Using embryonic stem cell-derived ureteric buds for ureter engineering and developing methods to connect them to host kidneys in culture

Abstract

Chronic renal disease is a global health care burden that has a high mortality rate. The only cure available is either life-long renal dialysis or to replace the damaged organ using human donor kidneys which have significant issues including availability and long-term rejection. Scientists have developed an increasing interest in producing lab-grown kidneys and hope that they can, one day, solve the organ transplantation problem. Recent techniques generate renal tissue but contain no ureter, which is required before engineered kidneys be of any use. In this thesis my aim was to engineer ES cell-derived ureters that could be connected to these kidney organoids. Mouse ES cells were differentiated into ureteric bud tissue using a stepwise protocol. ES cell-derived engineered ureteric buds (eUBs) were grafted into isolated fetal mouse kidneys in culture. The GFP-eUBs grafted into the cortex of embryonic kidneys showed branching and encouraged nephron formation. If placed in the peri-Wolffian mesenchyme, either attached to a kidney or independent, they showed no branching but made multilayer, uroplakin-positive urothelium and induced the mesenchyme to differentiate into a contractile smooth muscle.

These eUBs formed collecting ducts with a ureter when grafted between the two kidney mesenchymes. Furthermore, the isolated ES cell-derived eUBs could be encouraged to connect to the host kidneys in culture using a simple mechanical technique (an incision in the wall of the host epithelium at the engraftment site). The results also show that connection is possible in older kidneys in culture, and those connected to ureters show rhythmic contractions.

This work introduces new possibilities for renal regeneration and tissue engineering.