Understanding corneal endotheliitis: an animal model approach

Establishing an Animal Model of Cytomegalovirus Keratouveitis in Rats: Broad Infection of Anterior Segment Tissue by Cytomegalovirus

Purpose

Considering the difficulty of obtaining adequate biological tissue in clinical practice, we established an animal model of cytomegalovirus (CMV) keratouveitis in rats and investigated the viral infection sites and corresponding imaging and histopathological features.

Methods

Subconjunctival injection and topical use of dexamethasone were used to induce ocular immunosuppression in rats followed by intracameral inoculation of murine cytomegalovirus (MCMV). The clinical manifestations, intraocular pressure (IOP) and imaging changes were observed. Infected eyes were further examined by immunofluorescence, light microscopy, and electron microscopy. MCMV RNA was detected by reverse transcription-polymerase chain reaction.

Results

Typical keratouveitis occurred in the experimental rats and was characterized by corneal edema, keratic precipitates, and iridocyclitis with increased IOP. Corneal endothelial lesions displayed as “black holes,” enlarged intercellular gaps, and high-intensity cellular infiltration by confocal microscopy, consistent with the pathological changes of “ballooning degeneration,” endothelial cell detachment, and inflammatory cell infiltration. Mitochondrial edema was the most prominent organelle lesion in endothelial cells. Trabeculitis, mechanical obstruction of Schlemm's canal, and anterior chamber angle stenosis accounted for elevated IOP. Inflammation of the iris and ciliary body tended to transform into a chronic form. Immunofluorescence revealed that corneal endothelial cells, iris cells, trabecular meshwork cells, and monocytes could be infected by MCMV. MCMV RNA was found in the anterior segments after infection.

Conclusions

CMV can widely infect anterior segment tissue, including the corneal endothelium, iris, and trabecular meshwork, in vivo, inducing the corresponding clinical manifestations. Corneal endotheliitis and hypertensive anterior uveitis could be the specific stage of anterior segment infection of CMV.

In Vivo Confocal Microscopy Use in Endotheliitis

PURPOSE

The use of in vivo confocal microscopy has been valuable in detecting and managing corneal pathology. This case study documents endotheliitis using in vivo confocal microscopy where apparent resolution of endothelial edema on clinical examination resulted in the discovery of subclinical findings with confocal scanning. The purpose of this case study was to discuss a rare corneal pathology and the clinical value of confocal scanning.

CASE REPORT

A 30-year-old Asian Indian woman presented with unilateral endotheliitis and trabeculitis of presumed varicella zoster virus etiology. She was treated successfully with oral antiviral and topical corticosteroid therapy. Subclinical endotheliitis was detected using in vivo confocal microscopy, prompting the continuation of prophylactic, low-dose, topical corticosteroid therapy and topical hyperosmotics.

CONCLUSIONS

Further research is warranted to better understand the role of confocal microscopy in endotheliitis therapeutic management, endothelial cell count and morphology, and keratic precipitate characterization. To date, prophylactic oral antivirals and/or topical corticosteroids may play a role in immune suppression of the herpes virus, although prospective, randomized, controlled clinical trials have not focused specifically on endotheliitis cases.

Review of clinical and basic approaches to corneal endotheliitis

Corneal endotheliitis was first reported as an autoimmune disease by Khodadoust in 1982. Thereafter, herpes simplex virus (HSV) was detected as a causative agent, and corneal endotheliitis was classified as an infectious disease. However, most primary corneal endotheliitis had been idiopathic. In 2006, cytomegalovirus (CMV) DNA was detected in a case of corneal endotheliitis, and other reports on CMV endotheliitis from Asian countries established it as a new clinical entity. Limited studies have reported clinical findings, and the pathogenesis of HSV and CMV corneal endotheliitis is unknown. Therefore, this review describes what is currently known about the pathogenesis of HSV and CMV endotheliitis by way of previously reported case studies and basic research. In addition, we review work by our own group regarding the role of Toll-like receptor 9 and the results of transcriptome analysis after HSV infection in an in vitro model using immortalized human corneal endothelial cells. It is critical to diagnose corneal endotheliitis early to provide effective treatment with ganciclovir or valganciclovir and prevent the loss of corneal endothelial cells. Therefore, we hope that these in vitro results may provide further information to help elucidate the in vivo pathogenesis of HSV and CMV endotheliitis.

Expression of CXCL9, -10, and -11 in the aqueous humor of patients with herpetic endotheliitis

PURPOSE

To evaluate the expression of CXCL9, -10, and -11 chemokines in the aqueous humor of patients with herpetic endotheliitis.

METHODS

Aqueous humor was collected from 26 patients with herpetic endotheliitis and 21 control subjects. The concentrations of CXCL9, -10, and -11 in the aqueous humor were measured with enzyme-linked immunosorbent assays. The correlation between chemokine levels and clinical parameters of disease severity was analyzed. Flow cytometry was performed to count CXCR3 cells and CXCR3CD4 cells in the aqueous humor.

RESULTS

The concentrations of CXCL9, -10, and -11 were 429.08 ± 297.41 pg/mL, 23,102.49 ± 15,964.95 pg/mL, and 258.25 ± 103.25 pg/mL in patients with herpetic endotheliitis and 16.84 ± 16.73 pg/mL (P < 0.01), 188.45 ± 183.43 pg/mL (P < 0.01), and 7.32 ± 6.45 pg/mL (P < 0.01) in control subjects, respectively. Aqueous chemokine levels correlated significantly with keratitic precipitates and corneal edema in patients with herpetic endotheliitis. The mean percentages of CXCR3 and CXCR3CD4 cells were higher in herpetic endotheliitis patients compared with the controls.

CONCLUSIONS

Expression of CXCL9, -10, and -11 chemokines and their receptor CXCR3 increases in the aqueous humor of patients with herpetic endotheliitis. Chemokine levels are associated with the clinical severity of the disease.

Eye

The Eye chapter of the 3rd edition of Haschek and Rousseaux’s Handbook of Toxicologic Pathology brings a comprehensive description of pathological processes affecting the ocular tissues in the most commonly used laboratory animals and their correlations with human diseases of interest in toxicology. Also presented are detailed descriptions of the structure and function of the different ocular tissues, the most advanced techniques applied in the toxicological evaluation of the eye, useful animal models of human disease, and known mechanisms of ocular toxicity. The introductory sections of the chapter also feature such essential topics as ocular embryology, an overview of clinical ophthalmic evaluation, and eye-specific techniques of tissue processing.