What are the limitations of chick chorioallantoic membrane (CAM) angiogenesis assay?

The primary limitation of chick chorioallantoic membrane (CAM) angiogenesis assay is that it induces a nonspecific inflammatory reaction. This may develop as a result of grafting and induce a secondary vasoproliferative response. Thus, the quantification of the primary response is disrupted. Inflammatory angiogenesis, in which macrophages or leukocytes are the source of angiogenic factors, cannot be distinguished from direct angiogenic activity without a histological study of several positive and negative controls. Other limitations are that there is a short observation period and there is a risk of angiogenesis induced by technical errors. Additionally, the chicken-origin of the assay limits availability of other reagents. It also contains a highly-developed vascular network, which makes it hard to distinguish between new capillaries and pre-existing ones. CAM also goes through rapid changes morphologically and in the change in the rate of endothelial cells during proliferation throughout embryonic development. Lastly, there are also differences in the drug metabolism with mammals.