Figure 1. Macrophages contribute to peripheral nerve regeneration.
(A) Macrophages at the dorsal root ganglia release neurotrophic factors such as leukemia inhibitor factor (LIF) that stimulate axonal outgrowth. (B) Macrophages at the distal end target contribute to synapse formation and neurotransmitter regulation. (C-H) Macrophages at the injury site (C) clear myelin fragments and cellular debris, (D) regulate extracellular matrix (ECM) organization through secreting tissue inhibitors of metalloproteinase (TIMPs), (E) stimulate angiogenesis through secretion of vascular endothelial growth factor (VEGF), (F) recruit Schwann cells with chemokine ligand 3 (CCL3), (G) induce Schwann cell maturation through growth arrest specific 6 (GAS6), and (H) prevent ectopic growth with slit homolog 3 protein (Slit3) expression.