Fig. 2

Scanning and transmission electron microscopy of human SMIS. A SEMs display the surface of the spheroids consisting of a fibroblast core, covered by epithelial and goblet cells. Scale bars indicate 2 µM. B Higher magnification of the SEMs, scale bars indicate 1 µM. C Analysis of the surface of human SMIS with only fibroblasts and epithelial cells by SEM. Scale bars indicate 1 µM. D SEMs in higher magnification, scale bars indicate 1 µM. E Transmission electron microscopy of the spheroids consisting of fibroblasts, epithelial and goblet cells to identify membrane protrusions proving microvilli formation. Scale bars indicate 200 nm. F Higher magnification of the TEMs, scale bars indicate 200 nm