Tissue engineering of ligament and tendon healing

Ligaments and tendons are bands of dense connective tissue that mediate nor mal joint movement and stability. Injury to these structures may result in significant joint dysfunction because they either heal by production of inf erior matrix or do not heal at all. The process of ligament and tendon heal ing is complex and the roles of cellular and biochemical mediators continue to be elucidated, The expression of growth factors and growth factor recep tors is modulated after injury, and cells from healing tissues are responsi ve to growth factors. Tissue engineering offers the potential to improve th e quality of ligaments and tendons during the healing process. The concept is based on the manipulation of cellular and biochemical mediators to affec t protein synthesis and improve tissue remodeling. Recently, novel techniqu es such as application of growth factors, gene transfer techniques, and cel l therapy have shown promise and may become effective biologic therapies in the future. Many groups have been successful in introducing marker and the rapeutic genes into ligaments and tendons. Cell therapy involves the introd uction of mesenchymal progenitor cells as a pluripotent cell source into th e healing environment. The combination of cell therapy with growth factor a pplication via gene transfer offers new avenues to improve ligament and ten don healing.