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The effects of oxygen concentration and gestational age on extravillous trophoblast outgrowth in a human first trimester villous explant model.

BACKGROUND
In the first trimester of human pregnancy, extravillous trophoblasts from placental villi invade the decidua temporarily occluding the spiral arteries, preventing maternal blood flow and creating a low-oxygen environment, which is believed to play an important role in the regulation of extravillous trophoblast outgrowth. This work aimed to quantify the effects of gestational age and oxygen concentration on extravillous trophoblast outgrowth.


METHODS
A quantitative first trimester villous explant model was used to measure the frequency and area of extravillous trophoblast outgrowths from villi grown in 1.5 or 8% oxygen.


RESULTS
The percentage of explants producing outgrowth declined independently of oxygen concentration as gestation increased from 8 to 12 weeks. Culture in 1.5% oxygen significantly reduced the frequency and area of outgrowths in comparison with 8% oxygen. HLA-G and alpha1 integrin were both expressed throughout outgrowths, with no difference in the expression between oxygen concentrations. Gestation influenced the response of explants to oxygen, with a significant differential response to oxygen concentration in placentae under 11 weeks of gestation, whereas in villi from placentae of 11 or 12 weeks, no differential response was observed.


CONCLUSIONS
In the first trimester, oxygen and gestational age both regulate extravillous trophoblast outgrowth.