Significant differential imaging of some ECM peptides. Biomap was used to localize and quantify the differences in the peptide peak intensity of m/z 1679.8, m/z 2256.1 and m/z 2027.2 between young, old and OA cartilages. Samples representative of each group are illustrated here. Scale bar shows normalized intensities to 190 m/z matrix peak. In the scale bar red represents the highest signal. Histograms show the means of the relative peak intensities and 95% CI, n = 3 for each peptide. There was no change in the distribution of the type II collagen peak m/z 1679.8. However, a significant difference was evident for the COMP peptide m/z 2256.1 (P = 0.03 young versus old and old versus OA) and the biglycan peptide m/z 2027.2 (P = 0.02, young versus OA and old versus OA). COMP, cartilage oligomeric matrix protein; ECM, extracellular matrix; OA, osteoarthritis; 95% CI, 95% confidence interval.