Influence of site and age on biochemical characteristics of the collagen network of equine articular cartilage

Objective-To determine variations in biochemical characteristics of equine articular cartilage in relation to age and the degree of predisposition for osteochondral disease at a specific site. Sample Population-Articular cartilage specimens from 53 horses 4 to 30 year s old. Procedure-Healthy specimens were obtained from 2 locations on the proximal articular surface of the first phalanx that had different disease prevalenc es (site 1 at the mediodorsal margin and site 2 at the center of the medial cavity). Water, total collagen, and hydroxylysine contents and enzymatic ( hydroxylysylpyridinoline [HPI) and nonenzymatic (pentosidine) crosslinking were determined at both sites. Differences between sites were analyzed by A NOVA (factors, site, and age), and age correlation was tested by Pearson's product-moment correlation analysis. Significance was set at P< 0.01. Results-Correlation with age was not found for water, collagen, hydroxylysi ne contents, and enzymatic crosslinking. Nonenzymatic crosslinking was high er in older horses and was linearly related to age (r = 0.94). Water and co llagen contents and HP and pentosidine crosslinks were significantly higher at site 1. Hydroxylysine content was significantly lower at site 1, Conclusions-Except for nonenzymatic glycation, the composition of articular cartilage collagen does not change significantly in adult horses. A signif icant topographic variation exists in biochemical characteristics of the ar ticular cartilage collagen network in equine metacarpophalangeal joints. Th ese differences may influence local biomechanical properties and, hence, su sceptibility to osteochondral disease, as will greater pentosidine crosslin ks in older horses that are likely to cause stiffer and more brittle cartil age.