Rivka Frankel, Gili Paz, Shay Hantisteanu, Ofer Limonad, Mordechai Hallak, Ofer Fainaru

Laboratory for Reproductive Immunology, Department of Obstetrics and Gynecology, Hillel Yaffe Medical Center, Faculty of Medicine, Technion – Israel Institute of Technology, Israel

Introduction: Immature myeloid cells (IMCs) are generated in the bone marrow and expand

in malignant states. We have shown that IMCs populate the placenta and actively promote angiogenesis in mice and humans. Dendritic cells (DCs) that can differentiate from IMCs, are

immune cells that coordinate immune responses. They were shown to promote angiogenesis

during early pregnancy, especially during implantation. Very little is known about their function in the placenta and in the latter part of pregnancy when significant angiogenesis takes part. The pathophysiology of preeclampsia (PE) may be attributed to impaired placentation and angiogenesis during early pregnancy.  This in turn may lead to increased blood supply demands by an hypoxic fetoplacental unit in the latter part of pregnancy.

We sought to determine whether alterations in myeloid cell populations within the placenta, i.e IMCs and/or DCs, precede the onset of delivery and in pregnancy complications such as PE.

Materials and methods: Human placentas were obtained from normal vaginal deliveries (NVD) and cesarean-sections (CS) or from pregnancies complicated by PE. Placentas were immunostained and analyzed using flow cytometry.

Results: The DC population in the human placenta was higher in placentas derived from NVD  compared to elective CS (6.7±3.36% vs. 4.7±1.98%, n=41, P=0.03).

The IMC population in placentas derived from patients with preeclampsia was significantly higher as compared with those obtained from healthy controls (17.7±7.35% vs. 9.4±3.8%, n=14, P=0.018).

Conclusions: In human pregnancies, the DC population increases prior to labor (NVD), as compared to placentas obtained in the absence of labor (CS). The possibility that the onset of labor and delivery is preceded by the maturation of IMCs into DCs is intriguing. In preeclampsia, we observed an increase in the IMC population within the placenta. This may result from a hypoxic placenta and the need for increased angiogenesis. The roles of IMCs in other pregnancy complications such as IUGR and pre-term labor are the subject of our current study.