Integrating collecting systems in human kidney organoids through fusion of distal nephron to ureteric bud.

Kidneys maintain homeostasis through an array of parallel nephrons, which fuse during development to a system of collecting ducts (CDs), establishing the essential luminal pathway for excretion of metabolic waste. Human kidney organoids derived from pluripotent stem cells (human pluripotent stem cells [hPSCs]) generate nephrons that lack CDs and terminate as blind-ended tubules, limiting their functional potential. Here, we describe a developmentally inspired hPSC differentiation system that addresses this deficiency through assembly of induced nephrogenic mesenchyme with ureteric bud (UB) progenitors, leading to a CD network functionally integrated in kidney organoids through fusion with the distal tubule. The nephron fusion occurs stereotypically and is regulated by proximal-distal nephron patterning, which can be modulated through temporal manipulation of developmental pathways. This work provides a platform for interrogating the principles and mechanisms underlying nephron-UB fusion and a framework for engineering unobstructed nephrons with collecting systems, an important step toward de novo generation of functional kidney tissue.