Exploring the choroidal vascular labyrinth and its molecular and structural roles in health and disease.

The choroid is a key player in maintaining ocular homeostasis and plays a role in a variety of chorioretinal diseases, many of which are poorly understood. Recent advances in the field of single-cell RNA sequencing have yielded valuable insights into the properties of choroidal endothelial cells (CECs). Here, we review the role of the choroid in various physiological and pathophysiological mechanisms, focusing on the role of CECs. We also discuss new insights regarding the phenotypic properties of CECs, CEC subpopulations, and the value of measuring transcriptomics in primary CEC cultures derived from post-mortem eyes. In addition, we discuss key phenotypic, structural, and functional differences that distinguish CECs from other endothelial cells such as retinal vascular endothelial cells. Understanding the specific clinical and molecular properties of the choroid will shed new light on the pathogenesis of the broad clinical range of chorioretinal diseases such as age-related macular degeneration, central serous chorioretinopathy and other diseases within the pachychoroid spectrum, uveitis, and diabetic choroidopathy. Although our knowledge is still relatively limited with respect to the clinical features and molecular pathways that underlie these chorioretinal diseases, we summarise new approaches and discuss future directions for gaining new insights into these sight-threatening diseases and highlight new therapeutic strategies such as pluripotent stem cell‒based technologies and gene therapy.

Endothelial tip cells in vitro are less glycolytic and have a more flexible response to metabolic stress than non-tip cells.

Formation of new blood vessels by differentiated endothelial tip cells, stalk cells, and phalanx cells during angiogenesis is an energy-demanding process. How these specialized endothelial cell phenotypes generate their energy, and whether there are differences between these phenotypes, is unknown. This may be key to understand their functions, as (1) metabolic pathways are essentially involved in the regulation of angiogenesis, and (2) a metabolic switch has been associated with angiogenic endothelial cell differentiation. With the use of Seahorse flux analyses, we studied metabolic pathways in tip cell and non-tip cell human umbilical vein endothelial cell populations. Our study shows that both tip cells and non-tip cells use glycolysis as well as mitochondrial respiration for energy production. However, glycolysis is significantly lower in tip cells than in non-tip cells. Additionally, tip cells have a higher capacity to respond to metabolic stress. Finally, in non-tip cells, blocking of mitochondrial respiration inhibits endothelial cell proliferation. In conclusion, our data demonstrate that tip cells are less glycolytic than non-tip cells and that both endothelial cell phenotypes can adapt their metabolism depending on microenvironmental circumstances. Our results suggest that a balanced involvement of metabolic pathways is necessary for both endothelial cell phenotypes for proper functioning during angiogenesis.

Reversal of threatening blindness after initiation of eculizumab in Purtscher-like retinopathy secondary to atypical hemolytic uremic syndrome.

Purtscher-like retinopathy, a rare manifestation of systemic thrombotic microangiopathy, is a potentially visually debilitating condition with no effective proven treatment. Distinct pathogenic pathways have been proposed as etiological factors. We revisit the etiology of Purtscher-like retinopathy based on the rapid response and profound visual improvement after initiation of systemic intravenous eculizumab, an inhibitor of the complement cascade, in a patient with Purtscher-like retinopathy secondary to familial atypical hemolytic uremic syndrome (aHUS) due to a mutation in complement factor H. We hypothesize that the efficacy of eculizumab in this patient provides evidence for pathogenic events in the retina similar to those encountered in the renal microvasculature of aHUS patients, namely complement-mediated thromboembolization as a result of activation of the complement cascade in endothelial cells with release of tissue factor and development and amplification of a procoagulant state. To the best of our knowledge, this is the first report in the literature of eculizumab as an effective therapeutic strategy in Purtscher-like retinopathy.

Stem Cell Derived Retinal Pigment Epithelium: The Role of Pigmentation as Maturation Marker and Gene Expression Profile Comparison with Human Endogenous Retinal Pigment Epithelium.

In age-related macular degeneration (AMD) the retinal pigment epithelium (RPE) deteriorates, leading to photoreceptor decay and severe vision loss. New therapeutic strategies aim at RPE replacement by transplantation of pluripotent stem cell (PSC)-derived RPE. Several protocols to generate RPE have been developed where appearance of pigmentation is commonly used as indicator of RPE differentiation and maturation. It is, however, unclear how different pigmentation stages reflect developmental stages and functionality of PSC-derived RPE cells. We generated human embryonic stem cell-derived RPE (hESC-RPE) cells and investigated their gene expression profiles at early pigmentation (EP) and late pigmentation (LP) stages. In addition, we compared the hESC-RPE samples with human endogenous RPE. We used a common reference design microarray (44 K). Our analysis showed that maturing hESC-RPE, upon acquiring pigmentation, expresses markers specific for human RPE. Interestingly, our analysis revealed that EP and LP hESC-RPE do not differ much in gene expression. Our data further showed that pigmented hESC-RPE has a significant lower expression than human endogenous RPE in the visual cycle and oxidative stress pathways. In contrast, we observed a significantly higher expression of pathways related to the process adhesion-to-polarity model that is typical of developing epithelial cells. We conclude that, in vitro, the first appearance of pigmentation hallmarks differentiated RPE. However, further increase in pigmentation does not result in much significant gene expression changes and does not add important RPE functionalities. Consequently, our results suggest that the time span for obtaining differentiated hESC-RPE cells, that are suitable for transplantation, may be greatly reduced.

Comparing the Effectiveness of Bevacizumab to Ranibizumab in Patients with Exudative Age-Related Macular Degeneration. The BRAMD Study.

PURPOSE: To compare the effectiveness of bevacizumab and ranibizumab in the treatment of exudative age-related macular degeneration (AMD). DESIGN: Multicentre, randomized, controlled, double-masked clinical trial in 327 patients. The non-inferiority margin was 4 letters. PATIENTS: Patients ≥ 60 years of age with primary or recurrent sub- or juxtafoveal choroidal neovascularization (CNV) secondary to AMD with a total area of CNV < 12 disc areas and a best corrected visual acuity (BCVA) score between 20 and 78 letters on an EDTRS like chart in the study eye. METHODS: Monthly intravitreal injections with 1.25 mg bevacizumab or 0.5 mg ranibizumab were given during one year. Intention to treat with last observation carried forward analysis was performed. MAIN OUTCOME MEASURES: Primary outcome was the change in BCVA in the study eye from baseline to 12 months. RESULTS: The mean gain in BCVA was 5.1 (±14.1) letters in the bevacizumab group (n = 161) and 6.4 (±12.2) letters in the ranibizumab group (n = 166) (p = 0.37). The lower limit of the 95% confidence interval of the difference in BCVA gain was 3.72. The response to bevacizumab was more varied; 24% of patients showed a gain of ≥15 letters, 11% a loss of ≥15 letters and 65% a gain or loss < 15 letters compared to 19%, 5% and 76% respectively for ranibizumab (p = 0.038). No significant differences in absolute CRT and CRT change (p = 0.13) or in the presence of subretinal or intraretinal fluid (p = 0.14 and 0.10, respectively) were observed. However, the presence of any fluid on SD-OCT (subretinal and/or intraretinal) differed significantly (p = 0.020), with definite fluid on SD-OCT in 45% of the patients for bevacizumab versus 31% for ranibizumab. The occurrence of serious adverse events and adverse events was similar, with 34 SAEs and 256 AEs in the bevacizumab group and 37 SAEs and 299 AEs in the ranibizumab group (p = 0.87 and p = 0.48, respectively). CONCLUSIONS: Bevacizumab was not inferior to ranibizumab. The response to bevacizumab was more varied with higher percentages of both gainers and losers and more frequently observed retinal fluid on SD-OCT at 12 months when compared to the ranibizumab group. TRIAL REGISTRATION: Trialregister.nl NTR1704.

Detecting signs of retinal leakage in exudative AMD using Cirrus OCT versus SL SCAN-1, a novel integrated FD-OCT into a common slit lamp.

PURPOSE: The purpose is to evaluate the interdevice and interobserver agreements between the SL SCAN-1 (a FD-OCT integrated into a common slit lamp) and a standard stand-alone FD-OCT device (the Cirrus) with regard to the presence or absence of signs of leakage in the retina in patients with exudative AMD and treated with anti-VEGF. METHODS: Fifty-six patients, known to have exudative AMD and under treatment with anti-VEGF agents, were included. During a regular follow-up, OCT scans were made with the Cirrus (macular-cube pattern) and the SL SCAN-1 (radial-scan pattern). All scans were graded by two medical retina specialists for signs of intraretinal cysts, subretinal fluid accumulation, and thickening of the neurosensory retina. Presence of signs of leakage was concluded if one or more of the three signs were present. RESULTS: In 91 % of the patients, the observers made identical conclusions for both devices of the presence of signs of leakage, resulting in an interdevice Kappa coefficient of 0.87. For the scans with disagreement about the presence or absence of signs of leakage, positive and negative conclusions were equally distributed between both devices, and differences were restricted to more subtle signs of leakage. CONCLUSION: The interdevice Kappa coefficient of 0.87 shows a high agreement between the SL SCAN-1 and the Cirrus in grading signs of leakage in exudative AMD. OCT images play a pivotal role in the diagnosis and management of exudative diseases like AMD, and the SL SCAN-1 provides a very efficient approach to these patients with the integration of the FD-OCT device into a common slit lamp.

New approaches for the treatment of diabetic macular oedema: recommendations by an expert panel.

The current standard therapy for patients with diabetic macular oedema (DME)--focal/grid laser photocoagulation--usually does not improve impaired vision, and many patients lose vision despite laser therapy. Recent approval of ranibizumab by the European Medicines Agency to treat visual impairment due to DME fulfils the previously unmet medical need for a treatment that can improve visual acuity (VA) in these patients. We reviewed 1- and 2-year clinical trial findings for ranibizumab used as treatment for DME to formulate evidence-based treatment recommendations in the context of this new therapy. DME with or without visual impairment should be considered for treatment when it fulfils the Early Treatment Diabetic Retinopathy Study (ETDRS) criteria for clinically significant oedema. For DME with centre involvement and associated vision loss due to DME, monthly ranibizumab monotherapy with treatment interruption and re-initiation based on VA stability is recommended. Laser therapy based on ETDRS guidelines is recommended for other forms of clinically significant DME without centre involvement or when no vision loss has occurred, despite centre involvement. Because these recommendations are based on randomised controlled trials of 1-2 years duration, guidance may need updating as long-term ranibizumab data become available and as additional therapeutic agents are assessed in clinical trials.

Protection against methylglyoxal-derived AGEs by regulation of glyoxalase 1 prevents retinal neuroglial and vasodegenerative pathology.

AIMS/HYPOTHESIS: Methylglyoxal (MG) is an important precursor for AGEs. Normally, MG is detoxified by the glyoxalase (GLO) enzyme system (including component enzymes GLO1 and GLO2). Enhanced glycolytic metabolism in many cells during diabetes may overpower detoxification capacity and lead to AGE-related pathology. Using a transgenic rat model that overexpresses GLO1, we investigated if this enzyme can inhibit retinal AGE formation and prevent key lesions of diabetic retinopathy. METHODS: Transgenic rats were developed by overexpression of full length GLO1. Diabetes was induced in wild-type (WT) and GLO1 rats and the animals were killed after 12 or 24 weeks of hyperglycaemia. N ε)-(Carboxyethyl)lysine (CEL), N(ε)-(carboxymethyl)lysine (CML) and MG-derived-hydroimidazalone-1 (MG-H1) were determined by immunohistochemistry and by ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MSMS). Müller glia dysfunction was determined by glial fibrillary acidic protein (GFAP) immunoreactivity and by spatial localisation of the potassium channel Kir4.1. Acellular capillaries were quantified in retinal flat mounts. RESULTS: GLO1 overexpression prevented CEL and MG-H1 accumulation in the diabetic retina when compared with WT diabetic counterparts (p < 0.01). Diabetes-related increases in Müller glial GFAP levels and loss of Kir4.1 at the vascular end-feet were significantly prevented by GLO1 overexpression (p < 0.05) at both 12- and 24-week time points. GLO1 diabetic animals showed fewer acellular capillaries than WT diabetic animals (p < 0.001) at 24 weeks' diabetes. CONCLUSIONS/INTERPRETATION: Detoxification of MG reduces AGE adduct accumulation, which, in turn, can prevent formation of key retinal neuroglial and vascular lesions as diabetes progresses. MG-derived AGEs play an important role in diabetic retinopathy.

Effect of sulodexide on endothelial glycocalyx and vascular permeability in patients with type 2 diabetes mellitus.

AIMS/HYPOTHESIS: Endothelial glycocalyx perturbation contributes to increased vascular permeability. In the present study we set out to evaluate whether: (1) glycocalyx is perturbed in individuals with type 2 diabetes mellitus, and (2) oral glycocalyx precursor treatment improves glycocalyx properties. METHODS: Male participants with type 2 diabetes (n = 10) and controls (n = 10) were evaluated before and after 2 months of sulodexide administration (200 mg/day). The glycocalyx dimension was estimated in two different vascular beds using sidestream dark field imaging and combined fluorescein/indocyanine green angiography for sublingual and retinal vessels, respectively. Transcapillary escape rate of albumin (TER(alb)) and hyaluronan catabolism were assessed as measures of vascular permeability. RESULTS: Both sublingual dimensions (0.64 [0.57-0.75] µm vs 0.78 [0.71-0.85] µm, p < 0.05, medians [interquartile range]) and retinal glycocalyx dimensions (5.38 [4.88-6.59] µm vs 8.89 [4.74-11.84] µm, p < 0.05) were reduced in the type 2 diabetes group compared with the controls whereas TER(alb) was increased (5.6 ± 2.3% vs 3.7 ± 1.7% in the controls, p < 0.05). In line with these findings, markers of hyaluronan catabolism were increased with diabetes (hyaluronan 137 ± 29 vs 81 ± 8 ng/ml and hyaluronidase 78 ± 4 vs 67 ± 2 U/ml, both p < 0.05). Sulodexide increased both the sublingual and retinal glycocalyx dimensions in participants with diabetes (to 0.93 [0.83-0.99] µm and to 5.88 [5.33-6.26] µm, respectively, p < 0.05). In line, a trend towards TER(alb) normalisation (to 4.0 ± 2.3%) and decreases in plasma hyaluronidase (to 72 ± 2 U/ml, p < 0.05) were observed in the diabetes group. CONCLUSION/INTERPRETATION: Type 2 diabetes is associated with glycocalyx perturbation and increased vascular permeability, which are partially restored following sulodexide administration. Further studies are warranted to determine whether long-term treatment with sulodexide has a beneficial effect on cardiovascular risk. TRIAL REGISTRATION: www.trialregister.nl NTR780/ http://isrctn.org ISRCTN82695186 FUNDING: An unrestricted Novartis Foundation for Cardiovascular Excellence grant (2006) to M. Nieuwdorp/E. S. G. Stroes, Dutch Heart Foundation (grant number 2005T037).

Treatment of retinal diseases with VEGF antagonists.

Diabetic retinopathy (DR) and age-related macular degeneration (AMD) are the most prevalent causes of blindness in the Western world. The pathogenesis of neovascularization and vascular leakage, both hallmarks of these diseases, appears to have one common denominator: vascular endothelial growth factor (VEGF). Since the recent introduction of anti-VEGF therapy, intravitreal injections with these agents have become standard care in neovascular AMD, and have been found to be a valuable additional treatment strategy in several other vascular retinal diseases. This review provides an overview of the history of anti-VEGF treatment in the eye, its rationale, its efficacy, and its potential drawbacks.

[The practice guideline 'The red eye' (first revision) of the Dutch College of General Practitioners; a response from the perspective ofthe ophthalmologist]. / De standaard 'Het rode oog' (eerste herziening) van het Nederlands Huisartsen Genootschap; reactie vanuit de oogheelkunde.

The revised guideline 'The red eye' of the Dutch College of General Practitioners contains adequate and scientifically well-supported recommendations for the diagnosis and management of patients with minor ocular trauma and red eyes. Unfortunately the guideline lacks a roadmap for implementation of these recommendations, as well as a definition of indicators for the measurement of implementation. This is important in the light of the limited implementation of the previous guideline 'The red eye' published in 1996.

Advanced glycation end products cause increased CCN family and extracellular matrix gene expression in the diabetic rodent retina.

AIMS/HYPOTHESIS: Referred to as CCN, the family of growth factors consisting of cystein-rich protein 61 (CYR61, also known as CCN1), connective tissue growth factor (CTGF, also known as CCN2), nephroblastoma overexpressed gene (NOV, also known as CCN3) and WNT1-inducible signalling pathway proteins 1, 2 and 3 (WISP1, -2 and -3; also known as CCN4, -5 and -6) affects cellular growth, differentiation, adhesion and locomotion in wound repair, fibrotic disorders, inflammation and angiogenesis. AGEs formed in the diabetic milieu affect the same processes, leading to diabetic complications including diabetic retinopathy. We hypothesised that pathological effects of AGEs in the diabetic retina are a consequence of AGE-induced alterations in CCN family expression. MATERIALS AND METHODS: CCN gene expression levels were studied at the mRNA and protein level in retinas of control and diabetic rats using real-time quantitative PCR, western blotting and immunohistochemistry at 6 and 12 weeks of streptozotocin-induced diabetes in the presence or absence of aminoguanidine, an AGE inhibitor. In addition, C57BL/6 mice were repeatedly injected with exogenously formed AGE to establish whether AGE modulate retinal CCN growth factors in vivo. RESULTS: After 6 weeks of diabetes, Cyr61 expression levels were increased more than threefold. At 12 weeks of diabetes, Ctgf expression levels were increased twofold. Treatment with aminoguanidine inhibited Cyr61 and Ctgf expression in diabetic rats, with reductions of 31 and 36%, respectively, compared with untreated animals. Western blotting showed a twofold increase in CTGF production, which was prevented by aminoguanidine treatment. In mice infused with exogenous AGE, Cyr61 expression increased fourfold and Ctgf expression increased twofold in the retina. CONCLUSIONS/INTERPRETATION: CTGF and CYR61 are downstream effectors of AGE in the diabetic retina, implicating them as possible targets for future intervention strategies against the development of diabetic retinopathy.

[Screening for diabetic retinopathy]. / Screening op diabetische retinopathie.

Concurrent with the increasing incidence of diabetes mellitus, the incidence of diabetic retinopathy is also rising. Timely recognition with the aid of screening, followed by laser therapy, can prevent the greater part of the resulting visual impairment and blindness. However, many patients with diabetes are not screened or not screened adequately. The necessary screening frequency is annually or biannually, depending on the degree of retinopathy and the presence of risk factors, of which glycaemic control, duration of diabetes, blood pressure, lipid profile, and race are the most important. Digital 2-field fundus photography, preferably in mydriasis, is of sufficient quality for routine screening. The impact of screening programmes can be further improved by applying the optimal method and by initiating an active implementation strategy.

Single spot PDT in patients with circumscribed choroidal haemangioma and near normal visual acuity.

BACKGROUND: In circumscribed choroidal hemangiomas (CCH) a long observation period and decreased visual acuity before treatment are risk factors for poor visual outcome. Therefore, we studied the use of limited, single spot photodynamic therapy (PDT) with Visudyne for the timely treatment of CCH. METHODS: Six consecutive patients with CCH, and metamorphopsia but (near) normal visual acuity were treated with PDT, using a single spot covering only the most prominent part of the tumour, and a radiance exposure of 50 J/cm(2). Start of treatment was 6 min following a 1-min infusion with Visudyne (6 mg/m(2) BSA), using a diode laser (692 nm). RESULTS: In all patients, the metamorphopsia disappeared, the OCT images returned to a normal foveal contour, and visual acuity remained 20/20 or improved to 20/20. In five patients, the tumour became ultrasonographically undetectable; in three after one PDT session, in one patient after two and in another patient after three PDT sessions. The last patient had a residual tumour height of 1.2 mm, but no metamorphopsia, a normal foveal contour on OCT, and fluorescein angiography showed no residual leakage. CONCLUSION: The present series demonstrates that single spot PDT might be an effective treatment for CCH with a visual acuity > or =20/30, without serious side-effects during a follow-up of at least 18 months.

Added value of OCT in evaluating the presence of leakage in patients with age-related macular degeneration treated with PDT.

BACKGROUND: Evaluating the presence of leakage on fluorescein angiography (FA) in patients with age-related macular degeneration (AMD) retreated with photodynamic therapy (PDT) can be difficult. New diagnostic tools such as optical coherence tomography (OCT) might help to optimize PDT management. METHODS: Thirty AMD patients scheduled for regular follow-up FA in conjunction with PDT treatment were also scanned with OCT. Follow-up data at 9 months were retrieved from the patients' medical records. Inter-observer agreement [kappa coefficient] for the presence of leakage on FA, for OCT parameters for leakage, and agreement between FA and OCT evaluations were calculated. The indication for retreatment was evaluated using the leakage analysis based on FA alone, OCT alone, and both examinations combined, and compared to the actual follow-up of the patients at 9 months. RESULTS: Agreement between the two observers for the presence of leakage on FA was moderate (kappa=0.51). OCT agreement between the two observers for the presence of leakage was good (kappa=0.85). Agreement between FA and OCT for the presence of leakage was poor (kappa=0.16). Follow-up data at 9 months on all patients were analyzed. Seven out of 30 patients were not retreated at the time of examination, and four of these patients (57%) remained stable without further treatment. Twenty-three patients did receive a PDT treatment at the time of examination; and eight of these patients did not show leakage on OCT, and five of these patients (62%) remained stable without additional treatment. In contrast, only three out of 15 patients (20%) with leakage on both FA and OCT remained stable during this 9 month follow-up period. CONCLUSIONS: Inter-observer agreement for the presence of leakage was moderate for FA and good for OCT. There was considerable disagreement between leakage as judged by OCT and by FA. OCT could be of help in the decision regarding PDT retreatment. Assuming that 57% of the patients without leakage either on FA or OCT would remain stable without retreatment, the rate of probable ineffective retreatment could be reduced from 35% to 20%.

Evaluation of central serous retinopathy with en face optical coherence tomography.

BACKGROUND: The diagnosis of idiopathic central serous retinopathy (CSR) is usually based on biomicroscopy and fluorescein angiography (FA). The optical coherence tomography (OCT) ophthalmoscope produces en face OCT scans (OCT C-scans) and provides additional information not readily available by conventional imaging techniques. The authors describe the characteristic features observed in patients with a clinical diagnosis of CSR using the OCT ophthalmoscope. METHODS: 38 eyes with a clinical diagnosis of CSR, seen at the Academic Medical Centre (Amsterdam, Netherlands) and the New York Eye and Ear Infirmary (New York, USA) between August 2002 and March 2004, were evaluated with standard digital FA and scanned with the OCT ophthalmoscope. RESULTS: Nine of 38 eyes had no serous neurosensory detachment (inactive CSR) when scanned with the OCT ophthalmoscope. Characteristics for active CSR (n=29) were large neurosensory detachment (23/29), subretinal hyper-reflective depoits (20/29), and pigment epithelial detachment (15/29). One third of the patients, either active or inactive, had multiple small pigment epithelial detachments located both within and outside the neurosensory detachment. CONCLUSION: The OCT ophthalmoscope provides complementary morphological information on patients with CSR. The presence of more diffuse retinal pigment epithelium (RPE) changes lends further support to the concept that CSR is a diffuse rather than localised RPE anomaly.

Spare the rod and spoil the eye.

This review presents a new unified view of the pathogenesis of three common causes of acquired retinal degenerative disease-diabetic retinopathy, age related macular degeneration, and retinopathy of prematurity. In these three conditions, angiogenesis has a predominant role in the development of sight threatening pathology. Angiogenesis is controlled by among other factors the expression of vascular endothelial growth factor (VEGF), which in turn is regulated by absolute and relative lack of oxygen. The severe pathological manifestations of these three conditions are not part of a general underlying disease process because they are peculiar to the eye, and the profound hypoxia that develops in normal retina during dark adaptation (rod driven hypoxia) is an adequate and elegant additional factor to explain their pathogenesis. A large number of experimental reports support this conclusion, although rod driven anoxia is not generally considered as a causal factor in ocular disease. However, the hypothesis can be critically tested, and also suggests novel methods of treatment and prevention of these conditions that may be simpler and more inexpensive than current therapies and that have a smaller potential for adverse effects.

Immunohistochemical localization of vascular endothelial growth factor receptors-1, -2 and -3 in human spinal cord: altered expression in amyotrophic lateral sclerosis.

Vascular endothelial growth factor (VEGF) has recently been implicated in several neurological disorders. Apart from its prominent role in angiogenesis, VEGF has been shown to have direct effects on neuronal and glial cells through activation of different VEGF receptor (VEGFR) types. In the present study the expression patterns of VEGFR-1, -2 and -3 were investigated in the spinal cord of control and both sporadic and familial amyotrophic lateral sclerosis (ALS) patients. Immunocytochemical analysis of control human spinal cord demonstrated that VEGFR-1, but not VEGFR-2 or -3 was found to be present in blood vessels of both white and grey matter. All three VGEFRs were not detectable in resting glial cells of control tissue. Diffuse neuropil staining was observed in the control spinal cord grey matter for VEGFR-3. Regional differences in VEGFRs immunoreactivity (IR) were apparent in ALS compared to controls. In particular, VEGFR-1 expression was increased in reactive astroglial cells in both grey (ventral horn) and white matter of ALS spinal cord. In addition to the astroglial labelling, increased expression of VEGFR-1 and, to a less extent also of VEGFR-2, was observed in blood vessels of the ALS spinal cord. No changes in VEGFR-3 IR were detected in blood vessels or reactive astroglial cells, whereas VEGFR-3 neuropil expression was reduced and paralleled the distribution of neuronal loss in the ventral horn of ALS spinal cord. These findings indicate that VEGFRs have specific distribution patterns, suggesting different physiological functions in human spinal cord. Moreover, the altered expression observed in ALS supports a role for these receptors in the complex reactive processes that are associated with the progression of spinal cord damage.

Differential expression of connective tissue growth factor in microglia and pericytes in the human diabetic retina.

BACKGROUND/AIM: Connective tissue growth factor (CTGF) stimulates extracellular matrix formation, fibrosis, and angiogenesis. It has a role in the pathogenesis of diabetic nephropathy and possibly in diabetic retinopathy (DR): in cultured retinal vascular cells CTGF is induced by VEGF-A. To further characterise this role the authors investigated CTGF expression in normal and diabetic human retina. METHODS: CTGF expression patterns were studied by immunohistochemistry in the retina of eyes of 36 diabetic persons and 18 non-diabetic controls and compared with markers of endothelial cells (CD31, PAL-E), pericytes (NG2), astrocytes (GFAP), and microglia (CD45). RESULTS: In the retina, distinct and specific staining of CTGF was observed in microglia, situated around or in close vicinity of retinal capillaries. In the control cases, sporadic staining of pericytes was also observed within the vascular wall. In contrast, in the retina of people with diabetes, CTGF staining in microglia was decreased and staining in pericytes was increased. This pattern of predominantly pericyte staining was observed in 20 out of 36 diabetic cases and in one out of 18 controls. The altered CTGF staining patterns in the diabetic cases did not correlate to staining of PAL-E, a marker of retinal vascular leakage associated with DR. CONCLUSIONS: The study shows that CTGF is expressed in microglia in the normal retina whereas in a large subset of diabetic persons, CTGF expression shifts to microvascular pericytes. This altered CTGF expression pattern appears unrelated to manifest DR and may therefore represent a preclinical retinal change caused by diabetes. The results suggest a distinct, but as yet unidentified, role of CTGF in the pathogenesis of diabetic retinopathy.