Optimization of a Rabbit Dry Eye Model Induced by Topical Instillation of Benzalkonium Chloride

Efficacy of Topical Cyclosporine Combined with Punctal Plugs in Treating Dry Eye Disease and Inflammation

PURPOSE

To evaluate the effect of punctal plugs combined with cyclosporine eye drops on dry eye disease (DED) and ocular surface inflammation.

METHODS

In a clinical trial, 73 patients were randomly allocated into three groups: punctal plug group, combination therapy group, and cyclosporine group. At the baseline and four weeks after treatment, the Schirmer I test score, fluorescein tear film break-up time (FBUT), ocular surface staining score and dry eye symptoms were assessed. Tear samples were collected to detect the level of inflammatory factors (interleukins, matrix metalloproteinase 9 (MMP-9) and tumor necrosis factor alpha (TNF-α)). In an animal experiment, a New Zealand rabbit dry eye model was induced. The rabbits were randomly divided into control group, punctal plug group, and combination therapy group (n = 6). Conjunctival goblet cell density, protein level of MMP-9 in conjunctiva and mRNA levels of inflammatory factors in conjunctiva and cornea were measured before and after treatment.

RESULTS

In combination therapy group of the clinical trial, the following results were observed: significant improvement in Schirmer I test scores and FBUT compared to the cyclosporine group and punctal plug group, respectively; a decrease in the tear levels of IL-6, IL-1, and MMP-9 compared to the punctal plug group; and a decrease in the tear levels of IL-1α, IL-6, and IL-17 compared to the baseline (all p < 0.05). In the animal experiment, rabbits in combination therapy group had a higher goblet cell density (p < 0.01) and lower mRNA levels of IL-16 (p < 0.05), IL-17 (p < 0.05), and MMP-9 (p < 0.01) in conjunctiva and that of MMP-9 (p < 0.01) in cornea compared to punctal plug group.

CONCLUSION

Cyclosporine eye drops combined with degradable punctal plugs is a more optimized clinical treatment strategy for DED compared with degradable punctal plugs or cyclosporine eye drops alone, considering the influence of comprehensive clinical efficacy and ocular surface inflammation.

Inflammation in Dry Eye Disease-Pathogenesis, Preclinical Animal Models, and Treatments

Dry eye disease (DED) is a rapidly growing ocular surface disease with a significant socioeconomic impact that affects the patients' visual function and, thus, their quality of life. It is distinguished by a loss of tear film homeostasis, leading to tear film instability, hyperosmolarity, ocular surface inflammation, and neurosensory abnormalities, with all of these playing etiological roles in the propagation of the vicious DED circle. While current treatments primarily focus on reducing tear film instability and hyperosmolarity, increasingly more attention is being placed on tackling the underlying inflammation that propagates and potentiates these factors. As such, preclinical models are crucial to further elucidate the DED pathophysiology and develop novel therapeutic strategies. This review outlines the role of inflammation in DED, highlighting related signs and diagnostic tools before focusing on relevant preclinical animal models and potential therapeutic strategies to tackle DED-associated inflammation.

Controlled release of vitamin A palmitate from crosslinked cyclodextrin organic framework for dry eye disease therapy

Controlled release drug delivery systems of eye drops are a promising ophthalmic therapy with advantages of good patient compliance and low irritation. However, the lack of a suitable drug carrier for ophthalmic use limits the development of the aforementioned system. Herein, the crosslinked cyclodextrin organic framework (COF) with a cubic porous structure and a uniform particle size was synthesized and applied to solidify vitamin A palmitate (VAP) by using the solvent-free method. The VAP@COF suspension eye drops were formulated by screening co-solvents, suspending agents, and stabilizing agents to achieve a homogeneous state and improve stability. According to the in vitro release study, the VAP@COF suspension exhibited a controlled release of VAP within 12 h. Both the ex vivo corneal contact angle and in vivo fluorescence tracking indicated that the VAP@COF suspension prolonged the VAP residence time on the ocular surface. This suspension accelerated the recovery of the dry eye disease (DED) model in New Zealand rabbits. Furthermore, the suspension was non-cytotoxic to human corneal epithelial cells and non-irritation to rabbit eyes. In summary, the particulate COF is an eye-acceptable novel carrier that sustains release and prolongs the VAP residence time on the ocular surface for DED treatment.

Characterizing the Robustness of Distinct Clinical Assessments in Identifying Dry Eye Condition of Animal Models

PURPOSE

The study aims to characterize the robustness of distinct clinical assessments in identifying the underlying conditions of dry eye disease (DED), with a specific emphasis on the involvement of conjunctival goblet cells.

METHODS

Seven rabbits receiving surgical removal of the lacrimal and Harderian glands were divided into two groups, one with ablation of conjunctival goblet cells by topical soaking of trichloroacetic acid (TCA) to the bulbar conjunctiva (n = 3) and one without (n = 4), and the conditions of DED were assessed weekly using Schirmer test, tear breakup time (TBUT), tear osmolarity, and National Eye Institute (NEI) fluorescein staining grading. After 8 weeks, the rabbits were sacrificed, and the eyes were enucleated for histopathological examination.

RESULTS

Histopathological analysis revealed corneal epithelial thinning in both groups. While TCA soaking significantly decreased the density of conjunctival goblet cells, DED rabbits without TCA also showed a partial reduction in goblet cell density, potentially attributable to dacryoadenectomy. Both groups showed significant decreases in Schirmer test and TBUT, as well as an increase in tear osmolarity. In DED rabbits with TCA soaking, tear osmolarity increased markedly, suggesting that tear osmolarity is highly sensitive to loss and/or dysfunction of conjunctival goblet cells. Fluorescein staining was gradually and similarly increased in both groups, suggesting that fluorescein staining may not reveal an early disruption of the tear film until the prolonged progression of DED.

CONCLUSION

The Schirmer test, TBUT, tear osmolarity, and NEI fluorescein grading are distinct, yet complementary, clinical assessments for the evaluation of DED. By performing these assessments in definitive DED rabbit models, both with and without ablation of conjunctival goblet cells, the role of these cells in the homeostasis of tear osmolarity is highlighted. Characterizing the robustness of these assessments in identifying the underlying conditions of DED will guide a more appropriate management for patients with DED.

Antioxidant Carbon Dots Nanozyme Loaded in Thermosensitive in situ Hydrogel System for Efficient Dry Eye Disease Treatment

Purpose

Dry eye disease (DED) is a multifactorial ocular surface disease with a rising incidence. Therefore, it is urgent to construct a reliable and efficient drug delivery system for DED treatment.

Methods

In this work, we loaded C-dots nanozyme into a thermosensitive in situ gel to create C-dots@Gel, presenting a promising composite ocular drug delivery system to manage DED.

Results

This composite ocular drug delivery system (C-dots@Gel) demonstrated the ability to enhance adherence to the corneal surface and extend the ocular surface retention time, thereby enhancing bioavailability. Furthermore, no discernible ocular surface irritation or systemic toxicity was observed. In the DED mouse model induced by benzalkonium chloride (BAC), it was verified that C-dots@Gel effectively mitigated DED by stabilizing the tear film, prolonging tear secretion, repairing corneal surface damage, and augmenting the population of conjunctival goblet cells.

Conclusion

Compared to conventional dosage forms (C-dots), the C-dots@Gel could prolong exhibited enhanced retention time on the ocular surface and increased bioavailability, resulting in a satisfactory therapeutic outcome for DED.

Sialylated IVIg promotes clinical improvements in a rabbit dry eye model by regulating inflammatory cytokines

Dry eye disease (DED) is caused by a loss of homeostasis of the tear film, which results in visual disturbance, ocular surface inflammation and damage, and neurosensory abnormalities. Although it is prevalent in 5-50% of the global population, there are limited clinical options for its treatment. This study explored the potential use of human intravenous immunoglobulin (IVIg) and its enriched fractions of sialylation, sialylated IVIg (sIVIg), as a treatment for DED. Fifteen female New Zealand white rabbits were topically instilled with 0.2% benzalkonium chloride (BAC) twice daily for five consecutive days to induce experimental dry eye. Saline, 0.4% IVIg, or 0.04% sIVIg eye drops were instilled twice daily for 20 consecutive days. Clinical evaluations, such as non-invasive tear break-up time (NIBUT) and corneal fluorescein staining (CFS), were conducted. mRNA levels of mucin 4, mucin 16, TNF-α, IL-1β, MMP9, IL-10, TGF-β, and CD209 in rabbit conjunctival tissues were examined using reverse transcription polymerase chain reaction (RT-PCR) or quantitative RT-PCR (qRT-PCR). The relationships between CD209 family members in rabbits and various mammalian species were analyzed using a phylogenetic tree. IVIg or sIVIg treatment resulted in clinical improvements in the rabbit DED model. The inflammatory cytokines, TNF-α and IL-1β, were increased and mucin 4 and mucin 16, cell surface-associated mucins, were decreased in BAC-induced dry eye. Following IVIg or sIVIg treatment, inflammatory cytokines decreased, whereas the anti-inflammatory cytokine, IL-10, increased substantially. Moreover, a 10-fold lower sIVIg treatment dose resulted in prolonged IL-10 production, representing a significantly improved DED compared to IVIg. Furthermore, the expression of rabbit CD209 mRNA in the rabbit conjunctiva and its close relationship with primate homologs suggest that it may interact with IVIg or sIVIg to promote IL-10 expression, as previously described in humans. At a lower dosage, sIVIg showed a more efficient improvement in DED, making it a promising new candidate medication for DED.

DZ2002 alleviates corneal angiogenesis and inflammation in rodent models of dry eye disease via regulating STAT3-PI3K-Akt-NF-κB pathway

Dry eye disease (DED) is a prevalent ocular disorder with a multifactorial etiology. The pre-angiogenic and pre-inflammatory milieu of the ocular surface plays a critical role in its pathogenesis. DZ2002 is a reversible type III S-adenosyl-L-homocysteine hydrolase (SAHH) inhibitor, which has shown excellent anti-inflammatory and immunosuppressive activities in vivo and in vitro. In this study, we evaluated the therapeutic potential of DZ2002 in rodent models of DED. SCOP-induced dry eye models were established in female rats and mice, while BAC-induced dry eye model was established in female rats. DZ2002 was administered as eye drops (0.25%, 1%) four times daily (20 μL per eye) for 7 or 14 consecutive days. We showed that topical application of DZ2002 concentration-dependently reduced corneal neovascularization and corneal opacity, as well as alleviated conjunctival irritation in both DED models. Furthermore, we observed that DZ2002 treatment decreased the expression of genes associated with angiogenesis and the levels of inflammation in the cornea and conjunctiva. Moreover, DZ2002 treatment in the BAC-induced DED model abolished the activation of the STAT3-PI3K-Akt-NF-κB pathways in corneal tissues. We also found that DZ2002 significantly inhibited the proliferation, migration, and tube formation of human umbilical endothelial cells (HUVECs) while downregulating the activation of the STAT3-PI3K-Akt-NF-κB pathway. These results suggest that DZ2002 exerts a therapeutic effect on corneal angiogenesis in DED, potentially by preventing the upregulation of the STAT3-PI3K-Akt-NF-κB pathways. Collectively, DZ2002 is a promising candidate for ophthalmic therapy, particularly in treating DED.

Early-Stage Development of an Anti-Evaporative Liposomal Formulation for the Potential Treatment of Dry Eyes

Dry eye disease (DED), the most common ocular disorder, reduces the quality of life for hundreds of millions of people annually. In healthy eyes, the tear film lipid layer (TFLL) stabilizes the tear film and moderates the evaporation rate of tear fluid. In >80% of DED cases, these central features are compromised leading to tear film instability and excessive evaporation of tear fluid. Herein we assess the potential of liposomal formulations featuring phosphatidylcholines and tailored lipid species from the wax ester and O-acyl-ω-hydroxy fatty acid categories in targeting this defect. The developed lead formulation displays good evaporation-resistant properties and respreadability over compression-expansion cycles in our Langmuir model system and a promising safety and efficacy profile in vitro. Preclinical in vivo studies will in the future be required to further assess and validate the potential of this concept in the treatment of DED.

Neurosensory abnormalities and stability of a mouse model of dry eye disease

This study aimed to use a mouse model of dry eye disease (DED) induced by topical administration of benzalkonium chloride (BAK) and assess its stability and the presence of neurosensory abnormalities, including ocular pain. Eight-week-old C57BL6/6 N male mice were used in this study. Mice were treated with 10 μL of 0.2% BAK dissolved in artificial tears (AT), administered twice daily for 7 days. After one week, animals were randomized into two groups: one was administered with 0.2% BAK in AT once per day for 7 days, while the other was not further treated. Corneal epitheliopathy was quantified at days 0, 3, 7, 12, and 14. Moreover, tear secretions, corneal nociception, and corneal nerve integrity were measured after BAK treatment. After sacrifice, corneas were dissected to assess nerve density and leukocyte infiltration by immunofluorescence. Topical BAK instillation for 14 days significantly increased corneal fluorescein staining (p < 0.0001) compared to day 0. On the other hand, interruption of BAK instillation was associated with improvement of corneal epitheliopathy (day 12, p < 0.0001; day 14, p < 0.001). BAK treatment increased ocular pain (p < 0.0001) and resulted in a significant increase in leukocyte infiltration in the cornea (p < 0.01). Moreover, corneal sensitivity was reduced (p < 0.0001), together with corneal nerve density (p < 0.0001) and tear secretion (p < 0.0001). One week twice a day, followed by one additional week once a day, of 0.2% BAK topical administration induces stable clinical and histological signs of DED, which is associated with neurosensory abnormalities, including pain.

Dietary Alcohol Consumption Elicits Corneal Toxicity Through the Generation of Cellular Oxidative Stress

Purpose: Clinical data suggest that alcohol use is associated with the development of signs and symptoms of dry eye disease. However, preclinical data investigating ocular toxicity after dietary alcohol consumption are lacking. In this study, we investigated the effects of alcohol on the ocular surface, in human corneal epithelial cells (HCE-T) in vitro and in C57BL/6JRj mice in vivo. Methods: HCE-T were exposed to clinically relevant doses of ethanol. To determine the effects of dietary alcohol consumption in vivo, wild-type mice were administered the Lieber-DeCarli liquid diet (5% vol/vol ethanol or isocaloric control) for 10 days ad libitum. Corneal fluorescein staining was performed to assess ocular surface damage. Histopathological and gene expression studies were performed on cornea and lacrimal gland tissue. Results: Sublethal doses of ethanol (0.01%-0.5%) resulted in a dose-dependent increase of cellular oxidative stress in corneal epithelial cells and a significant increase in NFE2L2 and downstream antioxidant gene expression, as well as an increase in NFκB signaling; short-term exposure (0.5%, 4 h) triggered significant corneal epithelial cell barrier breakdown. Exposure to the alcohol-containing diet caused a 3-fold increase in corneal fluorescein staining, with no effect on tear volumes. Corneal thickness was significantly reduced in the alcohol diet group, and corneal tissue revealed dysregulated antioxidant and NFκB signaling. Our data provide the first published evidence that alcohol exposure causes ocular toxicity in mice. Conclusions: Our results are consistent with clinical studies linking past alcohol consumption to signs of ocular surface disease.

Rodent models for dry eye syndrome: Standardization using benzalkonium chloride and scopolamine hydrobromide

Dry eye disease is a highly prevalent ocular condition that significantly affects the quality of life and presents a major challenge in ophthalmology. Animal models play a crucial role in investigating the pathophysiology and developing effective treatments. The goal of this study was to compare and standardize two dry eye disease rodent models and explore their recovery aspects. We have standardized benzalkonium chloride and scopolamine-induced dry eye disease models which represents two different classes of the dry eye i.e., evaporative dry eye and aqueous deficient dry eye, respectively. After the development of dry eye conditions, a self-recovery period of seven days was granted to assess the reversal of the induced changes. The dry eye condition was assessed by measuring tear volume, corneal slit lamp imaging, and histological examination of the cornea, the lacrimal and the harderian gland. The study indicated the development of chronic inflammation of the cornea and lacrimal gland in the case of benzalkonium after five days of the treatment, while the scopolamine treated group showed chronic inflammation of the lacrimal gland after five days and corneal inflammation after seven days of administration. The recovery study suggested that after discontinuation of inducing agent, the dry eye symptoms were still persistent suggesting the utility of the model in evaluating dry eye treatments. The study highlights the comparative changes in both models along with recovery which can serve as a base for drug discovery and development against dry eye disease.

Benzalkonium Chloride for Experimental Dry Eye Induction in a Rabbit Model

Purpose: This study compared the clinical parameters and histological findings according to the benzalkonium chloride concentration (BAC; 0.05%, 0.1%, and 0.2%) for inducing experimental dry eye (EDE) in a rabbit model.Methods: Rabbits were divided into four groups according to the BAC concentration: untreated group, 0.05%, 0.1%, and 0.2% BAC. BAC was instilled topically in both eyes of the rabbits twice daily until they were euthanized after 14 days. Tear volume, tear break-up time (TBUT), and corneal fluorescein staining score (CFS) were measured 0, 3, 5, 7, and 14 days after treatment. After excising tissues on day 14, the conjunctival goblet cell density and corneal epithelial apoptosis were quantified.Results: The tear volume and TBUT were lower and the CFS was higher than baseline values after 14, 10, and 5 days in the 0.05, 0.1, and 0.2% BAC groups, respectively (all p < 0.05). At 14 days, the 0.2% BAC group showed more significant aggravation of all clinical parameters, and the 0.1% BAC group had a lower CFS (all p < 0.05) than the 0.05% BAC group. In all BAC groups, the conjunctival goblet cell density was lower and corneal epithelial apoptosis was significantly higher than in the untreated group (all p < 0.01). The conjunctival goblet cell density was lower in the 0.2% BAC group than in the 0.05% BAC group. Between-group differences in corneal epithelial apoptosis were observed in all experimental groups (all p < 0.01).Conclusions: Instilling BAC for 14 days induced EDE in the 0.05, 0.1, and 0.2% BAC groups. Although 0.2% BAC cannot be used for a severe EDE model, it is useful for inducing EDE in a rabbit model in a short time.

Efficacy of Artificial Tears Based on an Extract of Artemia salina Containing Dinucleotides in a Rabbit Dry Eye Model

(1) Background: Artemia salina is a brine shrimp containing high concentrations of dinucleotides, molecules with properties for dry eye treatment. For this reason, the purpose of the study was to evaluate the effect of the artificial tears based on an extract of Artemia salina in a rabbit dry eye model. (2) Methods: A prospective and randomized study was carried out. Twenty rabbits were divided into 4 groups (n = 5, each group): healthy rabbits, dry eye rabbits, dry eye rabbits treated with hypromellose (HPMC), and dry eye rabbits treated with Artemia salina. Dry eye was induced by the topical instillation of 0.2% benzalkonium chloride. The measurements were performed before and after the treatment for 5 consecutive days. (3) Results: The topical instillation of artificial tears containing Artemia salina showed beneficial effects on tear secretion, tear break-up time, corneal staining, the density of Goblet cells, heigh of mucin cloud secreted by these cells, and mRNA levels of IL-1β and MMP9 in conjunctival cells. Compared with the HPMC, there was a statistically significant improvement (p < 0.05) with the Artemia salina in all the variables under study, except for the conjunctival hyperemia, density of Goblet cells, and mRNA levels of IL-6. (4) Conclusions: The potential of artificial tears based on Artemia salina as a secretagogue agent for dry eye treatment was confirmed, opening the door for future clinical trials and studies to extrapolate the findings for dry eye patients.

Rabbit models of dry eye disease: Current understanding and unmet needs for translational research

Dry eye disease (DED) is emerging as an eye health pandemic, affecting millions worldwide. The development of novel drugs, drug delivery systems, and targeted therapies for addressing the inflammation in DED necessitates progress in experimental models of DED. Animal models of DED have been created for simulating the two clinically described forms of DED: lacrimal insufficiency and the evaporative DED models. Although most DED models have relied upon rodents, the larger eye size and longer life span of rabbits and the closer resemblance to human lacrimal glands, render rabbits a promising near-ideal model for studying DED. Since the first rabbit DED model was described, numerous modifications including the use of topical epitheliotoxic drugs, neural abolition, activated lymphocytes injection, and surgical dacryoadenectomy have been introduced. The stability of these models, whether short-term or long-term, accordingly guides their experimental or therapeutic utility. A rabbit autoimmune dacryoadenitis model has successfully simulated DED signs and features of lacrimal gland inflammation, as observed in Sjogren's syndrome, that improved with mesenchymal stem cell therapy. This review summarizes the comparative microscopic anatomy of rabbit and human lacrimal glands, various existing rabbit DED models and their respective suitability for understanding pathogenetic mechanism of DED or for experimental drug testing. Also, the insights gained from animal models in dry eye management is described along with the future perspectives. There is still a pressing need of developing rabbit models for studying the pathogenesis of complex ocular surface changes in evaporative and aqueous deficiency DED other than autoimmune dacryoadenitis.