Comparison of cytokine expression profile during Wallerian degeneration of myelinated and unmyelinated peripheral axons

Changes in cytokine and chemokine expression during Wallerian degeneration have been studied using nerve transection models, which result in denervation of both myelinating and non-myelinating Schwann cells. Cytokine and chemokine response of non-myelinating Remak Schwann cells to loss of their axons is unknown. In this study, we compared the expression profile of various cytokines and chemokines in distal nerves after capsaicin-induced degeneration of unmyelinated axons to Wallerian degeneration induced by nerve transection. Upregulation of MCP-1, IL-2, IL-6 and IL-10 were seen in both groups but IL-1ß and LIF were primarily upregulated in Wallerian degeneration of the whole nerve and not in capsaicin-induced degeneration of unmyelinated axons. The activated macrophage response, as measured by an increase in ED-1 immunostaining, was more prominent in the transected sciatic nerves compared to capsaicin-treated nerves. These findings indicate that there are differences in the cytokine and chemokine response of myelinating and non-myelinating Schwann cells to loss of their axons, and add to a growing body of literature that points to greater heterogeneity among Schwann cells.