An experimental study on choroidal neovascularization induced by Krypton laser in rat model

Newly Identified Peptide, Peptide Lv, Promotes Pathological Angiogenesis

Background We recently discovered a small endogenous peptide, peptide Lv, with the ability to activate vascular endothelial growth factor receptor 2 and its downstream signaling. As vascular endothelial growth factor through vascular endothelial growth factor receptor 2 contributes to normal development, vasodilation, angiogenesis, and pathogenesis of various diseases, we investigated the role of peptide Lv in vasodilation and developmental and pathological angiogenesis in this study. Methods and Results The endothelial cell proliferation, migration, and 3-dimensional sprouting assays were used to test the abilities of peptide Lv in angiogenesis in vitro. The chick chorioallantoic membranes and early postnatal mice were used to examine its impact on developmental angiogenesis. The oxygen-induced retinopathy and laser-induced choroidal neovascularization mouse models were used for in vivo pathological angiogenesis. The isolated porcine retinal and coronary arterioles were used for vasodilation assays. Peptide Lv elicited angiogenesis in vitro and in vivo. Peptide Lv and vascular endothelial growth factor acted synergistically in promoting endothelial cell proliferation. Peptide Lv-elicited vasodilation was not completely dependent on nitric oxide, indicating that peptide Lv had vascular endothelial growth factor receptor 2/nitric oxide-independent targets. An antibody against peptide Lv, anti-Lv, dampened vascular endothelial growth factor-elicited endothelial proliferation and laser-induced vascular leakage and choroidal neovascularization. While the pathological angiogenesis in mouse eyes with oxygen-induced retinopathy was enhanced by exogenous peptide Lv, anti-Lv dampened this process. Furthermore, deletion of peptide Lv in mice significantly decreased pathological neovascularization compared with their wild-type littermates. Conclusions These results demonstrate that peptide Lv plays a significant role in pathological angiogenesis but may be less critical during development. Peptide Lv is involved in pathological angiogenesis through vascular endothelial growth factor receptor 2-dependent and -independent pathways. As anti-Lv dampened the pathological angiogenesis in the eye, anti-Lv may have a therapeutic potential to treat pathological angiogenesis.

Intravitreal Stanniocalcin-1 Enhances New Blood Vessel Growth in a Rat Model of Laser-Induced Choroidal Neovascularization

Purpose

The purpose of this study was to investigate the impact of stanniocalcin-1 (STC-1), a photoreceptor-protective glycoprotein, on the development of choroidal neovascularization (CNV) in relation to VEGF and its main receptor (VEGFR2) expression after laser injury.

Methods

In rats, CNV was induced by laser photocoagulation in both eyes, followed by intravitreal injection of STC-1 in the right eye and vehicle or denatured STC-1 injection in the left eye as control. Two weeks after laser injury, fundus autofluorescence (FAF) imaging and fundus fluorescein angiography (FFA) were performed. Fluorescein leakage from CNV was graded using a defined scale system. The size of CNV was quantified with spectral domain optical coherence tomography (SD-OCT), fluorescein-labeled choroid-sclera flat mounts, and hematoxylin-eosin staining. Protein expressions were evaluated by Western blot.

Results

Photocoagulation produced a well-circumscribed area of CNV. With STC-1 treatment, CNV lesions assessed by FAF were increased by 50% in both intensity and area. The CNV lesions were also increased with SD-OCT, flat-mount, and histologic analyses. FFA disclosed enhanced fluorescein leakage in CNV lesions in STC-1 treated eyes. The STC-1 protein was detected in the choroidal tissue and its level was increased with CNV lesions in correlation with VEGF and VEGFR2 expressions. Intravitreal administration of STC-1 significantly increased choroidal expression of both VEGF and VEGFR2 proteins.

Conclusions

Chorodial tissue expresses STC-1, which seemingly acts as a stress response protein by enhancing pathological new blood vessel growth in laser-induced CNV. It is likely that STC-1 promotes CNV development via VEGF signaling.

Inhibition of Laser-Induced Choroidal Neovascularization by Hematoporphyrin Dimethylether-Mediated Photodynamic Therapy in Rats

This study aimed to investigate the effect of hematoporphyrin dimethylether (HDME)-mediated photodynamic therapy for laser-induced choroidal neovascularization (CNV) in adult Brown Norway rats. HDME was administered via tail vein at 14 d after the laser photocoagulation, and the rats received irradiance with a laser light at 570 nm at 15 min after injection. CNV was evaluated by fundus photography, fundus fluorescein angiography, optical coherence tomography, and hematoxylin and eosin staining. We found that CNV was occurred at 7 d after photocoagulation and reaching peak activity at 14 d after photocoagulation. There is a significant reduction in the total area of the fluorescein leakage and the number of strong fluorescein leakage spots on 7 d after HDME-mediated photodynamic therapy (PDT). The results suggest that HDME-mediated PDT inhibits laser-induced CNV in rats, representing a promising therapy for wet age-related macular degeneration.

A Quantitative and Standardized Method for the Evaluation of Choroidal Neovascularization Using MICRON III Fluorescein Angiograms in Rats

Introduction

In-vivo imaging of choroidal neovascularization (CNV) has been increasingly recognized as a valuable tool in the investigation of age-related macular degeneration (AMD) in both clinical and basic research applications. Arguably the most widely utilised model replicating AMD is laser generated CNV by rupture of Bruch’s membrane in rodents. Heretofore CNV evaluation via in-vivo imaging techniques has been hamstrung by a lack of appropriate rodent fundus camera and a non-standardised analysis method. The aim of this study was to establish a simple, quantifiable method of fluorescein fundus angiogram (FFA) image analysis for CNV lesions.

Methods

Laser was applied to 32 Brown Norway Rats; FFA images were taken using a rodent specific fundus camera (Micron III, Phoenix Laboratories) over 3 weeks and compared to conventional ex-vivo CNV assessment. FFA images acquired with fluorescein administered by intraperitoneal injection and intravenous injection were compared and shown to greatly influence lesion properties. Utilising commonly used software packages, FFA images were assessed for CNV and chorioretinal burns lesion area by manually outlining the maximum border of each lesion and normalising against the optic nerve head. Net fluorescence above background and derived value of area corrected lesion intensity were calculated.

Results

CNV lesions of rats treated with anti-VEGF antibody were significantly smaller in normalised lesion area (p<0.001) and fluorescent intensity (p<0.001) than the PBS treated control two weeks post laser. The calculated area corrected lesion intensity was significantly smaller (p<0.001) in anti-VEGF treated animals at 2 and 3 weeks post laser. The results obtained using FFA correlated with, and were confirmed by conventional lesion area measurements from isolectin stained choroidal flatmounts, where lesions of anti-VEGF treated rats were significantly smaller at 2 weeks (p = 0.049) and 3 weeks (p<0.001) post laser.

Conclusion

The presented method of in-vivo FFA quantification of CNV, including acquisition variable corrections, using the Micron III system and common use software establishes a reliable method for detecting and quantifying CNV enabling longitudinal studies and represents an important alternative to conventional CNV quantification methods.