PROM1 and ischemic stroke: In light of these and further findings implying the value of circulating EPCs for endothelial repair6,11,17 and as potential prognostic biomarkers18, the present study hypothesised that changes in circulating numbers of certain EPC subtypes, defined as cells co-expressing a variety of markers for stemness (CD34 +), immaturity (CD133 +) and endothelial cell maturity (KDR +), may explain the differences reported in the severity and/or outcome of ischaemic stroke in older patients.