Figure 2:

Methods used for exposing human intestinal stem-cell derived models with gut microbes. A) Microinjection is used for introducing microbes into the lumen of 3D organotypic models enabling microbe-epithelium interaction at the apical side. B) Polarity of enteroids in apical out HIEs is reversed by removing surrounding matrix and microbes are added in the outer media providing apical access. C) Dissociated 3D organotypic cultures are mixed with microbial species of interest. Microbes may get incorporated into the lumen or left outside in the matrix of reformed 3D structures. D) Organotypic models can be enzymatically dissociated to form 2D polarized monolayers and microbes can be added either on the apical or basolateral side.