Rescue of chloride and bicarbonate transport by elexacaftor-ivacaftor-tezacaftor in organoid-derived CF intestinal and cholangiocyte monolayers

Kelly F. Meijsen,Monique M.A. Verstegen,Henk P. Roest,Marcel J.C. Bijvelds,Hettie M. Janssens,Luc J.W. van der Laan,Floris J.M. Roos,Hugo R. de Jonge

doi:10.1016/j.jcf.2021.12.006

Kelly F. Meijsen, Monique M.A. Verstegen + Show 6 more

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https://doi.org/10.1016/j.jcf.2021.12.006

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Abstract

BackgroundIn cystic fibrosis (CF), loss of CF transmembrane conductance regulator (CFTR)-dependent bicarbonate secretion precipitates the accumulation of viscous mucus in the lumen of respiratory and gastrointestinal epithelial tissues. We investigated whether the combination of elexacaftor (ELX), ivacaftor (IVA) and tezacaftor (TEZ), apart from its well-documented effect on chloride transport, also restores Phe508del-CFTR-mediated bicarbonate transport. MethodsEpithelial monolayers were cultured from intestinal and biliary (cholangiocyte) organoids of homozygous Phe508del-CFTR patients and controls. Transcriptome sequencing was performed, and bicarbonate and chloride transport were assessed in the presence or absence of ELX/IVA/TEZ, using the intestinal current measurement technique. ResultsELX/IVA/TEZ markedly enhanced bicarbonate and chloride transport across intestinal epithelium. In biliary epithelium, it failed to enhance CFTR-mediated bicarbonate transport but effectively rescued CFTR-mediated chloride transport, known to be requisite for bicarbonate secretion through the chloride-bicarbonate exchanger AE2 (SLC4A2), which was highly expressed by cholangiocytes. Biliary but not intestinal epithelial cells expressed an alternative anion channel, anoctamin-1/TMEM16A (ANO1), and secreted bicarbonate and chloride upon purinergic receptor stimulation. ConclusionsELX/IVA/TEZ has the potential to restore both chloride and bicarbonate secretion across CF intestinal and biliary epithelia and may counter luminal hyper-acidification in these tissues.

Highlights

Accumulation of viscous mucus in the respiratory, intestinal and biliary tract is a hallmark of cystic fibrosis (CF), and is the primary cause of defective mucociliary clearance in the airways and of luminal obstruction in gastrointestinal epithelia [1,2,3,4]
Bicarbonate is transported by the CF-gene encoded cystic fibrosis transmembrane conductance regulator (CFTR) channel and by chloride-bicarbonate exchangers that are functionally coupled to CFTR [6]
Gene expression was analyzed by transcriptome sequencing of representative CF and non-CF monolayer cultures of cholangiocyte and intestinal organoids (Fig. 1)

Summary

Introduction

Accumulation of viscous mucus in the respiratory, intestinal and biliary tract is a hallmark of cystic fibrosis (CF), and is the primary cause of defective mucociliary clearance in the airways and of luminal obstruction in gastrointestinal epithelia [1,2,3,4]. In cystic fibrosis (CF), loss of CF transmembrane conductance regulator (CFTR)-dependent bicarbonate secretion precipitates the accumulation of viscous mucus in the lumen of respiratory and gastrointestinal epithelial tissues. Transcriptome sequencing was performed, and bicarbonate and chloride transport were assessed in the presence or absence of ELX/IVA/TEZ, using the intestinal current measurement technique. Results: ELX/IVA/TEZ markedly enhanced bicarbonate and chloride transport across intestinal epithelium. In biliary epithelium, it failed to enhance CFTR-mediated bicarbonate transport but effectively rescued CFTR-mediated chloride transport, known to be requisite for bicarbonate secretion through the chloridebicarbonate exchanger AE2 (SLC4A2), which was highly expressed by cholangiocytes. Conclusions: ELX/IVA/TEZ has the potential to restore both chloride and bicarbonate secretion across CF intestinal and biliary epithelia and may counter luminal hyper-acidification in these tissues

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