Control of oral fibroblast growth and function by N-acetyl cysteine

Prosthodontic and pre-prosthodontic treatments often require the management of unfavorable mucosal tissue response, including denture fibromatosis, hypertrophic gingiva around tissue bars, and fibrous migration into extraction or defect sites that prevent bone regeneration. Such hyper-fibrogenesis is closely linked to the production of oxidative stress. N-Acetyl-L-cysteine (NAC) is a cysteine derivative and known as an antioxidant molecule that provides antioxidant precursors and directly serves an oxidant scavenger. Objectives: This study tested a hypothesis that NAC controls growth and function of oral fibroblasts. Methods: Fibroblasts harvested from the rat palatal tissue were cultured with NAC in various concentration; 2.5mM, 5mM and 10mM. To simulate an inflammatory condition, oxidative stress was given by treating cultures with 10mM H2O2. The viability and proliferation of the cells were evaluated by annexin V-based flow cytometry and BrdU incorporation, respectively. The function of the fibroblasts was evaluated by Sirius Red staining for collagen production and by RT-PCR for gene expression. Potential usefulness of NAC was also tested by delivering NAC via collagen materials in membrane and sponge forms. Results: Proliferation activity of the oral fibroblasts was significantly reduced by the addition of NAC into the culture NAC-concentration dependently (p<0.001, ANOVA). The NAC addition downregulated the fibroblastic gene expression, such as collagen I and III, and reduced the collagen production at protein level. The NAC treatment did not produce apoptotic or necrotic cells. The H2O2-induced inflammatory reaction, as represented by increased fibroblastic proliferation and collagen production, was abrogated by the co-treatment with NAC. The cells cultured on the NAC-containing collagen materials showed lower cellular proliferation.

Conclusion: NAC inhibits the proliferation and function of oral fibroblasts without showing any cytotoxic effect. The inhibitory effect was also demonstrated to abrogate oxidative stress-induced hyper-growth and -function of the fibroblasts, suggesting the potential therapeutic value of NAC as an antifibrogenesis agent.