Astroglial-Conditioned Media and Growth Factors Modulate Proliferation and Differentiation of Astrocytes in Primary Culture

Astroglial conditioned media (ACM) influence the development and maturation of cultured nerve cells and modulate neuron-glia interaction. To clarifymechanisms of astroglial cell proliferation/differentiationin culture, incorporation of [methyl-3H]-thymidine or [5,6-3H]-uridine in cultured astrocytes was assessed.Cultures were pre-treated with epidermal growth factor(EGF), insulin (INS), insulin-like growth factor-I (IGFI), and basic fibroblast growth factor (bFGF) andsubsequently with ACM. DNA labeling revealed a marked stimulatory effect of ACM from 15 days in vitro (DIV) cultures in 30 DIV astrocytes after 12h pre-treatment with growth factors. The main effects were found after INS or EGF pre-treatment in 30 DIVcultures. ACM collected from 15 or 60 or 90 DIV increased RNA labeling of 15 and 30 DIV astrocyte cultures, being the highest value that of 30 DIVcultures added with ACM from 90 DIV. The findings of increased DNA labeling after EGF or INS pretreatment in 30 DIV cultures, followed by addition of ACM from 15 DIV cultures, suggest that these phenomena may depend by extra cellular signal-regulated kinase 1 (ERK1) activation.