Growth and differentiation of human induced pluripotent stem cell(hiPSC)-derived kidney organoids using fully synthetic peptide hydrogels

Human induced pluripotent stem cell(hiPSC)-derived kidney organoids have prospective applications ranging from basic disease modelling to personalised medicine.However,there remains a necessity to refine the bio-physical and biochemical parameters that govern kidney organoid formation.Differentiation within fully-controllable and physiologically relevant 3D growth environments will be critical to improving organoid reproducibility and maturation.Here,we matured hiPSC-derived kidney organoids within fully synthetic self-assembling peptide hydrogels(SAPHs)of variable stiffness(storage modulus,G′).The resulting organoids con-tained complex structures comparable to those differentiated within the animal-derived matrix,Matrigel.Single-cell RNA sequencing(scRNA-seq)was then used to compare organoids matured within SAPHs to those grown within Matrigel or at the air-liquid interface.A total of 13,179 cells were analysed,revealing 14 distinct clusters.Organoid compositional analysis revealed a larger proportion of nephron cell types within Transwell-derived organoids,while SAPH-derived organoids were enriched for stromal-associated cell populations.Notably,dif-ferentiation within a higher G’SAPH generated podocytes with more mature gene expression profiles.Addi-tionally,maturation within a 3D microenvironment significantly reduced the derivation of off-target cell types,which are a known limitation of current kidney organoid protocols.This work demonstrates the utility of syn-thetic peptide-based hydrogels with a defined stiffness,as a minimally complex microenvironment for the selected differentiation of kidney organoids.