Retinoic acid and VEGF delay smooth muscle relative to endothelial differentiation to coordinate inner and outer coronary vessel wall morphogenesis.
BACKGROUND
Major coronary vessels derive from the proepicardium, the cellular progenitor of the epicardium, coronary endothelium, and coronary smooth muscle cells (CoSMCs). CoSMCs are delayed in their differentiation relative to coronary endothelial cells (CoEs), such that CoSMCs mature only after CoEs have assembled into tubes. The mechanisms underlying this sequential CoE/CoSMC differentiation are unknown. Retinoic acid (RA) is crucial for vascular development and the main RA-synthesizing enzyme is progressively lost from epicardially derived cells as they differentiate into blood vessel types. In parallel, myocardial vascular endothelial growth factor (VEGF) expression also decreases along coronary vessel muscularization.


OBJECTIVE
We hypothesized that RA and VEGF act coordinately as physiological brakes to CoSMC differentiation.


RESULTS
In vitro assays (proepicardial cultures, cocultures, and RALDH2 [retinaldehyde dehydrogenase-2]/VEGF adenoviral overexpression) and in vivo inhibition of RA synthesis show that RA and VEGF act as repressors of CoSMC differentiation, whereas VEGF biases epicardially derived cell differentiation toward the endothelial phenotype.


CONCLUSIONS
Experiments support a model in which early high levels of RA and VEGF prevent CoSMC differentiation from epicardially derived cells before RA and VEGF levels decline as an extensive endothelial network is established. We suggest this physiological delay guarantees the formation of a complex, hierarchical, tree of coronary vessels.
Azambuja
Ana P
AP
Brazilian Biosciences National Laboratory-LNBio, Caixa Postal 6192, CEP 13083-970, Campinas-SP, Brazil.
Portillo-Sánchez
Victor
V
Rodrigues
Mariliza V
MV
Omae
Samantha V
SV
Schechtman
Deborah
D
Strauss
Bryan E
BE
Costanzi-Strauss
Eugenia
E
Krieger
José E
JE
Perez-Pomares
José M
JM
Xavier-Neto
José
J
D000445:Aldehyde Oxidoreductases / Q000235:genetics / Q000378:metabolism; D000818:Animals; D017209:Apoptosis; D019898:Autocrine Communication; D002454:Cell Differentiation / Q000235:genetics; D002478:Cells, Cultured; D002642:Chick Embryo; D018920:Coculture Techniques; D003331:Coronary Vessels / Q000196:embryology / Q000378:metabolism*; D042783:Endothelial Cells / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D051379:Mice; D009024:Morphogenesis; D032383:Myocytes, Cardiac / Q000378:metabolism; D032389:Myocytes, Smooth Muscle / Q000378:metabolism*; D019899:Paracrine Communication; D010496:Pericardium / Q000196:embryology / Q000378:metabolism*; D011784:Quail; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics; D046509:Tissue Culture Techniques; D014161:Transduction, Genetic; D014212:Tretinoin / Q000378:metabolism*; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism*
D011993:Recombinant Fusion Proteins; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; D014212:Tretinoin; D000445:Aldehyde Oxidoreductases; C470579:RALDH2 protein, mouse