The significance of M1 macrophage should be highlighted in peripheral nerve regeneration.

Macrophage influences peripheral nerve regeneration. According to the classical M1/M2 paradigm, the M1 macrophage is an inhibitor of regeneration, while the M2 macrophage is a promoter. However, several studies have shown that M1 macrophages are indispensable for peripheral nerve repair and facilitate many critical processes in axonal regeneration. In this review, we summarized the information on macrophage polarization and focused on the activities of M1 macrophages in regeneration. We also provided some examples where the macrophage phenotypes were regulated to help regeneration. We argued that the coordination of both macrophage phenotypes might be effective in peripheral nerve repair, and a more comprehensive view of macrophages might contribute to macrophage-based immunomodulatory therapies.