Engineering structure and function of human kidney organoids

About This Grant

PROJECT SUMMARY The kidney is responsible for maintaining an overall state of homeostasis, which it achieves by filtering a large volume of plasma through millions of epithelial units termed nephrons. It is estimated that 1 in 7 adults in the US suffer from chronic kidney disease (CKD), resulting from impairment of these functions. A seminal event in the development of every nephron is the formation of a connection with a collecting duct that establishes a patent pathway for the drainage of fluid into the collecting system and eventually out of the kidney. Human kidney organoids derived from pluripotent stem cells (hPSCs) are an innovative and powerful tool to study renal pathophysiology and to potentially inform new therapeutic avenues, but they suffer from several major limitations. One paramount deficiency is the lack of collecting ducts and failure of their nephrons to drain into a collecting system. To address this problem, we have recently developed a novel platform in which nephrogenic mesenchyme is combined with ureteric bud (UB) progenitor cells to produce an integrated system of collecting ducts within the organoids. Like in vivo development, the nephrons connect with the UB through a controlled fusion event with the distal GATA3+ segment that establishes a continuous passage for fluid flow. Currently, nephron connectivity in this system is limited by a relatively low efficiency of distal specification, and we hypothesize that finetuning the molecular processes underlying fusion will enable more complete integration of nephrons with collecting systems. In this proposal, we will apply this integrated organoid model to address major gaps in our mechanistic understanding of distal nephron patterning and fusion. In Aim 1, we will investigate how WNT and NOTCH signaling interactions coordinate and synergize to control nephron segmentation, and these mechanisms will be applied to enhance nephron-UB fusion in the organoid model. Aim 2 will delineate the cell- autonomous mechanisms underlying distal nephron fusion. Preliminary data show that expression of GATA3 is sufficient to induce fusion-competent distal tubules. Here we will build on this understanding by dissecting the genetic mechanisms downstream of GATA3 and how they regulate this unique cell biological property. Collectively, this work will generate novel and important insights into the mechanisms underlying nephron fusion, and simultaneously it will lead to further advancement in our state-of-the-art organoid model by informing methods to optimize nephron-UB connectivity. We anticipate that these approaches will yield seminal improvements in the structural organization of hPSC-derived kidney organoids, which will translate to progress in the functional capabilities of these tissues and their utility as models for investigation of renal pathophysiology and potentially for developing new therapies for CKD.