Developing microtissue-building toolbox to study biophysical effects at multiple scales

Despite the widely acknowledged notion that biophysical properties of the microenvironment are integral in maintaining tissue homeostasis or disease development, it is still technically challenging to study cell dynamics in vitro, with well-defined biophysical parameters such as geometry, stiffness, porosity, micro-organization of the extracellular matrix, and water permeability. We have developed a toolbox to grow microtissues with desired biophysical parameters described above. First, we can combine 3D printing and soft lithography to form epithelium-lined channels with varied radii at sub-100 µm scale. Secondly, we can apply micro-molding techniques and modulate polymer swelling to form capillary-like structures. Third, by using stereolithography to crosslink photo-curable, cell-laden biopolymers such as functionalized gelatin, alginate or collagen, we can fabricate micro-tissues with specific porosity, stiffness and shapes. Fourth, we have devised a self-induced rolling membrane platform, where rectangular thin elastic films are rolled cylindrically by strain mismatching between the two sides of the film, to study the effect of continuum curvature on subcellular organization in the epithelium.Using the toolbox, we are able to build microtissues and made following observations: E-cadherin and ZO-1 expression in the epithelium varies depending on the curvature; cortical actin assembly is associated with tissue geometry and cell-cell adhesion; the steady-state response of the epithelium to hydrostatic pressure perturbations is independent of ECM elasticity but dependent on its porosity and its extent of crosslinking.