FGF9 treatment reduces off-target chondrocytes from iPSC-derived kidney organoids.

Renal failure due to drug nephrotoxicity or disease is frequently observed in patients. The development of in vitro models able to recapitulate kidney biology offers new possibilities to study drug toxicity or model diseases. Induced pluripotent stem cell-derived kidney organoids already show promise, but several drawbacks must be overcome to maintain them in culture, among which is the presence of non-renal cell populations such as cartilage. We modified the culture protocol and maintained kidney organoids in medium containing FGF9 for 1 additional week compared to the control protocol (Takasato). In comparison to the control, the FGF9-treated kidney organoids had reduced cartilage at day 7 + 25 and diminished chondrocyte marker expression. Importantly, the renal structures assessed by immunofluorescence were unaffected by the FGF9 treatment. This reduction of cartilage produces a higher quality kidney organoid that can be maintained longer in culture to improve their maturation for further in vivo work.