Gingival fibroblast cells (rGF) from aged rats have an age-related decline in proliferative capacity compared with young rats. We investigated G1 phase cell cycle regulation and MMP-9 expression in both young and aged rGF. G1 cell cycle protein levels and activity were significantly reduced in response to interleukin-1 beta (IL-1 beta) stimulation with increasing in vitro age. Tumor necrosis factor-alpha (TNF-alpha)-induced matrix metalloproteinase-9 (MMP-9) expression was also decreased in aged rGF in comparison with young rGF. Mutational analysis and gel shift assays demonstrated that the lower MMP-9 expression ill aged rGF is associated with lower activities of transcription factors NF-kappa B and AP-1. These results Suggest that cell cycle dysregulation and down-regulation of MMP-9 expression in rGF may play a role in gingival remodeling during in vitro aging. (C) 2008 Published by Elsevier Inc.