Identification of a genetic variant for joint damage progression in autoantibody-positive rheumatoid arthritis.

BACKGROUND:Joint destruction is a hallmark of autoantibody-positive rheumatoid arthritis (RA), though the severity is highly variable between patients. The processes underlying these interindividual differences are incompletely understood. METHODS:We performed a genome-wide association study on the radiological progression rate in 384 autoantibody-positive patients with RA. In stage-II 1557 X-rays of 301 Dutch autoantibody-positive patients with RA were studied and in stage-III 861 X-rays of 742 North American autoantibody-positive patients with RA. Sperm-Associated Antigen 16 expression in RA synovium and fibroblast-like synoviocytes (FLS) was examined using Real-Time Quantitative (RT-qPCR) and immunohistochemistry. FLS secrete metalloproteinases that degrade cartilage and bone. genotypes were related to matrix metalloproteinase (MMP)-3 and MMP-1 expression by FLS in vitro and MMP-3 production ex vivo. RESULTS:A cluster of single nucleotide polymorphisms (SNPs) at 2q34, located at associated with the radiological progression rate; rs7607479 reached genome-wide significance. A protective role of rs7607479 was replicated in European and North American patients with RA. Per minor allele, patients had a 0.78-fold (95% CI 0.67 to 0.91) progression rate over 7 years. mRNA and protein expression of duanyu1842G16 in RA synovium and FLS was verified. FLS carrying the minor allele secreted less MMP-3 (p=1.60×10(-2)). Furthermore, patients with RA carrying the minor allele had lower serum levels of MMP-3 (p=4.28×10(-2)). In a multivariate analysis on rs7607479 and MMP-3, only MMP-3 associated with progression (p=2.77×10(-4)), suggesting that the association between and joint damage is mediated via an effect on MMP-3 secretion. CONCLUSIONS:Genetic and functional analyses indicate that duanyu1842G16 influences MMP-3 regulation and protects against joint destruction in autoantibody-positive RA. These findings could enhance risk stratification in autoantibody-positive RA.

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