Vascular endothelial growth factor mediates hypoxic stimulated embryonic bladder growth in organ culture.
OBJECTIVE
Tissue hypoxia enhances embryonic angiogenesis at least in part by up-regulating vascular endothelial growth factor. Additionally, exogenous vascular endothelial growth factor-A enhances embryonic bladder explant growth. We hypothesized that developing bladders are hypoxic in vivo and oxygen tensions modulate explanted bladder growth by altering vascular endothelial growth factor-A expression.


METHODS
Embryonic day 14 mouse bladders were cultured in 20% O(2) or 3% O(2) atmospheres. Some cultures were supplemented with a vascular endothelial growth factor receptor 1/Fc chimera to block vascular endothelial growth factor bioactivity. After 6 days explant areas, DNA, protein, total cell numbers, and proportions expressing endothelial and smooth muscle markers were measured. Pimonidazole was administered to pregnant mice and hypoxia was sought in embryonic tissues by immunohistochemistry.


RESULTS
In vivo pimonidazole adducts and vascular endothelial growth factor-A immunolocalized to embryonic urothelium and bladders up-regulated total vascular endothelial growth factor-A between embryonic days 14 and 18. All growth parameters and vascular endothelial growth factor-A protein levels were enhanced in hypoxic vs normoxic culture. Addition of vascular endothelial growth factor receptor 1/Fc prevented this accelerated growth.


CONCLUSIONS
In vivo embryonic bladders are hypoxic and express vascular endothelial growth factor-A. In vitro, when oxygen tensions are manipulated, vascular endothelial growth factor-A protein positively correlates with the growth of whole explants as well as endothelium. Normal embryonic bladder development may be driven at least in part by hypoxic up-regulation of vascular endothelial growth factor-A.
Burgu
Berk
B
Department of Pediatric Urology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA. berkburgu@gmail.com
Medina Ortiz
Wanda E
WE
Pitera
Jolanta E
JE
Woolf
Adrian S
AS
Wilcox
Duncan T
DT
D000818:Animals; D015687:Cell Hypoxia; D051379:Mice; D009924:Organ Culture Techniques; D001743:Urinary Bladder / Q000196:embryology* / Q000254:growth & development*; D042461:Vascular Endothelial Growth Factor A / Q000502:physiology*
D042461:Vascular Endothelial Growth Factor A