Blood, Vol. 94 No. 4 (August 15), 1999:
pp. 1482-1483
CORRESPONDENCE
Circulating Apoptotic Endothelial Cells
 |
LETTER |
To the Editor:
In their article published in the May 1, 1999 issue of Blood,
Mutin et al1 find no circulating endothelial cells in their control group of patients and are unable to demonstrate activated or
apoptotic endothelial cells. These results disagree with previously published data on the characteristics of circulating nucleated endothelial cells in normal healthy persons.2,3
There are several possible reasons for the failure to identify
apoptotic endothelial cells in this study. (1) Neither the antibody nor
the methods used by the authors have ever been validated for their
ability to reliably identify and retrieve apoptotic endothelial
cells from peripheral blood. (2) The morphologic criteria used by the
investigators for identification of endothelial cells after staining
with acridin orange1 exclude cells with characteristics of
apoptotic endothelial cells after such staining.4-6 (3)
They use a kit for detection of apoptosis1 that fails to
identify cells in early stages of apoptosis.7 (4) All
patients are on aspirin, heparin, and a 
-blocker.1
Aspirin prevents activation of endothelial cells in vitro8
and reduces endothelial detachment9 and numbers of
circulating endothelial cells in vivo.10 It also stimulates
ferritin production in endothelial cells,11 and iron chelation was shown to prevent apoptosis of these cells.12
Heparin reduces endothelial cell detachment9 and numbers of
circulating endothelial cells in vivo.13 It also activates
the constitutive nitric oxide synthase in endothelial
cells,14 an effect that prevents apoptosis in these
cells.15 -Blockers may reduce the influence of
endogenous adrenergic stimulants that are known to increase the number
of circulating endothelial cells.16 They also prevent the
formation of angiotensin II,17 and the latter has a known
ability to induce apoptosis in endothelial cells.18
The use of poorly validated methods for detection and isolation of
apoptotic cells, the exclusion of cells in early and late stages of
apoptosis, and administration of antiapoptotic factors may have
significantly influenced the results as reported by Mutin et
al.1
Tihomir 
tefanec
Section
of Critical Care Medicine
Saint Vincent's Hospital and Medical
Center
New York, NY
| |
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