Fig. 5

Candidate Ion validation Across Multiple OA Patients Comparing Medial to Lateral Joints. a Regions of Interest (ROIs in green) were manually segmented around the outer most regions of the medial and lateral tibial plateaus of OA patients (n = 4), using the edge of the cartilage layer (thin blue line) as a guide for affected tissue in medial joints and using an equivalent distance on the lateral side. Average pixel intensity within the segmented region was calculated for each candidate ion that was previously identified using automated tissue segmentation and ROC curve predictive score. b Visualization of data grouping by 3-dimensional PLS-DA of pixel intensity showed distinct separation between the two joint sides despite physiologic complexity and patient heterogeneity in the OA medial cohort. c Group-wide heat maps of candidate feature distribution with peptide IDs derived from several ECM proteins or related proteins, Collagen alpha-1(III) (Col3A1) G³⁶⁶QRGEP^(ox)GPQ³⁷⁴ at m/z 941.43, Collagen alpha-1(I) (Col1A1) G¹¹⁶⁶PRGRTGD¹¹⁷³ at 1 139.58 m/z, Asporin (ASPN) A²⁰⁴NPLDNN^(de)GIEPGAFEG²¹⁹ at m/z 1 615.74, and Collagen alpha-3(VI) (Col6A3) G²⁰⁰⁷EIGLDGLDGEDGDKGLP^(ox)2124 at m/z 1 772.80, depicted increases of the ion intensity in the outermost region of medial OA joints compared to their lateral counterparts (of the same OA patient). Statistical differences in feature intensities were confirmed via paired t-test *P < 0.05 (n = 4) see Table S2