Selective mTORC1 Inhibitors Block Cystogenesis in a Human Kidney Organoid Model of Polycystic Kidney Disease
- Genetic Diseases of the Kidneys: Cystic - II
November 04, 2022 | Location: Exhibit Hall, Orange County Convention Center‚ West Building
Abstract Time: 10:00 AM - 12:00 PM
Category: Genetic Diseases of the Kidneys
- 1101 Genetic Diseases of the Kidneys: Cystic
- Gulieva, Ramila E., University of Washington, Seattle, Washington, United States
- Freedman, Benjamin S., University of Washington, Seattle, Washington, United States
The mammalian target of rapamycin complex (mTORC) pathway is activated in kidneys with PKD, and is therefore a promising target for therapy development. There are two mTORC complexes, mTORC1 and mTORC2. Recent work has developed selective mTORC1 inhibitors (mTORC1i), which have fewer side effects than compounds that inhibit both mTORC1 and mTORC2. Whether such compounds can affect PKD cystogenesis, however, has not yet been determined. We set out to test this in human kidney organoids with mutations in PKD1 or PKD2, which form cysts in a PKD-specific way.
PKD1-/- or PKD2-/- iPSCs were differentiated into kidney organoids, placed in suspension for 9 days until cysts formed, and transferred into 96-well plates (one cyst/well). Compounds were introduced at different concentrations (0.1 to 30 µM), including two selective mTORC1i (ORG1, ORG2), everolimus, vehicle and untreated controls. Phase contrast images were taken of each organoid on multiple days for 14 days to measure changes in cyst size. In parallel, cultures of organoids were used to assess markers of mTOR activity (P-p70S6, P-S6RP, P-AKT). LDH activity and live/dead staining were used to measure toxicity.
All mTORC1 inhibitors produced dose-dependent reductions in cyst growth over the course of the experiment. Everolimus and ORG1 had statistically significant effects, whereas ORG2 was less efficacious. All mTORC inhibitors significantly decreased phosphorylation of mTOR targets S6RP and p70s6. P-AKT was decreased only in everolimus treatments but not in ORG1 and ORG2 treated organoids, reflecting selectivity of mTORC1i. Live/dead assay measured on day 14 indicated that everolimus is toxic at 10 µM and 30 µM, ORG1 at 30 µM, and for ORG2 no sign of toxicity was identified.
We have established a model of drug treatment in PKD organoids to predict therapeutics that can slow cyst growth. Findings in organoids demonstrated efficacy of mTORC inhibitors for PKD, which was consistent with the ability of this class of drugs to slow cyst growth in pre-clinical models. This helps to validate the use of organoids for studying PKD and screening potential therapeutics. An exciting finding is that novel selective mTORC1i compounds show efficacy and target engagement at non-toxic doses. These data provide proof of concept for further studies in animals and eventually humans.
- NIDDK Support –