Renal engineering: Strategies to address the problem of the ureter

Current techniques for making renal organoids generate tis-
sues that show function when transplanted into a host, but they
have no ureter through which urine can drain. There are at
least 4 possible strategies for adding a ureter: connecting to
the host ureter; inducing an engineered kidney to make a
ureter; making a stem cell–derived ureter; and replacement of
only damaged cortex and outer medulla using remaining host
calyces, pelvis and ureter. Here, we review progress. Local
BMP4 can induce a collecting duct tubule to become a ureter;
a urothelial tube can be produced directly from pluripotent
cells, and connect to the collecting duct system of a renal
organoid; it is possible to graft Embryonic Stem (ES) cell-
derived ureters into host kidney rudiments and see connection,
smooth muscle development and spontaneous contraction, but
this has not yet been achieved with all components being
derived from ES cells. Remaining problems are discussed.