Blastocyst implantation in the Chinese hamster (Cricetulus griseus)

Embryonic development of the Chinese hamster (Cricetulus griseus) was studied from the onset of implantation to the formation of the parietal yolk sac placenta. Implantation began on day 6 of pregnancy, when the embryo became fixed to the uterine luminal epithelium. At this time there was no zona pellucida, and microvilli of the trophoblast and uterine epithelium were closely apposed. Stromal cells immediately adjacent to the implantation chamber began to enlarge and accumulate glycogen. By day 7 the mural trophoblast penetrated the luminal epithelium in discrete area. The trophoblast appeared to phagocytize uterine epithelial cells, although epithelium adjoining the points of penetration was normal. In other areas nascent apical protrusions from the uterine epithelium indented the surface of the trophoblast. The epiblast had enlarged and both visceral and parietal endoderm cells were present. The well-developed decidual cells were epithelioid and completely surrounded the implantation chamber. On day 8 the uterine epithelium had disappeared along the mural surface of the embryo. The embryonic cell mass was elongated and filled the yolk sac cavity. Reichert's membrane was well developed. The uterine epithelial basal lamina was largely disrupted, and the trophoblast was in direct contact with decidual cells. Primary and secondary giant trophoblast cells were present and in contact with extravasated maternal blood. The mural trophoblast formed channels in which blood cells were found in close proximity to Reichert's membrane. Decidual cells were in contact with capillary epithelium and in some cases formed part of the vessel wall. Structural changes occurring in the embryo and endometrium during implantation in the Chinese hamster are described for the first time in this report and are compared to those described for some other myomorph rodents.

Modulators of cyclic AMP metabolism induce syncytiotrophoblast formation in vitro

During placental development cytotrophoblast stem cells fuse to form the syncytiotrophoblast, a multinucleate cytoplasm with a brush border in contact with the maternal blood. Biochemical differentiation including the expression of placental-specific proteins and hormones accompanies this maturation. However, the biochemical mechanisms responsible for these events are unknown. We have defined a system in which single cytotrophoblast-like cells of the human choriocarcinoma (BeWo) cell line undergo fusion and extensive morphological differentiation following their treatment with effectors of cyclic AMP metabolism. Forskolin incubation caused a dose-dependent increase in intracellular and secreted cyclic AMP and a coordinate fusion of cells which yielded syncytia containing hundreds of nuclei per cytoplasm and a mature dense "placental-like" brush border. These fused cells also synthesized and secreted large amounts of both subunits of chorionic gonadotropin. However, they continued to synthesize several other placenta-specific proteins--placental-like alkaline phosphatase, placental lactogen, and SP1--at rates similar to those in control cells. Other reported effectors of cyclic AMP metabolism also induced cell fusion, although theophylline, an inhibitor of phosphodiesterase, induced fusion by a cyclic AMP-independent mechanism. Additionally, unlike the case with forskolin, treatment of BeWo cells with theophylline did not induce other morphological features of mature syncytiotrophoblasts. Thus, this system will allow one to examine the biochemical mechanism of placental cell fusion in the absence of other variables of cell differentiation.

Isolation and characterization of 5T4, a tumour-associated antigen

The monoclonal antibody (MAb) 5T4 defines a human trophoblast antigen marker with a restricted pattern of expression in normal adult tissues but this antigen is expressed on a variety of carcinomas. The purification of 5T4 antigenic molecules is described from term syncytiotrophoblast by a combination of lectin- and immunoaffinity chromatography and gel filtration giving up to 10,000-fold purification with 70% yield. The antigen is carried by non-associated glycoprotein molecules with an apparent molecular weight of 72 kDa on SDS-PAGE and a neutral pI. Removal of N-linked sugars by N-glycanase reveals a core protein of 42 kDa. Treatment with enzymes that cleave O-linked sugars does not substantially alter the molecular size. The native 5T4 molecules are very resistant to proteolysis until the N-linked sugars are removed or the glycoprotein is denatured and reduced. Glycopeptides generated by these approaches will be suitable for amino acid sequencing.

Aggregation of dispersed human cytotrophoblastic cells: lessons relevant to the morphogenesis of the placenta

The syncytial trophoblast of the human placenta forms by the fusion of mononuclear cytotrophoblast cells. Cytotrophoblast cells only fuse with other trophoblastic cells, indicating a specificity to this interaction. To explore the cellular aggregation which precedes fusion, we examined the association of cytotrophoblast cells isolated from term placentae and JEG-3 choriocarcinoma cells, a cytotrophoblast-like cell line, in suspension culture. Cytotrophoblast cells were isolated by dispersion of chorionic villi in trypsin-DNase in Ca2+/Mg2(+)-free medium. JEG-3 cells were released from culture flasks by trypsinization in Versene-EDTA buffer. In suspension culture, each cell type aggregated forming tissue-like masses over a 24-hr period. Transmission electron microscope analysis demonstrated the formation of numerous desmosomes between the aggregated cells. In outgrowth culture, the aggregates created in suspension were maintained as microvilli-covered multicellular structures with hollow cores. The extent of aggregation was dependent upon the concentration of cells in the incubations with greater aggregation occurring with higher cell densities. Aggregation of both cytotrophoblast cells and JEG-3 cells progressed rapidly during the initial 10 hr of incubation and then continued at a slower rate. Aggregation took place in serum-containing and serum-free medium, but was impeded in Ca2+/Mg2(+)-free medium. Incubation of JEG-3 and cytotrophoblast cells in the presence of the protein synthesis inhibitor, cycloheximide, prevented aggregation, whereas the inhibitor of N-linked glycosylation, tunicamycin, did not. The inhibitor of RNA synthesis, actinomycin D, had no effect on the aggregation of the cells during the initial 6 hr of aggregation. These findings suggest that trypsin treatment in Ca2+/Mg2(+)-poor medium removed a protein(s) from the trophoblast cell surface which must be resynthesized for cell-cell association to take place.

Gene imprinting and major histocompatibility complex class I antigen expression in the rat placenta

Ultrastructural immunocytochemical studies of the expression of major histocompatibility complex class I antigens in the placentas of inbred rats were performed using placentas derived from natural matings and from embryo transfers into females made pseudopregnant by mechanical stimulation. The studies utilized the WF (u) and DA (a) strains and monoclonal antibodies to all of the class I antigens involved. All four mating combinations of the two strains showed that only paternal antigens were expressed in the placenta and that they were limited to the basal trophoblast. This conclusion was confirmed using embryo transfer experiments. In allogeneic natural matings, the allele-specific class I transplantation antigens were not expressed on the membrane of the basal trophoblast but they were expressed in embryo transfers involving embryos of the same genotype. In both types of pregnancies, the pregnancy-associated (Pa) antigen was present on the membrane of the basal trophoblast. The antibody response to DA X DA and to WF X DA embryos transferred into pseudopregnant WF females was against the allele-specific RT1.Aa antigen and the Pa antigen, whereas the antibody response to the heterozygous embryo in the natural WF (female) X DA (male) mating was against the Pa antigen only. These results are consistent with the hypothesis that the suppression of the expression of the allele-specific major histocompatibility complex class I antigens occurs shortly after fertilization and that it requires the uterine environment of a natural mating.

The phosphorylation of p68, a calcium-binding protein associated with the human syncytiotrophoblast submembranous cytoskeleton, is modulated by growth factors, activators of protein kinase C and cyclic AMP

The phosphorylation of the lipocortin-related protein, p68, found in Ca2+-dependent association with the submembranous cytoskeleton has been studied using isolated human placental syncytiotrophoblast plasma membrane vesicles. p68 undergoes rapid, cation-independent phosphorylation in unstimulated membrane vesicles which was inhibited, in a dose-dependent manner, by insulin, platelet-derived growth factor, macrophage colony stimulating factor, protein kinase C-activating phorbol esters and phosphatidylinositol-specific phospholipase C. Epidermal growth factor had no effect on overall p68 phosphorylation. Transferrin induced an increase in p68 phosphorylation. However, phosphotyrosine was detected in p68 after treatment with epidermal growth factor, macrophage colony stimulating factor or transferrin, whereas a reduction in p68 phosphorylation appeared to be restricted to serine. cAMP and both cholera and pertussis toxins inhibited p68 phosphorylation. Both toxins were synergistic with the effects of insulin and platelet-derived growth factor whilst being antagonistic to the effect of transferrin. Epidermal growth factor and both human and equine immunoglobulin G, all of which alone did not affect overall p68 phosphorylation, reduced cholera or pertussis toxin-induced inhibition of p68 phosphorylation. Several phosphatase inhibitors failed to prevent macrophage colony stimulating factor-induced reduction of p68 phosphorylation. These results indicate that (i) p68 is a potential substrate of receptor tyrosyl kinases, (ii) p68 is not phosphorylated by protein kinase C or cAMP-dependent kinase and (iii) p68 phosphorylation is inhibited by activation of multiple pathways including those employing diacylglycerol or cAMP as second messengers.

Differentiation of trophoblast of the baboon blastocyst

The structure of trophoblast of the baboon blastocyst undergoes a number of maturational changes from the early blastocyst to the late blastocyst stage. The striking expansion of the blastocyst that occurs during the preimplantation period is accompanied by the development of an extensive endocytic apparatus. Cationized ferritin labels coated depressions and vesicles near the apical cell surface, numerous uncoated tubules and larger apical vesicles, and multivesicular bodies within trophoblast cells. Basally and laterally the labeled components are primarily small uncoated vesicles and tubules. Small, discrete clusters of ferritin particles were seen within the basolateral compartment between trophoblast and its basal lamina and beneath trophoblast cells that do not have a basal lamina. the results indicate that ingested materials may be directed in two pathways, one involving breakdown within the lysosomal system and one involving transcytosis. The zona pellucida is a trilaminar structure consisting of a fibrillar outer layer that often contains spermatozoa, an intermediate zone, and an inner layer containing columns of dense zonal material. Loss of the zona occurs after expansion of the blastocyst and development of the endocytic organelles. During the late blastocyst stage, syncytial trophoblast differentiates at the margin of the polar trophoblast. Because blastocysts were flushed from the uterus, it could not be determined whether azonal blastocysts had been adherent to the uterine surface prior to collection.

[A comparative study of the main components of the nucleolus in different populations of rat trophoblast cells during differentiation. I. The nucleoli of the trophoblast cells in the labyrinth section of the placenta]

The nucleolus undergoes some steps of structural transformation during differentiation of the labyrinth trophoblast cells. Primarily (on day 13 of gestation) the nucleolar components become rather disjoined. The nucleolus is composed of a loose net of strands of granulofibrillar and dense fibrillar components bearing fibrillar centers (FCs). Strands are separated by large lacunae. This rare-occurring type of nucleoli is replaced on the next (14th) day by the nucleolonemal type and later--by the compact nucleolar type. FCs with dense fibrillar component strands become extended into the masses of granulofibrillar component. Such transformations of nucleolar structure seem to be an expression of a fast-proceeding differentiation of the labyrinth trophoblast cells.

[A comparative study of the main components of the nucleolus in different populations of rat trophoblast cells during differentiation. II. The nucleoli of the trophospongium cells, the glycogen cells and the secondary giant cells]

A comparative study was performed of the arrangement of different nucleolar components during differentiation of trophoblast cell populations in the junctional zone of placenta (glycogen cells and trophospongium) and in the secondary giant cells. Each cell type is characterized by specific interrelation of nucleolar components. Some glycogen cells show signs of segregation of nucleolar components: strands of nucleolar components with fibrillar centers (FCs) are displaced to the periphery of the nucleolus and contact with the perinucleolar chromatin. Large reticular nucleoli in trophospongium cells contain many FCs which are gathered into several "chains" by strands of dense fibrillar component. Such a "chain" has also been found in nucleoli of secondary giant cells, with greater number of FCs in each "chain". Relationship between the arrangement of nucleolar components and the level of cell differentiation is discussed.

[A quantitative study of Ag-positive nucleolar segments revealed by silver staining in the interphase nuclei of trophoblast cells from the rat placental connective zone]

A cytomorphological study was made of silver stained nucleoli in interphasic nuclei of trophoblast cells from the rat placenta connective zone, in addition to calculation of Ag-positive spherules in the nucleoli. The prevalent number of Ag-positive nucleolar spherules in the nuclei was 6, corresponding to the number of nucleolar organizers (NOR's) in the diploid chromosome complement of the rat. The mean number of Ag-positive spherules in the nucleoli progressively increase in the course of polyploidization from 2c to 32c; variability of the spherule number also increasing. The mean area of nucleoli is found to increase in proportion to the ploidy degree. A high correlation is found between the number of Ag-positive spherules and the area of nucleoli in the nucleus (r = 0.78). This appropriateness is exhibited at all the ploidy levels. The number of Ag-spherules and the area of nucleoli are found to depend slightly on the number of nucleoli. The possibility to use the number of Ag-positive spherules as a criterion of the activity of the NOR in interphasic nuclei is discussed.

Trophoblast differentiation during the transition from trophoblastic plate to lacunar stage of implantation in the rhesus monkey and human

The transition from the trophoblastic plate stage to the early lacunar stage was examined in a series of implantation sites from the rhesus monkey, timed on the basis of the preovulatory estrogen peak, and prepared for transmission electron microscopy. This transition was compared with specimens from stage 5a, b, and c in the Carnegie collection of human embryos. The transition was marked by the differentiation of a new type of syncytial trophoblast--namely, a unilaminar microvillous polarized syncytium, which developed throughout the trophoblastic plate, forming characteristic intrasyncytial clefts. The rapid development of this type of syncytium created a nonclotting chamber for maternal blood wherever trophoblast intrusion into maternal vessels created confluence. Although the nature of the material in the Carnegie series precluded cytological characterization of the trophoblast, there is evidence that a similar transition occurs in human trophoblast and that in the human also the appearance of lacunae marks a change from an early invasive trophoblast to a situation in which growth is more significant.

Identification and characterization of monolayer cultures of sheep trophoblast cells maintained in bicameral culture chambers

Enriched epithelial cell and fibroblast fractions were isolated from ovine placentomes by isopycnic centrifugation of collagenase/DNAse-dispersed cells through a density gradient of 45% Percoll. The epithelial cells formed confluent monolayers when plated onto filters impregnated with a 50-microns layer of Matrigel in medium containing 10% fetal bovine serum. These cells were maintained in dual environment culture chambers in serum-free medium for at least 12 days. The epithelium had a polarized appearance similar to that found in vivo only when cells were plated at high density (10(7)/cells/cm2). The epithelial monolayer consisted predominantly of a single population of uninucleate cells with intracellular features similar to those previously described for ovine trophoblast both in vivo and in vitro. These cells stained positively with an antiserum to alpha-keratin, a marker specific to epithelial cells, and no staining was observed with antisera raised against binucleate cells or leucocyte-common antigen. Binucleate cells were detected by microscopy and immunostaining in the pellet of cells obtained from the Percoll gradient but were rarely seen in the epithelium. The epithelial monolayer excluded 3H-inulin, added to the basal chamber, from the apical chamber, thus demonstrating the formation of a permeability barrier similar to that found in vivo. The maintenance of a monolayer of pure ovine trophoblast cells in vitro, which retain the characteristics of the epithelium in vivo, will enable the study of many cellular functions of the trophoblast.

Vacuolated cytotrophoblast: a subpopulation of trophoblast in the chorion laeve

In summary, immunocytochemical analysis of the placenta and fetal membranes discloses two subpopulations of trophoblastic cells in the chorion laeve with distinct morphologic and immunocytochemical features. Both subpopulations are composed of mononucleate cells but one contains clear vacuolated cytoplasm whereas the other contains non-vacuolated eosinophilic cytoplasm. The vacuolated cells are placental alkaline phosphatase (PLAP) positive and human placental lactogen (hPL) negative, whereas the eosinophilic cells are PLAP negative and hPL positive. Both cell types contained immunoreactive keratin and epithelial membrane antigen, but are negative for human chorionic gonadotropin(beta), pregnancy specific beta I-glycoprotein, and prolactin. Electron microscopic studies of the vacuolated cells show that these cells contain numerous lucent non-membrane bound lipid droplets and pinocytotic vesicles. In addition they contain numerous intracellular filaments and desmosomes corresponding to the immuno-cytochemical localization of keratin. Their precise function is not clear, but the abundance of PLAP, an enzyme associated with absorption, suggests that these cells may be involved with maternal fetal transport. The vacuolated cells appear to be limited to the chorion. Their characteristic morphologic and immunocytochemical features and unique anatomic distribution suggests that they represent a distinctive subpopulation of trophoblastic cells for which we propose the term 'vacuolated cytotrophoblast'.

[Hypertension and syncytiotrophoblast: morpho-structural aspects]

Hypertension is a pathological condition that involves maternal fetal relationship. In hypertension placenta displays a syncytiotrophoblast plasmalemma with aspects of anomalous behaviour concerning Intramembranous Particles (IMP) and actin content of microvilli cytoskeleton. Decrease of syncytiotrophoblast microvilli IMP and microvilli actin further sustain the tendency of hypertensive placenta to show some features of immaturity that might deeply influence fetal-maternal exchanges during pregnancy associated with pathological status.

Early human trophoblast cell cultures. A morphological and immunocytochemical study

Rapidly growing cytotrophoblasts were isolated from early human chorionic villi and the Papanicolaou method was used to characterize their cytology and transformation into syncytiotrophoblasts. Cytotrophoblasts fused and formed binucleated cells or mononucleated intermediate cells. Syncytial cells were formed by fusion of small cytotrophoblasts or intermediate cells and cytotrophoblasts. Glycosaminoglycans were produced in cytotrophoblasts and released extracellularly. Here they were accumulated and/or diffused into a continuous layer covering the cells. Glycosaminoglycans in syncytial cells were contained in well defined membranous sacs. Cytotrophoblasts only grown beyond confluence differentiated into villi with a villus-like histology.

Trophoblast invasion during implantation of the mouse embryo

The interaction between trophoblastic and maternal cells was analysed by electron microscopy on days 6, 7 and 8 of pregnancy, in the mouse. Special emphasis was given to phagocytic activity and invasiveness by the trophoblast. On the sixth day of pregnancy, the trophoblast cells are in contact with the epithelial cells of the implantation crypt, with the basal lamina of the crypt, and with cells of the antimesometrial decidua. On the seventh and eighth days of pregnancy, the trophoblastic cells interact with those of the antimesometrial decidua. The giant trophoblastic cells engulf epithelial cells, maternal blood cells and decidual cells although the pattern of phagocytosis of these structures differs. Both whole epithelial cells and blood cells were ingested. The epithelial cells were deteriorated whereas the blood cells had a normal morphology; the decidual cells were ingested following a severe process of deterioration. Processes of trophoblastic cells interposed between the epithelium of the implantation crypt and its basal lamina seem to contribute to the displacement of the epithelial cells. The invasion of the endometrium by the trophoblast begins with the penetration by processes of trophoblastic cells between the decidual cells. The contact between the surface of both cell types may be very close: adherens type junctions and focal contacts are formed between trophoblastic cells and healthy decidual cells. Trophoblastic cells ingest deteriorated or fragmented cells and gradually occupy the spaces left by the latter.

A comparative study of attachment of human, bovine and mouse blastocysts to uterine epithelial monolayer

The in-vitro attachment of human, bovine and murine blastocysts to monolayer cultures of uterine epithelium were studied by transmission electron microscopy. The human trophoblastic cells intrude between uterine epithelial cells forming a multilayer during attachment in vitro, thus resembling the intrusive type of penetration observed in vivo. The bovine trophoblastic outgrowth resembled an epitheliochorial attachment as the trophoblast formed an attachment plate on top of the endometrial cells without penetration. In the murine attachment study, the trophoblast cells immediately displaced the uterine cells and formed contact with the culture vessel.

Morphological demonstration of the failure of Mus caroli trophoblast in the Mus musculus uterus

A histological study of Mus caroli embryos gestating in the Mus musculus uterus was undertaken at Day 8.5 of gestation, 1 day after such embryos are reported to be normal and 1 day before the earliest events associated with death of the xenogeneic embryos. In comparison to control M. caroli embryos recovered from M. caroli and to control M. musculus embryos recovered from M. musculus, the xenogeneically transferred embryos showed intrauterine growth retardation that was associated with trophoblastic insufficiency. Trophoblast cell degeneration was observed, in the absence of lymphocytic infiltration. Therefore, loss of trophoblast cell function rather than lymphocyte-mediated destruction of trophoblast appears to underlie the death of M. caroli embryos in the M. musculus uterus.

O-glycosylation of the alpha-subunit does not limit the assembly of chorionic gonadotropin alpha beta dimer in human malignant and nonmalignant trophoblast cells

Biosynthetic experiments were carried out in cultures of human malignant trophoblast cells (the JAR cell line) and in explants of normal first trimester human placental tissue to test the hypothesis that the O-glycosylation of the glycoprotein hormone alpha-subunit at Thr-39 regulates the assembly of the CG alpha beta dimer. This modification of alpha has been shown to ablate its ability to combine in vitro with the beta-subunit of bovine LH and might explain why JAR cells and placental explants secrete uncombined alpha- and beta-subunits in addition to the hCG alpha beta dimer. We have previously detected an O-linked carbohydrate chain at Thr-39 in preparations of secreted free alpha-subunit, but not dimer CG alpha from JAR culture medium. We report here evidence that the O-glycosylation of alpha does not regulate the biosynthetic assembly of the hCG dimer in cultures of JAR choriocarcinoma cells or first trimester placental explants. The intracellular precursor forms of alpha and beta that accumulate in the endoplasmic reticulum and combine in that compartment are not yet modified with O-linked carbohydrate, as determined by measurements of their [3H]galactosamine content after biosynthetic labeling of amino sugars with [3H]glucosamine. Furthermore, only half of the free alpha-subunit secreted by JAR cells and less than 10% of free alpha secreted by 10-week-old placental explants received the O-linked chain. This was shown by determining the ratio of the unglycosylated and glycosylated forms of the tryptic peptide from free alpha that contains the O-glycosylation site (residues 36-42). Based on these findings, we make the following conclusions. 1) O-Glycosylation of alpha-subunit is a late event in the secretory pathway of trophoblasts compared to the rapid combination in the rough endoplasmic reticulum of hCG subunit precursors to form alpha beta dimer. 2) Association of alpha with beta precludes the subsequent addition of the glycan to alpha at Thr-39. 3) The alpha molecules that fail to combine with beta in the endoplasmic reticulum are substrates for the later addition of O-linked carbohydrate, presumably in the Golgi complex, but only a fraction of the free alpha molecules are modified with O-linked carbohydrate.

Characterization of pure human first-trimester cytotrophoblast cells in long-term culture: growth pattern, markers, and hormone production

Pure long-term cytotrophoblast cultures were established from human first-trimester placentas by growing chorionic villus explants without enzymatic digestion. Cytoplasmic human chorionic gonadotropin was detectable in all (100%) cells in culture when labeled with a polyclonal anti-human chorionic gonadotropin antibody and in 71% to 83% of cells labeled with a monoclonal anti-alpha-human chorionic gonadotropin antibody. Most of the cells expressed cytokeratin and surface Trop-1 and Trop-2 antigens (89% to 95%), but none expressed cytoplasmic vimentin or surface 63D3 antigens. Study of the ultrastructure of the cells demonstrated epithelial morphologic features. The average doubling time of the trophoblast was 48 to 96 hours. Some of the lines have been continuously propagated for 8 months. They produced variable amounts of human chorionic gonadotropin (50 to 710 mIU/ml per 10(5) cells per 24 hours). The basal level of progesterone secreted by trophoblast (444.4 +/- 32.4 pg/ml per 10(5) cells per 24 hours) doubled in the presence of pure human chorionic gonadotropin (100 ng/ml). They produced small amounts of 17 beta-estradiol (less than 20 pg/ml per 10(5) cells per 24 hours); human chorionic gonadotropin had no effect on the estradiol production. Trophoblast-derived human chorionic gonadotropin acted as a growth factor because trophoblast proliferation (measured by uptake of thymidine labeled with tritium) was reduced by 60% in the presence of an anti-human chorionic gonadotropin antibody. Availability of pure, functionally competent human cytotrophoblast in long-term cultures is relevant for further studies in reproduction biology.

Thromboxane and prostacyclin production by different compartments of the human placental villus

We separated the trophoblast and villous core of human placental villi to compare thromboxane (Tx) and prostacyclin production in these two compartments with eicosanoid production by intact villi. TxB2 and 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha), the stable metabolites of TxA2 and prostacyclin, respectively, were measured in serum-free media from 48-h incubations of intact villi, villous core tissue denuded of its trophoblast layer, and trophoblast cells. In villi, the medium TxB2 concentrations increased rapidly to a peak level of 20 +/- 9 (+/- SE) (n = 11) pg/microgram protein at 48 h; 6-keto-PGF1 alpha was first detected in medium at 20 h, and it increased to 19.6 +/- 4.0 pg/micrograms protein (n = 11) by 48 h. Compared to villi, villous core tissue denuded of its surface trophoblast layer had a 7-fold greater TxB2 level (136 +/- 17 pg/micrograms protein; n = 11) by 48 h, but a comparable level of 6-keto-PGF1 alpha (22.5 +/- 3.7 pg/micrograms protein). Trophoblast cultures produced predominantly TxB2 (109 +/- 18 pg/micrograms protein; n = 11) and had the lowest 6-keto-PGF1 alpha production among the three groups (11.4 +/- 2.6 pg/micrograms protein). At 48 h, the mean TxB2/6-keto-PGF1 alpha ratio was 1.0 in medium from intact villi, 6.2 in medium from villous core tissue, and 13.3 in medium from trophoblast cells. Indomethacin inhibited production of both eicosanoids in all cultures. Our studies indicate that intact placental villi produce equal amounts of Tx and prostacyclin, the trophoblast compartment produces predominantly Tx, and the villous core compartment produces an increased amount of Tx when denuded of its trophoblast layer. These data also suggest that the trophoblast produces an inhibitor or provides a catabolic function that limits villous core Tx production.

Enzymatic isolation of human trophoblast and culture on various substrates: comparison of first trimester with term trophoblast

A simple method is described for the isolation of trophoblast cells from both first trimester and term placenta. Trophoblast preparations were characterized by light microscopy, scanning and transmission election miscroscopy and immunohistochemistry to distinguish these cells from mesenchyme and endothelium. Trophoblast cells were cultured on various substrates and a comparison made of their ability to attach, proliferate and function. A collagen gel substrate produced by repolymerization of an acid soluble collagen fraction from chorionic villi allowed rapid attachment of trophoblast cells and maintainance of their original morphology. Term trophoblast cells were shown to become fully functional in short term (three day) cultures by virtue of their increased immunocytochemical staining for the presence of beta hCG, hPL and SPI. beta hCG increased significantly by day three thus demonstrating functional activation. Trophoblast cells from first trimester placenta formed proliferating colonies of hormone producing cells while those from term placenta reaggregated into clusters and closely resembled syncytiotrophoblast both morphologically and functionally. This short term culture system for term trophoblast will allow further studies into the biology of trophoblast polypeptide hormone synthesis and secretion.

Ultrastructural changes and immunocytochemical analysis of human placental trophoblast during short-term culture

Trophoblastic cells, of at least 95 per cent purity by immunofluorescence and morphological criteria, were obtained from human term placenta by a simple trypsinisation method without the additional purification steps or complex culture conditions used by others. The differentiation of these cells was followed over four days in culture by fluorescence immunocytochemistry, by scanning and transmission electron microscopy and by light microscopy. The results support the idea that the isolated cells are cytotrophoblast and that these differentiate during this time into cells with characteristics of villous syncytiotrophoblast. This process involved first the formation of a multicellular layer of mononucleated cells, then the development of a syncytium of multinucleated cells and, not necessarily concurrently, functional differentiation. This may be a useful model for the study of syncytiotrophoblast function.

Hydatidiform mole: an ultrastructural analysis of syncytiotrophoblast surface organization

The scanning ultrastructural examination of a series of 31 hydatidiform mole and 12 healthy placental specimens of similar gestational age has revealed a variety of surface architectures more common in molar tissue. Characteristic paddle-shaped sprouts, ridging of the syncytial maternal oriented surface and microgibbosities are described. These structures are explicable in terms of organellar hyperplasia of cortical cytoskeletal elements found in healthy tissue. Specific morphological evidence of involvement of these elements in a condition where aberrant growth control leads to the characteristic trophoblastic hyperplasia is a further indication that cytoskeletal elements may mediate transformation. An increase in resolution obtained over previous scanning electron microscope studies has allowed the description of detailed features such as 'caveolar collars' on the maternal oriented healthy and molar trophoblast surfaces. These observations are of relevance to understanding the mechanisms of several cell physiological processes, including transepithelial transport. New observations of a reticular organization in the surface layer of molar trophoblast indicate that a syncytioskeletal layer, with organization resembling that previously described in healthy chorionic villi, is also present in molar villi.

Induction of class I major histocompatibility complex antigen expression by West Nile virus on gamma interferon-refractory early murine trophoblast cells

Primary murine trophoblast giant cells (TGC) do not express detectable major histocompatibility complex (MHC) antigens and are refractory to the MHC-increasing effects of alpha and beta (virus-induced) interferons and gamma (immune type) interferon during early implantation (postcoital days 3.5-6). West Nile virus infection of primary TGC monolayers from postcoital-day-3.5 preimplantation blastocysts induced paternal MHC antigen expression within 16 hr, as detected by immunogold labeling for electron microscopy. Induction is unlikely to have been mediated by secreted virus-induced interferons or other factors, as it occurred in the presence of high concentrations of anti-alpha/beta interferon antibodies and was not induced by virus-inactivated supernatants from MHC-induced primary TGC cultures. Attempts to induce MHC antigen expression with poly(I.C) or recombinant tumor necrosis factor alpha in primary TGC cultures also failed. Thus, the apparent inhibition of MHC antigen expression in primary TGC during early implantation and their refractoriness to induction of de novo MHC antigen expression is not absolute. This may represent a maternal-and/or species-protective evolutionary device. As such, manipulation of this phenomenon may allow a conclusive assessment of the significance of inhibition of MHC antigen expression on trophoblast cells in the implanting semiallogeneic embryo.