Inflammatory Profiling of Schwann Cells in Contact with Growing Axons Distal to Nerve Injury

Activated Schwann cells distal to nerve injury upregulate inflammatory mediators, including cytokines. The goal of the present study was to investigate expression of proinflammatory (IL-1β, TNFα) and anti-inflammatory cytokines (IL-4, IL-10) in activated Schwann cells in relation to growing axons distal to crush injury of rat sciatic nerves. Seven days from sciatic nerve crush, transverse cryostat sections were cut 5 mm distal to lesion and incubated for double immunostaining to indicate Schwann cells (GFAP or S100b) and individual investigated cytokines or to demonstrate growing axons (GAP43). The Schwann cells of naïve sciatic nerves and those removed from sham-operated rats displayed similar weak immunoreactivity for the investigated cytokines. In contrast, increased intensity of cytokine immunofluorescence was found in Schwann cells distal to crush lesion. The cytokine-positive Schwann cells were found in close contact with growing axons detected by immunostaining for GAP43. The results of immunohistochemical analysis distal to nerve crush injury suggest that inflammatory profiling of Schwann cells including upregulation of both pro- and anti-inflammatory cytokines does not prevent growth of axons distal to nerve crush injury.