Developmental changes in the fine structure of the chorion laeve (Smooth chorion) of the rhesus monkey placenta

Abstract

Developmental changes in the fine structure of the chorion laeve (smooth chorion) of the rhesus monkey were studied at two time periods during gestation: 1) Early (19-60 days of gestation), before the chorionic epithelium fuses with the parietal decidua, and 2) near term, when the fused chorioamnion has also fused with the parietal decidua. Early in gestation the chorionic epithelium consisted of columnar and cuboidal cells one or two layers thick. The apical border of the cells had microvilli and coated pits, and adjacent cells were joined by tight junctions and desmosomes. The chorionic epithelial cells during this early period contained numerous large vesicles and vacuoles of varying electron-density. The apical cytoplasm contained various small coated vesicles and tubules. Taken together these observations were interpreted as indicating a possible role for these cells in endocytosis or phagocytosis of substances from the uterine lumen; i.e., a potential role in histiotrophic nutrition during this early period. Late in gestation the trophoblastic cells were more irregular in shape. The cells contained abundant granular endoplasmic reticulum (ER) and mitochondria, and a well-developed Golgi complex, suggesting the cells were actively synthetic late in gestation. The numerous cytoplasmic vacuoles characteristic of the trophoblastic cells of early gestation were absent near term. Glycogen deposits and lipid droplets were moderately well-developed near term. Most of the cells were joined by desmosomes but wide intercellular spaces, unobstructed by any cell junctions, were frequently observed. This observation provides at least one explanation for the increase in permeability of the chorion laeve later in gestation. Cells of the parietal decidua associated with the chorion laeve were also examined. These cells generally had a well-developed granular ER and Golgi apparatus, and numerous mitochondria. Limited numbers of membrane-bounded secretory bodies, similar to those in human decidual cells, were also present.

Differentiation of the chorionic plate of the placenta: Cellular and extracellular matrix changes during development in the macaque

“…Additional immunohistochemical analyses are needed to resolve this issue. The presence of microfibrils was consistent with earlier studies of macaque amnion, chorion laeve, and cytotrophoblastic shell where similar microfibrils were abundant (King, 1980(King, , 1981Blankenship, 1993, 1994). Microfibrils have also been described in human fetal membranes (Modesti et al, 1984;Aplin et al, 1985;Malak et al, 1993).…”

Plasmodium coatneyi in the rhesus monkey (Macaca mulatta) as a model of malaria in pregnancy.

“…The macaque placenta is anatomically similar to that of humans [24][25][26][27][28][29][30] and produces progesterone 21 as does the human placenta. Organogenesis in macaques is also comparable with humans.…”

Transport of horseradish peroxidase across monkey trophoblastic epithelium in coated and uncoated vesicles

“…The ultrastructure of the membranous chorion of the rhesus monkey placenta early in gestation has been described in detail elsewhere (King, 1981). Therefore, only those features pertinent to this study will be described, specifically the vacuolar apparatus which includes the endocytic complex and Golgi-lysosomal system.…”

“…As a result of superficial implantation in the macaque monkey, the membranous chorion is exposed to the uterine lumen during early gestation. Morphological studies have suggested that this epithelium may be absorptive, possibly taking up macromolecules from the uterine lumen (King, 1981). The suggestion is also supported by the observations that similar cells in other species have been shown to have a n absorptive or phagocytic function (for references see Dantzer, 1982;Burton, 1982;King, 1982a,b;1984).…”

“…The membranous chorion of the macaque monkey placenta is composed of a columnar trophoblastic epithelium backed by a relatively avascular connective tissue (King, 1981). As a result of superficial implantation in the macaque monkey, the membranous chorion is exposed to the uterine lumen during early gestation.…”