During radiotherapy, microenvironments neighboring the tumor are also exposed to gamma irradiation; this results in unexpected side effects. Blood vessels can serve as microenvironments for tumors and they play an important role in providing nutrients to tumors. This is mostly related to tumor progression, metastasis, and relapse after therapy. Many studies have been performed to obtain a better understanding of tumor vasculature after radiotherapy with in vitro models. However, compared to 3-D models, 2-D in vitro endothelial monolayers cannot physiologically reflect in vivo blood vessels. We previously remodeled the extracellular matrix (ECM) hydrogel that enhanced the tight barrier formation of 3-D blood vessels and the vascular endothelial growth factor (VEGF) gradient induced angiogenesis in a microfluidic device. In this study, the blood vessel model is further introduced to understand how gamma irradiation affects the endothelial monolayer. After the gamma irradiation exposure, we observed a collapsed endothelial barrier and a reduced angiogenic potential. Changes in the cell behaviors of the tip and stalk cells were also detected in the angiogenesis model after irradiation, which is difficult to observe in 2-D monolayer models. Therefore, the 3-D in vitro blood vessel model can be used to understand radiation-induced endothelial injuries.
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