Evidence for oxygen-derived free radical mediated damage to first trimester human trophoblast in vitro

Abstract

We have found that, despite considerable experimentation with conditions, we are unable to maintain first trimester syncytiotrophoblast in a viable state in organ culture (conventional conditions i.e. in buffered culture medium supplemented with serum, maintained at 37°C/21% oxygen/5% carbon dioxide). Evidence for syncytiotrophoblastic degeneration includes: parallel release of LDH and HCG, widespread NΣ-Dansyl-1-Lysine uptake, indicating cell death, and extensive vacuolation observed via electron microscopy. These results suggest syncytial death occurs within hours of culture initiation. Despite this the cytotrophoblasts and stromal cell populations showed good viability for a number of days as shown by BrdU incorporation. When investigating the effect of oxygen tension on tissue survival we found that lipid peroxidation was considerably increased under ambient (21%) rather than low (2.5%) oxygen conditions. Furthermore, keeping early villous tissue at 2.5% oxygen reduced the rate of HCG as well as LDH release and also improved the ultrastructural appearance of the syncytiotrophoblast. We subsequently discovered that mitochondrial activity within the syncytiotrophoblast declined to virtually zero within six hours of cultureat 21% O 2 but was retained for this period at 2.5% O 2 . Second trimester tissue, however, showed mitochondrial activity following 6 hours of culture at 21% O 2 . These results suggest that the syncytiotrophoblast is acutely sensitive to oxygen during the first trimester but becomes more resistant by 14 weeks gestational age, probably due to an increase in the capacity of the mechanisms which defend cells against oxidative stress.