Hypoxia is responsible for soluble vascular endothelial growth factor receptor-1 (VEGFR-1) but not for soluble endoglin induction in villous trophoblast.
BACKGROUND
Pre-eclampsia is a pregnancy disorder characterized by a maternal endothelial cell dysfunction associated with low levels of circulating placental growth factor (PlGF) and increased levels of total vascular endothelial growth factor (VEGF), soluble VEGF receptor-1 (sVEGFR-1), and soluble endoglin, a transforming growth factor beta1 and 3 coreceptor. Here, we tested the hypothesis that these altered levels of angiogenic cytokines and of the anti-angiogenic soluble forms of cytokine receptors could be the consequence of hypoxia.


METHODS
Normal human umbilical vein endothelial cells, immortalized first trimester extravillous trophoblast cells (HTR8/SVneo) and first trimester placental villi explants (8-14 weeks) were used for culture under normoxia (20% O(2)) or hypoxia (1% O(2)). Culture media were collected for the measurement of cytokines by enzyme-linked immunosorbent assay. Total RNA was extracted for RT-PCR analysis.


RESULTS
Under hypoxia, villous trophoblast expressed higher levels of VEGF, VEGFR-1, sVEGFR-1 and VEGFR-2 mRNAs (P < 0.001), and secreted more VEGF and sVEGFR-1 proteins (P < 0.05). In contrast, PlGF mRNA and protein were decreased in 1% O(2) (P < 0.001), whereas endoglin (Eng) was not modulated. Additionally, sVEGFR-1 directly abolished VEGF/PlGF-induced angiogenesis in the rat aortic ring assay.


CONCLUSIONS
Our results support the hypotheses that, in pre-eclampsia, (i) overproduction of VEGF family factors by pre-eclamptic placenta is a consequence of induced hypoxia; (ii) overproduction of sVEGFR-1 by hypoxic villous trophoblast accounts for maternal free VEGF depletion; (iii) low circulating level of free PlGF is not only related to sVEGFR-1 overproduction, but also to hypoxia-induced mRNA down-regulation; (iv) Eng is not modulated by hypoxia.
Munaut
Carine
C
Laboratory of Tumor and Development Biology, CRCE, CHU, GIGA, University of Liège, Tour de Pathologie (B23), Sart Tilman B-4000, Liège, Belgium. c.munaut@ulg.ac.be
Lorquet
Sophie
S
Pequeux
Christel
C
Blacher
Sylvia
S
Berndt
Sarah
S
Frankenne
Francis
F
Foidart
Jean-Michel
JM
D000328:Adult; D000818:Animals; D015703:Antigens, CD / Q000378:metabolism*; D002824:Chorionic Villi / Q000378:metabolism*; D015536:Down-Regulation; D000071063:Endoglin; D004730:Endothelium, Vascular / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D015870:Gene Expression; D006801:Humans; D000860:Hypoxia / Q000150:complications*; D000072483:Placenta Growth Factor; D011225:Pre-Eclampsia / Q000378:metabolism; D011247:Pregnancy; D011257:Pregnancy Proteins / Q000378:metabolism; D011261:Pregnancy Trimester, First; D051381:Rats; D011956:Receptors, Cell Surface / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014327:Trophoblasts / Q000378:metabolism*; D014471:Umbilical Veins / Q000166:cytology; D042461:Vascular Endothelial Growth Factor A / Q000096:biosynthesis; D040281:Vascular Endothelial Growth Factor Receptor-1 / Q000096:biosynthesis*
D015703:Antigens, CD; C064206:ENG protein, human; D000071063:Endoglin; C000608036:PGF protein, human; C000608038:Pgf protein, rat; D011257:Pregnancy Proteins; D011956:Receptors, Cell Surface; D042461:Vascular Endothelial Growth Factor A; D000072483:Placenta Growth Factor; D040281:Vascular Endothelial Growth Factor Receptor-1