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Abstract: Although determination of circulating endothelial progenitor cell (EPC) in peripheral blood by flow cytometry is an emerging marker for cardiovascular medicine, a common standardized protocol is still not available, due to the low numbers achieved in peripheral blood. In the present paper we describe a novel technique for EPC quantification as CD34+/CD144+/CD3− cells within the lymphocyte gate, which increases the percentages of EPC positivity described before and also offers high intra-assay reproducibility. These improvements are based on a gating strategy for big-sized lymphocytes, smooth fixation and cytometric clearance of CD3+ lymphocytes (T-cells). This last procedure is able to increase intra-assay Pearson''s correlation from 0.8517 to 0.8908. Therefore, the technical setting described here offers a high-performance and clinically oriented EPC determination strategy in human peripheral blood. [Copyright &y& Elsevier]

Abstract: The CFSE dye dilution assay is widely used to determine the number of divisions a given CFSE labelled cell has undergone in vitro and in vivo. In this paper, we consider how the data obtained with the use of CFSE (CFSE data) can be used to estimate the parameters determining cell division and death. For a homogeneous cell population (i.e., a population with the parameters for cell division and death being independent of time and the number of divisions cells have undergone), we consider a specific biologically based “Smith–Martin” model of cell turnover and analyze three different techniques for estimation of its parameters: direct fitting, indirect fitting and rescaling method. We find that using only CFSE data, the duration of the division phase (i.e., approximately the S+G2 +M phase of the cell cycle) can be estimated with the use of either technique. In some cases, the average division or cell cycle time can be estimated using the direct fitting of the model solution to the data or by using the Gett–Hodgkin method [Gett A. and Hodgkin, P. 2000. A cellular calculus for signal integration by T cells. Nat. Immunol. 1:239-244]. Estimation of the death rates during commitment to division (i.e., approximately the G1 phase of the cell cycle) and during the division phase may not be feasible with the use of only CFSE data. We propose that measuring an additional parameter, the fraction of cells in division, may allow estimation of all model parameters including the death rates during different stages of the cell cycle. [Copyright &y& Elsevier]