Kidney organoids made from pluripotent stem cells have the potential to revolutionize how kidney development, disease, and injury are studied. Current protocols are technically complex, suffer from poor reproducibility, and have high reagent costs that restrict scalability. To overcome some of these issues, we have established a simple, inexpensive, and robust method to grow kidney organoids in bulk from human induced pluripotent stem cells. Our organoids develop tubular structures by day 8 and show optimal tissue morphology at day 14. A comparison with fetal human kidneys suggests that day-14 organoid tissue most closely resembles late capillary loop stage nephrons. We show that deletion of HNF1B, a transcription factor linked to congenital kidney defects, interferes with tubulogenesis, validating our experimental system for studying renal developmental biology. Taken together, our protocol provides a fast, efficient, and cost-effective method for generating large quantities of human fetal kidney tissue, enabling the study of normal and aberrant kidney development.

Acute kidney injury (AKI) remains a major global healthcare problem and there is a need to develop human-based models to study AKI in vitro. Towards this goal, we have characterized induced pluripotent stem cell-derived human kidney organoids and their response to cisplatin, a chemotherapeutic drug that induces AKI and preferentially damages the proximal tubule. We found that a single treatment with 50 µM cisplatin induces HAVCR1 and CXCL8 expression, DNA damage (γH2AX) and cell death in the organoids but greatly impairs organoid viability. DNA damage was not specific to the proximal tubule but also affected the distal tubule and interstitial cell populations. This lack of specificity correlated with low expression of the proximal tubule-specific SLC22A2/OCT2 transporter for cisplatin. To improve viability, we developed a repeated low-dose regimen of 4x 5 µM cisplatin over 7 days and found this causing less toxicity while still inducing a robust injury response that included secretion of known AKI biomarkers and inflammatory cytokines. This work validates the use of human kidney organoids to model aspects of cisplatin-induced injury, with the potential to identify new AKI biomarkers and develop better therapies.

We present a loss‐of‐function study using antisense morpholino (MO) reagents for the organizer‐specific gene Goosecoid ( Gsc ) and the ventral genes Vent1 and Vent2 . Unlike in the mouse Gsc is required in Xenopus for mesodermal patterning during gastrulation, causing phenotypes ranging from reduction of head structures—including cyclopia and holoprosencephaly—to expansion of ventral tissues in MO‐injected embryos. The overexpression effects of Gsc mRNA require the expression of the BMP antagonist Chordin , a downstream target of Gsc. Combined Vent1 and Vent2 MOs strongly dorsalized the embryo. Unexpectedly, simultaneous depletion of all three genes led to a rescue of almost normal development in a variety of embryological assays. Thus, the phenotypic effects of depleting Gsc or Vent1/2 are caused by the transcriptional upregulation of their opposing counterparts. A principal function of Gsc and Vent1/2 homeobox genes might be to mediate a self‐adjusting mechanism that restores the basic body plan when deviations from the norm occur, rather than generating individual cell types. The results may shed light on the molecular mechanisms of genetic redundancy.

D-amino acids are present in some peptides from amphibian skin. These residues are derived from the correspondingl-amino acids present in the respective precursors. From skin secretions ofBombinae, we have isolated an enzyme that catalyzes the isomerization of anl-Ile in position 2 of a model peptide tod-allo-Ile. In the course of this reaction, which proceeds without the addition of a cofactor, radioactivity from tritiated water is incorporated into the second position of the product. The amino acid sequence of this isomerase could be deduced from cloned cDNA and genomic DNA. After expression of this cDNA in oocytes ofXenopus laevis, isomerase activity could be detected. Polypeptides related to the frog skin enzyme are present in several vertebrate species, including humans.