Endothelial progenitor cells induce a phenotype shift in differentiated endothelial cells towards PDGF/PDGFRβ axis-mediated angiogenesis.
BACKGROUND
Endothelial Progenitor Cells (EPC) support neovascularization and regeneration of injured endothelium both by providing a proliferative cell pool capable of differentiation into mature vascular endothelial cells and by secretion of angiogenic growth factors.


OBJECTIVE
The aim of this study was to investigate the role of PDGF-BB and PDGFRβ in EPC-mediated angiogenesis of differentiated endothelial cells.


RESULTS
Conditioned medium from human EPC (EPC-CM) cultured in hypoxic conditions contained substantially higher levels of PDGF-BB as compared to normoxic conditions (P<0.01). EPC-CM increased proliferation (1.39-fold; P<0.001) and migration (2.13-fold; P<0.001) of isolated human umbilical vein endothelial cells (HUVEC), as well as sprouting of vascular structures from ex vivo cultured aortic rings (2.78-fold increase; P = 0.01). The capacity of EPC-CM to modulate the PDGFRβ expression in HUVEC was assessed by western blot and RT-PCR. All the pro-angiogenic effects of EPC-CM on HUVEC could be partially inhibited by inactivation of PDGFRβ (P<0.01). EPC-CM triggered a distinct up-regulation of PDGFRβ (2.5±0.5; P<0.05) and its phosphorylation (3.6±0.6; P<0.05) in HUVEC. This was not observed after exposure of HUVEC to recombinant human PDGF-BB alone.


CONCLUSIONS
These data indicate that EPC-CM sensitize endothelial cells and induce a pro-angiogenic phenotype including the up-regulation of PDGFRβ, thereby turning the PDGF/PDGFRβ signaling-axis into a critical element of EPC-induced endothelial angiogenesis. This finding may be utilized to enhance EPC-based therapy of ischemic tissue in future.
Department of Cardiac Surgery, Children's Hospital Boston and Harvard Medical School, Boston, Massachusetts, USA.
Moritz
M
Wyler von Ballmoos
Zijiang
Z
Yang
Jan
J
Völzmann
Iris
I
Baumgartner
Christoph
C
Kalka
Stefano
S
Di Santo
D000818:Animals; D001011:Aorta / Q000502:physiology; D000077214:Becaplermin; D015153:Blotting, Western; D002454:Cell Differentiation; D002478:Cells, Cultured; D017077:Culture Media, Conditioned / Q000378:metabolism / Q000494:pharmacology; D042783:Endothelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D018919:Neovascularization, Physiologic / Q000187:drug effects / Q000502:physiology*; D010982:Platelet-Derived Growth Factor / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D020574:Proto-Oncogene Proteins c-sis; D051381:Rats; D017208:Rats, Wistar; D020797:Receptor, Platelet-Derived Growth Factor beta / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013234:Stem Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*
D017077:Culture Media, Conditioned; D010982:Platelet-Derived Growth Factor; D020574:Proto-Oncogene Proteins c-sis; D011994:Recombinant Proteins; D000077214:Becaplermin; D020797:Receptor, Platelet-Derived Growth Factor beta