Identifying the proportion of age related macular degeneration patients who would benefit from photodynamic therapy with verteporfin (Visudyne)

Inhibition of Hypoxia-Inducible Factor-1α and Vascular Endothelial Growth Factor by Chrysin in a Rat Model of Choroidal Neovascularization

Age-related macular degeneration (AMD) is a leading cause of irreversible vision loss among the elderly population. Vascular endothelial growth factor (VEGF) is essential for choroidal neovascularization (CNV) development in advanced, wet AMD. Chrysin (5,7-dihydroxyflavone) is a natural flavonoid with anti-inflammatory, anti-oxidative, and anti-angiogenic effects. We hypothesized that intravitreally injected chrysin may inhibit CNV due to its inhibitory effect on angiogenesis. To determine the effects of chrysin on an experimental CNV model, we induced CNV in Brown Norway rats with a diode laser. One week later, rats were injected intravitreally with chrysin in the right eye and vehicle in the left eye. The following week, we evaluated chrysin’s effects via the CNV grade assessed with fluorescein angiography and histologic analyses. Hypoxia-inducible factor-1 alpha (HIF-1α) and VEGF expression in the retina/choroid complex were also measured in both eyes. The mean CNV grade was significantly lower in chrysin-treated vs. control eyes (2.34 ± 1.14 vs. 2.97 ± 1.05, p < 0.001), as was the mean CNV thickness (33.90 ± 4.89 vs. 38.50 ± 5.43 μm, p < 0.001) and mean HIF-1α and VEGF levels (both p < 0.001). Compared to chrysin-treated eyes, the relative risk of control eyes developing high-leakage lesions was 2.03 (95% confidence interval: 1.46–2.83). Since chrysin inhibited laser-induced CNV and downregulated HIF-1α and VEGF expression, it is a candidate for treating wet AMD and other CNV-associated conditions.

Inhibitory Effect of Chrysin (5,7-Dihydroxyflavone) on Experimental Choroidal Neovascularization in Rats

PURPOSE

The aim of this study was to evaluate the effect of chrysin on laser-induced experimental choroidal neovascularization (CNV) in a rat model.

METHODS

Male brown Norway rats were anesthetized, and a diode laser was used to break Bruch's membrane. One week later, each rat was intravitreally injected with 5 µl of 15 mg/ml chrysin, and CNV development was determined by fluorescein angiography at 2 weeks. The effect of chrysin on experimental CNV was assessed by fluorescein angiography and histology.

RESULTS

Two weeks after laser treatment, the intensity of fluorescein leakage from the photocoagulated lesions decreased significantly compared with the control group (p = 0.044). When the lesions were categorized into low- and high-leakage groups, there was a significant correlation between chrysin treatment and degree of leakage (p = 0.028). Compared with the chrysin-treated group, the relative risk of developing high-leakage lesions in the control group was 3.18. The mean CNV thickness was significantly thinner in chrysin-treated eyes than in control eyes (34.13 ±.0.88 vs. 37.76 ± 0.90 μm, p = 0.005).

CONCLUSION

Chrysin has an inhibitory effect on CNV in an experimental rat model, indicating that chrysin should be further evaluated for its potential as a therapy for CNV in age-related macular degeneration and in other vision-threatening conditions associated with CNV.

Analytical platforms in vitreoretinal proteomics

Current proteomic technologies can effectively be used to study the proteins of the vitreous body and retina in health and disease. The use of appropriate samples, analytical platform and bioinformatic method are essential factors to consider when undertaking such studies. Certain proteins may hinder the detection and evaluation of more relevant proteins associated with pathological processes if not carefully considered, particularly in the sample preparation and data analysis stages. The utilization of more than one quantification technique and database search program to expand the level of proteome coverage and analysis will help to generate more robust and worthwhile results. This review discusses important aspects of sample processing and the use of label and label-free quantitative proteomics strategies applied to the vitreous and retina.

EFFECT OF A NOVEL OCTAPEPTIDE UROKINASE FRAGMENT, A˚6, ON EXPERIMENTAL CHOROIDAL NEOVASCULARIZATION IN THE MONKEY

PURPOSE

To evaluate the inhibitory effects of a urokinase-derived octapeptide, A 6, on laser-induced choroidal neovascularization (CNV) in monkeys.

METHODS

Twenty female cynomolgus monkeys were randomly grouped into weekly or monthly A 6 treatment groups, each consisting of 10 animals. CNV was induced in both eyes by perimacular laser treatment. In each right eye, a single 22.25-mg A 6 dose (monthly group) or 4 22.25-mg A 6 doses each week (weekly group) were given by intravitreal injections. Each left eye received phosphate buffer on the same schedule. Monkeys were observed for 4 weeks by ophthalmic examinations, color photography, and fluorescein angiography.

RESULTS

Weekly treated eyes had a 35% reduction of CNV compared with controls (P = 0.23). In contrast, monthly treated eye had a 71% reduction of CNV compared with controls (P = 0.0009). There was no evidence of toxicity at both clinical and pathologic examinations.

CONCLUSIONS

Intravitreal A 6 injections effectively inhibited CNV in cynomolgus monkeys without evidence of toxicity. The overall reduction in CNV was greater for monthly treated eyes than for weekly treated eyes. This study suggests that A 6 has promise as a local antiangiogenic treatment of CNV. Further work is indicated to evaluate the potential role of A 6 in therapy for human CNV associated with age-related macular degeneration.

Impact of lesion size on photodynamic therapy with verteporfin of predominantly classic lesions in age related macular degeneration

AIM

To determine if photodynamic therapy (PDT) outcomes are related to lesion size in patients with subfoveal predominantly classic choroidal neovascularisation (CNV) secondary to age related macular degeneration (AMD).

METHODS

According to greatest linear dimension (GLD) of the entire lesion determined with fluorescein angiography (FA) patients were divided into two groups. In the first group GLD was <3000 microm and in the second one GLD was 3000-5000 microm. All eyes were treated with standard PDT with the verteporfin protocol. The primary outcome was the proportion of eyes in both groups that did not show significant leakage in FA at the end of follow up. Secondary outcomes were changes in GLD and in best corrected visual acuity (BCVA).

RESULTS

64 patients (mean (SD) age, 76.7 (7.7) years; range 58-95 years) were recruited to participate in the study. All participants in the study completed the follow up time (mean 16.6 months). 24 patients (75%) in the group of smaller lesions (n = 32) compared with 15 patients (46.8%) in the group of larger lesions (n = 32) did not show significant leakage in FA at the end of follow up (p = 0.02). A GLD increase >1000 microm was recorded in nine eyes (28.1%) in the group of smaller lesions and in 16 eyes (50%) in the group of larger lesions (p = 0.07). 22 eyes (68.7%) in the group of smaller lesions compared with 19 eyes (59.3%) in the group of larger lesions lost less than three lines of vision (p = 0.06). Relevant side effects related to verteporfin therapy were not recorded, except for four patients (6.2%) with infusion related back pain.

CONCLUSIONS

These results suggest that lesion size at baseline may be a prognosis factor in PDT in patients with subfoveal predominantly classic CNV secondary to AMD. There are no relevant side effects or safety concerns derived from verteporfin therapy.

Intraocular properties of urokinase-derived antiangiogenic A6 peptide in rabbits

To investigate the intraocular properties of an antiangiogenic peptide, A6, a total of 70 New Zealand rabbit eyes were used. For the toxicity study, 0.05 mL of 0.459 M or 0.148 M A6 was injected intravitreally; right eyes received A6, and left eyes received a vehicle. Serial intraocular pressure measurement, slit lamp, and indirect ophthalmoscopy were performed. The rabbit eyes were evaluated by fluorescein angiography, electroretinography, and histology after the scheduled sacrifice. The pharmacokinetics of an intravitreal A6 (0.05 mL of 0.488 M) and a subtenon A6 (0.5 mL of 0.305 M) injection was studied. There was no toxicity observed following the 0.148 M A6 intravitreal injections. In 2 eyes with a 0.459 M A6 intravitreal injection, focal retinal pigmentary change was observed at the injection site, which was contacted by the hyperosmolar drug bolus. Choroidal A6, following the intravitreal injection, remained therapeutic (>or=10 microM) for 72 hours. The vitreous half-life was 19.4 hours. Choroidal concentrations following the subtenon injection were minimal. The low choroidal concentrations observed may relate to the polar nature of A6. More hydrophobic analogs of A6 are likely to cross the retina more efficiently. However, in diseased eyes, in the area of choroidal neovascularization (CNV), the fluid-filled, damaged, edematous retina may permit the drug to enter the choroid in higher concentrations.

Age-related maculopathy: a genomewide scan with continued evidence of susceptibility loci within the 1q31, 10q26, and 17q25 regions

Age-related maculopathy (ARM), or age-related macular degeneration, is one of the most common causes of visual impairment in the elderly population of developed nations. In a combined analysis of two previous genomewide scans that included 391 families, containing up to 452 affected sib pairs, we found linkage evidence in four regions: 1q31, 9p13, 10q26, and 17q25. We now have added a third set of families and have performed an integrated analysis incorporating 530 families and up to 736 affected sib pairs. Under three diagnostic models, we have conducted linkage analyses using parametric (heterogeneity LOD [HLOD] scores under an autosomal dominant model) and nonparametric (Sall statistic) methods. There is ongoing evidence of susceptibility loci within the 1q31, 10q26, and 17q25 regions. If we treat the third set of families as a replication set, then two regions (10q26 and 17q25) are replicated, with LOD scores >1.0. If we pool all our data together, then four regions (1q31, 2q14.3, 10q26, and 17q25) show HLOD or Sall scores > or =2.0. Within the 1q31 region, we observed an HLOD of 2.72 (genomewide P=.061) under our least stringent diagnostic model, whereas the 17q25 region contained a maximal HLOD of 3.53 (genomewide P=.007) under our intermediate diagnostic model. We have evaluated our results with respect to the findings from several new independent genomewide linkage studies and also have completed ordered subset analyses (OSAs) with apolipoprotein E alleles, smoking history, and age at onset as stratifying covariates. The OSAs generate the interesting hypothesis that the effect of smoking on the risk of ARM is accentuated by a gene in the 10q26 region--a region implicated by four other studies.

The incidence and outcome of photodynamic therapy for macular degeneration in the Northern Region of the UK

PURPOSE

To assess the patients who have had photodynamic therapy (PDT) in the Northern region of the UK, in relation to the eligibility criteria found to benefit in the TAP study (treatment of age-related macular degeneration with photodynamic therapy study), so as to make an estimate of the number of patients who might benefit from this treatment and to present the outcome of the treatment so far.

METHOD

The records and fluorescein angiograms (FFAs) of all patients who had had PDT in the Northern region between 2001 and 2002 were reviewed for compliance with the TAP criteria of >50% classic choroidal neovascularization and >34 letters on the 2 m logMAR Early Treatment Diabetic Retinopathy Study chart. NHS funding has been available in the Northern Region since January 2001 for 'second eye' involvement. A review of all the angiograms performed for exudative macular degeneration in 1 year was also performed. The visual outcome of those patients 1 year from baseline was measured.

RESULTS

A total of 82 'second eye' patients were treated between January 2001 and December 2002. This gives an incidence of 65 per 3 million and so about 1300 in the whole of the UK (population 60 million). In all, 238 FFAs were performed on exudative macular degeneration, with 21% being found eligible for PDT. As of February 2003, 54 TAP criteria, macular degeneration patients were 1 year from initial treatment. Of these, 12 had incomplete follow-up and 13 patients had lost more than 15 letters. The responder rate defined as losing <15 letters was 42-13/42=69%. Seven of those who did not make 1-year follow-up had lost more than 15 letters when last seen, giving a responder rate of 54-20/54=63%.

CONCLUSION

There may not be as many patients eligible for PDT, using the TAP criteria, as previously hoped. The outcome of treatment appears similar to that found in the TAP study.

Inhibition of choroidal neovascularization in rats by the urokinase-derived peptide A6

PURPOSE

To evaluate the inhibitory effects of a urokinase-derived octapeptide A6 on laser-induced choroidal neovascularization (CNV).

METHODS

In the first arm of the study, subcutaneous injection of A6 (200 mg/kg per day) into the right eyes in 20 rats and phosphate-buffered saline in 20 control rats was started 1 day before laser injury. Angiography was performed at week 2. To evaluate the dose response, a second arm of the study was performed in the left eyes. Half of the treatment group was treated with 400 mg/kg per day, and the remaining half continued to receive 200 mg/kg per day beginning on week 4. Laser injury was made at week 5 and angiography was performed at week 7. Angiographic evaluation, histopathologic evaluation including maximum CNV thickness and factor-VIII-stained endothelium counting were performed in the second arm of the study. Choroidal concentrations of A6 were measured.

RESULTS

In the first arm of the study, angiography showed a 40.8% reduction in CNV in the 200-mg/kg per day treatment group, compared with the control (P = 0.0008). In the second arm of the study, angiographic reduction in CNV was 37.9% in the 200-mg/kg per day group (P = 0.0314) and 70.0% in the 400-mg/kg per day group (P = 0.0124), compared with the control. CNV was significantly less in the 400-mg/kg per day group than in the 200-mg/kg per day group (P = 0.0393). Both CNV thickness and number of endothelial cells were reduced in a dose-dependent manner and significantly less than in the control (P < 0.05). Mean choroidal concentration of A6 2 hours after injection was 0.72 micro M in the 200-mg/kg per day (100 mg/kg every 12 hours) and 1.75 micro M in the 400-mg/kg per day (200 mg/kg every 12 hours) treatment groups. Levels at 11 hours after injections were undetectable.

CONCLUSIONS

A6 demonstrated antiangiogenic properties in a rat model of CNV and may be useful in the treatment of CNV.

Sub-retinal neovascular membrane in exudative macular degeneration

Age-related macular degeneration is a major cause of serious vision loss. The earliest stages of age-related maculopathy may be defined by the size of the drusen present in the macula and the effects on vision. Further manifestations may include soft drusen, choroidal neovascularisation, macular haemorrhage and cicatricial or disciform degeneration of the macula. This report describes a patient with a macular haemorrhage, a choroidal neovascular membrane and serious loss of vision. In addition, the pathogenesis, diagnosis and treatment options of macular degeneration are reviewed.