Assays of Angiogenic Potential Using Quail and Chicken Chorioallantoic Membrane (CAM)

Angiogenesis is crucial in tissue repair, wound healing, and embryo development. Maintaining a balance between pro‐angiogenic and anti‐angiogenic factors is crucial for tissue homeostasis, thereby preventing the development of pathological conditions. In addition, the tissue microenvironment constantly influences molecular signaling, potentially altering this delicate balance. The chorioallantoic membrane (CAM) assay has emerged as a dynamic, cost‐effective, and ethically favorable alternative for studying angiogenesis. This work presents a detailed and accessible approach to the CAM assay, focusing on the evaluation of the angiogenic potential of applied stimuli (such as conditioned media, extracellular vesicles, or bioscaffolds) through various techniques, including hematoxylin and eosin, PicroSirius Red, Alcian Blue, and resorcin‐fuchsin staining; immunofluorescence; immunohistochemistry; and scanning electron microscopy (SEM). Our protocol uses the in ovo CAM assay approach, utilizing a simple incubator setup that eliminates the need for expensive equipment. The primary objective is to provide a comprehensive methodology for researchers to efficiently analyze angiogenesis, offering insights into vessel morphology and protein expression. The experiment comprises three major steps: (1) egg opening, stimulation, and sample collection; (2) histological processing and paraffin blocking; and (3) microscopic analyses. The first and second procedures take approximately 15 days, after which each analysis can be conducted whenever the researcher judges appropriate. The expected results include several types of data concerning the proliferation rate, vessel presence and integrity, measurement of angiogenic‐specific proteins, and investigation of structural proteins.