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Monitoring Stem Cell Research 
endothelial progenitors, including co-expression of Tie-2, as well as 
AC 133, but not markers of mature endothelium such as ecNOS, vWF, 
E-selectin, and ICAM. Sorting CD34+ cells on the basis of CD117 
bright or dim expression demonstrated that GATA-2 mRNA and 
protein levels were significaantly higher in the GDI 
population, indicating that human adult bone marrow contains cells 
with an angioblast-like phenotype. 
Since the frequency of circulating endothelial cell precursors 
in animal models has been shovm to be increased by either VEGF 
or regional ischemia phenotypically-defined angioblasts were 
examined for proliferative responses to VEGF and to factors in 
ischemic serum. CD117^^^^^GATA-2^^angioblasts demonstrated 
significantly higher proliferative responses relative to 
CD117^™GATA-2^° bone marrow-derived cells from the same donor 
following culture for 96 hours with either VEGF or ischemic serum. 
The expanded angioblast population consisted of large blast cells, 
defined by forward scatter, which continued to express immature 
markers, including GATA-2 and CD117^^^^^, but not markers of 
mature endothelial cells, including eNOS or E-selectin, indicating 
blast proliferation without differentiation under these culture 
conditions. However, culture on fibronectin with endothelial growth 
medium resulted in outgrowth of monolayers with endothelial 
morphology and functional and phenotypic features characteristic of 
endothelial cells, including uniform uptake of acetylated LDL, and co- 
expression of CD34, factor VIII, and eNOS. Thus, G-CSF treatment of 
adult humans mobilizes into the peripheral circulation a bone- 
marrow derived population with phenotypic and functional 
characteristics of embryonic angioblasts, as defined by specific 
surface phenotype, high proliferative responses to VEGF and 
cytokines in ischemic serum, and ability differentiate into endothelial 
cells by culture in medium enriched with endothelial growth factors. 
Human Angioblasts Induce Neovascularization Of The Myocardial 
Infarct Zone. Intravenous injection of fireshly-obtained human 
angioblasts into athymic nude rats who had undergone ligation of 
the left anterior descending (LAD) coronary artery resulted in infarct 
zone infiltration within 48 hours. Few human cells were detected in 
unaffected areas of hearts with regional infarcts or in myocardium of 
sham-operated rats. Histologic examination at two weeks post- 
infarction revealed that injection of human angioblasts was 
accompanied by a significant increase in infarct zone 
PRE-PUBLICATION VERSION 
