Circulating Hematopoietic Stem Cells in Patients with Neovascular Age-Related Macular Degeneration

Circulating hematopoietic stem cells (HSCs) appear to have roles in the formation of choroidal neovascularization (CNV) in age-related macular degeneration (AMD). This study was conducted to investigate whether the number or function of HSCs plays a role in neovascular AMD. Eighty-one patients with neovascular AMD who underwent comprehensive fundus examinations every 3 months were included. The number of CD34(+) HSCs isolated from peripheral blood was counted by flow cytometry. Serum cytokine levels were assessed by enzyme-linked immunosorbent assay. To examine the function of circulating HSCs, mononuclear cells were cultured and then colony forming unit (CFU-EC) and migration were measured. The number of circulating CD34(+) HSCs was significantly increased in the patients with active CNV without major systemic diseases (stable: 3.8 +/- 0.3 cells/microL, active: 5.5 +/- 0.7 cells/microL, stable versus active: P < 0.05). The number of HSCs correlated positively with the erythropoietin serum level (r = 0.47, P = 0.002). Although there was no significant difference in the CFU-EC between the patients with CNV and the control subjects, a significant decrease of CFU-EC was observed in the patients with bilateral or larger CNV. The findings suggest that CD34(+) HSCs may be recruited from bone marrow through a signal from active CNV. Furthermore, HSCs may play a role in the severity of CNV.