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  • Title: Genome multiplication in the tertiary giant trophoblast cells in the course of their endovascular and interstitial invasion into the rat placenta decidua basalis.
    Author: Zybina TG, Zybina EV.
    Journal: Early Pregnancy (Cherry Hill); 2000 Apr; 4(2):99-109. PubMed ID: 11723540.
    Abstract:
    Processes of invasion of the tertiary giant trophoblast cells (tGTCs) into the uterine wall in the course of implantation of the rat embryo at 10-15 days post coitum (dpc) were studied. Reproduction of tGTCs was evaluated using 3H-thymidine incorporation and cytophotometric measurement of the nuclear DNA content. 1. Patterns of trophoblast invasion. Two patterns of invasion were observed: endovascular (from 10 to 15 dpc) and interstitial (from 12 to 15 dpc), via extracellular matrix of endometrial stroma towards the central arterial channel. The both types of the tGTC invasion seem to take part in modification of the arterial wall. The tGTCs were shown to differentiate from cambial trophoblast cells of ectoplacental cone (EC) or junctional zone of placenta. 2. Peculiarities of reproduction of tGTCs. By the start of the endovascular and interstitial migration, tGTCs lose completely their capability for mitotic divisions and are found autoradiographically to stop incorporation of 3H-thymidine soon after beginning of their migration. Cytophotometric measurements of the nuclear DNA content have shown tGTCs to be polyploid. Their degree of ploidy is mainly 8-32c, which is by 1-2 classes of ploidy higher than that of the initial cambial cell populations of ectoplacental cone (EC) and junctional zone trophoblast cells (JTCs). Since the replication processes in tGTCs are limited, their polyploidization seems to occur within cambial populations of the trophoblast cells. The final genome multiplication cycles in the beginning of the tGTC invasion can be accomplished only via endoreduplication, i.e., with the complete elimination of the mitotic mechanism. The not too high level of tGTC ploidy, 8-32 c, probably does not prevent the tGTC deep invasion against the blood flow and through the extracellular matrix and may be of a protective significance in their interrelations with allogenic maternal tissues.
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