A "best-in-class" systemic biomarker predictor of clinically relevant knee osteoarthritis structural and pain progression

Abstract

We aimed to identify markers in blood (serum) to predict clinically relevant knee osteoarthritis (OA) progression defined as the combination of both joint structure and pain worsening over 48 months. A set of 15 serum proteomic markers corresponding to 13 total proteins reached an area under the receiver operating characteristic curve (AUC) of 73% for distinguishing progressors from nonprogressors in a cohort of 596 individuals with knee OA. Prediction based on these blood markers was far better than traditional prediction based on baseline structural OA and pain severity (59%) or the current "best-in-class" biomarker for predicting OA progression, urinary carboxyl-terminal cross-linked telopeptide of type II collagen (58%). The generalizability of the marker set was confirmed in a second cohort of 86 individuals that yielded an AUC of 70% for distinguishing joint structural progressors. Blood is a readily accessible biospecimen whose analysis for these biomarkers could facilitate identification of individuals for clinical trial enrollment and those most in need of treatment.

Fig. 1.. Screening, classification, and analysis of the FNIH600 cohort.

*Magnetic resonance imaging (MRI) artifact, knee positioning exclusions; **frequency matching for 15 combinations of K/L grades by BMI strata, with random selection.

Fig. 2.. Backward elimination process to yield essential biomarker sets.

(A) JSL and pain progressor versus composite comparator (JSL or pain-only progression or combined JSL and pain nonprogression), (B) JSL and pain progressor versus nonprogressor, (C) JSL progressor versus nonprogressor, (D) pain progressor versus nonprogressor. The biomarkers in the stable sets were sorted by the area under the receiver operating characteristic curve (AUC) drop associated with a single biomarker removal from the model. Certain rules were applied to determine the stop point (red dot) as described in the methods. The AUC of each model was calculated as the average value of 10 imputed datasets. boot.ave (left y axis), the average AUC when fitting on the bootstrapping samples; orig.ave (left y axis), the average AUC of fitting on the original datasets; bias.ave (right y axis), the average bias between original AUC and bootstrapping AUC. Each peptide is defined (full name and sequence) in table S1.

Fig. 3.. Venn diagram of selected protein biomarkers.

(A) Stable biomarker sets of the primary and secondary end points. (B) Essential biomarker sets of the primary and secondary end points. Proteins in overlapping regions are selected in common in corresponding comparison models. prog., progression.

Fig. 4.. Forest plot and OR estimates for the models with the essential biomarkers.

(A) The JSL and pain progressor group compared to the composite comparator group defined as the combined JSL and pain nonprogressor, JSL-only progressor, and pain-only progressor groups; (B) the JSL and pain progressor group compared to the JSL and pain nonprogressor group; (C) the JSL-only progressor group compared to the JSL and pain nonprogressor group; (D) the pain-only progressor group compared to the JSL and pain nonprogressor group. Parameter estimates of each model were obtained by fitting on 10 imputed data sets. Rubin’s rules were then applied to combine the estimates from the repeated complete data analyses. Because the peptide ratios were first standardized by their own SD, the results are presented as the ORs for an SD change of the corresponding peptides ratios. With our peptide selection strategy, most of the biomarkers significantly contribute to knee OA progression or benign symptoms.

Fig. 5.. Joint tissue gene expression profile corresponding to essential biomarkers.

(A) Expression level, defined as number of cells expressing the gene (y axis) corresponding to the essential biomarker (gene name listed on the x axis above the graphic) in the medial tibial (MT) lesioned knee OA articular knee cartilage, outer lateral tibial (OLT) nonlesioned knee OA articular cartilage, and matched knee OA synovium (SY); the data are extracted from a previously described database of scRNA-seq data (47). Of the 27 proteins comprising the essential peptides, 19 were found in the transcriptome data and are plotted. (B) Stacked bar plots depict the top ranked canonical pathways from ingenuity pathway analysis associated with all four OA progression phenotypic models at P < 0.05 [i.e., −log₁₀ (P value) > 1.3]. prog., progression.