Immunofluorescence microscopy of the jejunum was performed as previously described with minor modifications.11 (link) For immunohistochemistry, tissues were fixed in 4% paraformaldehyde/PBS for 1 hour 20 minutes at 4°C prior to dehydration overnight in 20% sucrose/PBS at 4°C. The tissues were cut and placed into Tissue-Tek Crymold (Sakura Finetek, Torrence, CA, USA) containing one part Tissue-Tek OCT Compound (Sakura Finetek) and one part 20% sucrose/PBS prior to flash freezing with liquid nitrogen. Embedded molds were sectioned with a cryostat at 8 μm thickness onto glass slides and stained with primary antibodies for SRF (1:100, Cat No: sc-13029; Santa Cruz Biotechnology, Dallas, TX, USA), Ki67 (1:100, Cat No: RM-9106-S0; Thermo Scientific, Fremont, CA, USA) overnight at 4°C followed by staining with the secondary antibody Alexa Fluor 594-Conjugated AffiniPure Donkey Anti-Rabbit IgG (1:500, Cat No: 711-585-152; Jackson Immuno Research, West Grove, PA, USA) for 1 hour at room temperature prior to mounting onto slides with 4,6-diamidino-2-phenylindole (DAPI)-Prolong Gold (Cat No: P36931; Invitrogen, Carlsbad, CA, USA). Images were collected using the Fluoview FV10-ASW 3.1 Viewer software (Olympus, Tokyo, Japan) with an Olympus FV1000 confocal laser scanning microscope.