Fasting protects mice from lethal DNA damage by promoting small intestinal epithelial stem cell survival

Short-term fasting protects mice from lethal doses of chemotherapy through undetermined mechanisms. Herein, we demonstrate that fasting preserves small intestinal (SI) architecture by maintaining SI stem cell viability and SI barrier function following exposure to high-dose etoposide. Nearly all SI stem cells were lost in fed mice, whereas fasting promoted sufficient SI stem cell survival to preserve SI integrity after etoposide treatment. Lineage tracing identified multiple SI stem cell populations, marked by Lgr5, Bmi1 or HopX expression, that contributed to fasting-induced survival. DNA repair and DNA damage response genes were elevated in SI stem/progenitor cells of fasted etoposide-treated mice, which importantly correlated with faster resolution of DNA double strand breaks and less apoptosis. Thus, fasting preserved SI stem cell viability as well as SI architecture and barrier function suggesting that fasting may reduce host toxicity in patients undergoing dose intensive chemotherapy. Intestines were harvested 3 h post-etoposide injection, flushed with PBS, and then flushed with ice-cold Methacarn (60% methanol, 30% chloroform, 10% acetic acid) to fix the tissue while preserving RNA integrity. Fixed intestines were rinsed with 70% ethanol, embedded in 2% agar followed by paraffin embedding. Sections were deparrafinized and dehydrated through xylene and an increasing gradient of ethanol. Laser capture microdissection was performed using the Acturus PixCell IIe, with the following settings: spot size power 80, duration 1 ms, repeat 0.2 s, target 0.150 V, current 1.82 mA. RNA was isolated from the CapSure HS LCM Caps (Applied Biosystem) using the PicoPure RNA Isolation kit (Applied Biosystems). All RNA samples were treated with DNaseI (Qiagen). Four biological replicates were used for each of the following treatments: Fasted Etoposide, Fed Etoposide. Each group had 2 male and 2 females samples. 4-6 week old Lgr5EGFP-IRES-CreERT2/+ mice were dosed with 80mg/kg etoposide (i.v.).