Emerging evidence to support the use of endothelial progenitor cells (EPCs) for angiogenic therapies or as biomarkers to assess cardiovascular disease risk and progression is compelling. However, there is no uniform definition of an EPC, which makes interpretation of these studies difficult. Although hallmarks of stem and progenitor cells are their ability to proliferate and to give rise to functional progeny, EPCs are primarily defined by the expression of cell-surface antigens. Here, using adult peripheral and umbilical cord blood, we describe an approach that identifies a novel hierarchy of EPCs based on their clonogenic and proliferative potential, analogous to the hematopoietic cell system. In fact, some EPCs form replatable colonies when deposited at the singlecell level. Using this approach, we also identify a previously unrecognized population of EPCs in cord blood that can achieve at least 100 population doublings, replate into at least secondary and tertiary colonies, and retain high levels of telomerase activity. Thus, these studies describe a clonogenic method to define a hierarchy of EPCs based on their proliferative potential, and they identify a unique population of high proliferative potentialendothelial colony-forming cells (HPPECFCs) in human umbilical cord blood.

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PURPOSEPlasma-mediated radiofrequency ablation (coblation) creates a cavity for directed polymethylmethacrylate deposition through molecular dissociation, providing a safe and efficacious cementoplasty for patients with high-risk, painful vertebral body metastatic disease. The purpose of this study was to retrospectively review and report details regarding the feasibility, safety, and efficacy of coblation and cementoplasty for treating painful advanced vertebral body metastatic disease. MATERIALS AND METHODSFifteen patients with painful metastatic vertebral body fractures with a posterior cortical defect and/or epidural tumor extension underwent percutaneous coblation and cementoplasty. Each patient's medical record was reviewed for technical success, imaging outcome, complications, and palliative effect. RESULTSOf the 15 cases, 14 were completed successfully. Postprocedure imaging studies demonstrated adequate cement deposition within the targeted vertebral body without cement extravasation or fracture progression during the 1-3 months follow-up period. Pain relief was achieved in all patients, and no neurological damage was reported (mean follow-up, 141.1±132.5 days). CONCLUSIONPercutaneous image-guided coblation-mediated cavity creation prior to vertebroplasty allows for safe, efficacious cement deposition in patients with metastatic foci. Future studies prospectively comparing this procedure with other standard-of-care regimens are warranted.