Use of stem cells in orthopaedics

Mesenchymal stem cells have for some time been gaining interest in the context of their potential applications in the treatment of musculoskeletal disorders. Mesenchymal stem cells (MSCs) are capable of differentiating into one of several mesenchymal phenotypes such as osteoblasts, chondrocytes, myocytes, marrow stromal cells, tendon–ligament fibroblasts and adipocytes [ 1– 4]. Due to the relative ease of obtaining and administering them, compared to the alternative surgical treatment (or in combination with surgical treatment), they offer an attractive therapeutic option, for both physicians and patients alike, and find an increasing range of applications in orthopaedics. According to the most recent thinking on mesenchymal stem cell physiology, these cells are actually pericytes, that is, perivascular cells which are activated in response to trauma or local inflammation, and act to repair the damage using various types of chemotactic factors [ 5]. These secreted bioactive factors suppress the local immune system, inhibit fibrosis (scar formation) and apoptosis, enhance angiogenesis and stimulate mitosis and differentiation of tissue-intrinsic reparative or stem cells [ 6]. It has been proposed that the pericyte is released from its position on a vascular tube in the case of a focal injury, and, as such, it functions as an immunomodulatory and trophic MSC [ 7]. MSC-induced immune modulation turns off T-cell supervision of the injured area and blocks autoimmunological reactions. Its trophic activity limits the field of damage so that scarring does not occur and that tissue-intrinsic progenitors replace the expired cells.