Ultrastructural changes in ageing lacrimal gland in Wistar rats

Differential response to topical lubrication in patient with dry eye disease, based on age

BACKGROUND

To compare the Ocular surface disease index (OSDI) score, Schirmer I test (SIT), fluorescein break up time (FBUT) and fluorescence staining (FLCS) score of dry eye patients at different ages.

METHODS

90 eyes of 90 patients with mild to moderate dry eye from September 2020 to September 2021 were retrospectively included and were divided into young group (20-39 years, n = 29), middle-age group (40-59 years, n = 30), and elder group (> 60 years, n = 31). Patients were given a 28-day topical lubricating ocular surface and repair-promoting drugs combined with local physical therapy. Patients were followed up at 7, 14 and 28 days. The OSDI score, SIT, FBUT and FLCS score were examined.

RESULTS

There were differences between the OSDI score in three groups at each time point (all P < 0.001). SIT were different among the three groups (F = 350.61, P < 0.001), and a time effect was found (F = 80.87, P < 0.001). SIT at 14 and 28 days after treatment in middle-age and elder groups were lower than young group (all P < 0.001). SIT at 7, 14 and 28 days in elder group were lower than middle-age group (all P < 0.001). FLCS score was lower at 28 days than other time points (all P < 0.001).

CONCLUSION

Dry eye patients are given a 28-day topical lubricating ocular surface and repair-promoting drugs combined with local physical therapy, which can promote tear secretion, film stability, and the recovery of corneal integrity. Age affects the treatment effect of mild to moderate dry eye, among which tear secretion is the most significant.

N-Palmitoylethanolamine Maintains Local Lipid Homeostasis to Relieve Sleep Deprivation-Induced Dry Eye Syndrome

Sleep loss is a key factor associated with dry eye. Use of a “stick over water” mouse model revealed that sleep deprivation induces accumulation of lipids, hypertrophy, and dysfunction of the lacrimal gland. These changes result in decreased tear production and dry eye clinical signs. The specific pathophysiological mechanisms that contribute to dry eye remain unclear. In this study, we found that sleep deprivation decreased endogenous lipid palmitoylethanolamide (PEA) expression in the lacrimal gland. The reduced expression was mainly attributed to the decreased expression of N-acylated phosphatidylethanolamine–phospholipase D, the synthetic enzyme of PEA. Exogenous PEA treatment restored local lipid metabolism homeostasis in the lacrimal gland. This change was accompanied by reduced lipid deposition, maintenance of the endoplasmic reticulum and mitochondrial morphology, and improved acinar cell secretory function. PEA treatment also prevented damage to corneal barrier function and improved the dry eye clinical signs caused by sleep deprivation. The nuclear receptor peroxisome proliferator-activated receptor-α (PPAR-α) was found to mediate the PEA-associated improvements. We describe here for the first time that PEA is involved in sleep deprivation–induced lacrimal gland pathogenesis and dry eye development. PEA and its metabolizing enzymes may serve as adjunctive therapeutic targets for treatment of dry eye.

Mitochondria-targeted antioxidant SkQ1 reduces age-related alterations in the ultrastructure of the lacrimal gland

Dry eye syndrome is an eye disorder affecting many people at an old age. Because dry eye syndrome is accelerated by aging, a useful approach to the prevention of this syndrome may be an intervention into the aging process. Previously, we showed that the mitochondria-targeted antioxidant SkQ1 delays manifestations of aging and inhibits the development of age-related diseases including dry eye syndrome. Nevertheless, the link between SkQ1's effects and its suppression of age-related changes in the lacrimal gland remains unclear. Here we demonstrated that dietary supplementation with SkQ1 (250 nmol/[kg body weight] daily) starting at age 1.5 months significantly alleviated the pathological changes in lacrimal glands of Wistar rats by age 24 months. By this age, lacrimal glands underwent dramatic deterioration of the ultrastructure that was indicative of irreversible disturbances in these glands' functioning. In contrast, in SkQ1-treated rats, the ultrastructure of the lacrimal gland was similar to that in much younger rats. Morphometric analysis of electron-microscopic specimens of lacrimal glands revealed the presence of numerous secretory granules in acinar cells and a significant increase in the number of operating intercalary ducts. Our results confirm that dietary supplementation with SkQ1 is a promising approach to healthy ageing and to prevention of aberrations in the lacrimal gland that underlie dry eye syndrome.

Lacrimal Gland Inflammation Deregulates Extracellular Matrix Remodeling and Alters Molecular Signature of Epithelial Stem/Progenitor Cells

PURPOSE

The adult lacrimal gland (LG) is highly regenerative and is able to repair itself even after substantial damage; however, this ability to regenerate is lost with the development of dry eye conditions in chronically inflamed LGs.This study compares changes in the cell adhesion and cell matrix molecules and stem cell transcription factors in the LGs of healthy mice and of two mouse models of Sjögren's syndrome: nonobese diabetic (NOD) and MRL-lpr/lpr (MRL/lpr) mice during the early stage of inflammation.

METHODS

The LGs from 12- to 13-week-old female MRL/lpr and male NOD mice along with their respective control strains were harvested and divided into three pieces and processed for quantitative (q) RT-PCR and qRT-PCR Arrays, histology, immunohistochemistry, and Western blotting.

RESULTS

The extracellular matrix (ECM) and adhesion molecules RT2-PCR array combined with protein expression data revealed changes in the expression of integrins, matrix metalloproteinases, and other molecules, which are associated largely with invasion, attachment, and expansion of the lymphocytic cells, whereas changes in the stem cell transcription factors revealed substantial decrease in expression of transcription factors associated with epithelial stem/progenitor cell lineage.

CONCLUSIONS

We concluded that the expression of several important ECM components is significantly deregulated in the LG of two murine models of Sjögren's syndrome, suggesting an alteration of the epithelial stem/progenitor cell niche. This may result in profound effects on localization, activation, proliferation, and differentiation of the LG stem/progenitor cells and, therefore, LG regeneration.