Vascular endothelial growth factor is crucial for erythropoietin-induced improvement of cardiac function in heart failure.
OBJECTIVE
We intended to delineate the mechanisms of erythropoietin (EPO)-induced cardiac vascular endothelial growth factor (VEGF) production and to establish if VEGF is crucial for EPO-induced improvement of cardiac performance.


RESULTS
The effects of EPO on VEGF expression were studied in cultured cardiac cells and EPO-treated hearts. The role of VEGF in EPO-induced neovascularization was studied with two distinct VEGF-neutralizing antibodies or irrelevant control IgG in an aortic sprouting assay and in rats with heart failure (HF) after myocardial infarction (MI) treated with EPO. EPO-alfa (10 IU/mL) was used in vitro and darbepoetin alfa (40 microg/kg/3 weeks, starting 3 weeks after MI) in vivo. EPO stimulated VEGF mRNA expression through the signal transducers and activators of transcription-3 (STAT-3) pathway in neonatal rat cardiomyocytes, but not in endothelial cells or fibroblasts. Similarly, the direct effects of EPO on endothelial sprouting were modest and VEGF independent. In rats with HF, EPO increased VEGF protein expression predominantly in cardiomyocytes, associated with a 37% increase in capillary density and improved cardiac performance. Administration of VEGF-neutralizing antibodies abrogated the salutary effects of EPO on cardiac microvascularization and function. VEGF neutralization attenuated EPO-induced proliferation of myocardial endothelial cells and reduced myocardial incorporation of endothelial progenitor cells (EPCs) in rats with alkaline phosphatase-labelled bone marrow cells.


CONCLUSIONS
VEGF is crucial for EPO-induced improvement of cardiac function in HF. EPO fosters VEGF expression predominantly in cardiomyocytes, which in turn stimulates myocardial endothelial proliferation and incorporation of EPCs.
Department of Cardiology, Thoraxcenter, University Medical Center Groningen, University of Groningen, Hanzeplein 1, PO Box 30001, Groningen 9700 RB, The Netherlands. b.d.westenbrink@thorax.umcg.nl
B Daan
BD
Westenbrink
Willem-Peter T
WP
Ruifrok
Adriaan A
AA
Voors
Ronald G
RG
Tilton
Dirk J
DJ
van Veldhuisen
Regien G
RG
Schoemaker
Wiek H
WH
van Gilst
Rudolf A
RA
de Boer
D000818:Animals; D000831:Animals, Newborn; D002316:Cardiotonic Agents / Q000494:pharmacology*; D002465:Cell Movement / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D000068256:Darbepoetin alfa; D004195:Disease Models, Animal; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism; D000068817:Epoetin Alfa; D004921:Erythropoietin / Q000031:analogs & derivatives* / Q000494:pharmacology*; D006333:Heart Failure / Q000188:drug therapy* / Q000378:metabolism / Q000503:physiopathology; D006801:Humans; D008297:Male; D032383:Myocytes, Cardiac / Q000187:drug effects* / Q000378:metabolism; D018919:Neovascularization, Physiologic / Q000187:drug effects; D019899:Paracrine Communication / Q000187:drug effects; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins; D020127:Recovery of Function; D050796:STAT3 Transcription Factor / Q000378:metabolism; D033581:Stem Cell Transplantation; D013234:Stem Cells / Q000187:drug effects / Q000378:metabolism; D013997:Time Factors; D014158:Transcription, Genetic / Q000187:drug effects; D015854:Up-Regulation; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism*; D016277:Ventricular Function, Left / Q000187:drug effects*; D020257:Ventricular Remodeling / Q000187:drug effects
D002316:Cardiotonic Agents; D012333:RNA, Messenger; D011994:Recombinant Proteins; D050796:STAT3 Transcription Factor; C494088:Stat3 protein, rat; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; C467498:vascular endothelial growth factor A, rat; D004921:Erythropoietin; D000068256:Darbepoetin alfa; D000068817:Epoetin Alfa