Amniotic fluid-derived kidney organoids recapitulate human fetal nephrogenesis and show functionality in vitro

Kidney anomalies are a common problem, which usually lacks treatment due to the difficulty in directly studying the cells of the developing human kidney. Amniotic fluid (AF) consists mainly of fetal urine, likely containing fetal renal progenitors, representing an accessible cell source for studying kidney development in real time. We hypothesize that renal fetal progenitors can be utilized to create kidney organoids, which could be employed to study and model human nephrogenesis in a personalized manner. As a first step, we identified nephron progenitors expressing PAX2 and SIX2 in AF. We next established organoid cultures from AF derived cells using a defined kidney media. The morphology of AF kidney organoids is similar to other types of kidney organoids, presenting as either cystic or convoluted. Immunostaining of the organoids demonstrates presence of renal progenitors, kidney epithelia of the proximal, loop of Henle and distal tubular lineages, and ureteric bud markers, indicating recapitulation of nephrogenic processes. Single cell RNA sequencing supports kidney identity of organoids. Gene expression of kidney clusters confirms the presence of fetal developmental stages: nephron progenitor cells, renal vesicle /pre-tubular aggregate, ureteric bud cells, as well as tubular cells. The organoids can be further directed towards maturation by inhibition of Wnt signaling, and by removal of supporting extracellular matrix. To conclude, AF-derived kidney organoids can be established with high efficiency, representing a unique model of human fetal development, which could be used to uncover new aspects of nephrogenesis, decipher pathogenic mechanisms of developmental anomalies and screen new drugs.