Fresh osteochondral allografts have been proven clinically effective. However, the logistics of getting fresh, viable cartilage from donor to recipient requires the development of tissue banking methods. Conventional cryopreserved osteochondral grafts perform poorly in vivo and it is well established, in other tissue systems, that conventional cryopreservation often results in potentially damaging ice formation, both in the cells and in the surrounding extracellular matrix. In Phase I, we performed feasibility testing of an alternative ice-free cryopreservation method known as vitrification in a rabbit model. Fresh, conventionally cryopreserved, and vitrified specimens were compared. The results demonstrated 80-85 percent cell viability in vitrified specimens and similar performance of fresh and vitrified cartilage in vivo. In contrast, frozen cryopreserved specimens had low cell viability, correlating with the distribution of ice, and poor performance in vivo. In this Phase II proposal, testing of vitrification as a storage method for articular cartilage transplants is extended to a longer duration large animal study. In addition, several new methods of vitrification with better ice control will be screened in vitro and the two most effective methods will be tested in a large animal model in year 2. In Phase III, these studies will be extended to include human cartilage and tissue-engineered constructs.
Cryopreservation by vitrification may enable the storage and delivery of viable, functioning articular cartilage grafts, both allografts and tissue-engineered constructs, to the clinical market place. The U.S. market for cartilage repair products is predicted to exceed 90,000 units and $248 million in the near future.
