Extracellular matrix components and angiogenesis

Angiogenesis, the formation of new capillaries, is critical for normal physiological processes such as embryonic development and wound repair. However, it also facilitates pathological processes including tumor growth, metastases, proliferative diabetic retinopathy and pannus formation in rheumatoid arthritis. It has been described that the angiogenesis occurs through a series of events that include endothelial cell protease production, migration and proliferation, tubule formation, and basement membrane incorporation. Within the last two decades, with in vivo assay systems, various kinds of growth factors were identified as angiogenic factors that promote endothelial cell proliferation and migration, while an in vitro model for angiogenesis indicated that extracellular matrix (ECM) proteins stimulated endothelial cells to organize into a capillary-like tubular network and suggested that the ECM proteins are involved in the tubule formation process of antiogenesis. Recent papers reported the identification of the specific receptors on endothelial cells involved in the ECM-induced capillary tube formation. This article will focus on papers describing the in vitro analyses of tube formation of endothelial cells.