Methodological issues in measuring circulating endothelial cells to detect endothelial dysfunction
Bart Ramakers, Radboud University Nijmegen Medical centre
18 June 2010
To the editor: Referring to the article of Fink et al. [1] we consider it important to discuss a major drawback using circulating endothelial cells (CECs) as a marker of endothelial dysfunction. There is a wide variety in techniques to measure CECs and endothelial progenitor cells (EPCs). Only in the field of oncology there seems to be consensus that CECs and EPCs can properly be distinguished from other cells using: CD31, CD34, CD45, CD133, CD146 and VEGF. Fink et al. used CD146 and CD45 to detect CECs after ferromagnetic separation. Since, e.g., smooth muscle cells, parenchyma cells and hematopoietic stem cells express the same markers this method is rather nonspecific. In healthy subjects, CECs do not exceed 0.7±0.3 cells/ml, while during septic shock, also associated with endothelial dysfunction, CECs increase up to 10.4±1.2 cells/ml [2]. Levels of CECs found by Fink et al. (4500±1200 cells/ml) are therefore unlikely to represent a reliable number of solely CECs, but may be caused, e.g., by a change in leukocyte differentiation following CPR, ischemia-induced cell death, or false positive selection of other cell types such as hematopoietic stem cells. CECs may have potential as markers of endothelial dysfunction, but consensus regarding the techniques used to measure CECs is of the utmost importance. In our opinion, CECs should be defined in human blood as CD31+, CD34+ CD45-, CD133-, (CD146+) and VEGF+ cells [4].
Bart P. Ramakers1,2 J. van Velzen4 Peter Pickkers1,2,3 Department of Intensive Care Medicine1, and Pharmacology-Toxicology2, N4i3 Department of Immunology, University Medical Centre Utrecht4, Utrecht, The Netherlands
Radboud University Nijmegen Medical Center PO-box 9101, 6500 HB, Nijmegen, The Netherlands E-Mail: p.pickkers@ic.umcn.nl
Reference List
(1) Fink K, Schwarz M, Feldbruegge L, Sunkomat JN, Schwab T, Bourgeois N, et al. Severe endothelial injury and subsequent repair in patients after successful cardiopulmonary resuscitation. Crit Care 2010 Jun 4;14:R104. (2) Mutunga M, Fulton B, Bullock R, Batchelor A, Gascoigne A, Gillespie JI, et al. Circulating endothelial cells in patients with septic shock. Am J Respir Crit Care Med 2001 Jan;163:195-200. (3) Boos CJ, Mayr FB, Lip GY, Jilma B. Endotoxemia enhances circulating endothelial cells in humans. J Thromb Haemost 2006 Nov;4:2509-11. (4) Duda DG, Cohen KS, Scadden DT, Jain RK. A protocol for phenotypic detection and enumeration of circulating endothelial cells and circulating progenitor cells in human blood. Nat Protoc 2007;2:805-10.
Critical Care
Methodological issues in measuring circulating endothelial cells to detect endothelial dysfunction
18 June 2010
To the editor: Referring to the article of Fink et al. [1] we consider it important to discuss a major drawback using circulating endothelial cells (CECs) as a marker of endothelial dysfunction. There is a wide variety in techniques to measure CECs and endothelial progenitor cells (EPCs). Only in the field of oncology there seems to be consensus that CECs and EPCs can properly be distinguished from other cells using: CD31, CD34, CD45, CD133, CD146 and VEGF. Fink et al. used CD146 and CD45 to detect CECs after ferromagnetic separation. Since, e.g., smooth muscle cells, parenchyma cells and hematopoietic stem cells express the same markers this method is rather nonspecific.
In healthy subjects, CECs do not exceed 0.7±0.3 cells/ml, while during septic shock, also associated with endothelial dysfunction, CECs increase up to 10.4±1.2 cells/ml [2]. Levels of CECs found by Fink et al. (4500±1200 cells/ml) are therefore unlikely to represent a reliable number of solely CECs, but may be caused, e.g., by a change in leukocyte differentiation following CPR, ischemia-induced cell death, or false positive selection of other cell types such as hematopoietic stem cells.
CECs may have potential as markers of endothelial dysfunction, but consensus regarding the techniques used to measure CECs is of the utmost importance. In our opinion, CECs should be defined in human blood as CD31+, CD34+ CD45-, CD133-, (CD146+) and VEGF+ cells [4].
Bart P. Ramakers1,2
J. van Velzen4
Peter Pickkers1,2,3
Department of Intensive Care Medicine1, and Pharmacology-Toxicology2, N4i3
Department of Immunology, University Medical Centre Utrecht4, Utrecht, The Netherlands
Radboud University Nijmegen Medical Center
PO-box 9101, 6500 HB, Nijmegen, The Netherlands
E-Mail: p.pickkers@ic.umcn.nl
Reference List
(1) Fink K, Schwarz M, Feldbruegge L, Sunkomat JN, Schwab T, Bourgeois N, et al. Severe endothelial injury and subsequent repair in patients after successful cardiopulmonary resuscitation. Crit Care 2010 Jun 4;14:R104.
(2) Mutunga M, Fulton B, Bullock R, Batchelor A, Gascoigne A, Gillespie JI, et al. Circulating endothelial cells in patients with septic shock. Am J Respir Crit Care Med 2001 Jan;163:195-200.
(3) Boos CJ, Mayr FB, Lip GY, Jilma B. Endotoxemia enhances circulating endothelial cells in humans. J Thromb Haemost 2006 Nov;4:2509-11.
(4) Duda DG, Cohen KS, Scadden DT, Jain RK. A protocol for phenotypic detection and enumeration of circulating endothelial cells and circulating progenitor cells in human blood. Nat Protoc 2007;2:805-10.
Competing interests
None