Intracellular sulfatide expression in a subpopulation of astrocytes in primary cultures

A highly specific antibody against sulfatide, a myelin-associated glycolipid, has been investigated using indirect double immunocytochemistry in rat primary astroglial cultures from cerebral cortex. Sulfatide was expressed in a selected subpopulation of astrocytes (2-3%) and was found to be exclusively located intracellularly. The sulfatide-positive cells appeared in two different morphologies: flat and stellate. Immunolabeling of the astroglial cultures showed that sulfatide always co-existed with GFAP or S-100, and in some cells with GD3 (flat 90% and stellate 50%) or A2B5 (1%) antibody. The sulfatide-positive cells did not bind the O1 antibody, which is used as a marker for oligodendrocytes. Glial cultures from other regions and mixed cultures, with both neurons and glial cells, were examined and showed similar results. Biochemical analysis by TLC-ELISA verified the presence of sulfatide in the astroglial culture and showed decreasing amounts of sulfatide with days in vitro; 0.05 nmol/mg protein at day 10 and 0.01 nmol/mg protein at day 17. This analysis also showed that neither sulpholactosylceramide nor seminolipid was present, each of which also has affinity for the sulfatide antibody. This selective and intracellular expression encourages further identification of the astrocytes expressing sulfatide and the biological role of sulfatide in these cells.