BACKGROUNDEndothelial dysfunction is thought to be critical events in the pathogenesis of Alzheimer's disease (AD). Endothelial progenitor cells (EPCs) have provided insight into maintaining and repairing endothelial function. To study the relation between EPCs and AD, we explored the number of circulating EPCs in patients with AD.

METHODSA total of 104 patients were recruited from both the outpatients and inpatients of the geriatric neurology department at General Hospital, Tianjin Medical University. Consecutive patients with newly diagnosed AD (n = 30), patients with vascular dementia (VaD, n = 34), and healthy elderly control subjects with normal cognition (n = 40) were enrolled after matching for age, gender, body mass index, medical history, current medication and Mini Mental State Examination. Middle cerebral artery flow velocity was examined with transcranial Doppler. Endothelial function was evaluated according to the level of EPCs, and peripheral blood EPCs was counted by flow cytometry.

RESULTSThere were no significant statistical differences of clinical data in AD, VaD and control groups (P > 0.05). The patients with AD showed decreased CD34-positive (CD34(+)) or CD133-positive (CD133(+)) levels compared to the control subjects, but there were no significant statistical differences in patients with AD. The patients with AD had significantly lower CD34(+)CD133(+) EPCs (CD34 and CD133 double positive endothelial progenitor cells) than the control subjects (P < 0.05). In the patients with AD, a lower CD34(+)CD133(+) EPCs count was independently associated with a lower Mini-Mental State Examination score (r = 0.514,P = 0.004). Patients with VaD also showed a significant decrease in CD34(+)CD133(+) EPCs levels, but this was not evidently associated with the Mini-Mental State Examination score. The changes of middle cerebral artery flow velocity were similar between AD and VaD. Middle cerebral artery flow velocity was decreased in the AD and VaD groups and significantly lower than the normal control group (P < 0.01). There was no significant difference of the blood flow velocity between the AD and VaD patients (P > 0.05).

CONCLUSIONSThe results provided evidence that patients with AD have reduced circulating EPCs. Endothelial function is impaired in patients with AD and vascular factors have a role in the pathogenesis of AD. CD34(+)CD133(+) EPCs may be a novel biomarker of AD dementia.