Development, Degradation and Possible Function of Trabecular Trophoblast in the Course of Placentation of Silver fox Vulpes fulvus Desm.

Abstract

Aims: Development of trabecular trophoblast cell population in the spongy zone of the endotheliochorial silver fox placenta was investigated with special attention to cytokeratin intracellular arrangement. Methodology: Cytokeratin immunohistochemistry. Results: It was shown that keratin filaments contribute to formation of carcass of trabeculae, especially in the zone attached to endometrium In the course of placenta development, in the deep part of spongy zone, there occured progressive detachment of the trophoblast cells out of the trabeculae and acquirement of «migratory» phenotype characterized by specific arrangement of the cytokeratin filaments. Another part of differentiated trabecular trophoblast cells undergo progressive destruction of the cytokeratin filaments that results in complete desintegration of cytoplasm. As a result, a zone filled by products of destruction of the trabecular trophoblast cell is formed between trabeculae and labyrinth. Conclusion: In the silver fox placentation there are several ways of migration of trophoblast cells that play a role in feto-maternal contacts and in histiotrophic nutrition. First, invasion of trophoblast in the depth of uterine glands with partial replacement of glandular epithelium. Second, detachment of the trophoblast cells into the lumen of trabeculae that is accompanied by acquirement of «migratory phenotype» with specific arrangement of cytokeratin filaments. The nutrients that result from degradation of the trabecular trophoblast cell may be uptaken by the labyrinth, i.e. the main site of supply of nutrient and oxigen to embryo.