Placenta Development and Ki-67 Nuclear Immunolocalization in Placental Tissues of the Wild Type and Domesticated Silver Fox (Vulpes fulvus Desm.)

Abstract

Aims: To study development of placenta in wild type and domesticated silver fox with special reference to  cell cycle progression of the invasive trophoblast cells. Study Design: Immunohistochemistry with cytokeratin and CD34 primary antibodies to evaluate trophoblast, epithelium and blood vessel arrangement. Semiquantitative evaluation of Ki-67 immunolocalization to characterize involvement of the cells in cell cycle during placenta development. Place and Duration of the Study: Institute of Cytology RAS, St.-Petersburg, Institute of Cytology and Genetics, Novosibirsk, Institute of Radiology and Surgical technologies,  Saint-Petersburg, between March 2014 and July 2015. Methodology: Paraffin-embedded placentae of wild type and domesticated silver fox at the 19-22 day of gestation were sectioned and stained with hematoxylin/eosin and immunostained with standard procedure. Percentage of nuclei of different patterns of Ki-67-immunolocalization was calculated. Results: Endotheliochorial placenta development in the silver fox Vulpes fulvus Desm. includes invasion of endometrial glands by the trophoblast cells. Immunohistochemical Ki-67 reaction demonstrated high incidence of cell cycle progression in the invasive trophoblast cells of spongy zone of placenta at early developmental stages (19 day of gestation) followed by  decrease of Ki-67 immunopositivity at the later stages (21-22 days) in both genotypes. Attenuation of Ki-67 expression starts from the loss of labeling of chromatin while labeling of nucleoli persists for a longer time. Conclusion: Invasive trophoblast cells show high capability of cell cycle progression that attenuate by the time of definitive endotheliochorial placenta development both in wild type and domesticated silver fox placenta.