Figure 4.

Construction of tissue‐like structures composed of layers of alternative cell types. The presentation of a solid porous scaffold as a membrane provides a suitable platform to construct layers of alternative cell types. Many types of tissue are composed of alternate layers of cells and such tissue architecture can be replicated by seeding cells sequentially onto supporting porous scaffolds. (A) An example of two cell types: those in blue were seeded first and allowed to grow and establish a 3D culture inside the scaffold; those in green were seeded second onto the surface of the scaffold to establish a 3D layer on top. (B) Example of a human skin construct produced by first seeding human primary dermal fibroblasts into a 200‐μm‐thick porous polystyrene scaffold for 7 days, followed by seeding human primary keratinocytes onto the surface and maintaining the culture for a further 21 days at the air–liquid interface. The skin construct matures over time in culture consisting of differentiated epidermal (epi) and supporting dermal (der) components. Scale bar: 50 μm. (Image courtesy of N. Robinson, Durham University).