Age-related changes in the synthesis and mRNA expression of decorin and aggrecan in human meniscus and articular cartilage

Objective: To determine if the biosynthesis of aggrecan and decorin in the human meniscus and the potential of the cells to express these macromolecul es (mRNA), is affected by the age of the individual and that if any changes are observed are they different to those measured in articular cartilage o btained from the same joint. Design: Radiolabelling of tissue explants. anion-exchange chromatography an d agarose-polyacrylamide gel electrophoresis were used to analyze newly syn thesized proteoglycans. A quantitative, competitive reverse-transcriptase p olymerase chain reaction was developed and applied to the tissue to measure the expression of decorin and aggrecan mRNA. Results: Proteoglycan synthesis in the meniscus was higher in young donors (1-5 mmoles sulfate incorporated/h/mgDNA, under 20 years of age) than in ad ult tissues (0.5-1 mmoles incorporated/h/mgDNA. 20-62 years of age) and dec orin was the major proteoglycan synthesized at this time. An age-related in crease in the proportion of aggrecan synthesis in the meniscus was also obs erved using agarose-polyacrylamide gel electrophoresis. Both decorin (five- fold) and aggrecan (eight-fold) mRNA expression increased with age in menis cus whereas levels were relatively constant in articular cartilage. In addi tion, the synthesis of decorin and aggrecan and the expression of their mRN A was different in meniscus and articular cartilage from the same knee join t. Conclusion: The synthesis and turnover of aggrecan and decorin in the human meniscus is influenced by the age of the individual and is not the same as that observed for articular cartilage. (C) 2001 OsteoArthritis Research So ciety International.