Development of an in vitro Model for Bovine Placentation: A Comparison of the in vivo and in vitro Expression of Integrins and Components of Extracellular Matrix in Bovine Placental Cells

Abstract

Background/Aims: Interaction of trophoblastic integrins with the extracellular matrix plays a role in embryo implantation and trophoblast invasion. The phenomenon of restricted trophoblast invasion, observed in the bovine epitheliochorial placenta offers intriguing conditions to study invasive processes. The migration of bovine trophoblast giant cells is accompanied by the expression of specific integrins and corresponding extracellular matrix ligands. Methods: Primary cultures of different cell populations from cow placentomes were established and characterized, and in vitro phenotypes were compared with in vivo conditions by immunofluorescence. Results: Propagated epithelial cells were positive for cytokeratin and vimentin, while fibroblasts contained α-smooth muscle actin, desmin and vimentin. Epithelial cells coexpressed integrin subunits α₆ and β₁ with laminin, and fibroblast cells were positive for α_v, β₃, fibronectin and laminin. In contrast to cells in vivo, cultured epithelial cells secreted fibronectin, while collagen IV was not detected. The occurrence of integrin subunits was confirmed at mRNA level by RT-PCR. Conclusion: We have established cell cultures isolated from maternal and fetal components of bovine placentomes expressing typical cytoskeletal filaments and integrin receptors also present in their in vivo counterparts. These bovine placentomal cells provide a suitable in vitro model for the study of cell-cell interactions.