Downregulation of the core circadian gene Nr1d2 in the lacrimal gland contributes to postoperative dry eye disease by impairing lipid metabolism

Purpose

Dry eye disease (DED) is a prevalent complication after refractive surgery, and its underlying mechanisms are not fully understood. Given that circadian rhythm tightly regulates tear secretion, this study aims to investigate the circadian changes in the lacrimal gland after corneal refractive surgery and the associated mechanisms.

Methods

C57/BL6 mice underwent corneal epithelial abrasion and stromal severing. DED was assessed using phenol red thread and fluorescein staining. RNA sequencing identified differentially expressed genes (DEGs) related to circadian rhythm, validated by RT-qPCR and Western blotting. Immunofluorescence, TUNEL staining, untargeted metabolomics, Oil-Red-O staining, and TEM were performed to analyze the lacrimal gland changes. Clinically, DED symptoms were evaluated using the OSDI questionnaire in 867 post-surgical patients and 705 controls.

Results

Corneal epithelial abrasion and stromal severing induced DED symptoms and lacrimal dysfunction, including reduced tear volume, ocular surface inflammation, and lacrimal pathophysiological changes. Nr1d2, the key circadian rhythm gene, was significantly down-regulated in the lacrimal gland compared to the control. Activation of Nr1d2 with SR9011 restored the lacrimal gland function and alleviated DED symptoms. Furthermore, the down-regulation of Nr1d2 significantly impaired lipid metabolism and mitochondrial function in the lacrimal gland, which SR9011 reversed. Clinically, the incidence of DED was markedly higher in the surgical cohort, with symptom occurrence exhibiting diurnal variation and peaking in the early morning and late evening.

Conclusions

Disruption of circadian rhythms, specifically Nr1d2 downregulation, contributes to post-surgical DED. Targeting Nr1d2 may offer a novel therapeutic approach to restore lacrimal gland function and alleviate DED.