Dendrobium officinale kimura et migo improved dry eye symptoms via promoting tear production in an experimental dry eye rat model

Objectives: To evaluate the ameliorative effect of Dendrobium officinale Kimura et Migo (DO) on a desiccated environment-induced experimental dry eye rat model and elucidate its underlying mechanisms. Materials and Methods: The Sprague-Dawley rats were kept in low-humidity environment and received constant airflow for 8 weeks to establish the experimental dry eye model. DO water extract (DOW, 372 mg/kg/day) was orally administered daily for 8 weeks. Schirmer's test was used to measure the tear fluid production at days 0, 14, 28, 42, and 56. At the end of experiment, lacrimal gland tissues and eyeballs were collected for hematoxylin and eosin staining, PAS staining, and immunohistochemical staining. Inflammatory cytokines in conjunctiva including tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), IL-6, and matrix metalloproteinase 9 were measured by real-time PCR. The aquaporin 5 (AQP5) expression in lacrimal gland was also determined using Western blot assay. Results: DOW treatment (DOWT) increased the tear production of rats significantly in the desiccated environment at day 42. Histological analysis revealed that DOW could reverse destruction of conjunctiva and increase goblet cell number and mucin expression in the experimental dry eye rats. In dry eye rats, desiccated environment and constant airflow induced TNF-α and IL-1β production in the conjunctiva, whereas DOWT reversed the upregulation of proinflammatory cytokines. Moreover, DOWT increased the expression of AQP5 at protein level in the lacrimal gland tissues in both desiccated and normal environmental conditions. Conclusion: The present study suggests that DO has therapeutic potential on dry eye symptoms through upregulating AQP5 expression, increasing tear production, inhibiting conjunctiva destruction and inflammation, as well as promoting mucin production.