The chick embryo choriallantoic membrane as a bioassay for angiogenesis factors: reactions induced by carrier materials.

A variety of filter materials, sponges, and gels were placed on the chick chorioallantoic membrane (CAM), the reactions of it investigated and compared with those induced by natural egg materials (white eggshell membrane, coagulated albumen and yolk). Independently of the kind and nature of the naterials the CAM reacted nearly regularly underneath these diverse materials with a proliferation of ectodermal cells, fibroblasts, and blood vessels forming a highly capillarized granulation tissue. The area of the CAM surrounding the foreign materials frequently displayed an increase of small blood vessels macroscopically discernible and showing a radial arrangement (spoke-wheel-appearance according to FOLKMAN 1974). It is concluded that this type of vascular reaction cannot be considered as a characteristic feature for the action of a special tumour angiogenesis factor, since it can be induced by a variety of stimuli leading to an inflammatory reaction in the CAM. For the detection of special angiogenetic activities an objective quantification of the vessel reactions is necessary under consideration of the reactions induced by the mere presence of such foreign materials.