CHARACTERIZATION AND APPLICATIONS OF THE DISK ANGIOGENESIS SYSTEM

A model to study microvascular proliferation, the Disc Angiogenesis System (DAS), consists of a synthetic foam disc implanted subcutaneously in experimental animals. After a period of growth, usually 7 to 21 days, the disc is removed. Planar sections are used to measure and characterize the growth. Microvessels grow centripetally into the disc, together with fibroblasts. Concentric growth zones have been defined by light and electron microscopy. Moderate growth occurs spontaneously and is accelerated by angiogenic stimulants placed in the center of the disc. Morphometric analyses have shown that vessel growth is directly proportional to total fibrovascular growth, so the former can be quantified by procedures measuring the latter. These include manual projection of sections and computer-assisted digital image analysis, which is recommended for routine use. The proliferation of endothelial and other cells is determined by incorporation of tritiated thymidine, using scintillation counting and autoradiography. Using the DAS, well-established angiogenic agents such as basic fibroblast growth factor (bFGF), epidermal growth factor (EGF), and prostaglandin E1 were found to increase proliferation of endothelial cells (EC) and microvessels. Heparin augmented the effect of bFGF. When used by itself heparin increased angiogenesis but not EC proliferation, in keeping with in vitro observations indicating that it stimulates migration but not proliferation of EC. Locally applied hyperthermia and ionizing radiation decreased angiogenesis, even when applied after the angiogenic stimulus. Systemic prostaglandin synthetase inhibitors antagonized the angiogenic effects of bFGF and EGF, in accordance with a postulated role of prostaglandins in the transduction of proliferative signals in microvascular EC. The DAS is easy to assemble and implant in small animals, including mice, which tolerate it well. Hence multiple discs can be used for each time or dose point, which allows reproducible measurements of vascular growth and increases statistical accuracy. Another advantage of the system is the capability of discriminating between proliferation and migration of EC and fibroblasts. The DAS can be used to test putative agonists or antagonists of angiogenesis. More generally, the DAS provides a model of wound healing, either uncomplicated or complicated by inflammation, and of angiogenic responses to solid tumors. © 1992.