Age‐related changes in human meniscal glycosaminoglycans
Authors: Blackburn Gareth , Al‐Jafary Meneerah , Huckerby Tom , Lauder Robert 
Published: August 2004

Introduction  With an increased human lifespan, a major challenge is now to ensure a concomitant increase in healthspan. Meniscal damage and degradation are common and are strongly correlated with subsequent osteoarthritis. Indeed, meniscal damage has been identified in about 60% of people over 60. Markers of pathology will facilitate intervention but first require normal age‐related changes to be established.

Methods  Undamaged vascular and avascular regions of medial and lateral human menisci were comminuted and the tissue extracted into 4‐m GuHCl and subject to associative CsCl density gradient centrifugation. Aggrecan and the small leucine rich PGs (SLRPs) were isolated and their GAG profiles examined by HPAEC fingerprinting, following enzyme depolymerization, and by an NMR spectroscopy.

Results and discussion  Analysis of aggrecan and the SLRPs show that there is a complex and dynamic pattern of KS, CS and DS abundance and distribution within human menisci, which changes with age.

The abundance of SLRPs is higher in the avascular than vascular tissues, however, this is not reflected in the abundance of aggrecan which is present at similar levels in both tissue regions. The data show no other significant differences between medial and lateral and between vascular and avascular tissue regions.

Analysis of the sulfation pattern of CS following digestion by ACII lyase, shows that in both aggrecan and SLRPs the 4‐sulfation level falls with age from 20 to 35% in young tissues to 10–20% in older. Subsequent analyses following ABC lyase depolymerization, to include DS, shows very significant change with age from CS + DS 4‐sulfation levels of ca. 40–55% in young tissue to ca. 15–30% in older.

The difference between these datasets represents the contribution made by 4‐sulfated DS. Thus, analysis of the difference suggests that DS makes a decreasing contribution to the CS/DS profile with age.

Indeed, this is confirmed by an NMR analysis of these samples. Analysis of the resonances in the region 1.95–2.2 p.p.m. (ref to TSP) allows the estimation of the contribution made by DS, CS and KS. These data show that, in aggrecan, the contribution made by DS chains falls from ca. 10% in younger tissues to ca. 2–4% in older tissues.

NMR analysis also shows that KS levels fall with age from ca. 15–20% in younger tissues to 5–10% in older tissues. Analysis of the structure of the KS chains shows chains with a structure similar to that of in articular cartilage but that at all ages there are very low levels of fucosylation (ca. 1–5%).

Previous studies of age‐related changes in CS/DS and KS structures have shown significant changes in the first 17 years of life, with only modest nonpathological changes after that time. These data from meniscal tissues do not show such a dramatic halting of normal age‐related changes. Indeed, the data show gradual age‐related changes in DS, CS and KS abundance and structure throughout life.

These baseline age‐related changes data will now allow the analysis of pathology‐related changes.