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bioRxiv · 10.1101/2021.06.29.450444

Cystinosin deficient rats recapitulate the phenotype of nephropathic cystinosis

Hollywood, J. A.·Kallingappa, P. K.·Cheung, P. Y.·Martis, R. M.·Sreebhavan, S.·Chatterjee, A.·Buckels, E. J.·Matthews, B. G.·Lewis, P. M.·Davidson, A. J.
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Abstract

BackgroundThe lysosomal storage disease cystinosis is caused by mutations in CTNS, encoding a cystine transporter, and in its severest form leads to proximal tubule dysfunction followed by kidney failure. Patients receive the drug-based therapy cysteamine from diagnosis. However, despite long-term treatment, cysteamine only slows the progression of end-stage renal disease and a kidney transplant is inevitable. Pre-clinical testing in cystinotic rodents is required to evaluate new therapies; however, the current models are sub-optimal. To solve this problem we generated a new cystinotic rat model. MethodsWe utilized CRISPR/Cas9-mediated gene editing to disrupt exon 3 of Ctns and measured various parameters over a 12-month time-course including blood and tissue cystine levels, urine and serum electrolytes, and analysed the histopathology and immunohistochemistry of the kidney. ResultsCtns-/- rats display hallmarks of cystinosis by 3-6 months of age as seen by a failure to thrive, excessive thirst and urination, cystine accumulation in tissues, corneal cystine crystals, a loss of Lrp2 in proximal tubules and immune cell infiltration. High levels of glucose, calcium, albumin and protein are excreted at 6-months of age, consistent with the onset of Fanconi syndrome, with a progressive diminution of urine urea and creatinine from 9-months of age, indicative of chronic kidney disease. The kidney histology and immunohistochemistry showed proximal tubule atrophy and glomerular damage as well as classic swan neck lesions. Overall, Ctns-/- rats show a disease progression that more faithfully recapitulates nephropathic cystinosis than existing rodent models. ConclusionsThe Ctns-/- rat provides an excellent new rodent model of nephropathic cystinosis that is ideally suited for conducting pre-clinical drug testing and a powerful tool to advance cystinosis research. Translational StatementGood animal models of disease are essential to perform pre-clinical testing of potential new drugs and therapies before they can progress to human clinical trials. Unfortunately, the cystinosis field has been hampered by a lack of suitable animal models that fully recapitulate the disease. We have overcome this by generating a new rat model of cystinosis by CRISPR-Cas9 gene editing. These rodents closely model the human condition in a time-frame that makes them an excellent model ideally suited for pre-clinical drug testing as well as being a powerful tool to advance cystinosis research.

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Hollywood, J. A., Kallingappa, P. K., Cheung, P. Y., Martis, R. M., Sreebhavan, S., Chatterjee, A., Buckels, E. J., Matthews, B. G., Lewis, P. M., Davidson, A. J.. 2021-06-30. Cystinosin deficient rats recapitulate the phenotype of nephropathic cystinosis. https://doi.org/10.1101/2021.06.29.450444

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