Investigation of myelination in vitro: polar lipid content and fatty acid composition of myelinating oligodendrocytes in rat oligodendrocyte cultures.

Oligodendrocytes (OL) from newborn rat brain grown in culture according to Besnard et al. (Neurosci. Lett.73, 287-292, 1987) were characterized with a polyclonal anti-2?,3?-cyclic nucleotide-3?-phosphodiesterase antibody; ultrastructural study demonstrated the production of "myelin". These cultures contain 90% OL of which 7% were proliferating. Compared to rodent myelin, the cultured OL had about the same phospholipid/sulfatide ratio and phosphatidylethanolamine was also the major phospholipid but the percentage of long-chain hydroxy fatty acid cerebrosides was about 20% less and that of sulfatides 3% greater. Their fatty acid (FA) composition revealed some unusual features compared to bulk isolated OL. In the total lipid extract 77% of FAs were unsaturated with a high proportion of monounsaturated FAs (51%). The n-3/n-6 ratio was low (0.51), especially when compared to cultured astrocytes (n-3/n-6=0.80). Myelination was observable in these cultures by electron microscopy but the FA composition of OL differed from that reported in vivo and their 24:0 content was low (0.7%). In addition to the possibility that bulk isolation procedures may alter the biochemical composition of cells, (especially by loss of cell processes) culture conditions probably also interfere with the lipid composition of OL. In this respect the FA pattern observed and its possible consequences on the fluidity of the cell membrane should be kept in mind when the response of OL to external factors is analyzed.