Orthopaedic applications of gene therapy.

Current treatment modalities for musculoskeletal injuries due to disease or trauma often implement the use of tissue grafts, cell transplantations, and artificial scaffolding. These approaches may be augmented with the use of specific biological factors, which accelerate healthy tissue regeneration. Unfortunately, the short half-life and inherent instability of proteins requires the delivery of high doses or multiple doses of these molecules, neither of which is ideal for the patient or clinician. Gene therapy, as an alternative approach, has the potential to circumvent the existing limitations associated with protein delivery by producing a sustained release of the biologic agent at therapeutic levels. This is achieved by the direct transfer of the gene encoding the therapeutic agent to the cells of the afflicted tissue or by implanting cells that have been previously genetically modified in vitro. Using these methods, several laboratories have demonstrated the ability to deliver genes in vitro and in vivo resulting in accelerated and enhanced musculoskeletal tissue regeneration or inhibited disease progression. Many of these investigations, which involved bone, ligament, tendon, and cartilage, are covered in this review. Specifically, musculoskeletal tissue anatomy, factors relevant to musculoskeletal tissue regeneration, target cells, and in vivo and ex vivo gene therapy approaches for musculoskeletal regeneration are discussed. The experience and knowledge gained from these studies have affirmed gene therapy is a promising therapeutic strategy to combat musculoskeletal tissue repair and regeneration following disease or injury.