Upregulation of pigment epithelium-derived factor after laser photocoagulation

Vitreous levels of pigment epithelium-derived factor and vascular endothelial growth factor in diabetic and non-diabetic retinopathy: associated factors and anatomical correlation

BACKGROUND

This study aims to investigate the factors affecting the vitreous levels of pigment epithelium-derived factor (PEDF) and vascular endothelial growth factor (VGEF) among patients with pars plana vitrectomy (PPV). Also, this study correlates the levels of PEDF with RRD characteristics.

METHODS

All patients who were scheduled for PPV for any indication were included in the study. They were divided into a case group which included patients with advanced PDR and a control group which included the remaining diagnoses. During the PPV, an undiluted vitreous sample was taken and the enzyme-linked immunosorbent assay method was utilized to measure the levels of VEGF and PEDF.

RESULTS

Eighty eyes were involved. Patients diagnosed with advanced PDR and endophthalmitis exhibited higher levels of VEGF. PEDF was affected inversely by the age of the patients and PEDF levels were higher in RRD and endophthalmitis cases. In patients with RRD, the level of PEDF was higher if the tear was found inferiorly, if the macula was detached, and with a longer duration of RRD.

CONCLUSIONS

This study highlights the clinical importance of those biomarkers. Anti-VEGF-based treatment is the mainstay against PDR. PEDF may show a promising predictive values regarding patients with RRD.

The progress of assessment methods and treatments of neovascular glaucoma secondary to central retinal vein occlusion

Neovascular glaucoma is a condition that results from central retinal vein occlusion and often leads to blindness. Accurate evaluation and appropriate treatment are crucial for patients. However, there is currently no uniform and clear standard to differentiate between ischemic and non-ischemic central retinal vein occlusion. Also, the assessment of neovascular glaucoma progression is uncertain. Meanwhile, although pan-retinal photocoagulation is a standard treatment to prevent the onset of neovascular glaucoma, its actual efficacy and the timing of intervention remain highly controversial. It is still challenging to balance the risks of side effects in the visual field against the uncertain effectiveness of the treatment. This paper delves into the pathogenesis of neovascular glaucoma to understand the development of therapeutic approaches. By taking into account various assessment criteria of central retinal vein occlusion and neovascular glaucoma over the years, combining functional tests and morphological tests provides the most accurate and rigorous solution. The age of patients, the extent, location, and duration of retinal ischemia are the primary factors that affect the severity and extent of ischemic central retinal vein occlusion and induce serious complications. From the perspective of prevention and treatment, the ischemic index is closely related to the development of neovascularization. The paper provides essential insights into the mechanism, efficacy, complications, and optimal timing of pan-retinal photocoagulation. Comparing the treatment effects of pan-retinal photocoagulation and intravitreal anti-VEGF injections, we suggest a combination of both treatments to explore effective treatment with fewer side effects in the long term. This article details the debate on the above issues and explores ideas for the clinical diagnosis and preventive treatment of neovascular glaucoma that results from ischemic central retinal vein occlusion.

Current and Novel Therapeutic Approaches for Treatment of Diabetic Macular Edema

Diabetic macular edema (DME) is a major ocular complication of diabetes mellitus (DM), leading to significant visual impairment. DME’s pathogenesis is multifactorial. Focal edema tends to occur when primary metabolic abnormalities lead to a persistent hyperglycemic state, causing the development of microaneurysms, often with extravascular lipoprotein in a circinate pattern around the focal leakage. On the other hand, diffusion edema is due to a generalized breakdown of the inner blood–retinal barrier, leading to profuse early leakage from the entire capillary bed of the posterior pole with the subsequent extravasation of fluid into the extracellular space. The pathogenesis of DME occurs through the interaction of multiple molecular mediators, including the overexpression of several growth factors, including vascular endothelial growth factor (VEGF), insulin-like growth factor-1, angiopoietin-1, and -2, stromal-derived factor-1, fibroblast growth factor-2, and tumor necrosis factor. Synergistically, these growth factors mediate angiogenesis, protease production, endothelial cell proliferation, and migration. Treatment for DME generally involves primary management of DM, laser photocoagulation, and pharmacotherapeutics targeting mediators, namely, the anti-VEGF pathway. The emergence of anti-VEGF therapies has resulted in significant clinical improvements compared to laser therapy alone. However, multiple factors influencing the visual outcome after anti-VEGF treatment and the presence of anti-VEGF non-responders have necessitated the development of new pharmacotherapies. In this review, we explore the pathophysiology of DME and current management strategies. In addition, we provide a comprehensive analysis of emerging therapeutic approaches to the treatment of DME.

Study on Factors Associated with High Myopia CNV in Aqueous Humor and Serum

Objective

The objective is to investigate the relationship and correlation between PEDF and TGF-β in aqueous humor and serum and high myopia CNV lesions.

Methods

For each group of patients (namely, group A: patients with high myopia CNV (mCNV); group B: patients with high myopia without CNV; group C: patients with CNV caused by other eye diseases; and group D (control group): patients with simple cataract (without CNV and high myopia)), 20 patients were collected. A total of 40 patients have been collected since the beginning of the study in December 2020, including 7 patients in group A, 13 patients in group B, 10 patients in group C, and 10 patients in group D. Serum and aqueous humor samples were collected, and PEDF and TGF-β levels in serum and aqueous humor were detected by enzyme-linked immunosorbent assay (ELISA). SPSS 26.0 statistical software was used to process the data. Independent sample t-test was used to compare the data of the same factor in the same group between serum and aqueous humor. Comparisons of the same factors between different groups were performed using a one-way analysis of variance (ANOVA). Correlation analysis was conducted by the Pearson correlation coefficient test. P < 0.05 indicated that the difference was statistically significant.

Results

There were no significant differences in age, gender, and course of disease among all groups (P > 0.05). The concentration of PEDF in aqueous humor in group A and group C was higher than that in group B and group D. There was no significant correlation between serum PEDF content and the above-mentioned diseases. The concentration of TGF-β in aqueous humor in groups A, B, and C was significantly higher than that in group D. However, there was no significant correlation between TGF-β content in serum and the above-mentioned diseases. There was no significant correlation between aqueous humor and serum PEDF. There was no significant correlation between the content of TGF-β in aqueous humor and serum.

Conclusion

TGF-β in aqueous humor may be involved in the development of high myopia and intraocular CNV disease. However, PEDF in aqueous humor may be involved in the development of intraocular CNV disease and has no significant correlation with high myopia. At the same time, TGF-β and PEDF in serum had no significant correlation with high myopia and intraocular CNV disease. There was no significant correlation between the concentrations of TGF-β and PEDF in aqueous humor and serum.

Dysregulation of the NLRP3 Inflammasome in Diabetic Retinopathy and Potential Therapeutic Targets

Diabetic Retinopathy (DR) is an insidious neurovascular disorder secondary to chronic glycemic dysregulation in elderly diabetic patients. In the later stages of DR, the disease manifests as fluid infiltrating the macula, culminating in the leading cause of irreversible visual impairment in working age adults. With the current mainstay treatments preoccupied with slowing down the progression of DR, this presents an unsustainable solution from both an economic and quality of life perspective. Although the exact mechanisms by which hyperglycemia leads to retinal tissue insult are unknown, the evidence suggests that chronic low-grade inflammation in diabetic eye is in part driving the constellation of symptoms present in DR. Of the innate immune system within the eye, the NLR Family Pyrin Domain Containing 3 Inflammasome (NLRP3) has been identified in retinal cells as a causal factor in the pathogenesis of DR. Multiple pathways appear to be present in the diabetic eye that instigate prolonged activation of the NLRP3 which subsequently exerts its deleterious effects by upregulating the release of Interleukin-1Beta and Interleukin-18. In this review, we highlight the current understanding of the pathophysiology of DR, the dysregulation of the NLRP3 secondary to hyperglycemic stress in retinal cells, and novel therapeutic targets to alleviate overactivation of the inflammasome.

Subthreshold micropulse yellow laser for the management of refractory cystoid macular edema consequent to complicated cataract surgery

PURPOSE

To report the safety and efficacy of subthreshold micropulse yellow laser of 577 nm for a complex case of refractory pseudophakic cystoid macular edema.

METHODS

A retrospective chart review of an interventional case report of three subthreshold micropulse yellow laser interventions for refractory pseudophakic cystoid macular edema.

PATIENT

A 77-year-old healthy female underwent pseudoexfoliative cataract surgery complicated by posterior capsule rupture and sulcus intraocular lens implantation. After 3 months, she required a scleral fixation of the same lens, due to a lack of capsular support and decentration of the intraocular lens. One month later, she experienced a severe pseudophakic cystoid macular edema (foveal thickness of 399 µm and best-corrected visual acuity of 20/80 Snellen). The condition was refractory to conventional treatments prior to subthreshold micropulse yellow laser interventions, including non-steroidal anti-inflammatory eye drops, topical steroids, oral indomethacin and three sub-Tenon's triamcinolone injections, attempted over a 14-month period.

RESULTS

Subthreshold micropulse yellow laser treatment was performed and immediate resolution was achieved and maintained for 2 months. Two cases of edema relapse were observed at 3 months from initial laser treatment and again at 4 months from the second laser treatment. Final patient's follow-up at 6 months from the third laser treatment evidenced the absence of edema, improved visual acuity (foveal thickness of 265 µm/best-corrected visual acuity of 20/30 Snellen) and the absence of complications.

CONCLUSIONS

Subthreshold micropulse yellow laser seems to be a safe and effective treatment for short-term resolution of refractory pseudophakic cystoid macular edema after complicated cataract surgery and represents a useful alternative to expensive and invasive therapies. A trend towards a longer duration of edema resolution with every subthreshold micropulse yellow laser repetition was observed.

The Role of Subthreshold Micropulse Yellow Laser as an Alternative Option for the Treatment of Refractory Postoperative Cystoid Macular Edema

BACKGROUND

To evaluate the efficacy and the safety of subthreshold micropulse yellow laser (SMYL) in the treatment of chronic postoperative cystoid macular edema (PCME), which is refractory to standard therapies.

METHODS

A retrospective chart review of ten eyes of ten patients affected by refractory PCME who underwent SMYL was performed. Five PCME cases were subsequent to uncomplicated cataract surgery (CS), two cases to complicated CS (CCS) with posterior capsule rupture and three cases occurred after retinal detachment surgery (RD). All conditions were refractory to conventional treatments prior to SMYL interventions for at least 4 months, including nonsteroidal anti-inflammatory eyedrops, topical steroids, oral indomethacin, sub-Tenon's triamcinolone injections and Dexamethasone intravitreal implants. All patients underwent one or more treatments with 577 nm SMYL photo-stimulation, with 7 × 7 grids with confluent spots and a 5% duty cycle covering the whole edematous retina, including the foveal center. Best corrected visual acuity (BCVA) and central macular thickness (CMT) were obtained using OCT, and evaluated before and after the treatment at 1, 2, 3 and 6-month follow-ups.

RESULTS

A complete subfoveal macular edema resolution was observed in all of the eyes, with statistically significant improvements in terms of BCVA and CMT in all of the follow-up timelines (at 6 months, p = 0.002 and p = 0.005, respectively). The mean number of laser treatments was 1.3. At the final follow-up, a complete subfoveal edema reabsorption was observed in all patients with visual acuity improvement. No complications were observed in any case.

CONCLUSIONS

SMYL seems to be a safe and effective treatment for the long-term resolution of refractory PCME and may be a useful alternative to expensive and invasive therapeutic options.

Human vitreous in proliferative diabetic retinopathy: Characterization and translational implications

Diabetic retinopathy (DR) is one of the leading causes of visual impairment in the working-age population. DR is a progressive eye disease caused by long-term accumulation of hyperglycaemia-mediated pathological alterations in the retina of diabetic patients. DR begins with asymptomatic retinal abnormalities and may progress to advanced-stage proliferative diabetic retinopathy (PDR), characterized by neovascularization or preretinal/vitreous haemorrhages. The vitreous, a transparent gel that fills the posterior cavity of the eye, plays a vital role in maintaining ocular function. Structural and molecular alterations of the vitreous, observed during DR progression, are consequences of metabolic and functional modifications of the retinal tissue. Thus, vitreal alterations reflect the pathological events occurring at the vitreoretinal interface. These events are caused by hypoxic, oxidative, inflammatory, neurodegenerative, and leukostatic conditions that occur during diabetes. Conversely, PDR vitreous can exert pathological effects on the diabetic retina, resulting in activation of a vicious cycle that contributes to disease progression. In this review, we recapitulate the major pathological features of DR/PDR, and focus on the structural and molecular changes that characterize the vitreal structure and composition during DR and progression to PDR. In PDR, vitreous represents a reservoir of pathological signalling molecules. Therefore, in this review we discuss how studying the biological activity of the vitreous in different in vitro, ex vivo, and in vivo experimental models can provide insights into the pathogenesis of PDR. In addition, the vitreous from PDR patients can represent a novel tool to obtain preclinical experimental evidences for the development and characterization of new therapeutic drug candidates for PDR therapy.

Translational Preclinical Pharmacologic Disease Models for Ophthalmic Drug Development

Preclinical models of human diseases are critical to our understanding of disease etiology, pathology, and progression and enable the development of effective treatments. An ideal model of human disease should capture anatomical features and pathophysiological mechanisms, mimic the progression pattern, and should be amenable to evaluating translational endpoints and treatment approaches. Preclinical animal models have been developed for a variety of human ophthalmological diseases to mirror disease mechanisms, location of the affected region in the eye and severity. These models offer clues to aid in our fundamental understanding of disease pathogenesis and enable progression of new therapies to clinical development by providing an opportunity to gain proof of concept (POC). Here, we review preclinical animal models associated with development of new therapies for diseases of the ocular surface, glaucoma, presbyopia, and retinal diseases, including diabetic retinopathy and age-related macular degeneration (AMD). We have focused on summarizing the models critical to new drug development and described the translational features of the models that contributed to our understanding of disease pathogenesis and establishment of preclinical POC.

Micropulse Trabeculoplasty in Open Angle Glaucoma

Background:

We report the effect of micropulse laser trabeculoplasty (MLT) in the intraocular pressure (IOP) of patients with uncontrolled open-angle glaucoma (OAG).

Materials and Methods:

In this retrospective review, 30 eyes with OAG were treated with a single session of MLT at the Vista Clinic in Lima Perú. We used a 532 nm frequency doubled Nd: YAG laser to 360° of the trabecular meshwork with a power of 1000 mW, 15% of the duty cycle, and 300 ms of exposure. The IOP was measured at baseline and at 1 day, 1 week, 3 months, and 6 months post-treatment and were followed up for one last control.

Results:

The mean baseline IOP was 15.6 mmHg and in the last control was 12.8 mmHg, mean follow-up time of 19 months (±10 standard deviation [SD]). The mean reduction of IOP in the 1^st day was 1.6 mmHg (±2.6 SD) and 1.2 mmHg (±3.3 SD) in the last follow-up. The mean percentage of IOP reduction was 17.9% and 7 eyes (40%) had IOP reduction >20%. No statistical significant difference in relation to demographic characteristics of the patients. The greatest reduction was achieved in the 1^st day with a median of 2.00 (P < 0.001). A tendency to achieve a higher reduction of IOP in patients with higher baseline IOP was found but was not statistically significant. No adverse reactions occurred.

Conclusions:

MLT slightly reduced the IOP in a few patients with uncontrolled OAG for a very short time and may not be suitable for these patients.

Diabetic Retinopathy: Pathophysiology and Treatments

Diabetic retinopathy (DR) is the most common complication of diabetes mellitus (DM). It has long been recognized as a microvascular disease. The diagnosis of DR relies on the detection of microvascular lesions. The treatment of DR remains challenging. The advent of anti-vascular endothelial growth factor (VEGF) therapy demonstrated remarkable clinical benefits in DR patients; however, the majority of patients failed to achieve clinically-significant visual improvement. Therefore, there is an urgent need for the development of new treatments. Laboratory and clinical evidence showed that in addition to microvascular changes, inflammation and retinal neurodegeneration may contribute to diabetic retinal damage in the early stages of DR. Further investigation of the underlying molecular mechanisms may provide targets for the development of new early interventions. Here, we present a review of the current understanding and new insights into pathophysiology in DR, as well as clinical treatments for DR patients. Recent laboratory findings and related clinical trials are also reviewed.

Advances in Retinal Laser Therapy

Since the 1960s, laser therapies have played a critical role in the treatment of numerous retinal diseases. Significant advances have been made in laser technology and the molecular understanding of laser-tissue interactions over the past 55 years to maximize the therapeutic effect while minimizing side-effects. While pharmacologic therapies (e.g., anti-vascular endothelial growth factor or anti-VEGF) are playing a larger role, laser therapy remains an important treatment modality for proliferative diabetic retinopathy (PDR), diabetic macular edema (DME), sickle cell retinopathy, retinal vein occlusions, central serous chorioretinopathy, tumors, polypoidal choroidal vasculopathy, and retinal tears. With the development new laser technologies such as selective retinal therapy, subthreshold micropulse laser, nanosecond laser, photomediated ultrasound therapy, and navigated laser, the risk of adverse events has been significantly reduced. This review summarizes the latest developments in retinal laser therapy.

Identification of vitreous proteins in retinopathy of prematurity

Retinopathy of prematurity (ROP) is a disorder of blood vessels in the retina developed in premature infants and the leading cause of the blindness in children. Proteomic analysis was performed to identify vitreous proteins specific to patients with ROP. Vitreous humor samples were obtained from three patients with ROP and two patients with congenital cataract, the latter included as a control group. The vitreous samples were separated by 2D-PAGE and the proteins running as definitive spots were identified by MALDI-TOF MS spectrometry. We identified 13 and 6 proteins in the vitreous from ROP and cataract patients, respectively. Albumin, transferrin, pigment epithelium-derived factor (PEDF) and transthyretin were found in both patient groups. In the samples from ROP patients, PEDF and transthyretin levels were lower than in those from cataract patients, and retinol binding protein 3 and prostaglandin D synthase were not detected. Of the 13 proteins, 9 proteins including α-2-macroglobulin, ceruloplasmin, α-fetoprotein, vitamin D-binding protein, α-1-antitrypsin, α-1-β-glycoprotein, hemopexin, apolipoprotein A-1 and A-lV were found in vitreous samples of only the ROP patients. PEDF has anti-angiogenic and neurotrophic functions. Whether PEDF is increased or decreased in diabetic retinopathy has been controversial but we observed lower PEDF in the ROP samples than in the controls. The proteins specific to or decreased in ROP, if confirmed in future studies, may provide clue to understanding its pathogenesis.

New Developments in the Classification, Pathogenesis, Risk Factors, Natural History, and Treatment of Branch Retinal Vein Occlusion

For years, branch retinal vein occlusion is still a controversial disease in many aspects. An increasing amount of data is available regarding classification, pathogenesis, risk factors, natural history, and therapy of branch retinal vein occlusion. Some of the conclusions may even change our impression of branch retinal vein occlusion. It will be beneficial for our doctors to get a deeper understanding of this disease and improve the treatment skills. The aims of this review is to collect the information above and report new ideas especially from the past a few years.

Diabetic macular oedema

Diabetic macular oedema, characterised by exudative fluid accumulation in the macula, is the most common form of sight-threatening retinopathy in people with diabetes. It affects one in 15 people with diabetes resulting in more than 20 million cases worldwide. Few epidemiological studies have been done to specifically investigate risk factors for diabetic macular oedema, although poor glycaemic and blood pressure control are associated with the presence and development of the disorder. The pathophysiological processes begin with chronic hyperglycaemia, and interplay between vascular endothelial growth factor (VEGF) and inflammatory mediators. Non-invasive imaging using optical coherence tomography has allowed clinicians to detect mild levels of diabetic macular oedema in order to monitor progress and guide treatment. Although focal or grid laser photocoagulation was the traditional mode of treatment, intraocular pharmacotherapy with anti-VEGF agents is now the standard of care. However, these therapies are expensive and resource intensive. Emerging therapeutic strategies include improving efficacy and duration of VEGF suppression, targeting alternative pathways such as inflammation, the kallikrein-kinin system, the angiopoietin-Tie2 system, and neurodegeneration, and using subthreshold and targeted laser therapy. Ongoing research should lead to improvements in screening, diagnosis, and management of diabetic macular oedema.

Low-Fluence Photodynamic Therapy versus Subthreshold Micropulse Yellow Wavelength Laser in the Treatment of Chronic Central Serous Chorioretinopathy

Purpose. To compare the efficacy and safety of subthreshold micropulse yellow wavelength laser (SMYL) and low-fluence photodynamic therapy (PDT) in the treatment of chronic central serous chorioretinopathy (CSC). Methods. Thirty-three eyes of 30 patients with chronic CSC received either PDT (18 eyes) or SMYL (15 eyes) therapy. Best corrected visual acuity (BCVA), subretinal fluid (SRF) height, and central macular thickness (CMT) were evaluated at the baseline visit and one, three, six, nine, and 12 months after the therapy. Results. After 12 months, mean BCVA improved from 67.3 ± 14.2 to 71.5 ± 21.4 ETDRS letters in SMYL group and from 60.7 ± 16.3 to 64.4 ± 24.9 ETDRS letters in PDT group (p = 0.285 and p = 0.440, resp.). Mean CMT decreased from 242.8 ± 80 μm to 156.9 ± 60 μm in the PDT group and from 287.3 ± 126 μm to 138.0 ± 40 μm in the SMYL group (p = 0.098 and p = 0.003, resp.). SRF resolved completely in 72.2% and 80.0% of the eyes in the PDT and SMYL groups, respectively. Mean SRF height decreased from 117.2 ± 58 μm to 31.3 ± 56 μm in the PDT group and from 130.0 ± 104 μm to 12.5 ± 21 μm in the SMYL group (p = 0.031 and p = 0.014, resp.). Conclusions. Subthreshold micropulse yellow wavelength laser seems to be effective in the treatment of chronic CSC without any side effect and results in the resorption of SRF without causing visible retinal scarring.

New Diagnostic and Therapeutic Approaches for Preventing the Progression of Diabetic Retinopathy

Diabetic retinopathy (DR) is a severe sight-threatening complication of diabetes mellitus. Retinal laser photocoagulation, antivascular endothelial growth factors, steroid therapy, and pars plana vitrectomy are now used extensively to treat advanced stages of diabetic retinopathy. Currently, diagnostic devices like ultrawide field fundus fluorescein angiography and the improvement of optical coherence tomography have provided quicker and more precise diagnosis of early diabetic retinopathy. Thus, treatment protocols have been modified accordingly. Various types of lasers, including the subthreshold micropulse laser and RPE-targeting laser, and selective targeted photocoagulation may be future alternatives to conventional retinal photocoagulation, with fewer complications. The new developed intravitreal medications and implants have provided more therapeutic options, with promising results.

Recent developments in laser treatment of diabetic retinopathy

Laser photocoagulation has been the mainstay of diabetic retinopathy treatment since its development in mid-20^th century. With the advent of antivascular endothelial growth factor therapy, the role of laser therapy appeared to be diminished, however many advances in laser technology have been developed since. This review will describe recent advances in laser treatment of diabetic retinopathy including pattern scan laser, short-pulse duration and a reduced fluence laser, and navigated laser system for proliferative diabetic retinopathy and macular edema.

Direct photocoagulation to leakage points to treat chronic macular edema associated with branch retinal vein occlusion: a pilot study

Summary statement

Direct photocoagulation reduces the central foveal thickness (CFT) in cases with chronic branch retinal vein occlusion (BRVO) of longer than 12 months duration. Photo-coagulation might be effective for chronic macular edema due to branch retinal vein occlusion.

Background

The aim was to investigate the effect of direct photocoagulation for treating chronic macular edema associated with BRVO.

Methods

This study was a noncomparative, pilot interventional case series. We examined the CFT and best-corrected visual acuity over 6 months in patients with BRVO treated with direct photocoagulation.

Results

Sixteen eyes of 16 patients had been treated with direct photocoagulation (mean follow-up period, 20.5 months). The mean CFT decreased significantly (P<0.001) between the baseline (465 μm) and the final visit (304 μm). The mean (logarithm of the minimum angle of resolution equivalent) best-corrected visual acuity at the baseline was 0.39 and improved significantly (P<0.001) to 0.20 at the final visit.

Conclusion

Direct photocoagulation to leakage points is beneficial for treating chronic macular edema associated with chronic BRVO of longer than 12 months duration.

Laser-based strategies to treat diabetic macular edema: history and new promising therapies

Diabetic macular edema (DME) is the main cause of visual impairment in diabetic patients. The management of DME is complex and often various treatment approaches are needed. At the present time, despite the enthusiasm for evaluating several new treatments for DME, including the intravitreal pharmacologic therapies (e.g., corticosteroids and anti-VEGF drugs), laser photocoagulation still remains the current standard in DME. The purpose of this review is to update our knowledge on laser photocoagulation for DME and describe the developments in laser systems. And we will also discuss the new laser techniques and review the latest results including benefits of combined therapy. In this paper, we briefly summarize the major laser therapeutics for the treatment of diabetic macular edema and allude to some future promising laser therapies.

Targeting Neovascularization in Ischemic Retinopathy: Recent Advances

Pathological retinal neovascularization (RNV) is a common micro-vascular complication in several retinal diseases including retinopathy of prematurity, diabetic retinopathy, age-related macular degeneration and central vein occlusion. The current therapeutic modalities of RNV are invasive and although they may slow or halt the progression of the disease they are unlikely to restore normal acuity. Therefore, there is an urgent need to develop treatment modalities, which are less invasive and therefore associated with fewer procedural complications and systemic side effects. This review article summarizes our understanding of the pathophysiology and current treatment of RNV in ischemic retinopathies; lists potential therapeutic targets; and provides a framework for the development of future treatment modalities.

Microphthalmia-associated transcription factor acts through PEDF to regulate RPE cell migration

Cells of the retinal pigment epithelium (RPE) play major roles in metabolic functions, maintenance of photoreceptor function, and photoreceptor survival in the retina. They normally form a stable monolayer, but migrate during disease states. Although growth factors produced by the RPE cells primarily control these cellular events, how these factors are regulated in RPE cells remain largely unknown. Here we show that the basic-helix-loop-helix-leucine zipper microphthalmia-associated transcription factor (MITF), which plays central roles in the development and function of a variety of cell types including RPE cells, upregulates the expression of a multifunctional factor PEDF in RPE cells. Consequently, the upregulation of PEDF impairs microtubule assembly and thus inhibits RPE cell migration. Conversely, specific knockdown of PEDF partially rescues the impairment of microtubule assembly and cell migration proceeds in MITF overexpressing stable cells. We conclude that MITF acts through PEDF to inhibit RPE cell migration and to play a significant role in regulating RPE cellular function. We suggest that MITF has a novel and important role in maintaining RPE cells as a stable monolayer and the down-regulation of PEDF that may contribute to retinal degenerative diseases.

Micropulsed diode laser therapy: evolution and clinical applications

Many clinical trials have demonstrated the clinical efficacy of laser photocoagulation in the treatment of retinal vascular diseases, including diabetic retinopathy. There is, however, collateral iatrogenic retinal damage and functional loss after conventional laser treatment. Such side effects may occur even when the treatment is appropriately performed because of morphological damage caused by the visible endpoint, typically a whitening burn. The development of the diode laser with micropulsed emission has allowed subthreshold therapy without a visible burn endpoint. This greatly reduces the risk of structural and functional retinal damage, while retaining the therapeutic efficacy of conventional laser treatment. Studies using subthreshold micropulse laser protocols have reported successful outcomes for diabetic macular edema, central serous chorioretinopathy, macular edema secondary to retinal vein occlusion, and primary open angle glaucoma. The report includes the rationale and basic principles underlying micropulse diode laser therapy, together with a review of its current clinical applications.

Pigment epithelium-derived factor and vascular endothelial growth factor in branch retinal vein occlusion with macular edema

BACKGROUND

We investigated whether pigment epithelium-derived factor (PEDF) or vascular endothelial growth factor (VEGF) influence macular edema in patients with branch retinal vein occlusion (BRVO). This investigation aimed to clarify the influence of PEDF in the vitreous fluid on retinal vascular permeability in patients with macular edema secondary to BRVO. The findings were expected to be useful for the treatment of macular edema in BRVO patients.

METHODS

This was a retrospective cross-sectional comparative case series. Thirty-three BRVO patients with macular edema and 24 control patients with nonischemic ocular diseases were enrolled. Retinal ischemia was evaluated by measuring the area of capillary nonperfusion on fluorescein angiography with Scion Image software. Macular edema was examined by optical coherence tomography. Vitreous fluid samples were obtained via pars plana vitrectomy, and the VEGF and PEDF levels were determined by enzyme-linked immunosorbent assay.

RESULTS

The vitreous level of VEGF was significantly higher in BRVO patients than controls (P < 0.001). The vitreous PEDF level was significantly lower in BRVO patients than controls (P = 0.026). In BRVO patients, vitreous levels of PEDF and VEGF showed a significant negative correlation with each other (P < 0.001). Additionally, the vitreous VEGF level had a significant positive correlation (P < 0.001) and the vitreous PEDF level had a significant negative correlation (P < 0.001) with the nonperfused retinal area in BRVO patients. Furthermore, vitreous levels of VEGF and PEDF showed significant positive (P = 0.001) and negative (P = 0.014) correlations, respectively, with macular edema in BRVO patients.

CONCLUSIONS

VEGF and PEDF may inversely influence retinal vascular permeability in patients with ischemic BRVO and macular edema. However, prospective validation will be needed to confirm these observations.

Diabetic macular edema: classification, medical and laser therapy

PURPOSE

to propose and describe a new classification of diabetic macular edema (DME) based on its etiopathogenetic features and to present efficacy and safety data on medical and laser treatments currently used and under investigation.

METHODS

available literature on DME has been reviewed and information provided by contact lens biomicroscopy, fluorescein angiography and optical coherence tomomography has been combined; published data from trials and reports investigating effectiveness of medical and laser treatments were also analyzed.

RESULTS

DME was classified according to its main etiopathogenetic components: prevalently retinovascular, tractional and with taut attached posterior hyaloid, each of them having peculiar aspects on fundus, angiographic and tomographic examination. Focal laser treatment remains the only effective intervention, as shown by a large randomized controlled trial, but new less-invasive photocoagulation strategies (i.e., light laser photocoagulation and subthreshold micropulse diode laser) as well as pharmacological approaches (i.e., antioxidants, PKC inhibitors, aldose-reductase and AGE inhibitors, VEGF inhibitors, intravitreal triamcinolone) are emerging.

CONCLUSIONS

based on our review a classification of DME was developed that may prove useful in making the appropriate treatment decision; the new laser and pharmacological treatments currently investigated are promising and need to be confirmed by large, controlled clinical trials.

Pigment epithelium derived factor (PEDF) is neuroprotective in two in vitro models of Parkinson's disease

Transplantation of retinal pigment epithelial (RPE) cells in the basal ganglia has been proposed as a novel cell-based therapy for Parkinson's disease (PD), by providing a constant source of dopamine replacement via the melanin synthetic pathway enzyme tyrosinase. We have demonstrated previously that human RPE cells also produce a neurotrophic effect on primary cultures of rat striata mesencephalic (dopaminergic) neurons and showed that pigment epithelium derived factor (PEDF) accounted for a major portion of the neurotrophic effect. We now have also begun studies that demonstrate that the neurotrophic effect of PEDF corresponds to neuroprotection against toxins used to produce experimental PD. This was shown in (1) rotenone and (2) 6-hydroxydopamine (6-OHDA) in vitro models. The toxins were added at day 10 in culture, PEDF was added 1h prior. The cultures were fixed and analyzed after tyrosine hydroxylase (TH) immunocytochemical staining. Cell count of TH+ neurons clearly shows the neuroprotective potential of PEDF in both neurotoxin models. The neurotoxic effect of rotenone (25nM) on dopaminergic neurons is reversed by addition of PEDF. At a concentration of 1ng/ml PEDF the neurotoxic effect of rotenone is completely counteracted. PEDF (1ng/ml) has also a neuroprotective effect in the 6-OHDA midbrain in vitro model. The effect is most pronounced at concentrations of 25microM and 50microM 6-OHDA. We conclude that the neurotrophic factor PEDF, produced from RPE cells, can improve neuronal survival in models of PD, and plan to test if this effect can be observed using in vivo models of PD following RPE transplantation.

Therapeutic potential of novel modulators of neovascularization

Neovacularization is an important biological process whereby new blood vessels develop in both health and disease. During development, blood vessels are formed from mesodermal cells in a process called vasculogenesis. The vascular network then expands by the sprouting of new vessel networks from pre-established vessels in a process known as angiogenesis. However, in adult life, undesirable neovascularization is associated with tumor development and a growing list of 'angiogenesis-dependent' diseases, including cardiovascular complications. Furthermore, diseases characterized by ischemia-induced tissue damage cause a neovascularization response to facilitate tissue repair. Recent research has identified novel molecular and cellular mediators of neovascularization that, in adult life, recapitulate angiogenic processes observed during embryonic development. The discovery of vascular progenitor cells and new molecules that display selective functions in modulating endothelial cell fate, migration and patterning, vessel morphogenesis and the amplification of angiogenic signaling by regulating the master signal VEGF, opens the door to new clinical strategies that target angiogenesis-dependent diseases or that can promote therapeutic neovascularization.

Angiogenesis inhibitors and the need for anti-angiogenic therapeutics

Angiogenesis is the formation of new blood vessels from pre-existing vessels to form capillary networks, which, among other diseases, such as diabetic retinopathy and macular degeneration, is particularly important for tumor growth and metastasis. Thus, depriving a tumor of its vascular supply by means of anti-angiogenic agents has been of great interest since its proposal in the 1970s. This review looks at the common angiogenic inhibitors (angiostatin, endostatin, maspin, pigment epithelium-derived factor, bevacizumab and other monoclonal antibodies, and zoledronic acid) and their current status in clinical trials.

Proteomic analysis of human vitreous fluid by fluorescence-based difference gel electrophoresis (DIGE): a new strategy for identifying potential candidates in the pathogenesis of proliferative diabetic retinopathy

AIMS/HYPOTHESIS

The aim of this study was to compare the protein profile of vitreous fluid from diabetic patients with proliferative diabetic retinopathy (PDR) with that from non-diabetic patients with idiopathic macular holes (MH). The mRNA of proteins differentially produced was also assessed in the retinas from diabetic and non-diabetic donors.

MATERIALS AND METHODS

Vitreous humour from type 1 diabetic patients with PDR (n = 8) and from non-diabetic patients with MH (n = 10) closely matched in terms of age were studied. The comparative proteomic analysis was performed using fluorescence-based difference gel electrophoresis (DIGE). Differentially produced proteins (abundance ratio >1.4, p < 0.05) were identified by mass spectrometry. Expressions of mRNA were measured by real-time RT-PCR in retinas from ten human eyes obtained at post-mortem (five eyes from diabetic subjects and five eyes from non-diabetic subjects).

RESULTS

Eight proteins were highly produced in PDR patients in comparison with non-diabetic subjects: zinc-alpha(2)-glycoprotein (ZAG), apolipoprotein (apo) A1, apoH, fibrinogen A, and the complement factors C3, C4b, C9 and factor B). We found three proteins that were underproduced in PDR subjects: pigment epithelial derived factor (PEDF), interstitial retinol-binding protein (IRBP) and inter-alpha-trypsin inhibitor heavy chain (ITIH2). There was no overlap in the vitreous levels of the above-mentioned proteins between PDR patients and non-diabetic control subjects. The differential production of ZAG, C3, factor B, PEDF and IRBP was further confirmed by western blot, and was in agreement with mRNA levels detected in the retina.

CONCLUSIONS/INTERPRETATION

Proteomic analysis by DIGE, which permits an accurate quantitative comparison, was useful in identifying new potential candidates involved in the pathogenesis of PDR.

Modulation of Ku70/80, Clusterin/ApoJ Isoforms and Bax Expression in Indocyanine-Green-Mediated Photo-Oxidative Cell Damage

PURPOSE

In order to characterize the biological effects and molecular mechanism underlying indocyanine-green (ICG)-mediated photo-oxidative cell damage, human cultured retinal pigmented epithelium (RPE) cells preloaded with ICG were exposed to 810-nm laser irradiation. Cell viability and death induction were examined, as well as the modulation of proteins involved in cell death and DNA repair.

METHODS

ARPE-19 cells preloaded with 100 microM ICG were irradiated using continuous and micropulsed 810-nm laser for the dye photoactivation, and cell viability and apoptosis were evaluated. The expression and subcellular localization of Bax, Ku70, Ku80 and clusterin/ApoJ were analyzed by immunocytochemistry and Western blot.

RESULTS

ICG photoactivation induced apoptosis in RPE cells. The micropulsed laser irradiation induced a higher percentage of cell killing as compared to continuous wave. Cell killing was inhibited by sodium azide, suggesting the involvement of reactive oxygen species in the laser-induced cell damage. Bax was strongly induced after 4 and up to 24 h of treatment. The nuclear proapoptotic isoform of clusterin/ApoJ was selectively upregulated after 24 h of treatment. The DNA repair machinery was upregulated after 4 and up to 24 h.

CONCLUSION

These data elucidate some molecular mechanisms involved in cell death induced by ICG photosensitization. The increase and relocalization of Bax into the mitochondria and the upregulation and translocation of the proapoptotic isoform of clusterin/ApoJ in the nucleus demonstrated the involvement of these proteins in the photo-oxidative cell death pathway. These data point out new molecular targets and suggest potential applications in the therapy of the retinal diseases that could benefit by selective RPE treatment.

Comparison of the modified Early Treatment Diabetic Retinopathy Study and mild macular grid laser photocoagulation strategies for diabetic macular edema

OBJECTIVE

To compare 2 laser photocoagulation techniques for treatment of diabetic macular edema: the modified Early Treatment Diabetic Retinopathy Study (ETDRS) direct/grid photocoagulation technique and a potentially milder (but potentially more extensive) mild macular grid (MMG) laser technique in which microaneurysms are not treated directly and small mild burns are placed throughout the macula, whether or not edema is present.

METHODS

Two hundred sixty-three subjects (mean age, 59 years) with previously untreated diabetic macular edema were randomly assigned to receive laser photocoagulation by either the modified ETDRS (162 eyes) or MMG (161 eyes) technique. Visual acuity, fundus photographs, and optical coherence tomography measurements were obtained at baseline and at 3.5, 8, and 12 months. Treatment was repeated if diabetic macular edema persisted.

MAIN OUTCOME MEASURE

Change in optical coherence tomography measurements at 12-month follow-up.

RESULTS

Among eyes with a baseline central subfield thickness of 250 microm or greater, central subfield thickening decreased by an average of 88 microm in the modified ETDRS group and by 49 microm in the MMG group at 12-month follow-up (adjusted mean difference, 33 microm; 95% confidence interval, 5-61 microm; P = .02). Weighted inner zone thickening by optical coherence tomography decreased by 42 microm in the modified ETDRS group and by 28 microm in the MMG group (adjusted mean difference, 14 microm; 95% confidence interval, 1-27 microm; P = .04); maximum retinal thickening (maximum thickening of the central and 4 inner subfields) decreased by 66 and 39 microm, respectively (adjusted mean difference, 27 microm; 95% confidence interval, 6-47 microm; P = .01), and retinal volume decreased by 0.8 and 0.4 mm3, respectively (adjusted mean difference, 0.3 mm3; 95% confidence interval, 0.02-0.53 mm3; P = .03). At 12 months, the mean change in visual acuity was 0 letters in the modified ETDRS group and 2 letters worse in the MMG group (adjusted mean difference, 2 letters; 95% confidence interval, -0.5 to 5 letters; P = .10).

CONCLUSIONS

At 12 months after treatment, the MMG technique was less effective at reducing optical coherence tomography-measured retinal thickening than the more extensively evaluated current modified ETDRS laser photocoagulation approach. However, the visual acuity outcome with both approaches is not substantially different. Given these findings, a larger long-term trial of the MMG technique is not justified.

APPLICATION TO CLINICAL PRACTICE

Modified ETDRS focal photocoagulation should continue to be a standard approach for treating diabetic macular edema.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00071773.

Ocular neovascularization: Implication of endogenous angiogenic inhibitors and potential therapy

Ocular neovascularization (NV) is the primary cause of blindness in a wide range of ocular diseases, such as diabetic retinopathy (DR) and age-related macular degeneration (AMD). The exact mechanism underlying the pathogenesis of ocular NV is not yet well understood, and as a consequence, there is no satisfactory therapy for ocular NV. In the last 10 years, a number of studies provided increasing evidence demonstrating that the imbalance between angiogenic stimulating factors and angiogenic inhibitors is a major contributor to the angiogenesis induced by various insults, such as hypoxia or ischemia, inflammation and tumor. The angiogenic inhibitors alone or in combination with other existing therapies are, therefore, believed to be promising in the treatment of ocular NV in the near future. This article reviews recent progress in studies on the mechanisms and treatment of ocular NV, focusing on the implication and therapeutic potential of endogenous angiogenic inhibitors in ocular NV.

Vitreous fluid biomarkers

Interactions between cells and the network of secreted proteins are associated with the ocular disease. In most cases, clinical appearcance is sufficiently diagnostic. However, in cases of nonspecific or atypical clinical presentation, diagnostic sampling of vitreous fluid can aid diagnosis and treatment for ocular disease. Progresses in the basic sciences, particularly molecular biology, and advances in surgical instrumentation have greatly enhanced the diagnostic armamentarium. These developments also have led to a better understanding of the pathophysiological processes involved in ocular diseases and have prompted evolution of new therapeutic modalities. In this chapter, we review techniques for vitreous fluid sampling and biomarker quantitation thereof. The molecular biology of bioactive vitreous fluid factors is also discussed with respect to their clinical involvement in the development of ocular disease.

PEDF: a potential molecular therapeutic target with multiple anti-cancer activities

Pigment epithelium-derived factor (PEDF) is an endogenously produced protein that is widely expressed throughout the human body, and exhibits multiple and varied biological activities. Already established as a potent anti-angiogenic molecule, PEDF has recently shown promise as a potential anti-tumour agent, causing both direct and indirect tumour suppression. Here, we explore the unique anti-tumour properties of PEDF and discuss its role as an effective anti-angiogenic, anti-proliferative and pro-differentiation factor. We also discuss the prospects for PEDF therapy and the need for a closer evaluation of issues such as delivery, stability and potential toxicity.

Pigment epithelium-derived factor: a multimodal tumor inhibitor

Pigment epithelium-derived factor (PEDF), a noninhibitory member of the serine protease inhibitor (serpin) family, is a well-known potent endogenous inhibitor of angiogenesis. It has been known for years to be aberrantly expressed in ocular disorders, but in recent years, down-regulation has been shown to be prevalent in a range of cancers as well. This review describes the trimodal anticancer activities of this interesting protein: antiangiogenesis, apoptosis-mediated tumor suppression, and tumor cell differentiation. The key to successful antitumor therapy with this protein is the ability to synthesize the recombinant form of the protein (or its active shortened forms) and deliver at therapeutic doses or alternatively to use gene transfer technology to prolong the effect in vivo. Although there is a substantial amount of work carried out at the preclinical stage with this protein, more groundwork has to be done before PEDF is tested against cancer in clinical trials.

Pigment-Epithelium-Derived Factor Is Upregulated in Photocoagulated Human Retinal Pigment Epithelial Cells

There is much evidence that pigment-epithelium-derived factor (PEDF) is a potent antiangiogenic cytokine which inhibits retinal and choroidal neovascularization by inducing apoptosis in activated vascular endothelial cells. Furthermore, the regulation of PEDF appears to be linked to the regulation of vascular endothelial growth factor (VEGF), one of the most potent inducers of intraocular neovascularization. Previous studies have established that thermal photocoagulation, the mainstay in the therapy of various neovascular diseases of the posterior segment, results in a decrease in intraocular concentrations of VEGF and other angiogenic growth factors, thereby inhibiting active retinal neovascularization. In the current study, we sought to determine whether thermal photocoagulation has the potential to regulate the expression of PEDF in human retinal pigment epithelial (RPE) cells. Cultures of RPE cells were photocoagulated with a 532-nm diode laser. Subsequently, RNA was isolated for RT-PCR, and whole-cell extracts and precipitated cell culture supernatant were subjected to Western blot analysis. According to our results, PEDF mRNA and protein are significantly upregulated after photocoagulation. Moreover, PEDF protein was found to be secreted in the cell culture medium.

Adeno-associated virus-vectored gene therapy for retinal disease

Recombinant adeno-associated viral (AAV) vectors have become powerful gene delivery tools for the treatment of retinal degeneration in a variety of animal models that mimic corresponding human diseases. AAV vectors possess a number of features that render them ideally suited for retinal gene therapy, including a lack of pathogenicity, minimal immunogenicity, and the ability to transduce postmitotic cells in a stable and efficient manner. In the sheltered environment of the retina, AAV vectors are able to maintain high levels of transgene expression in the retinal pigmented epithelium (RPE), photoreceptors, or ganglion cells for long periods of time after a single treatment. Each cell type can be specifically targeted by choosing the appropriate combination of AAV serotype, promoter, and intraocular injection site. The focus of this review is on examples of AAV-mediated gene therapy in those animal models of inherited retinal degeneration caused by mutations directly affecting the interacting unit formed by photoreceptors and the RPE. In each case discussed, expression of the therapeutic gene resulted in significant recovery of retinal structure and/or visual function. Because of the key role of the vasculature in maintaining a healthy retina, a summary of AAV gene therapy applications in animal models of retinal neovascular diseases is also included.

"Light" versus "classic" laser treatment for clinically significant diabetic macular oedema

AIM

To compare the effectiveness of "light" versus "classic" laser photocoagulation in diabetic patients with clinically significant macular oedema (CSMO).

METHODS

A prospective randomised pilot clinical trial in which 29 eyes of 24 diabetic patients with mild to moderate non-proliferative diabetic retinopathy (NPDR) and CSMO were randomised to either "classic" or "light" Nd:YAG 532 nm (frequency doubled) green laser. "Light" laser treatment differed from conventional ("classic") photocoagulation in that the energy employed was the lowest capable to produce barely visible burns at the level of the retinal pigment epithelium. Primary outcome measure was the change in foveal retinal thickness as measured by optical coherence tomography (OCT); secondary outcomes were the reduction/elimination of macular oedema on contact lens biomicroscopy and fluorescein angiography, change in visual acuity, contrast sensitivity, and mean deviation in the central 10 degrees visual field. Examiners were masked to patients' treatment.

RESULTS

14 eyes were assigned to "classic" and 15 were assigned to "light" laser treatment. At 12 months, seven (50%) of 14 eyes treated with "classic" and six (43%) of 14 eyes treated with "light" laser had a decrease of foveal retinal thickness on OCT (p = 0.79). A comparison of reduction/elimination of oedema, visual improvement, visual loss, change in contrast sensitivity, and mean deviation in the central 10 degrees showed no statistical difference between the groups at 12 months (p>0.05 for all groups).

CONCLUSIONS

This study suggests that "light" photocoagulation for CSMO may be as effective as "classic" laser treatment, thus supporting the rationale for a larger equivalence trial.

Pigment Epithelium Endoscopic Laser Surgery for Treatment of Choroidal Neovascularization

PURPOSE

To present a new concept and technique for subretinal surgery.

METHODS

Twenty-four eyes of 24 patients with subfoveal choroidal neovascularization (CNV) were included in this study. Nine patients were operated on in Mexico City by one surgeon, 15 patients in Frankfurt by another surgeon. The retina at the posterior pole was detached and subretinal thermal photocoagulation of the CNVs was performed using a 20/19-gauge GRIN rod laser endoscope (Insight Instruments Inc., Sanford, Fla., USA). This procedure was termed PEELS (pigment epithelium endoscopic laser surgery).

RESULTS

In 7 patients (Mexico), moderate improvement or stabilization of vision over 6 months or longer was achieved. In 10 out of 12 patients (Frankfurt), stabilization of vision over a follow-up period of 6-18 months was achieved, at least. Serious complications were not observed. Four of the Frankfurt series patients improved their vision.

CONCLUSION

PEELS can stabilize or improve vision.

Pharmacologic therapy for diabetic retinopathy

Diabetic retinopathy remains one of the major causes of acquired blindness in developed nations. This is true despite the development of laser treatment, which can prevent blindness in the majority of those who develop macular oedema (ME) or proliferative diabetic retinopathy (PDR). ME is manifest by retinal vascular leakage and thickening of the retina. The hallmark of PDR is neovascularisation (NV)--abnormal angiogenesis that may ultimately cause severe vitreous cavity bleeding and/or retinal detachment. Pharmacologic therapy aimed specifically at preventing vascular leakage and NV would be a welcome addition to the armamentarium. PDR and ME could be prevented by improved metabolic control or by pharmacologically blunting the biochemical consequences of hyperglycaemia (e.g., with aldose reductase inhibitors, inhibitors of non-enzymatic glycation or by protein kinase C [PKC] inhibition). The angiogenesis in PDR could be treated via growth factor (e.g., vascular endothelial growth factor [VEGF], insulin like growth factor-1 [IGF-1]) blockade, integrin (e.g., alpha-v beta-3) blockade, extracellular matrix alteration (e.g., with steroid compounds) or interference with intracellular signal transduction pathways (e.g., PKC and mitogen activated protein kinase [MAPK] pathway proteins). Some of these antiangiogenic agents may also prove useful for treating or preventing ME. Numerous potentially useful antiangiogenic compounds are in development; two drugs are presently in clinical trials for treatment of the preproliferative stage of PDR, while two are in clinical trials for treatment of ME.

Expression of pigment epithelium-derived factor (PEDF) and vascular endothelial growth factor (VEGF) in sickle cell retina and choroid

Pigment epithelium-derived factor (PEDF) has been shown to be an inhibitor of angiogenesis as well as a multipotent neurotrophic factor in the mammalian eye. Changes in PEDF levels have been correlated with development of retinal neovascularization in oxygen-induced retinopathy. The purpose of this study was to determine the localization and relative level of PEDF in human retinas and choroids using immunohistochemistry and evaluate the changes in PEDF and vascular endothelial growth factor (VEGF) localization and their relation to the progression of proliferative sickle cell retinopathy. Cryopreserved tissues from eyes of normal subjects and subjects with non-proliferative or proliferative sickle cell retinopathy were used with streptavidin peroxidase immunohistochemistry. A rabbit polyclonal antibody was made against recombinant human PEDF. Binding of the antibody was blocked by preincubation of the antibody with excess human recombinant PEDF. Relative levels of immunoreactivity were scored with a seven-point grading system and by microdensitometric analysis.The most prominent sites of PEDF localization in the normal eye were the vitreous condensed at the internal limiting membrane and RPE-Bruch's membrane-choriocapillaris complex. PEDF was also prominent in choroidal stroma. There was limited immunoreactivity in some cells of the neural retinas, in blood vessels and in the interphotoreceptor matrix (IPM). There was no difference in ratio (1.47 vs. 1.44) of PEDF/VEGF or the relative levels of either growth factor in the retinal vasculatures of the control subjects and perfused area of non-proliferative sickle cell retinas. The ratio was increased in the non-perfused area of the non-proliferative sickle cell retinas (2.24). In eyes with proliferative sickle cell retinopathy, elevated PEDF and VEGF immunostaining was present in viable vessels of sea fan neovascular formations as well as feeder vessels of sea fans. The PEDF/VEGF ratio in sea fans was 1.0. Immunoreactivity for PEDF was prominent in retinal vessels in non-perfused regions and in atrophic sea fans, while VEGF immunoreactivity was weak or absent in these structures. In conclusion, PEDF and VEGF were both significantly elevated in viable sea fan formations in sickle cell disease (p<0.05) but only PEDF was present in non-viable sea fans. The highest levels of PEDF in all eyes were associated with extracellular matrices (vitreous, choroidal stroma, IPM, and walls of blood vessels). PEDF might play an important role in inhibiting angiogenesis and inducing the regression of sea fans. Progression of angiogenesis may be dependent on the ratio of PEDF/VEGF.