Abstract
Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited kidney disorder and a leading cause of end-stage kidney disease. It is characterised by progressive cyst formation, leading to renal dysfunction and, often kidney failure. Despite its prevalence, treatment options remain limited. Tolvaptan, the only FDA-approved therapy, provides partial benefits but has significant side effects, indicating the urgent need for alternative therapeutic strategies.
Paired box 2 (PAX2) is downregulated in mature kidney but reactivated in ADPKD, making it a promising therapeutic target with potential kidney-specificity. The study has demonstrated that a small-molecule inhibitor, EG1, previously identified by its ability to interact with the PAX2 DNA binding domain, significantly reduced spheroid growth in 3D cell culture models using MDCK, human ADPKD-derived WT9-7 and WT9-12 cells. Similarly, PAX2 silencing via siRNAs reduced spheroid size, supporting PAX2 inhibition as a potential treatment strategy. Anti-miR-17-5p has shown significant efficacy in attenuating disease progression in ADPKD but may have off-target effects. A dual-silencing construct was developed, targeting both PAX2 and miR-17-5p, to allow lower dose inhibition of two pathways. This construct also suppressed cyst growth, suggesting a potential combinatorial therapeutic approach.
Since EG1 inhibits the DNA-binding activity of both the renal PAX proteins, PAX2 and PAX8, inhibition of PAX8 alone using siRNA was then examined in 3D culture models and also displayed a reduction in spheroid growth. PAX8 cellular localization in ADPKD kidney tissues was unexpectedly altered, with cytoplasmic staining in cyst-lining epithelial cells, suggesting a novel effect on the subcellular localization of PAX8 in cyst-lining epithelial cells. RNA sequencing of human ADPKD cell lines identified distinct and overlapping transcriptional networks regulated by PAX2 and PAX8, implicating pathways involved in cell cycle progression, apoptosis, and extracellular matrix (ECM) remodeling in cyst-derived cells. Several downstream genes regulated by PAX2 and PAX8 such as FGF18, WWTR1, GPRC5A, and HDAC4, might be novel therapeutic targets for ADPKD.
This study provides new insights into the roles of PAX2 and PAX8 in ADPKD and supports PAX2-targeting therapies as a potential treatment strategy. Future research should focus on experimental validation of RNA-seq identified genes and signaling pathways, and assessment of these therapeutic candidates in more advanced disease models to facilitate clinical translation.