Imaging The Longitudinal Reduction In Placental Ischemia In Response To Therapeutic Intervention For Preeclampsia

Preeclampsia is believed to be induced by abnormal vascular remodeling and the resulting placental ischemia during early development. Sildenafil, a phosphodiesterase-5 inhibitor, reduces the maternal symptoms of preeclampsia by promoting angiogenesis and enhancing NO-mediated vasodilation. However, the effect of sildenafil on in vivo placental function has not been demonstrated. We performed longitudinal spectral photoacoustic (sPA) imaging of placental therapeutic response to sildenafil in the reduced uterine perfusion pressure (RUPP) model of preeclampsia. Sprague Dawley rats were administered sildenafil (S) via drinking water beginning on gestational day (GD) 11. Imaging was performed on GD14, 16, and 18 with the RUPP procedure implemented after the first imaging session. sPA images of oxygenation show that the placental ischemia induced by the RUPP surgery (RUPP, n=8, 48%; NP, n=8, 54%), was effectively eliminated by treatment with sildenafil (RUPP+S, n=8, 53%, p<0.05). In addition to improved placental oxygenation, sildenafil was also found to reduce mean arterial pressure in RUPP animals by GD18 (RUPP, 110 mmHg; RUPP+S, 98 mmHg; p<0.05), consistent with prior reports. Our studies demonstrate that sPA imaging can detect changes in placental oxygenation which could be used to indicate in vivo placental therapeutic response. Figure 1: Placental hypoxia in the RUPP is improved by treatment with sildenafil on GD16. B-mode US images (a, c) of anatomy were used to manually select the placenta (p) and average placental oxygenation was calculated. A custom red-blue oxygenation colormap was then overlaid for visualization (b, d). Scale bars = 3mm.