Characterizing Pregnancy Outcomes in a Humanized Mouse Model of Sickle Cell Disease

Background: Sickle cell disease (SCD) is a group of hereditary disorders commonly associated with the distortion of red blood cells (RBC) at low oxygen levels. It is characterized by complications such as vaso-occlusion, anemia, and hemolysis. These complications are lifelong and become extremely relevant during periods of increased physiological stress such as pregnancy. Pregnancy in sickle cell disease (SCD) is associated with an increased risk of complications including, pre-term delivery, deep vein thrombosis, intra-uterine growth restriction, pre-eclampsia, and intra-uterine death. Recent meta-analyses have shown that women with SCD are at 26x greater risk for maternal mortality than their healthy counterparts; a figure which, despite the adoption of improved care plans, has shown little to no significant improvement over the last two decades. While impaired vascular maintenance underlies multiple complications of pregnancy outside of sickle cell disease, it is especially relevant to, and characteristic of sickle cell-related pathologies at baseline and is highly likely to be exacerbated as pregnancy proceeds. Through this study we aimed to characterize the effects of SCD-related vasculopathy on pregnancy outcomes and overall placental health using the Townes humanized mouse model of SCD. Methods: SS (sickle hemoglobin) and AA (normal hemoglobin) mice underwent timed breeding to produce pregnant dams. These dams were housed under normal conditions until 17.5 days post conception (dpc), at which point they began undergoing procedures for analysis including 24-hour urine collection, high-resolution ultrasound analysis (18.5dpc), and post-mortem analysis of pregnancy outcomes and tissue collection (18.5dpc). Included in this report are gross pregnancy outcomes, histological assessments of placental tissue, and reports from ultrasound analysis including 3-D volume measures, placental vascularization renders, and laser-Doppler assessment of uterine and umbilical arteries. Continuing research efforts will further utilize tissues from this study to evaluate the biochemical interactions influencing poor pregnancy outcomes related to SCD. Results: These studies show that the SCD mice recapitulate many similarly poor outcomes as women. We observed: reduced litter sizes (AA 6.9 ± 1.5 embryos vs SS 5.2 ± 1.2 embryos**), fetal weight (AA 0.49 ± 0.14g vs SS 0.38 ± 0.16g*), viability of embryos (AA 100.0% IQR 0.0 vs SS 20.0% IQR 33.3***), and maternal mortality (AA