Spatial Control of Epithelial Tissue Collective Behavior

Abstract

Epithelial tissues are crucial for maintaining organ compartmentalization and act as protective barrier functions, thus were essential for the evolution of multicellular life. Their self-healing tendency through collective cell migration is the principle behind the key feature of epithelial tissues. The coordinated motion of cells is pivotal to close wounds caused by trauma or diseases such as diabetes or vascular insufficiency, as well as drive complex developmental processes. Modulating this collective migration can help us to better engineer tissue and treat injuries.Here, I investigated two different tools, micropatterned protein and optogenetics, as means to spatially control collective migration of the epithelial tissues. In first project, Madin-Darby Canine Kidney (MDCK) epithelial tissue was grown on a biphasic (half-ECM half-Ecadherin) substrate, and the tissue behaviors on both sides were compared. Tissue on the Ecadherin side moved and divided slower. Reduced migration and proliferation positioned the tissue into fluid-like, but non-motile (low-fluctuation) phase. Lack of focal adhesion formation on Ecadherin substrate was a key biological mechanism behind all the observed phenomena. In second project, I used optogenetics to enable spatiotemporal control of tissue mobility. OptoEGFR gene was expressed in the Retinal Pigment Epithelial (RPE) cells. When the OptoEGFR RPE cells were exposed to blue light, they activated their EGFR signaling pathway. Via local activation of EGFR caused by the illumination, I could induce two different migration patterns in the RPE monolayer. Inner illumination generated converging migration of the cells toward the illumination and illumination of expanding tissue sped up the outgrowth velocity. With the inhibitor assay, PI3K pathway was determined as the key regulator of these migration. Applying these two rules of light-guided migration, we could custom design the RPE tissue with sophisticated illumination pattern. Through this work, I could confirm the validity of these tools as the methods of spatial control of monolayer tissue collective migration. Expanding these methodologies to 3D tissues is left as a future work.