Hypoxia-Inducible Factor-1α Is Associated With Sprouting Angiogenesis in the Murine Laser-Induced Choroidal Neovascularization Model

Abstract

PURPOSE: To investigate the expression and distribution of neoangiogenic molecules and the role of hypoxia during the development of experimental choroidal neovascularization (CNV). METHODS: Lesions were induced on C57Bl6 mice using laser photocoagulation. Animals were euthanized in a timely manner and eyecups were dissected from enucleated eyes. Choroids were immunostained for pericytes, sprouting endothelial cells (EC), or vascular EC. Choroidal neovascularization lesions where analyzed for tissue hypoxia, hypoxia-inducible factors (HIF), and heat-shock proteins (HSP). RESULTS: Choroidal neovascularization lesions showed a trend of increased cellular recruitment throughout the time-course and the lesions displayed positive staining for angiogenic markers. Both pericytes and sprouting EC displayed a radial progression, while vascular EC displayed a more uniform distribution across the CNV lesions. Furthermore, positive tissue hypoxia staining was observed and associated with expression of HIF-1α and vascular endothelial growth factor (VEGF). CONCLUSIONS: Our data delimitate specific temporal windows during CNV initiation, propagation, maturation, and even recovery in experimental CNV. We show that murine CNV undergoes hypoxia-associated sprouting angiogenesis, and demonstrate involvement of pericytes. Moreover, we have shown expression of HIF-1α to the retinal pigment epithelium surrounding the CNV lesions, together with VEGF upregulation, independently of the HSP response induced by the laser thermal insult.