Embryonic Stem Cells Derived Kidney Organoids as Faithful Models to Target Programmed Nephrogenesis.

The kidney is a complex organ that is comprised of thousands of nephrons developing through reciprocal inductive interactions between metanephric mesenchyme (MM) and ureteric bud (UB). The MM undergoes mesenchymal to epithelial transition (MET) in response to the signaling from the UB. The secreted protein Wnt4, one of the Wnt family members, is critical for nephrogenesis as mouse Wnt4-/- mutants fail to form pretubular aggregates (PTA) and therefore lack functional nephrons. Here, we generated mouse embryonic stem cell (mESC) line lacking Wnt4 by applying the clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated systems 9 (Cas9). We describe here, differentiation of the wild type and Wnt4 knockout mESCs into kidney progenitors, and such cells induced to undergo nephrogenesis by the mouse E11.5 UB mediated induction. The wild type three-dimensional (3D) self-organized organoids depict appropriately segmented nephron structures, while the Wnt4-deficient organoids fail to undergo the MET, as is the case in the phenotype of the Wnt4 knockout mouse model in vivo. In summary, we have established a platform that combine CRISPR/Cas9 and kidney organoid technologies to model kidney development in vitro and confirmed that mutant organoids are able to present similar actions as in the in vivo studies.