Oxygen-enhanced assembloid-based vascularized intestinal-on-a-chip for radioprotective drug evaluation

The intestine plays essential roles in digestion, immunity, and metabolism, but is highly sensitive to ionizing radiation during cancer treatment or environmental exposure. Although three-dimensional intestinal models more accurately replicate tissue architecture than conventional monolayers, they are frequently limited by insufficient oxygen delivery, leading to hypoxia-associated functional impairment. Incorporating physiologically relevant oxygenation strategies remains a key challenge in advanced in vitro systems. This study aimed to establish a physiologically relevant in vitro intestinal model by improving oxygen mass transfer within three-dimensional tissue constructs, thereby enhancing structural organization and functional maturation, and subsequently applying the system to investigate radiation-related mechanisms and evaluate potential protective agents.

Based on a microengineered 3D cell-assembly platform, intestinal epithelial cells, endothelial cells, and fibroblasts were spatially organized to form a structured intestinal tissue model. The composition of the cells was optimised to improve tissue uniformity and the function of the epithelial barrier. To alleviate hypoxia in the three-dimensional construct, an oxygen-permeable microwell system was employed to enhance oxygen diffusion and promote epithelial differentiation, as evidenced by the upregulation of Isx, Cyp3a5, and Tff3. A vascularized chip that recapitulated the in vivo intestinal-stromal-vascular interface was created by incorporating microvascular networks self-assembled from endothelial cells within a hydrogel matrix.

Following radiation exposure, the model exhibited characteristic symptoms of intestinal injury, such as decreased cell viability, impaired E-cadherin signaling, and compromised epithelial barrier integrity. Treatment with dimethyloxalylglycine (DMOG) mitigated these effects, confirming it's utility for assessing radioprotective drugs.

This vascularized intestinal-on-a-chip model closely mimics the structure and function of the human intestinal microenvironment. It serves as a robust in vitro platform for studying radiation-induced intestinal injury and for screening candidate protective agents, offering valuable applications in radiation protection and regenerative medicine research.