[Peripheral nerve regeneration in mice exposed to an enriched environment]. / Regeneración nerviosa periférica en ratones expuestos a un ambiente enriquecido.

INTRODUCTION: Taking into account the fact that the literature contains no studies on how an enriched environment influences peripheral nerve lesions, in this study we analysed the characteristics of the sciatic nerve in mice submitted to axonotmesis and subsequent exposure to an enriched environment. MATERIALS AND METHODS: Twenty-four male Wistar mice (198.66 +/- 11.61 g) were distributed into the following groups: control, lesion, enriched environment grouping (EEG) and simple environment grouping (SEG). Following lesion to the nerve, the animals were placed in different cages according to the groups they had been allocated to. The enriched cage had an exercise wheel, a ladder, a ramp, and mobile food and water compartments, which were randomly changed every day. After 24 days, the sciatic nerve was analysed quantitatively, morphometrically and functionally. RESULTS: The number of axons in the EEG and SEG groups was higher than that of the control group (p < 0.05). The SEG group had a higher number of axons than the lesion and EEG groups. The diameter of the axons in the experimental groups was smaller than that of the control group. The same occurred with the diameter of the nerve fibre. The thickness of the myelin sheath was inferior in the experimental groups compared to the control, and the value for the SEG group was lower than for the lesion group. The G ratio did not differ among groups. There were no differences in the values of the sciatic function index among the groups, while in the intragroup comparison there was a difference between postoperative days 7 and 14 and the preoperative values. Functioning was restored at postoperative day 21. CONCLUSIONS: The enriched environment did not have a negative effect on axonal regeneration and maturation, but neither did it favour the process. Functional recovery was not influenced by this form of intervention.

Exercício imediato versus tardio na regeneração do nervo isquiático de ratos após axoniotmese: análise histomorfométrica e funcional / Immediate versus later exercises for rat sciatic nerve regeneration after axonotmesis: histomorphometric and functional analyses

OBJETIVO: Devido à controvérsia sobre o melhor momento para iniciar o exercício físico, bem como sua influência sobre a regeneração nervosa periférica, este estudo realizou uma análise histomorfométrica e funcional para avaliar a influência do exercício físico em esteira, aplicado nas fases imediata e tardia da regeneração do nervo isquiático de ratos, após axoniotmese. MÉTODOS: Vinte ratos Wistar machos (229,05±18,02g) foram divididos nos grupos: controle (CON); desnervado (D); desnervado+exercício+gaiola (DEG) e desnervado+ gaiola+exercício (DGE). Após 24 horas da axoniotmese, o grupo DEG iniciou o exercício, enquanto o grupo DGE iniciou no 14º dia, com o seguinte protocolo: velocidade=8m/min, inclinação=0 por cento, 30min/dia, durante 14 dias. Em seguida, a porção distal do nervo isquiático foi retirada para análise histomorfométrica. Realizou-se o registro da marcha (pré-operatório e 7º, 14º, 21º, 28º dias pós-operatório (PO)), através do índice funcional do ciático (IFC). RESULTADOS: O número de axônios regenerados nos grupos D foi maior que no CON (p<0,05), não havendo diferença intergrupos D. O diâmetro do axônio do grupo DGE foi maior que do grupo D, enquanto os demais parâmetros morfométricos apenas apresentaram diferença significativa com o grupo CON. Não houve diferença nos valores de IFC intergrupos, enquanto na comparação intragrupos, o 7º e o 14º dias diferem do pré-operatório, 21º e o 28º dias PO. CONCLUSÕES: O protocolo de exercício em esteira aplicado nas fases imediata e tardia, não influenciou o brotamento axonal, o grau de maturação das fibras regeneradas e nem a funcionalidade dos músculos reinervados.

OBJECTIVE: Considering the controversies regarding the best period to begin physical exercise in relation to peripheral nerve regeneration, along with its influence on regeneration, this study accomplished a histomorphometric and functional analysis to evaluate the influence of physical exercise on a treadmill, applied to the immediate and late stages of sciatic nerve regeneration in rats following crushing injury. METHODS: Twenty male Wistar rats (229.05±18.02g) were divided into the following groups: control (CON); denervated (D); denervated+exercise+cage (DEC) and denervated+cage+exercise (DCE). The DEC group started the exercise 24 hours after the nerve injury, while the DCE group started on the 14th day after the injury, with the following protocol: speed=8m/min, inclination=0 percent, 30min/day, for 14 days. The distal segment of the sciatic nerve was then removed for histomorphometric analysis. The gait was recorded before the operation and on the 7th, 14th, 21st and 28th days after the operation, using the sciatic functional index (SFI). RESULTS: The number of regenerated axons in the D groups was greater than in the CON group (p<0.05), without differences between the D groups. The axon diameter in the DCE group was greater than the diameter in the D group, whereas the other morphometric parameters only showed significant differences with the CON group. There was no difference in SFI values between the groups, whereas within the groups, the 7th and 14th days differed from the values before the operation and on the 21st and 28th days after the operation. CONCLUSIONS: The treadmill exercise protocol that was applied to the immediate and late stages of nerve regeneration did not influence the axonal budding, the degree of maturation of the regenerated nerve fibers or the functional performance of the reinnervated muscles.

[Electrical stimulation and swimming in the acute phase of axonotmesis: their influence on nerve regeneration and functional recovery]. / Estimulación eléctrica y natación en la fase aguda de la axonotmesis: influencia sobre la regeneración nerviosa y la recuperación funcional.

INTRODUCTION: Little attention has been given to the influence of low-frequency phasic electrical stimulation (LFPES) and physical exercise on the quality of peripheral nerve regeneration and functional recovery. AIM. To evaluate the influence of LFPES, swimming and the association between the two in terms of the morphology of the regenerated sciatic nerve following axonotmesis. MATERIALS AND METHODS: Thirty Wistar mice (222.05 +/- 42.2 g) were distributed into groups: control (C), denervated (D), denervated + swimming (DS), denervated + electrostimulation (DE) and denervated + swimming + electrostimulation (DSE). After 24 hours of axonotmesis, the soleus muscle of the DE and DSE groups was stimulated electrically. The DS and DSE groups swam over a period of 22 days. The number of axons, morphometric data on the nerve and the functional index of the sciatic nerve (FIS) were evaluated. RESULTS: The number of axons in the denervated groups was higher than in the control group, and in the DE group the figure was higher than in the D group. The axonal diameter was smaller in the denervated groups, yet in the DS group it was higher than in the D group. The other morphometric parameters were quite similar to those of the C group. The FIS between days 7 and 14 of the post-operative period was different to the pre-operative index and that measured on day 21 of the post-operative period; the DSE group, however, differed from the pre-operative values. CONCLUSIONS: Swimming and LFPES, applied on an individual basis, do not affect the maturation of the regenerated fibres or functional recovery. LFPES favoured axonal regeneration and combining the treatments delayed functional recovery without having any influence on nerve regeneration.

Analise morfometrica dos tecidos muscular e conjuntivo apos desnervacao e estimulacao eletrica de baixa frequencia / Morphometric analysis of muscle and conjunctive tissue after denervation and low-frequency electrial stimulation

A estimulacao eletrica muscular tem sido empregada apos lesao nervosa periferica com o objetivo de minimizar a atrofia e a fraqueza muscular. Experimentos tem demonstrado que ha plasticidade nas fibras musculares, sendo o musculo capaz de sofrer adaptacoes ante fatores como a desnervacao e a estimulacao eletrica. Objetivo: analisar a influencia da estimulacao eletrica sobre o perfil morfometrico do musculo soleo de ratos desnervado por esmagamentodo nervo isquiatico. Metodo: foram utilizados 18 ratos Wistar (196,86g+-33,67) divididos em 3 grupos(n=6): desnervado+estimulacao eletrica (DEE); desnervado(D); e controle(C). Vinte e quatro horas apos o esmagemento do nervo iniciou-se a estimulacao eletrica muscular no grupo DEE(i=5mA, Fase=3ms, f=10Hz) por 30 minutos, durante 20 dias consecutivos. O musculo soleo foi retirado para analise morfometrica. Ressultados: a area medica de seccao transversa das fibras musculares do grupo C foi de 1.035 um2+-210, no grupo D foi de 375 um2+-65 e no grupo DEE, de 600 um2+-126(P<-0,05). A densidade de area do tecido conjuntivo foi significativamente menor (P<-0,05) no grupo DEE (16,61 por cento +- 3,68) em relacao ao D(34,49 por cento +- 4,32), sendo que ambos os grupos apresentaram valores maiores que o grupo C (9,55 por cento +- 2,62). A densidade de area das fibras do musculo soleo foi significativamente maior (P<-0,05) no grupo DEE(83,37 por cento +- 3,68) quando comparada ao grupo D (65,49 por cento +- 4,32). A estimulacao eletrica de baixa frequencia minimizou a atrofia das fibras musculares e a proliferacao de tecido conjuntivo no musculo desnervado

Axonal regeneration through muscle autografts submitted to local anaesthetic pretreatment.

Freeze-thawed muscle grafts (FTMG) have been used as an alternative to nerve grafts for the reconstruction of peripheral nerve defects, although their use has some disadvantages. For instance, FTMG may fragment easily after freeze-thawing, a fact impairing their use for surgery. In this study we describe a method to obtain muscle autografts based on the myotoxic properties of local anaesthetics. Fifteen adult rats had their left tibialis anterior muscles injected transcutaneously with 0.3 ml of 2% lidocaine hydrochloride. Twenty-four hours later the injected muscle was removed and a lidocaine muscle graft (LMG) was obtained by trimming the muscle to a rectangular block of approximately 1.0 cm in length. The left sciatic nerve was exposed in the mid-thigh region and a segment removed so that a final 1.0 cm-long gap was produced. The LMG was coaxially autografted to the epineurium between the proximal and distal nerve stumps. In another 15 rats, the sciatic nerve gap was repaired with FTMG obtained from the tibialis anterior muscle. Surgical procedures were similar in both groups. Axonal regeneration and muscle reinnervation were studied quantitatively and ultrastructurally 60 days after the insertion of LMG and FTMG. The results showed that axonal regeneration with the LMG was qualitatively similar to that observed with the FTMG, with no significant differences between groups. We conclude that LMG was a successful muscle graft and a suitable alternative to other denaturing methods, without the disadvantages of FTMG.