Figure 12.

A schematic diagram of our model for the neuron–macrophage interactions in conditioning injury-induced enhanced regenerative capacity of DRG sensory neurons. A, A simplified illustration of the major players in a resting state. B, Preconditioning peripheral nerve injury or cAMP injection, either of which supports activation of regeneration-associated genes, stimulates neurons to produce molecules to attract and activate macrophages. C, Activated macrophages produce various molecular factors that enhance regenerative capacity of DRG neurons. Our in vitro experiments suggest that oncomodulin may constitute the major proregenerative activity derived from macrophages, but the possibility remains that more molecules, such as neurotrophic factors, are also involved.