Reduced endothelial progenitor cells and brachial artery flow-mediated dilation as evidence of endothelial dysfunction in ocular hypertension and primary open-angle glaucoma

Purpose: This study aimed to assess vascular endothelial function in patients with ocular hypertension (OHT) or primary open-angle glaucoma (POAG) by measuring: (a) endothelium-dependent flow-mediated vasodilation (FMD) of the brachial artery, and (b) circulating endothelial progenitor cells, which are believed to support the integrity of the vascular endothelium. Methods: We enrolled 25 patients with OHT, 23 with POAG and 26 control subjects, all of whom were aged <65 years and had no medical history of cardiovascular disease or cardiovascular risk factors. All subjects underwent a complete ophthalmological examination, biochemistry study, assessment of cardiovascular parameters, brachial artery ultrasound assessment of endothelium-dependent FMD, generic circulating progenitor cell (CPC) and circulating endothelial progenitor cell (EPC) count with the use of flow cytometry. Results: Flow-mediated vasodilation values differed significantly in OHT (4.5 ± 1.1%; p = 0.021) and POAG (4.0 ± 0.9%; p = 0.003) patients compared with controls (7.7 ± 0.8%). The CD34⁺ KDR⁺ EPC count was markedly lower in OHT (28.0 ± 5.0; p <0.001) and POAG (24.3 ± 3.4; p <0.001) patients compared with controls (73.1 ± 8.1). Neither FMD not EPCs differed significantly between OHT and POAG patients. No significant differences in CPC count or cardiovascular parameters were found among OHT or POAG patients and controls. The levels of CD34⁺ KDR⁺ EPCs were directly correlated (p = 0.043) with FMD, and inversely correlated (p = 0.032) with baseline intraocular pressure in OHT and POAG patients. Conclusions: Both OHT and POAG patients without cardiovascular risk factors have previously unreported severely reduced circulating EPCs and reduced FMD, both of which are indicators of endothelial dysfunction and increased risk of cardiovascular events.