In a study published in Cell Stem Cell, researchers helped to clarify the mechanism by which mesenchymal stem cells achieve their immunosuppressive effects. While immunosuppression is not always appealing, there are certain contexts in which suppressing the immune system is critical. These cases include patients with autoimmune disease, where their immune system begins attacking the body’s organs, as well as skin grafts, where the immune system’s reaction to new skin often leads to graft rejection.
Mesenchymal stem cells have been strategically chosen over other types of stem cells when their immunosuppressive properties are beneficial. Nonetheless, because the specific reasons that these cells lead to immunosuppression are unknown, researchers have begun to investigate potential ways that the immunosuppression occurs.
One critical factor that the researchers considered was that the immunosuppressive effects of mesenchymal stem cells may not be innate. Given that immunosuppression is not always observed when mesenchymal stem cells are employed, the researchers hypothesized that the immunosuppression may depend on the presence of other factors in combination with mesenchymal stem cells.
Nitric oxide was one factor of particular interest to the researchers because nitric oxide is known to suppress the immune system’s T cells. Nitric oxide easily diffuses across barriers and interacts with a number of important proteins, making it an attractive candidate for contributing to immunosuppression that is observed with the use of mesenchymal stem cells.
Consistent with their hypothesis, the researchers found that nitric oxide does mediate the immunosuppression achieved by mesenchymal stem cells and demonstrated a specific mechanism by which this mediation occurs. This new information improves our understanding of how mesenchymal stem cells work and will therefore also enhance our ability to strategically use these cells to achieve the therapeutic benefits for which we strive.