Toxicological Analysis by Assessment of Vascularization and Cell Viability Using the Chicken’s Chorioallantoic Membrane (CAM Assay)

Abstract

The chorioallantoic membrane (CAM) assay is an increasingly popular method using a hen's egg as an experimental organism. Animal models have been established in scientific research for centuries. Yet, awareness of animal welfare in society rises, and the transferability of findings obtained in rodentmodelsto human physiology is challenged. Thus, using fertilized eggs as an alternative platform for animal experimentation might be a promising alternative. The CAM assay is utilized for toxicological analysis by determination of CAM irritation as well as analysis of organ damage and ultimately death of the embryo. Furthermorethe CAM provides a micromilieu suited for the implantation ofxenografts. Xenogene tissues and tumors grow on the CAM due to a lack of rejection by the immune system and a dense vascular network providing oxygen and nutrients. Multiple analytical methods including in vivo microscopy and various imaging techniques are applicable to this model. Additionally, ethical aspects, a comparatively low financial burden, and low bureaucratic hurdles legitimize the CAM assay.We here describe anin ovo modelutilized for xenotransplantation ofa human tumor. The model can be used to evaluate the efficacy as well as the toxicity of different therapeutic agents afterintravascular injection. Additionally, we presentthe evaluation of vascularization and viability by intravital microscopy, ultrasonography, and immunohistochemistry.