Blood-brain barrier integrity is unaltered. in human brain cortex with diabetes mellitus

Diabetes-related cognitive dysfunction has been recognized for many years in humans, but the pathogenesis of this condition is poorly understood. Evidence from animal studies suggests that altered function of the blood-brain barrier (BBB) could be a potential cause contributing to this disease. This study aimed to investigate whether, the permeability of the BBB is affected in the brains of persons with diabetes mellitus (DM). On postmortem prefrontal and temporal cortex of diabetic patients and controls, immunohistochemical stainings were carried out using specific antibodies against three proteins (PAL-E, IgG and albumin), which are considered as markers for the vascular permeability status of the BBB. Rare or no PAL-E staining was found in the capillaries of the prefrontal and temporal cortex parenchyma, in both DM and control materials. IgG and albumin were localized in and directly around blood vessel walls in the prefrontal and temporal cortex. No obvious difference's in the staining pattern of IgG and albumin were observed between brain samples of persons with DM and controls. This study suggests that the BBB in diabetic patients is well maintained. (C) 2002 Elsevier Science B.V. All rights reserve

Expression of vascular endothelial growth factor receptors 1, 2, and 3 in quiescent endothelia

The vascular endothelial growth factor (VEGF) family is involved in angiogenesis, and therefore VEGFs are considered as targets for anti-angiogenic therapeutic strategies against cancer. However, the physiological functions of VEGFs in quiescent tissues are unclear and may interfere with such systemic therapies. In pathological conditions, increased levels of expression of the VEGF receptors VEGFR-1, VEGFR-2, and VEGFR-3 accompany VEGF activity. In this study we investigated normal human and monkey tissues for expression patterns of these receptors. Immunohistochemical staining methods at the light and electron microscopic level were applied to normal human and monkey tissue samples, using monoclonal antibodies (MAbs) against the three VEGFRs and anti-endothelial MAbs PAL-E and anti-CD31 to identify blood and lymph vessels. In human and monkey, similar distribution patterns of the three VEGFRs were found. Co-expression of VEGFR-1, -2, and -3 was observed in microvessels adjacent to epithelia in the eye, gastrointestinal mucosa, liver, kidney, and hair follicles, which is in line with the reported preferential expression of VEGF-A in some of these epithelia. VEGFR-1, -2, and -3 expression was also observed in blood vessels and sinusoids of lymphoid tissues. Furthermore, VEGFR-1, but not VEGFR-2 and -3, was present in microvessels in brain and retina. Electron microscopy showed that VEGFR-1 expression was restricted to pericytes and VEGFR-2 to endothelial cells in normal vasculature of tonsils. These findings indicate that VEGFRs have specific distribution patterns in normal tissues, suggesting physiological functions of VEGFs that may be disturbed by systemic anti-VEGF therapy. One of these functions may be involvement of VEGF in paracrine relations between epithelia and adjacent capillarie

In vivo angiogenic phenotype of endothelial cells and pericytes induced by vascular endothelial growth factor-A

VEGF-A is a major angiogenesis and permeability factor. Its cellular effects, which can be used as targets in anti-angiogenesis therapy, have mainly been studied in vitro using endothelial cell cultures. The purpose of the present study was to further characterize these effects in vivo in vascular endothelial cells and pericytes, in an experimental monkey model of VEGF-A-induced iris neovascularization. Two cynomolgus monkeys (Macaca fascicularis) received four injections of 0.5 mug VEGF-A in the vitreous of one eye and PBS in the other eye. After sacrifice at day 9, eyes were enucleated and iris samples were snap-frozen for immunohistochemistry (IHC) and stained with a panel of antibodies recognizing endothelial and pericyte determinants related to angiogenesis and permeability. After VEGF-A treatment, the pre-existing iris vasculature showed increased permeability, hypertrophy, and activation, as demonstrated by increased staining of CD31, PAL-E, tPA, uPA, uPAR, Glut-1, and alpha(v)beta(3) and alpha(v)beta(5) integrins, VEGF receptors VEGFR-1, -2 and -3, and Tie-2 in endothelial cells, and of NG2 proteoglycan, uPA, uPAR, integrins and VEGFR-1 in pericytes. Vascular sprouts at the anterior surface of the iris were positive for the same antigens except for tPA, Glut-1, and Tie-2, which were notably absent. Moreover, in these sprouts VEGFR-2 and VEGFR-3 expression was very high in endothelial cells, whereas many pericytes were present that were positive for PDGFR-P, VEGFR-1, and NG2 proteoglycan and negative for alpha-SMA. In conclusion, proteins that play a role in angiogenesis are upregulated in both pre-existing and newly formed iris vasculature after treatment with VEGF-A. VEGF-A induces hypertrophy and loss of barrier function in pre-existing vessels, and induces angiogenic sprouting, characterized by marked expression of VEGFR-3 and lack of expression of tPA and Tie-2 in endothelial cells, and lack of alpha-SMA in pericytes. Our in vivo study indicates a role for alpha-SMA-negative pericytes in early stages of angiogenesis. Therefore, our findings shed new light on the temporal and spatial role of several proteins in the angiogenic cascade in viv

Argon laser lesions of the rabbit iris: Quantitative aspects

The destructive effect of nonperforating argon laser coagulations in the brown irides of rabbits was studied with quantitative histological methods. Power, spot size, and exposure time were systematically varied. The lateral and axial extensions of the crater and the denaturation of the adjacent tissue were studied. The main conclusions are: (1) the extent of tissue damage is significantly correlated with power and spot size, though the correlation is not proportional; (2) the lateral extension of the tissue reaction is far more pronounced than the axial extension; (3) increase in exposure time is effective up to 0.2 s, though a further increase up to 0.5 s does not enhance the tissue reaction. It is discussed that for conventionally switched lasers the main determinant for the final extension of the lesion is the density and distribution of the pigment granules within the iris. The radial distribution of the protrusions of the melanocytes in brown irides of the rabbits used in this study favors the lateralization of the tissue reaction. The nonlinearity of the tissue reaction and exposure time might be due to the fact that after initial damage in early phases of irradiation (e.g. up to 50 or 100 ms, the absorbed laser energy is dissipated in already destroyed tissue. Some practical aspects for iridectomy are discussed. © 1982 Springer-Verlag GmbH & Co. KG, Berlin Heidelberg.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Proprietary interest category: N. Reprint requests: I. Michael Wormstone, School of Biological Sciences

Purpose. The ocular humors are relatively low in protein, yet cell growth in the human capsular bag still occurs after extracapsular cataract extraction (ECCE) surgery. This resilient growth gives rise to posterior capsule opacification (PCO) in a significant proportion (30%) of patients. This study compared the ability of human lens cells to proliferate in serum-supplemented and protein-free medium. Methods. Sham cataract operations were performed on human donor eyes. The capsular bag was dissected free, pinned flat on a petri dish, and incubated in Eagle's minimal essential medium (EMEM) alone or in EMEM supplemented with 10% fetal calf serum. Observations were made by phase-contrast microscopy. At the endpoint, capsules were studied by fluorescence or electron microscopy. Mitotic activity was identified using Bromo-2-deoxyuridine labeling and detection techniques. When required, an intraocular lens was implanted when surgery was performed. Results. It was found that human lens cells from a wide age spectrum of donors proliferate and migrate on the lens capsule in the absence of added protein. The rate of growth was age-dependent, such that the posterior capsule was completely confluent after 8.0 ± 0 days (n = 3) and 24.4 ± 5.3 days (n = 8) for donor lenses aged <40 years and >60 years, respectively. The outgrowth of epithelial cells gave rise to capsular contraction, wrinkling, and increased light scatter. Growth on the anterior surface of the intraocular lens was less prolific than on the posterior capsule. Conclusion. The protein-free model replicates many features of clinically-observed PCO. The resilient cell growth on the natural collagen capsule explains the high prevalence of PCO, especially in younger patients, and suggests that inflammation and external growth factors are not necessary for PCO. Furthermore, the protein-free capsular bag system can be used to explore fundamental questions concerning the autocrine control of lens epithelial cell survival and growth. Invest Ophthalmol Vis Sci. 1997; 38:396-404. .Despite improvements in surgical techniques, posterior capsule opacification (PCO) remains a major problem associated with extracapsular cataract extraction (ECCE) surgery that requires further treatment in approximately 30% to 50% of patients. PCO arises from the growth of lens epithelial cells remaining o

Altered expression patterns of VEGF receptors in human diabetic retina and in experimental VEGF-induced retinopathy in monkey

PURPOSE. The vascular endothelial growth factor (VEGF) family is involved in vascular leakage and angiogenesis in diabetic retinopathy (DR) in the eye, but may also have physiological functions. Based on the hypothesis that differential VEGF receptor (VEGFR) expression in the retina is an important determinant of effects of VEGF, this study was conducted to investigate VEGFR expression in the diabetic retina and in an experimental monkey model of VEGF-A-induced retinopathy. METHODS. In retinas of 27 eyes of diabetic donors, 18 eyes of nondiabetic control donors, and 4 monkey eyes injected with PBS or VEGF-A, expression patterns of VEGFR-1, -2, and -3 in relation to leaky microvessels, as identified by the marker pathologische anatomie Leiden-endothelium (PAL-E) were studied by, immunohistochemistry. RESULTS. In control human retinas and retinas of PBS-injected monkey eyes, all three VEGFRs were expressed in nonvascular areas, but only VEGFR-1 was constitutively expressed in retinal microvessels. In diabetic eyes, increased microvascular VEGFR-2 expression was found in association with PALE expression, whereas microvascular VEGFR-3 was present in a subset of PAL-E-positive cases. In VEGF-A-injected monkey eyes, VEGFR-1, -2, and -3 and PAL-E were expressed in retinal microvessels. CONCLUSIONS. The VEGFR-1, -2, and -3 expression patterns in control retinas suggest physiological functions of VEGFs that do not involve the vasculature. Initial vascular VEGF signaling may act primarily through VEGFR-1. In diabetic eyes, expression of retinal VEGFR-2 and -3 is increased, mainly in leaky microvessels, and VEGF-A induces vascular expression of the VEGF-A receptor VEGFR-2 and the VEGF-C/D receptor VEGFR-3. These findings indicate a dual role of VEGFs in the physiology and pathophysiology of the retina and suggest that microvascular VEGFR-2 and -3 signaling by VEGFs occurs late in the pathogenesis of DR, possibly initiated by high levels of VEGF-A in established nonproliferative D