Nonfrozen preservation of articular cartilage by epigallocatechin-3-gallate reversibly regulating cell cycle and NF-kappaB expression.

Epigallocatechin-3-O-gallate (EGCG) is known to have beneficial effects on the nonfrozen preservation of mammalian cells and tissues. In this study, we aimed at testifying the hypothesis that the deleterious effects of cold preservation of articular cartilages can be ameliorated by the addition of EGCG to the storage media. Articular cartilages were preserved in a storage solution composed of serum-free RPMI 1640 media with 1 mM EGCG at 4 degrees C for 1-4 weeks. The regulatory effects of EGCG on cell cycle progression as well as expression levels of CyCliNS (CCNs) and nuclear factor-kappaB (NF-kappaB) were investigated in articular chondrocytes. Chondrocyte viability of cartilages preserved with EGCG was significantly well maintained for 2 weeks with high contents of glycosaminoglycan and total collagen. These beneficial effects of EGCG were confirmed by histological and immunohistochemical observations showing well-preserved cartilaginous structures and delayed denaturation of extracellular matrices. The compressive elastic modulus of cartilages preserved with EGCG was close to that of fresh specimens. Increased cell population at the G(0)/G(1) phase by EGCG returned to the normal level after EGCG removal, whereas decrease at the G(2)/M phase did not. Negatively regulated expression of CCND1, CCNE2, or NF-kappaB in EGCG-treated cells was restored by removing EGCG, but not CCNA2 and CCNB1. After 8 weeks of in vivo implantation into full-thickness cartilage defects in rabbits, the cartilages preserved with EGCG were found to be integrated with the host environment and support tissue regeneration. It is suggested that EGCG plays effective roles in preserving and repairing articular cartilages by reversibly regulating cell cycle at G(0)/G(1) phase and NF-kappaB expression.