Identification of HIF-2α-regulated genes that play a role in human microvascular endothelial sprouting during prolonged hypoxia in vitro

During prolonged hypoxic conditions, endothelial cells change their gene
expression to adjust to the low oxygen environment. This process is
mainly regulated by the hypoxia-inducible factors, HIF-1α and HIF-2α.
Although endothelial cells do not form sprouts during prolonged hypoxic
culturing, silencing of HIF-2α partially restores sprout formation. The
present study identifies novel HIF-2α-target genes that may regulate
endothelial sprouting during prolonged hypoxia. The gene expression
profile of primary human microvascular endothelial cells (hMVECs) that
were cultured at 20 % oxygen was compared to hMVECs that were cultured
at 1 % oxygen for 14 days by using genome-wide RNA-sequencing. The
differentially regulated genes in hypoxia were compared to the genes
that were differentially regulated upon silencing of HIF-2α in hypoxia.
Surprisingly, KEGG pathway analysis showed that metabolic pathways were
enriched within genes upregulated in response to hypoxia and enriched
within genes downregulated upon HIF-2α silencing. Moreover, 51
HIF-2α-regulated genes were screened for their role in endothelial
sprouting in hypoxia, of which four genes ARRDC3, MME, PPARG and RALGPS2
directly influenced endothelial sprouting during prolonged hypoxic
culturing. The manipulation of specific downstream targets of HIF-2α
provides a new, but to be further evaluated, perspective for restoring
reduced neovascularization in several pathological conditions, such as
diabetic ulcers or other chronic wounds, for improvement of
vascularization of implanted tissue-engineered scaffolds.