Biomedical subjects

R O Schlingemann

Publications and source records attributed to R O Schlingemann.

At least 19 recordsLinked to original sources

PubMed2006

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%.

Aged↗

PubMed2006

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.

Adult↗

PubMed2005

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.

Animals↗

PubMed2005

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.

Acute Disease↗

PubMed2004

[Routine funduscopic examination in hypertensive patients not useful].

Funduscopic examination according to the classification of Keith, Wagener and Barker has been used since 1939 to assess retinal damage in patients with hypertension. Improved treatment possibilities and the screening of patients with hypertension seem to have led to a decrease in the incidence and severity of the retinal abnormalities found. The following findings have been published during the past ten years. The assessment of retinopathy is subject to a large interobserver-variability, especially with respect to venous-crossings and arteriolar narrowing of retinal vessels. The positive and negative predictive value of retinopathy for high blood pressure is low. The association of retinopathy with other predictive indicators for organ damage is inconsistent and its association with cardiovascular complications is weak. These findings indicate that the usefulness of funduscopic examination as an instrument for assessing organ damage in patients with hypertension is limited. Therefore it should not be used as a routine diagnostic tool unless a hypertensive crisis is indicated.

Female↗

PubMed2004

Are tumours angiogenesis-dependent?

The final proof of principle that cancer patients can be effectively treated with angiogenesis inhibitors is eagerly awaited. Various preclinical in vivo experiments have proven that most tumours need new vessel formation in order to grow and to form metastases. First of all, tumours do not grow in avascular corneas until new blood vessels reach the implant. Secondly, the introduction of only one angiogenic gene can cause a switch from tumour dormancy to progressive tumour growth. Thirdly, tumour growth can be inhibited and sometimes tumour regression can be obtained just by attacking the vascular compartment with specific angiogenesis inhibitors. These three examples of preclinical experiments and many others have led to the conclusion that, in general, tumours are angiogenesis-dependent. Supported by disappointing clinical results, the angiogenesis dependency of tumours has been questioned, mainly because of the immaturity and the presumed lack of a functional blood supply (oxygen delivery and discarding of waste products) from a newly formed tumour vasculature. However, human tumours are highly heterogeneous in vascular architecture, differentiation, and functional blood supply. Vascular immaturity is a natural consequence of a genetically based unlimited expansion of tumour cells, compared to the well-regulated growth of different organs during embryonic development, for example. Unlimited tumour expansion and therefore the continuous stimulation of vessel outgrowth prevent endothelial cells from generating a mature vasculature, but instead continuously stimulate them to expand the vascular compartment of the growing tumour. In this review, the translation of angiogenesis inhibitors as a treatment for cancer from preclinical experiments to the clinic is evaluated. The preclinical evidence that tumours are angiogenesis-dependent is summarized and explanations are put forward for why the clinical results so far are not as exciting as was expected from preclinical studies. Reviewing the translation, one may conclude that human tumours are heterogeneous in their vascular architecture and function and that tumour-induced angiogenesis in humans is a more complex (multifactorially regulated) process compared with angiogenesis in preclinical cancer models.

Angiogenesis Inducing Agents↗

PubMed2004

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.

Adult↗

PubMed2004

Vascular leucocyte adhesion molecules unaltered in the human retina in diabetes.

BACKGROUND/AIMS: Capillary occlusion is believed to have a critical role in the development of diabetic retinopathy (DR). The exact mechanism by which it occurs, however, remains unclear. Several in vitro and animal model studies have suggested increased adhesion of leucocytes to the endothelium via upregulated ICAM-1 on the retinal microvasculature as a possible mechanism. In this comparative immunohistochemical study the expression of ICAM-1 was compared in the retinal vasculature of 41 eyes obtained from 37 diabetic people with 19 eyes from 19 non-diabetic controls. METHODS: Serial cryosections of postmortem posterior tissue from 41 diabetic eyes and 19 non-diabetic eyes were stained with the monoclonal antibodies ICAM-1 (two clones), CD31(panendothelial marker), and PAL-E (vascular leakage marker). RESULTS: A similar pattern of vascular ICAM-1 staining was observed between diabetic and non-diabetic eyes. A diffuse ICAM-1 staining of the retina was also observed that was significantly more intense in the diabetic subjects (p = 0.001). CONCLUSION: These results indicate that ICAM-1 is constitutively expressed on retinal and choroidal vasculature of non-diabetic, control subjects and that this level of expression is not significantly altered by the diabetic environment. Taken together, these results do not support the prevalent paradigm of increased adhesion molecule expression as a primary mechanism responsible for capillary occlusion reported in diabetic individuals.

Adolescent↗

PubMed2004

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.

Aged↗

PubMed2003

Longstanding symptomatic choroidal hemangioma managed with limited PDT as initial or salvage therapy.

PURPOSE: To describe the use of limited, low-irradiance, single-spot photodynamic therapy (PDT) with verteporfin for the treatment of symptomatic choroidal hemangiomas. METHODS: Thirteen consecutive patients with a circumscribed choroidal hemangioma were treated with limited PDT 6 min following a 1-min infusion with verteporfin (6 mg/m(2) body surface area), using a diode laser (692 nm) and a single spot large enough to cover only the most prominent part of the tumor. Exposure time was 166 s in the first three patients and 83 s in the last ten patients, resulting in a radiance exposure of respectively 100 and 50 J/cm(2). RESULTS: In all 11 not previously conventionally treated patients, visual acuity improved following PDT treatment. The two remaining patients with prior radiation treatment both reported widening of the visual field and sharper vision, but did not show an increase in ETDRS vision. In all but four patients the tumor became ultrasonographically undetectable by the first follow-up visit at 6 weeks, with only a slight irregularity at the level of the previous tumor remaining. In four patients the residual tumor was still detectable, and they received a second treatment, following which the tumor flattened completely. In all patients the retinal detachment disappeared. CONCLUSION: The present series demonstrates that even limited, low-irradiance, single-spot photodynamic therapy with verteporfin is an effective first-line treatment for choroidal hemangiomas.

Adult↗

PubMed2003

Vascular endothelial growth factors and angiogenesis in eye disease.

The vascular endothelial growth factor (VEGF) family of growth factors controls pathological angiogenesis and increased vascular permeability in important eye diseases such as diabetic retinopathy (DR) and age-related macular degeneration (AMD). The purpose of this review is to develop new insights into the cell biology of VEGFs and vascular cells in angiogenesis and vascular leakage in general, and to provide the rationale and possible pitfalls of inhibition of VEGFs as a therapy for ocular disease. From the literature it is clear that overexpression of VEGFs and their receptors VEGFR-1, VEGFR-2 and VEGFR-3 is causing increased microvascular permeability and angiogenesis in eye conditions such as DR and AMD. When we focus on the VEGF receptors, recent findings suggest a role of VEGFR-1 as a functional receptor for placenta growth factor (PlGF) and vascular endothelial growth factor-A (VEGF)-A in pericytes and vascular smooth muscle cells in vivo rather than in endothelial cells, and strongly suggest involvement of pericytes in early phases of angiogenesis. In addition, the evidence pointing to distinct functions of VEGFs in physiology in and outside the vasculature is reviewed. The cellular distribution of VEGFR-1, VEGFR-2 and VEGFR-3 suggests various specific functions of the VEGF family in normal retina, both in the retinal vasculature and in neuronal elements. Furthermore, we focus on recent findings that VEGFs secreted by epithelia, including the retinal pigment epithelium (RPE), are likely to mediate paracrine vascular survival signals for adjacent endothelia. In the choroid, derailment of this paracrine relation and overexpression of VEGF-A by RPE may explain the pathogenesis of subretinal neovascularisation in AMD. On the other hand, this paracrine relation and other physiological functions of VEGFs may be endangered by therapeutic VEGF inhibition, as is currently used in several clinical trials in DR and AMD.

Animals↗

PubMed2002

[Eye complaints indicative of a tumor elsewhere in the body].

A variety of clinical presentations of malignant tumour metastases outside of the eye and orbit, were seen in four patients: a 52-year-old man who was scheduled to have a surgical removal of an oesophageal carcinoma and who presented with retinal detachment, a 58-year-old woman in whom retinopathy was the first sign of a cervical carcinoma (cancer-associated retinopathy), a 71-year-old man who had been treated for colon carcinoma and who presented with an orbital mass, and finally a 67-year-old woman with an orbital mass as the first sign of a Grawitz tumour. Metastasis should be considered in patients with a history of malignancy, who present with ophthalmologic complaints. Further it should be borne in mind that eye problems can be the first sign of oncological disease outside the eye.

Aged↗

PubMed2002

[The practice guideline 'Refraction errors' from the Dutch College of General Practitioners: response from the perspective of ophthalmology].

The practice guideline 'Refraction errors' from the Dutch College of General Practitioners provides a guideline for referral of persons aged 6 to 65 with gradual loss of vision to either an optician or an ophthalmologist. In this guideline, relevant questions regarding important symptoms are missing, and the value of the proposed examination employing 'diagnostic refraction' has insufficient scientific support. In addition, the possibility to send children between 6 and 10 years of age to the optician may be dangerous for some of the patients, and there are no explicit indications for the urgency of referral to the ophthalmologist. Due to these short-comings, the guideline may fail to provide optimal preventive and therapeutic eye care for the target group of patients concerned.

Adolescent↗

PubMed2002

[Eye problems due to contact lenses; an advisory report from the Health Council of the Netherlands].

In a recent report, the Committee on Health Risks of Contact Lenses from the Health Council of the Netherlands evaluated the health risks of contact lens wear in the Netherlands. Contact lens-related eye disease appears to be common, with an incidence of approximately 80,000 persons per year, who suffer from self-limiting or mild conditions. Such conditions are multifactorial, caused for example by chronic hypoxia, tear-film dysfunction or inadequate fit of the lens. They can range from ocular irritation to giant papillary conjunctivitis, a common cause of permanent lens intolerance. A very serious complication of contact lens wear is infectious keratitis, caused by bacteria or fungi. This is most common in users of permanent-wear soft lenses (20 per 10,000 persons per year) and can lead to a severe loss of vision. Therefore, the Committee has recommended that permanent-wear lenses should not be used. Moreover, lens fitting and follow-up of contact lens wearers should be a prerequisite for optometrists and ophthalmologists. However, the Dutch government has not taken action with respect to this last recommendation.

Contact Lenses↗

PubMed2001

An anti-angiogenic state in mice and humans with retinal photoreceptor cell degeneration.

Abnormal angiogenesis accompanies many pathological conditions including cancer, inflammation, and eye diseases. Proliferative retinopathy because of retinal neovascularization is a leading cause of blindness in developed countries. Another major cause of irreversible vision loss is retinitis pigmentosa, a group of diseases characterized by progressive photoreceptor cell degeneration. Interestingly, anecdotal evidence has long suggested that proliferative diabetic retinopathy is rarely associated clinically with retinitis pigmentosa. Here we show that neonatal mice with classic inherited retinal degeneration (Pdeb(rd1)/Pdeb(rd1)) fail to mount reactive retinal neovascularization in a mouse model of oxygen-induced proliferative retinopathy. We also present a comparable human paradigm: spontaneous regression of retinal neovascularization associated with long-standing diabetes mellitus occurs when retinitis pigmentosa becomes clinically evident. Both mouse and human data indicate that reactive retinal neovascularization either fails to develop or regresses when the number of photoreceptor cells is markedly reduced. Our findings support the hypothesis that a functional mechanism underlying this anti-angiogenic state is failure of the predicted up-regulation of vascular endothelial growth factor, although other growth factors may also be involved. Preventive and therapeutic strategies against both proliferative and degenerative retinopathies may emerge from this work.

Animals↗

PubMed2001

Endothelial cell hypertrophy induced by vascular endothelial growth factor in the retina: new insights into the pathogenesis of capillary nonperfusion.

OBJECTIVE: To investigate the mechanism leading to capillary nonperfusion of the retina in a monkey model of vascular endothelial growth factor A (VEGF)-induced retinopathy in which capillary closure occurs in a late stage after VEGF treatment. METHODS: Two monkeys received 4 intravitreous injections of 0.5 microg of VEGF in one eye and of phosphate-buffered saline in the other eye and were killed at day 9. After perfusion and enucleation, retinal samples were snap frozen for immunohistochemical analysis with the panendothelial cell marker CD31 or were fixed for morphometric analysis at the light and electron microscopic level. RESULTS: At the light microscopic level, all capillaries in the retina of VEGF-injected eyes displayed hypertrophic walls with narrow lumina. In a quantitative analysis of the deep capillary plexus in the inner nuclear layer, VEGF-injected eyes had a significant 5- to 7-fold decrease in total capillary luminal volume. CD31 staining showed that this decrease was not accompanied by a change in the number of capillaries. Electron microscopy revealed that the luminal volume of individual capillaries of the inner nuclear layer of VEGF-injected eyes was significantly decreased due to a 2-fold hypertrophy of the endothelial cells. CONCLUSIONS: Luminal narrowing caused by endothelial cell hypertrophy occurs in the deep retinal capillary plexus in VEGF-induced retinopathy in monkeys. This suggests a causal role of endothelial cell hypertrophy in the pathogenesis of VEGF-induced retinal capillary closure. A similar mechanism may operate in retinal conditions in humans associated with ischemia and VEGF overexpression. CLINICAL RELEVANCE: Capillary nonperfusion occurs in diabetic retinopathy and other ischemic diseases associated with overexpression of VEGF. In addition, VEGF-induced endothelial cell hypertrophy may be causative for capillary closure in these diseases.

Animals↗

PubMed2001

VEGFR-3 in adult angiogenesis.

Vascular endothelial growth factor receptor 3 (VEGFR-3, Flt-4), the receptor for vascular endothelial growth factors (VEGFs) C and D, is expressed on lymphatic endothelium and may play a role in lymphangiogenesis. In embryonic life, VEGFR-3 is essential for blood vessel development. The purpose of this study was to investigate whether VEGFR-3 is also involved in blood vessel angiogenesis in the adult. This was studied in human tissues showing angiogenesis and in a model of VEGF-A-induced iris neovascularization in the monkey eye, by the use of immunohistochemistry at the light and electron microscopic level. VEGFR-3 was expressed on endothelium of proliferating blood vessels in tumours. In granulation tissue, staining was observed in the proliferative superficial zone in plump blood vessel sprouts, in the intermediate zone in blood vessels and long lymphatic sprouts, and in the deeper fibrous zone in large lymphatics, in a pattern demonstrating that lymphangiogenesis follows behind blood vessel angiogenesis in granulation tissue formation. At the ultrastructural level, VEGFR-3 was localized in the cytoplasm and on the cell membrane of endothelial cells of sprouting blood vessels and sprouting lymphatics. In monkey eyes injected with VEGF-A, blood vessel sprouts on the anterior iris surface and pre-existing blood vessels in the iris expressed VEGFR-3. In conclusion, these results support a role for VEGFR-3 and its ligands VEGF-C and/or VEGF-D in cell-to-cell signalling in adult blood vessel angiogenesis. The expression of VEGFR-3 in VEGF-A-induced iris neovascularization and in pre-existing blood vessels exposed to VEGF-A suggests that this receptor and possibly its ligands are recruited in VEGF-A-driven angiogenesis.

Animals↗

PubMed2001

Vascular localization of heparan sulfate proteoglycans in retinas of patients with diabetes mellitus and in VEGF-induced retinopathy using domain-specific antibodies.

PURPOSE: The Steno hypothesis (Deckert et al. ) states that in diabetes mellitus (DM), changes in vascular heparan sulfate proteoglycan (HSPG) expression are involved in systemic endothelial dysfunction and increased capillary permeability. In diabetes-induced glomerular capillary leakage, loss of HSPG and its side chains has been documented. This study aimed to investigate whether microvascular leakage in diabetic retinopathy (DR) is also associated with altered expression of HSPG in retinal microvessels. METHODS: Serial cryosections of post-mortem eyes of 22 subjects with DM and 7 controls were stained with antibodies against the core proteins of the basement membrane HSPGs agrin (Abs Bl31 and JM72) and perlecan (Ab 1948), and four antibodies against heparan sulfate side chains (HS) (Abs JM403, HepSS1, JM13, 3G10). Moreover, we investigated Cynomolgus monkey eyes injected with vascular endothelial growth factor (VEGF)-A, as a model of retinal microvas-cular leakage. The endothelial antigen PAL-E was used to detect microvascular leakage. RESULTS: In the retina of all controls and DM cases, agrin and perlecan core proteins and HS as recognized by JM403 and 3G10 were expressed in the walls of microvessels. Staining for JM13 was variable between cases, but unrelated to microvascular leakage as determined by PAL-E. Staining for HepSS1 was absent in all human retinal microvessels. In monkey retinas, HSPG staining was identical to that in human retinal tissues, except for the staining for HepSS1, which was found absent in control monkey eyes but which was positive in VEGF-injected eyes. CONCLUSIONS: Increased microvascular permeability in human DR is not associated with changes in expression of the HSPGs studied, whereas high amounts of VEGF may induce increased expression of the HS side chain epitope recognized by HepSS1. These results suggest that the mechanism underlying retinal leakage is different from diabetic glomerular capillary leakage.

Aged↗