Roles of vascular endothelial growth factor and astrocyte degeneration in the genesis of retinopathy of prematurity

PURPOSE: To assess the role of vascular endothelial growth factor (VEGF) in the feline model of retinopathy of prematurity (ROP). METHODS: Retinopathy of prematurity was induced in neonatal cats by raising them in an oxygen-enriched (70% to 80%) atmosphere for 4 days to suppress vessel formation and then returning them to room air for 3 to 27 days. In situ hybridization was used to detect the expression of VEGF and its high-affinity receptor, flk-1, in the retina of neonatal cats, and glial fibrillary acidic protein immunocytochemistry was used to assess astrocyte status. RESULTS: The expression of VEGF in the innermost layers of retina fell in hyperoxia and increased on return to room air. Vascular endothelial growth factor expression was transient; it was maximal where vessels were about to form, and it rapidly downregulated after vessels had formed. During the proliferative vasculopathy of ROP, VEGF expression was stronger than in the normally developing retina, and the astrocytes that normally express VEGF degenerated. After the degeneration of astrocytes, VEGF was expressed by neurones of the ganglion cell layer. flk-1 was expressed by intraretinal and preretinal vessels. Supplemental oxygen therapy reduced or eliminated the overexpression of VEGF expression, astrocyte degeneration, and formation of preretinal vessels. CONCLUSIONS: Regulation of VEGF by tissue oxygen mediates the inhibition of vessel growth during hyperoxia and the subsequent proliferative vasculopathy. Degeneration of retinal astrocytes creates conditions for the growth of preretinal vessels.     

Role of astrocytes in the control of developing retinal vessels

PURPOSE: To assess the role of astrocytes in controlling the growth of developing retinal vessels. METHODS: Growth of retinal vessels in the neonatal rat retina was examined in three conditions: normal development, cyclic hyperoxia, and normoxia (1 day 70% to 75% oxygen, 1 day room air for up to seven cycles from birth, and room air for up to 16 days), and direct hypoxia (10% oxygen from postnatal day 3 [P3]). Retinas were examined as wholemounts labeled for astrocytes, microglia, and blood vessels and in some experiments for the fragmentation of DNA characteristic of apoptosis. RESULTS: In normoxia, superficial retinal vessels formed to the processes of astrocytes. In cyclic hyperoxia, the depletion of superficial retinal vessels and subsequent neovascularization described by others were confirmed. The neovascularization was preceded by the depletion by apoptotic death of the astrocyte population, first between vessels but eventually breaching the glia limitans along vessels. The earliest forms of neovascularization resembled microaneurysms, each protruding through a defect in the glia limitans of a capillary. Neurons of the ganglion cell layer survived. Direct hypoxia from P3 caused hypertrophy of superficial vessels. Between P3 and P6, some vessels accelerated past the still-spreading astrocytes, often growing out of the retina into the vitreous humor. Direct hypoxia also caused astrocyte degeneration, but capillaries retained astrocyte investment and were not the site of vascular damage. By P8, breaches in the astrocytic glia limitans became prominent but were restricted to large veins. At such breaches, bleeding into the vitreous humor was common. CONCLUSIONS: Retinal vessels normally develop in close association with astrocytes. Where that association is broken, preretinal vessels may grow or bleed into the vitreous humor. Astrocytes play important roles in constraining retinal vessels to the retina and in maintaining their integrity.     

Basic fibroblast growth factor is neither necessary nor sufficient for the development of retinal neovascularization

Basic fibroblast growth factor (FGF2) is constitutively expressed in the retina and its expression is increased by a number of insults, but its role in the retina is still uncertain. This study was designed to test the hypothesis that altered expression of FGF2 in the retina affects the development of retinal neovascularization. Mice with targeted disruption of the Fgf2 gene had no detectable expression of FGF2 in the retina by Western blot, but retinal vessels were not different in appearance or total area from wild-type mice. When FGF2-deficient mice were compared with wild-type mice in a murine model of oxygen-induced ischemic retinopathy, they developed the same amount of retinal neovascularization. Transgenic mice with a rhodopsin promoter/Fgf2 gene fusion expressed high levels of FGF2 in retinal photoreceptors but developed no retinal neovascularization or other abnormalities of retinal vessels; in the ischemic retinopathy model, they showed no significant difference in the amount of retinal neovascularization compared with wild-type mice. These data indicate that FGF2 expression is not necessary nor sufficient for the development of retinal neovascularization. This suggests that agents that specifically antagonize FGF2 are not likely to be useful adjuncts in the treatment of retinal neovascularization and therapies designed to increase FGF2 expression are not likely to be complicated by retinal neovascularization.     

Histopathologic features of neovascularization in sickle cell retinopathy

PURPOSE: To examine the histopathologic and morphometric features of neovascular lesions in human proliferative sickle cell retinopathy. METHODS: Postmortem ocular tissue was obtained from three subjects (aged 20, 28, and 40 years) with SS hemoglobinopathy and prepared for adenosine diphosphatase flat-embedding. Morphometric analysis was performed before serial sectioning. RESULTS: Numerous active and autoinfarcted lesions were found that represented virtually all stages in the life cycle of preretinal neovascularization. These formations ranged from single small loops extending from arteries and veins along the retinal surface to the typical complex, elevated sea fan formations. Sea fans developed at hairpin loops and at arteriovenous crossings. There was an average of 5.6 connections between sea fans and retinal vessels; of these, 45% were arteriolar, 52.5% were venular, and 2.6% were at the capillary level. Six of eight sea fans were located at arteriovenous crossings. Autoinfarction appeared to occur initially within the sea fan capillaries. The average height of sea fans was 123 microns above the retinal surface. CONCLUSIONS: Preretinal neovascularization in sickle cell retinopathy can arise from both the arterial and venous sides of the retinal vasculature and can assume a variety of morphologic configurations. Multiple feeding arterioles and draining venules are common, and autoinfarction appears to occur initially at the preretinal capillary level rather than at feeding arterioles. Arteriovenous crossings may be a preferential site for sea fan development.     

Transient shallow anterior chamber induced by supraciliary fluid after vitreous surgery

PURPOSE: To report a patient with idiopathic retinal venous beading and recurrent preretinal hemorrhage. METHOD: Case report of a 17-year-old girl with bilateral retinal venous beading, greater in the left eye than in the right eye, and recurrent preretinal hemorrhage in the left eye. RESULTS: Complete blood cell count, platelet count, blood glucose level, and hemoglobin electrophoresis were normal. Fluorescein angiography showed normal retinal arterial and venous filling with no evidence of retinal capillary nonperfusion or neovascularization. CONCLUSION: Idiopathic retinal venous beading may be associated with recurrent preretinal hemorrhage, even in the absence of retinal ischemia or neovascularization.     

Promotion of healthy lifestyle: knowledge and attitudes of primary care physicians

Preretinal neovascularization and chronic retinal oedema are the two major sight-threatening complications that can occur during diabetic retinopathy. Ocular neovascularization is strongly associated with retinal ischaemia, and growth factors have been implicated in its pathogenesis. The ischaemic retina is assumed to secrete growth factors that stimulate residual vessels to proliferate. Interest has focused on basic fibroblast growth factor (bFGF), insulin-like growth factor-1 (IGF-1), platelet-derived growth factor (PDGF), transforming growth factor beta (TGF beta) and more recently vascular endothelial cell growth factor (VEGF). Histologic studies have demonstrated the presence of growth factor proteins and receptors and/or their mRNA, mainly VEGF, PDGF, and bFGF, in preretinal membranes of patients with proliferative diabetic retinopathy. Elevated intravitreal levels of IGF-1 and VEGF correlating with neovascular activity have been found in some patients. However, a direct causal relationship between ischaemia, growth factors and neovascularization has not been clearly demonstrated despite considerable research work. To date, the growth factor correlating most closely with neovascularization is VEGF. As many growth factors seem to be produced during the neovascular process, their specific inhibition probably will have limited effects. Laser photocoagulation of the retina has proved beneficial for regression of new vessels, probably through destruction of the ischaemic retina producing neovascular growth factors, and is currently the only treatment for proliferative diabetic retinopathy. Inhibition of IGF-1 by somatostatin analogs has produced unsatisfactory results. Other vascular inhibitors are currently being studied.     

Developmental expression of laminin beta 2 in rat retina. Further support for a role in rod morphogenesis

PURPOSE: The authors previously hypothesized that laminin beta 2 (S-laminin) plays a role in directing photoreceptor development. The aim of this study was to examine the temporal and spatial expression pattern of beta 2 laminins in rat retina to test this hypothesis. METHODS: Retinas from Sprague-Dawley rats were harvested on embryonic days (E) 14, 16, and 21, as well as on postnatal days (P) 2, 5, and 10. Cryostat sections were probed with antibodies directed against beta 2 laminin, laminin-1 (alpha 1-beta 1-gamma 1), and von Willebrand factor. RESULTS: At the onset of rod photoreceptor birth (E14), laminin beta 2 surrounds the cells of the retinal pigmented epithelium (RPE) and is present on the apical surface of the retinal neuroepithelium. At E16, laminin beta 2 persists on the apical surface of the neuroepithelium and the subjacent apical surface of the RPE. At birth, laminin beta 2 fills the matrix between the juxtaposed surfaces of the RPE and neuroepithelium; moreover, laminin beta 2 immunoreactivity penetrates the neural retina. Throughout postnatal development, laminin beta 2 immunoreactivity surrounds maturing inner and outer segments. Laminin beta 2 also is found in association with blood vessels in the neural retina itself, as well as with choroidal blood vessels; in both places, it is co-localized with an endothelial marker, von Willebrand factor, and laminin-1. CONCLUSIONS: The spatial and temporal expression of laminin beta 2 is consistent with its hypothesized role in rod development. Laminin beta 2 is in a unique position to interact with mitotically active cells (in early retinal development), uncommitted progenitors (in late embryonic development), developing rods (in early postnatal development), and mature outer segments (throughout adulthood). Together with our earlier functional data, these data support our hypothesis that this molecule is an important component of the interphotoreceptor matrix.     

Regenerating sciatic nerve does not utilize circulating cholesterol

Vascular endothelial growth factor (VEGF) is a major contributor to retinal neovascularization. The possible participation of VEGF and its high-affinity tyrosine kinase receptors, flk-1 and flt-1, in early background diabetic retinopathy was studied in the streptozotocin-induced diabetic rat model of experimental retinopathy using in situ hybridization, blotting techniques, and immunohistochemistry. Diabetic retinopathy was assessed by quantitative morphometry of retinal digest preparations. The number of acellular capillaries increased 2.7-fold in diabetic animals with diabetes' duration of 6 months compared with nondiabetic controls. VEGF expression was not detectable by in situ hybridization in nondiabetic rats but was highly increased in the ganglion cell layer and in the inner and outer nuclear layers of retinas from diabetic animals. VEGF protein was extractable only from diabetic retinas, and a strong immunolabeling was detected in vascular and perivascular structures. Increased flk-1 and flt-1 mRNA levels were also found in the ganglion cell and both nuclear layers of diabetic samples only. Dot blot and Western blot analyses confirmed the increase in flk-1 mRNA and protein in diabetic retinas. Also, flk-1 immunoreactivity was associated with vascular and nonvascular structures of the inner retinas from diabetic animals. These data obtained from a rodent model in which retinal neovascularization does not occur support the concept that the VEGF/VEGF receptor system is upregulated in early diabetic retinopathy.     

Immunohistochemical study on the prognostic value of the expression of laminin and Ki-67 receptors in advanced gastric cancer

The expression of 67-KDa laminin receptor (LR) was investigated in a group of 75 patients who underwent curative gastrectomy for advanced gastric cancer, with special reference to the possible role in the tumor progression and in the overall survival. In 56 out of these 75 patients also the prognostic significance of proliferative activity was investigated using the monoclonal antibody Ki-67. The tumor LR expression and the Ki-67 labeling index (Ki-67 LI) were immunohistochemically determined in paraffin-embedded sections using the avidin-biotin immunoperoxidase method. The cumulative 5-years survival rate was 75.1% for patients without expression of LR, 52.6% for those with positive LR expression. Significant association between LR expression and depth of tumor invasion (p = 0.022) was found. By univariate analysis the presence of laminin receptor seemed to be associated with an higher risk of death (RR1.73-95% C.I. 0.71-4.20), but this effect disappeared after controlling for depth of tumor invasion. There was no significant relationship between the Ki-67 LI and wall invasion (p = 0.80) or nodal status (p = 0.73). The cumulative 5-year survival rates (95% CI) were 61.0% (35.3-79.2) in patients with Ki-67 index < 10%, 52.4% (29.7-70.9) with Ki-67 index = 10%-40%, 52.9% (27.6-73.0) with Ki-67 index > 40% and the differences were not statistically significant (p = 0.93). Also in multivariate analysis the proliferative activity did not independently affect survival (p = 0.98). An interaction between Ki-67 index and age was found and Ki-67 index > 40% was significantly associated with a poor prognosis in patients over 70 years old old (p = 0.002). In conclusion, tumor expression of laminin receptor could be correlated with gastric cancer aggressiveness, however its prognostic significance is already provided by depth of tumor invasion. The proliferative activity, determined with the monoclonal antibody Ki-67, does not seems to influence the survival except in elderly patients (> or = 70 years old).     

Factors influencing life-sustaining treatment decisions in a community sample of families

The 67-kD laminin receptor (67LR) is a cell membrane-associated molecule exhibiting high affinity for the basement membrane glycoprotein, laminin. While export of the 67LR toward the extracellular matrix has been recently suggested by electron microscopy studies, there is to date no evidence of shedding of the 67LR from cells. Using two monoclonal antibodies directed against the 67LR, we developed a double-determinant radioimmunoassay that demonstrates that the 67LR is released from cancer cells into the culture medium. The shed molecule exhibited the same apparent molecular weight as that of the membrane-associated 67LR, suggesting that no proteolytic cleavage is involved in the process. Furthermore, we demonstrate that the 67LR is not anchored to the membrane through a glycolsyl-phosphatidylinositol bridge. However, the observation that lactose increased the release of 67LR suggests that a lectin-type interaction is involved in the cell membrane association of this laminin binding protein and the cell surface. Interestingly, the released 67LR recovered after HPLC gel filtration was found free as well as associated to high molecular weight complexes. The free 67LR retained its ability to bind to the cell surface. Our study is the first demonstration that the 67LR is effectively shed by cancer cells. The released free 67LR could play an important role in modulating interactions between cancer cells and laminin during tumor invasion and metastasis.     

Intravitreous injections of vascular endothelial growth factor produce retinal ischemia and microangiopathy in an adult primate

PURPOSE: The purpose of the study is to determine the effect of exogenous vascular endothelial growth factor (VEGF) on the primate retina and its vasculature. METHODS: Ten eyes of five animals were studied. Physiologically relevant amounts of the 165 amino acid isoform of human recombinant VEGF were injected into the vitreous of six healthy cynomolgus monkey eyes. Inactivated human recombinant VEGF or vehicle was injected into four contralateral control subject eyes. Eyes were assessed by slit-lamp biomicroscopy, tonometry, fundus color photography, fundus fluorescein angiography, light microscopy, and immunostaining with antibodies against proliferating cell nuclear antigen and factor VIII antigen. RESULTS: All six bioactive VEGF-injected eyes developed dilated, tortuous retinal vessels that leaked fluorescein. Eyes receiving multiple injections of VEGF developed progressively dilated and tortuous vessels, venous beading, edema, microaneurysms, intraretinal hemorrhages and capillary closure with ischemia. The severity of the retinopathy correlated with the number of VEGF injections. None of the four control eyes exhibited any abnormal retinal vascular changes. The endothelial cells of retinal blood vessels were proliferating cell nuclear antigen positive only in the bioactive VEGF-injected eyes. CONCLUSION: Vascular endothelial growth factor is sufficient to produce many of the vascular abnormalities common to diabetic retinopathy and other ischemic retinopathies, such as hemorrhage, edema, venous beading, capillary occlusion with ischemia, microaneurysm formation, and intraretinal vascular proliferation.     

Overexpression of the 67-kD laminin receptor correlates with tumour progression in human colorectal carcinoma

The high affinity 67-kD laminin receptor (67LR) is a cell surface protein whose expression is increased in a number of human carcinoma models. To date, 67LR expression in colorectal carcinomas has been examined in a small number of cases. 67LR expression has been immunohistochemically analysed in a large series of human colorectal neoplasms, using the MLuC5 monoclonal antibody. The study included 59 samples of non-neoplastic mucosa, 45 polyps (11 hyperplastic, 34 adenomas), 196 carcinomas, and lymph node metastases of 87 carcinomas. Epithelial cells of normal mucosa and hyperplastic polyps were negative or showed weak positivity in the paranuclear and apical areas of the cytoplasm. In adenomas and carcinomas, the staining was stronger, with a membranous or cytoplasmic pattern. The expression of 67LR correlated significantly with the progression from normal mucosa (22 per cent) to adenoma (44 per cent), carcinoma (61 per cent), and lymph node metastasis (75 per cent) (P < 0.0001). Expression of the laminin receptor showed a tendency to be more frequently positive in advanced stage (III+IV; 67 (III+IV; 67 per cent) when compared with early stage (I+II) carcinomas (54 per cent). The difference, however, was not statistically significant (P = 0.058). In addition, 14 out of 28 (50 per cent) primary carcinomas without 67LR expression became positive in lymph node metastases, while most (86 per cent) of the MLuC5-positive primary carcinomas were also immunoreactive in metastases. In conclusion, these results indicate that 67LR is up-regulated in the progression of human colorectal carcinomas and may play a role in the local and metastatic progression of these tumours.     

Biogenesis of the purple membrane of Halobacterium halobium

In 168 eyes with preretinal membranes studied histopathologically, five major distinct types of membranes were categorized: 61 glial, 28 fibrous, 22 cortical vitreous, 16 retinal pigment epithelium, 15 fibroinflammatory, 24 combinations, and one endothelial and melanomatous membrane each. The overall prevalence of preretinal membranes was 5.5% in 2,000 cases studied. Selected cases examined by electron microscopy were supportive of the origin of the cells in the preretinal membranes in the glial, fibrous, and retinal pigment epithelial types. Glial preretinal membranes occurred as the result of defects in the internal limiting membrane, such as retinal pits or holes, and from the optic nerve head in association with posterior vitreous detachment. Fibrous preretinal membranes were associated with proliferative retinopathy and long-standing retinal detachment. Studies of the cellular origin of these membranes were inconclusive. The cortical vitreous type of preretinal membrane was hypocellular and occurred in the absence of associated ocular abnormalities. Pigment epithelial preretinal membranes occurred in eyes with rhegmatogenous retinal detachment.     

Expression of the 67-kD laminin receptor, galectin-1, and galectin-3 in advanced human uterine adenocarcinoma

Alterations of tumor cell interactions with laminin, a basement membrane glycoprotein, are consistent features of the invasive and metastatic phenotype. Qualitative and quantitative changes in the expression of cell surface laminin-binding proteins have been correlated with the ability of cancer cells to cross basement membranes during the metastatic cascade. Such phenotypic modifications are usually associated with poor prognosis. In this study, the authors examined the possibility that expression of three laminin-binding proteins, the 67-kD laminin receptor (67LR), galectin-1, and galectin-3, is altered in human endometrial cancer in a fashion similar to that reported in other carcinomas, such as breast, colon, and ovarian cancer. Twenty advanced uterine adenocarcinomas were analyzed for expression of these three molecules using immunoperoxidase staining and specific antibodies. The authors found a significant increase in the expression of the 67LR and galectin-1 in cancer cells compared with normal adjacent endometrium (P = .0004 and .0022, respectively). As observed in other carcinomas, a significant down-regulation of galectin-3 expression was found in endometrial cancer cells compared with normal mucosa (P = .02). In the galectin-3 positive tumors, galectin-3 was detected in the cytoplasm and/or nucleus of cancer cells. Interestingly, tumors in which galectin-3 was detected only in the cytoplasm were characterized by deeper invasion of the myometrium than lesions where galectin-3 was found both in nucleus and cytoplasm (P = .02). This study shows an alteration of nonintegrin laminin-binding protein expression in advanced human endometrial cancer. Further studies on larger populations should determine the prognostic value of the detection of these laminin-binding proteins in endometrial carcinoma. Inverse modulation of the 67LR and galectin-3 appears to be a phenotypical feature of invasive carcinoma.     

Infectious simian varicella virus expressing the green fluorescent protein

PURPOSE: To determine if vascular occlusion and nonperfusion is associated with the outer retinal atrophy, retinopathy, and choroidopathy (chorioretinopathy) that occurs in the alpha H beta S[beta MDD] and alpha H beta S [alpha MD beta MDD] transgenic mouse models of sickle cell disease. METHODS: Mice from the alpha H beta S[beta MDD] and alpha H beta S[alpha MD beta MDD] transgenic mouse lines that express high levels of human beta S globin were anesthetized and administered horseradish peroxidase (HRP) intracardially. After 1 min, the animals were sacrificed, and the retina from one eye was excised, fixed, and developed in diaminobenzidine (DAB). The contralateral eye was fixed, embedded whole in glycol methacrylate, and HRP developed in 2.5 microns sections. RESULTS: HRP reaction product (HRP-RP) and stained erythrocytes (RBCs) (due to endogenous peroxidase) were diffusely distributed within all vascular lumens in flatmount retinas from control animals (littermates homozygous for the mouse Beta Major deletion not expressing the beta S transgene). In 42.5% of the transgenic mice expressing beta S without any proliferative retinopathy, many blood vessels contained RBC plugs and lacked lumenal HRP-RP. In addition to packed RBCs, fibrin was sometimes present at sites of occlusion. In sections from whole eyes of the same animals, foci of photoreceptor degeneration were associated with areas of choriocapillaris nonperfusion (lumen that lacked HRP-PR). In areas with normal photoreceptors, the choriocapillaris appeared perfused (HRP-RP was present). In animals with proliferative chorioretinopathy, some neovascular formations lacked luminal HRP-RP, suggesting autoinfarction. CONCLUSIONS: Nonperfused retinal and choroidal vessels were observed in mice from the alpha H beta S[beta MDD] and alpha H beta S[alpha MD beta MDD] lines without retinal and choroidal neovascularization, whereas, all mice with neovascularization had nonperfused areas. Furthermore, small foci of PR loss were associated with areas of nonperfused choriocapillaris. These results suggest that sickle cell-mediated vaso-occlusions are an initial event in the chorioretinopathy and outer retinal atrophy that occurs in these models.     

Equity is out of fashion? An essay on autonomy and health policy in the individualized society

The 67-kDa laminin receptor (67LR) is a nonintegrin cell surface receptor that mediates high-affinity interactions between cells and laminin. Overexpression of this protein in tumor cells has been related to tumor invasion and metastasis. Thus far, only a full-length gene encoding a 37-kDa precursor protein (37LRP) has been isolated. The finding that the cDNA for the 37LRP is virtually identical to a cDNA encoding the ribosomal protein p40 has suggested that 37LRP is actually a component of the translational machinery, with no laminin-binding activity. On the other hand, a peptide of 20 amino acids deduced from the sequence of 37LR/p40 was shown to exhibit high laminin-binding activity. The evolutionary relationship between 23 sequences of 37LRP/p40 proteins was analyzed. This phylogenetic analysis indicated that all of the protein sequences derive from orthologous genes and that the 37LRP is indeed a ribosomal protein that acquired the novel function of laminin receptor during evolution. The evolutionary analysis of the sequence identified as the laminin-binding site in the human protein suggested that the acquisition of the laminin-binding capability is linked to the palindromic sequence LMWWML, which appeared during evolution concomitantly with laminin.     

TNF-alpha and IFN-gamma down-regulate the expression of the metastasis-associated bi-functional 37LRP/p40 gene and protein in transformed keratinocytes

The 37 LRP/p40 molecule is a bi-functional protein in which expression is increased in a large variety of cancers in association with their metastatic phenotype. Here we present the first data concerning the 37 LRP/p40 gene promoter activity and show that it is very active in a cervix carcinoma cell line. Interestingly, despite hallmarks of a housekeeping gene, we show that the 37 LRP/p40 gene promoter can be down-regulated by two potentially anticancerous cytokines, TNF-alpha and IFN-gamma. In addition, the dual fate of the protein, i.e., being intracellularly involved in the cell translation machinery and incorporated into a 67-kDa cell surface protein functioning as a laminin receptor (67LR), is differentially affected by the treatment. Our data suggest multiple regulation levels in the control of the 67LR/37LRP/p40 molecule expression and uncover new clues for the understanding of both the control of expression of this metastasis-associated molecule and the IFN-gamma and TNF-alpha anticancerous action.     

An aldose reductase inhibitor and aminoguanidine prevent vascular endothelial growth factor expression in rats with long-term galactosemia

OBJECTIVE: To study the effects of an aldose reductase inhibitor (ARI-509, Wyeth-Ayerst, Princeton, NJ) and aminoguanidine (AMG), agents that have been reported to prevent or delay diabetic retinopathy, on retinal vascular abnormalities and the immunocytochemical expression in the retina of vascular endothelial growth factor (VEGF) in rats maintained for up to 2 years on a 50% galactose diet. METHODS: Albino rats were placed on a control diet, a diet containing 50% galactose, or the 50% galactose diet containing either ARI-509 or AMG. Treatment with ARI-509 or AMG was initiated at the beginning of the experiment or after 12 months of galactose feeding. After 22 to 24 months, the rats were killed and the retinal vasculature from half of one eye was isolated by trypsin-elastase digestion for semiquantitative evaluation of retinal vascular lesions. The other half of the retina was prepared for immunocytochemistry and stained for the presence of VEGF, factor VIII, vimentin, and glial fibrillary acidic protein. Red blood cells, sciatic nerves, and a portion of the retina from the second eye were assayed for glucose, galactose, fructose, sorbitol, galactitol, and myo-inositol. Red blood cells were also assayed for galactosylated hemoglobin. RESULTS: Galactose-fed animals developed a vascular retinopathy characterized by severe cellular loss in the retinal capillaries and intensification of periodic acid-Schiff staining of the vascular basement membranes. Some animals also displayed dilation and hypercellularity of vessels in the posterior retina. These changes were substantially reduced in animals receiving ARI-509 from the beginning of the galactose diet, but were unaffected in all of the other treatment groups. None of the rats receiving ARI-509 or AMG treatment, whether initiated from the onset or after 12 months of galactosemia, demonstrated VEGF immunoreactivity. With the exception of the animals receiving ARI-509 from the beginning of the experiment, all of the galactose-fed animals developed dense cataracts within 6 weeks of the beginning of the galactose diet. Galactitol levels in animals receiving ARI-509 were 86% to 93% lower in red blood cells, retina, and sciatic nerve than those in the other galactose-fed groups. CONCLUSIONS: Although ARI-509 and AMG have different abilities to delay or prevent the diabetic-like retinopathy in galactosemic rats, even when substantial retinal microvascular acellularity occurs, both drugs prevent the immunocytochemical expression of VEGF. These results suggest that factors other than hypoxia may be responsible for VEGF expression in the retina, and that aldose reductase inhibitors and AMG have potential roles in preventing such expression and, thus, perhaps preventing retinal neovascularization.