Bone Marrow-derived Stem Cells for Tendon and Ligament Injuries

Introduction
Regenerative medicine offers the prospect of restoring normal, or as close to normal, structure and function to an injured organ and thereby resulting in a successful restoration of activity without the risk of re-injury. Over-strain and traumatic tendon and ligament injuries are common in the horse and, for the most part, heal (repair) naturally by the formation of scar tissue. However, the scar tissue formed in this repair is functionally deficient compared to normal tendon, which has important consequences for the animal in terms of reduced performance and a substantial risk of re-injury, in spite of a multitude of treatments that have been proposed. As pain is not usually a feature of these conditions in the long-term, the primary need is to restore functionality and so this has encouraged the development of regenerative strategies.

Mesenchymal progenitor cells (MPCs) have been considered an ideal source of cells for regenerative medicine because it can be demonstrated, in horses as in other species, that they are capable of differentiating into different cell lines and synthesise new matrix (usually chondrogenesis, adipogenesis and osteogenesis). These cells are thought to be present in small numbers in most tissues but we have chosen to harness the action of MPCs recovered from bone marrow because of ease of recovery, minimal donor site morbidity, and, as these stem cells can be recovered from adult tissue, the possibility of autologous re-implantation which carries fewer regulatory and safety issues. Furthermore, in comparative experiments assessing multipotency, bone marrow-derived MPCs tend to out-perform MPCs from other sources. [...]