Therapeutic Effects of Topical Application of Lycium barbarum Polysaccharide in a Murine Model of Dry Eye

Abstract

Purpose: To evaluate the safety and efficacy of Lycium barbarum polysaccharide (LBP) eye drops in a murine model of dry eye disease (DED).

Methods: Six- to eight-week-old female C57BL/6 mice were subjected to a combination of desiccating stress (DS) and topical benzalkonium chloride (BAC) to induce DED. Five microliters of LBP eye drops (0.625, 2.5, or 12.5 mg/ml) or PBS was applied topically 3 times per day for 10 days to subsequently test their efficacy. Tear secretion, tear breakup time (TBUT), corneal irregularity, and corneal fluorescein staining scores were measured on days 3 and 10 after treatment. The expression of tumor necrosis factor-alpha (TNF-α) in the cornea was assessed by quantitative (q) RT-PCR on days 10. The ocular irritation of LBP eye drops of corresponding concentrations was evaluated on 10- to 12-week-old female Sprague-Dawley rats.

Results: Compared with PBS-treated groups, mice treated with 0.625, 2.5, and 12.5 mg/ml LBP showed a significant improvement in the clinical signs of DED in a dose-dependent manner, including corneal epithelial integrity, corneal regularity, and tear production, as well as significant inhibition of inflammatory cell infiltration and TNF-α expression levels in the cornea. All corresponding concentrations of LBP eye drops revealed no obvious ocular irritation.

Conclusion: Topical application of LBP could ameliorate dry eye in a murine model of DED without obvious ocular irritation.

Keywords: Lycium barbarum polysaccharide; cornea; dry eye disease; inflammation; ocular surface.

FIGURE 1

The effects of topical application of LBP on corneal epithelial integrity and regularity in a mouse DED model. (A) Representative images of corneal fluorescein staining in different groups on days 3 and 10 after treatment. (B) The results of corneal fluorescein staining scores of different groups on days 3 and 10 after treatment. (C) Representative images of corneal irregularity in different groups on days 3 and 10 after treatment. (D) The comprehensive results of corneal irregularity scores of different groups on days 3 and 10 after treatment. Data were shown as median (IQR). *P < 0.05, ^***P < 0.001, ^****P < 0.0001.

FIGURE 2

(A) The effects of topical application of LBP on the tear secretion rate on days 3 and 10 after treatment. (B) The effects of topical application of LBP on TBUTs on days 3 and 10 after treatment. Data of tear secretion rate were shown as the mean ± SD. Data of TBUTs were shown as median (IQR). *P < 0.05, ^**P < 0.01, ^****P < 0.0001.

FIGURE 3

(A) Representative images of H&E staining in the cornea and limbus of different groups on days 10 after treatment. The arrows showed corneal conjunctivization (magnification: 40×). (B) The inflammatory cell count in the cornea and limbus of different groups on days 10 after treatment. ^****P < 0.0001.

FIGURE 4

The effects of topical application of LBP on the relative expression level of TNF-α mRNA in the cornea. Data were shown as the mean ± SD. *P < 0.05, ^**P < 0.01.

FIGURE 5

Representative images of H&E staining of ocular tissues on days 7. (A) the cornea; (B) the limbus; (C) the iris; (D) the bulbar conjunctiva; (E) the fornix conjunctiva (magnification: 40×).