CONTROLLING A CELLULAR NICHE IN SCAFFOLD DESIGNS FOR EPITHELIAL TISSUE ENGINEERING - Intelligent Scaffolds for Tissue Engineering and Regenerative Medicine - page 458

The purpose of scaffolds either for in vitro or in vivo applica-
tions of engineered epithelia is to allow restoration of the natural
functions of these tissues. Scaffolds should be soft enough to limit
mechanical tension to cells so that the cells are not stretched and
forced to exhibit a mesenchymal morphology. Ideally the scaffold's
mechanical properties are tunable to cater to subtle variations in
mechanical requirements of different epithelial tissues. Scaffolds
should also be macroporous even in hydrated states such that in
ex vivo bioreactors and applications a certain range of fluidic shear
can be introduced and for in vivo implant applications vasculature
infiltration can occur. Scaffold-cell interfaces should have nanosized
features, be easily modified with different chemical ligands to react
with receptors on cellular surfaces, and be controllable spatially,
suchthatthecellsexperiencecuesthatrestoretheirnaturallypolar-
ized structures and functions.
Over the past decade, we and other groups have developed a
range of cell culture technologies to individually control the extra-
cellular microenvironments of epithelial tissues, such as the devel-
opment of elastomeric biodegradable materials for esophagus, 3
hydrogels for three-dimensional (3D) presentation of the growth
factors, 4 , 5 sandwich cultures for spatial presentation of polarity
cues, 6 andmicrofluidicdevices torecapitulate themechanical shear
of the liver. 7 Here we aim to summarize some of these individual
efforts to control the microenvironments of the tissue-engineered
epithelia.Wealsointroduceeffortstodevelopscaffoldmaterialsand
constructs that combine these considerations to potentially yield
future generations of tissue-engineered epithelia whose functions
can match those of native epithelia for specific applications in vitro
and in vivo .
24.2 Native Extracellular Microenvironment
for Epithelial Cells
Epithelial tissue covers the whole internal and external surface of
thebody.Itismadeupofoneormorelayersofepithelialcells.These
cellsadheretightlywithlittleornointercellularsubstance.Basedon
the cell morphology and spatial organization, epithelial tissues can