Fig. 6.

Enteroendocrine cells support Lgr5⁺ crypt stem cells on Paneth cell ablation. Immunostaining (A, A′, B, and B′), smFISH (C and D), and TEM analysis (E and F) to detect synaptophysin⁺ enteroendocrine cells in jejunum sections from pLys^DTR KI mice DT-treated for 6 consecutive days (B, D, and F) and untreated pLys^DTR KI mice (A, C, and E) at 16 h after the last DT injection. The synaptophysin⁺ enteroendocrine cells could be detected in the TA zone of the crypt and on the villi (A, A′, and C), while in the DT-treated pLys^DTR KI mice, the synaptophysin⁺ enteroendocrine cells were intermingled with Lgr5⁺ intestinal stem cells at the bottom of the crypt (arrows in B, B′, and D). Quantification revealed the presence of 0.89 enteroendocrine cells per crypt in a single section (counted: 600 crypts per mouse; n = 3). In contrast to the untreated control pLys^DTR KI mice (E, white arrows marking Paneth cells [P]), TEM analysis confirmed the presence of enteroendocrine cells (ee) (F, white arrows) at the bottom of the crypt after DT-mediated Paneth cell ablation. (Scale bars: 100 µm.)