Myeloid cell alterations in the mouse placenta precede the onset of labor and delivery.
OBJECTIVE
Immature myeloid cells (IMCs) are bone marrow-derived cells that normally differentiate into granulocytes, macrophages, and dendritic cells (DCs) but expand in pathological conditions such as malignancy. DCs are antigen-presenting cells that regulate the immune response. Both IMCs and DCs were shown to take part in angiogenesis; however, little is known of their function in the placenta. We sought to determine whether alterations in DC and IMC populations in the placenta precede the onset of delivery.


METHODS
Experiments were performed on 6-8 week old C57Bl/6 female mice. Placentas from pregnant mice that were killed on designated days, immunostained using fluorescently labeled anti-CD11b, Gr-1, CD11c, major histocompatibility II (MHCII), and CD45, and analyzed by flow cytometry and immunofluorescent microscopy.


RESULTS
Throughout the latter part of pregnancy toward labor and delivery, the CD45(+)CD11b(+)Gr1(+)-IMC population decreased 29 ± 9.1% (day 12) and 30 ± 9.9% (day 15), vs 21 ± 8.1% (day18, n = 21, 15, and 27; P = .006 and P = .004, respectively), whereas the CD45(+)CD11c(+)MHCII(+)-DC population increased 0.87 ± 0.3% (day 12) and 0.70 ± 0.3% (day 15) vs 1.81 ± 1.3% (day 18, n = 21, 15, and 27, P = .002 and P = .001, respectively). Both myeloid cell populations were localized adjacent to CD31(+) endothelial cells in sites of placental angiogenesis.


CONCLUSIONS
Labor and delivery are preceded by proangiogenic-myeloid cell alterations, reflected by a decrease in IMCs and an increase in DCs populating the mouse placenta. The intriguing possibility that delivery is preceded by the maturation of IMCs in part into DCs warrants further studies.
Laboratory for Reproductive Immunology, Department of Obstetrics and Gynecology, Hillel Yaffe Medical Center, Faculty of Medicine, Technion-Israel Institute of Technology, Israel. Electronic address: ofainaru@techunix.technion.ac.il.
Ofer
O
Fainaru
Laboratory for Reproductive Immunology, Department of Obstetrics and Gynecology, Hillel Yaffe Medical Center, Faculty of Medicine, Technion-Israel Institute of Technology, Israel.
Gili
G
Paz
Laboratory for Reproductive Immunology, Department of Obstetrics and Gynecology, Hillel Yaffe Medical Center, Faculty of Medicine, Technion-Israel Institute of Technology, Israel; Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel.
Shay
S
Hantisteanu
Laboratory for Reproductive Immunology, Department of Obstetrics and Gynecology, Hillel Yaffe Medical Center, Faculty of Medicine, Technion-Israel Institute of Technology, Israel.
Mordechai
M
Hallak
D000818:Animals; D003713:Dendritic Cells / Q000502:physiology*; D005260:Female; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D007745:Labor Onset / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D022423:Myeloid Cells / Q000502:physiology*; D018919:Neovascularization, Physiologic / Q000502:physiology*; D010920:Placenta / Q000166:cytology* / Q000502:physiology; D011247:Pregnancy
angiogenesis; dendritic cells; immature myeloid cells; placenta