Engineering Tissue Patterning: Rules Governing Gene Expression Patterning and Compartment Boundary Formation in vitro

Engineered bioartificial tissues represent one possible solution for overcoming the devastating shortage of organs and tissues, which causes hundreds of Canadian deaths every year. Despite considerable efforts however, the promise of bioengineering complex solid organs, such as liver and kidney, remains unfulfilled partly due to the challenges of organizing multiple cell components comprising such tissues ex vivo. One promising avenue of designing biomimetic tissues with improved organization is recapitulating certain aspects of developmental biology. In an embryo, cells within a developing tissue are commonly organized in a process of tissue patterning. During tissue patterning, expression of certain key genes is spatially patterned in initially naïve cells, leading to the formation of distinct phenotypic cell domains. Following this patterning process, separation of cells from distinct phenotypic domains is commonly ensured by implementation of compartment boundaries. To successfully recapitulate tissue patterning ex vivo therefore, it is important to study the rules governing gene expression patterning and boundary formation in vitro. In this work the question of how tissue pattering can be engineered in vitro is explored. This thesis describes methodology for patterning gene expression in vitro, outlines design principles governing generation of gene expression patterns with sharp interfaces, and explores the rules governing compartment boundary formation in vitro. The work presented here suggests that simply spatially controlling cell organization at the stage of developing an engineered tissue is not sufficient. Instead, to obtain multicomponent tissues with organizational stability it is necessary to incorporate long-term instructive cues into the design of bioartificial tissues.Ph.D