Abstract
Purpose: :
Tumor Necrosis Factor Related Apoptosis-Inducing Ligand (TRAIL) can induce apoptosis in various cell types, including endothelial cells (EC). Using TRAIL deficient (-/-) mice, we previously reported that TRAIL plays a role in regression of retinal neovascularization (NV) in the mouse model of oxygen-induced retinopathy (OIR) (Hubert KE, et al. IOVS 2008;49: ARVO E-Abstract 3295). The current study examines the role of TRAIL in the laser-induced model of choroidal neovascularization (CNV); an inflammatory cell mediated ocular neovascular process.
Methods: :
C57BL/6 (B6) and TRAIL -/- mice between 6 and 8 weeks old were used. Laser photocoagulation (532-nm argon green laser) was performed on both eyes of each mouse on day (D) 0. In all eyes, four laser spots were delivered to the retina through a slit lamp using a handheld contact lens. Eyes were enucleated on D7 and D14, one eye for whole mount analysis, the other for histopathologic studies. The extent of CNV was assessed in whole mounts from TRAIL-/- and B6 mice double labeled for isolectin IB4-Alexa Fluor-594 and a primary antibody against von Willabrand Factor (vWF) with an Alexa Fluor-488 secondary antibody. Whole mounts were imaged by confocal microscopy and analyzed with Image Pro Plus (n = 16 lesions/condition). Whole mounts were also immunostained for F4/80, a macrophage specific marker. CNV was qualitatively assessed in both vWF and H&E stained cross-sections.
Results: :
Quantitative analysis of CNV area demonstrated no significant difference between B6 mice and TRAIL-/- mice in both lectin-labeled and vWF-labeled RPE-chorodial flat-mounts at D7 or D14. Additionally, immunolabeling for F4/80 demonstrated the presence of numerous infiltrating macrophages in B6 and TRAIL-/- CNV lesions. The vWF-labeled sections and H&E sections displayed characteristic CNV lesions in the B6 and TRAIL-/- mice, without an appreciable difference in lesion size or severity of NV.
Conclusions: :
In summary, while the absence of TRAIL altered the neovascular response in the OIR model of retinal NV, TRAIL does not appear to play a role in the laser-induced mouse model of CNV. Compared to B6 mice, TRAIL-/- mice showed similar CNV lesion area at both 7 and 14 days post laser photocoagulation. Differences in the vascular response observed between the OIR and CNV model in the TRAIL-/- mice may relate to the temporal and functional differences between infiltrating macrophages in the OIR and laser-induced CNV models
Keywords: neovascularization • choroid: neovascularization • apoptosis/cell death