PubMed · 14437162
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J REINERT. 1960-02-05. [Phytohormones].. https://doi.org/10.1055/s-0029-1209728
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Growth factors (GF) are important in several stages of the pathogenesis of age-related macular disease (AMD). In choroidal neovascularization (CNV) in exudative AMD, the GF involved are similar to those involved in wound healing of the skin. Like granulation tissue of skin, CNV is characterized by clotting, inflammation, angiogenesis and fibrosis, and like in skin wounds, members of the VEGF, angiopoietin, PDGF and TGF-beta families of GF are expressed. However, several of these GF may also serve physiological functions in the normal eye, where the retinal pigment epithelium (RPE) employs them to provide trophic support to the neuroretina and choriocapillaris, in addition to maintaining an anti-angiogenic state. Derangement of these physiological functions may underlie the initiation of CNV in AMD. Basolateral secretion of VEGF-A by the RPE maintains the choriocapillaris, and is enhanced by hypoxia. Age-related changes in Bruch's membrane lead to impairment of this trophic function and choriocapillaris atrophy, as well as to decreased diffusion of oxygen towards the neuroretina. The resulting outer retina hypoxia may be an important driving force of CNV formation, by stimulating VEGF overexpression by the RPE, in addition to the effects of increased oxidative stress and low-grade inflammation. RPE senescence and hypoxia may also decrease expression of angiogenesis inhibitors such as PEDF, further shifting the balance to a pro-angiogenic state in the aging eye.
There is much evidence that angiogenesis is related to mast cells. Mast cells accumulate in many angiogenesis-dependent situations, including tumor growth, rheumatoid arthritis, ovulation, would healing, and tissue repair. Several mast cell mediators are angiogenic and regulate endothelial cell proliferation and function. Stem cell factor, vascular endothelial growth factor, epidermal growth factor, basic fibroblast growth factor, and platelet-derived growth factor induce chemotactic migration of mast cells to sites of neovascularization. Mast cell products such as tryptase also degrade connective tissue matrix to provide space for neovascular sprouts. Angiogenesis has been proposed as a target for anticancer therapy and for treatment of inflammatory disorders such as rheumatoid arthritis. Future studies on the cascade of angiogenic events, including mast cell-target cell interaction, and various intracellular signaling pathways are indicated to provide a new approach for the treatment of cancer and inflammatory disorders and for tissue repair.
Enhancement of wound healing was limited to good surgical technique, maintenance of a clean wound with appropriate dressings, and debridement. The ability to heal wounds has been advanced through the recognition that healing in a moist environment is improved over that of a desiccated wound. Pharmacologic approaches to wound healing did not exist until the last few decades, when it was recognized that growth factors are normally present in the wound environment and that in animal models and a few clinical studies, the addition of growth factors could enhance healing. In 1998, platelet-derived growth factor was approved for clinical use. This approach is still the subject of intense investigation and clinical trials. This article analyzes current knowledge on growth factors as therapeutic agents and speculates on their future potential, with an analysis of successes and failures to date.