IntroductionAlthough rare, circulating endothelial and progenitor cells could be considered as markers of endothelial damage and repair potential, possibly predicting the severity of cardiovascular manifestations. A number of studies highlighted the role of these cells in age-related diseases, including those characterized by ectopic calcification. Nevertheless, their use in clinical practice is still controversial, mainly due to difficulties in finding reproducible and accurate methods for their determination.MethodsCirculating mature cells (CMC, CD45(-), CD34(+), CD133(-)) and circulating progenitor cells (CPC, CD45(dim), CD34(bright), CD133(+)) were investigated by polychromatic high-speed flow cytometry to detect the expression of endothelial (CD309(+)) or osteogenic (BAP(+)) differentiation markers in healthy subjects and in patients affected by peripheral vascular manifestations associated with ectopic calcification.ResultsThis study shows that: 1) polychromatic flow cytometry represents a valuable tool to accurately identify rare cells; 2) the balance of CD309(+) on CMC/CD309(+) on CPC is altered in patients affected by peripheral vascular manifestations, suggesting the occurrence of vascular damage and low repair potential; 3) the increase of circulating cells exhibiting a shift towards an osteoblast-like phenotype (BAP(+)) is observed in the presence of ectopic calcification.ConclusionDifferences between healthy subjects and patients with ectopic calcification indicate that this approach may be useful to better evaluate endothelial dysfunction in a clinical context.