MMP1 and rheumatoid arthritis: While there have been previous reports of increased MMP expression/activity in RA fibroblasts exposed to hypoxia, particularly for MMP-1 and MMP-3 [32,34,35], our studies have attempted to mimic RA synovial membrane milieu by utilising total RA synovial membrane cells, which include macrophages as well as fibroblasts, thus possibly explaining the differences between these published data and our own.