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Scientific Projects
 
Identification of modifier gene(s) for autosomal dominant polycystic disease (ADPKD) in the PKD/ Mhm(cy/+) rat, Dr. Marie-Therese Bihoreau

This project builds on results from the mapping of modifier loci for ADPKD carried out in hybrids derived from PKD/Mhm (cy/+) and non-affected Brown Norway rats. The objectives of the project are to identify modifier genes of spontanous ADPKD in the PKD/Mhm (cy/+) rat model and to determine how they influence the severity of the phenotype. Chromosomal mapping of modifier genes for ADPKD will be undertaken in a PKD/Mhm (cy/+) x Lewis cross. Both comparative genome analysis of the modifier loci between rat and human, and sequence analysis of differentially expressed cDNAs will be applied to the isolation of candidate genes for ADPKD in rat and their functional validation. Strong candidates will be searched for sequence variations between PKD/Mhm (cy/+) and non-affected inbred rat strains. Results from our study will help therapeutic strategies by providing new candidate genes for ADPKD and defining new biochemical pathways involved in the disease amenable to drug development.
 

Conditional PKD2 knockout mouse, PD Dr. Bernd Dworniczak

The aim of our project is the establishment of a murine conditional ADPKD2 model. Homozygous mutant animals (Pkd1 and Pkd2) die perinatally, and heterozygous mice do not show an adequate phenotype; therefore therapeutic strategies to halt cyst formation cannot be tested efficiently. Generation of a mouse model where cyst formation can be induced in adult mice will be achieved by conditional targeting of the Pkd2 gene by use of the Cre-loxP recombination system. Cyst formation will be induced by breeding these mice to transgenic mice in which Cre-recombinase is expressed in different parts of the nephron. Disease progression and improvement of kidney performance - after therapeutic gene transfer - will be monitored by analysis of physiological parameters and by magnetic resonance imaging. We expect to create a Pkd2 mouse model where the induced loss of Pkd2 gene function leads to cyst formation in a spatially and temporally controlled manner. This animal model will be a valuable tool to test therapeutic genes and strategies to reduce, modulate or prevent cyst formation. By use of techniques where we can measure cyst formation and kidney performance in the living animal, we will be able to perform follow up studies.
 

Role of Mmp9 in polycystic kidney disease (PKD), Dr. Brigitte Lelongt

The objective ist to determine in vivo whether Mmp9, a member of the matrix metalloproteinase family of enzymes, can be used as a gene therapy in PKD. This enzyme degrades extracellular matrix components and is probably involved in tubular cyst formation and fibrosis observed in PKD. In a first step, we will breed Mmp9 (-/-) mice available in our laboratory to pcy mice that develop a progressive form of PKD, to analyze the impact of Mmp9 deficiency on pcy mouse renal phenotype. Since Pkd2 (-/-) mice are lethal, conditional Pkd2 (-/-) deficient mice that are currently in preparation, will be used in a second step to establish Mmp9 (-/-)/conditional Pkd2 double-mutants, and their renal phenotype will be compared to Mmp9 (+/+)/ conditional Pkd2 (-/-) control mice. We hypothesize that Mmp9 can be deleterious in early stage of cyst formation and protective at later stages, when fibrosis develops.
 

Efficacy and safety of gene transfer in the polycystic kidney, Dr. Lucia Monaco/  Prof. Dr. Norbert Gretz

In the first part of our project we aim to establish an efficient and safe gene transfer protocol for an animal model of ADPKD. To this aim, reporter genes will be employed, to address 3 questions: 1) How can we improve gene transfer to the rat kidney? 2) Can we efficiently and safely express exogenous DNA in the (cy/+) kidney? 3) Can we efficiently and safe express exogenous DNA in the kidney of conditional Pkd2 knockout mice? In the second part of the project, the optimized methods for gene transfer to the kidney will be applied to the use of the therapeutic genes identified within the project "Identification of modifier gene(s) for autosomal dominant polycystic disease (ADPKD) in the PKD/ Mhm(cy/+) rat" in the polycystic kidney models ((cy/+)rat, pcy mouse, conditional Pkd2 knockout mouse). The work we propose will advance the technology of gene transfer to the kidney; expected results include improved efficiency and control of safety issues. This is a relevant aspect, in view of clinical applications. In addition, gene transfer experiments with therapeutic genes for ADPKD in animal models of the disease should provide the proof-of-principle of the feasibility of gene therapy for PKD. Finally, the outcome of this work will be useful in addressing other renal diseases by gene therapy.
 

TIMP-2 as a novel therapeutic tool against polycystic disease, Prof. Dr. Ralph Witzgall

The expansion of cysts bears several similarities to the expansion of benign tumors into the surrounding tissue. Previous evidence argues for an important contribution of metalloproteinases to cyst formation in several rodent models of polycystic kidney disease (PKD). This observation represents the rationale for the strategy to use TIMP-2, a crucial member of the tissue-inhibitors of metalloproteinases, to prevent or slow down cystic expansion in the pcy mouse model of PKD. Using an inducible expression system in transgenic mice, the efficacy of TIMP-2 as a therapeutical tool against PKD will be investigated. A number of pharmaceutical companies are already conducting clinical trials in order to establish the usefulness of synthetic matrix metalloproteinases inhibitors against cancer and rheumatoid arthritis. Compared to those conventional synthetic drugs, the local delivery of TIMP-2 by gene therapy should have a distinct advantage due to less systemic side effects.
 

 

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