Vascular endothelial growth factor receptor Flt-1 negatively regulates developmental blood vessel formation by modulating endothelial cell division.
Mice lacking the vascular endothelial growth factor (VEGF) receptor flt-1 die of vascular overgrowth, and we are interested in how flt-1 normally prevents this outcome. Our results support a model whereby aberrant endothelial cell division is the cellular mechanism resulting in vascular overgrowth, and they suggest that VEGF-dependent endothelial cell division is normally finely modulated by flt-1 to produce blood vessels. Flt-1(-/-) embryonic stem cell cultures had a 2-fold increase in endothelial cells by day 8, and the endothelial cell mitotic index was significantly elevated before day 8. Flt-1 mutant embryos also had an increased endothelial cell mitotic index, indicating that aberrant endothelial cell division occurs in vivo in the absence of flt-1. The flt-1 mutant vasculature of the cultures was partially rescued by mitomycin C treatment, consistent with a cell division defect in the mutant background. Analysis of cultures at earlier time points showed no significant differences until day 5, when flt-1 mutant cultures had increased beta-galactosidase(+) cells, indicating that the expansion of flt-1 responsive cells occurs after day 4. Mitomycin C treatment blocked this early expansion, suggesting that aberrant division of angioblasts and/or endothelial cells is a hallmark of the flt-1 mutant phenotype throughout vascular development. Consistent with this model is the finding that expansion of platelet and endothelial cell adhesion molecule(+) and VE-cadherin(+) vascular cells in the flt-1 mutant background first occurs between day 5 and day 6. Taken together, these data show that flt-1 normally modulates vascular growth by controlling the rate of endothelial cell division both in vitro and in vivo.
Kearney
Joseph B
JB
Program in Genetics and Molecular Biology, Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
Ambler
Carrie A
CA
Monaco
Kelli-Ann
KA
Johnson
Natalie
N
Rapoport
Rebecca G
RG
Bautch
Victoria L
VL
D000818:Animals; D002455:Cell Division / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000166:cytology* / Q000187:drug effects; D016326:Extracellular Matrix Proteins / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D007150:Immunohistochemistry; D051379:Mice; D018345:Mice, Knockout; D016685:Mitomycin / Q000494:pharmacology; D008940:Mitotic Index; D018995:Myosin Heavy Chains; D018919:Neovascularization, Physiologic / Q000502:physiology*; D024501:Nonmuscle Myosin Type IIB; D020794:Receptor Protein-Tyrosine Kinases / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D017978:Receptors, Growth Factor / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D040262:Receptors, Vascular Endothelial Growth Factor; D013234:Stem Cells; D040281:Vascular Endothelial Growth Factor Receptor-1; D001616:beta-Galactosidase / Q000235:genetics
D016326:Extracellular Matrix Proteins; D017978:Receptors, Growth Factor; D016685:Mitomycin; C501163:Flt1 protein, mouse; D020794:Receptor Protein-Tyrosine Kinases; D040262:Receptors, Vascular Endothelial Growth Factor; D040281:Vascular Endothelial Growth Factor Receptor-1; D001616:beta-Galactosidase; D024501:Nonmuscle Myosin Type IIB; C103815:nonmuscle myosin type IIB heavy chain; D018995:Myosin Heavy Chains