Mesenchymal Stem Cells and Immunomodulation: Implications in Bone Tissue Engineering

Abstract

Each year, millions of fractures occur all over the world, anda significant number of them carry the risk of failing to heal, resulting in delayed or non-union, requiring therapeutic intervention. Early immune response and inflammation after fractures plays an important role in the healing process; however, it has been shown that the prolonged inflammatory response is an inhibitory process in fracture repair. The exact mechanisms of inflammatory cells and their cytokines on fracture healing remains unclear. Some of the inflammatory mediators have been reported as encouraging factors in new bone formation, while others inhibit bone healing. From the past, stem cell therapy has always been an attractive option in bone tissue engineering for augmenting the fracture repair process. MSCs, as pluripotent stem cells, not only differentiate into pre-ostoblastic cells to form new bone, but they also apply immunomodulatory effects via a variety of mechanisms. This paper reviewsthe effects of immune cells and their cytokines on bone healing process and also discusses the most important modulatory mechanisms of MSCs on immune cells involved in bone tissue engineering.