ABSTRACT
Regulation of new blood vessel growth, the process of angiogenesis, is critical for inflammation, wound healing, granulation tissue formation, development of fibroproliferative diseases, and solid tumor growth. Numerous studies over the past three decades have indicated that angiogenesis is regulated by a series of growth regulatory factors affecting the principal cells that constitute the microvasculature, namely, endothelial cells, smooth muscle cells, and pericytes. The angiogenic and antiangiogenic growth regulatory factors are produced by these vascular cells themselves, as well as by nonvascular cells recruited to the vicinity of the microvasculature as a result of microenvironmental signals. These nonvascular cells include monocytes/macrophages, lymphocytes and platelets, recruited as part of inflammatory processes, and certain populations of tumor cells produced as a result of cellular transformation. Many transformed cells produce high levels of proangiogenic growth factors, such as vascular endothelial growth factor (VEGF) and various isoforms of fibroblast growth factor (FGF), including oncogenic forms, in an unregulated,
constitutive fashion, due to genetic alterations in the transcription factors involved in the expression of these factors.
