Comparative analysis of human kidney organoid and tubuloid models
Kidney organoids can be generated from commercially available human induced pluripotent stem cells (iPSC). They are amenable for genetic manipulation and useful for modelling development and early-onset genetic diseases. However, iPSC-derived kidney organoids lack longevity to model chronic stressors associated with chronic kidney disease. Adult epithelial kidney organoids (tubuloids) derived from nephrectomies or from renal cells suspended in urine can be passaged, expanded and cryopreserved, offering avenues to model epithelial injury and repair over longer timeframes. However, patient-derived organoids face regulatory barriers in their utilization. To leverage the benefits of both models, we establish a new protocol to generate tubuloids from iPSC-derived kidney organoids (iTubuloids). Kidney organoids were produced from iPSCs by directed differentiation then dissociated and cultured under adult organoid culture conditions. Epithelial organoids formed in less than 3 days from three distinct iPSC lines, each of which have been passaged > 12 times. Comparative analysis of gene expression profiles with RNA sequencing suggested that adult-derived tubuloids better represented the collecting duct, and iTubuloids showed increased expression of proximal and some distal markers. However, expression of proximal tubule markers was higher in iPSC-derived kidney organoids than any tubuloid model. We then evaluated the capacity of iTubuloids to model repetitive kidney injury and found exacerbation of the response and signs of failed repair as the injured progressed. Our study affirms capacity to extend the lifespan of epithelial cell types from short-lived iPSC-derived kidney organoids and reveal a need to optimise nephron cell identities in the tubuloid culture. Overall design: Adult tubuloids were generated from three different nephrectomies and compared to the new iTubuloid model. iTubuloids were derived from three different kidney organoids, which in turn were generated from three induced pluripotent stem cell lines. iTubuloids were subjected to a triple hypoxic injury from day 4 to day 6, after three consecutive passages.