Monocytes coexpress endothelial and macrophagocytic lineage markers and form cord-like structures in Matrigel under angiogenic conditions.
OBJECTIVE
It has been shown that circulating human non-adherent CD34+ cells coexpressing vascular endothelial growth factor (VEGF)-R2 and AC133 have the capacity to differentiate into adherent mature endothelial cells. However, prior studies have demonstrated that a much bigger subset of primary adherent mononuclear cells can also form endothelial progenitor cells (EPC). To determine the origin of the latter cell population we tested the hypothesis: do monocytes as a firmly adherent and plastic cell type have the potential to differentiate into an endothelial phenotype.


METHODS
CD34-/CD14+ monocytes were isolated from human peripheral blood by adherence separation and magnetic bead selection (purity >90%) and cultured on fibronectin-coated plastic dishes (medium containing VEGF 10 ng/ml, basic fibroblast growth factor (bFGF) 2 ng/ml, insulin like growth factor (IGF-1) 1 ng/ml, 20% fetal calf serum).


RESULTS
After 2 weeks of culture, using fluorescence activated cell analysis we observed a new expression of the endothelial markers von Willebrand factor (vWf), VE-cadherin (VE) and ec-NOS in 45.2, 12.4 and 9.8% of the cells, respectively. The proportion of cells expressing these markers further increased after 4 weeks (94.2, 89.7 and 58.8% of these cells, respectively). The proportion of CD45 expressing cells remained unchanged during this period. However, after 14 days the specific macrophage antigen CD68 was newly expressed in 62% of the analysed cells with a further increase to 90% after 28 days of culture. In three-dimensional gel (Matrigel the formation of cord- and tubular-like structures was observed.


CONCLUSIONS
The present data indicate that under angiogenic stimulation macrophages develop an endothelial phenotype with expression of specific surface markers and even form cord- and tubular-like structures in vitro suggesting that this cell population may be recruited for vasculogenesis.
Schmeisser
A
A
Department of Cardiology, Technical University of Dresden, Heart Center Dresden, Fetscherstr. 76, D-01307, Dresden, Germany. alexanderschmeis@t-online.de
Garlichs
C D
CD
Zhang
H
H
Eskafi
S
S
Graffy
C
C
Ludwig
J
J
Strasser
R H
RH
Daniel
W G
WG
D015703:Antigens, CD; D018952:Antigens, CD34 / Q000032:analysis; D015415:Biomarkers / Q000032:analysis; D015820:Cadherins / Q000032:analysis; D002448:Cell Adhesion / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D003094:Collagen; D004338:Drug Combinations; D016228:Endothelial Growth Factors / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000166:cytology*; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology; D005434:Flow Cytometry; D006133:Growth Substances / Q000494:pharmacology*; D006801:Humans; D007797:Laminin; D017493:Leukocyte Common Antigens / Q000032:analysis; D018950:Lipopolysaccharide Receptors; D008222:Lymphokines / Q000494:pharmacology; D009000:Monocytes / Q000187:drug effects / Q000502:physiology*; D018919:Neovascularization, Physiologic; D019001:Nitric Oxide Synthase / Q000032:analysis; D052250:Nitric Oxide Synthase Type III; D011509:Proteoglycans; D020794:Receptor Protein-Tyrosine Kinases / Q000032:analysis; D017978:Receptors, Growth Factor / Q000032:analysis; D040262:Receptors, Vascular Endothelial Growth Factor; D020133:Reverse Transcriptase Polymerase Chain Reaction; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D014841:von Willebrand Factor / Q000032:analysis; D000099152:Cadherin 5
D015703:Antigens, CD; D018952:Antigens, CD34; D015415:Biomarkers; D015820:Cadherins; D003094:Collagen; D004338:Drug Combinations; D016228:Endothelial Growth Factors; D016222:Fibroblast Growth Factor 2; D006133:Growth Substances; D007797:Laminin; D017493:Leukocyte Common Antigens; D018950:Lipopolysaccharide Receptors; D008222:Lymphokines; D019001:Nitric Oxide Synthase; D052250:Nitric Oxide Synthase Type III; D011509:Proteoglycans; D020794:Receptor Protein-Tyrosine Kinases; D017978:Receptors, Growth Factor; D040262:Receptors, Vascular Endothelial Growth Factor; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D014841:von Willebrand Factor; D000099152:Cadherin 5; C059485:matrigel; C496314:NOS3 protein, human