Optimized Colitis and Adenoma Induction

The colitis protocol was based on preliminary toxicity data in the Lgr5-lacZ strain. The standard protocol to induce acute colitis uses 2%–3% DSS for 7 consecutive days dependent on mouse strain sensitivity (84 (link)). As we found approximately 30%–40% of Lgr5-lacZ mice died at day 6 or 7 after DSS treatment because of severe colon damage at ≥2% DSS, we elected to use 1% DSS in drinking water ad libitum (MP Biomedicals or TdB, molecular mass 36–50 kDa) for colitis induction in this strain. Adenoma induction used a standard AOM-DSS protocol (21 (link), 84 (link)) modified as follows: electing a schedule of decreasing DSS dosage to mitigate toxicity, 6- to 8-week-old male Lgr5-lacZ mice were injected intraperitoneally with AOM (MilliporeSigma) at a dose of 12.5 mg/kg body weight and after 5 days were fed 2% DSS in the drinking water for 5 days, followed by 14 days of regular water. This cycle was repeated twice with 1.5% DSS and 1.0% DSS, respectively. Colonoscopy was performed at day 90 on anesthetized mice to check for tumor formation using the Coloview System (Karl Storz). Our data show a single AOM injection does not induce colon tumorigenesis in C57BL/6J mice (data not shown) (40 (link), 85 (link), 86 (link)).