A 3D Renal Proximal Tubule on Chip Model Phenocopies Lowe Syndrome and Dent II Disease Tubulopathy.

Sindhu Naik,Richard Janssen,Paniz Saidiyan,Maté Ongenaert,Jan Stallen,Kai S Erdmann,Andrew R Wood,Edo D Elstak,Henriëtte L Lanz,Elizabeth Smythe

doi:10.3390/ijms22105361

Abstract

Lowe syndrome and Dent II disease are X-linked monogenetic diseases characterised by a renal reabsorption defect in the proximal tubules and caused by mutations in the OCRL gene, which codes for an inositol-5-phosphatase. The life expectancy of patients suffering from Lowe syndrome is largely reduced because of the development of chronic kidney disease and related complications. There is a need for physiological human in vitro models for Lowe syndrome/Dent II disease to study the underpinning disease mechanisms and to identify and characterise potential drugs and drug targets. Here, we describe a proximal tubule organ on chip model combining a 3D tubule architecture with fluid flow shear stress that phenocopies hallmarks of Lowe syndrome/Dent II disease. We demonstrate the high suitability of our in vitro model for drug target validation. Furthermore, using this model, we demonstrate that proximal tubule cells lacking OCRL expression upregulate markers typical for epithelial–mesenchymal transition (EMT), including the transcription factor SNAI2/Slug, and show increased collagen expression and deposition, which potentially contributes to interstitial fibrosis and disease progression as observed in Lowe syndrome and Dent II disease.

Highlights

Accepted: 18 May 2021Lowe syndrome is an X-linked monogenetic human disease mainly affecting the eye, brain, and kidney and, is known as oculocerebrorenal syndrome, which gave rise to the name OCRL for the gene mutated in Lowe syndrome [1,2]
We reveal that proximal tubule cells lacking OCRL demonstrate upregulation of epithelial–mesenchymal transition (EMT) marker proteins and increased collagen deposition, which may contribute to interstitial fibrosis as observed in Lowe syndrome patients
In order to develop an organ on chip model for Lowe syndrome, we first engineered a suitable cellular model for Lowe syndrome by deleting OCRL protein expression in the human proximal tubule cell line HK-2 using CRISPR/Cas9

Summary

Introduction

Lowe syndrome is an X-linked monogenetic human disease mainly affecting the eye, brain, and kidney and, is known as oculocerebrorenal syndrome, which gave rise to the name OCRL for the gene mutated in Lowe syndrome [1,2]. Mutations in OCRL can be found in a subset of Dent disease patients, which led to the establishment of a Dent II disease category for these patients [3,4]. Dent disease patients show a very similar renal phenotype but differ from Lowe syndrome patients by not showing a major phenotype in the nervous system or eye. Lowe syndrome and Dent II disease patients both show a progressive reabsorption defect in the kidney that often leads to complete kidney failure and which is the main cause for increased mortality observed in Lowe syndrome patients [5,6]. OCRL has been shown to play a major role as a regulator of intracellular trafficking, in particular

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Conclusion