In vivo Tube Assay: An Optimised Protocol of the Directed in vivo Angiogenesis Assay by Implementing Immunohistochemistry

BACKGROUND: Angiogenesis, the formation of new blood vessels, is an essential process under physiological and pathological conditions. METHOD: Here, we improved the directed in vivo angiogenesis assay (DIVAA®) test, which is based on the usage of small Matrigel-filled tubes that are implanted into mice subcutaneously for a period of up to 15 days. The subsequent ex vivo assessment of neoangiogenesis within the silicon tubes is then achieved by fluorometry. RESULTS: We showed that the immunohistochemical quantification of the ingrowth of endothelial cells, based on CD31, was superior to the fluorometric quantification advised in the manufacturer's instructions. We optimised the explantation procedure, ensuring the complete recovery of the ingrown vessels. Using this modified protocol, we investigated the effect of the length of stay of the implanted tubes as well as of the concentration of the growth factors VEGF and FGF on the assay. CONCLUSION: Our improved protocol offered an effective and reliable alternative to the original assay, which is expected to facilitate in vivo research on angiogenesis and, thus, might drive the development of novel therapeutic agents.