EPAS1 and rheumatoid arthritis: More importantly, the development of RA-like phenotypic manifestations, including synovitis, pannus formation and invasion, cartilage destruction, and angiogenesis, induced in inflamed synovium by IA injection of Ad-Epas1 was markedly diminished in Il6−/− DBA/IJ mice compared with WT mice (Figure 9E and F).