HIF-2alpha-haploinsufficient mice have blunted retinal neovascularization due to impaired expression of a proangiogenic gene battery.
OBJECTIVE
To characterize the effect of HIF-2alpha haploinsufficiency on retinal neovascularization and angiogenic signaling in neonatal mice.


METHODS
Retinal samples were obtained from HIF-2alpha-haploinsufficient (Epas1+/-) and wild-type (Epas1+/+) neonatal mice subjected to an oxygen-induced retinopathy (OIR) protocol. Histologic and molecular studies were performed immediately, 12 hours, or 5 days after initiation of the hypoxia phase of the OIR protocol. Molecular profiling was performed in mouse brain endothelial cells maintained in normoxia or hypoxia. Transfection studies assessed the response of isolated promoter regions from proangiogenic genes to HIF-1alpha or -2alpha overexpression.


RESULTS
Epas1+/- mice exhibited no significant differences in retinal vasculature during normal development but had reduced retinal neovascularization in an OIR protocol. Multiple proangiogenic factors were induced during the hypoxia phase in Epas1+/+ OIR retinal samples, whereas Epas1+/- OIR retinal samples had absent or blunted induction of these same factors. Several, but not all, proangiogenic factors were induced in mouse brain endothelial cells after hypoxia. In transfection assays, most proangiogenic promoter regions were preferentially activated by HIF-2alpha relative to HIF-1alpha.


CONCLUSIONS
HIF-2alpha deficiency results in reduced neovascularization and blunted inducibility of multiple proangiogenic factors in the retinas of mice with OIR. The authors propose that HIF-2alpha is a master regulator of proangiogenic factors in retinal vascular endothelial cells, the predominant cell type of the retina in which HIF-2alpha is expressed. Future studies will address whether the molecular and functional roles for HIF-2alpha identified from these studies can be generalized to other pathophysiological states involving neovascularization.
Dioum
Elhadji M
EM
Department of Internal Medicine, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390-8573, USA.
Clarke
Stephen L
SL
Ding
Kan
K
Repa
Joyce J
JJ
Garcia
Joseph A
JA
D042501:Angiogenic Proteins / Q000235:genetics*; D000818:Animals; D000831:Animals, Newborn; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics*; D018929:Cell Culture Techniques; D018389:Codon, Nonsense; D005260:Female; D005786:Gene Expression Regulation / Q000502:physiology*; D017930:Genes, Reporter; D006801:Humans; D000860:Hypoxia / Q000378:metabolism*; D007231:Infant, Newborn; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D020125:Mutation, Missense; D010100:Oxygen / Q000633:toxicity; D010957:Plasmids; D015861:Retinal Neovascularization / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D012171:Retinal Vessels / Q000473:pathology; D012178:Retinopathy of Prematurity / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection; D000099162:Endothelial PAS Domain-Containing Protein 1
D042501:Angiogenic Proteins; D051792:Basic Helix-Loop-Helix Proteins; D018389:Codon, Nonsense; D010100:Oxygen; D000099162:Endothelial PAS Domain-Containing Protein 1