REUNION OF STUMPS OF SMALL NERVES BY TUBULATION INSTEAD OF SUTURE

Update on nerve repair by biological tubulization

Many surgical techniques are available for bridging peripheral nerve defects. Autologous nerve grafts are the current gold standard for most clinical conditions. In selected cases, alternative types of conduits can be used. Although most efforts are today directed towards the development of artificial synthetic nerve guides, the use of non-nervous autologous tissue-based conduits (biological tubulization) can still be considered a valuable alternative to nerve autografts. In this paper we will overview the advancements in biological tubulization of nerve defects, with either mono-component or multiple-component autotransplants, with a special focus on the use of a vein segment filled with skeletal muscle fibers, a technique that has been widely investigated in our laboratory and that has already been successfully introduced in the clinical practice.

Poly(amidoamine) Hydrogels as Scaffolds for Cell Culturing and Conduits for Peripheral Nerve Regeneration

Biodegradable and biocompatible poly(amidoamine)-(PAA-) based hydrogels have been considered for different tissue engineering applications. First-generation AGMA1 hydrogels, amphoteric but prevailing cationic hydrogels containing carboxylic and guanidine groups as side substituents, show satisfactory results in terms of adhesion and proliferation properties towards different cell lines. Unfortunately, these hydrogels are very swellable materials, breakable on handling, and have been found inadequate for other applications. To overcome this problem, second-generation AGMA1 hydrogels have been prepared adopting a new synthetic method. These new hydrogels exhibit good biological propertiesin vitrowith satisfactory mechanical characteristics. They are obtained in different forms and shapes and successfully testedin vivofor the regeneration of peripheral nerves. This paper reports on our recent efforts in the use of first-and second-generation PAA hydrogels as substrates for cell culturing and tubular scaffold for peripheral nerve regeneration.

Types of neural guides and using nanotechnology for peripheral nerve reconstruction

Peripheral nerve injuries can lead to lifetime loss of function and permanent disfigurement. Different methods, such as conventional allograft procedures and use of biologic tubes present problems when used for damaged peripheral nerve reconstruction. Designed scaffolds comprised of natural and synthetic materials are now widely used in the reconstruction of damaged tissues. Utilization of absorbable and nonabsorbable synthetic and natural polymers with unique characteristics can be an appropriate solution to repair damaged nerve tissues. Polymeric nanofibrous scaffolds with properties similar to neural structures can be more effective in the reconstruction process. Better cell adhesion and migration, more guiding of axons, and structural features, such as porosity, provide a clearer role for nanofibers in the restoration of neural tissues. In this paper, basic concepts of peripheral nerve injury, types of artificial and natural guides, and methods to improve the performance of tubes, such as orientation, nanotechnology applications for nerve reconstruction, fibers and nanofibers, electrospinning methods, and their application in peripheral nerve reconstruction are reviewed.

Estudo comparativo da ação do fator de crescimento de fibroblastos e fragmentos de nervo na regeneração de nervo tibial em ratos

OBJETIVO: Comparar quantitativamente, a estimulação da regeneração do nervo tibial de ratos pelo Fator de Crescimento de Fibroblastos e por fragmentos de nervo dentro tubos de silicone. MÉTODOS: Foram utilizados 18 ratos da raça Wistar. A cirurgia consistiu inicialmente na ressecção de um segmento de 8 mm do nervo tibial, seguida da interposição com tubos de silicone. No lado direito, o tubo foi preenchido com solução de Fator de Crescimento de Fibroblastos (FGF) e, no lado esquerdo, com segmentos do nervo cortados em fragmentos de 1 mm. Após três meses, os animais foram submetidos a nova cirurgia para exposição dos nervos tibiais ao marcador neuronal Fluro-Gold®. Quarenta e oito horas após a exposição ao corante, os ratos foram perfundidos com solução de paraformaldeído e o segmento medular entre L3 e S1 foi removido e cortado em fatias de 40 micrômetros de espessura. RESULTADOS E CONCLUSÃO: os resultados da contagem neuronal mostraram maior quantidade de neurônios no lado onde foi colocado FGF em relação ao lado onde foram colocados fragmentos nervosos, demonstrando que o fator de crescimento de fibroblastos é superior a fragmentos de nervos na estimulação da regeneração nervosa quando colocados no tubo de silicone.

Peripheral nerve regeneration through guidance tubes

Biological nerve grafts have been extensively utilized in the past to repair peripheral nerve injuries. More recently, the use of synthetic guidance tubes in repairing these injuries has gained in popularity. This review focuses on artificial conduits, nerve regeneration through them, and an account of various synthetic materials that comprise these tubes in experimental animal and clinical trials. It also lists and describes several biomaterial considerations one should regard when designing, developing, and manufacturing potential guidance channel candidates. In the future, it it likely that the most successful synthetic nerve conduit will be one that has been fabricated with some of these strategies in mind.

The use of a muscle graft to repair a segmentary nerve defect

The use of a devitalized skeletal muscle graft and conventional nerve graft to repair a 5mm long segmentary sciatic nerve lesion was studied in rats by means of functional, morphometric and spinal cord motor neuron cell response evaluation. Thirty-four rats were used and divided into four groups according to the procedure: (1) sham operation; (2) conventional nerve grafting; (3) muscle grafting; (4) unrepaired lesion. The sciatic functional index (SFI) was evaluated every fortnight up to the 105th postoperative day by measuring three parameters in the rats' footprint. The animals of Groups 2 and 3 presented initial complete functional loss, followed by slow but steady recovery, with final similar SFIs. The histologic and morphometric studies showed an increased small diameter/thin myelin sheath nerve fiber density distally to the lesion site for both types of graft. An increased population of motor neurons was observed in the anterior horn of the lumbar spinal cord segment with both types of grafts, but not in the control groups. The SFI, histologic and morphometric data did not differ significantly between the two types of graft, thus indicating a similar behavior. The authors conclude that a 5mm long skeletal muscle graft works as well as a conventional nerve graft.