Morphological analysis of Wallerian degeneration in the rat sciatic nerve following mechanical damage

Abstract

Introduction. Peripheral nerve injury is an important social problem. Fundamental research on mechanisms regulating degenerative and reparative processes that occur in the nerve following injury is necessary to find new ways of improving nerve regeneration. The purpose was to study the structural changes in the distal segment of the rat sciatic nerve at early stages following injury (ligature) using immunohistochemical and histochemical methods. Materials and methods. The rat sciatic nerve was subjected to mechanical trauma through ligation for a duration of 40 seconds. After days 7, 21, and 60, we analyzed changes in the nerve fibers using immunohistochemical reactions for alpha-tubulin and Luxol Fast Blue stains for myelin. Antibodies to tight junction protein claudin-1 were used to study perineurial cells. We identified Schwann cells (neurolemmocytes) and macrophages with the reaction for GFAP and the Iba-1 protein IHC reaction, respectively. Results. After 7 days, we observed degeneration of most nerve fibers, disintegration of myelin sheaths, disruption of the blood-neural barrier, migration of hematogenous macrophages, and dedifferentiation of Schwann cells in the endoneurium of the rat sciatic nerve distal segment. However, after day 21, the growth of nerve fibers from the proximal segment of the nerve and their remyelination were observed. The density of nerve fibers reached its highest value 60 days after the injury. Conclusion. We evaluated the relationship between the degree of myelin breakdown and the number of Iba-1+ macrophages, detected changes in the perineurium in the distal segment of the nerve, and identified dedifferentiated mitotically dividing Schwann cells. Keywords: Wallerian degeneration, damaged rat nerve, Luxol Fast Blue, claudin-1, Iba-1 protein, GFAP, immunohistochemistry