Background/Purpose: Our goal is the identification of informative synovial biomarkers to predict persistent vs extended course in oligoarticular JIA patients.

Methods: Stored remnant synovial fluid samples obtained from patients undergoing medically indicated arthrocenteses were retrieved. Using our clinical database, JIA samples were separated into two groups: (1) oligoarticular JIA with persistent course (PR), (2) oligoarticular JIA with extended course (E). All samples were from steroid-na•ve joints and all samples from E were obtained prior to extension. Primary cultures of fibroblast-like synoviocytes (FLS) were established for each subject. RNA from cultured passage 3-6 FLS were isolated, amplified and hybridized to Affymetrix Human GeneChips using the Affymetrix protocol.  Expression values were determined with GC-RMA. Global gene expression of FLS from 5 PR and 9 E samples were obtained.  Data was filtered for log2 expression >4 in all samples of either PR or E, then for absolute value of 1.5-fold change to reveal 3231 probesets.  Of these, LIMMA revealed 39 probesets with statistically significant differential expression between PR vs E FLS (p<0.05), shown in heatmap (Figure 1).

Results: Hierarchical clustering of the 39 probesets revealed samples from the different courses cluster together, with all the E to the left of the heatmap.  Importantly, the E were all taken from the very first sample available, which preceded extension in all patients, highlighting that there are detectible differences in the gene expression of the FLS early in the course in the patients whose disease is destined to extend. These 39 probesets represent 32 unique genes. PR overexpressed 19 genes, including known biomarkers for other diseases, AURKA, CCNB1, PLAUR and the secreted protein IGFBP6, in addition to another secreted protein, COL5A1.  E overexpressed 13 genes, including known biomarkers for other diseases, XIST and secreted protein GDF5, which is important in inflammatory and apoptotic pathways and activates macrophages within the TNFa pathway.

Conclusion: We were able to demonstrate differential gene expression in FLS from JIA patients who remained PR vs those who were destined to extend, demonstrating detectible difference early in disease which may be useful for prediction.  The differentially expressed proteins, especially secreted proteins, provide a starting point for development of biomarkers to distinguish between PR and E JIA using aspirated synovial fluid.

Figure 1