Cell viability and protein composition in cryopreserved cartilage

Chondrocyte survival in frozen-stored osteochondral allografts is low. We analyzed different storage conditions to determine the best for maintenance or storage for preserving cartilage. We hypothesized cell viability and extracellular protein content could be improved with better cryopreservation. Articular cartilage from nine sheep femoral condyles were stored at 4 degrees C, -80 degrees C, and -196 degrees C with and without cryopreservative agents for 1 month. We determined cell viability and performed Western blot analysis for TGF-beta, IGF-I, and MMP-2, 9, and 13. We observed decreases in viability in cartilage stored at 4 degrees C: 36.2% viability when stored without solution, 40.4% in phosphate-buffered saline, and 48.1% in culture medium. TGF-beta and IGF-1 decreased in the first week in all groups. The groups stored at -80 degrees C and -196 degrees C contained less protease in the last 2 weeks. In the groups stored at 4 degrees C in phosphate-buffered saline, we detected no increase in the levels of MMPs. Our data discourage the use of frozen cartilage because of the decrease of cell viability and elevation in MMPs. However, modifying the freezing conditions might moderate these changes and improve the state of preserved cartilage.