(865) Toll-like Receptor 9 (TLR9) suppression restores endothelial function in the maternal placental microvasculature in preeclampsia.

Objective: We have previously shown that endothelial function in the human placental microcirculation is impacted by excessive oxidative stress and TLR9 may be part of this mechanism.  Therefore, to evaluate whether TLR9 knockdown restores vascular function in preeclamptic microvessels.

Study Design: Placental microvessels (< 150µM diameter) were dissected from the maternal side of control or preeclamptic placentas and then incubated with media and scrambled siRNA or TLR9-specific siRNA (50nM) for 12-16 hours. Vessels were cannulated on glass micropipettes, pressurized to 60mmHg, and then pre-constricted with 0.1-2.0 nM endothelin-1. A pressure gradient was applied to induce flow and vessel inner diameters were measured by videomicroscopy. Flow-mediated dilation (FMD) was calculated as a % of maximum diameter and expressed as mean ± SEM. Results were analyzed by two-way ANOVA with Dunnett’s multiple comparisons. The maximum dilation values were evaluated by a Kruskal-Wallis test with Dunn’s multiple comparative test or t-test as appropriate.

Results:

Preeclamptic microvessels demonstrated impaired endothelium-dependent vasodilation compared to healthy controls (Fig. A, p=0.0018). Vasodilator capacity in healthy controls was not significantly impacted by siRNA treatment (Fig. B, p=0.4429). TLR9 siRNA restored impaired endothelium-dependent vasodilation to flow compared to both untreated and scrambled siRNA-transfected vessels from patients with preeclampsia (Fig. C, p=0.0082).


Conclusion: Suppression of TLR9 expression restores endothelium-dependent vasodilation to flow in preeclamptic vessels and merits further evaluation.