The skeletal muscle, small intestines, and brain tissues were treated with 4% paraformaldehyde at 4°C for 24 h. Then, the tissues were embedded in paraffin (Beyotime Biotech.) and cut into sections 4 μm thick. Tissue slices were subsequently de-paraffinized as previously described [23 ]. The tissue sections were used for HE staining assay as previously described [24 (link)]. Briefly, the above tissue sections were stained with hematoxylin for 10 min, followed by eosin staining for 30 s. Both hematoxylin and eosin staining were conducted at room temperature. The stained sections were imaged with an inverted fluorescence microscope (Model IX70; Olympus, Tokyo, Japan) and analyzed using the Medical Image Analysis System (HMIAS22000; Wuhan Champion Image Technology Co., Ltd., Wuhan, China).