Five-mm segments of proximal and distal colon were resected and fixed in 10% neutral buffered formalin for histological examination as described previously (57 (link)). Briefly, tissues were embedded in paraffin wax, sectioned into 4-μm-thick sections with a paraffin microtome (ThermoFisher), and mounted on microscope slides (Fisher Scientific). Dewaxed sections were stained with H&E (Richard Alen Scientific). Histological images were obtained using a Zeiss Axio Observer microscope with an Olympus DP72 camera (Zeiss).