A Novel Quantitative In Vitro Model of Angiogenesis

The process of angiogenesis includes sprouting of new vessels from pre-existing ones, their remodelling and regression. Angiogenesis is a pre-requisite for growth and differentiation of organs and tissues as it allows for supply with nutrients and oxygen (Folkman, 2003). Angiogenesis also plays a key role in many pathological processes, particularly growth and metastasis of tumours (Folkman, 1995; Caldwell et al., 2005; Banning, 2005). Both, the stimulation of angiogenesis to generate new vessels in ischemia and the inhibition of angiogenesis, so called antiangiogenesis, to arrest growth and metastasis of tumours, are promising therapeutical concepts (Gowda, 2005; Markkanen et al., 2005; Huber et al., 2005; Gasparini et al., 2005). Angiogenesis occurs in a characteristic multi-step cascade of migration, proliferation, differentiation and three-dimensional organisation of endothelial cells to generate new vessels with an internal lumen. Angiogenesis as well as antiangiogenesis are regulated by soluble factors, which may influence endothelial cells in the different stages of the angiogenic cascade (Augustin, 2003). Quantification of angiogenesis and antiangiogenesis, i.e. their depiction in measurable factors, is a basic requirement for determination of angiogenic or angiostatic effects of a substance. Most quantitative investigations are undertaken in animal models. The most frequently used models are the cornea model, the chorioallantoismembrane (CAM)-model and several skin preparations (Hasan et al., 2004; Bahramsoltani, 2004). It cannot be obviated that these investigations are associated with pain for the animals. Up to now some twoand three-dimensional in vitro models of angiogenesis have been developed (for example: Montesano et al., 1983; Nehls and Drenckhahn, 1995; Hoying and Williams, 1996; Meyer et al., 1997; Peters et al., 2002; Rookmaaker et al., 2005; Wang et al., 2005; Pozzi et al., 2005). However, in these models, the effects of the substances tested were quantified in only a few phases of angiogenesis. The aim of this study was to establish a method to quantify angiogenesis in vitro in order to achieve a replacement and complementary method comprising all stages of the angiogenic cascade. Furthermore, routine accomplishment of quantification should be possible for different investigators with a maintainable effort of time and costs. A Novel Quantitative In Vitro Model of Angiogenesis