Characterization of the bovine placenta by cytoskeleton, integrin receptors, and extracellular matrix.

The cytoskeleton together with integrin receptors and proteins of the extracellular matrix provide sensitive indices of the development and organization of the bovine placenta. The bovine placenta is classified as synepitheliochorial because migrating trophoblast giant cells fuse with single uterine epithelial cells. This phenomenon may be interpreted as a restricted trophoblast invasion. Bovine placentomes from early placentation until term can be characterized by indirect immunohistochemical methods. In order to do so, placental tissues are snap-frozen in liquid nitrogen or perfusion-fixed in formalin and embedded in paraffin. Depending on the antibodies used, the different cell types within the cow placenta are identified either on frozen sections or on paraffin sections according to the expression of different cytoskeletal filaments (alpha smooth muscle actin, different cytokeratins, desmin and vimentin). The specific expression of integrin receptors (subunits alpha1, alpha2, alpha3, alpha4, alpha5, alpha6, alpha(v), beta1, beta3, and alpha4) as well as proteins of the extracellular matrix (collagens type I and IV, fibronectin, and laminin) in the different cell populations is also examined.