N-acetyl cysteine protects osteoblastic function from oxidative stress

Regenerative dentistry has become an inevitable treatment tool for prosthodontic therapy. Regenerative therapy mostly involves surgical procedure and host invasion by various biomaterials. It is unavoidable that a significant degree of oxidative stress is generated in the recipient site, that hinders and delays the healing process.

Objectives: This study tested the protective potential of an anti-oxidant, amino-acid derivative, N-acetyl cysteine (NAC) in controlling the oxidative stress against osteoblasts.

Methods: Osteoblastic cells were extracted from the rat bone marrow and cultured. Oxidative stress was given by adding the 100ìM H2O2 into the media. Some of the cultures were co-treated with H2O2 and NAC in a concentration of 2.5mM or 5mM. Cell proliferation was evaluated using hematocytometer. The osteoblastic phenotypes were assessed by alkaline-phosphatase (ALP) activity and reverse transcriptase-polymerase chain reaction for collagen, osteopontin and osteocalcin gene expressions. Mineralizing capability was assessed by Von Kossa stain.

Results: Adding H2O2 decreased the number of the cells to the levels of 32% and 5% of the untreated control group at culture days of 2 and 5, respectively (ANOVA, p<0.01). Both osteopontin and osteocalcin gene expressions were downregulated 9-fold by H2O2 at day 7. NAC addition into the H2O2 cultures, dose-dependently, increased the number of the cells, with the cell number at day 5 being 2.5 times for the NAC-co-treatment. The gene expression, reduced by H2O2, was fully recovered to the level equivalent to the untreated control culture. The ALP positive area measured at day 7 and Von Kossa positive area measured at day 14 were approximately 1.8 times greater for NAC+H2O2 co-treated group than for H2O2 group.

Conclusion: Oxidative stress-induced by H2O2 could be devastating for osteoblasts. However, more importantly, the addition of NAC into the osteoblastic culture restores their damaged proliferative and differentiation capacities to a near normal level.