M. Hangai et al., Angiopoietin-1 upregulation by vascular endothelial growth factor in humanretinal pigment epithelial cells, INV OPHTH V, 42(7), 2001, pp. 1617-1625
PURPOSE. TO determine whether vascular endothelial growth factor (VEGF) reg
ulates angiopoietin (Ang)-1 and -2 expression in retinal pigment epithelial
(RPE) cells.
METHODS. Expression of VEGF, Ang1, and Ang2 in surgically removed human cho
roidal neovascular membranes (CNVMs) was analyzed by double-label confocal
immunofluorescence microscopy. Total RNA was extracted from cultured human
RPE cells treated with VEGF for mRNA analysis. Northern blot analysis was p
erformed to examine the time course and dose response of Ang1 and Ang2 mRNA
expression. mRNA stability and nuclear nm-on analyses were performed. Secr
eted Angl and Ang2 protein levels in conditioned media from RPE cells were
examined by Western blot analysis.
RESULTS. Angl and Ang2 immunostaining colocalized with VEGF-positive stroma
l cells in human CNVMs. Angl and Ang2 mRNAs were expressed by cultured seru
m-starved RPE cells. VEGF upregulated Angl mRNA in a time- and dose-depende
nt manner without a significant change in Ang2 mRNA. Angl and Ang2 mRNAs in
RPE cells were as stable as that of S18. VEGF stimulation further increase
d the half-life of Ang1 mRNA, but did not alter its transcription rate. VEG
F increased the amount of Ang1, but not Ang2, protein secreted into the med
ium.
CONCLUSION. The colocalization of Ang1 and Ang2 with VEGF in CNVM stromal c
ells and the upregulation of Angl expression by VEGF in cultured RPE cells
suggest that VEGF may selectively modulate Ang expression during CM.