Lipid metabolism of isolated oligodendrocytes maintained in long-term culture mimics events associated with myelinogenesis.

Abstract

Oligodendrocytes isolated from ovine white matter according to a published procedure [Szuchet, S., Stefansson, K., Wollmann, R. L., Dawson, G. & Arnason, B. G. W. (1980) Brain Res. 200, 151-164] were cultured for up to 35 days and their capacity to incorporate precursors into lipids was investigated. At various times, cultures were double labeled with [3H]glycerol/[14C]acetate or [3H]galactose/35SO2-4. The cells were harvested 72 hr later and lipids were fractionated using standard procedures. The time course of incorporation for each precursor was distinct. In the days after attachment to substratum, oligodendrocytes preferentially incorporated [3H]glycerol into phospholipids and [14C]acetate into cholesterol while uptake of 35SO2-4 and [3H]galactose into glycolipids was modest. A switch in phospholipid metabolism from preferential incorporation into phosphatidylcholine to incorporation into phosphatidylethanolamine, phosphatidylserine, and phosphatidylinositol occurred at about the 10th day in vitro. After 20 days, uptake of [3H]glycerol into phospholipids and [14C]acetate into cholesterol had stabilized but incorporation of 35SO2-4 into glycolipids had increased. 35SO2-4 incorporation into glycolipids was even greater at 35 than at 20 days. Uptake of [3H]galactose did not change over time. An attempt was made to correlate changes in lipid metabolism with morphologic developments. High incorporation into phospholipids and cholesterol coincided in time with the extensive membrane synthesis required for cell attachment and process extension. Differentiation of these newly formed membranes, as assessed by the incorporation of myelin-characteristic glycolipids, galactocerebrosides, and sulfatides, occurred at a time when an intricate network of processes had already been established. The sequence of metabolic events observed in vitro parallels that observed at the onset of myelinogenesis in vivo. We postulate that mature oligodendrocytes can reenact those early events associated with myelinogenesis.