(502) Elevated levels of circulating endothelial cells in pregnancies complicated by preeclampsia and/or fetal growth restriction

We used model human umbilical vein endothelial cells (HUVECs) to develop a 4-parameter immunofluorescence assay (IF) on the established RareCyte® liquid biopsy platform with the following markers: Sytox (nucleus), VE-Cadherin (CD144, positive CEC marker #1), MCAM (CD146, positive CEC marker #2), and CD45 (white blood cell exclusionary marker). CECs were defined as nucleated cells, negative for CD45, and positive for either or both CD144 and CD146. Using the HUVEC spike-in model system, we analytically validated assay performance by evaluating specificity, sensitivity and limit of detection across clinically relevant CEC count ranges. In clinical studies, CEC numbers in healthy, non-pregnant female subjects of child-bearing age (20-40 years old; N=10) were compared to third trimester pregnancy samples (N=17 total, including N=9 uncomplicated, N=8 FGR, N=5 PE, N=3 FGR + PE).  All pregnant subjects were enrolled after informed consented at Swedish Medical Center, Seattle, WA.

Results:

Analytic validation studies demonstrated sensitivity and specificity of CD144 and CD146 of 99 – 100% and lower limit of detection of 1 cell in >1 million.  CEC count was higher in pregnancy compared to non-pregnant reproductive age subjects and was higher in pregnancies with PE +/- FGR compared to those with uncomplicated outcomes.  Results are shown in Figure 1A and B.

Conclusion:

We have developed a robust assay for enumeration of CECs in pregnancy.  Elevated levels of CECs in third trimester pregnant patients were observed in both PE and FGR relative to healthy third trimester pregnancies.  These preliminary studies support further investigation of CEC enumeration as a predictive biomarker of pregnancy complications.