Angiogenic factors in human proliferative sickle cell retinopathy

Sickle Eye Project: a cross-sectional, non-interventional study of the prevalence of visual impairment due to sickle cell retinopathy and maculopathy in the UK

INTRODUCTION

Sickle cell disease (SCD) is one of the most common genetic disorders in the UK, with over 15 000 people affected. Proliferative sickle cell retinopathy (SCR) is a well-described complication of SCD and can result in significant sight loss, although the prevalence in the UK is not currently known. There are currently no national screening guidelines for SCR, with wide variations in the management of the condition across the UK.

METHODS AND ANALYSIS

The Sickle Eye Project is an epidemiological, cross-sectional, non-interventional study to determine the prevalence of visual impairment due to SCR and/or maculopathy in the UK. Haematologists in at least 16 geographically dispersed hospitals in the UK linked to participating eye clinics will offer study participation to consecutive patients meeting the inclusion criteria attending the sickle cell clinic. The following study procedures will be performed: (a) best corrected visual acuity with habitual correction and pinhole, (b) dilated slit lamp biomicroscopy and funduscopy, (c) optical coherence tomography (OCT), (d) OCT angiography where available, (e) ultrawide fundus photography, (f) National Eye Institute Visual Function Questionnaire-25 and (g) acceptability of retinal screening questionnaire. The primary outcome is the proportion of people with SCD with visual impairment defined as logarithm of the minimum angle of resolution ≥0.3 in at least one eye. Secondary outcomes include the prevalence of each stage of SCR and presence of maculopathy by age and genotype; correlation of stage of SCR and maculopathy to severity of SCD; the impact of SCR and presence of maculopathy on vision-related quality of life; and the acceptability to patients of routine retinal imaging for SCR and maculopathy.

ETHICS AND DISSEMINATION

Ethical approval was obtained from the South Central-Oxford A Research Ethics Committee (REC 23/SC/0363). Findings will be reported through academic journals in ophthalmology and haematology.

Comparative transcriptome analysis of endothelial progenitor cells of HbSS patients with and without proliferative retinopathy

Among sickle cell anemia (SCA) complications, proliferative sickle cell retinopathy (PSCR) is one of the most important, being responsible for visual impairment in 10-20% of affected eyes. The aim of this study was to identify differentially expressed genes (DEGs) present in pathways that may be implicated in the pathophysiology of PSCR from the transcriptome profile analysis of endothelial progenitor cells. RNA-Seq was used to compare gene expression profile of circulating endothelial colony-forming cells (ECFCs) from HbSS patients with and without PSCR. Furthermore, functional enrichment analysis and protein-protein interaction (PPI) networks were performed to gain further insights into biological functions. The differential expression analysis identified 501 DEGs, when comparing the groups with and without PSCR. Furthermore, functional enrichment analysis showed associations of the DEGs in 200 biological processes. Among these, regulation of mitogen-activated protein (MAP) kinase activity, positive regulation of phosphatidylinositol 3-kinase (PI3K), and positive regulation of Signal Transducer and Activator of Transcription (STAT) receptor signaling pathway were observed. These pathways are associated with angiogenesis, cell migration, adhesion, differentiation, and proliferation, important processes involved in PSCR pathophysiology. Moreover, our results showed an over-expression of VEGFC (vascular endothelial growth factor-C) and FLT1 (Fms-Related Receptor Tyrosine Kinase 1) genes, when comparing HbSS patients with and without PSCR. These results may indicate a possible association between VEGFC and FLT1 receptor, which may activate signaling pathways such as PI3K/AKT and MAPK/ERK and contribute to the mechanisms implicated in neovascularization. Thus, our findings contain preliminary results that may guide future studies in the field, since the molecular mechanisms of PSCR are still poorly understood.

Comparison of Ultra-Wide Field Photography to Ultra-Wide Field Angiography for the Staging of Sickle Cell Retinopathy

Sickle cell retinopathy (SCR) is classified by Goldberg based on peripheral vascular changes. Ultra-wide field (UWF) imaging has enhanced visualization of the peripheral retina. However, there is no consensus on the optimal imaging technique for the screening of SCR. We performed a monocentric observational cross-sectional study to compare UWF fundus photography (UWF-FP) with UWF angiography (UWF-FA). All patients who underwent UWF-imaging (Optos, PLC, Scotland, UK) for screening of sickle cell retinopathy between January 2016 and December 2019 were retrospectively included. Eyes with previous laser treatment or concomitant retinal disease were excluded. UWF-FP images were graded based on the Goldberg classification by four graders with various degrees of experience. UWF-FA pictures were reviewed by an independent retina specialist. Differences in Goldberg staging across UWF-FP and UWF-FA were assessed. A total of 84 eyes of 44 patients were included. Based on UWF-FA, most eyes were stage 2 (77.4%) and 19 were stage 3 (22.6%). The pre-retinal neovascularization detection sensitivity on UWF-FP was 52.6 to 78.9%, depending on the graders. UWF-FA led to a later Goldberg stage of retinopathy, in most cases from stage 1 to stage 2. Neovascularization (stage 3) was not detected by our graders on UWF-FP in 21.1 to 57.9% of eyes. UWP-FP tends to underestimate Goldberg stages of retinopathy compared with UWF-FA and is less accurate when detecting neovascularization in sickle cell retinopathy, which has a direct impact on therapeutic management and prognosis.

Monitoring retinal pathology and cerebral injury in sickle cell disease using spectral-domain optical coherence tomography in pediatric patients

PURPOSE

This study aimed to confirm the correlation between sickle cell disease (SCD) genotype and retinal damage identified by spectral-domain optical coherence tomography (SD-OCT), and examine a potential link between hypoxic ischemic injury in the retina and brain.

METHODS

In this prospective, observational case series, 117 patients (56 males) aged 5-20 years with SCD (36 SC, 68 SS, eight Sβ+ thalassemia, five Sβ0 thalassemia) underwent ophthalmologic examination including funduscopy and SD-OCT imaging. Comparison of SCD genotypes and association between ocular findings and cerebrovascular disease (CVD) in subjects with SS/Sβ0 genotype were investigated.

RESULTS

Visual acuity ranged from 20/20 to 20/40. On funduscopic exam, 16 of 117 (13.7%) had retinopathy; 69 of 117 (59.0%) showed inner retina thinning on SD-OCT. Patients with SS/Sβ0 showed a higher frequency of sickle cell retinopathy (SCR) change (68.5% vs. 47.2%), bilateral SCR (49.9% vs. 25.0%), and foveal involvement (15.1% vs. 0) than the SC genotype. While funduscopic findings in our cohort with SS/Sβ0 genotype showed no correlation with CVD, 20 of 21 patients with CVD had abnormal SD-OCT. Elevated reticulocyte percentage and aspartate aminotransferase are associated with SD-OCT changes and CVD.

CONCLUSIONS

SD-OCT was better than funduscopy in detecting retinal changes, higher frequency, and more extensive retinal changes in the more severe SCD genotypes SS and Sβ0 as compared with SC. The correlation between abnormal SD-OCT and CVD strongly suggests that retinal exam using SD-OCT may aid in detection and monitoring SCD-related CVD. Retinopathy may be another component of the hemolytic subphenotype of SCD.

Sickle Cell Anemia Patients Display an Intricate Cellular and Serum Biomarker Network Highlighted by TCD4+CD69+ Lymphocytes, IL-17/MIP-1β, IL-12/VEGF, and IL-10/IP-10 Axis

BACKGROUND

Sickle cell anemia (SCA) is associated with a chronic proinflammatory state characterized by elevated leukocyte count, mortality from severe recurrent infections, and subsequent vasoocclusive complications with leukocyte adhesion to the endothelium and increased plasma levels of inflammatory cytokines. The immune system has a close connection with morbidity in SCA, but further studies are needed to uncover the involvement of innate and adaptive immunities in modulating the SCA physiopathology. We performed measurements of the frequency of innate and adaptive immunity cells, cytokines, chemokines, and growth factors and immunophenotyping of Toll-like receptor and adhesion molecule expression in the blood of SCA patients and healthy donors to evaluate the different profiles of these biomarkers, the relationship among them, and their correlation to laboratory records and death risk. Material and Methods. Immunophenotyping of cells, Toll-like receptors, and adhesion molecules were performed from peripheral blood samples of SCA patients and healthy donors by flow cytometry and cytokine/chemokine/growth factor measurement by the Luminex technique performed from the serum of the same subjects.

RESULTS

Cells of adaptive immunity such as IL-12, IL-17, and IL-10 cytokines; IL-8, IP-10, MIP-1α, MIP-1β, and RANTES chemokines; and VEGF, FGF-basic, and GM-CSF growth factors were higher in SCA patients than healthy donors regardless of any laboratorial and clinical condition. However, high death risk appears to have relevant biomarkers.

CONCLUSION

In the SCA pathophysiology at steady state, there is a broad immunological biomarker crosstalk highlighted by TCD4+CD69+ lymphocytes, IL-12 and IL-17 inflammatory and IL-10 regulatory cytokines, MIP-1α, MIP-1β, and IP-10 chemokines, and VEGF growth factor. High expression of TLR2 in monocytes and VLA-4 in TCD8+ lymphocytes and high levels of MIP-1β and RANTES appear to be relevant in high death risk conditions. The high reticulocytosis and high death risk conditions present common correlations, and there seems to be a balance by the Th2 profile.

Wide-field imaging of sickle retinopathy

Background

Wide-field imaging is a newer retinal imaging technology, capturing up to 200 degrees of the retina in a single photograph. Individuals with sickle cell retinopathy commonly exhibit peripheral retinal ischemia. Patients with proliferative sickle cell retinopathy develop pathologic retinal neovascularization of the peripheral retina which may progress into sight-threatening sequelae of vitreous hemorrhage and/or retinal detachment. The purpose of this review is to provide an overview of current and future applications of wide-field retinal imaging for sickle cell retinopathy, and recommend indications for best use.

Main body

There are several advantages to wide-field imaging in the clinical management of sickle cell disease patients. Retrospective and prospective studies support the success of wide-field imaging in detecting more sickle cell induced retinal microvascular abnormalities than traditional non-wide-field imaging. Clinicians can easily capture a greater extent of the retinal periphery in a patient's clinical baseline imaging to follow the changes at an earlier point and determine the rate of progression over time. Wide-field imaging minimizes patient and photographer burden, necessitating less photos and technical skill to capture the peripheral retina. Minimizing the number of necessary images can be especially helpful for pediatric patients with sickle cell retinopathy. Wide-field imaging has already been successful in identifying new biomarkers and risk factors for the development of proliferative sickle cell retinopathy. While these advantages should be considered, clinicians need to perform a careful risk-benefit analysis before ordering this test. Although wide-field fluorescein angiography successfully detects additional pathologic abnormalities compared to traditional imaging, a recent research study suggests that peripheral changes differentially detected by wide-field imaging may not change clinical management for most sickle cell patients.

Conclusions

While wide-field imaging may not carry a clinically significant direct benefit to all patients, it shows future promise in expanding our knowledge of sickle cell retinopathy. Clinicians may monitor peripheral retinal pathology such as retinal ischemia and retinal neovascularization over progressive time points, and use sequential wide-field retinal images to monitor response to treatment. Future applications for wide-field imaging may include providing data to facilitate machine learning, and potential use in tele-ophthalmology screening for proliferative sickle retinopathy.

Sickle cell disease: Clinical presentation and management of a global health challenge

Sickle cell disease is an autosomal recessive, multisystem disorder, characterised by chronic haemolytic anaemia, painful episodes of vaso-occlusion, progressive organ failure and a reduced life expectancy. Sickle cell disease is the most common monogenetic disease, with millions affected worldwide. In well-resourced countries, comprehensive care programs have increased life expectancy of sickle cell disease patients, with almost all infants surviving into adulthood. Therapeutic options for sickle cell disease patients are however, still scarce. Predictors of sickle cell disease severity and a better understanding of pathophysiology and (epi)genetic modifiers are warranted and could lead to more precise management and treatment. This review provides an extensive summary of the pathophysiology and management of sickle cell disease and encompasses the characteristics, complications and current and future treatment options of the disease.

The past, present and future management of sickle cell retinopathy within an African context

Sickle cell retinopathy is a potentially blinding condition that affects young people in the working age group. This review looks at the past, present and future management of sickle cell retinopathy within an African context. After Sickle cell disease was first reported in 1910, some reports from Africa were pivotal in describing the retinal changes associated with the disease. It soon became obvious that there was a varied clinical picture and clinical course. Several landmark studies were carried out in Jamaica to help elucidate the complexities of the disease and outline appropriate clinical management. In most of the developed world, the clinical management of sickle cell disease has improved with concurrent improvement in outcomes. Currently resource constraints in most Sub-Saharan African countries where there is a high burden of disease means that the management of sickle cell retinopathy is fraught with numerous challenges. Future large scale trials in Africa shall hopefully help to better elucidate the mechanisms behind proliferative sickle retinopathy and help in the development of new and improved therapeutic pathways. The use of technology can help immensely in the screening of patients with sickle cell to detect early proliferative changes and if necessary treat accordingly.

Funduscopic examination and SD-OCT in detecting sickle cell retinopathy among pediatric patients

PURPOSE

To compare the results of fundus examination and spectral domain optic coherence tomography (SD-OCT) in detecting retinal changes in pediatric patients with sickle cell disease at a single center.

METHODS

In this prospective study, conducted over a period of 19 months, consecutive African American patients with sickle cell disease underwent complete ophthalmologic examination, and SD-OCT images of the maculas of both eyes were obtained.

RESULTS

A total of 69 (37 males) patients aged 5-20 years (mean 12.89 ± 4.09; range, 2-20) with sickle cell disease (SC, 26; SS, 36; Sβ+, 5; Sβ0 thalassemia, 2) were examined. Patients' visual acuity range was 20/20 to 20/40. On funduscopic examination, 11 of 69 showed signs of retinopathy, whereas 47 of 68 showed inner retina thinning in the watershed zone temporal to the fovea on SD-OCT. On average, SD-OCT diagnosed disease 1.78 years earlier than fundus examination. Of patients <10 years of age, 1 was diagnosed with retinopathy by funduscopy, whereas retinal changes were evident on SD-OCT in 12 of 22. Fundus examination showed no significant difference in retinal findings between SS/Sβ0 and SC genotypes. On SD-OCT, SS/Sβ0 showed worse disease process than SC in frequency of diagnosis (82% vs 56%), bilateral involvement (87% vs 43%), and foveal involvement (18% vs 0).

CONCLUSIONS

The peripheral retina could be visualized on fundus examination but not easily imaged on SD-OCT, which, however, had a higher detection rate and offered earlier diagnosis. In our patient cohort SD-OCT showed that the severity of retinal change was associated with more severe sickle cell disease genotypes (SS and Sβ0).

Sickle cell retinopathy: A literature review

Hemoglobinopathies are a group of hereditary diseases that cause quantitative or qualitative changes in the shape, function or synthesis of hemoglobin. One of the most common is sickle cell anemia, which, due to sickling of erythrocytes, causes vaso-occlusive phenomena. Among the possible ocular manifestations, the most representative is retinopathy, which can lead to blindness if left untreated. Therefore, periodic ophthalmologic monitoring of these patients is important for early diagnosis and adequate therapeutic management, which can be done localy by treating the lesions in the eyes, or systemically.

Ocular Histopathology and Immunohistochemical Analysis in the Oldest Known Individual with Autosomal Dominant Vitreoretinochoroidopathy

PURPOSE

To assess the immunohistochemical and histopathological changes in a subject with Autosomal Dominant Vitreoretinochoroidopathy (ADVIRC).

DESIGN

Case study.

PARTICIPANT

Ninety two year-old Caucasian male with ADVIRC.

METHODS

The subject was documented clinically for 54 Years. The retina/choroid complex of the right eye was evaluated with cryosections stained with hematoxylin and eosin or periodic acid schiff reagent. Cryosections were also evaluated with immunofluorescence or alkaline phosphatase immunohistochemistry (IHC) using primary antibodies against bestrophin1, GFAP, PEDF, RPE65, TGFβ, VEGF, and vimentin. The left retina and choroid were evaluated as flat mounts using immunofluorescence. UEA lectin was used to stain viable vasculature.

MAIN OUTCOME MEASURES

The immunohistochemical and histopathological changes in retina and choroid from a subject with ADVIRC.

RESULTS

The subject had a heterozygous c.248G>A variant in exon 4 of the BEST1 gene. There was widespread chorioretinal degeneration and atrophy except for an island of spared RPE monolayer in the perimacula/macula OU. In this region, some photoreceptors were present, choriocapillaris was spared, and retinal pigment epithelial cells were in their normal disposition. There was a Muller cell periretinal membrane throughout much of the fundus. Bestrophin-1 was not detected or only minimally present by IHC in the ADVIRC RPE, even in the spared RPE area. Beyond the island of retained RPE monolayer on Bruch's membrane (BrMb), there was migration of RPE into the neuro-retina, often ensheathing blood vessels and producing excessive matrix within their perivascular aggregations.

CONCLUSIONS

The primary defect in ADVIRC is in RPE, the only cells in the eye that express the BEST1 gene. The dysfunctional RPE cells may go through epithelial/mesenchymal transition as they migrate from BrMb to form papillary aggregations in the neuro-retina, often ensheathing blood vessels. This may be the reason for retinal blood vessel nonperfusion. Migration of RPE from BrMb was also associated with attenuation of the choriocapillaris.

New Ways to Detect Pediatric Sickle Cell Retinopathy: A Comprehensive Review

Sickle retinopathy reflects disease-related vascular injury of the eye, which can potentially result in visual loss from vitreous hemorrhage or retinal detachment. Here we review sickle retinopathy among children with sickle cell disease, describe the epidemiology, pediatric risk factors, pathophysiology, ocular findings, and treatment. Newer, more sensitive ophthalmological imaging modalities are available for retinal imaging, including ultra-widefield fluorescein angiography, spectral-domain optical coherence tomography, and optical coherence tomography angiography. Optical coherence tomography angiography provides a noninvasive view of retinal vascular layers that could previously not be imaged and can be quantified for comparative or prospective analyses. Ultra-widefield fluorescein angiography provides a more comprehensive view of the peripheral retina than traditional imaging techniques. Screening for retinopathy by standard fundoscopic imaging modalities detects a prevalence of approximately 10%. In contrast, these more sensitive methods allow for more sensitive examination that includes the retina perimeter where sickle retinopathy is often first detectable. Use of these new imaging modalities may detect a higher prevalence of early sickle pathology among children than has previously been reported. Earlier detection may help in better understanding the pathogenesis of sickle retinopathy and guide future screening and treatment paradigms.

Expression Pattern of HIF-1α and VEGF Supports Circumferential Application of Scatter Laser for Proliferative Sickle Retinopathy

Purpose

Retinal vascular occlusions in sickle cell anemia patients cause tissue ischemia and the release of angiogenic mediators that promote the development of retinal neovascularization, initiating proliferative sickle retinopathy (PSR). Laser photocoagulation (LPC) has emerged as the most common treatment for PSR. Nonetheless, only two randomized controlled clinical trials have evaluated the use of LPC for PSR, and both failed to definitively demonstrate efficacy of this approach. This may be due to a lack of knowledge regarding the appropriate location for placement of laser coagulations in PSR eyes. To help address this question, we examined the expression of hypoxia-inducible factor (HIF)-1α and vascular endothelial growth factor (VEGF) in PSR eyes.

Methods

The expression pattern of HIF-1α and VEGF in PSR (n = 5) and control (n = 3) eyes was examined by immunohistochemistry in different retinal regions defined by the presence or absence of retinal vessels.

Results

Hypoxia-inducible factor 1α and VEGF were expressed in the inner retina of 5/5 untreated PSR eyes adjacent to retinal neovascularization; expression of HIF-1α was not detected (and VEGF only lightly detected) in normal retinal and choroidal vasculature of 3/3 control eyes. Hypoxia-inducible factor 1α and VEGF were strongly expressed in retinal cells within avascular (nonperfused) retina, anterior to the boundary between perfused and nonperfused retina, as well as in posterior ischemic retina in the presence or absence of neovascular sea fans.

Conclusions

If the goal of LPC in PSR is to quench the expression of HIF-1–driven angiogenic mediators, our results support broad application of peripheral laser for its treatment.

[Fortuitous detection of composite heterozygous S/C sickle cell disease]

Le syndrome drépanocytaire composite SC représente 20% à 30% des syndromes drépanocytaires majeurs. Nous rapportons le cas d'une découverte fortuite d'une drépanocytose hétérozygote composite SC dans un contexte de décollement rétinien. Il s'agit d'une patiente hospitalisée au service d'ophtalmologie pour une baisse de l'acuité visuelle détectée depuis 06 mois et rebelle au traitement. Les antécédents cliniques sont dominés par la mise en place d'une prothèse totale de la hanche (PTH) douze ans auparavant. Notre observation rappelle la grande variabilité clinique de la maladie drépanocytaire imposant un dépistage précoce des patients à risque avec une surveillance clinique adaptée afin d'éviter l'évolution vers des séquelles organiques irréversibles telles que la rétinopathie drépanocytaire.

Bevacizumab presurgical treatment for proliferative sickle-cell retinopathy-related retinal detachment

PURPOSE

To report the use of presurgical intravitreal bevacizumab in the context of proliferative sickle-cell retinopathy with retinal detachment.

METHODS

Intravitreal bevacizumab was injected 3 days before the surgical procedure for traction retinal detachment. Vitrectomy, membrane peeling, endolaser, and SF6 gas tamponade were performed. A 37-year-old African American woman presented with hemoglobin sickle-cell disease and temporal retinal detachment with bullous subretinal fluid extending through the fovea associated with an area of active sea-fan retinal neovascularization with preretinal hemorrhage and retinal traction, with 3 associated retinal breaks.

RESULTS

The sea-fan neovascularization associated with the traction retinal detachment and the resultant retinal breaks appeared more fibrotic and les vascular than was noted prior to the pre-operative bevacizumab injection. Segmentation and dissection were performed with minimal bleeding, and retinal traction was relieved without difficulty. This was believed to be atypical in the experience of the surgeons. One month postoperatively, vision measured 20/50, and the retina remained attached.

CONCLUSION

Further study is necessary to clarify the role of anti-vascular endothelial growth factor in the treatment of proliferative sickle cell retinopathy associated retinal detachment.

Peripheral sea-fan retinal neovascularization as a manifestation of chronic rhegmatogenous retinal detachment and surgical management

Background

To report the rare occurrence of peripheral retinal sea-fan neovascularization in a patient with chronic rhegmatogenous retinal detachment and describe the surgical management.

Case presentation

A 29-year-old female patient was referred to our department by her ophthalmologist for investigation and treatment of peripheral retinal neovascularization in her right eye(RE). Visual acuity(VA) at presentation was 20/200 RE and 20/20 LE. Fundoscopy of the RE revealed a chronic inferotemporal retinal detachment and peripheral neovascularization with a sea fan configuration. Fundoscopy of the LE was without any findings. Fluorescein angiography confirmed the sea fan neovascularization in the RE with leakage of the newly formed vessels and peripheral ischemia while the LE did not demonstrate any neovascularization angiographically. Family history was negative for retinitis pigmentosa and haemoglobinopathies. Patient underwent full blood count and haemoglobin electrophoresis to exclude thrombocytosis and sickle cell anaemia, and serum angiotensin-converting enzyme (SACE) measurement to exclude sarcoidosis. Examination with scleral indentation of the RE revealed 2 peripheral small retinal holes close to the ora serrata . The patient underwent a scleral buckling procedure with a small segmental buckle limited to the area of the holes and cryotherapy. Ccryotherapy was not applied to the area with neovascularization and no subretinal fluid drainage was performed. The detached retina was successfully re-attached surgically and the subretinal fluid was gradually absorbed within three months from the time of surgery. Complete regression of neovascularization was evident 2 months postoperatively and VA improved to 20/30. Three years later the clinical and functional findings remain unchanged.

Conclusion

Our case illustrates the rare but possible association of chronic retinal detachment with peripheral retinal sea-fan neovascularization; although the incidence is rare it may pose diagnostic and treatment dilemmas. In such cases and in the presence of retinal breaks, cryotherapy and a segmental buckle limited to the retinal holes and not on the neovascularization seems to suffice for the regression of the new vessels.

Increased circulating PEDF and low sICAM-1 are associated with sickle cell retinopathy

Sickle cell retinopathy (SCR) develops in up to 30% of sickle cell disease patients (SCD) during the second decade of life. Treatment for this affection remains palliative, so studies on its pathophysiology may contribute to the future development of novel therapies. SCR is more frequently observed in hemoglobin SC disease and derives from vaso-occlusion in the microvasculature of the retina leading to neovascularization and, eventually, to blindness. Circulating inflammatory cytokines, angiogenic factors, and their interaction may contribute to the pathophysiology of this complication. Angiopoietin (Ang)-1, Ang-2, soluble vascular cell adhesion molecule-1, intercellular adhesion molecule (ICAM)-1, E-selectin, P-selectin, IL1-β, TNF-α, pigment epithelium derived factor (PEDF) and vascular endothelial growth factor plasmatic levels were determined in 37 SCD patients with retinopathy, 34 without retinopathy, and healthy controls. We observed that sICAM-1 is significantly decreased, whereas PEDF is elevated in HbSC patients with retinopathy (P=0.012 and P=0.031, respectively). Ang-1, Ang-2 and IL1-β levels were elevated in SCD patients (P=0.001, P<0.001 and P=0.001, respectively), compared to controls, and HbSS patients presented higher levels of Ang-2 compared to HbSC (P<0.001). Our study supports the possible influence of sICAM-1 and PEDF on the pathophysiology of retinal neovascularization in SCD patients.

Assessment of gelatinase and tumor necrosis factor-α level in the vitreous and serum of patients with Eales disease: role of inflammation-mediated angiogenesis in the pathogenesis of Eales disease

BACKGROUND

Eales disease (ED) is an idiopathic, inflammatory, venoocclusive disorder of peripheral retina resulting in retinal angiogenesis and vitreous hemorrhage. The objective of the present study is to investigate the expression and activation of gelatinase associated with the retinal neovascularization in ED and the relation between the levels of gelatinase and the cytokine tumor necrosis factor-α, known to upregulate matrix metalloproteinase (MMP) expression on various cells.

METHODS

Vitreous and serum samples from 19 patients with ED who underwent retinal surgery were estimated for levels of MMP-2, MMP-9, tissue inhibitor of metalloproteinase-1, tissue inhibitor of metalloproteinase-2, and tumor necrosis factor-α by enzyme-linked immunosorbent assay method. Matrix metalloproteinase-2 and MMP-9 activities in serum and vitreous samples were evaluated by gelatin zymography method. Vitreous samples from 16 patients with macular hole undergoing vitrectomy were used as controls.

RESULTS

Among the 2 gelatinase examined in vitreous and serum samples, only level and activity of MMP-9 were significantly higher in serum (P = 0.0001) and vitreous (P = 0.0002) samples of patients with ED than those of control subjects. Simultaneously, a positive correlation was found between intraocular tumor necrosis factor-α and MMP-9 concentration (Spearman correlation coefficient, r = 0.7040, P = 0.0023) in patients with ED.

CONCLUSION

Increase in MMP-9 activity and its concentration in serum and vitreous of patients with ED compared with that of control subjects and correlation between intraocular levels of MMP-9 and tumor necrosis factor-α in patients with ED seem to provide a plausible explanation for inflammation-mediated angiogenesis during the development of this condition.

Effect of VEGF trap on normal retinal vascular development and oxygen-induced retinopathy in the dog

Purpose. To evaluate the effects of a vascular endothelial growth factor trap (VEGF Trap) on retinal vascular development and pathologic neovascularization (NV) in the canine model of oxygen-induced retinopathy (OIR). Methods. Newborn dogs (postnatal day [P]1) were exposed to 100% O(2) and then returned to room air on P5. VEGF Trap (5, 25, or 250 μg) was injected intravitreally in one eye and human FC (hFc) injected in the fellow eye of air control and oxygen-treated dogs on P8. The retinal vasculature and NV were evaluated on P21. Other oxygen-exposed animals received 5 μg of VEGF Trap or hFc on P22 after confirmation of retinopathy of prematurity (ROP)-like pathology and were evaluated at P45. Results. In air controls, both the vascularized area of the retina and the density of superficial capillaries were reduced in 250 or 25 μg VEGF Trap-injected eyes, and deep capillaries were absent. Eyes that received the 5 μg dose were indistinguishable from controls. In oxygen-treated animals, all eyes injected with VEGF Trap exhibited markedly less intravitreal NV than that of hFc-injected fellow eyes, irrespective of dose. Retinal vascular area in OIR animals was significantly reduced in eyes injected with 250 or 25 μg of VEGF Trap, but the 5 μg dose did not inhibit retinal revascularization. Eyes with existing NV that received 5 μg VEGF Trap at P22 exhibited substantial resolution of OIR pathology at P45. Conclusions. The VEGF Trap inhibited the formation of NV, but higher doses also inhibited revascularization of retina when injected at P8. In contrast, the lowest dose tested effectively blocked NV and caused regression of existing NV, without appreciably affecting vasculogenesis or retinal revascularization. These findings suggest that dose selection is an important variable when considering the use of VEGF-targeting agents for the treatment of ROP.

Elevated endothelial progenitor cells during painful sickle cell crisis

OBJECTIVE

Circulating endothelial progenitor cells (EPCs) counts were determined in patients with sickle cell disease (SCD) to elucidate their role in SCD-related ischemia-induced angiogenesis and reendothelialization.

MATERIALS AND METHODS

Circulating EPC counts (KDR(+)/CD34(+)/Cd45(dim) cells) and their relation to serum levels of EPC mobilizing growth factors erythropoietin, vascular endothelial growth factor, and interleukin-8 were investigated in SCD patients during asymptomatic state (n=66) and painful crisis (n=36) and compared to healthy controls (n=13).

RESULTS

EPC counts were comparable between controls (0; range, 0-1.1 cells/mL) and patients (0; range, 0-0 cells/mL) in asymptomatic state, but were significantly higher during painful crisis (41.7; range, 0-186 cells/mL; p<0.05). Also in a paired analysis of 12 patients who were included both during asymptomatic state and painful crisis, EPC counts increased significantly during painful crisis (from 0 [range, 0-0] to 26 [range, 0-149 cell/mL; p<0.05). EPC counts were not related to any of the measured growth factors.

CONCLUSION

The higher EPC counts during painful crisis might indicate a role for EPC mobilization in reendothelialization. As a relationship of EPCs with the established mobilizing growth factors, measured in this study was not observed, the mechanism of EPC mobilization in SCD remains to be elucidated.

[Epidemiology and prognostic factors for sickle cell retinopathy in Ouagadougou (Burkina Faso)]

INTRODUCTION

The frequency of sickle cell disease varies from 5% to 20% in Africa.

PATIENTS AND METHOD

This retrospective study investigated 173 patients in an ambulatory setting from August 2000 to July 2006. The study included 98 women and 75 men, aged 15-62 years, with a mean age of 26.7 years.

RESULTS

Only 89 patients (71 SC and 18 SS) were seen in ophthalmology, 44 (49%) had sickle cell retinopathy with 26 (29%) cases nonproliferative and 18 cases proliferative (20%). Among the 71 SC patients, 35 (50%) had sickle cell retinopathy, with 40% the proliferative form. Of the 18 SS patients, nine had a retinopathy (50%), with four cases proliferative.

DISCUSSION

Retinopathy is a frequent complication of sickle cell disease, which can lead to blindness, and its management better accessibility to the ophthalmologic examination and preventive treatment by laser photo coagulation.

Canine retinal angioblasts are multipotent

The purpose of this study was to culture and characterize endothelial cells and angioblasts, vascular precursors, from adult and neonatal dog retina and determine if angioblasts are committed to endothelial cell lineage or have the potential to be multipotent, i.e. express phenotypic characteristics of other vascular cell types. Endothelial cells were established from adult dog retina (ADREC) by the technique of Gitlin and D'Amore. For angioblasts, pieces of neonatal day 2 (P2) avascular peripheral retina were placed under coverslips until sufficient cells had explanted. All cells were maintained initially on hyaluronic acid (HA)/fibronectin (FN) substratum. Neonatal canine retinal angioblasts (NCRA) were maintained initially on retinal-derived growth factor with alpha-amino adipic acid to inhibit growth of Muller cells. Cell lines were characterized by enzyme histochemistry [menadione-dependent alpha glycerophosphate dehydrogenase (alphaGPDH), marker for angioblasts] and immunocytochemistry. Once characterized, cells were grown on FN, or collagens I or IV substrata and fed platelet-derived growth factor-BB (PDGF-BB) or fibroblast growth factor-2 (FGF-2). The phenotypic expression of a marker for endothelial cells [acetylated LDL (acLDL) uptake] or a marker for pericytes and smooth muscle cells, production of alpha smooth muscle actin (alphaSMA), was evaluated under those conditions. The canine retinal cell lines that were established had the following characteristics when maintained on serum and a retinal extract. Angioblasts had low expression of vWf and VEGF-R2 (two markers for canine endothelial cells), and very low uptake of acLDL but high expression of alphaGPDH and adenosine A2a receptors (A2aR) (two markers for canine angioblasts in vivo). ADREC had high expression of endothelial cell markers (vWf, VEGF-R2, and acLDL uptake) but minimal expression of alphaGPDH and A2aR. Both angioblasts and endothelial cells expressed CXCR4, a marker for hemangioblasts. Angioblasts grown on any of the substrata in the presence of FGF-2 had high uptake of acLDL and low expression of alphaSMA, while those grown in the presence of PDGF-BB had high expression of alphaSMA and low uptake of acLDL. In conclusion, angioblasts cultured from peripheral vascular retina have low expression of endothelial cell markers and high alphaGPDH and A2aR, markers for canine angioblasts in vivo. Angioblasts will internalize acLDL when maintained on FGF-2 and express alphaSMA when maintained on PDGF-BB, suggesting that they have the potential to become endothelial cells or pericytes, i.e. are multipotent.

Effects of Sickle Cell Disease on the Eye: Clinical Features and Treatment

Ocular complications of the sickling disorders are multiple and require continuing assessment to detect lesions early enough for effective prophylactic therapy to maximize visual functioning. The disease requires close monitoring of the patient for progression or regression of lesions in determining the selection of therapeutic options.

The angiopoietin/Tie-2 system in proliferative sickle retinopathy: relation to vascular endothelial growth factor, its soluble receptor Flt-1 and von Willebrand factor, and to the effects of laser treatment

AIM

To determine plasma levels of angiopoietin-1 and angiopoietin-2 (Ang-1, Ang-2), their soluble receptor Tie-2, vascular endothelial growth factor (VEGF), its soluble receptor Flt-1 (as indices of angiogenesis), and von Willebrand factor (vWf, marking endothelial damage/dysfunction) in sickle cell disease (SCD) patients with proliferative sickle retinopathy (PSR), with non-proliferative retinopathy (NPR), or no retinopathy (NR) and in control subjects with normal haemoglobin (AA subjects). In addition, to determine changes with panretinal laser photocoagulation (PRP) therapy.

METHODS

Research indices were measured (ELISA) in 24 SCD patients who had PSR, 16 with NPR, 16 with NR, and from 23 AA subjects. Eight patients received PRP therapy and plasma was obtained before laser treatment and at 6 months after the last PRP session.

RESULTS

Ang-1, Ang-2, VEGF, and vWf (but not Tie-2 or sFlt-1) were raised in SCD patients compared to AA subjects (p<0.01) but there were no differences among the three SCD subgroups. Significant correlations were between Ang-1 and VEGF, Ang-1 and Tie-2, and VEGF and sFlt-1 in patients with SCD (r = 0.67-0.88). Plasma Ang-2, VEGF, sFlt-1, and vWf levels did not change, but Ang-1 fell and Tie-2 rose significantly following PRP therapy.

CONCLUSIONS

SCD patients have raised plasma angiopoietins (Ang-1, Ang-2), VEGF, and vWf compared to AA subjects. These indices did not differ according to severity of retinopathy and only limited changes occurred following PRP. The elevated growth factor levels in SCD may have obscured any association with retinopathy.

Maculopathie ischémique drépanocytaire résolutive après échange érythrocytaire

The authors report a case of a young patient with a recent decrease in unilateral vision. He had homozygote sickle cell disease with multiple general complications. Fundus examination was normal apart from a mild alteration of the macular reflect in the left eye, but fluorescein angiography showed multiple arteriolar macular occlusions, explaining the decrease in vision in the left eye. After erythropheresis, vision acuity improved and fluorescein angiography showed reperfusion. This case suggests that transfusional exchange may improve acute macular ischemia secondary to sickle cell disease.

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.

Immunohistochemical staining and morphometric analysis of the monkey choroidal vasculature

The purpose of this study was to develop a method for staining non-human primate choroidal blood vessels for combined whole mount and histologic analysis. Ten monkey eyes were used in this study. Diabetic and non-diabetic aged rhesus monkeys ranging in age from 16 to 31 years were killed and eyes were obtained immediately after death. Anterior segments were removed and retinas dissected from the posterior eyecup. Eyecups were soaked in 0.1% EDTA for 1hr to remove the retinal pigment epithelium (RPE). The whole choroids were dissected from the sclera, fixed in 2% paraformaldehyde and processed for immunohistochemical demonstration of perlecan, a heparan sulfate proteoglycan, using a streptavidin alkaline phosphatase technique. The alkaline phosphatase reaction product was developed using Histomark Red. Following immunohistochemical staining, choroids were incubated for the enzyme histochemical demonstration of non-specific esterase to label granulocytes. Anti-perlecan was localized to the endothelial cells of viable choroidal blood vessels and provided excellent staining of the choriocapillaris in all regions. Morphometric measurements of choriocapillaris were made in wet preparations using digitized images and image analysis software. The staining was absent in degenerated choroidal capillaries (lacking endothelial cells), thus allowing for sites of pathology to be identified and analysed. The reaction product was retained within the tissue throughout the flat-embedding process and allowed for precise site-specific identification of angiopathic lesions en bloc during sectioning. This technique provides a method of staining monkey choroidal blood vessels in situ and allows for identification and analysis of pathologic changes associated with aging or diseases.

Neutrophils and leucocyte adhesion molecules in sickle cell retinopathy

AIMS

The expression of the adhesion molecules ICAM-1, VCAM-1, and P-selectin, and the distribution and number of polymorphonuclear leucocytes (PMNs) were investigated in sickle cell retinopathy (SCR) and compared to the normal retina.

METHODS

Postmortem ocular tissue was obtained from five subjects (16, 21, 28, 40, and 41 years of age) with sickle haemoglobinopathies and from one control subject. Tissue was cryopreserved, and streptavidin peroxidase immunohistochemistry was performed with antibodies against ICAM-1, VCAM-1, and P-selectin. Immunohistochemical reaction product was scored, and PMN numbers were counted in sections stained with non-specific esterase.

RESULTS

Increased ICAM-1, VCAM-1, and P-selectin immunoreactivities were observed in sickle cell subjects compared to the control subject. The highest ICAM and P-selectin immunoreactivity was associated with intraretinal vessels adjacent to the preretinal neovascular formation in subjects with proliferative retinopathy. This was not the case with VCAM-1 immunoreactivity, which was highest in intraretinal vessels adjacent to the sea fan when the sea fan was still "in statu nascendi." Fully formed, "older" sea fans had the highest levels of VCAM-1. The increase in adhesion molecule immunoreactivity was paralleled by an increase in intraretinal PMNs. The number of intraretinal PMNs increased with progression of the disease and the numbers surpassed those in control subjects by threefold. In the sea fan with the greatest VCAM-1 immunoreactivity, there were 20 times more PMNs were observed than in the rest of the retina in the same subject.

CONCLUSION

These data suggest that adhesion molecule mediated leucocyte adhesion might play an important part in the vaso-occlusive phase of sickle cell retinopathy and in autoinfarction of sea fan formations.

Pleiotropic and epistatic effects in sickle cell anemia

Sickle cell anemia is the first monogenic disease ever described, and it became the paradigm for a disease traceable to a single mutation in a single gene. Pauling's concept of "molecular disease," based on this discovery, opened a new chapter in the history of medicine. Nevertheless, at the phenotypic level, sickle cell anemia is not a monogenic disease; it is a multigenic disease. The latter is the product of pleiotropic genes (involved in secondary pathophysiologic events) and epistatic genes (same gene but with significant pathophysiologic consequences among individual=polymorphism). These secondary events are an important part of the phenotype and explain the intense interindividual differences in the severity of the disease, in spite of all the patients having the same sickle globin gene in the homozygote form. In the last decade a number of epistatic genes and pleiotropic genes have been defined, and many others are potential candidates. CHIP technology and high-throughput sequencing promise to accelerate our full multigenic understanding of this disease, contributing to a more individualized concept of disease in conjunction as we enter the new millennium.