Generation of heterozygous PKD1 mutant pigs exhibiting early-onset renal cyst formation

Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited kidney disease, manifesting as the progressive development of fluid-filled renal cysts. In approximately half of all patients with ADPKD, end-stage renal disease results in decreased renal function. In this study, we used CRISPR-Cas9 and somatic cell cloning to produce pigs with the unique mutation c.152_153insG (PKD1insG/+). Pathological analysis of founder cloned animals and progeny revealed that PKD1insG/+ pigs developed many pathological conditions similar to those of patients with heterozygous mutations in PKD1. Pathological similarities included the formation of macroscopic renal cysts at the neonatal stage, number and cystogenic dynamics of the renal cysts formed, interstitial fibrosis of the renal tissue, and presence of a premature asymptomatic stage. Our findings demonstrate that PKD1insG/+ pigs recapitulate the characteristic symptoms of ADPKD.

The Natural Course of Total Kidney Volume in Patients with Autosomal Dominant Polycystic Kidney Disease undergoing Hemodialysis

Objectives: The natural course of native kidneys after hemodialysis initiation in patients with autosomal dominant polycystic kidney disease (ADPKD) remains poorly understood.Methods: We measured the total volumes of native kidneys in 12 patients who had at least one enhanced computed tomography (CT) image both before and after initiation of hemodialysis (group 1) and in 18 patients who had no image before dialysis but more than two images after dialysis (group 2). In patients with images, the last image was used for analysis only after dialysis.Results: The mean total kidney volume (TKV) (± SD) before hemodialysis initiation was 3132 ± 1413 mL and the mean TKV of the last image was 3047 ± 1323 mL in group 1. The mean TKV change rate (%) was - 5.2 ± 27.4% (P > 0.05) during follow-up of 3.9 ± 1.9 years in group 1. The mean TKV change rate was 2.8 ± 34.4% (P > 0.05) in group 2. The follow-up period after dialysis initiation ranged from 4.2 ± 4.7 to 8.0 ± 5.2 years.Conclusions: The results suggest that the TKV of native polycystic kidneys decreases substantially after hemodialysis initiation. This reduction occurs mainly during the early post-hemodialysis period and followed by a slow enlargement of TKV.

Obacunone Retards Renal Cyst Development in Autosomal Dominant Polycystic Kidney Disease by Activating NRF2

Autosomal dominant polycystic kidney disease (ADPKD) is a common inherited disease characterized by progressive enlargement of fluid-filled cysts derived from renal tubular epithelial cells, which has become the fourth leading cause of end-stage renal diseases. Currently, treatment options for ADPKD remain limited. The purpose of this study was to discover an effective therapeutic drug for ADPKD. With virtual screening, Madin-Darby canine kidney (MDCK) cyst model, embryonic kidney cyst model and kidney-specific Pkd1 knockout mouse (PKD) model, we identified obacunone as a candidate compound for ADPKD drug discovery from a natural antioxidant compound library. In vitro experiments showed that obacunone significantly inhibited cyst formation and expansion of MDCK cysts and embryonic kidney cysts in a dose-dependent manner. In vivo, obacunone treatment significantly reduced the renal cyst development in PKD mice. Western blot and morphological analysis revealed that obacunone served as a NRF2 activator in ADPKD, which suppressed lipid peroxidation by up-regulating GPX4 and finally restrained excessive cell proliferation by down-regulating mTOR and MAPK signaling pathways. Experimental data demonstrated obacunone as an effective renal cyst inhibitor for ADPKD, indicating that obacunone might be developed into a therapeutic drug for ADPKD treatment.

TACAN is a novel regulator of PKD2

Autosomal dominant polycystic kidney disease (ADPKD) is caused by mutations in membrane receptor PKD1 or cation channel PKD2. TACAN (also named TMEM120A), recently reported as an ion channel in neuron cells for mechano and pain sensing, is also distributed in diverse non-neuronal tissues such as kidney, heart and intestine, suggesting its involvement in other functions. In this study, we found that TACAN is in complex with PKD2 in native renal cell lines. Using the two-electrode voltage clamp in Xenopus oocytes we found that TACAN inhibited the channel activity of PKD2 gain-of-function mutant F604P. The first and last transmembrane domains of TACAN were found to interact with the PKD2 C- and N-terminal portions, respectively. We showed that the TACAN N-terminus acted as a blocking peptide and that TACAN inhibits the PKD2 function through the PKD2/TACAN binding. By patch clamping in mammalian cells, we found that TACAN inhibits both the single channel conductance and open probability of PKD2 and mutant F604P. Further, PKD2 co-expressed with TACAN, but not PKD2 alone, exhibited pressure sensitivity. In summary, this study revealed that TACAN acts as a PKD2 inhibitor and mediates mechano sensitivity of the PKD2/TACAN channel complex.

The C-terminal tail of polycystin-1 suppresses cystic disease in a mitochondrial enzyme-dependent fashion

Autosomal dominant polycystic kidney disease (ADPKD) is the most prevalent potentially lethal monogenic disorder. Approximately 78% of cases are caused by mutations in the PKD1 gene, which encodes polycystin-1 (PC1). PC1 is a large 462-kDa protein that undergoes cleavage in its N and C-terminal domains. C-terminal cleavage produces fragments that translocate to mitochondria. We show that transgenic expression of a protein corresponding to the final 200 amino acid residues of PC1 in a Pkd1-KO orthologous murine model of ADPKD dramatically suppresses cystic phenotype and preserves renal function. This suppression depends upon an interaction between the C-terminal tail of PC1 and the mitochondrial enzyme Nicotinamide Nucleotide Transhydrogenase. This interaction modulates tubular/cyst cell proliferation, the metabolic profile, mitochondrial function and the redox state. Together, these results suggest that a short fragment of PC1 is sufficient to suppress cystic phenotype and open the door to the exploration of gene therapy strategies for ADPKD.