Macrophage-enhanced neurite regeneration of adult dorsal root ganglia neurones in culture.

To study the effects of macrophages on nerve regeneration, purified low population dorsal root ganglia (DRG) neurones from adult mice were cultured in protein-free medium (PFM) or in conditioned media (CM) from peritoneal macrophages cultured in PFM. In PFM, only 20% of the neurones survived at 5 days in culture, but the macrophage CM more than doubled the proportion of neurone survival and neurite extension of controls. These factors did not act on superior cervical ganglia (SCG) neurones, and were considered as being proteins because of their trypsin-sensitive property. Additionally, they may be different from the previously known neurotrophic factors derived from macrophages, because the target cells and effective concentration of these factors were different from those of known ones. The factors investigated in this study may play an important role in nerve regeneration.