In vivo efficacy of fresh versus frozen osteochondral allografts in the goat at 6 months is associated with PRG4 secretion.

The long-term efficacy of osteochondral allografts is due to the presence of viable chondrocytes within graft cartilage. Chondrocytes in osteochondral allografts, especially those at the articular surface that normally produce the lubricant proteoglycan-4 (PRG4), are susceptible to storage-associated death. The hypothesis of this study was that the loss of chondrocytes within osteochondral grafts leads to decreased PRG4 secretion, after graft storage and subsequent implant. The objectives were to determine the effect of osteochondral allograft treatment (FROZEN vs. FRESH) on secretion of functional PRG4 after (i) storage, and (ii) 6 months in vivo in adult goats. FROZEN allograft storage reduced PRG4 secretion from cartilage by ∼85% compared to FRESH allograft storage. After 6 months in vivo, the PRG4-secreting function of osteochondral allografts was diminished with prior FROZEN storage by ∼81% versus FRESH allografts and by ∼84% versus non-operated control cartilage. Concomitantly, cellularity at the articular surface in FROZEN allografts was ∼96% lower than FRESH allografts and non-operated cartilage. Thus, the PRG4-secreting function of allografts appears to be maintained in vivo based on its state after storage. PRG4 secretion may be not only a useful marker of allograft performance, but also a biological process protecting the articular surface of grafts following cartilage repair.