Human internal thoracic artery (HITA) ring assay: A new ex vivo human angiogenesis model

Objective: Angiogenesis is defined as newly formed vessels from pre-existing blood vessels. It plays a key role in different diseases such as tumor growth, metastasis, and is involved in the re-vascularization of ischemic tissues. Therefore, we established a new ex vivo angiogenesis model using rings from human internal thoracic artery (HITA) obtained during coronary bypass procedures. Material and Method: HITA rings of 60 patients were embedded between two layers of collagen gel and incubated with basal medium containing 10% FCS. After 3–4 days, the medium was replaced by basal medium containing 5% FCS and the rings were treated with pro-angiogenic factors such as vascular endothelial growth factor (VEGF, 50 ng/ml), fibroblast growth factor (FGF-2, 25 ng/ml) and anti-angiogenic factor endostatin (600 ng/ml) individually or in combination. Results: A moderate capillary outgrowth was observed by incubation of the rings with only basal medium containing 5% FCS after 4–7 days of culture. Capillary like sprouts were grown into the collagen gel within the lumen as well as in the outside of rings. An extensive capillary outgrowth was induced by VEGF. This was inhibited by VEGF plus endostatin. Newly formed capillaries were also visualized immunohistochemistically on paraffin sections and studied by electron microscopy. Conclusion: In summary, the HITA ring assay serves an easy and effective ex vivo model to study mechanisms of angiogenesis and vascular morphogenesis based on human tissue and factors.