Assembly of a Functionally Mature Synthetic Kidney Organoid with Spatial Patterning from the Self-Organization of Expandable Kidney Progenitors

Background: The prospect of utilizing stem cells to rebuild a kidney holds great promise as an alternative organ source for kidney transplantation. During kidney development, nephron progenitor cells (NPCs) give rise to the nephrons, and ureteric progenitor cells (UPCs). We have previously established systems to expand mouse and human NPCs and UPCs. Here we investigate whether we can assemble a functionally mature synthetic kidney organoid with patterned and interconnected nephrons to the collecting ducts from expandable NPCs and UPCs. Methods: Culture conditions were tested to enhance the natural reciprocal interactions between NPCs and UPCs. The resulting synthetic kidney organoids were characterized in a time-course manner and compared to the native kidney development. Single-cell multiome, and physiological assays were performed to characterize the development and functionality of the synthetic kidney organoids. Results: Under optimal culture conditions, we assembled synthetic kidney organoids from expandable NPCs and UPCs. Synthetic kidney organoids can recapitulate the major developmental stages of the native kidney in vitro as that in vivo: NPCs undergo the subsequent stages of nephrogenesis before forming around 150 well-segmented nephrons; UPCs undergo dramatic branching morphogenesis, eventually forming a central collecting duct system interconnected to the distal ends of the nephrons formed from the NPCs. snRNA-seq and snATAC-seq confirmed the formation of all major nephron and collecting duct cell types with a transcriptome comparable to a postnatal kidney. Surprisingly, the major kidney stromal cell types are also formed, in a mechanism that involves the plasticity of a subset of NPCs adopting interstitial progenitor cell fate, the third kidney progenitor cell type that gives rise to the kidney stromal cells. Functional assays validate the renal epithelia's physiological and major endocrine roles similar to the native kidney. Upon transplantation, the synthetic kidney organoids are properly vascularized and produce primitive urine. Conclusion: The generation of a functionally mature, and spatially organized synthetic kidney organoid model represents a major step toward the development of transplantable synthetic kidneys, and other therapeutic modalities. Funding: NIDDK Support - NIDDK Support, NIDDK Support, Private Foundation Support