Inhibitory Effects of Epithelial Cells on Fibrosis Mechanics of Microtissue and Their Spatiotemporal Dependence on the Epithelial-Fibroblast Interaction

Cell-generatedcontraction forceis the primary physical drivefor fibrotic densification of biological tissues. Previous studiesusing two-dimensional culture models have shown that epithelial cellsinhibit the myofibroblast-derived contraction force via the regulationof the fibroblast/myofibroblast transition (FMT). However, it remainsunclear how epithelial cells interact with fibroblasts and myofibroblaststo determine the mechanical consequences and spatiotemporal regulationof fibrosis development. In this study, we established a three-dimensionalmicrotissue model using an NIH/3T3 fibroblast-laden collagen hydrogel,incorporated with a microstring-based force sensor, to assess fibrosismechanics. When Madin-Darby canine kidney epithelial cellswere cocultured on the microtissue's surface, the densification,stiffness, and contraction force of the microtissue greatly decreasedcompared to the monocultured microtissue without epithelial cells.The key fibrotic features, such as enhanced protein expression of & alpha;-smooth muscle actin, fibronectin, and collagen indicatingFMT and matrix deposition, respectively, were also significantly reduced.The antifibrotic effects of epithelial cells on the microtissue weredependent on the intercellular signaling molecule prostaglandin E2(PGE2) with an effective concentration of 10 & mu;M and their proximityto the fibroblasts, indicating paracrine cellular signaling betweenthe two types of cells during tissue fibrosis. The effect of PGE2on microtissue contraction was also dependent on the time point whenPGE2 was delivered or blocked, suggesting that the presence of epithelialcells at an early stage is critical for preventing or treating advancedfibrosis. Taken together, this study provides insights into the spatiotemporalregulation of mechanical properties of fibrosis by epithelial cells,and the cocultured microtissue model incorporated with a real-timeand sensitive force sensor will be a suitable system for evaluatingfibrosis and drug screening.

Automated summary

Cell-generated contraction force is the primary physical drive for fibrotic densification of biological tissues. Epithelial cells inhibit the myofibroblast-derived contraction force through the regulation of the fibroblast/myofibroblast transition. However, the mechanical consequences and spatiotemporal regulation of fibrosis development remain unclear.