Engineering kidney developmental trajectory using culture boundary conditions.

Kidney explant cultures are traditionally carried out at air-liquid interfaces, which disrupts 3D tissue structure and limits interpretation of developmental data. To overcome this limitation, we developed a 3D culture technique using hydrogel embedding to capture morphogenesis in real time. We show that 3D culture better approximates -like niche spacing and dynamic tubule tip rearrangement, as well as -like presentation of branching defects under perturbations to glial cell-derived neurotrophic factor (GDNF)- RE arranged during T ransfection (RET) tyrosine kinase signaling. We find that the concentration of the embedding matrix influences the number of nephrons per ureteric bud (UB) tip and the spacing between tips. To isolate the effect of specific material properties on explant development, we introduce engineered acrylated hyaluronic acid hydrogels that allow independent tuning of stiffness and adhesion. We find that sufficient stiffness and adhesion are both required to maintain kidney shape. Matrix stiffness has a "Goldilocks effect" on the nephron per UB tip balance centered at ∼2 kPa, while higher matrix adhesion increases nephron per UB tip ratio. Our technique captures large-scale, -like tissue morphogenesis in 3D, providing a platform suited to contrasting normal and congenital disease contexts. Moreover, understanding the impact of boundary condition mechanics on kidney development benefits fundamental renal research and advances the engineering of next-generation kidney replacement tissues.