentration of collagen and fibroblasts at the synaptic sites. Reinnervation began 4 weeks after tube implantation, when the first axon terminals established contact with a small portion of the specialized subneural region, many synaptic folds were still covered by collagen fibers and, in some cases, Schwann cells remained interposed between the folds and the synaptic terminals. Twelve weeks after surgery all the neuromuscular junctions examined were reinnervated and looked normal; motor terminals were alawys located at the primary synaptic clefts, although rarely some subneural folds lacking nerve terminals were seen. At 12 to 40 weeks all motor endplates appeared normally innervated by EM criteria.