New flow cytometric technique for the evaluation of circulating endothelial progenitor cell levels in various disease groups.

Circulating endothelial progenitor cells (EPC) localise to sites of ischaemia and play a role in vascular repair and re-endothelialisation of injured blood vessels. Low levels of EPCs are associated with cardiovascular disease (CVD) in the general population. It is not clear at present whether and how the numbers of circulating EPCs vary in diseases other than CVD. We have enumerated EPCs by the flow cytometric analysis of whole blood by using a novel cocktail of monoclonal antibodies. This consisted of CD2FITC, CD13FITC and CD22FITC to eliminate non-progenitor cells and VEGFR2PE and CD133-streptavidin-PeCy7 to include only EPCs. We analysed 250 patients with varying stages of uraemia, 36 patients with inflammatory bowel disease (IBD) and 9 patients with acute respiratory distress syndrome and compared this to 74 healthy controls. Using flow cytometry we were able to measure the circulating levels of EPCs, with a result available within hours of the sample being obtained. Circulating EPC numbers vary in different patient groups and healthy controls. In uraemic patients, irrespective of disease severity, there are lower numbers of circulating EPC numbers compared to normal controls (46.6+/-3.7 vs. 66.1+/-4.7; p=0.03). This new technique provides a means of monitoring patients and shows a reduction in circulating EPCs in uraemic patients; this abnormality may be a target of novel therapies.