Abstract
Purpose :
We have previously reported that aged mice have decreased corneal innervation and dry eye, suggesting that aging has a negative impact on corneal nerves. The purpose of this study was to investigate the molecular pathways used by corneal epithelial cells to support corneal nerves and epithelial cells in young and aged mice and to investigate corneal epithelialization after a cornea sterile wound.
Methods :
Corneal epithelium of female C57BL/6J (B6) mice of different ages [2, -12, -18, and 24M (months)] was scrapped and subjected to gene expression analysis using bulk RNA sequencing and ROSALIND software. Cornea sensitivity was measured using the Cochet Bonnet in 2M and 18M mice. Both male and female B6 mice (2M and 18M) were subjected to unilateral corneal debridement using a blunt blade. Wound size was visualized and photographed at different time points (1, 20-, 24-, 28-, and 48h and 14 and 21-days post-injury) using a digital camera. The re-epithelization rate was calculated by comparing the measurements to the 1-hour time point, which was set as 100%. Fluorescein staining gray levels of the right and left corneas were visualized and photographed on day 14.
Results :
Bulk RNA sequencing showed that the number of differentially expressed genes increased with aging (64, 12M), (94, 18M), (119, 24M) when compared to 2M. Downregulated pathways included wound healing, blood vessel development, sensory perception, negative regulation of peptidase and hydrolase activity. Upregulated pathways included negative regulation of protein phosphorylation, hormone metabolic processes, regulation of protein kinase activity and protein stability. Cornea sensitivity was decreased in aged mice compared to young (p<0.001). 18M mice had delayed corneal re-epithelialization after corneal wound debridement in the first 48h and worse corneal fluorescein staining intensity at day 14 compared to the 2M mice (p=0.04, p=0.01, respectively). There were no sex differences between male and female mice. 18M mice still had open wounds compared to young mice (44.4%, 6.7%, p=0.01) at day 21.
Conclusions :
The corneal epithelium shows altered pathways with increasing aging. 18M mice have significantly slower wound healing rate and display signs of dry eye disease 14 days post-initial wound. These results indicate that aging is a significant risk factor for corneal disease.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.