The timing and duration of hypoxia determine gene expression patterns in cultured human trophoblasts

Objective: Exposure of cultured trophoblasts to hypoxia is commonly used to interrogate the molecular mechanisms underlying placental hypoxic injury. We examined the effect of levels, durations, and patterns of hypoxia on gene expression patterns in primary human trophoblasts. Study design: We exposed primary term human trophoblasts to either standard culture conditions (O ₂= 20%) or to static or alternating levels of oxygen (O₂= 8%, or O₂= 0%) either early or late in culture, and analyzed the expression of 34 genes that are known to be regulated in placentas from pregnancies complicated by fetal growth restriction (FGR). Results: Using multidimensional scale analysis, Euclidean distance, and hierarchical clustering, we found that gene expression patterns in cells exposed to O ₂= 8% were similar to patterns observed in O₂= 20%, but more distant from patterns in O₂= 0%. Alternating atmospheric oxygen (8% vs. 0%) yielded intermediate results. Changes in oxygen levels over a longer period had a greater effect on gene expression than short-term changes. Gene expression patterns in cultured trophoblasts did not fully capture expression patterns observed in biopsies from FGR placentas vs. control. Conclusions: The level, duration, and patterns of hypoxia are critical in determining trophoblast gene expression, and therefore germane for analysis of trophoblast hypoxic injury.