Generation of multi-lineage kidney assembloids with integration between nephrons and a single exiting collecting duct

A functional kidney requires a patent connection between all nephrons and the collecting duct network to ensure an exit path for the urinary filtrate. While it is now possible to separately direct the differentiation of pluripotent stem cells to nephron-forming or nephric duct-forming populations, the controlled integration of these two systems has not been demonstrated in human. We report the formation of an integrated kidney assembloid via the co-culture of distinct nephric duct progenitor and nephron-forming cultures in the absence of any requirement for cell enrichment. Nephrons within these kidney assembloids connect to a single exiting nephric duct with this connection forming with the early distal nephron prior to nephron segmentation. Using constitutional reporter lines, we show that the nephrons arise from the nephric progenitors and fuse with the nephric duct while the nephric duct progenitors form a single common duct without any branching. The stromal component of the nephric duct progenitor population also contributes to the medullary stroma surrounding the nephrons. Such modular assembloids address the challenge of nephron unification in an engineered kidney tissue model.