Background of the invention: Angiogenesis refers to the process by which new capillary blood vessels are formed from existing microvessels, resulting in the development of a blood supply to a given area of tissue [23, 25]. It is one of the most pervasive and fundamen...
Background of the invention: Angiogenesis refers to the process by which new capillary blood vessels are formed from existing microvessels, resulting in the development of a blood supply to a given area of tissue [23, 25]. It is one of the most pervasive and fundamentally essential biological processes encountered in mammalian organizations. In the healthy, adult human body, angiogenesis is a normal and important function that is critical in a variety of physiological settings, including chronic inflammation, embryonic development, reproduction, and wound healing [22, 29]. For example, angiogenesis occurs in the female reproductive system, in response to ovulation or gestation, and in the normal hair cycle . Nevertheless, apart from the processes of wound healing and inflammation, angiogenesis virtually never occurs physiologically in adult tissues, except in the ovary, the endometrium, and the placenta . When defective or uncontrolled, angiogenesis is also central to a number of pathological processes, including: abnormalities of wound healing in diseases such as diabetes and duodenal ulceration; chronic inflammatory disorders, such as rheumatoid arthritis, psoriasis, and periodontitis; dermatological conditions such as cutaneous malignancy, decubitus ulcers, hemangiomas, Kaposi's sarcoma, psoriasis, pyogenic granulomas, and warts; diseases of the eye, particularly diabetic retinopathy; and growth of solid tumors, both benign and malignant [22, 23, 25, 26]. The consequence of abnormal angiogenesis is either excessive or insufficient blood vessel growth. Ulcers, strokes, and heart attacks can result from the absence of angiogenesis normally required for natural healing, while excessive blood vessel proliferation may favor arthritis, blindness, and tumor growth and dissemination [29 ]. The angiogenic process is tightly regulated (in both time and space) by a variety of endogenous angiogenic and angiostatic factors. It is propelled by a mixture of growth factors and pro-angiogenic cytokines, and is moderated by a collection of inhibitors of neovascularization which interfere with steps in the angiogenic process [22, 30]. In angiogenesis, capillary sprouts are formed in response to pro-angiogenic factors. The sprouts then grow and develop, driven by endothelial cell migration and proliferation, and organize themselves into a ordendritic structure . Angiogenic and anti-angiogenic molecules control the formation of new vessels via different mechanisms. Hypoxia and other ill-defined stimuli drive tumor, inflammatory, and connective tissue cells to generate angiogenic molecules, such as vascular endothelial growth factor, fibroblast growth factor, transforming growth factor beta, and platelet-derived growth factor. Natural and synthetic angiogenesis inhibitors, such as angiostatin, thalidomide, and thrombospondin, can repress angiogenesis .