Defining and Controlling Axial Nephron Patterning in Human Kidney Organoids with Synthetic Wnt-Secreting Organizers
Current human pluripotent stem cell-derived kidney organoids contain nephron-like structures that lack organotypic patterning. It is thought that during human development, nephrons form their proximal-distal axial polarity in response to collecting duct-derived signals that are absent in kidney organoids. To delineate how nephron polarities establish, we profiled human kidney development by spatial transcriptomic approaches. Our analyses describe a new axial polarity in the nephron and demonstrate that the nephron proximal-distal polarity develops adjacent to a transcriptional boundary in the collecting duct where non-canonical WNT11 is downregulated and canonical WNT9B ligand is upregulated. The nephron region closest to this boundary in turn activates a series of canonical WNT target genes inferring positional nephron identities. To establish whether a canonical WNT source can improve organoid patterning to an in vivo-like state, we bioengineered self-organizing WNT-secreting synthetic organizers. Organizer-coupled kidney organoids respond to WNT ligands by forming expression gradients and developing distal cell identities. Tuning the WNT dose produced nephrons with continuous patterning along the proximal-distal axis. Strikingly, polarized iPSC-derived nephrons directed their distal tubules towards the WNT-source, indicating axial patterning and morphogenetic programs are tuned by WNTs from the synthetic organizers. Our data present a strategy to control organ patterning, build an artificial kidney, and highlights the power of synthetic organizer systems for advancing organoid models.