Peripheral Nervous System: Regenerative Therapies

Abstract

There is a general belief that regeneration in the Peripheral Nervous System (PNS) is a successful event, however complete functional regeneration is seldom achieved in patients that have suffered a nerve traumatic injury. In fact, what is clinically observed is that these patients live with permanent disabilities that interfere negatively in their daily routine activities. In injuries where there is tissue loss a direct neurorraphy is not possible without causing nerve tension and, therefore, another repair technique is needed. Clinically, these lesions are repaired by nerve autograft, a technique that requires a second surgery to harvest a segment of a donor nerve, a disadvantage of the method. Also, the area covered by the donor nerve becomes denervated and its function is lost. Other techniques that are used by surgeons when the proximal stump is not available are end-to-side coaptation and nerve transfer. Experimental studies aiming at developing alternative strategies that can improve nerve regeneration have increased over the last decades. Particularly, the search for nerve guiding conduits that can be used to bridge the nerve defect has received much attention by researchers all over the world. These conduits can be made by either synthetic or biological materials, but ideally, they should be biodegradable and biocompatible, have adequate permeability so as to allow the entrance of nutrients into the tube lumen and yet avoid the passage of cells that can interfere negatively in the regeneration processes, such as fibroblasts and inflammatory cells. Other therapeutic strategies such as gene, cell and molecular therapies as well as physical therapies (exercise, electrical and LASER therapy) have also been tested in experimental studies with positive results. In this chapter we review the literature covering all these strategies in terms of experimental studies and existing clinical trials.