Mechanical environments shape kidney branching morphogenesis in 3D culture

Complex tissue-level organization achieved during development is critical for organ function. Mammalian kidneys rely on a branched urinary collecting duct tree that organizes thousands to millions of nephrons that are responsible for filtering blood. These structures develop by branching morphogenesis, which gives rise to the urinary tubule tree and nephrons. Defects that occur during this branching process result in aberrant tissue morphology and functional deficiencies after birth. My thesis aims to understand the interplay between tissue-level organization and mechanics during kidney development using a novel 3D culture technique. Tissue-level dynamics are often modeled in air-liquid interface (ALI) culture, which flattens and distorts the explant. To overcome this challenge, I first developed a 3D kidney culture method compatible with live imaging by suspending explants in hydrogel droplets. First, I hypothesize that a 3D encapsulating hydrogel environment would preserve organ architectures and in vivo-like tubule distribution that are not preserved in ALI culture. These are validated by quantifying tubule tip-tip distancing and dynamic rotation measured by live imaging. Next, I hypothesize that the mechanical properties of the embedding matrix influence explant development outcomes. By embedding explants in biological and synthetic hydrogel materials with tunable properties, I demonstrate that both matrix stiffness and adhesive properties independently contribute to kidney shape and nephrogenesis balance (number of nephrons per tip). Ongoing study is focusing on tracking and characterizing the cortical stromal cells as a potential translator between the external mechanical environment and nephrogenesis decisions. This work presents new systems for tracking and evaluating 3D kidney morphogenesis through live imaging and investigating the effect of genetic and mechanical perturbations on ex vivodevelopment.