Four‐jointed knock‐out delays renal failure in an ADPKD model with kidney injury

Abstract

Autosomal Dominant Polycystic Kidney Disease is characterised by the development of fluid‐filled cysts in the kidneys which lead to end‐stage renal disease (ESRD). In the majority of cases, the disease is caused by a mutation in the Pkd1 gene. In a previous study, we demonstrated that renal injury can accelerate cyst formation in Pkd1 knock‐out (KO) mice. In that study, we found that after injury four‐jointed (Fjx1), an upstream regulator of planar cell polarity and the Hippo pathway, was aberrantly expressed in Pkd1 KO mice compared to WT. Therefore, we hypothesised a role for Fjx1 in injury/repair and cyst formation. We generated single and double deletion mice for Pkd1 and Fjx1, and we induced toxic renal injury using the nephrotoxic compound 1,2‐dichlorovinyl‐cysteine. We confirmed that nephrotoxic injury can accelerate cyst formation in Pkd1 mutant mice. This caused Pkd1 KO mice to reach ESRD significantly faster; unexpectedly, double KO mice survived significantly longer. Cyst formation was comparable in both models, but we found significantly less fibrosis and macrophage infiltration in double KO mice. Taken together, these data suggest that Fjx1 disruption protects the cystic kidneys against kidney failure by reducing inflammation and fibrosis. Moreover, we describe, for the first time, an interesting (yet unidentified) mechanism that partially discriminates cyst growth from fibrogenesis. © 2019 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Characterisation of transcription factor profiles in polycystic kidney disease (PKD): identification and validation of STAT3 and RUNX1 in the injury/repair response and PKD progression

“…Our next step was to validate TFs identified in the meta-analysis in independent experimental groups of mice during PKD progression and/or the nephrotoxic injury/repair response [15]. Briefly, we induced Pkd1 deletion in adult mice via tamoxifen administration, which leads to a slow progression of the disease.…”

“…Mice were sacrificed at 1, 2, 5 and 10 weeks after DCVC and kidney failure. The experimental pipeline has been presented in Formica et al [15]. The Wt + PBS, Wt + DCVC and Pkd1 KO + PBS groups have also been used in Malas et al [5].…”

“…Renal tissue from ADPKD patients at end-stage renal failure was fixed in formalin as previously described [15]. Control tissues were obtained from donor kidneys non-suitable for transplant.…”

Reducing YAP expression in Pkd1 mutant mice does not improve the cystic phenotype

“…Total RNA was isolated from snap‐frozen kidneys using TRI Reagent (#T9424; Sigma‐Aldrich) according to manufacturer's protocol, and gene expression analysis was performed by quantitative PCR (qPCR) as described previously 8 . Briefly, cDNA synthesis was done using Transcriptor First Strand cDNA Synthesis Kit (#04897030001; Roche) according to the manufacturer's protocol.…”

The Biological Significance and Implications of Planar Cell Polarity for Nephrology

“…Though Fat4 −/− and Dchs1 −/− embryos possess characteristics that could suggest defective planar-polarised behaviours, such as misorientation of stereocilia in the cochlea, widening of the neural tube and disruption of orientated cell division in renal tubular epithelium (Saburi et al, 2008;Mao et al, 2011), the asymmetric expression of these proteins in tubular epithelial cells has not been assessed. Moreover, deletion of Fjx1; the mammalian homologue of Fj, did not worsen the cystic phenotype in mice with postnatal deletion of Pkd1 in collecting ducts (Formica et al, 2019). Compound loss of Fat4 with Vangl2 in mice, however, does enhance the cystic phenotype compared to Fat4 loss alone (Saburi et al, 2008), and raises the question as to whether FAT4 interacts with core PCP proteins to modulate cyst expansion in PKD.…”