(Stroke. 2005;36:1112-a.)
© 2005 American Heart Association, Inc.
Letters to the Editor |
Endothelial Progenitor Cells in Cerebrovascular Disease
Department of Clinical and Experimental Medicine, University of Padova School of Medicine, Padova, Italy
To the Editor:
In their interesting article, Ghani and colleagues reported a reduction in endothelial progenitor cells (EPCs) in patients with cerebrovascular disease, when compared with healthy control subjects.1 However, the authors did not mention a recent article by Taguchi et al reporting that CD34+ cells and CD133+ cells, as an EPC-enriched population, provided a marker of cerebrovascular function,2 thus failing to consider their work as the first correlation between EPCs and cerebrovascular disease.
The study by Ghani et al took vantage from the large sample of subjects enrolled. However, they did not specify how many patients were included in the acute stroke, stable stroke and control group. Moreover, patient characteristics are not reported and it is not stated whether controls were matched for age, sex and concurrent risk factors, diseases, and medications. Given that cardiovascular and cerebrovascular diseases cluster together, the difference may be related to the overall cardiovascular risk rather than to the presence of stroke.
A growing amount of data suggests that EPCs are relevant to vascular homeostasis.3–4 Thus, the finding of reduced EPCs in the presence of altered cerebrovascular function is not surprising. What is unexpected is that the authors could not report higher EPCs in patients with acute stroke than in patients with stable stroke. Many articles have shown that tissue ischemia is a strong stimulus for mobilization of EPCs from bone marrow to peripheral blood.5–6 In their work, Taguchi et al demonstrated that circulating EPCs increased after the onset of stroke and peaked after 7 days. This inconsistency may be related to the different method used in the 2 works to identify EPCs. Indeed, it should be noted that in the work by Ghani and colleagues, EPCs are defined as CD31+/vWF+ cells in 7-day cultures of peripheral blood mononuclear cells. This technique identifies cells with a mature endothelial phenotype that may have an origin other than EPCs.7 Currently, to identify the true EPC population, cultures should be prolonged for at least 15 days, allowing selection and outgrow of cells with actual progenitor properties.8 Alternatively, EPCs may be identified and counted by flow cytometry of fresh peripheral blood, looking for the parallel expression of both surface markers of immaturity (such as CD34 of CD133) and endothelial markers (such as VEGFR-2 or CD31).9
In the end, Ghani and colleagues may have specified whether the strokes were because of in situ intracranial thrombosis or to arterial atheroembolism. In the latter case, correlations between EPC levels and carotid atherosclerosis could be of some interest.
References
- Ghani U, Shuaib A, Salam A, Nasir A, Shuaib U, Jeerakathil T, Sher F, O’rourke F, Nasser AM, Schwindt B, Todd K. Endothelial progenitor cells during cerebrovascular disease. Stroke. 2005; 36: 151–153.
[Abstract/Free Full Text] - Taguchi A, Matsuyama T, Moriwaki H, Hayashi T, Hayashida K, Nagatsuka K, Todo K, Mori K, Stern DM, Soma T, Naritomi H. Circulating CD34-positive cells provide an index of cerebrovascular function. Circulation. 2004; 109: 2979–2982.
- Hill JM, Zalos G, Halcox JP, Schenke WH, Waclawiw MA, Quyyumi AA, Finkel T. Circulating endothelial progenitor cells, vascular function, and cardiovascular risk. N Engl J Med. 2003Feb 13; 348: 593–600.
[Abstract/Free Full Text] - Urbich C, Dimmeler S. Endothelial progenitor cells: characterization and role in vascular biology. Circ Res. 2004; 95: 343–353.
[Abstract/Free Full Text] - Park S, Tepper OM, Galiano RD, Capla JM, Baharestani S, Kleinman ME, Pelo CR, Levine JP, Gurtner GC. Selective recruitment of endothelial progenitor cells to ischemic tissues with increased neovascularization. Plast Reconstr Surg. 2004; 113: 284–293.[CrossRef][Medline] [Order article via Infotrieve]
- George J, Goldstein E, Abashidze S, Deutsch V, Shmilovich H, Finkelstein A, Herz I, Miller H, Keren G. Circulating endothelial progenitor cells in patients with unstable angina: association with systemic inflammation. Eur Heart J. 2004; 25: 1003–1008.
[Abstract/Free Full Text] - Gulati R, Jevremovic D, Peterson TE, Chatterjee S, Shah V, Vile RG, Simari RD. Diverse origine and function of cells with endothelial phenotype obtained from adult human blood. Circ Res. 2003; 93: 1023–1025.
[Abstract/Free Full Text] - Hur J, Yoon CH, Kim HS, Choi JH, Kang HJ, Hwang KK, Oh BH, Lee MM, Park YB. Characterisation of two types of endothelial progenitor cells and their different contributions to neovasculogenesis. Hypertension. 2004; 24: 1–6.
- Peichev M, Naiyer AJ, Pereira D, Zhu Z, Lane WJ, Williams M, Oz MC, Hicklin DJ, Withe L, Moore MA, Rafii S. Expressione of VEGFR-2 and AC133 by circulating human CD34(+) cells identify a population of functional endothelial precursors. Blood. 2000Feb 1; 95: 952–958.
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Response:
Stroke Research Unit
Department of Psychiatry Unit, Division of Neurology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
We thank Dr. Fadini and colleagues for their interest in our paper. There is a growing understanding that endothelial progenitor cells (EPCs) are involved in repairing damaged endothelium by forming a cellular patch at the site of injury or by serving as a cellular reservoir to replace damaged endothelium.1,2,3,4 The method that we followed in our studies is based on the isolation, culture and colony formation of EPCs. The method emphasizes the ability of EPCs to make colonies and the measurement of their numbers representing an indirect measure of their ability to repair endothelial damage. In contrast, the method described by Taguchi et al5 in their studies measures the level of circulating CD34+ and other cells by flow cytometry without culturing or determining their ability to make colonies. The 2 methods may measure the same cells but comparative work is lacking. Therefore, from a methodological perspective, we believe our work represents the first detailed study on the correlation of EPCs with cerebrovascular disease. We studied the progenitor cells in a large population of patients with acute and stable cerebrovascular disease (transient ischemic attacks and completed stroke).
The methodology for identification of endothelial cells is evolving and will hopefully improve as we better understand the behavior of EPCs. Phenotypic characterization of EPCs remains controversial.6 We identified EPCs by measuring CD31, vWF and CD133 markers. We are currently also evaluating the use of flow cytometry to better identify such cells. With regards to the culturing of EPCs, we included a preplating step in order to avoid the possibility of contaminating the cultures with mature endothelial cells. An initial preplating of cells was performed for 48 hours using human fibronectin-coated plates, and nonadherent cells were collected which were finally cultured for 7 days. Cells isolated in this manner are, in fact, EPCs which exhibit many endothelial characteristics as previously demonstrated by other investigators.7,8
References
- Hill JM, Zalos G, Halcox JP, Schenke WH, Waclawiw MA, Quyyumi AA, Finkel T. Circulating endothelial progenitor cells, vascular function and cardiovascular risk. N Engl J Med. 2003; 348: 593–600.
[Abstract/Free Full Text] - Walter DH, Rittig K, Bahlmann FH, Kirchmair R, Silver M, Murayama T, Nishimura H, Losordo DW, Asahara T, Isner JM. Statin therapy accelerates endothelialization: a novel effect involving mobilization and incorporation of bone marrow-derived endothelial progenitor cells. Circulation. 2002; 105: 3017–3024.
[Abstract/Free Full Text] - Shi Q, Wu MH, Hayashida N, Wechezak AR, Clowes AW, Sauvage LR. Proof of fallout endothelialization of impervious Dacron grafts in the aorta and inferior vena cava of the dog. J Vasc Surg. 1994; 20: 546–556.[Medline] [Order article via Infotrieve]
- Kaushal S, Amiel GE, Guleserian KJ, Shapira OM, Perry T, Sutherland FW, Rabkin E, Moran AM, Schoen FJ, Atala A, Soker S, Bischoff J, Mayer JE Jr. Functional small-diameter neovessels created using endothelial progenitor cells expanded ex vivo. Nat Med. 2001; 7: 1035–1040.[CrossRef][Medline] [Order article via Infotrieve]
- Taguchi A, Matsuyama T, Moriwaki H, Hayashi T, Hayashida K, Nagatsuka K, Todo K, Mori K, Stern DM, Soma T, Naritomi H. Circulating CD34-positive cells provide an index of cerebrovascular function. Circulation. 2004; 109: 2979–2982.
- Khakoo AY, Finkel T. Endothelial progenitor cells. Annu Rev Med. 2005; 56: 79–101.[CrossRef][Medline] [Order article via Infotrieve]
- Asahara T, Murohara T, Sullivan A, Silver M, van der Zee R, Li T, Witzenbichler B, Schatteman G, Isner JM. Isolation of putative endothelial progenitor cells for angiogenesis. Science. 1997; 275: 964–967.
[Abstract/Free Full Text] - Ito H, Rovira II Bloom ML, Takeda K, Ferrans VJ, Quyyumi AA, Finkel T. Endothelial progenitor cells as putative targets for angiostatin. Cancer Res. 1999; 59: 5875–5877.
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