Fig. 1. RA angiogenesis is driven by pro-inflammatory cytokines released from the cells in the synovial tissue-lining layer.
In response to inflammatory stimuli, RA synovial tissue macrophages and fibroblasts produce pro-inflammatory cytokines that can modulate expression of adhesion molecules, MMPs, chemokines and growth factors which are all important in different stages of angiogenesis. There are several steps involved in angiogenesis; which consist of endothelial cells migration, endothelial cell proliferation into vascular tubules, separation of the newly formed blood vessels that mature and become interconnected to the circulatory system.