A matrix metalloproteinase–generated aggrecan neoepitope as a marker of skeletal maturation and aging in cartilage

OBJECTIVE: To quantify the matrix metalloproteinase-induced neoepitope F(M/V)DIPEN (Phe-[Met/Val]-Asp-Ile-Pro-Glu-Asn341) in guinea pig and rabbit cartilage during aging. METHODS: Cartilage was taken from the stifle joint, nasal septum, and xiphoid process in guinea pigs and rabbits at selected ages. The cartilage was then extracted and evaluated for F(M/V)DIPEN levels by radioimmunoassay. RESULTS: In the 3 tissues studied, there were major increases in F(M/V)DIPEN levels during skeletal maturation and aging in both the guinea pig and rabbit cartilage. Except for spontaneous osteoarthritis that develops in guinea pigs with aging, increases in the neoepitope were not correlated with arthritis pathology. CONCLUSION: Increases in the level of F(M/V)DIPEN in cartilage occur as a result of skeletal maturation and aging. This physiologic accumulation of F(M/V)DIPEN in cartilage should be considered when using the neoepitope as a disease marker in arthritis.