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Selwyn Marc Prea, Guei-Sheung Liu, Gregory James Dusting, Algis J Vingrys, Bang V Bui; Investigating the laser model of experimental choroidal neovascularization in Long Evans rats. Invest. Ophthalmol. Vis. Sci. 2016;57(12):2139.
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© ARVO (1962-2015); The Authors (2016-present)
The aim of this study was to determine the minimum laser energy required to successfully breach Bruch’s membrane (BM) in Long Evans rats and to assay the inflammatory and angiogenic changes following laser application.
Adult (30 weeks) Long Evans rats were anaesthetised (60:5 mg/kg ketamine:xylazine) and six laser burns (Nd:YAG) of varying energy (2.0 to 10.2 J/mm2) were delivered to the posterior pole of each eye (n = 4 rats). A dose response was established for breach as a function of laser energy. Spectral domain-optical coherence tomography (SD-OCT) was performed at 5 min, 14 days and 28 days after laser and compared against histological findings made at 28 days. Changes in mRNA with qPCR were determined for tumour necrosis factor-alpha (TNF-α) and vascular endothelial growth factor-A (VEGF-A) 2 days after high dose (5.10 J/mm2) laser (n = 6 eyes) that invoked breach of BM. Rats were sacrificed at 28 days and choroidal wholemounts were stained with isolectin B4 and von Willebrand Factor. Confocal microscopy was used to determine if a choroidal neovascular (CNV) membrane was present with IB4 and vWF staining. All group data are shown as mean [95% CLs].
The dose response found that the amount of laser energy required to breach BM (95% success) was 3.12 J/mm2 [3.01, 3.29]. Rupture of BM with high laser energy (5.10 J/mm2) resulted in immediate ablation of the retinal pigment epithelium viewed with SD-OCT at 5 mins. CNV was not observed in these lesions at 28 days although macrophages were present at 10 µm above the choriocapillaris. Elevated levels of TNF-α mRNA were detected in the retina (9.7 fold increase, p<0.001) and choroid (2 fold increase, p<0.05) at 2 days post laser. However, a downregulation of VEGF-A mRNA was found in the retina (1.2 fold decrease, p<0.05) and choroid (1.6 fold decrease, p<0.01) 2 days after laser.
The minimum energy to successfully breach BM in Long Evans rats was 3.12 J/mm2 [3.01, 3.29] which was visualised by SD-OCT. In the presence of breach, we found upregulation in TNF-α and a downregulation of VEGF-A.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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