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

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-1 alpha 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-1 alpha to the retinal pigment epithelium surrounding the CNV lesions, together with VEGF upregulation, independently of the HSP response induced by the laser thermal insult.