Exploring epithelial cell response and engineered microbial therapeutics in the mitigation of radiation-induced gastrointestinal injury

Abstract

As a cornerstone of cancer treatment, over half of all cancer patients will receive radiation therapy at some point in their treatment course. However, the gastrointestinal tract (GIT) is particularly vulnerable due to its high cellular turnover, often resulting in gastrointestinal toxicity that compromises patient quality of life and limits the efficacy of abdominal and pelvic radiotherapy. This thesis aimed to investigate the biological effects of ionizing radiation on the GIT using a multi-model approach and to establish future therapeutic strategies involving genetically engineered probiotics. First, mice underwent whole-body exposure to X-rays (0.1–3 Gy) which revealed acute structural and microbial disruptions within the gut 48 hours post-irradiation. At 3 Gy, significant crypt loss, goblet cell depletion, and increased goblet cell size were observed in the ileum. Radiation-induced shifts in microbial composition were observed across doses and gut regions, underscoring the microbiome's sensitivity to radiation. Next, the effects of the immune-regulated growth factor amphiregulin (AREG), were evaluated in-vitro in HIEC-6 and Caco-2 intestinal epithelial cell lines following radiation. While AREG enhanced cell density at plateau in Caco-2 cells, it did not significantly alter other outcomes, suggesting a potential role in epithelial recovery rather than direct radioprotection. Finally, to advance microbial-based interventions, a dual-origin shuttle vector system was successfully developed for Lactobacillus reuteri, enabling high-efficiency transformation and robust gene expression. An optimized electroporation protocol and P32-driven promotor established a modular platform for future delivery of therapeutic clones. Together, these findings present a comprehensive analysis of radiation induced bowel injury across biological models and introduce a translational pipeline for evaluating microbial-based therapies. This work establishes a foundation for integrated analysis of engineered probiotics as mitigation strategies in radiation-induced gut toxicity.