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Kidney Week

Abstract: TH-PO818

Investigating the Pathophysiology and a Potential Therapeutic Approach for Cystinosis

Session Information

Category: Genetic Diseases of the Kidneys

  • 1002 Genetic Diseases of the Kidneys: Non-Cystic

Authors

  • Jamalpoor, Amer A., Utrecht Institute of Pharmaceutical Sciences, Utrecht, Netherlands
  • Zaal, Esther A., University of Utrecht, Utrecht, Netherlands
  • Berkers, Celia, Utrecht University, Utrecht, Netherlands
  • Levtchenko, Elena N., University Hospitals Leuven, Herent, Belgium
  • Masereeuw, Rosalinde, Utrecht Institute for Pharmaceutical Sciences, Utrecht,, UTRECHT, Netherlands
  • Janssen, Manoe J., Utrecht University, Utrecht, Netherlands
Background

Nephropathic cystinosis is a severe genetic disorder caused by mutations in CTNS gene (cystine transporter), leading to the lysosomal accumulation of cystine and progressive organ damage. To date, no appropriate in vitro isogenic cystinotic cell models exist, a pre-requisite to study the link between the CTNS gene and the disease, and to investigate potential therapeutic strategies. Hence, our aim was to generate a cystinosis phenotype in human kidney cells using CRISPR/Cas9 and study cystinosis pathology.

Methods

We selectively knocked-out the CTNS gene in conditionally immortalized proximal tubular epithelial cells (ciPTEC). An untargeted metabolomics approach based on UHPLC-MS/MS was applied for the intra- and extracellular quantification of cystine and other metabolites differentially expressed in knock-out and control cells. Various assays were applied to monitor the lysosomal-autophagy dynamics (TFEB, LC3-II and DQ-BSA) in ciPTEC.

Results

The CTNS-/- isogenic cell line of ciPTEC showed a significant increase in cystine accumulation compared to healthy control cells (6.32 vs. 0.05 nmol/mg protein; p<0.001). Upon treatment with cystine depleting drug cysteamine, CTNS-/- cells showed a significant reduction in cystine levels (0.74 nmol/mg protein; p<0.01). Using metabolomics, we identified that not only cystine but also >25 metabolites and 9 metabolic pathways were affected (p<0.05) in cystinotic cells. CTNS-/- cells demonstrated an abnormally increased autophagy, confirmed by the increased TFEB nuclear translocation (2-fold; p<0.05), increased accumulation of LC3-II (2.3-fold; p<0.05) and increased lysosomal degradation of DQ-BSA (2-fold; p<0.05). Of note, cysteamine had no effect on the restoration of autophagy, which might explain its limited effect on treating renal Fanconi syndrome. However, a promising registered drug molecule was found to be effective either alone or in combination with cysteamine in resolving cystinotic manifestations.

Conclusion

We developed a genetically engineered cystinotic cell model with isogenic controls. These cells provide a novel versatile tool to study the pathology of cystinosis and develop screens for drugs with the potential to reverse the symptoms. Metabolomics allowed an unbiased analysis of potential new targets for treatment of cystinosis.

Funding

  • Government Support - Non-U.S.