Abstract
Background In vivo studies of high dose radiation-induced crypt and intestinal stem cell (ISC) loss and subsequent regeneration are typically restricted to 5–8 days after radiation due to high mortality and immune failure. This study aimed to develop murine radiation models of complete crypt loss that permit longer-term studies of ISC and crypt regeneration, repair and normalization of the intestinal epithelium.MethodsIn C57Bl/6J mice, a predetermined small intestinal segment was exteriorized and exposed to 14Gy-radiation, while a lead shield protected the rest of the body from radiation. Sham controls had segment exteriorization but no radiation. Results were compared to C57Bl/6J mice given 14 Gy-abdominal radiation. Effects of elemental liquid diet feeding from the day prior to radiation until day 7 post-radiation were assessed in both models. Body weight and a custom-developed health score was assessed every day until day 21 post-radiation. Intestine was assessed histologically.ResultsAt day 3 after segment radiation, complete loss of crypts occurred in the targeted segment, while adjacent and remaining intestine in segment-radiated mice, and entire intestine of sham controls, showed no detectable epithelial damage. Liquid diet feeding was required for survival of mice after segment radiation. Liquid diet significantly improved survival, body weight recovery and normalization of intestinal epithelium after abdominal radiation. Mice given segment radiation combined with liquid diet feeding showed minimal body weight loss, increased food intake and enhanced health score.ConclusionsThe segment radiation method provides a useful model to study ISC/crypt loss and long-term crypt regeneration and epithelial repair, and may be valuable for future application to ISC transplantation or to genetic mutants that would not otherwise survive radiation doses that lead to complete crypt loss. Liquid diet is a simple intervention that improves survival and facilitates long-term studies of intestine in mice after high dose abdominal or segment radiation.
Highlights
Increasing attention has been given to the impact of radiation on the gastrointestinal (GI) tract due to concerns about exposure to radiation after an accident or due to terrorist activity and a need for medical countermeasures [1,2]
Tissue was harvested for histology at 3 days after segment radiation, a time known to be associated with complete loss of crypts following 14 Gy radiation in high dose Total Body Irradiation (TBI) or abdominal radiation models [11], to validate specific localization of the damaged zone and that radiation induced complete loss of crypts, and at 21 days after radiation, a time later than typically analyzed after high dose radiation, to study epithelial normalization
Intestinal tissues were collected at day 3 post-radiation, time associated with complete crypt ablation in jejunum after 14 Gy abdominal radiation [11]
Summary
Increasing attention has been given to the impact of radiation on the gastrointestinal (GI) tract due to concerns about exposure to radiation after an accident or due to terrorist activity and a need for medical countermeasures [1,2]. The GI epithelium is one of the most highly proliferative tissues in the body with constant renewal of the epithelial lining occurring over 3–10 days depending on the species and the region of the GI tract. Radiation induces DNA damage which, when radiation dose is sufficiently high, leads to death of a majority of cells within the crypt, and subsequent loss of villi and severe damage to intestinal epithelium. In vivo studies of high dose radiation-induced crypt and intestinal stem cell (ISC) loss and subsequent regeneration are typically restricted to 5–8 days after radiation due to high mortality and immune failure. This study aimed to develop murine radiation models of complete crypt loss that permit longer-term studies of ISC and crypt regeneration, repair and normalization of the intestinal epithelium
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