Evidence that V+ fibronectin, GFAP, and S100ß mRNAs are increased in the hippocampus of aged rats

Abstract In the present study, using RNA gel-blot analysis, we characterized the developmental changes in the prevalence of mRNA coding for fibronectin (FN), glial fibrillary acidic protein (GFAP), neurotrophic protein S100s, and s-actin mRNA in rat hippocampus and forebrain from 1 to 720 days of age. We found that the FN and mRNA containing the V segment (FN-V) was relatively abundant at early postnatal stages, but very few transcripts were detected in adult rats. However, the hybridization signal for the juvenile FN-V mRNA was up to ∼ 8-fold increased in some but not all 24-versus 6-month-old rats. Also, GFAP and S100s transcripts were faintly expressed at an early developmental stage, then the level of expression steadily increased starting with day 21. The greatest increase averages ∼ 1.8-fold for GFAP in 24-month-old rats, and ∼1.5-fold for S100s in 15-month-old versus 6-month-old rats. As all these messages are localized primarily in astrocytes, we conclude that (a) astrocyte might play an active role in aging hippocampus and (b) an increase in S100s and GFAP mRNA expression may precede that for FN-V mRNA expression in a hypothetical pathway of molecular events underlying neurodegeneration in the hippocampus of old rats. We also note the considerable variability among the 24-month-old rats, suggesting that aging is an individual process.