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Applied desiccated stress leads to a decrease in ocular surface epithelial cells and limbal epithelial stem cell stress in mouse models, according to research published in The Ocular Surface.
Clinicopathological outcomes following desiccation stress in animal models have been well-documented, but the study says researchers have thus far under-investigated the effect of limbal epithelial stem cells in offspring. To address this, researchers promoted desiccation stress to characterize subsequent effects on the murine ocular surface through clinical and histopathological assessments.
Mice lived in a customized isolated transit unit under dehumidified conditions for the course of the 10-day experiment. Mice were anesthetized at baseline, day 5, and day 10 to undergo phenol red tear thread testing and sodium fluorescein (1 µl of 0.1%) into the right eye, followed by imaging to view staining. Optical coherence tomography was also performed on desiccation stress exposed mouse corneas using the same imaging system with anterior segment attachments.
General appearance and bodyweight measurements were used to assess how desiccation stress levels impacted health and wellbeing. All mice demonstrated normal physiological behavior, but a statistically significant difference in bodyweight was noted between untreated mice and those under desiccation stress (0.00909±0.267% vs -9.16±3.53%) on days 1 through 9.
At baseline, no difference in phenol red tear thread testing between the two groups was noted; tear production decreased between the groups at days 5 and 10 (1.73±0.676 mm vs 0.167±0.160 mm and 1.51±0.800 mm vs 0.132±0.136 mm, respectively).
Fluorescein dye uptake was also determined between the groups. In unrinsed corneas, a significant dye staining increase was seen when comparing untreated vs desiccated stress mice (26.4±16.6 spots vs 46±16.8 spots) at 10 days. Following rinsing, desiccated stress mice showed greater fluorescein dye uptake vs untreated controls (11±7.90 spots vs 2±0.0984 spots).
Researchers also conducted immunopathological and histopathological assessment of the ocular surface in desiccated stress exposed mice who displayed features of dry eye disease. Tissue sections were stained for corneal, conjunctival, and cutaneous biomarkers; researchers noted no phenotype changes across ocular surface epithelia. Due to histological anomalies, investigators assumed that this response was stress related.
Data raised suspicions that desiccated stress exposure influenced corneal thickness. Anesthetized mice underwent intravitreal anterior segment OCT imaging, which were visually reviewed at day 10. No gross structural differences in the corneas were seen in either group. In untreated corneas, central epithelial thickness showed significant increases between baseline and day 10 (35.1±2.88 µm to 40.2±1.17 µm); central stromal thickness also increased (55.8±5.76 µm vs 67.7±2.20 µm) in corneas from resected mice.
“Following desiccation stress, ocular surface epithelial cell health decreased and limbal epithelial stem cells appeared stressed,” according to researchers. “This suggested that potential downstream effects of desiccation stress on corneal homeostasis are present, a phenomenon that is currently under-investigated.”
“The method used to induce dry eye disease in this study enables the development of a chronic model which more closely resembles disease seen in the clinic,” the study concludes.
Reference
Zhang R, Pandzic E, Park M, Wakefield D, Di Girolamo N. Inducing dry eye disease using a custom engineered desiccation system: Impact on the ocular surface including keratin-14-positive limbal epithelial stem cells. Ocul Surf. Published online April 27, 2021. doi:10.1016/j.jtos.2021.04.006
