CAFFEINE DECREASES GLIAL-CELL NUMBER AND INCREASES HYALURONAN SECRETION IN NEWBORN RAT-BRAIN CULTURES

Newborn rat brain astrocytes (type 1 astrocytes, O-2A progenitor cells , and O-2A progenitor-derived cells, i.e. oligodendrocytes and type 2 astrocytes) were cultivated to investigate the effect of addition of c affeine to the culture medium on glial cell development and secretion of hyaluronan (hyaluronic acid, HA). HA is a glycosaminoglycan, secret ed by type 1 astrocytes especially, which is a major component of the extracellular matrix of immature brain involved in morphogenesis and d ifferentiation. Caffeine was added to the culture medium of primary gl ial cell cultures at concentrations of 102 muM (20 mg/L) or 255 muM (5 0 mg/L), considered therapeutic and toxic levels, respectively, in hum an newborns. HA was measured in the culture medium by immunoenzyme ass ay using sheep brain hyaluronectin, a glycoprotein that exhibits a str ong affinity for HA, as probe. In primary glial cell cultures, 102 muM (20 mg/L) caffeine had no visible effect on cell number or on HA secr etion. At 255 muM (50 mg/L), there was a significant reduction of cell number (i.e. type 1 astrocytes, 0-2A progenitor cells, and progenitor -derived cells) and a significant increase of HA secretion per cell. T hese results suggest that caffeine at a high concentration in brain co uld have a prejudicial effect on the number of proliferating glial cel ls (astrocytes and oligodendrocytes) and on the composition of the ext racellular matrix, which could affect myelination onset.