Chondrocyte Viability Is Higher After Prolonged Storage at 37°C Than at 4°C for Osteochondral Grafts

Background: Osteochondral allografts are currently stored at 4 degrees C for 2 to 6 weeks before implantation. At 4 degrees C, chondrocyte viability, especially in the superficial zone, deteriorates starting at 2 weeks. Alternative storage conditions could maintain chondrocyte viability beyond 2 weeks, and thereby facilitate increased graft availability and enhanced graft quality. Purpose: The objective of the study was to determine the effects of prolonged 37 degrees C storage compared with traditional 4 degrees C storage on chondrocyte viability and cartilage matrix content. Study Design: Controlled laboratory study. Methods: Osteochondral samples from humeral heads of adult goats were analyzed (i) fresh, or after storage in medium for (ii) 14 days at 4 degrees C including 10% fetal bovine serum, (iii) 28 days at 4 degrees C including 10% fetal bovine serum, (iv) 28 days at 37 degrees C without fetal bovine serum, (v) 28 days at 37 degrees C including 2% fetal bovine serum, or (vi) 28 days at 37 degrees C including 10% fetal bovine serum. Portions of samples were analyzed by microscopy after LIVE/DEAD staining to determine chondrocyte viability and density, both en face (to visualize the articular surface) and vertically (overall and in superficial, middle, and deep zones). The remaining cartilage was analyzed for sulfated glycosaminoglycan and collagen. Results: The 37 degrees C storage maintained high chondrocyte viability compared with 4 degrees C storage. Viability of samples after 28 days at 37 degrees C was similar to 80% at the cartilage surface en face, similar to 65% in the superficial zone, and similar to 70% in the middle zone, which was much higher than similar to 45%, similar to 20%, and similar to 35%, respectively, in 4 degrees C samples after 28 days, and slightly decreased from similar to 100%, similar to 85%, and similar to 95%, respectively, in fresh controls. Cartilage thickness, glycosaminoglycan content, and collagen content were maintained for 37 degrees C and 4 degrees C samples compared with fresh controls. Conclusion: The 37 degrees C storage of osteochondral grafts supports long-term chondrocyte viability, especially at the vulnerable surface and superficial zone of cartilage. Clinical Relevance: Storage of allografts at a physiologic temperature of 37 degrees C may prolong storage duration, improve graft availability, and improve treatment outcomes.