miR-21 negatively regulates stemness-related properties of granulation tissue-derived cells via a reactive oxygen species-dependent pathway. N-acetyl cysteine (NAC; 5 mM) was added into culture medium and adipogenic and osteogenic induced medium of granulation tissue-derived cells (GTCs) to scavenge the intracellular reactive oxygen species (ROS). (A) Proliferation of GTCs with and without NAC was measured every 2 days after seeding. Colony formation assay including (B) colony numbers, (C) average colony sizes and (D) colony size distribution of GTCs with and without NAC was present. (E) Representative migration photographs of GTCs with and without NAC at indicated time points. (F) The migration rate of the two groups presented as mean ± standard deviation (n = 6 per time point for each group). (G) The quantification and representative photographs of the Oil-Red O staining of the adipogenic differentiation of GTCs with and without NAC. (H) Quantification and representative photographs of the Alizarin Red staining of the osteogenic differentiation of GTCs and GTCs with NAC. CFU, colony-forming units; d, days; h, hours, OD, optical density. *P <0.05; **P <0.01. Scale bar = 500 μm.