Animal models

Animal models

For acute colitis, 6-week-old male C57BL/6J mice (InVivos, Singapore) were grouped randomly and given 3.5% DSS (colitis grade, 36 to 50 kDa, MP Biomedicals, USA) in drinking water for 7 days. After 3 days, mice were euthanized for further investigation. B-mEVs were orally administered to mice for 1 week before DSS feeding. Chronic colitis was induced by intermittent administration of 3.5% DSS. Body weight and DAI (body weight loss, stool consistency, and bleeding) were assessed in both acute and chronic models of colitis. For different colitis models, mice were divided into different groups, including a control group, DSS group (3.5% DSS), DSS + mEVs-L group (3.5% DSS + 0.6 mg/kg/day, low-dose), DSS + mEVs-H group (3.5% DSS + 3.0 mg/kg/day, high-dose) and EV-depleted supernatant group (1.2 mg/kg every day). For NASH, 7-week-old C57BL/6J mice were fed on the MCD diet (MP Biomedicals, USA) for 8 weeks. At 4 weeks of MCD diet feeding, mice were randomly grouped for different treatments. Mice were orally administered with B-mEVs starting at 4 weeks feeding on MCD diet 1.2 mg/kg every other day for 4 weeks. Saline or EV-depleted supernatant (1.2 mg/kg every other day) were used as negative control. In brief, mice were divided into four groups, including a control group, MCD diet group, EV-depleted supernatant group (1.2 mg/kg every day EV-depleted supernatant) and MCD diet + mEVs group (1.2 mg/kg every other day mEVs). Mice were kept on a 12-hour light and dark cycle. All animal experiments were approved by the Institutional Animal Care and Use Committee of the National University of Singapore or Ocean University of China and conformed to the Guide for the Care and Use of Laboratory Animals published by the U.S. National Institutes of Health (NIIH Publication, 8th Edition, 2011).