Abstract
Purpose: :
The prevalence of ocular surface disease increases with advancing age and is associated with increasing meibomian gland atrophy and altered secretion profiles. The purpose of this study was to characterize the effects of age on the mouse meibomian gland as a potential model for studying age-related meibomian gland disease.
Methods: :
Eyelids from C57Bl/6 mice were collected at 2 months, 6 months, and 2 years of age. Eyelids were fixed in 2% paraformaldehyde, equilibrated with increasing concentrations of sucrose up to 30%, embedded in OCT and frozen in liquid nitrogen. Frozen sections (10 µm) were then stained with antibodies specific for B-lymphocyte-induced maturation protein 1 (BLIMP1), leukocyte common antigen (CD45), peroxisome proliferator activated receptor gamma (PPARγ) and Oil Red O (ORO). Additional tissue was embedded in LR White acrylic resin and serially sectioned (1µm) for 3D reconstruction and measurement of meibomian gland volume. All sections were imaged using a Nikon Eclipse E600 microscope. Digital images were analyzed using Metamorph 7.0. Image J was used to convert the serial sections into a aligned stack with StackReg.
Results: :
Meibomian glands from aged mice (2 years) showed positive BLIMP1 and CD45 stained cells within the acini and ductal epithelium, suggesting the presence of B-cells, i.e. plasmacytoid cells, in older meibomian glands. Meibomian glands from younger mice (2 months and 6 months) showed cytoplasmic and nuclear anti-PPARγ staining, while glands from aged mice (2 years) showed a predominantly nuclear anti-PPARγ localization. ORO staining of lipid within meibomian gland acinar cells showed abundant small lipid droplets in young meibomian glands associated with developing meibocytes while meibomian glands from older mice (2 years) showed fewer smaller lipid droplets and more intensely stained, enlarged lipid droplets associated with an apparent reduction in acinar gland tissue and increased ductal epithelial tissue.
Conclusions: :
Our results demonstrated age-related changes in mouse meibomian gland including increased lymphocytic infiltration with plasmacytoid cells, decreased meibocyte differentiation and reduced lipid production, suggesting a possibility of enhanced immune response in aged mice. Taken together, these results suggest aging mouse meibomian glands undergo age-related changes similar to those identified in human that may play a role in age-related dry eye disease.
Keywords: cornea: tears/tear film/dry eye • aging • imaging/image analysis: non-clinical