In Vivo Base Editing Rescues ADPKD in Mice

Background: ADPKD is the most prevalent genetic kidney disease, caused by mutations of the PKD1 and PKD2 genes, which drive renal cyst growth and extrarenal complications, including cardiac hypertrophy. Adeno-associated virus (AAV) delivered CRISPR-Cas9 base editing is a revolutionary approach for treating inherited diseases. However, thus far, the effect of AAV-BEs on DNA editing in ADPKD have not been reported. Methods: To determine whether correction of the Pkd1 gene mutation in Pkd1RC/RC mice, carrying an arginine (R) to cystine (C) mutation as in ADPKD patients, delays cyst growth and decreases heart hypertrophy, we treated Pkd1RC/RC mice with one dose of two newly developed ABE9-AAV9 base editors through intravenous (IV) injection. To evaluate the effect of the ABE9-AVV9 base editing on lifespan, we treated Pkd1RC/null mice with both base editor systems. Results: We developed 1) a broadly expressed AAV9-ABE9 base editor system to correct Pkd1 gene mutation in whole body, and 2) a kidney specific AAV9-ABE9 base editor system to increase the efficiency and specificity of ABE9 base editor on correction of Pkd1 gene mutation in kidney only. We showed that one dose of broadly expressed AAV9-ABE9 base editor can effectively delay renal cyst growth and decrease cardiac hypertrophy in Pkd1RC/RC mice, and that one dose of kidney-specific AVV9-ABE9 base editor is selectively expressed in kidneys, but not in hearts, resulting in efficiently delaying cyst growth in Pkd1RC/RC kidneys. The precise editing efficiency with one dose of these two AAV9-ABE9 base editor systems remained stable in kidneys six months after treatment, increasing the expression of Pkd1 mRNA and a decrease of cyst index, KW/BW ratios, BUN levels in Pkd1RC/RC mice. Treatment with AAV9-ABE9 base editors also decreased cystic cell proliferation and the accumulation of macrophages at interstitial and pericystic regions, and increased cyst lining epithelial cell apoptosis in Pkd1RC/RC kidneys. Treatment with one dose of either the broadly expressed or kidney specific ABE9 base editor increased the survival rate of Pkd1RC/null mice. Conclusion: This is the first proof-of-principle study that use CRISPR/Cas9 base editing to correct a pathogenic single-nucleotide variant in an ADPKD mouse model, which demonstrates considerable potential for single-dose genetic therapies to correct pathogenic variants and prevent the development of ADPKD in the clinic. Funding: NIDDK Support - NIDDK Support, NIDDK Support, Other U.S. Government Support