Mesenchymal stem cells and infectious diseases: Smarter than drugs.

After bone marrow stromal cells (BMSCs also known as mesenchymal stem cells of bone marrow origin) were used successfully to treat graft versus host disease in a single human subject [1], many investigators studied the immune-suppressive properties of BMSCs and later adipose tissue derived MSCs (AMSC). The field has expanded significantly and there are many ongoing clinical trials that are trying to exploit the amazing abilities of MSCs from many tissues to regulate the immune system. In addition to "supervising" cells of the innate immune system, MSCs have also been shown to have anti-microbial properties. They appear to make molecules with direct effects on bacteria. Many questions about MSCs remain, however. We still need to determine how to isolate subpopulations of cells with specific immunomodulatory or antibacterial actions from the heterogeneous pool of cultured BMSCs. We need to find ways to prime cells to improve their immune regulatory activities, and while we have some ideas about mechanisms that underlie MSC/immune cell interactions, there is still much to discover before we can take full advantage of the regulatory abilities of MSCs to treat human diseases.