EVALUATION OF TOLL-LIKE RECEPTORS (TLRS) AGONISTS-TREATED MOUSE BONE MARROW-DERIVED MESENCHYMAL STEM CELLS AND THEIR CULTURE SUPERNATANT ON NK CELLS’ ACTIVITY AGAINST YAC-1 CELLS

Mesenchymal stem cells (MSCs) are multipotent, non-hematopoietic precursor cells that can be found in many adult tissues. The multipotency and immunomodulatory potential of MSCs make these cells a remarkable tool for the treatment of some diseases. It seems that stimulation of toll-like receptors expressed on the surface of mesenchymal stem cells may potentiate the immunomodulatory potential of these cells. This study was conducted to investigate the effects of polarized bone marrow-derived mesenchymal stem cells from mice on the cytotoxic activity of natural killer (NK) cells.

MSCs were isolated from the bone marrow of the femur and tibia of NMRI mice. The third passage of cells was treated with LPS and Poly I-C, then the effects of polarized MSCs, as well as their culture supernatant, on the cytotoxic activity of NK cells against lymphoid cancer cells Yac-1 (as target cells), were evaluated using flow cytometry after 12, 24, and 72 hours.

MSCs treated with LPS and Poly I-C, and their respective culture supernatants, decreased the percentage of dead cells (necrosis and apoptosis) (38% and 35% respectively) compared to untreated MSCs (44%). In the case of cell viability, this effect was the opposite; that is, the untreated cells showed higher viability.

Previous studies indicated that MSCs inhibit the expansion and cytotoxicity of NK cells on tumor cells; however, our results revealed that MSCs treated with LPS potentiated the inhibitory effects of MSCs on NK cell activity.