Investigation of laser-induced choroidal neovascularization in the rat.
OBJECTIVE
Choroidal neovascularization plays an important role in pathogenesis of age-related macular degeneration. Induction of neovascularization by laser photocoagulation in the rat fundus is an established animal model in which the effects of new therapeutic approaches are assessed. The purpose of this study was to compare different detection methods of laser-induced neovascularization in the rat.


METHODS
Laser spots were applied to the fundus of Long-Evans rats. Ten days after, four different methods were used to detect laser-induced neovascularization: (1) high-resolution angiography with fluorescein isothiocyanate-dextran, (2) immunohistochemical visualization of platelet endothelial cell adhesion molecule (PECAM)-1, (3) visualization of intravascular lumens by peroxidase perfusion in the living rat with subsequent histologic analysis, and (4) histochemical representation of alkaline phosphatase in endothelial cells.


RESULTS
At the rim of the laser scars vessel-forming endothelial cells with intravasal dextran and peroxidase were present. Cross-sections demonstrated that these vessels originated from the retina. The center of the scars contained homogenous endothelial cells of choroidal origin, which was confirmed by immunohistochemistry and electron microscopy. In laser-treated eyes without FITC-dextran perfusion, scars showed unspecific fluorescence, making differentiation from specific FITC-dextran-associated fluorescence difficult.


CONCLUSIONS
In the rat model of laser-induced neovascularization, newly developed endothelial cells originate from the retina and the choroid. Whereas ring-like surrounding vessels come from the retina, flat endothelial cells in deeper layers are of choroidal origin or may originate from circulating endothelial precursor cells. Dextran angiography has to be regarded critically for visualizing the choriocapillaris and CNV in laser scars. PECAM-1 immunohistochemistry is best for detection and quantification of neovascularization in laser scars.
Semkova
Irina
I
Division of Gene Therapy, University of Ulm, Ulm, Germany. irina.semkova@medizin.uni-koeln.de
Peters
Swaantje
S
Welsandt
Gerhard
G
Janicki
Hanna
H
Jordan
Jens
J
Schraermeyer
Ulrich
U
D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D002829:Choroid / Q000098:blood supply* / Q000473:pathology; D020256:Choroidal Neovascularization / Q000175:diagnosis* / Q000209:etiology; D003911:Dextrans; D004195:Disease Models, Animal; D004730:Endothelium, Vascular / Q000378:metabolism / Q000473:pathology*; D005451:Fluorescein Angiography / Q000379:methods; D016650:Fluorescein-5-isothiocyanate / Q000031:analogs & derivatives*; D019084:Fluorescent Antibody Technique, Indirect; D006735:Horseradish Peroxidase / Q000378:metabolism; D007124:Immunoenzyme Techniques; D017075:Laser Coagulation / Q000009:adverse effects*; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000378:metabolism; D051381:Rats; D020318:Rats, Long-Evans
D003911:Dextrans; D019408:Platelet Endothelial Cell Adhesion Molecule-1; C015219:fluorescein isothiocyanate dextran; D006735:Horseradish Peroxidase; D000469:Alkaline Phosphatase; D016650:Fluorescein-5-isothiocyanate