The beneficial effects of doxycycline, an inhibitor of matrix metalloproteinases, on sulfur mustard-induced ocular pathologies depend on the injury stage.

PURPOSE: Sulfur mustard (SM) induces acute ocular lesions, including erosions and inflammation that may be followed by delayed injuries expressed by epithelial defects and neovascularization (NV). Based on the matrix metalloproteinases (MMPs) activity, we evaluated the clinical and biochemical effects of topical treatment with doxycycline, an MMP inhibitor, targeted to the various injury stages. METHODS: Rabbit eyes were exposed to SM vapor. A clinical follow-up was carried out up to 2 months. Tear fluid and cornea samples were collected at different time points for measurements of MMPs activity by zymography. Efficacy of a post-exposure topical doxycycline (2 mg/ml in phosphate buffer saline, ×4/d), targeted to the different phases of the clinical injury, was evaluated. RESULTS: Elevated MMP-9 and MMP-2 activities were found in all corneas during the acute injury and in vascularized corneas during the delayed pathology. In the tear fluid, high MMP-9 activity and negligible MMP-2 activity were found in all the exposed eyes until after the appearance of the delayed pathology symptoms. Prolonged doxycycline treatment reduced MMP-9 activity in the tear fluid. During the acute phase, doxycycline treatment reduced corneal MMP-9 activity and the severity of the injury. Targeting the delayed pathology, doxycycline was clinically efficient only when treatment began before NV appearance. CONCLUSIONS: This in vivo study showed the involvement of MMP-9 and MMP-2 during different phases of the SM-induced ocular injury, and the potential of doxycycline treatment as a post exposure measure for reducing the acute injury and as a preventive therapy for ameliorating the delayed pathology. The tear fluid provided a non-invasive method for continuous follow-up of MMPs activity and revealed additional beneficial aspects of injury and the treatment.

Cultivation and characterization of limbal epithelial stem cells on contact lenses with a feeder layer: toward the treatment of limbal stem cell deficiency.

PURPOSE: Limbal epithelial sheets are used to promote corneal surface reconstruction after the detection of limbal epithelial stem cell deficiency. The aim of this study was to evaluate a novel combination of limbal stem cells (LSCs) maintained on contact lenses (CLs) in the presence of a 3T3 feeder cell layer regarding preservation of stem cell phenotype and the potential use for future in vivo transplantation. METHODS: Limbal epithelial cells were isolated from rabbit cornea and cultured with 3T3 cells on CLs. The preservation of LSC phenotype was determined using p63α and ABCG2 immunostaining, whereas epithelial differentiation was evaluated using CK3 and CK19. The colony-forming assay was used to determine the percentage of LSCs in cultures. Finally, CLs seeded with PKH26-labeled LSCs were transferred to rabbit eyes after performing a surgical keratectomy, and the transition and phenotype of labeled cells on the corneal surface were evaluated in whole-mount corneas. RESULTS: Proliferation of individual limbal cells was observed on CLs with a 3T3 feeder cell layer, showing holoclone formation and retention of viable stem or progenitor cell phenotype. Finally, a higher transition of cultivated cells after a dual sequential CL transplantation to the ocular surface was observed, showing the preservation of the LSC phenotype in the corneal surface. CONCLUSIONS: Limbal cells cultivated on a CL carrier overlaying a 3T3 feeder layer are mitotically active and retain the LSC phenotype. This novel technique of using CLs as a carrier offers an easily manipulable and nonimmunogenic method for transferring LSCs for ocular surface reconstruction in patients with limbal epithelial stem cell deficiency.

Efficacy assessment of various anticholinergic agents against topical sarin-induced miosis and visual impairment in rats.

Eye exposure to the organophosphorus (OP) irreversible acetylcholinesterase inhibitor sarin results in long-term miosis and reduction in visual function. Anticholinergic drugs, such as atropine or homatropine, which are used topically in order to counter these effects may produce mydriasis and partial cycloplegia, which may worsen visual performance. This study was aimed to test the efficacy of short-acting anticholinergic drugs against sarin-induced miosis and visual impairment, which will minimally insult vision. Long-Evans rats, exposed topically to various sarin doses from 0 to 10 µg, showed a dose-dependent miosis, which returned to pre-exposure levels within 24-48 h. Tropicamide treatment rapidly widened the miotic effect to a different extent depending on time following treatment and dosage given. Cyclopentolate, however, showed a delayed response that finally widened the pupils in a dose-dependent manner. Atropine treatment showed a rapid widening of the pinpoint pupils exceeding baseline level finally causing mydriasis. Light reflex test showed that the contraction ability of the iris following atropine treatment was impaired, as opposed to the use of tropicamide which facilitated the iris contraction, similar to control. Finally, tropicamide and atropine treatments ameliorated the visual impairment, as opposed to cyclopentolate, which worsened visual performance. Considering that tropicamide treatment against sarin exposure did not cause mydriasis nor did it impair the iris contraction flexibility as a response to light, the use of this drug should be taken into consideration as a first-choice topical treatment against OP intoxication.

Ocular injuries following sulfur mustard exposure--pathological mechanism and potential therapy.

Sulfur mustard (SM) is a potent vesicant, known for its ability to cause incapacitation and prolonged injuries to the eyes, skin and respiratory system. The toxic ocular events following sulfur mustard exposure are characterized by several stages: photophobia starting a few hours after exposure, an acute injury phase characterized by inflammation of the anterior segment and corneal erosions and a delayed phase appearing following a clinically silent period (years in human). The late injury appeared in part of the exposed eyes, expressed by epithelial defects and corneal neovascularization (NV), that lead to vision deficits and even blindness. During the last years we have characterized the temporal development of ocular lesions following SM vapor exposure in rabbits and have shown the existence of two sub-populations of corneas, those exhibiting delayed ocular lesions (clinically impaired) and those exhibiting only minor injuries if at all (clinically non-impaired). The aim of the present study was to investigate the pathological mechanism underlying the delayed injury by focusing on the unique characteristics of each sub-population and to test the efficacy of potential treatments. Clinically impaired corneas were characterized by chronic inflammation, increased matrix metalloproteinase (MMP) activity, poor innervation and limbal damage. Moreover, using impression cytology and histology, we identified the delayed lesions as typical for an ocular surface disorder under the category of limbal epithelial stem cell deficiency (LSCD). These results point to therapeutic directions, using anti-inflammatory drugs, MMPs inhibitors, neurotrophic factors and amniotic membrane transplantation. Topical anti-inflammatory drugs, either steroid (Dexamycin, DEX) or non-steroidal anti-infllammatory drug (NSAID, Voltaren Ophtha) were found to be beneficial in ameliorating the initial inflammatory response and in postponing the development of corneal NV, when given during the first week after exposure. When DEX was administered as a symptomatic treatment against NV, a significant regression in the angiogenic process was observed, however, the effect was temporal and blood vessels reappeared after therapy ceased. Chronic administration (8 weeks) of the MMP inhibitor Doxycycline was also effective in attenuation of the acute and delayed injury. Preliminary results, using amniotic membrane transplantation revealed some decrease of corneal edema with no effect on corneal NV. It is suggested that the chronic inflammation and prolonged impairment of corneal innervation are playing a role in the pathogenesis of the delayed LSCD following SM exposure by creating a pathological microenvironment to limbal epithelial stem cells, thus, leading to their slow death and to a second cascade of pathological events eventually resulting in severe long-term injuries. As of today, only topical anti-inflammatory drugs reached the criteria of an applicable efficient post-exposure ocular treatment for SM injuries. Further studies are required to investigate the effects of SM on epithelial stem cells and their involvement in the pathogenesis of the long-term injuries.

Optic neuritis associated with etanercept therapy for juvenile arthritis.

PURPOSE: We sought to describe cases of optic neuritis associated with etanercept therapy. METHODS: A retrospective chart review was undertaken on all patients that developed uveitis or optic neuritis associated with etanercept therapy between January 2003 and January 2005 in 2 medical centers: Assaf Harofeh Medical Center, and Kaplan Medical Center, Israel. RESULTS: Four patients (3 girls, 1 boy) treated with etanercept for juvenile idiopathic arthritis (JIA) are presented. The 3 girls had oligoarticular-onset JRA. The boy had HLA-B27-positive juvenile spondyloarthropathy and bilateral uveitis. After a mean follow-up of 10 months (range, 2.5-18 months) all 4 patients had reduced visual acuity due to optic neuritis, which was accompanied by vitreitis in 2 eyes. In 3 patients, the discontinuation of etanercept, together with steroid treatment, resulted in resolution of the inflammation. The fourth patient elected to continue etanercept treatment and experienced no further deterioration in visual acuity. CONCLUSION: Optic neuritis is a potentially sight-threatening complication of etanercept therapy. Patients with JRA who are candidates for therapy should be examined by an ophthalmologist before starting treatment and then regularly thereafter. Ophthalmologists and rheumatologists should be aware of this hazard and be cautious when using etanercept in this patient population.