EFNA3 and rheumatoid arthritis: Furthermore, we exposed FLS to a range of oxygen tensions (1 to 10% oxygen) and found that the genes of interest (ANGPTL-4, VEGF, leptin, EFNA3) change in a similar fashion at 3%, the median oxygen tension measured in RA synovium when compared with 1% oxygen, albeit to a lesser extent (see Additional file 2).