Inhibition of Hedgehog signaling does not mitigate polycystic kidney disease severity in a <i>Pkd1</i> mutant mouse model

Autosomal dominant polycystic kidney disease (ADPKD) is a monogenic disorder caused by mutations in PKD1 or PKD2, encoding polycystin-1 and polycystin-2, respectively. These polycystins form a cilia-localized complex that, when mutated, fails to inhibit an uncharacterized cilia-dependent cyst activation (CDCA) signal. This leads to progressive bilateral cyst growth and ultimately compromised renal function. Previous in vitro and in vivo studies from our group have demonstrated that Hedgehog (Hh) signaling inhibition reduces renal cystic severity in PKD models. To further investigate, we inactivated several Hh pathway components (Gli1, Gli2, Gli3 and Smo) in a Pkd1 hypomorphic mouse model through conditional deletion by tamoxifen-induced Cre-Lox recombination. We assessed cystic severity using kidney weight assessment and a microcomputed tomography (micro-CT)-based 3D imaging assay. Contrary to expectations, inactivation of Gli1 and Smo significantly increased cystogenesis. These findings suggest that Hh signaling does not mediate the CDCA signal.