Ingeborg Stalmans

Impaired myocardial angiogenesis and ischemic cardiomyopathy in mice lacking the vascular endothelial growth factor isoforms VEGF164 and VEGF188.

Impaired myocardial angiogenesis and ischemic cardiomyopathy in mice lacking the vascular endothelial growth factor isoforms VEGF 164 and VEGF 188

Arteriolar and venular patterning in retinas of mice selectively expressing VEGF isoforms

The murine VEGF gene is alternatively transcribed to yield the VEGF(120), VEGF(164), and VEGF(188) isoforms, which differ in their potential to bind to heparan sulfate and neuropilin-1 and to stimulate endothelial growth. Here, their role in retinal vascular development was studied in mice selectively expressing single isoforms. VEGF(164/164) mice were normal, healthy, and had normal retinal angiogenesis. In contrast, VEGF(120/120) mice exhibited severe defects in vascular outgrowth and patterning, whereas VEGF(188/188) mice displayed normal venular outgrowth but impaired arterial development. It is noteworthy that neuropilin-1, a receptor for VEGF(164), was predominantly expressed in retinal arterioles. These findings reveal distinct roles of the various VEGF isoforms in vascular patterning and arterial development in the retina.

VEGF : A modifier of the del22q11 (DiGeorge) syndrome?

Hemizygous deletion of chromosome 22q11 (del22q11) causes thymic, parathyroid, craniofacial and life-threatening cardiovascular birth defects in 1 in 4,000 infants. The del22q11 syndrome is likely caused by haploinsufficiency of TBX1, but its variable expressivity indicates the involvement of additional modifiers. Here, we report that absence of the Vegf164 isoform caused birth defects in mice, reminiscent of those found in del22q11 patients. The close correlation of birth and vascular defects indicated that vascular dysgenesis may pathogenetically contribute to the birth defects. Vegf interacted with Tbx1, as Tbx1 expression was reduced in Vegf164-deficient embryos and knocked-down vegf levels enhanced the pharyngeal arch artery defects induced by tbx1 knockdown in zebrafish. Moreover, initial evidence suggested that a VEGF promoter haplotype was associated with an increased risk for cardiovascular birth defects in del22q11 individuals. These genetic data in mouse, fish and human indicate that VEGF is a modifier of cardiovascular birth defects in the del22q11 syndrome.

Further pharmacological and genetic evidence for the efficacy of PlGF inhibition in cancer and eye disease.

Our findings that PlGF is a cancer target and anti-PlGF is useful for anticancer treatment have been challenged by Bais et al. Here we take advantage of carcinogen-induced and transgenic tumor models as well as ocular neovascularization to report further evidence in support of our original findings of PlGF as a promising target for anticancer therapies. We present evidence for the efficacy of additional anti-PlGF antibodies and their ability to phenocopy genetic deficiency or silencing of PlGF in cancer and ocular disease but also show that not all anti-PlGF antibodies are effective. We also provide additional evidence for the specificity of our anti-PlGF antibody and experiments to suggest that anti-PlGF treatment will not be effective for all tumors and why. Further, we show that PlGF blockage inhibits vessel abnormalization rather than density in certain tumors while enhancing VEGF-targeted inhibition in ocular disease. Our findings warrant further testing of anti-PlGF therapies.

Inhibition of Vascular Endothelial Growth Factor Reduces Scar Formation after Glaucoma Filtration Surgery

PURPOSE Filtration failure due to excessive postoperative scarring remains a major problem after glaucoma surgery. The authors have investigated whether glaucoma and filtration surgery are associated with increased levels of vascular endothelial growth factor (VEGF), and whether a humanized monoclonal antibody against VEGF, bevacizumab, can reduce postoperative scar formation and improve surgical outcome. METHODS The levels of VEGF in samples of aqueous humor were measured by ELISA. The expression of the VEGF receptors Flt-1 and KDR was analyzed in cultured Tenon fibroblasts by real-time RT-PCR and Western blotting. The effect of VEGF and bevacizumab on Tenon fibroblasts in vitro was determined using a proliferation assay. The in vivo effect of the antibody was investigated in a rabbit model of trabeculectomy by measuring the intraocular pressure (IOP) and bleb area, and by immunohistological analysis of angiogenesis, inflammation, and fibrosis. RESULTS VEGF levels were increased significantly in the aqueous humor of glaucoma patients and rabbits that had undergone surgery. Both VEGF receptors were expressed on Tenon fibroblasts. Fibroblast proliferation in vitro was stimulated by delivery of VEGF, and was inhibited by administration of bevacizumab. The antibody also reduced angiogenesis and collagen deposition significantly, and improved the outcome of glaucoma surgery in rabbits. CONCLUSIONS VEGF was upregulated in the aqueous humor of glaucoma patients and in the rabbit model, and it stimulated fibroblast proliferation in vitro. This suggests that it is involved in the scarring process after filtration surgery. Bevacizumab reduced the proliferation of fibroblasts in vitro and improved surgical outcome.

Safe trabeculectomy technique: long term outcome

Aim: To assess the long term outcome of a new trabeculectomy technique. Methods: Trabeculectomy was performed using a fornix based conjunctival flap, an anterior chamber maintainer, a standardised punch technique, and a combination of adjustable and releasable sutures in 56 eyes of 53 patients. The main outcome measures were the postoperative intraocular pressure (IOP) and the frequency of early postoperative complications. The mean follow up time was 15.7 (range 12–21) months. Results: The mean preoperative and postoperative IOP at 12 months were 21.2 (SD 6) and 12.8 (3.0) mm Hg, respectively. All patients had an IOP of <21 mm Hg, 90.9% had an IOP <18 mm Hg, and 61.4% had an IOP <14 mm Hg. Postoperative complications were infrequent: flat anterior chamber (1.8%), bleb leakage (0%), or hypotony (1.5%) beyond 3 weeks, or choroidal detachment at any time point (8.9%). Conclusions: This novel trabeculectomy method offers the possibility to tailor the IOP postoperatively with a minimum of postoperative complications and excellent IOP control at the long term follow up.

Ocular perfusion pressure in glaucoma

This review article discusses the relationship between ocular perfusion pressure and glaucoma, including its definition, factors that influence its calculation and epidemiological studies investigating the influence of ocular perfusion pressure on the prevalence, incidence and progression of glaucoma. We also list the possible mechanisms behind this association, and discuss whether it is secondary to changes in intraocular pressure, blood pressure or both. Finally, we describe the circadian variation of ocular perfusion pressure and the effects of systemic and topical medications on it. We believe that the balance between IOP and BP, influenced by the autoregulatory capacity of the eye, is part of what determines whether an individual will develop optic nerve damage. However, prospective, longitudinal studies are needed to better define the role of ocular perfusion pressure in the development and progression of glaucoma.

Use of colour Doppler imaging in ocular blood flow research.

The main objective of this report is to encourage consistent quality of testing and reporting within and between centres that use colour Doppler imaging (CDI) for assessment of retrobulbar blood flow. The intention of this review is to standardize methods in CDI assessment that are used widely, but not to exclude other approaches or additional tests that individual laboratories may choose or continue to use.

Oximetry in glaucoma: correlation of metabolic change with structural and functional damage

Purpose:  To determine whether retinal vessel oxygen saturation in patients with glaucoma is associated with structural optic disc and retinal nerve fibre layer (RNFL) changes and visual field (VF) defects.

Trypan blue not toxic for retinal pigment epithelium in vitro.

PURPOSE To investigate whether trypan blue has a toxic effect on cultured retinal pigment epithelial (retinal pigment epithelium) cells. DESIGN Experimental study with a direct live/dead cell staining technique using fluorescent dyes. METHODS Cultured human retinal pigment epithelium cells were exposed for 5 minutes to various concentrations of trypan blue (0.06%, 0.15%, 0.30%), and cell viability was confocally measured. RESULTS No increased cell death was found in cultures incubated in any of the trypan blue concentrations used. CONCLUSION These findings indicate that a short exposure of trypan blue does not have a toxic effect on cultured retinal pigment epithelium cells.