Stem-cell-driven regeneration of synovial joints.

Mammalian skeletal motion is made possible by synovial joints. Widespread suffering from arthritis and joint injuries has motivated recent effort to regenerate a stem-cell-driven synovial joint condyle implantable in total joint replacement. A single adult stem cell lineage, mesenchymal stem cells, differentiate to form all components of a synovial joint. Whereas localized joint lesions may be repaired by either cell-based or cell-free approaches, regeneration of the entire articular condyle of the synovial joint is unattainable without tissue-forming cells. A series of experiments are presented here to describe our initial attempts to regenerate a synovial joint condyle in the shape and dimensions of a human mandibular condyle, with both cartilaginous and osseous components derived from a single population of rat mesenchymal stem cells. Upcoming challenges are along several intertwining fronts including structural integrity, tissue maturation, mechanical strength and host integration. The synovial joint condyle may turn out to be one of the first 'human body parts' or organs truly regeneratable by stem-cell-derived approaches. Current approaches to regenerate the synovial joint condyle from stem-cell-derived multiple cell lineages may also offer clues for engineering complex organs such as the kidney or liver.