Mesenchymal stem cells in connective tissue engineering and regenerative medicine: applications in cartilage repair and osteoarthritis therapy.

Defects of load-bearing connective tissues such as articular cartilage, often result from trauma, degenerative or age-related disease. Osteoarthritis (OA) presents a major clinical challenge to clinicians due to the limited inherent repair capacity of articular cartilage. Articular cartilage defects are increasingly common among the elderly population causing pain, reduced joint function and significant disability among affected patients. The poor capacity for self-repair of chondral defects has resulted in the development of a large variety of treatment approaches including Autologous Chondrocyte Transplantation (ACT), microfracture and mosaicplasty methods. In ACT, a cartilage biopsy is taken from the patient and articular chondrocytes are isolated. The cells are then expanded after several passages in vitro and used to fill the cartilage defect. Since its introduction, ACT has become a widely applied surgical method with good to excellent clinical outcomes. More recently, classical ACT has been combined with tissue engineering and implantable scaffolds for improved results. However, there are still major problems associated with the ACT technique which relate mainly to chondrocyte de-differentiation during the expansion phase in monolayer culture and the poor integration of the implants into the surrounding cartilage tissue. Novel approaches using mesenchymal stem cells (MSCs) as an alternative cell source to patient derived chondrocytes are currently on trial. MSCs have shown significant potential for chondrogenesis in animal models. This review article discusses the potential of MSCs in tissue engineering and regenerative medicine and highlights their potential for cartilage repair and cell-based therapies for osteoarthritis and a range of related osteoarticular disorders.