Cathepsin K is important for the brain, because its deficiency in mice is associated with a marked decrease in differentiated astrocytes and changes in neuronal patterning in the hippocampus as well as with learning and memory deficits. As cathepsin K activity is most prominent in hippocampal regions of wild type animals, we hypothesised alterations in astrocyte-mediated support of neurons as a potential mechanism underlying the impaired brain functions in cathepsin K-deficient mice. To address this hypothesis, we have generated and characterised astroglia-rich primary cell cultures from cathepsin K-deficient and wild type mice and compared these cultures for possible changes in metabolic support functions and cell composition. Interestingly, cells expressing the oligodendrocytic markers myelin-associated glycoprotein and myelin basic protein were more frequent in astroglia-rich cultures from cathepsin K-deficient mice. However, cell cultures from both genotypes were morphologically comparable and similar with respect to glucose metabolism. In addition, specific glutathione content, glutathione export and γ-glutamyl-transpeptidase activity remained unchanged, whereas the specific activities of glutathione reductase and glutathione-S-transferase were increased by around 50% in cathepsin K-deficient cultures. Thus, lack of cathepsin K in astroglia-rich cultures appears not to affect metabolic supply functions of astrocytes but to facilitate the maturation of oligodendrocytes.