Topical application of methotrexate for inhibition of corneal angiogenesis

· Purpose: Methotrexate (MTX) is a folic acid antagonist used in chemotherapy regimens. Additional therapeutic applications have been suggested based on effect as an immuno-modulating drug in systemic rheumatoid disease and associated uveitis. Since chronic inflammatory disease is often associated with a neovascular response, we investigated the use of MTX for treatment of corneal angiogenesis.· Methods: Neovascularizations were induced by fibroblast growth factor in a corneal pocket model. Vessels were examined biomicroscopically. MTX was applied topically to rabbit corneas in a concentration of 0.2 mg/day. MTX level was measured in aqueous humor and plasma. · Results: On day 9 the vascularized area was 12.0±6.9 mm² in control eyes and significantly smaller, 2.2±1.86 mm², in treated eyes. Treated animals showed no local side effects such as epithelial defects. Although therapeutic levels were measured in the aqueous humor, MTX could not be detected in the serum of treated animals.· Conclusion: The antiangiogenic mechanism of MTX might be due to inhibition of both macrophage invasion during early angiogenesis and endothelial cell proliferation. The high levels in the aqueous humor indicate a possible application of topical MTX for inflammations of the anterior segment of the eye. Received: 4 March 1999 Revised version received: 6 May 1999 Accepted: 6 May 1999     

Pharmacokinetics and safety of intravitreally delivered etanercept

Background The anti-inflammatory drug etanercept may be an effective therapeutic agent in diabetic retinopathy. In order to further evaluate its potential, the pharmacokinetics and safety of this drug after intravitreal delivery were investigated.Methods After intravitreal administration of etanercept in rabbits, clinical examination, electroretinography (ERG), visually evoked potentials (VEP) and histology were evaluated. The pharmacokinetics and distribution of etanercept were analyzed using fluorescence-coupled protein at 0, 2, 4, and 8 weeks after injection in vitreous, retina, and choroid.Results No adverse effects and signs of toxicity were found. Etanercept showed peak concentrations after 4 weeks in the retina and choroid.Conclusions Intravitreally delivered etanercept is safe and results in high concentrations in the retina and choroid over a long period of time.     

Side effects of proton beam therapy of choroidal melanoma in dependence of the dose to the optic disc and the irradiated length of the optic nerve

Graefe's Archive for Clinical and Experimental Ophthalmology - To analyze the impact of the dose to the optic disc and the irradiated length of the optic nerve on radiation-induced optic...     

Pneumatic retinopexy by evaporation of fluorocarbon liquids: in vitro and in vivo results

Purpose To develop an expanding gas tamponade allowing a controlled and complete filling of the vitreous cavity in the non-vitrectomized eye. Methods Twenty-two different liquid fluorocarbon mixtures with a high vapour pressure were tested in an in vitro eye model and in rabbit eyes. The intraocular pressure (IOP), the anterior segment of the eye, the vitreous and the retina were inspected at each examination during a period of 2 weeks. The timepoint of maximal gas expansion and the period required for complete absorption of the gas bubble were recorded. Results In vitro, admixtures of perfluorocarbons (PFCLs) and of semifluorinated alkanes (SFAs) with ether/alkanes generated limited temporary gas expansion but increased IOP. Admixtures of n-pentane in paraffin oil or silicone oil resulted in incomplete gas filling remaining for several days, with moderate IOP. In vivo, different clinical features and gas expansion were observed after the injection of PFCLs saturated with CO₂ or SF₆. Normal IOP was noted, but only with a transient and incomplete gas expansion and tamponade. For example, with n-pentane/n-hexane/perfluoromethylcyclopentane/perfluoromethyl-cyclohexane (1:1:1:1) a very rapid gas expansion was observed, followed by a raised IOP, a shallow anterior chamber, and finally rupture of the globe. The correlation between the in vitro and in vivo data was low. Conclusions Gas endotamponade based on evaporation of liquid fluorocarbons is possible, but a complete and reliable tamponade could not be achieved. The best results were demonstrated by admixtures with an overall density <1.00 g/cm³, an inert carrier with high vapour pressure, and a highly volatile substance. Further detailed investigation into the factors influencing evaporation is required.     

Irradiation for inhibition of endothelial cell growth in vitro

The clinical effect of ionising radiation on ocular neovascularisations is controversial, not only because of the variety of treatment modalities. The aim of our study was to investigate an experimental model which allows to evaluate radiation parameters and to study the mechanism of the inhibitory effect on neoangiogenesis. In vitro experiments were performed using human umbilical vein endothelial cells and human corneal keratocytes. The cells were irradiated with different doses of photon beam radiation and counted daily after treatment. Cell cultures confirmed the efficiency of irradiation in inhibiting proliferation of vascular endothelial cells. Radiosensitivity was shown to be higher in vascular endothelial cells than in corneal stromal keratocytes. This might be helpful in investigating therapy parameters for treating ocular neovascularisations, as well as underlying mechanisms.     

Diabetic retinopathy. Pathophysiology and therapy of hypoxia-induced inflammation

Diabetic retinopathy is the most common chronic microvascular complication associated with diabetes mellitus. The development of diabetic retinopathy is a consequence of metabolic dysregulation. Hyperglycemia is a critical factor which is involved in basement membrane thickening, loss of pericytes and endothelial cells, and retinal capillary nonperfusion. We review the molecular basis of diabetic retinopathy and maculopathy and elaborate the role of growth factors and cytokines in the development of diabetic vascular alterations, their specific influence on the cellular interaction between retinal endothelial cells and pericytes, and the role of intravascular blood components.     

Pigmented retinopathy as a presenting sign of mitochondrial encephalomyopathy without external ophthalmoplegia

Background. Mitochondrial encephalomyopathies result from deletions in the nuclear or mitochondrial (mt) DNA.Deletions in the mtDNA are often sporadic.Mitochondriopathies are commonly associated with chronic progessive external ophthalmoplegia (CPEO).Here we describe a patient with a structural mtDNA aberration whose presenting sign was impaired visual acuity in the presence of a pigmented retinopathy but lack of impaired ocular motility. Patient. A 7-year-old girl presented with impaired visual acuity (0.4 OD and 0.5 OS), coarse hyperpigmentation of the posterior pole and diffuse hyperpigmentation with irregular depigmentation in the periphery. Scotopic and photopic as well as multifocal ERG were abnormal.Further symptoms included an incomplete inner ear deafness, ataxia, lapses of coordination and an intention tremor.Compared with her twin sister, the patient's speech was less modulated and slower. MRI scanning disclosed symmetric changes of density in the basal ganglia and nucleus dentatus as well as in the brainstem. ECG yielded no evidence of an AV-node block. Molecular biological analysis showed a structural rearrangement of the mtDNA. Conclusions. Mitochondrial encephalomyopathies in early ages may present with pronounced retinal changes in the absence of external ophthalmoplegia.Therefore, it appears prudent to include a neuropediatric evaluation as well as a mutation screening of the mtDNA in the evaluation of pediatric patients with diffuse non-specific pigmented retinopathies.     

Pathogenesis of choroidal neovascularization. Old concepts,new questions

Age-related macular degeneration (AMD) is the leading cause of blindness in the developed world but the pathogenesis remains poorly understood.Malfunction of the retinal pigment epithelium (RPE) plays a central role in the disease and leads to either choriodal atrophy or proliferation.This article reviews the current concepts of the development of choriodal atrophy and neovascularisation. Furthermore, available animal models and potential therapeutical targets are discussed.     

Inhibition of inflammatory corneal angiogenesis by TNP-470

PURPOSE: To determine the efficacy of the angiogenic inhibitor TNP-470 on inflammatory corneal neovascularization. Topical and systemic delivery of the drug were investigated in a murine model as well as inhibition of endothelial cell proliferation in vitro and in vivo. METHODS: The effect of TNP-470 on VEGF- and bFGF-stimulated bovine capillary endothelial (BCE) cell proliferation was evaluated in vitro. Corneal neovascularization was induced in vivo by mechanical debridement of the corneal and limbal epithelium with 0.15 M NaOH on C57BL6 mice. TNP-470 was administered systemically at 30 mg/kg body weight (BW) every other day or topically three times daily in a concentration of 5 ng/ml dissolved in methylcellulose. Vessel length was investigated on day 7. VEGF protein content in murine corneas was analyzed by ELISA on days 2, 4, and 7 of treatment. A modified bromouridine (BrdU) ELISA was used to quantify endothelial cell proliferation. RESULTS: TNP-470 exerted a dose-dependent inhibition of bFGF- and VEGF-induced endothelial cell proliferation in vitro. Both systemic and topical application of TNP-470 led to a significant reduction of inflammatory corneal neovascularization (P < 1 x 10(-5)). BrdU labeling showed that TNP-470 inhibited endothelial cell proliferation. VEGF protein levels were reduced by systemic TNP-470 treatment. CONCLUSIONS: These results suggest that TNP-470 reduces inflammatory corneal angiogenesis by directly inhibiting endothelial cell proliferation. Topical and systemic treatment with TNP-470 reduces VEGF levels that are responsible for vessel growth during the neovascularization process.