ABSTRACT
Purpose: Ocular surface discomfort and dry eye disease are caused by a dysfunctional tear film. The efficacy of lubricating eye drops on the human eye is known, but the compositions may show differential effects on rescuing the tear film. Mucins form a critical layer of the tear film, a reduction of which may be causative for ocular surface conditions. Therefore, it is essential to develop relevant human?derived models to test mucin production. Methods: Human corneoscleral rims were obtained from a healthy donor (n = 8) post?corneal keratoplasty and cultured in DMEM/F12 media. Hyperosmolar stress mimicking dry eye disease was induced by exposing the corneoscleral rim tissues to +200 mOsml NaCl?containing media. The corneoscleral rims were treated with polyethylene glycol–propylene glycol (PEG–PG)?based topical formulation. Gene expression analysis was performed for NFAT5, MUC5AC, and MUC16. Secreted mucins were measured by enzyme?linked immunosorbent assay (ELISA) (Elabscience, Houston, TX, USA) for MUC5AC and MUC16. Results: The corneoscleral rims responded to hyperosmolar stress by upregulating NFAT5, a marker for increased osmolarity, as observed in the case of dry eye disease. The expression of MUC5AC and MUC16 was reduced upon an increase in hyperosmotic stress. The corneoscleral rim tissues showed induction of MUC5AC and MUC16 expression upon treatment with PEG–PG topical formulation but did not show significant changes in the presence of hyperosmolar treatments. Conclusion: Our findings showed that PEG–PG?based topical formulation slightly alleviated hyperosmolar stress?induced decrease in MUC5AC and MUC16 gene expression that is encountered in DED
ABSTRACT
Purpose: Dry eye disease (DED) is characterized by altered ocular surface proinflammatory and antiinflammatory factors. Interferons (IFNs) are a class of pleiotropic cytokines well known for their antimicrobial, inflammatory, and immunomodulatory roles. Hence, this study investigates the ocular surface expression of different types of IFNs in patients with DED. Methods: The cross?sectional, observational study included patients with DED and normal subjects. Conjunctival impression cytology (CIC) samples were obtained from the study subjects (controls, n = 7; DED, n = 8). The mRNA expression levels of type 1 IFN (IFN?, IFN?), type 2 IFN (IFN?), and type 3 IFN (IFN?1, IFN?2, IFN?3) were measured by quantitative PCR (polymerase chain reaction) in CIC samples. IFN? and IFN? expression under hyperosmotic stress was also studied in human corneal epithelial cells (HCECs) in vitro. Results: The mRNA expression levels of IFN? and IFN? were significantly lower and that of IFN? was significantly higher in DED patients compared to healthy controls. The mRNA levels of IFN?, IFN?, and IFN? were significantly lower compared to IFN? in DED patients. An inverse association between tonicity?responsive enhancer?binding protein (TonEBP; hyperosmotic stress maker) and IFN? or IFN? expression and a positive association between TonEBP and IFN? expression was observed in CIC samples. The expression of IFN? was lower than IFN? in HCECs undergoing hyperosmotic stress compared to HCECs without the stress. Conclusion: The presence of an imbalance between type 1 and type 2 IFNs in DED patients suggests newer pathogenic processes in DED, plausible ocular surface infection susceptibility in DED patients, and potential therapeutic targets in the management of DED