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. We propose feasibility testing of an alternative ice-free cryopreservation method known as vitrification. Distal osteochondral plugs will be procured from rabbits. Fresh, conventionally cryopreserved, and vitrified specimens will be compared in vitro using quantitative cell viability, biochemical, mechanical and histology methods. The use of cryosubstitution methods to determine the location of ice in conventionally cryopreserved cartilage may help explain the poor viability of chondrocytes (0-20%) reported in the literature. Modifications to the vitrification protocol will be attempted until chondrocyte viability is optimized. Conventionally cryopreserved and vitrified allografts will be compared six weeks post-transplantation using the same quantitative parameters. If vitrified specimens perform similarly to fresh cartilage, this research will be further developed in a Phase II proposal. Phase II will extend this feasibility study to a large animal, preclinical allogeneic model and will include assessment using 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.
| Brockbank, Kelvin G M; Chen, Zhen Z; Song, Ying C (2010) Vitrification of porcine articular cartilage. Cryobiology 60:217-21 |
