Prion protein gene expression in cultured astrocytes treated by recombinant growth hormone and insulin-like growth factor.

Cases of Creutzfeldt-Jakob disease recently occurred after long treatments with pituitary extracted human growth hormone (GH). Prion protein (PrP) and glial fibrillary acidic protein (GFAP), an astrocyte-specific marker, both accumulate in the central nervous systems of infected individuals during transmissible subacute spongiform encephalopathies (TSSE). PrP expression has been linked to susceptibility to and development of these diseases. We have investigated the effects of recombinant growth hormone, its main biological effector, insulin-like growth factor 1 (IGF-1), and two well known mitogens, epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF), on PrP and GFAP mRNA levels in primary cultures of murine astrocytes using Northern blot quantitation. After 48 h of exposure to these soluble factors, PrP mRNA levels remained unchanged relative to controls in all growth factor-treated cultures, whereas GFAP mRNA concentrations decreased markedly in EGF- and bFGF-treated cultures. These results suggest that GH and IGF-1 do not modulate PrP gene expression in astrocytes.