Explore Biomarkers In Peripheral Blood Cells To Predict Radiographic Severity In African Americans With Rheumatoid Arthritis

Objective:The clinical phenotype of Rheumatoid Arthritis (RA) ranges from mild joint inflammation to severe joint destruction. Patients with RA who develop erosions early in the course of their disease are more likely to rapidly progress to joint destruction and functional limitations, also, have a relatively higher mortality rate. Understanding these factors would facilitate the use of tailored therapies to minimize joint damage, but molecular factors responsible for variability are poorly understood, and no available predictors are highly predictive of disease severity and their utility for prognosis in clinical practice is limited, particularly in African-Americans compared with Caucasians in America. We sought to identify genes whose expression in peripheral blood mononuclear cells (PBMCs) is associated with radiographic severity of RA in African-Americans.Methods:This study was conducted in three parts. Part1sought to delineate an immune-related gene expression profile of40African-American RA patients with extremes of phenotypes in disease duration and radiographic severity, and20healthy controls. Collect PBMCs samples and extract total RNA using PAXgene Blood RNA Kit. Detect RNA quality and concentration using Agilent RNA6000Nano Kit and then reversely transcribe RNA into cDNA using High-Capacity cDNA Reverse Transcription Kit. Quantitative real-time PCR (qPCR) was performed to get immune-related gene expression profile for every sample using QIAGEN RT2Profiler PCR Arrays System. Gene set analysis was performed to determine whether these genes were overexpressed among relevant biological pathways. Part2validated expression of five genes, interferon gamma receptor1(IFNGR1) and2(IFNGR2), chemokine receptor CXCR3, oncogenes MYC and FYN, in seventy African-American RA patients (grouped into light, medium and heavy based on radiographic severity) and48healthy controls. Extract RNA and generate cDNA as described. Gene expression levels were detected using TaqMan(?) gene expression assays. Part3further validated the expression of the most promising candidate gene IFNGR2and its biological partner IFNGR1in580RA patients with different radiographic scores and51healthy controls. All the patients and controls enrolled are from the Consortium for the Longitudinal Evaluation of African-Americans with Rheumatoid Arthritis (CLEAR) Registry. Radiographic severity was defined as total Sharp/van der Heijde scores of hands/feet.Results:Part1:1) Immune-related gene expression profile in PBMCs is significantly correlated with radiographic severity in African-American RA patients;2) Cytokine signaling pathway, NF-κB pathway, Mitogen-activated Protein Kinases (MAPK) pathway, T cell receptor pathway, Toll-like receptor pathway, TNF signaling pathway are the main pathways related to RA susceptibility and severity in African-Americans. Part2:1) Expression of IFNGR1, CXCR3, MYC, and FYN are not significantly related to RA severity in African-Americans;2) Increased expression level of IFNGR2is closely related to more severe RA in African-Americans. Part3:1) Compared with healthy controls, there is a higher expression of IFNGR1and IFNGR2in African-American RA patients.2) IFNGR2, rather than IFNGR1, is closely related to radiographic severity of RA in African-Americans.3) Results of a zero-inflated negative binomial model for clinical outcomes with IFNGR2as a predictor adjusting for disease duration in years shows IFNGR2can predict the severity of RA in African-Americans.Conclusions:1) Immune-related gene expression profile in PBMCs is associated with radiographic severity of RA in African Americans;2) IFNGR2is a potential predictor of radiographic severity of RA in African Americans.3) This study yields insight into the function study of IFNGR2and pathophysiology study of RA.