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

The Hippo pathway is a highly conserved signalling route involved in organ size regulation. The final effectors of this pathway are two transcriptional coactivators, yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (WWTR1 or TAZ). Previously, we showed aberrant activation of the Hippo pathway in autosomal-dominant polycystic kidney disease (ADPKD), suggesting that YAP/TAZ might play a role in disease progression. Using antisense oligonucleotides (ASOs) in a mouse model for ADPKD, we efficiently down-regulated Yap levels in the kidneys. However, we did not see any effect on cyst formation or growth. Moreover, the expression of YAP/TAZ downstream targets was not changed, while WNT and TGF-ß pathways' downstream targets Myc, Acta2 and Vim were more expressed after Yap knockdown. Overall, our data indicate that reducing YAP levels is not a viable strategy to modulate PKD progression.

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

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.

Meta-analysis of polycystic kidney disease expression profiles defines strong involvement of injury repair processes.

Polycystic kidney disease (PKD) is a major cause of end-stage renal disease. The disease mechanisms are not well understood and the pathogenesis toward renal failure remains elusive. In this study, we present the first RNASeq analysis of a Pkd1-mutant mouse model in a combined meta-analysis with other published PKD expression profiles. We introduce the PKD Signature, a set of 1,515 genes that are commonly dysregulated in PKD studies. We show that the signature genes include many known and novel PKD-related genes and functions. Moreover, genes with a role in injury repair, as evidenced by expression data and/or automated literature analysis, were significantly enriched in the PKD Signature, with 35% of the PKD Signature genes being directly implicated in injury repair. NF-κB signaling, epithelial-mesenchymal transition, inflammatory response, hypoxia, and metabolism were among the most prominent injury or repair-related biological processes with a role in the PKD etiology. Novel PKD genes with a role in PKD and in injury were confirmed in another Pkd1-mutant mouse model as well as in animals treated with a nephrotoxic agent. We propose that compounds that can modulate the injury-repair response could be valuable drug candidates for PKD treatment.

Molecular pathways involved in injury-repair and ADPKD progression.

The major hallmark of Autosomal Dominant Polycystic Kidney Disease (ADPKD) is the formation of many fluid-filled cysts in the kidneys, which ultimately impairs the normal renal structure and function, leading to end-stage renal disease (ESRD). A large body of evidence suggests that injury-repair mechanisms are part of ADPKD progression. Once cysts have been formed, proliferation and fluid secretion contribute to the cyst size increase, which eventually causes stress on the surrounding tissue resulting in local injury and fibrosis. In addition, renal injury can cause or accelerate cyst formation. In this review, we will describe the various mechanisms activated during renal injury and tissue repair and show how they largely overlap with the molecular mechanisms activated during PKD progression. In particular, we will discuss molecular mechanisms such as proliferation, inflammation, cell differentiation, cytokines and growth factors secretion, which are activated following the renal injury to allow the remodelling of the tissue and a proper organ repair. We will also underline how, in a context of PKD-related gene mutations, aberrant or chronic activation of these developmental pathways and repair/remodelling mechanisms results in exacerbation of the disease.

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.

Autosomal dominant polycystic kidney disease (ADPKD) is the most common genetic renal disease, caused in the majority of the cases by a mutation in either the PKD1 or the PKD2 gene. ADPKD is characterised by a progressive increase in the number and size of cysts, together with fibrosis and distortion of the renal architecture, over the years. This is accompanied by alterations in a complex network of signalling pathways. However, the underlying molecular mechanisms are not well characterised. Previously, we defined the PKD Signature, a set of genes typically dysregulated in PKD across different disease models from a meta-analysis of expression profiles. Given the importance of transcription factors (TFs) in modulating disease, we focused in this paper on characterising TFs from the PKD Signature. Our results revealed that out of the 1515 genes in the PKD Signature, 92 were TFs with altered expression in PKD, and 32 of those were also implicated in tissue injury/repair mechanisms. Validating the dysregulation of these TFs by qPCR in independent PKD and injury models largely confirmed these findings. STAT3 and RUNX1 displayed the strongest activation in cystic kidneys, as demonstrated by chromatin immunoprecipitation (ChIP) followed by qPCR. Using immunohistochemistry, we showed a dramatic increase of expression after renal injury in mice and cystic renal tissue of mice and humans. Our results suggest a role for STAT3 and RUNX1 and their downstream targets in the aetiology of ADPKD and indicate that the meta-analysis approach is a viable strategy for new target discovery in PKD. KEY MESSAGES: We identified a list of transcription factors (TFs) commonly dysregulated in ADPKD. Out of the 92 TFs identified in the PKD Signature, 35% are also involved in injury/repair processes. STAT3 and RUNX1 are the most significantly dysregulated TFs after injury and during PKD progression. STAT3 and RUNX1 activity is increased in cystic compared to non-cystic mouse kidneys. Increased expression of STAT3 and RUNX1 is observed in the nuclei of renal epithelial cells, also in human ADPKD samples.

Comparative transcriptomics of shear stress treated Pkd1-/- cells and pre-cystic kidneys reveals pathways involved in early polycystic kidney disease.

Mutations in the PKD1 or PKD2 genes are the cause of autosomal dominant polycystic kidney disease (ADPKD). The encoded proteins localize within the cell membrane and primary cilia and are proposed to be involved in mechanotransduction. Therefore, we evaluate shear stress dependent signaling in renal epithelial cells and the relevance for ADPKD. Using RNA sequencing and pathway analysis, we compared gene expression of in vitro shear stress treated Pkd1-/- renal epithelial cells and in vivo pre-cystic Pkd1del models. We show that shear stress alters the same signaling pathways in Pkd1-/- renal epithelial cells and Pkd1wt controls. However, expression of a number of genes was slightly more induced by shear stress in Pkd1-/- cells, suggesting that Pkd1 has the function to restrain shear regulated signaling instead of being a mechano-sensing activator. We also compared altered gene expression in Pkd1-/- cells during shear with in vivo transcriptome data of kidneys from Pkd1del mice at three early pre-cystic time-points. This revealed overlap of a limited number of differentially expressed genes. However, the overlap between cells and mice is much higher when looking at pathways and molecular processes, largely due to altered expression of paralogous genes. Several of the altered pathways in the in vitro and in vivo Pkd1del models are known to be implicated in ADPKD pathways, including PI3K-AKT, MAPK, Hippo, calcium, Wnt, and TGF-ß signaling. We hypothesize that increased activation of selected genes in renal epithelial cells early upon Pkd1 gene disruption may disturb the balance in signaling and may contribute to cyst formation.

Allogeneic stem cell transplantation in therapy-related acute myeloid leukemia and myelodysplastic syndromes: impact of patient characteristics and timing of transplant.

Patients with therapy-related acute myeloid leukemia (t-AML) and myelodysplastic syndromes (t-MDS) have poor survival and high non-relapse mortality (NRM) after allogeneic stem cell transplantation. This retrospective study assessed the transplant outcomes of 29 consecutive patients with t-AML (83%) or t-MDS (17%) treated with allogeneic transplantation. The median age of patients was 51 years. Donors were mostly matched unrelated (52%), and 59% of patients received myeloablative conditioning. Two-year overall survival, event-free survival and relapse incidence were 37%, 34% and 33%; NRM was 17% at 100 days, and 32% at 2 years. Event-free survival was reduced in patients with high-risk cytogenetics (p = 0.02), Karnofsky performance status ≤ 80% (p = 0.001) and disease after induction ± consolidation (p = 0.006). NRM was higher in patients receiving > 2 therapy lines for previous cancer (p = 0.01) and in those allografted > 6 months from diagnosis (p = 0.03). In conclusion, allogeneic transplantation should be proposed timely to these patients after an accurate analysis of patient history.