Toll-Like Receptor Expression of Mesenchymal Stem Cells Derived from Granulocyte Colony-Stimulating Factor Treated Bone Marrow Donors

Objective: The present study was planned to examine the expression of Toll-like receptors on human marrow-derived mesenchymal stem cells as a result of in-vivo exposure to granulocyte colony-stimulating factor with or without exposure of the cells to Toll-like receptors agonists. Materials and Methods: Toll-like receptor 2, 3, and 4 expressions of mesenchymal stem cells obtained from healthy human bone marrow donors exposed to in-vivo granulocyte colony-stimulating factor were analyzed, and granulocyte colony-stimulating factor untreated donors served as controls. Also, mesenchymal stem cells were stimulated in-vitro by Toll-like receptor agonists to observe the changes in the expression of the Toll-like receptors. Results: Mesenchymal stem cells obtained from both granulocyte colony-stimulating factor exposed or unexposed donors showed a low level of Toll-like receptor 2, 4 expressions by flow cytometry, whereas Toll-like receptor 3 expression was higher. Lipopolysaccharide was used as an agonist, but no significant difference was observed in the Toll-like receptor 2, 4 expressions, both in the granulocyte colony-stimulating factor exposed and unexposed groups. Stimulation of cells with Tolllike receptor 3 ligand was associated with a statistically significant decrease in Toll-like receptor 3 expressions, which was more profound in granulocyte colony-stimulating factor unexposed cells. Conclusion: We have shown that human bone marrow-derived cultureexpanded mesenchymal stem cells express Toll-like receptor 3, whether in-vivo granulocyte colony-stimulating factor treated or untreated. Besides, the Toll-like receptor 3 agonist’s effect in lowering the expression levels was more significant in cells that were not exposed to granulocyte colony-stimulating factor. Additionally, detection of low expression of the pro-inflammatory Toll-like receptor 4 versus higher levels of Tolllike receptor 3 supports literature regarding the immunosuppressive characteristics of marrow-derived mesenchymal stem cells. Modulation of the expression of the Toll-like receptor of mesenchymal stem cells with granulocyte colony-stimulating factor or agonists may have implications in allogeneic mesenchymal stem cell therapies.