Myelination requirements of central nervous system glia in vitro: statistical validation of differences between glia from adult and immature mice.

Glia from adult optic nerve, like those from immature nerve, have been shown to colonize and myelinate cerebellar axons in combined cultures. Preliminary experiments suggested, however, that the glia from adults might require the added nutrients and/or chemical signals present in a serum and embryo extract containing medium to produce myelin, whereas glia from immature animals could form myelin in a chemically defined medium described by Hendelman et al. (1985). This observation demanded rigorous confirmation, since it depended on the meaning of a negative result (the absence of myelin), which could be produced by many factors other than the composition of the medium in this complex culture system. Here we report an extensive series of experiments, with controls for all other factors, that provide unquestionable statistical validation of the additional myelination requirements of the glia from adult nerves. The cultures can now be used to identify these required substances, which may be limiting factors for central nervous system myelin regeneration in situ.