Effect of predegenerated nerve grafts on axonal regeneration in the peripheral nervous system

ABSTRACT

This project has provided a general stereological survey for the study of the influence of the predegenerated nerve graft and prelesioned host site on axonal regeneration and remyelination in the peripheral nervous system. Right sciatic nerve of adult rats was sectioned at mid-thigh level, and the distal portion was allowed to predegenerate for 0, 6 and 12 days. The distal nerve segment [10-15 mm] was grafted onto the proximal nerve stump which had received a conditioning lesion 0, 6 or 12 days previously, resulting in different 9 donor-host combinations. The morphological study of the grafts was assessed 8 and/or 24 weeks after grafting. The number of regenerated remyelinated axons was counted by using a recent stereological technique. The grafts given eight weeks postgrafting had many regenerated myeflinated axons ranging from 11,000 to 28,000 axons, and the grafts given a 24 weeks postgrafting had large numbers of regenerated myelinated axons ranging from 15,000 to 29,000 axons. These results indicate that both a conditioning lesion of the host and the degree of predegeneration of the nerve graft are important in the influencing of the degree of axonal regeneration and remyelination. Six days post-lesion host is the best time which can enhance axonal regeneration before grafting. Using the retrograde tracer [Fast-Blue] for labeling the nerve cell bodies in DRG and anterior horn of the spinal cord at the levels of L[4] and L[5], the results showed there was no relationship between the number of regenerated axons and the number of the labeled nerve cells. Our results concluded the importance of neuronal vasculature in the process of axonal regeneration. Finally, we can fairly apply clinically the use of predegenerated nerve grafts and prelesioned host site in peripheral nerve repair following injury