Abstract
Purpose: :
Endothelial Progenitor Cells (EPCs) are found in experimental mouse CNV and late outgrowth endothelial progenitor cells (OECs) are increased in peripheral blood of patients with neovascular AMD. Systemic injection of cytokines such as VEGF can induce mobilization of EPCs. Mechanisms governing EPC mobilization in neovascular AMD are unkown.
Methods: :
8-week old wild-type mice were treated with diode laser to induce experimental CNV. Human serum albumin nanoparticles (NPs) of 100 nm size were prepared and VEGF or Stromal-Cell derived factor-1 (SDF-1) alpha was adsorbed on the developed NPs by an ionic bond. Mice were injected intravitreally with control, VEGF- or SDF-1-NPs alone or after laser treatment. Venous blood was collected at 24 hours, 3 and 7 days and peripheral blood mononuclear cells (PBMNCs) were separated by Ficoll density gradient centrifugation. PBMNCs were stained with PE- and FITC- conjugated antibodies against flk-1 and CD34 and analyzed by FACS. Mice were sacrificed at day 14 and eyes were enucleated for quantification of CNV area.
Results: :
A significant increase in flk-1+/CD34+ cells was observed in blood of laser-treated mice at day 7 compared to untreated control. In mice injected intraocularly with VEGF-NPs, frequency of flk-1+/CD34+ cells was significantly increased at day 3 compared to untreated control. The combination of laser and VEGF-NP injection led to a significant increase of flk+/CD34+cells as early as 24h after treatment, compared to control and VEGF-NP or laser alone. Control-NP or SDF-1-NP treatment had no effect on flk+/CD34+ cell frequency in mouse blood. CNV area of VEGF-NP-injected eyes was significantly larger than lasered control-injected eyes.
Conclusions: :
Experimental CNV leads to mobilization of flk-1+/CD34+ EPCs into peripheral blood. Sustained intraocular release of VEGF but not SDF-1 correlates with systemic EPC mobilization. Intraocular VEGF increase may be one of the mechanisms responsible for EPC mobilization during the development of CNV.
Keywords: age-related macular degeneration • choroid: neovascularization • vascular endothelial growth factor