N-acetyl-cysteine-fortified PMMA resin improves viability and restores function of fibroblasts

Although poly-methyl methacrylate (PMMA) is used in many applications in dentistry, adverse effects of PMMA at cell/tissue levels have been constantly reported. Genetic damage and oxidative stress are suggested as mechanisms underlying the adverse effects of PMMA. The use of oxidant scavengers, such as N-acetyl cysteine (NAC), may detoxify the resin and prevent cellular damage and death. Objectives: The study examines the cytotoxicity of PMMA resin to oral fibroblasts and the potential detoxification and restoration of fibroblastic function by NAC. Methods: Oral fibroblasts extracted from rat palatal tissue were cultured on the resin material with or without NAC addition. Cell viability on different cultures was evaluated via flow cytometric analysis. Cell proliferation was examined by cell count. Gene expression was analyzed via a reverse transcriptase-polymerize chain reaction. Sirius red-based stain assay was employed to examine collagen deposition. Results: Twenty-four hours after incubation, less than 2% of the cells were viable on the untreated resin, while up to 35% of the cells were viable on the NAC-added resin. At culture days 2 and 5, cells counts were consistently higher on the NAC-added resin cultures compared to that of the untreated culture. The expression of collagen I and III was downregulated on the untreated resin culture, while 0.6% NAC-added resin culture restored the expression to a level similar to that of polystyrene culture. At day 7 of culture, the amount of deposited collagen was similar among different NAC-added resin cultures and 3 times greater than that of untreated resin culture (p<0.0001). Conclusions: The data demonstrated the high cytotoxicity of PMMA resin and that the addition of NAC significantly ameliorated the cytotoxicity to oral fibroblasts and restored their function to a biologically significant level. The potential usefulness of NAC in exploring biocompatible PMMA-based resin materials can be considered for future developments.