Murine CD200+ CK7+ trophoblasts in a poly (I:C)-induced embryo resorption model.
Cytokeratin 7 (CK7) is currently regarded as the best marker for trophoblast cells, while CD200 (OX-2), known as 'tolerance signal', plays an important role in normal pregnancy. In this study, the status of CD200 expression was investigated in BALB/c x C57BL/6 and BALB/c x BALB/c mating combinations designed as allogeneic and syngeneic murine models of induced embryo resorption, in which the resorption rate was boosted by an i.p. injection of poly (I:C), a synthetic double-stranded RNA. The percentage of CD200+ cells in the CK7+ cell population (CD200+ CK7+ percentage) and the absolute number of these cells were determined with flow cytometry, using trophoblast cells collected at day 8.5 and day 13.5 of gestation. The potential effect of poly (I:C) on CD200 expression was also evaluated by detecting the CD200+ CK7+ percentage in trophoblast cells incubated in the presence or absence of poly (I:C), in vitro. The distribution pattern of CD200+ cells at the feto-maternal interface was evaluated by immunocytochemical examination. When 10(4) cells were analyzed at day 8.5 of gestation in each case, no significant difference was observed between the poly (I:C)-treated group and the control PBS group either in the CD200+ CK7+ percentage or in the absolute number of these cells. Similar results were observed both in BALB/c x C57BL/6 mice and in BALB/c x BALB/c mice. However, the CD200+ CK7+ percentage was significantly decreased in the poly (I:C)-treated group when evaluated at day 13.5 of gestation. Accordingly, a dramatically elevated rate of embryo resorption was observed at this time point of pregnancy after the administration of poly (I:C). In addition, the CD200+ CK7+ percentage was significantly lower in trophoblast cells incubated with poly (I:C) at a certain concentration, in vitro, while histocytochemical examination showed the CD200+ cells mainly scattered in placental tissue adjacent to the interface of the placenta and uterus. This indicates that sufficient expression of the CD200 molecule on CK7+ cells at the feto-maternal interface may be necessary for the maintenance of embryos during pregnancy in this rodent model, while poly (I:C) administration may increase embryo resorption, at least partially via direct inhibition of CD200 expression on CK7+ cells.
Lin
Yi
Y
Institute of Tissue Transplantation and Immunology, Jinan University, Guangzhou 510632, China. yilinonline@21cn.com
Zeng
Yaoying
Y
Di
Jingfang
J
Zeng
Shan
S
D000022:Abortion, Spontaneous / Q000276:immunology*; D000818:Animals; D015703:Antigens, CD / Q000276:immunology*; D015415:Biomarkers / Q000032:analysis; D002452:Cell Count; D002478:Cells, Cultured; D020964:Embryo Loss; D005260:Female; D007150:Immunohistochemistry / Q000379:methods; D007369:Interferon Inducers; D053552:Keratin-7; D007633:Keratins / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D023421:Models, Animal; D010920:Placenta / Q000276:immunology; D011070:Poly I-C; D011247:Pregnancy; D014327:Trophoblasts / Q000276:immunology*
D015703:Antigens, CD; D015415:Biomarkers; D007369:Interferon Inducers; D053552:Keratin-7; C507496:Krt7 protein, mouse; D007633:Keratins; D011070:Poly I-C; C042739:antigens, CD200