Angiogenesis in Inflammatory Arthritis.

BACKGROUND: Angiogenesis is the outgrowth of new blood vessels from existing ones and is an early occurrence in inflamed joint tissue. It is governed by a tightly controlled balance of pro- and anti-angiogenic stimuli, which promote or inhibit generation and proliferation of new endothelial cells, vascular morphogenesis, and vessel remodeling. At the beginning, capillary formation is crucial in maintaining the supply of various nutrients as well as oxygen to the inflamed tissue. Local and systemic expression of angiogenic factors may indicate a constant remodeling of synovial vasculature. Redox signaling is closely related to angiogenesis and can alter angiogenic responses of synovial cells. In this review we discuss key issues about the endothelial pathology in inflammatory arthritis followed by a review of angiogenic processes and main angiogenic mediators. We discuss the hypoxia-vascular endothelial growth factor (VEGF)-Ang/Tie2 system and its related therapeutic implications in detail with further review of various mediator protein targets and intracellular regulatory pathway targets with their current and potential future role in preclinical or clinical setting whilst ameliorating inflammation.