Corneal Abnormalities in the NC/Nga Mouse

Animal Models for the Study of Keratoconus

Keratoconus (KC) is characterized by localized, central thinning and cone-like protrusion of the cornea. Its precise etiology remains undetermined, although both genetic and environmental factors are known to contribute to disease susceptibility. Due to KC's complex nature, there is currently no ideal animal model to represent both the corneal phenotype and underlying pathophysiology. Attempts to establish a KC model have involved mice, rats, and rabbits, with some additional novel animals suggested. Genetic animal models have only been attempted in mice. Similarly, spontaneously occurring animal models for KC have only been discovered in mice. Models generated using chemical or environmental treatments have been attempted in mice, rats, and rabbits. Among several methods used to induce KC in animals, ultraviolet radiation exposure and treatment with collagenase are some of the most prevalent. There is a clear need for an experimental model animal to elucidate the underlying mechanisms behind the development and progression of keratoconus. An appropriate animal model could also aid in the development of treatments to slow or arrest the disorder.

Incorrect sleeping position and eye rubbing in patients with unilateral or highly asymmetric keratoconus: a case-control study

PURPOSE

To evaluate eye rubbing and sleeping position in patients with Unilateral or Highly Asymmetric Keratoconus (UHAKC).

METHODS

Case-control study of consecutive UHAKC patients diagnosed at the Rothschild Foundation. Controls were age- and sex-matched, randomly selected refractive surgery clinic patients. Patients self-administered questionnaires regarding their family history of keratoconus, eye rubbing, and sleeping habits. All the eyes underwent a comprehensive ocular examination. Logistic regression was used to analyze univariate and multivariate data to identify risk factors for keratoconus.

RESULTS

Thirty-three UHAKC patients and 64 controls were included. Univariate analyses showed that daytime eye rubbing [OR = 172.78], in the morning [OR = 24.3], or in eyes with the steepest keratometry [OR = 21.7] were significantly different between groups. Allergy [OR = 2.94], red eyes in the morning [OR = 6.36], and sleeping on stomach/sides [OR = 14.31] or on the same side as the steepest keratometry [OR = 94.72] were also significantly different. The multivariate model also showed statistical significance for most factors including daytime eye rubbing [OR = 134.96], in the morning [OR = 24.86], in the steepest eye [OR = 27.56], and sleeping on stomach/sides [OR = 65.02] or on the steepest side [OR = 144.02]. A univariate analysis in UHAKC group, comparing the worse and better eye, showed that eye rubbing [OR = 162.14] and sleeping position [OR = 99.74] were significantly (p < 0.001) associated with the worse eye.

CONCLUSION

Our data suggests that vigorous eye rubbing and incorrect sleeping position are associated with UHAKC. This is especially true in rubbing the most afflicted eye, and contributory sleep position, including positions placing pressure on the eye with the steepest keratometry.

Very Low Prevalence of Keratoconus in a Large Series of Vernal Keratoconjunctivitis Patients

PURPOSE

To evaluate the prevalence of keratoconus (KC) and other corneal abnormalities by means of videokeratography and tomography in a large series of patients affected by vernal keratoconjunctivitis (VKC).

DESIGN

Cross-sectional study.

METHODS

Setting: Single-center children's hospital.

STUDY POPULATION

A total of 651 consecutive patients with VKC and a control group of 500 were prospectively recruited between May 1, 2012 and September 30, 2013, with a minimum follow-up of 12 months.

OBSERVATION PROCEDURE

All patients were evaluated by means of a Scheimpflug camera combined with a Placido corneal topographer. Keratoconus, suspected keratoconus, or its absence were determined in each patient. The corneal symmetry index of front (SI_f) and back curvature (SI_b), shape indices, and thicknesses were compared between the 2 groups.

MAIN OUTCOME MEASURES

Prevalence of keratoconus and corneal indices modifications.

RESULTS

Five out of 651 patients (0.77%) demonstrated topographic signs of KC. Two of them were bilateral. All patients were older than 7 years of age, and the mean age was 11.54 years. Four other patients (0.61%) were classified as KC suspects by the screening program. Of 304 patients older than 11 years (mean age 14.4 years), 4 (1.32%) were found to have KCN, and 4 (1.32%) were KC suspects. The corneal indices of patients in the VKC group were extremely similar to those in the control group. (P > .05).

CONCLUSIONS

The prevalence of KC in our patient population, compared with previous reports in the literature, is much lower. The similar corneal indices in both groups suggest the absence of permanent corneal deformation due to VKC.

STAT6-mediated keratitis and blepharitis: a novel murine model of ocular atopic dermatitis

PURPOSE

Atopic dermatitis (AD) is a common inflammatory disease that can affect the eye, resulting in ocular pathologies, including blepharitis, keratitis, and uveitis; however, the pathogenic mechanisms underlying the ocular manifestations of AD are not well understood.

METHODS

In the present study, we characterized the ocular pathologies that develop in the Stat6VT mouse model of AD. We examined the cytokine profile of the eyelid lesions, measured the behavioral response, and documented the treatment response to topical steroids.

RESULTS

Our results show that Stat6VT mice spontaneously developed blepharitis, keratitis, and uveitis similar to that observed in patients with AD. Histologic findings of allergic inflammation in affected eyelids in this model include the presence of a lymphocyte-predominant infiltrate and tissue eosinophilia in the dermis. Gene expression analysis of affected eyelid tissue by quantitative PCR revealed increased amounts of mRNAs for the Th2 cytokines IL-4, IL-5, and IL-13. In addition, increased eyelid scratching was seen in Stat6VT mice with blepharitis. Topical treatment with the corticosteroid clobetasol reduced eyelid inflammation, tissue eosinophilia, and Th2 cytokine expression.

CONCLUSIONS

The development of AD-like ocular pathologies in this model supports the idea that in humans, AD-associated disease of the eye may be driven by Th2-mediated inflammation and demonstrates that the Stat6VT mouse may be a useful system in which to further investigate pathogenesis of and treatment strategies for blepharitis and other ocular diseases that develop in association with AD.

Evaluation of eosinophilic inflammation in a novel murine atopic keratoconjunctivitis model induced by crude Dermatophagoides farinae antigen

BACKGROUND

The purpose of this study is to conduct a histopathological research of the conjunctival findings and eosinophilic inflammation of novel atopic keratoconjunctivitis in a NC/Nga mouse model using crude Dermatophagoides farina.

METHODS

NC/Nga mice were sensitized by repeated topical applications of an ointment containing Dermatophagoides farinae body (Dfb). They were then divided into 4 groups depending on the following topical ophthalmic treatment: DFb group undergoing topical ophthalmic ointment containing Dfb; DFco group undergoing topical instillation of allergen extracts of Dermatophagoides farinae; Ba group undergoing topical ointment with substrate alone and NT group without after-topical ophthalmic treatment. At 24 hours after the last ophthalmic treatment, histopathological examination was performed. The density of the subepithelial infiltration of the eosinophils was determined. Serum total IgE and house-dust-mite (HDM)-specific IgE antibody concentrations were determined by enzyme-linked immunosorbent assay (ELISA).

RESULTS

In the DFb group, the conjunctiva showed similar findings to those of atopic keratoconjunctivitis, i.e. intraepithelial pseudotubular formation, Torus-form infiltration due to massive lymphocytes in the palpebral conjunctiva and gelatinous hyperplasia in the limbus with subepithelial granuloma composed of lymphocytes and eosinophils. Subepithelial infiltration of eosinophil density in the DFb group [878.4 ± 399.7cells/mm2 (mean ± SD)] was significantly higher than in the other 2 groups (DFco 85.6 ± 40.1 Ba 49.2 ± 32.3) (P < 0.001). Total serum IgE concentration and HDM-specific serum IgE antibody concentration in the DFb group and the DFco group were significantly higher compared with those in the NT group.

CONCLUSIONS

Topical application of an ointment containing DFb to both the skin and eyes of NC/Nga mice can induce an atopic keratoconjunctivitis (AKC) model in these mice.

Retinal degeneration and rd1 mutation in NC/Tnd mice-a human atopic dermatitis model

PURPOSE

NC/Tnd mice, a spontaneous model for human atopic dermatitis, are also useful animal models for various corneal disorders accompanying allergic diseases. The purposes of the current study were to investigate the development of retinal degeneration in NC/Tnd mice.

MATERIALS AND METHODS

Histological examination was performed to determine time-dependent alterations of the retina in NC/Tnd from 8 to 28 days of age. Apoptotic cells were determined by TUNEL assay. Retinal function was examined by electroretinography. Fundoscopy was performed in NC/Tnd mice at 8 weeks of age. Melanin contents in whole-eye extracts were measured by spectrophotometry. Since the retinal degeneration 1 (rd1) mutation in the rod photoreceptor cyclic guanosine monophosphate phosphodiesterase 6 β-subunit (Pde6b(rd1)) has been identified in laboratory mice, the possible existence of the rd1 mutation was analyzed with PCR genotyping and gene sequencing. C57BL/6, WB, and C3H/HeN mice were used as controls.

RESULTS

Histological examination revealed rapid postnatal retinal degeneration in NC/Tnd mice. The number of apoptotic cells in the outer nuclear layer (ONL) increased with aging, and finally the ONL disappeared. Histological abnormality was not obvious in the inner nuclear layer or the ganglion cell layer. Electroretinography shows no response in adult NC/Tnd mice. Fundoscopic observation revealed hypopigmentation in the retina, and melanin contents in the eye were significantly reduced when compared with other inbred strains. Insertion in the rd1 allele was confirmed and a nonsense mutation of Pde6b(rd1) gene was determined in NC/Tnd mice.

CONCLUSIONS

NC/Tnd mice also preserve the Pde6b(rd1) gene mutation resulting in the rapid postnatal retinal degeneration similar to that in C3H/HeN mice. Unlike C3H/HeN mice, since melanin contents of the retina in NC/Tnd mice was decreased, unknown defects may be present in the process of melanin composition in retinal pigment epithelial cells during fetal development of NC/Tnd mice.