Abstract
Purpose :
To evaluate appearance, morphology, lipid composition and IL-17+ gamma delta T cells in meibomian glands (MG) of the retinoic acid receptor X alpha (RXRα) mutant Pinkie mouse strain.
Methods :
Lid margins and MGs were imaged at 8 and 40 weeks of age in wild type (WT) C57BL/6 and RXRα mutant Pinkie strains. MG lipid was stained with oil red O and LipidtoxTM. Immunostaining for cornified envelope precursor SPRR2, gamma delta (gd) T cell receptor and IL-17 was performed in cryosections and whole mounts. Lipidomic analysis of MG lipid samples from age-matched mice was performed by liquid chromatography—mass spectrometry, the data were analyzed using unbiased multivariate statistical techniques, and the data for major components were verified using targeted lipidomic approaches.
Results :
Compared to WT, Pinkie develops elevated MG orifices, and has increased SPRR2 staining of the lid margin (Fig Panel A), and MG ducts and acini. The number of oil red O-stained MG acini is lower in aged Pinkie. Greater accumulation of LipidtoxTM positive lipid is noted in the MG ducts and lid margins of aged Pinkie. The number of IL-17+ gd T cells surrounding the MGs is increased in aged Pinkie. There were changes in MG lipid composition between age-matched B6 and Pinkie mice. The Principal Component and the Orthogonal Projections to Latent Structures Discriminant analyses resulted in two distinctive groups of samples (Fig Panel B). While the overall amounts of MG lipid were comparable in both strains, statistically significant increases in the KO/WT lipid ratios were observed for free cholesterol and extremely long chain wax esters, while the molar ratios of major triglycerides declined in mutant mice (p<0.05 for all observations).
Conclusions :
The RXRα mutant develops altered MG morphology associated with reduced lipid filled MG acini, altered lipid composition, and increased IL-17 producing gd T cells surrounding the MGs with aging. These findings suggest RXRα signaling maintains MG lipid homeostasis and suppresses inflammation.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.