Glial culture on artificial capillaries: electron microscopic comparisons of C6 rat glioma cells and rat astroglia.

The functional association of astroglial footplates with blood vessels is important because astrocytes may provide a channel between the blood and neurons deeper in the brain parenchyma for the passage of ions and metabolites. This hypothesized function is very difficult to study in vivo or in monolayer cultures. We have produced a three-dimensional cell culture model of perivascular astroglia by means of an artificial capillary system. Conventional primary cultures of astroglia were first prepared from neonatal rat cerebral hemispheres in 75-cm2 tissue culture flasks. After 25 days, the cells were seeded in Amicon Vitafiber hollow fiber culture vessels. Direct seeding of brain cell suspensions was not successful. A culture unit consists of a bundle of hollow, semi-permeable polysulfone fibers encased in a plastic shell. The fibers were coated with fibronectin and bovine serum albumin, and astroglia were seeded on their outer surfaces. Warmed medium was pumped through the lumina of the fibers. After 13 days the cells were fixed with paraformaldehyde and examined. Scanning electron microscopy revealed the tubes to be uniformly covered with astroglia with short processes that contacted nearby cells. Transmission electron microscopy showed glial filaments and gap junctions. Astrocyte cultures were compared morphologically to C6 rat glioma cells in hollow fiber culture. The astrocytes formed a monolayer, whereas C6 cells formed a stratified culture. Furthermore, C6 cells did not form gap junctions. Astrocytes have been hypothesized to take up K+ discharged to the extracellular space by depolarizing neurons and move it to areas of low concentration, i.e., to act as a K+ spatial buffer. Our culture system should permit direct testing of this hypothesis.