Reversal of elevated Gli3 in Autosomal Recessive Polycystic Kidney Disease does not alter cystogenesis

Polycystic kidney diseases (PKD) are genetic disorders characterised by the formation of fluid-filled cysts, which disrupt kidney architecture and function. Autosomal recessive PKD (ARPKD) is a rare form of PKD, caused by mutations in PKHD1, and clinically more severe than the more common autosomal dominant PKD (ADPKD). Prior studies have implicated the ciliary-located Hedgehog (Hh) pathway in ADPKD, with increased levels of Hh components in experimental ADPKD models, and reduced cystogenesis following pharmacological Hh inhibition. In contrast, the role of the Hh pathway in ARPKD is poorly understood. We hypothesised that Hh pathway activity would be elevated during ARPKD pathogenesis, and its modulation may inhibit cystogenesis, akin to prior findings in ADPKD. To test this, we utilised Cpk mice, a model which replicates the pathophysiology of ARPKD, and generated a human cellular ARPKD 3-dimensional cystogenesis model by mutating PKHD1 in human collecting duct cells through CRISPR-Cas9 technology. We found significantly elevated levels of the Hh transcriptional effector Gli3 in the Cpk mouse, a finding replicated in our human cellular ARPKD model. In the Cpk mouse, we also observed an increase in total GLI3 and GLI3 repressor protein levels. However, reduction of increased Gli3 levels via genetic deletion in the Cpk mouse did not affect cyst formation. Similarly, lowering GLI3 transcript to wildtype levels, did not influence cyst size in our human cellular ARPKD model. Collectively, these data show that elevated Gli3 does not modulate cyst progression in the context of ARPKD, highlighting the complexity of the Hh pathway in PKD.