The morphogenetic patterning that generates three-dimensional (3D) tissue structures requires dynamic concerted rearrangements of individual cells with respect to each other. In vivo models are difficult to manipulate and visualize, rendering them essentially intractable for mechanistic analysis of cellular dynamics during mammalian tissue development. We have used a lithography-based approach to develop 3D culture models¹ that recapitulate the architecture of epithelial ductal trees, enable micrometer-resolution control of tissue geometry and microenvironment, and provide quantitative 4D data in a physiologically relevant context. The engineered ducts execute a complete series of morphogenetic events and recapitulate many of the features observed during morphogenesis in vivo. Here we use time lapse spinning disk confocal microscopy to examine the motility of individual cells within hundreds of engineered ducts continuously over 24-48 hours to elucidate the cellular dynamics that governs normal tissue morphogenesis. This analysis has revealed complex social interactions between the epithelial cells comprising the duct both before and after the cells invade the surrounding extracellular matrix. By tracking every individual cell in 3D and quantifying speed and trajectory, we have determined that the population undergoes extensive reorganization based in part on quantitative differences in the expression levels of matrix metalloproteinases, matrix-degrading enzymes found to be critical for normal invasion and morphogenesis.

1. Nelson, C. M.; Vanduijn, M. M.; Inman, J. L.; Fletcher, D. A.; Bissell, M. J., Tissue geometry determines sites of mammary branching morphogenesis in organotypic cultures. Science 2006, 314, (5797), 298-300.