Abstract: Objectives: Previously, it was found that the para-nonylphenol (p-NP) impairs the osteogenic differentiation of rat bone marrow mesenchymal stem cells (rBMSCs); thus the aim of the present study was to evaluate the mechanism of the impairment. Methods: rBMSCs after 3rd passage cultured in osteogenic media in the presence of 0, 0.5 and 2.5 μM p-NP for 5, 10, 15 and 20 days. The study investigated the viability of the cells using MTT assays. The mineralization was studied using Alizarin red quantification analysis. Using a flame-photometer, the electrolytes (sodium and potassium) were measured, and the level of calcium as well as ALT, AST, ALP and LDH was determined by commercial kits. The level of total-antioxidant, MDA and the activity of SOD and CAT were estimated with the help of a spectrophotometer. Gene expression was studied using rt-PCR. Results: The p-NP treatment of osteogenic differentiated MSCs showed intracellular electrolyte imbalance and variation of cellular metabolism. In addition, we observed oxidative stress due to the reduction of total antioxidant capacity and the imbalance of antioxidant enzymes activity. Investigating the genes involved in the osteogenic differentiation of MSCs to osteoblast showed that the 2.5 μM of p-NP reduced the expression of the ALP, SMAD, BMP and RUNX2 genes. Conclusion: The study concludes that this pollutant via influencing the genomics and metabolic imbalance, as well as oxidative induction, caused a reduction of mineralization and differentiation of MSCs. This environmental pollutant might cause osteoporosis, which necessitates raising public awareness, especially to those who live in the industrial area to prevent its drastic effect.
