Mesenchymal stem cells (MSCs) exist in almost all tissues and are crucial in maintaining the cellular homeostasis of multicellular organisms. They provide the ultimate cell source for tissue repair and regeneration. Under pathological conditions, these cells are awakened, activated, and mobilized to damaged tissue sites. Since tissue damages are often accompanied by inflammatory factors, from both innate immune response and adaptive immune response, it is sensible that MSCs delicately interact with inflammatory factors at the sites of tissue damages.
Depending on the type and persistence of the inflammatory factors, the activated MSCs could lead either to complete or partial tissue repair, or to chronic inflammation and further tissue damage, such as cancer and fibrosis. Indeed, recent studies have shown that there is a bidirectional interaction between MSCs and inflammatory cells and cytokines. However, much information of this information remains to be elucidated. Further investigations in this newly emerging exciting research area will undoubtedly lead to better understanding of pathogenesis of various diseases and novel treatment strategies.