AUTHOR=Alam Jehan , Yazdanpanah Ghasem , Ratnapriya Rinki , Borcherding Nicholas , de Paiva Cintia S. , Li DeQuan , Guimaraes de Souza Rodrigo , Yu Zhiyuan , Pflugfelder Stephen C. 

TITLE=IL-17 Producing Lymphocytes Cause Dry Eye and Corneal Disease With Aging in RXRα Mutant Mouse

JOURNAL=Frontiers in Medicine

VOLUME=Volume 9 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/medicine/articles/10.3389/fmed.2022.849990

DOI=10.3389/fmed.2022.849990

ISSN=2296-858X

ABSTRACT=Purpose: To investigate IL-17 related mechanisms for developing dry eye disease in the Pinkie mouse strain with a loss of function RXR mutation. 
Methods: Measures of dry eye disease were assessed in the cornea and conjunctiva. Expression profiling was performed by single-cell RNA sequencing (scRNA-seq) to compare gene expression in conjunctival immune cells. Conjunctival immune cells were immunophenotyped by flow cytometry and confocal microscopy. The activity of RXR ligand 9-cis retinoic acid (RA) was evaluated in cultured monocytes and  T cells. 
Results: Compared to wild type (WT) C57BL/6, Pinkie has increased signs of dry eye disease, including decreased tear volume, corneal barrier disruption, corneal/conjunctival cornification and goblet cell loss, and corneal vascularization, opacification, and ulceration with aging. ScRNA-seq of conjunctival immune cells identified  T cells as the predominant IL-17 expressing population in both strains and there is a 4-fold increased percentage of  T cells in Pinkie. Compared to WT, IL-17a and IL-17f significantly increased in Pinkie with conventional T cells and   T cells as the major producers. Flow cytometry revealed an increased number of IL-17+  T cells in Pinkie. Tear concentration of the IL-17 inducer IL-23 is significantly higher in Pinkie. 9-cis RA treatment suppresses stimulated IL-17 production by  T and stimulatory activity of monocyte supernatant on  T cell IL-17 production. Compared to WT bone marrow chimeras, Pinkie chimeras have increased IL-17+  T cells in the conjunctiva after desiccating stress and anti-IL-17 treatment suppresses dry eye induced corneal MMP-9 production/activity and conjunctival goblet cell loss. 
Conclusion: These findings indicate that RXR suppresses generation of dry eye disease-inducing IL-17 producing lymphocytes s in the conjunctiva and identifies RXR as a potential therapeutic target in dry eye.