Barry F. King

Macaque intra-arterial trophoblast and extravillous trophoblast of the cell columns and cytotrophoblastic shell express neural cell adhesion molecule (NCAM).

During placental development in higher primates trophoblast cells originating in the cell columns migrate along endometrial surfaces to form the cytotrophoblastic shell. A subpopulation of these cells invades uterine arteries, where they migrate on the surface of endothelium, against the flow of blood. These intra‐arterial cells become sequestered in the walls of the arteries where they are referred to as intramural trophoblast. Because migration depends upon binding the cell surface to other cells or to extracellular matrix, we investigated the potential role of neural cell adhesion molecule (NCAM, CD56) in arterial invasion by trophoblast cells.

Immunohistochemical localization of fibrillin in developing macaque and term human placentas and fetal membranes

The objective of this study was to examine the developmental appearance of the extracellular matrix glycoprotein fibrillin in macaque placentas and fetal membranes and to compare this distribution to that seen in term human placentas and fetal membranes. Standard immunoperoxidase methods were used on paraformaldehyde‐fixed, paraffin‐embedded tissues. At early gestational ages (26–30 days), fibrillin was found in cell columns and cytotrophoblastic shell, with weak staining in the villous stroma. Staining was abundant in the shell and columns at 53 days as well, and stronger staining was seen in the stroma of the chorionic plate and stem villi. Staining in the shell and remnants of the cell columns in later gestation continued to be positive, though variable. Generally, the strongest staining was present in the distal cytotrophoblastic shell. Stroma in the tips of anchoring villi was also strongly positive. Later in gestation, fibrillin was observed around the multilayered cytotrophoblast of the chorionic plate. Fibrillin was abundant in the stromal cores of human term placental villi. In early macaque amnion, fibrillin staining was abundant in a layer beneath the amniotic epithelium. Later in gestation, macaque chorioamnion staining was generally similar to human term chorioamnion staining, with the heaviest staining in portions of the compact and reticular layers. Fibrillin was sometimes localized in regions known to be rich in connective tissue microfibrils, but, in other regions known to have abundant microfibrils, fibrillin staining was weak. This suggests that some microfibrils in placenta may be composed predominantly of some other protein(s). The function of fibrillin in the various placental compartments is unknown at present. It may provide attachment points for cells while at the same time providing a strong, yet flexible, matrix to accommodate growth particularly in areas subject to shear stress. Microsc. Res. Tech. 38:42–51, 1997.

Development and Organization of Primate Trophoblast Cells

An account of the development and organization of trophoblast in any group of mammals is a complex task, and this is particularly true for the primates. Part of the difficulty is due to quite different types of placentation found among different members of the order, but the most complex aspects are the constantly changing spatial relationships that trophoblast has with various maternal tissues over the course of gestation. In this overview of primate trophoblast we will examine: (i) the characteristics of the trophoblast of lower primates, (ii) the early development and differentiation of trophoblast in higher primates, and (iii) the development and organization of the heterogeneous trophoblast populations present in higher primates in later gestation. These populations include villous cytotrophoblast and syncytiotrophoblast and a variety of extravillous populations. These include trophoblast of the cell columns and the trophoblastic shell, interstitial trophoblast invading through endometrial stroma, endovascular trophoblast migrating up the spiral arteries, trophoblast of the chorion laeve, and deported trophoblast that enters the uterine veins and is carried to extrauterine sites. The diverse attributes of these related trophoblast populations are just beginning to be appreciated.