Cell cycle progression and different ways of cell and genome reproduction in the invasive trophoblast cells of the silver fox placenta

ABSTRACT

Relationship between cell cycle progression and different ways of cell and genome reproduction (regular mitotic cycle, polyploidizing mitoses, endoreduplication, depolyploidization) has been studied in the course of development of invasive trabecular trophoblast cell population in the silver fox placenta (Vulpes fulvus Desm.) Cell cycle progression was estimated using Ki-67 immunolabeling. In the region adjoining the endometrium the trophoblast cells keep their mitotic activity, giving rise to diploid or low-polyploid cells via polyploidizing (reduced) mitoses. In the depth of the spongy zone where some trophoblast cells migrate inside the fetal part of placenta, some cells switch to endocycles – polytenization and endomitosis. Judging by the Ki-67 labeling patterns, polytenization correlates with the persistence of cell cycles for a long time and takes part in retention of potential of cell/genome reproduction as well as achievement of the highest ploidy level (up to 256c). Meanwhile, other endoreduplicated cells leave the cell cycle with subsequent cell degradation. Classical endomitosis may be a mode of genome multiplication and correlate with both the persistence and attenuation of cell cycles. Depolytenization and depolyploidization often correlate with attenuation of Ki-67 expression followed by cell degradation. However, in a minor trophoblast cell population, non-mitotic genome segregation most probably takes part in retention of cell reproductive potential.

KEYWORDS:

• Cell cycle
• endomitosis
• fox
• invasion
• Ki-67
• polyteny
• trophoblast

Acknowledgments

The authors are grateful to Prof. Kazimir M. Pozharisski for providing the antibodies and other reagents and help in immunohistochemistry.

Disclosure statement

No potential conflict of interest was reported by the authors.