INTRODUCTION: Failure of the trophoblast to appropriately invade uterine spiral arteries is an initiating event in preeclampsia, a disorder characterised by hypertension and endothelial dysfunction. A dyslipidemia (low plasma levels of high density lipoproteins (HDL) and elevated triglycerides) has also been described in preeclampsia. The pro-inflammatory cytokine TNF-α inhibits trophoblast invasion of uterine endothelial cells. The effect of apoliopoprotein A-I, the main apolipoprotein component of HDL, on trophoblast incorporation into endothelial tubules ±TNF-α is investigated using the in vitro HTR-8/SVneo-Uterine endothelial cell (Tr-UEc) co-culture model.
OBJECTIVES: This study asks if apoA-I, which has established anti-inflammatory properties, can protect against the deleterious effect of TNF-α on trophoblast-endothelial cell interactions.
METHODS: The Tr-UEc co-culture model was used to investigate the effect of apoA-I on trophoblast incorporation into endothelial tubules ±TNF-α. UtMvEcs were pre-incubated with lipid free apoA-I (final apoA-I concentration 1mg/mL) for 16hrs prior to seeding onto matrigel. Tubules formed within 4hrs. Fluorescence-labelled HTR-8/SVneo trophoblast cells were then co-cultured with the endothelial cells ±TNF-α (final concentration of 0.2ng/mL). Live Cell Imaging techniques (Zeiss Axiovert) captured the integration in real time, bright field and fluorescent images were captured after 24hrs. The effect of TNF-α on trophoblast cell invasion was quantified with ImageJ software.
RESULTS: TNF-α inhibited trophoblast cell integration into endothelial tubular structures by 24.1±3.7% (p<0.001). This effect was reversed when the endothelial cells were pre-incubated for 16hrs with lipid free apoA-I (p<0.001 compared to non-incubated cells). Live cell images clearly demonstrate a disruption to the normal integration of trophoblast into endothelial tubular structures in the presence of TNF-α. The protective effect conferred by pre-incubation of endothelial cells with apoA-I against TNF-α is clearly visible.
CONCLUSION: apoA-I enhances trophoblast-endothelial cell integration in the presence of a pro-inflammatory stimulus. A healthy lipid profile may affect pregnancy outcomes by priming endothelial cells in preparation for trophoblast invasion.