Influence of BAKs on Tear Film Lipid Layer: in vitro and in silico models

In vitro biophysical and biological profiling of commercial lipid-based dry eye products

There is an increasing number of products available for treatment of dry eye disease (DED), thereby creating a challenge in selecting a suitable product. Commercial products have rarely been studied in the same experimental setup, and in the case of lipid-based products, their baseline capabilities to target central defects of DED requires a more thorough investigation. This study aims to discern potential differences in their abilities to stabilize the tear film, reduce the evaporation of water, and impact on corneal epithelial cell viability and recovery utilizing various biophysical and biological in vitro techniques. Seven commercial lipid-based eye drops (Cationorm®, Desodrop®, Evotears®, Oxyal® Triple Action, Puro™ Suoja, Systane® Complete, Thealipid®) were selected for the in vitro biophysical and biological profiling studies. Biophysical properties critical for tear film stability and evaporation reduction were evaluated using Langmuir trough techniques, while cell viability and recovery were assessed by an MTT assay after exposing either healthy or damaged human corneal epithelial cells to the products. The majority of the products spread reasonably well at the aqueous-air interface, suggesting that they bear intrinsic properties which may be beneficial to improving the coverage of the tear film lipid layer. However, only subtle evaporation reduction capabilities were observed, indicating that the products are not optimal at targeting this defect. Clear differences in cell viability and recovery were observed, with three of the products being able to promote the recovery of damaged cells. The significance of our findings with regards to DED treatment outcomes will require additional studies in the future.

Characterization of T cells in the progression of dry eye disease using single-cell RNA sequencing in mice

BACKGROUND

Increasing evidence indicated that T cells have significant effects in dry eye disease (DED). However, the regulatory role of T cells in DED remains unclear.

METHODS

In this study, we examined immune responses throughout the progression in murine DED model. Using cytometry by time-of-flight (CyTOF) and single-cell RNA sequencing (scRNA-seq), we observed dynamic alterations in the proportions of immune cell landscape. Pseudotime trajectory and cell-cell communication analyses further illustrated T-cell differentiation and interaction networks.

RESULTS

CD4+ and CD8+ T cells exhibited an initial decline on Day 3 (D3) and followed by a recovery on Day 7 (D7). Single-cell transcriptomics provided insights into 15 distinct subsets of T cells with heterogeneous functional states. Pseudotime trajectory analysis demonstrated coordinated differentiation patterns of CD4+ and CD8+ T cells, indicating their collaborative involvement in the inflammatory process.

CONCLUSIONS

Our results clarify the dynamics of the adaptive immune response in DED and indicate that targeting T cells may serve as a promising immune-modulatory approach in the treatment of DED model.

In Vitro Toxicity of Cetalkonium Chloride on Corneal Epithelial Cells

Objective: To investigate the toxicity of cetalkonium chloride (CKC) on primary cultured human corneal epithelial cells (HCECs). Methods: HCECs were subjected to various concentrations (0.03125 × 10-4 to 2.0 × 10-4% (w/v)) of CKC for durations ranging from 24 to 72 h. Cell viability was evaluated using the CCK-8 kit along with live and dead cell staining. Intracellular reactive oxygen species (ROS) levels were measured 20 min following CKC exposure. Observations of changes in cell morphology, cytoplasmic actin filaments, and mitochondrial distribution were conducted using immunocytochemistry and MitoTracker assays. Protein expression levels related to cell survival pathways, including mTOR, ERK, Akt, Bcl-xL, and BAX, were examined via Western blot analysis. Results: CKC exhibited dose-dependent toxicity in HCECs. Exposure to CKC concentrations below 0.125 × 10-4% resulted in no significant decrease in HCEC viability for up to 72 h. Conversely, exposure to CKC at concentrations of 1.0 × 10-4% or higher led to significantly decreased HCEC viability. Following exposure to higher concentrations of CKC, elevated levels of intracellular ROS and LDH release were observed. This toxicity was further characterized by decreased levels of phosphorylated mTOR, phosphorylated Akt, phosphorylated ERK, and Bcl-xL, as well as an increase in BAX expression. As the CKC concentration increased, HCECs decreased in size, and mitochondria displayed a loss of characteristic punctate staining. Conclusions: Our findings indicated that exposure to CKC caused significant toxicity in HCECs, which varied with concentration and duration of exposure. This toxicity was associated with an increase in ROS, mitochondrial alterations, and a decline in activity of the cell survival pathways.

Global research hotspots and trends in anti-inflammatory studies in dry eye: a bibliometric analysis (2004-2024)

Background

Inflammation plays a crucial role in the pathophysiology of dry eye (DE). This study aims to provide a comprehensive overview of the current status, hotspots and trends in DE anti-inflammatory research through bibliometric analysis.

Method

All publications were searched using the Web of Science Core Collection (WoSCC) database from 2004 to 2024. Bibliometric analyses were performed using VOSviewer, R-bibliometrix, and CiteSpace, and data were managed using Microsoft Office Excel 2019.

Results

There were 603 papers published between 2004 and 2024 included in this study, with the number of papers increasing each year. The United States was the major contributor, with the largest number of publications and the greatest impact. Baylor College of Medicine was the most influential research institution. Pflugfelder, Stephen C. and Tsubota, Kazuo were the most prolific authors in this area of research, while Dana, Reza was the most cited author in the field with the highest impact. The Journal with the highest number of publications was Investigative Ophthalmology & Visual Science, while the highest impact journal was Ocular Surface. Research hotspots were focused on the mechanisms of inflammation in DE and interventions for anti-inflammatory therapy. Future studies would favor more inflammation-related targeted therapies and physical therapies.

Conclusion

This study is the first bibliometric analysis to comprehensively summarize research trends and developments in DE anti-inflammatory treatments, pointing out recent research frontiers and hot directions for scholars studying DE anti-inflammatory treatments.

Mathematical modeling of transdermal delivery of topical drug formulations in a dynamic microfluidic diffusion chamber in health and disease

Mathematical models of epidermal and dermal transport are essential for optimization and development of products for percutaneous delivery both for local and systemic indication and for evaluation of dermal exposure to chemicals for assessing their toxicity. These models often help directly by providing information on the rate of drug penetration through the skin and thus on the dermal or systemic concentration of drugs which is the base of their pharmacological effect. The simulations are also helpful in analyzing experimental data, reducing the number of experiments and translating the in vitro investigations to an in-vivo setting. In this study skin penetration of topically administered caffeine cream was investigated in a skin-on-a-chip microfluidic diffusion chamber at room temperature and at 32°C. Also the transdermal penetration of caffeine in healthy and diseased conditions was compared in mouse skins from intact, psoriatic and allergic animals. In the last experimental setup dexamethasone, indomethacin, piroxicam and diclofenac were examined as a cream formulation for absorption across the dermal barrier. All the measured data were used for making mathematical simulation in a three-compartmental model. The calculated and measured results showed a good match, which findings indicate that our mathematical model might be applied for prediction of drug delivery through the skin under different circumstances and for various drugs in the novel, miniaturized diffusion chamber.

Comparative Study of Latanoprost Drug Delivery Systems for Glaucoma Treatment and Their Interaction with the Tear Film Lipid Layer Models

This study investigates the interaction of two approved and one newly developed latanoprost formulation with in vitro and in silico models of the tear film and tear film lipid layer (TFLL). Latanoprost, a prostaglandin analogue used for intraocular elevated pressure treatment, is topically delivered by nanocarriers within aqueous solutions or emulsions. The study focuses on the impact of these carriers on drug interactions with the tear film and their effect on the TFLL. Three different types of latanoprost carriers, micellar, nanoemulsion, and polymer-based, were compared, and each revealed distinct interaction patterns with the TFLL. Surface pressure kinetics demonstrated a rapid increase for the benzalkonium chloride formulation and a slow rise for the preservative-free variants. Visualization of the acellular in vitro TFLL model revealed different patterns of incorporation for each formulation, indicating unique interaction mechanisms. Molecular dynamics simulations further revealed different mechanisms of drug release in the TFLL between micellar and nanoemulsion formulations. In-depth examination highlighted the role of triglyceride molecules in replenishing the nonpolar layer of the TFLL, which suggests potential improvements in ocular surface compatibility by adjusting the quality and concentration of the oily phase. These findings suggest the potential for optimizing latanoprost formulations by tuning the oily phase-to-surfactant ratio and selecting suitable surfactants.

Latanoprost incorporates in the tear film lipid layer: An experimental and computational model study

Glaucoma is a leading cause of blindness worldwide, with elevated intraocular pressure being a major risk factor for its development and progression. First-line treatment for glaucoma relies on the administration of prostaglandin analogs, with latanoprost being the most widely used. However, before latanoprost reaches the cornea, it must pass through the tear film and tear film lipid layer (TFLL) on the ocular surface. Given the significant lipophilicity of latanoprost, we hypothesize that TFLL could, to a certain extent, act as a reservoir for latanoprost, releasing it on longer time scales, apart from the fraction being directly delivered to the cornea in a post-instillation mechanism. We investigated this possibility by studying latanoprost behavior in acellular in vitro TFLL models. Furthermore, we employed in silico molecular dynamics simulations to rationalize the experimental results and obtain molecular-level insight into the latanoprost-TFLL interactions. Our experiments demonstrated that latanoprost indeed accumulates in the TFLL models, and our simulations explain the basis of the accumulation mechanism. These results support the hypothesis that TFLL can serve as a reservoir for latanoprost, facilitating its prolonged release. This finding could have significant implications for optimizing glaucoma treatment, especially in the development of new drug delivery systems targeting the TFLL.