Mesenchymal stem cells: An efficient cell therapy for tendon repair (Review)

Tendon injury is a common disorder of the musculoskeletal system caused by overuse or trauma. With increasing incidence of tendon injuries, it is necessary to find an effective treatment. Mesenchymal stem cells (MSCs) are attracting attention because of their high proliferative and self-renewal capacity. These functions of MSCs show promise in treating a variety of diseases, including immune and musculoskeletal system disorder and cardiovascular disease, and show especially satisfactory effects in the treatment of tendon injury. First, since MSCs have multidirectional differentiation potential, they differentiate into specific cells after induction in vivo and in vitro. Furthermore, MSCs have paracrine functions and can secrete biologically active molecules and exosomes such as cytokines, growth factors and chemokines to promote tissue repair and regeneration. In tendon injury, MSCs promote tendon repair through four mechanisms: Decreasing inflammation and promoting neovascularization and cell proliferation and differentiation. They are also involved in extracellular matrix reorganization by promoting collagen production and transforming type III collagen fibers to type I collagen fibers. The present review summarized preclinical experiments with different sources of MSCs and their mechanisms in tendon repair, as well as the limitations of MSCs in current clinical applications and directions that need to be explored in the future.