Background: Osteochondral allografts (OCAs) are currently preserved at 4°C and used within 28 days of donor harvest. The window of opportunity for implantation is limited to 14 days due to a 2-week disease testing protocol.
Hypothesis: Osteochondral allograft tissues stored at 37°C will have significantly higher chondrocyte viability, as well as superior biochemical and biomechanical properties, than those stored at 4°C.
Study design: Controlled laboratory study.
Methods: Osteochondral allografts from 15 adult canine cadavers were aseptically harvested within 4 hours of death. Medial and lateral femoral condyles were stored in Media 1, similar to the current standard, or Media 2, an anti-inflammatory and chondrogenic media containing dexamethasone and transforming growth factor-β3, at 4°C or 37°C for up to 56 days. Chondrocyte viability, glycosaminoglycan (GAG) and collagen (hydroxyproline [HP]) content, biomechanical properties, and collagen II and aggrecan content were assessed at days 28 and 56. Five femoral condyles were stored overnight and assessed the next day to serve as controls.
Results: Storage in Media 1 at 37°C maintained chondrocyte viability at significantly higher levels than in any other media-temperature combination and at levels not significantly different from controls. Osteochondral allografts stored in either media at 4°C showed a significant decrease in chondrocyte viability throughout storage. Glycosaminoglycan and HP content were maintained through 56 days of storage in OCAs in Media 1 at 37°C. There were no significant differences in elastic or dynamic moduli among groups at day 56. Qualitative immunohistochemistry demonstrated the presence of collagen II and aggrecan throughout all layers of cartilage.
Conclusion: Osteochondral allograft viability, matrix content and composition, and biomechanical properties were maintained at "fresh" levels through 56 days of storage in Media 1 at 37°C. Osteochondral allografts stored at 4°C were unable to maintain viability or matrix integrity through 28 days of storage. These findings suggest that storage of OCAs in a defined media at 37°C is superior to current protocols (4°C) for tissue preservation prior to transplantation.
Clinical relevance: Storage of OCAs in serum-free chemically defined media at 37°C can increase the "window of opportunity" for implantation of optimal tissue from 14 days to 42 days after disease testing clearance.