Changes in organoid morphology after infection with H9N2 virus. Intestinal organoids from mouse small intestines were seeded into Matrigel and cultured for 72 h to obtain well-developed organoids. Organoids were treated with medium, H9N2 virus, or TNF-α (100 ng/mL). A Crypt morphology was assessed by light microscopy. B Annexin V–PI double staining was performed to differentiate cells in early apoptosis (Annexin V + , PI −) from those in late apoptosis (Annexin V + , PI +). C, D EdU incorporation (2 h) in organoids cultured in the presence of intestinal organoids. The results are representative of data from three independent experiments. Each data bar shown represents mean values ± SE of triplicate assays. *P < 0.05; **P < 0.01. Bars: 20 μm (A). Bars: 50 μm (C).