Background/Purpose: A significant progress has recently been made in the identification of molecular profiles involved in the pathogenesis of chronic autoinflammatory diseases through the use of high throughput techniques such as massive RNA sequencing. To date, only few studies have been carried out in axial spondyloarthritis (axSpA), which would allow the identification of new therapeutic targets and disease biomarkers.Objectives: 1) To identify clusters of highly correlated genes enriched in biological functions and specific molecular pathways involved in the pathogenesis of axSpA. 2) To study the association between the molecular signatures identified and the clinical-analytical profile of the disease.

Methods: Cross-sectional study including 20 healthy donors and 105 axSpA patients from the CASTRO cohort who underwent an exhaustive clinical evaluation including disease activity and functional limitation, structural damage and spinal mobility. Additionally, analytical parameters were measured and the carotid intima media thickness was evaluated by carotid eco-doppler. Mononuclear cells were purified from peripheral blood, and RNA was isolated. RNA from 25 axSpA patients was sequenced using the Illumina platform. For the identification of patient subgroups and the generation of co-expressed gene modules, the “hierarchical clustering” and WGCNA (“Weight gene correlation network analysis”) methodologies were used, respectively. Functional analysis of the genes conforming each module was carried out to identify enriched pathways and functions using the EnrichR platform. Hub genes were measured through high throughput PCR (Fluidigm Biomark HD) in a validation cohort of 80 axSpA and 20 healthy donors. Association and correlation studies between the molecular and the clinical profiles were performed.

Results: Unsupervised analysis of the transcriptome revealed the presence of two “clusters” of axSpA patients, clearly differentiated by their molecular and clinical profile. Specifically, the molecular analysis distinguished patients with a longer disease duration, greater disease activity, radiographic damage and cardiovascular risk. WGCNA identified 11 highly co-expressed modules. Among them, six were differentially expressed between the two clusters, being responsible for the molecular and clinical distinction of those groups. The functional analysis of these 6 gene modules revealed the enrichment of these genes in pathways related to inflammation, oxidative metabolism, proliferation of B and T lymphocytes, immune response and the increase of cell survival. Finally, key genes were identified within each module (“hub genes”), whose expression was associated with a more active phenotype of the disease such as ALOX5, GAB2, PSMD13, CASP8, NOTCH e ITGA4.

Conclusion: 1) The whole transcriptomic analysis by RNAseq in peripheral mononuclear cells from axSpA patients distinguished, in an unsupervised manner, subgroups of patients with distinctive clinical profiles. 2)The analysis of gene modules identified new pathways and molecular functions potentially involved in the pathophysiology of the disease.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/high-throughput-transcriptomic-analysis-of-peripheral-mononuclear-cells-identifies-molecular-alterations-associated-with-the-active-clinical-phenotype-of-axial-spondyloarthritis/