Perfusable 3D models of ureteric bud and collecting duct tubules
Recent protocols have emerged to derive ureteric bud (UB) and collecting duct (CD) organoids directly from human induced pluripotent stem cells (hiPSCs). However, these 3D kidney tissues lack biophysical cues from luminal flow and a drainage outlet. To address these limitations, we have created perfusable 3D models of UB and CD tubules. UB organoids are first generated from hiPSCs followed by their dissociation into individual UB cells. Individual UB cells are then seeded onto a 3D perfusable channel embedded within an extracellular matrix composed of fragmented basement membrane matrix and collagen I, where they self-assemble into a confluent monolayer. During in vitro perfusion, these cells exhibit UB-like marker expression over several weeks, during which they undergo budding akin to early branching morphogenesis in developing kidneys. To further promote network formation, UB cells are bioprinted adjacent to a perfusable UB tubule, which form interconnections through luminal fusion. Finally, these 3D perfusable UB tubules are differentiated into collecting duct tubules under luminal flow. Our platform facilitates fundamental understanding of human collecting duct formation during renal development, while paving the way for using these physiologically relevant models for drug testing, disease modeling, and, ultimately, integration into bioprinted kidney tissues for therapeutic use.