Biomedical subjects

A M Joussen

Publications and source records attributed to A M Joussen.

42 records · Page 3Linked to original sources

PubMed1998

In vivo fluorescence microscopy of corneal neovascularization.

PURPOSE: The purpose of our study establish an animal model to study the microcirculation in corneal neovascularization in the living animal atraumatically. METHODS: Corneal neovascularization was induced in New Zealand white rabbits by a standard micropocket assay utilizing pellets with 250 ng basic fibroblast growth factor. Anesthesia consisted of intramuscular injections of ketamine and xylazine. Intravital microscopy was performed without preparation of the cornea. Rhodamine 6G was used as fluorescent dye to stain leukocytes. Fluorescein-isothiocyanate-dextran served as plasma marker. Microcirculation analysis was done off-line by digital video imaging with special analysis software and included the following parameters: vessel diameters, blood velocity, and differentiation of leukocytes according to their interaction with endothelium into free-floating. rolling and sticking leukocytes. RESULTS: Vessel diameters in venular trunk vessels showed diameters of 54.0 +/- 13.3 microns with 1.1 +/- 0.5 mm/s flow; 29.4 +/- 16.3% of all leukocytes were attached to the vascular wall. The number of sticking leukocytes was found to be 17.8 +/- 36.0 cells/mm endothelial surface. Values are given for arteriolar trunk and branch as well as venular branch vessels. CONCLUSIONS: This method for in vivo microscopic observation and quantification of the vasculature of the ocular surface seems to be suitable for evaluation of microhemodynamic and leukocyte measurements in mature neovascular vessels. It allows atraumatic experiments without corneal preparation procedures which disturb the microcirculation. The results concerning microhemodynamics and adherence of leukocytes are in a range comparable to other microcirculation studies. This new model could provide insight into the pathophysiology of microcirculatory disorders of the anterior eye segment, e.g. during angiogenesis.

Animals↗

PubMed1998

Thalidomide inhibits corneal angiogenesis induced by vascular endothelial growth factor.

BACKGROUND: Ocular diseases caused by neovascularization are among the leading causes of blindness. No specific pharmacological treatment is available. Among potential drugs, thalidomide deserves special interest since a wide body of clinical experience exists. However, its antiangiogenic effect is controversial. We therefore investigated the effect of thalidomide on corneal angiogenesis induced by vascular endothelial growth factor (VEGF), which has a special role among angiogenic growth factors. METHODS: Corneal neovascularization was induced in NZW rabbits by an intrastromal pellet loaded with 500 or 750 ng VEGF. Animals received two daily feedings of 200 mg/kg thalidomide. RESULTS: Significant inhibition of corneal angiogenesis (P < 0.0001) was caused by the teratogenic dose of thalidomide after the 5th day of treatment and persisted for more than 16 days. No obvious side effects were recorded. CONCLUSIONS: Thalidomide has a significant antiangiogenic effect against VEGF-induced neovasclar growth. Together with earlier findings this observation indicates that the drug inhibits two angiogenic pathways which are mediated through integrin adhesion molecules.

Administration, Oral↗

PubMed1997

[Inhibition of neovascularization of the eye by dietary factors exemplified by isoflavonoids].

UNLABELLED: Chronic malignant diseases with neovascularization sometimes seem to improve when an exclusively plant-based diet is followed. In order to identify antiangiogenic substances in such diets, inhibitory factors such as genistein were isolated. We investigated the antiangiogenic substance genistein with regard to the possibility of an inhibitory effect on corneal angiogenesis in vivo. METHODS: Corneal neovascularization was experimentally induced in NZW rabbits by the use of methylcellulose discs loaded with 250 ng basic fibroblast growth factor (bFGF). Blood vessels grew from the limbus towards the pellet and were quantified under the microscope. Genistein was injected subconjunctivally (0.04 mg genistein/day). RESULTS: All eyes which received genistein subconjunctivally showed a statistically significant reduction of blood vessels at the limbus (from 63 +/- 40 vessels to 36 +/- 11 vessels; P = 0.001). Vascularized areas in the eyes treated with genistein also decreased, from 21.4 +/- 6.7 mm2 to 10.4 +/- 5.0 mm2 (P < 0.0001). CONCLUSION: Our results show that components of a plant-based diet, such as genistein, inhibit ocular neovascularization in vivo. The genistein level rises significantly in human urine following ingestion of soy products, for example. Therefore, certain vegetarian diets could have a positive effect on ocular diseases characterized by progressive neovascularization.

Animals↗

PubMed1997

[Endogenous porphyrins for photodynamic therapy of cataracts in vitro].

UNLABELLED: Photodynamic therapy is based on accumulation of a photosensitizing substance in tissues and excitement by light of a suitable wavelength. Because of high levels of locally absorbed energy this process may also enable the selective destruction of proliferating lens epithelial cells. Delta-aminolaevulinic acid (ALA) is a natural precursor of hemoglobin. An accumulation of porphyrin derivates occurs following ingestion of ALA, of which one, protoporphyrin IX (P IX), is a potent photosensitizer. METHODS: Bovine lens epithelial cells were removed from the anterior lens capsule and cultivated in Waymouth/Ham's F12 (1:2) with 10% serum. Cells of an epithelial tumor cell line were cultivated. Cultures were incubated with various concentrations of ALA and irradiated with an argon-pulsed dye laser (630 nm). RESULTS: Fluorescence typical for porphyrin was detectable following incubation with 200 micrograms/ml ALA. Irradiation of such cultures with 10 J/cm2 resulted in death of the cells; 75% of the cells were lethally damaged at 3 J/cm2. Addition of P IX to the medium at a concentration of 50 micrograms/ml resulted in cell death at the low energy of 1 J/cm2. No lethal effect was observed following laser treatment without addition of ALA or P IX. DISCUSSION: Our results show for the first time that photodynamic destruction of lens epithelial cells can be achieved by a photosensitizer, which is the product of cellular metabolism.

Aminolevulinic Acid↗

PubMed1995

[Devitalization of lens epithelium cells by dye-enhanced therapy].

UNLABELLED: Hitherto secondary cataract has been usually treated by Nd:YAG laser, which results in a dissection of the capsule with possible complications e.g. retinal detachment. Selective removal of the epithelial cells from the posterior capsule has not been possible. By use of dyes in connection with laser light of a suitable wavelength, lens epithelial cells could potentially be selectively destroyed. We investigated the dye indocyanine green, which has a peak absorbtion at the emission wavelength of commercially available diode lasers. METHODS: Human lens epithelial cells and 3T3 cells (mouse embryonal fibroblasts) were grown in MEM with 10% FBS. Confluent and preconfluent layers were incubated with indocyanine green and treated with a diode laser attached to a slit lamp (810 nm, Zeiss VISULAS, Zeiss Oberkochen, Germany). RESULTS: Indocyanine green alone was toxic in concentrations above 5 mg/ml (60 min). Combined with laser treatment (200 mW, 100 ms, 160 microns), indocyanine green led to cell damage in preconfluent cultures at concentrations above 0.01 mg/ml (10 min). After about 2 days irradiated cells became necrotic and began to desquamate from the culture disc. Cells in confluent cultures could be devitalised at concentrations above 0.05 mg/ml (10 min) using the same power. In contrast, neither indocyanine green alone nor diode laser alone could interfere with epithelial proliferation. DISCUSSION: The experiments show the possibility of dye-enhanced therapy of lens epithelial cells with indocyanine green and diode laser. In contrast to other photosensitizers, indocyanine green is widely used in human function tests. Therefore its use for the treatment of secondary cataracts may merit discussion.

Cell Division↗

PubMedDate not supplied

Irradiation for inhibition of endothelial cell growth in vitro.

The clinical effect of ionising radiation on ocular neovascularisations is controversial, not only because of the variety of treatment modalities. The aim of our study was to investigate an experimental model which allows to evaluate radiation parameters and to study the mechanism of the inhibitory effect on neoangiogenesis. In vitro experiments were performed using human umbilical vein endothelial cells and human corneal keratocytes. The cells were irradiated with different doses of photon beam radiation and counted daily after treatment. Cell cultures confirmed the efficiency of irradiation in inhibiting proliferation of vascular endothelial cells. Radiosensitivity was shown to be higher in vascular endothelial cells than in corneal stromal keratocytes. This might be helpful in investigating therapy parameters for treating ocular neovascularisations, as well as underlying mechanisms.

Beta Particles↗