FIGURE 5.

Enrichment of D-COMP in hip cartilage and OA lesion sites. Soluble proteins were extracted from cartilage using 4 m Gdn-HCl before buffer exchange into PBS to allow further analysis. Total COMP (a) and D-COMP (b) were measured by sandwich ELISA and normalized to total protein to correct for variations in the extraction and dialysis efficiency. The ratio of D-COMP/total COMP (c) was calculated as a measure that is independent of technical variation due to variation in protein extraction and dialysis efficiency. Data were plotted on a logarithmic scale for clarity, and statistical differences were determined on nonlogarithmically transformed data using nonparametric statistics. For paired samples (remote and lesion within a joint), the Wilcoxon signed rank test was used; for nonpaired samples (hip and knee joint comparisons) intergroup significance was determined using the nonparametric Mann-Whitney U test. D-COMP and the D-COMP/total COMP ratio were higher in hip than knee cartilages and higher in hip OA lesions than in hip cartilage remote from lesions.