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Objective— Smooth muscle progenitor cells (SMPCs) were intriguingly shown to act as a double-edged sword in the pathogenesis of atherosclerosis. To fully clarify the roles of SMPCs in atherosclerosis, a distinct panel of SMPC surface markers is mandatory to be developed. Methods and Results— Microarray gene expression analyses were used to discover potential surface markers of SMPCs. In vitro and in vivo experiments documented that platelet-derived growth factor receptor-β, carboxypeptidase M, carbonic anhydrase 12, receptor activity-modifying protein 1, and low-density lipoprotein receptor–related protein were the 5 specific surface markers regulating various SMPC functions, including migration, extracellular matrix formation, resistance to hypoxia, and anti-inflammation. In s evere combined immunodeficiency /nonobese diabetic mice after femoral arterial wire injury, injected human peripheral blood mononuclear cells contributed to substantial amount of neointimal α-smooth muscle actin-positive cells, coexpressing platelet-derived growth factor receptor-β, carboxypeptidase M, carbonic anhydrase 12, receptor activity-modifying protein 1, and low-density lipoprotein receptor–related protein. Based on these markers, a novel quantification assay was developed to enumerate circulating early SMPC. Early SMPC numbers were higher in patients with unstable angina compared with those with normal coronary angiograms. In patients with acute ST-elevation myocardial infarction, different patterns of serial early SMPC changes were noted, related to different clinical presentations. Conclusion— Surface markers of heterogeneous SMPCs exhibit various functions associated with atherosclerotic pathophysiology. Quantification of surface marker–defined SMPCs provides a platform for studying SMPCs in cardiovascular diseases.

Endothelial colony-forming cells (ECFCs) are undergoing extensive investigations to tackle certain deliberating cardiovascular diseases. However, the success of this approach depends on a thorough understanding of ECFC biology. This study sought to determine the factors associated with the purity, biological function, and activation potential of ex vivo expanded ECFCs. Seventy-three patients with newly diagnosed coronary artery disease (CAD) and 24 controls were studied. ECFCs were cultured for up to 10 passages to investigate changes in and the impact of coronary risk factors on ECFC biological functions and the atherogenic potential. Passages 3-5 of ECFCs exhibited higher endothelial phenotype expression and better biological functions, in terms of nitric oxide secretion and tubular formation, but lower activation potentials compared with later passages (P <0.05). Studies on passage 3 showed that endothelial phenotype expression and biological functions were impaired, and the activation potentials of the ECFCs were significantly upregulated in subjects with coronary risk factors and especially those with CAD (P < 0.05). Furthermore, ECFCs were already activated before inflammatory stimulation in subjects with diabetes mellitus, hypertension, and CAD. Atorvastatin upregulated the endothelial nitric oxide synthase expression of ECFCs in CAD patients (P < 0.01), although not up to the baseline level of controls. In conclusion, the passage number and a variety of coronary risk factors were associated with the purity, biological function, and activation potential of ex vivo-expanded ECFCs. Functional assessments and manipulations of ECFCs have to be pursued in patients with extensive risk factors.