Antiapoptotic activities of Leukemia Inhibitory Factor (LIF) and Vascular Endothelial Growth Factor (VEGF) in hypoxic human trophoblast depend on gestational age

Susceptibility of the human trophoblast to apoptosis is changing throughout pregnancy. Invasiveness and differentiation of the trophoblastic cells may be severely modulated by hypoxia, well-known apoptosis inducer. From the other hand, local antiapoptotic activities of Leukemia Inhibitory Factor (LIF) and Vascular Endothelial Growth Factor (VEGF) may affect the course of hypoxia-induced programmed cell death. In this study, we examined comparatively (first trimester vs. term pregnancy), whether gestational age as well as LIFand/or VEGF-dependent changes in functional status of the cultured trophoblast cells influence apoptotic activity in hypoxic conditions. Placental specimens were obtained after abortions in the first trimester (Group I) and after deliveries at term (Group II). The cytotrophoblast cells were isolated using Kliman’s method, based on enzymatic digestion and a Percoll gradient centrifugation. Established cultures within both groups were divided into 3 subgroups: LIF(10ng/mL), VEGF(100ng/mL) and LIF+VEGF-treated, cultured under hypoxia (2% O2) for 48 hours. After this period, quantitative determination of apoptosis was performed using ELISA, with cytokeratin-18 as an apoptosis marker. LIF, VEGF and LIF+VEGF reduced intensity hypoxia-related apoptosis. This effect was stronger in the first-trimester trophoblasts. The differences in mean decrease of apoptosis intensity between Group I and II were significant (p<0.05) and amounted to 76.09, 43.72 and 68.45 % (LIF-, VEGFand LIF+VEGF-treated cultures, respectively). Protective mechanisms induced by LIFand VEGF within trophoblast cells may be responsible for the relative resistance to hypoxia and consequently apoptosis, especially in the first-trimester of pregnancy. Key-Words: apoptosis, hypoxia, human trophoblast, leukemia inhibitory factor, vascular endothelial growth factor